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Grenoble

Grenoble (, ; Grenoblo or Grainóvol; Graçanòbol) is the prefecture and largest city of the Isère department in the Auvergne-Rhône-Alpes region of southeastern France. It was the capital of the Dauphiné historical province and lies where the river Drac flows into the Isère at the foot of the French Alps.

The population of the commune of Grenoble was 158,198 as of 2019, while the population of the Grenoble metropolitan area (French: aire d'attraction de Grenoble or agglomération grenobloise) was 714,799 which makes it the largest metropolis in the Alps, ahead of Innsbruck and Bolzano. A significant European scientific centre, the city advertises itself as the "Capital of the Alps", due to its size and its proximity to the mountains. The many suburban communes that make up the rest of the metropolitan area include four with populations exceeding 20,000: Saint-Martin-d'Hères, Échirolles, Fontaine and Voiron.

Grenoble's history goes back over 2,000 years, to a time when it was a village of the Allobroges Gallic tribe. It became the capital of the Dauphiné in the 11th century. This status, consolidated by the annexation to France, allowed it to develop its economy. Grenoble then became a parliamentary and military city, close to the border with Savoy, which at the time was part of the Holy Roman Empire. Industrial development increased the prominence of Grenoble through several periods of economic expansion over the last three centuries. This started with a booming glove industry in the 18th and 19th centuries, continued with the development of a strong hydropower industry in the late 19th to early 20th centuries, and ended with a post-World War II economic boom symbolized by the holding of the X Olympic Winter Games in 1968.

The city has grown to be one of Europe's most important research, technology and innovation centres, with one in five inhabitants working directly in these fields. Grenoble is classified as a global city with the ranking of "sufficiency" by the Globalization and World Cities Research Network. The city held the title of European Green Capital in 2022.

Antiquity
The first references to what is now Grenoble date back to 43 BC. Cularo was at that time a Gallic village of the Allobroges tribe, near a bridge across the Isère. Three centuries later and with insecurity rising in the late Roman empire, a strong wall was built around the small town in 286 AD.

The Emperor Gratian visited Cularo and, touched by the people's welcome, made the village a Roman city. In honour of this, Cularo was renamed Gratianopolis ("city of Gratian") in 381 (leading to Graignovol during the Middle Ages, and then Grenoble).

Christianity spread to the region during the 4th century, and the diocese of Grenoble was founded in 377 AD. From that time on, the bishops exercised significant political power over the city. Until the French Revolution, they styled themselves the "bishops and princes of Grenoble".

Middle Ages
After the collapse of the Roman Empire, the city became part of the first Burgundian kingdom in the 5th century and of the later Kingdom of Burgundy until 1032, when it was integrated into the Holy Roman Empire. The Burgundian rule was interrupted between 942 and 970 by Arab rule based in Fraxinet.

Grenoble grew significantly in the 11th century when the Counts of Albon chose the city as the capital of their territories. Their possessions at the time were a patchwork of several territories sprawled across the region, and the central position of Grenoble allowed the Counts to strengthen their authority. When they later adopted the title of "Dauphins", Grenoble became the capital of the State of Dauphiné.

Despite their status, the Counts had to share authority over the city with the Bishop of Grenoble. One of the most famous of those was Saint Hugh. Under his rule, the city's bridge was rebuilt, and a regular and leper hospital was built.

The inhabitants of Grenoble took advantage of the conflicts between the Counts and the bishops and obtained the recognition of a Charter of Customs that guaranteed their rights. That charter was confirmed by Kings Louis XI in 1447 and Francis I in 1541.

In 1336 the last Dauphin Humbert II founded a court of justice, the, which settled at Grenoble in 1340. He also established the University of Grenoble in 1339. Without an heir and deep into debt, Humbert sold his state to France in 1349, on the condition that the heir to the French crown used the title of Dauphin. The first one, the future Charles V, spent nine months in Grenoble. The city remained the capital of the Dauphiné, henceforth a province of France, and the Estates of Dauphiné were created.

The only Dauphin who governed his province was the future Louis XI, whose "reign" lasted from 1447 to 1456. It was only under his rule that Dauphiné properly joined the Kingdom of France. The Old Conseil Delphinal became a Parlement (the third in France after the Parliaments of Paris and Toulouse), strengthening the status of Grenoble as a Provincial capital. He also ordered the construction of the Palais du Parlement (finished under Francis I) and ensured that the Bishop pledged allegiance, thus unifying the political control of the city.

At that time, Grenoble was a crossroads between Vienne, Geneva, Italy, and Savoy. It was the industrial centre of the Dauphiné and the province's biggest city, but a rather small one.

Renaissance
Owing to Grenoble's geographical situation, French troops were garrisoned in the city and its region during the Italian Wars. Charles VIII, Louis XII, and Francis I went several times to Grenoble. Its people consequently had to suffer from the exactions of the soldiers.

The nobility of the region took part in various battles (Marignano, Pavia) and in doing so gained significant prestige. The best-known of its members was Bayard, "the knight without fear and beyond reproach".

Grenoble suffered as a result of the French Wars of Religion. The Dauphiné was indeed an important settlement for Protestants and therefore experienced several conflicts. The baron des Adrets, the leader of the Huguenots, pillaged the Cathedral of Grenoble and destroyed the tombs of the former Dauphins.

In August 1575, Lesdiguières became the new leader of the Protestants and, thanks to the accession of Henry IV to the throne of France, allied himself with the governor and the lieutenant general of the Dauphiné. But this alliance did not bring an end to the conflicts. Indeed, a Catholic movement, the Ligue, which took Grenoble in December 1590, refused to make peace. After months of assaults, Lesdiguières defeated the Ligue and took back Grenoble. He became the leader of the entire province.

Lesdiguières became the lieutenant-general of the Dauphiné and administered the Province from 1591 to 1626. He began the construction of the Bastille to protect the city and ordered the construction of new walls, increasing the city's size. He also constructed the Hôtel Lesdiguières, built new fountains, and dug sewers.

In 1689, the bishop Étienne Le Camus launched the construction of Saint-Louis Church.

From Louis XIV to the French Revolution

The revocation of the Edict of Nantes by Louis XIV caused the departure of 2,000 Protestants from Grenoble, weakening the city's economy. However, it also weakened the competing glove industry of Grasse, leaving the glove factories of Grenoble without any competition. This allowed a stronger economic development for the city during the 18th century. At the beginning of that century, only 12 glovers made 15,000 dozen gloves each year; by 1787, 64 glovers made 160,000 dozen gloves each year.

The city gained some notoriety on 7 June 1788 when the townspeople assaulted troops of Louis XVI in the "Day of the Tiles". The people attacked the royal troops to prevent an expulsion of the notables of the city, which would have seriously endangered the economic prosperity of Grenoble. Following these events, the Assembly of Vizille took place. Its members organized the meeting of the old Estates General, thus beginning the French Revolution. During the Revolution, Grenoble was represented in Paris by two illustrious notables, Jean Joseph Mounier and Antoine Barnave.

In 1790, the Dauphiné was divided into three departments, and Grenoble became the chef-lieu of the Isère department. Only two refractory priests were executed at Grenoble during the Reign of Terror. Pope Pius VI, prisoner of France, spent two days at Grenoble in 1799 before going to Valence where he died.

19th century

The establishment of the Empire was overwhelmingly approved (in Isère, the results showed 82,084 yes and only 12 no). Grenoble welcomed for the second time a prisoner Pope in 1809. Pius VII spent 10 days in the city en route to his exile in Fontainebleau.

In 1813 Grenoble was under threat from the Austrian army, which invaded Switzerland and Savoy. The well-defended city contained the Austrian attacks, and the French army defeated the Austrians, forcing them to withdraw at Geneva. However, the later invasion of France in 1814 resulted in the capitulation of the troops and the occupation of the city.

During his return from the island of Elba in 1815, Napoleon took a road that led him near Grenoble at Laffrey. There he met the Royalist Régiment d'Angoulême (former 5th) of Louis XVIII's Royal Army. Napoleon stepped toward the soldiers and said these famous words: "If there is among you a soldier who wants to kill his Emperor, here I am." The soldiers all joined his cause. After that, Napoleon was acclaimed at Grenoble and General Jean Gabriel Marchand could not prevent Napoleon from entering the city through the Bonne gate. He said later: "From Cannes to Grenoble, I still was an adventurer; in that last city, I came back a sovereign". But after the defeat of Waterloo, the region suffered from a new invasion of Austrian and Sardinian troops.

The 19th century saw significant industrial development of Grenoble. The glove factories reached their Golden Age, and their products were exported to the United States, the United Kingdom, and Russia.

General Haxo transformed the Bastille fortress, which took on its present aspect between 1824 and 1848. The Second Empire saw the construction of the French railway network, and the first trains arrived at Grenoble in 1858. Shortly thereafter Grenoble experienced widespread destruction by extensive flooding in 1859.

In 1869 engineer Aristide Bergès played a major role in industrializing hydroelectricity production. With the development of his paper mills, he accelerated the economic development of the Grésivaudan valley and Grenoble.

On 4 August 1897, a stone and bronze fountain was inaugurated in Grenoble to commemorate the pre-revolutionary events of June 1788. Built by the sculptor Henri Ding, the Fountain of the Three Orders, which represents three characters, is located on Place Notre-Dame. People in Grenoble interpret these characters as follows: "Is it raining?" inquires the third estate; "Please heaven it had rained", lament the clergy; and "It will rain", proclaims the nobility.

20th century
World War I accelerated Grenoble's economic development. To sustain the war effort, new hydroelectric industries developed along the various rivers of the region, and several existing companies moved into the armaments industry (for example in Livet-et-Gavet). Electrochemical factories were also established in the area surrounding Grenoble, initially to produce chemical weapons. This development resulted in significant immigration to Grenoble, particularly from Italian workers who settled in the Saint-Laurent neighborhood.

The economic development of the city was highlighted by the organization of the International Exhibition of Hydropower and Tourism in 1925, which was visited by more than 1 million people. The organization of this exhibition forced the military to remove the old city walls and allowed the expansion of the city to the south. This exhibition also highlighted the city's hydropower industry and the region's tourist attractions.

The site of the exhibition became an urban park in 1926, named Parc Paul Mistral after the death of the mayor in 1932. The only building of this exhibition remaining in the park is the crumbling Tour Perret, which has been closed to the public since 1960 due to its very poor state of maintenance.

World War II
During World War II, at the Battle of the Alps, the fascist Italian invasion was stopped near Grenoble at Voreppe by the forces of General Cartier in June 1940. The French forces resisted until the armistice, after which Grenoble was part of the French State before an Italian occupation from 1942 to 1943. The relative tolerance of the Italian occupiers towards the Jewish populations resulted in a significant number moving to the region from the German-occupied parts of France.

Grenoble was extremely active in the Résistance against the occupation. Its action was symbolized by figures such as Eugène Chavant, Léon Martin, and Marie Reynoard. The University of Grenoble supported the clandestine operations and provided false documentation for young people to prevent them from being assigned to STO.

In September 1943, German troops occupied Grenoble, escalating the conflict with the clandestine movements. On 11 November 1943 (the anniversary of the armistice of 1918), massive strikes and demonstrations took place in front of the local collaboration offices. In response, the occupiers arrested 400 demonstrators in the streets. On 13 November, the resistance blew up the artillery at the Polygon, which was a psychological shock for an enemy who then intensified the repression. On 25 November, the occupiers killed 11 members of the Résistance organizations of Grenoble. This violent crackdown was nicknamed "Grenoble's Saint-Bartholomew". From these events, Grenoble was styled by the Free French Forces the title of Capital of the Maquis on the antennas of the BBC.

This event only intensified the activities of Grenoble's resistance movements. The Germans could not prevent the destruction of their new arsenal on 2 December at the Bonne Barracks. After the Normandy landing, resistance operations reached their peak, with numerous attacks considerably hampering the activity of German troops. With the landing in Provence, German troops evacuated the city on 22 August 1944. On 5 November 1944, General Charles de Gaulle came to Grenoble and bestowed on the city the Compagnon de la Libération to recognise "a heroic city at the peak of the French resistance and combat for the liberation".

Post-war
In 1955, future physics Nobel prize laureate Louis Néel created the Grenoble Center for Nuclear Studies (CENG), resulting in the birth of the Grenoble model, a combination of research and industry. The first stone was laid in December 1956.

In 1968 Grenoble hosted the X Olympic Winter Games. This event helped modernize the city with the development of infrastructure such as an airport, motorways, a new town hall, and a new train station. It also helped the development of ski resorts like Chamrousse, Les Deux Alpes, and Villard-de-Lans.

Geography

Grenoble is surrounded by mountains. To the north lies the Chartreuse, to the south and west the Vercors, and to the east the Belledonne range. Grenoble is regarded as the capital of the French Alps. It is the centre of the Grenoble urban unit (agglomeration).

Except for a few dozen houses on the slopes of the Bastille hill of Chartreuse, Grenoble is exclusively built on the alluvial plain of the rivers Isère and Drac at an altitude of 214 m. As a result, the city itself is extremely flat. Mountain sports are an important tourist attraction in summer and winter. Twenty large and small ski resorts surround the city, the nearest being Le Sappey-en-Chartreuse, which is about 15 minutes away by car.

Historically, Grenoble and the surrounding areas were heavy industry and mining sites. Abandoned mills and factories can be found in small towns and villages, and a few have been converted to tourist attractions, such as the coal mine at La Mure.

Climate
The climate in Grenoble depends on the data from the chosen weather station. Grenoble Airport, located $40 km$ northwest of the city has a range from temperate continental climate to oceanic climate (Köppen: Cfb, Trewartha: Dc, Do) depending on the chosen classifications. The area contains significant seasonal differences between warm to hot summers and cool to cold winters. Both temperatures above 30 C for the summer months and winter air frosts are common.

In addition, the climate is much gloomier than in the Mediterranean region, although less so than in Northern France. Rainfall is quite heavy by French standards, although the number of rainy days is relatively moderate.

As a result of winter lows averaging below freezing, snowfall also occurs, although the Grenoble Airport area itself is too mild to sustain a snowpack all winter, unlike the surrounding mountains. The record low of -27.1 C decisively indicates the continental influence, being colder than records in typical maritime climates. Winter nights are also colder than in all other French lowland areas.

The Grenoble metropolitan area experiences two different microclimates: one more windy and cold to the west, the other, on the contrary, not very windy and warmer to the east.

However, the city of Grenoble features a humid subtropical climate (Köppen: Cfa) with no dry season. Although the record is incomplete, the newer station will meet the humid subtropical classification if maintained for the required 30-year period.

Saint-Martin-d'Hères weather station
(5 km east of Grenoble at an altitude of 220m)

Alpes-Isère Airport weather station
(40 km north-west of Grenoble at an altitude of 400m)

Urbanism and architecture
The Bouchayer-Viallet site is a powerful symbol of Grenoble's industrial past. This former factory is now converted into a dual-purpose area more closely linked to the Berriat neighbourhood. Innovative business activities as Apple Inc. co-exist with housing, sporting facilities, contemporary music venue and arts centres as Le Magasin. At the entrance to the Bouchayer-Viallet site, Square des Fusillés has been redeveloped and extended taking over an old car park, to facilitate access from the tramway stop and Cours Berriat.

Redevelopment of the former De Bonne barracks was an important step in the drive to launch sustainable housing in France. In 2009, the site of De Bonne was distinguished as the best eco-neighborhood in France. A shopping mall contains 53 shops arranged around an inner concourse, with one side opening onto the park and the other connecting to the town.

La Bastille
The Bastille, an ancient series of fortifications on the mountainside, overlooks Grenoble on the northern side and is visible from many points in the city. The Bastille is one of Grenoble's most visited tourist attractions and provides a good vantage point over both the town below and the surrounding mountains.

The Bastille fort was begun in the Middle Ages, and later centuries saw extensive additions, including a semi-underground defense network. The Bastille has been credited as the most extensive example of early 18th-century fortifications in all of France. It then held an important strategic point on the French Alpine frontier with the Kingdom of Sardinia.

The first cable transport system, installed on the Bastille in 1875, was built by the Porte de France Cement Company for freight. This cable transport system connected a quarry on Mount Jalla, just over the Bastille, and Grenoble. It was abandoned in the early 20th century.

Since 1934, the Bastille has been the destination of the "Grenoble-Bastille cable car". This system of mostly transparent egg-shaped cable cars known to locals as "Les Bulles" (the bubbles) provides the occupants with an excellent view over the Isère. At the top are two restaurants and installed in the casemates of the fort itself since June 2006, the Bastille Art Centre allows visitors to see contemporary art exhibitions. There is also a small military museum on mountain troops (Musée des troupes de montagne) and, since 2000, a memorial to the mountain troops (Mémorial national des troupes de montagne) further along the road, on top of the hill.

Palace of the Parliament of Dauphiné
This renaissance palace was constructed at the Place Saint André around 1500 and extended in 1539. It was the location of the Parlement of Dauphiné until the French Revolution. It then became the Grenoble courthouse, until the courts were moved to a modern building in 2002. The left wing of the palace was extended in 1897. The front of the former seat of the nearby Dauphiné Parlement combines elements from a gothic chapel and a Renaissance façade.

The building now belongs to the Isère Council (Conseil Général de l'Isère). An ongoing renovation project will give this building a new life whilst preserving its patrimonial character and adding a modern touch.

Museum of Grenoble
The city's most prized museum, the Museum of Grenoble (Musée de Grenoble), welcomes 200,000 visitors a year. It is primarily renowned for its extensive paintings collection, which covers Western paintings from the Middle Ages to the 21st century. In the early 20th century, the Museum of Grenoble became the first French museum to open its collections to modern art, and its collection of modern and contemporary art has grown to become one of the largest in Europe. The painting holdings include works by painters such as Veronese, Rubens, Zurbarán, Ingres, Delacroix, Renoir, Gauguin, Signac, Monet, Matisse, Picasso, Kandinsky, Joan Miró, Paul Klee, Giorgio de Chirico and Andy Warhol. The museum also presents a few Egyptian antiquities as well as Greek and Roman artifacts. The Sculpture collection features works by Auguste Rodin, Matisse, Alberto Giacometti and Alexander Calder. In April 2010, the prophetess of Antinoe, a 6th-century mummy discovered in 1907 in the Coptic necropolis of Antinoe in Middle Egypt, returned to the Museum of Grenoble, after more than fifty years of absence and extensive restoration.

Archaeological museums

Situated on the right bank of the Isère, on Place Saint-Laurent, the Grenoble Archaeological Museum presents the archaeological excavations done on its location. The vestiges date back to the 3rd century AD and provide a timeline of the history of Christianity in the region. The museum is situated below a 12th-century Benedictine church, under which Jacques Joseph Champollion-Figeac, brother of famed egyptologist Jean-François Champollion, discovered a 6th-century AD church in 1803. It was one of the first classified monuments in France thanks to the intervention of Prosper Mérimée, historic monument inspector. Systematic excavations were conducted from 1978 to 2011, as part of a regional research program on the evolution of churches during the Middle Ages. After eight years of work, the museum reopened on 6 May 2011.

The Musée de l'Ancien Évêché is the second archaeological museum in the city and is located near the Grenoble Cathedral. Installed in 1998, it houses the first baptistery of the city

The Grenoble townhall hosts a bust of Stendhal by sculptor Pierre Charles Lenoir.

Secondary level
The large community of both foreign students and foreign researchers prompted the creation of an international school. The Cité Scolaire Internationale Europole (CSI Europole) was formerly housed within the Lycée Stendhal across from the Maison du Tourisme, but later moved to its own building in the district. In the centre of the city, two high schools have provided education to the isérois for more than three centuries. The oldest one, the Lycée Stendhal, was founded in 1651 as a Jesuit College. An astronomical and astrological sundial created in the college's main building in 1673 can still be visited today. The second-oldest higher education establishment in Grenoble is the Lycée Champollion, completed in 1887 to offer an excellent education to both high school students and students of preparatory classes.

Higher education
The city is an important university centre with over 54,000 students in 2013, of whom 16% arrive from abroad.

In a 1339 pontificial bull, Pope Benedict XII commissioned the establishment of the University of Grenoble.

In 1965, the university mostly relocated from downtown to a suburban main campus outside of the city in Saint Martin d'Hères (with some parts in Gières). However, smaller campuses remain both downtown and in the northwestern part of the city known as the Polygone Scientifique ("Scientific Polygon").

From 1970 to 2015, the university was divided into four separate institutions sharing the campus grounds, some buildings and laboratories, and even part of their administration:
 * Grenoble I – Joseph Fourier University (sciences, health, technologies)
 * Grenoble II – Pierre Mendès-France University (social sciences)
 * which includes the Institute of political studies
 * Grenoble III – Stendhal University (humanities)
 * Grenoble Institute of Technology (INPG or Grenoble-INP) is a federation of engineering colleges.

The first three of those merged back on 1 January 2016 to form the Université Grenoble Alpes, and the last one joined them on 1 January 2020.

Campuses are also located in Grenoble for :
 * École nationale de l'aviation civile (French civil aviation university),
 * École d'Architecture de Grenoble ( School of Architecture of Grenoble) and
 * Grenoble École de Management (Grenoble School of Management) triple accredited AMBA-EQUIS-AACSB Business School.

Science and engineering

Grenoble is a major scientific centre, especially in the fields of physics, computer science, and applied mathematics: Universite Joseph Fourier (UJF) is one of the leading French scientific universities while the Grenoble Institute of Technology trains more than 5,000 engineers every year in key technology disciplines. Grenoble's high-tech expertise is organized mainly around three domains: information technology, biotechnologies, and new technologies of energy.

Many fundamental and applied scientific research laboratories are conjointly managed by Joseph Fourier University, Grenoble Institute of Technology, and the French National Centre for Scientific Research (CNRS). Numerous other scientific laboratories are managed independently or in collaboration with the CNRS and the French National Institute for Research in Computer Science and Control (INRIA).

Other research centres in or near Grenoble include the European Synchrotron Radiation Facility (ESRF), the Institut Laue-Langevin (ILL), the European Molecular Biology Laboratory (EMBL), the Institut de radioastronomie millimétrique, one of the main research facilities of the Commissariat à l'Énergie Atomique (Nuclear Energy Commission, CEA), the LNCMI and the European branch of Xerox Research (whose most notable center was PARC). Leti and the recent development of Minatec, a centre for innovation in micro- and nano-technology, only increases Grenoble's position as a European scientific centre. Biotechnologies are also well represented in the Grenoble region with the molecular biology research center BioMérieux, the Clinatec center, the regional center NanoBio and many ramifications of the global competitiveness cluster Lyonbiopôle.

Meanwhile, Grenoble has large laboratories related to space and to the understanding and observation of the universe as the Institut de radioastronomie millimétrique, the Institut de planétologie et d'astrophysique de Grenoble, the Laboratoire de physique subatomique et de cosmologie de Grenoble, the Institut Néel but also to a lesser extent the Institut des sciences de la Terre (part of the Observatoire des Sciences de l'Univers de Grenoble).

In order to foster this technological cluster university institutions and research organizations united to create the GIANT (Grenoble Innovation for Advanced New Technologies) Campus with the aim at becoming one of the world's top campuses in research (CEA, CNRS), higher education (INP-UGA, Grenoble Ecole de Management), and high tech.

The city benefits from the highest concentration of strategic jobs in France after Paris, with 14% of the employments, 35,186 jobs, 45% of which specialized in design and research. Grenoble is also the largest research center in France after Paris with 22,800 jobs (11,800 in public research, 7,500 in private research and 3,500 PhD students).

Grenoble is also renowned for the excellence of its academic research in humanities and political sciences. Its universities, alongside public scientific institutions, host some of the largest research centres in France (in fields such as political science, urban planning or the sociology of organizations).

Knowledge and innovation community
Grenoble is one of the co-location centres of the European Institute of Innovation and Technology's Knowledge and Innovation Communities for sustainable energy.

Economy
Industry occupies a large part of the local economy. High-tech industries have a significant presence, especially in the field of semiconductors, electronics, and biotechnology. STMicroelectronics, Schneider Electric and Soitec have major manufacturing and R&D facilities. Traditional industries in fields such as heavy equipment manufacturing and chemistry are still present and include Caterpillar, GE Renewable Energy, and Arkema.

The town was once famous for glove manufacturing, for which introduced an innovative technique in the 19th century. A few small companies continue to produce gloves for a very high-end market.

Companies
In 2011, the largest employers in the Grenoble metropolitan area were: The presence of companies such as HP or Caterpillar in the area has drawn many American and British workers to Grenoble, especially in the surrounding mountain villages. The region has the second largest English-speaking community in France, after Paris. That community has an English-speaking Church and supports the International School. Many of these Americans, British, Australians etc. go to Grenoble with the intention of returning home after some time but the mountains and general lifestyle often keep them there. Some choose to put their children in the international school "cité internationale", while the "American School of Grenoble" is the alternative for those who prefer to have the core curriculum in English. With numerous associations like Open House, this large English-speaking population organizes family events making life in Grenoble harder to turn away from.

Publisher Glénat has its head office in Grenoble. Inovallée is a science park with about 12,000 jobs located at Meylan and Montbonnot-Saint-Martin near Grenoble.

Media
téléGrenoble Isère is the local TV channel with France 3 Alpes. The local newspaper is Le Dauphiné libéré.

Sport
Grenoble hosted the 1968 Winter Olympics. The city is surrounded by ski resorts nestled in the surrounding mountains. Stade Lesdiguières is located in Grenoble and has been the venue for international rugby league and rugby union games.

Grenoble is the home of first rugby union, FC Grenoble, and ice hockey teams, Brûleurs de loups, and a second-tier football team, Grenoble Foot 38.

 * Six-Days of Grenoble, a six-day track cycling race held since 1971
 * The via ferrata Grenoble is a climbing route located on the hill of the Bastille in Grenoble.

The abundance of natural sites around Grenoble as well as the particular influence of mountaineering practices and history make many Grenoble inhabitants very fond of sports and outdoor activities (e.g., hiking, mountain biking, backcountry skiing, rock climbing, and paragliding). The Tour de France cycling race regularly passes through the city.

Transport

A comprehensive bus and tram service operates 26 bus routes and five tram lines. It serves much of greater Grenoble, while a new cable car system known as the Métrocâble is scheduled to be completed in 2022. Being essentially flat, Grenoble is also a bicycle-friendly city.

The Gare de Grenoble is served by the TGV rail network, with frequent high-speed services (3 hours) to and from Paris-Gare de Lyon, usually with a stop at Lyon Saint-Exupéry Airport. While Grenoble is not directly on any high-speed line, TGVs can run at reduced speeds on the classic network and enable such connections. Local rail services connect Grenoble with Lyon, and less frequently to Geneva, to Valence, and to destinations to the south. Valence and Lyon to the west provides connections with TGV services along the Rhône Valley. Rail and road connections to the south are less developed.

Grenoble can be accessed by air from Grenoble-Isère Airport, Lyon Saint-Exupéry Airport and Geneva International Airport, with the airport bus connections being most frequent to Lyon Saint-Exupéry.

Highways link Grenoble to the other major cities in the area including the A48 autoroute to the northwest toward Lyon, the A49 to the southwest toward the Rhone valley via Valence, the A41 to the northeast toward Chambéry, the Alps, and Italy and Switzerland.

A partial ring road around the south of the city, the Rocade Sud, connects the motorway arriving from the northwest (A48) with that arriving from the northeast (A41). A project to complete the ring road, with a tunnel under the Bastille as part of the likely routes, was rejected after its environmental impact studies.

From 2014 to 2017, the city of Grenoble tested the rental of seventy I-Road electric vehicles.

In 2016, the speed limit was lowered to 30 km/h on 80% of the streets of Grenoble and forty-two neighboring municipalities, to both improve safety and reduce pollution levels. The limit, however, remains 50 km/h on the main arteries.

Culture

Grenoble hosts several festivals: the Détours de Babel in March, the Open Air Short Film Festival in early July, and the Cabaret Frappé music festival at the end of July.

The Summum is the biggest concert hall in Grenoble, and the most famous artists produce there. Another big hall, Le grand angle, is located nearby in Voiron. Smaller halls in the city include the Salle Olivier Messiaen in the Minim Monastery.

The main cultural center of the city is called MC2 (for Maison de la culture, version 2), which hosts music, theater, and dance performances. The Conservatory of Grenoble is founded in 1935.

There are several theaters in Grenoble, the main one being Grenoble Municipal Theatre (Théatre de Grenoble). Others are the Théâtre de Création, the Théâtre Prémol, and the Théâtre 145. Grenoble also hosts Upstage Productions, which performs once a year through an exclusively English speaking troupe.

There are two main art centres in Grenoble: the Centre national d'Art contemporain (also called Le Magasin) and the Centre d'art Bastille.

Grenoble is known for its walnuts, which enjoy an appellation of controlled origin.

The town also hosts a well-known comics publisher, Glénat.

International relations
After World War I, one street in the centre of Smederevska Palanka (Serbia) was named French street (Francuska ulica) and one street in Grenoble was named Palanka street(Rue de Palanka). The same neighborhood also has a Belgrade Street (Rue de Belgrade).

Twin towns and sister cities
Grenoble is twinned with:

title: Grenoble


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List of medical abbreviations

Abbreviations are used very frequently in medicine. They boost efficiency as long as they are used intelligently. The advantages of brevity should be weighed against the possibilities of obfuscation (making the communication harder for others to understand) and ambiguity (having more than one possible interpretation). Certain medical abbreviations are avoided to prevent mistakes, according to best practices (and in some cases regulatory requirements); these are flagged in the list of abbreviations used in medical prescriptions.

Periods (stops)
Periods (stops) are often used in styling abbreviations. Prevalent practice in medicine today is often to forgo them as unnecessary. [chronic obstructive pulmonary disease]
 * Example:
 * Less common: The diagnosis was C.O.P.D.
 * More common: The diagnosis was COPD

Plurals
The prevalent way to represent plurals for medical acronyms and initialisms is simply to affix a lowercase s (no apostrophe).
 * Example: one OCP, two OCPs [oral contraceptive pills].

Possessives
Possessive forms are not often needed, but can be formed using apostrophe + s. Often the writer can also recast the sentence to avoid it.
 * Example:
 * BP's effect on risk of MI is multifaceted.
 * The effect of BP on MI risk is multifaceted.

Arrows
Arrows may be used to indicate numerous conditions including elevation (↑), diminution (↓), and causation (→, ←).

Pronunciation
Pronunciation follows convention outside the medical field, in which acronyms are generally pronounced as if they were a word (JAMA, SIDS), initialisms are generally pronounced as individual letters (DNA, SSRI), and abbreviations generally use the expansion (soln. = "solution", sup. = "superior"). Abbreviations of weights and measures are pronounced using the expansion of the unit (mg = "milligram") and chemical symbols using the chemical expansion (NaCl = "sodium chloride"). Some initialisms deriving from Latin may be pronounced either as letters (qid = "cue eye dee") or using the English expansion (qid = "four times a day").

Some common medical abbreviations
 Notation conventions
 * This series of lists omits periods from acronyms and initialisms.
 * It uses periods for certain abbreviations that traditionally often have them (mostly older Latin/Neo-Latin abbreviations). For example, both bid and b.i.d. may be found in the list.
 * It generally uses the singular form of an abbreviation (not the plural) as the headword.
 * This list uses significant capitalization for headwords (the abbreviations) and their expansions.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: List of medical abbreviations


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219

Year 219 (CCXIX) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known in Rome as the Year of the Consulship of Antonius and Sacerdos (or, less frequently, year 972 Ab urbe condita). The denomination 219 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Roman Empire

 * Imperator Marcus Aurelius Antoninus Augustus (Elagabalus) and Quintus Tineius Sacerdos become Roman Consuls.
 * Julia Maesa arranges, for her grandson Elagabalus, a marriage with Julia Paula. The wedding is a lavish ceremony and Paula is given the honorific title of Augusta.
 * Legions III Gallica and IV Scythica are disbanded by Elagabalus after their leaders, Verus and Gellius Maximus, rebel.
 * Emperor Elagabalus, age 15, is initiated into the worship of the Phrygian gods Cybele and Attis.

India

 * The reign of Pulona, Satavahana king of Andhra, begins in India.

China

 * The Battle of Mount Dingjun ends with Liu Bei emerging victorious. He declares himself king of Hanzhong afterwards.
 * Guan Yu floods the fortress at Fan (present-day Fancheng District, Xiangyang, Hubei) in the Battle of Fancheng, while Lü Meng captures his base in Jing Province. Guan Yu retreats to Maicheng, falls into an ambush, and gets captured by Sun Quan's forces.
 * Cao Cao controls the Yellow River basin and northern China. Sun Quan rules southern China. Liu Bei controls Yi Province (covering present-day Sichuan and Chongqing).
 * Tuoba Liwei becomes the first chieftain of the Tuoba clan of the Xianbei people.

Births

 * Hua He (or Yongxian), Chinese official and historian (d. 278)
 * Sun Jun (or Ziyuan), Chinese general and regent (d. 256)

Deaths

 * Jiang Qin (or Gongyi), Chinese general serving under Sun Quan
 * Lu Ji (or Gongji), Chinese scholar, official and politician (b. 188)
 * Marcus Munatius Sulla Cerialis, Roman governor and politician
 * Pang De (or Lingming), Chinese general serving under Cao Cao
 * Sima Fang (or Jianong), Chinese official and politician (b. 149)
 * Sun Jiao (or Shulang), Chinese general serving under Sun Quan
 * Xiahou Yuan (or Miaocai), Chinese general serving under Cao Cao
 * Yang Xiu (or Dezi), Chinese official, adviser and chancellor (b. 175)
 * Zhang Zhongjing, Chinese physician and pharmacologist (b. 150)

title: 219


text:
906

Year 906 (CMVI) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar.

Europe

 * February 27 – Battle of Fritzlar: The Conradines defeat the Babenberg counts, to establish themselves as dukes of Franconia (modern-day Bavaria). Count Conrad the Elder is killed in the battle; his son Conrad the Younger becomes duke of Franconia.
 * Summer – Duke Mojmir II halts the advance of the plundering Hungarians under Grand Prince Árpád in Great Moravia (approximate date).

Britain

 * King Constantine II of Scotland calls for an assembly to meet at Scone. Scottish Christian clergy under Bishop Cellach pledges that the laws and disciplines of the faith, and the laws of churches and gospels, should be kept pariter cum Scottis.

Arabian Empire

 * October 22 – Abbasid commander Ahmad ibn Kayghalagh leads a raid against the Byzantine Empire from Tarsus, joined by the governor Rustam ibn Baradu. He reaches the Halys River and takes 4,000–5,000 captives.

Asia

 * January 22 – The warlord Zhu Quanzhong secretly puts Empress Dowager He, the wife of the late Emperor Zhaozong and mother of the reigning Emperor Ai, to death (by strangulation) and has her defamed and posthumously demoted to commoner rank.

Armenia

 * 906 K'argop' earthquake. It took place in the monastery K'argop', Armenia. The monastery was also known as Xotakerk', the monastery of the Vegetarians. The earthquake occurred approximately 150 years following the 735 Vayots Dzor Province earthquake, and affected the same region.

Births

 * June 21 – Abu Ja'far Ahmad ibn Muhammad, Saffarid emir (d. 963)
 * Abu Tahir al-Jannabi, Qarmatian ruler (d. 944)
 * Fujiwara no Atsutada, Japanese nobleman (d. 943)
 * Guan Tong, Chinese landscape painter (approximate date)
 * Liu Congxiao, Chinese general (d. 962)
 * Majolus of Cluny, Frankish abbot (approximate date)
 * Nasr II, Samanid emir (d. 943)
 * Sherira Gaon, Jewish spiritual leader (d. 1006)

Deaths

 * January 22 – He, empress of the Tang dynasty
 * January 27 – Liu Can, chancellor of the Tang dynasty
 * February 27 – Conrad the Elder, Frankish nobleman
 * September 9 – Adalbert von Babenberg, Frankish nobleman
 * Acfred I, Frankish nobleman (approximate date)
 * Dae Wihae, king of Balhae (Korea)
 * Tughj ibn Juff, Abbasid governor
 * Zhong Chuan, Chinese warlord

title: 906


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CT scan

A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists.

CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry to measure X-ray attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is contraindicated.

Since its development in the 1970s, CT scanning has proven to be a versatile imaging technique. While CT is most prominently used in medical diagnosis, it can also be used to form images of non-living objects. The 1979 Nobel Prize in Physiology or Medicine was awarded jointly to South African-American physicist Allan MacLeod Cormack and British electrical engineer Godfrey Hounsfield "for the development of computer-assisted tomography".

Types
On the basis of image acquisition and procedures, various type of scanners are available in the market.

Sequential CT
Sequential CT, also known as step-and-shoot CT, is a type of scanning method in which the CT table moves stepwise. The table increments to a particular location and then stops which is followed by the X-ray tube rotation and acquisition of a slice. The table then increments again, and another slice is taken. The table movement stops while taking slices. This results in an increased time of scanning.

Spiral CT
Spinning tube, commonly called spiral CT, or helical CT, is an imaging technique in which an entire X-ray tube is spun around the central axis of the area being scanned. These are the dominant type of scanners on the market because they have been manufactured longer and offer a lower cost of production and purchase. The main limitation of this type of CT is the bulk and inertia of the equipment (X-ray tube assembly and detector array on the opposite side of the circle) which limits the speed at which the equipment can spin. Some designs use two X-ray sources and detector arrays offset by an angle, as a technique to improve temporal resolution.

Electron beam tomography
Electron beam tomography (EBT) is a specific form of CT in which a large enough X-ray tube is constructed so that only the path of the electrons, travelling between the cathode and anode of the X-ray tube, are spun using deflection coils. This type had a major advantage since sweep speeds can be much faster, allowing for less blurry imaging of moving structures, such as the heart and arteries. Fewer scanners of this design have been produced when compared with spinning tube types, mainly due to the higher cost associated with building a much larger X-ray tube and detector array and limited anatomical coverage.

Dual Energy CT
Dual Energy CT, also known as Spectral CT, is an advancement of Computed Tomography in which two energies are used to create two sets of data. A Dual Energy CT may employ Dual source, Single source with dual detector layer, Single source with energy switching methods to get two different sets of data.
 * 1) Dual source CT is an advanced scanner with a two X-ray tube detector system, unlike conventional single tube systems. These two detector systems are mounted on a single gantry at 90° in the same plane. Dual Source CT scanners allow fast scanning with higher temporal resolution by acquiring a full CT slice in only half a rotation. Fast imaging reduces motion blurring at high heart rates and potentially allowing for shorter breath-hold time. This is particularly useful for ill patients having difficulty holding their breath or unable to take heart-rate lowering medication.
 * 2) Single Source with Energy switching is another mode of Dual energy CT in which a single tube is operated at two different energies by switching the energies frequently.

CT perfusion imaging
CT perfusion imaging is a specific form of CT to assess flow through blood vessels whilst injecting a contrast agent. Blood flow, blood transit time, and organ blood volume, can all be calculated with reasonable sensitivity and specificity. This type of CT may be used on the heart, although sensitivity and specificity for detecting abnormalities are still lower than for other forms of CT. This may also be used on the brain, where CT perfusion imaging can often detect poor brain perfusion well before it is detected using a conventional spiral CT scan. This is better for stroke diagnosis than other CT types.

PET CT
Positron emission tomography–computed tomography is a hybrid CT modality which combines, in a single gantry, a positron emission tomography (PET) scanner and an X-ray computed tomography (CT) scanner, to acquire sequential images from both devices in the same session, which are combined into a single superposed (co-registered) image. Thus, functional imaging obtained by PET, which depicts the spatial distribution of metabolic or biochemical activity in the body can be more precisely aligned or correlated with anatomic imaging obtained by CT scanning.

PET-CT gives both anatomical and functional details of an organ under examination and is helpful in detecting different type of cancers.

Medical use
Since its introduction in the 1970s, CT has become an important tool in medical imaging to supplement conventional X-ray imaging and medical ultrasonography. It has more recently been used for preventive medicine or screening for disease, for example, CT colonography for people with a high risk of colon cancer, or full-motion heart scans for people with a high risk of heart disease. Several institutions offer full-body scans for the general population although this practice goes against the advice and official position of many professional organizations in the field primarily due to the radiation dose applied.

The use of CT scans has increased dramatically over the last two decades in many countries. An estimated 72 million scans were performed in the United States in 2007 and more than 80 million in 2015.

Head
CT scanning of the head is typically used to detect infarction (stroke), tumors, calcifications, haemorrhage, and bone trauma. Of the above, hypodense (dark) structures can indicate edema and infarction, hyperdense (bright) structures indicate calcifications and haemorrhage and bone trauma can be seen as disjunction in bone windows. Tumors can be detected by the swelling and anatomical distortion they cause, or by surrounding edema. CT scanning of the head is also used in CT-guided stereotactic surgery and radiosurgery for treatment of intracranial tumors, arteriovenous malformations, and other surgically treatable conditions using a device known as the N-localizer.

Neck
Contrast CT is generally the initial study of choice for neck masses in adults. CT of the thyroid plays an important role in the evaluation of thyroid cancer. CT scan often incidentally finds thyroid abnormalities, and so is often the preferred investigation modality for thyroid abnormalities.

Lungs
A CT scan can be used for detecting both acute and chronic changes in the lung parenchyma, the tissue of the lungs. It is particularly relevant here because normal two-dimensional X-rays do not show such defects. A variety of techniques are used, depending on the suspected abnormality. For evaluation of chronic interstitial processes such as emphysema, and fibrosis, thin sections with high spatial frequency reconstructions are used; often scans are performed both on inspiration and expiration. This special technique is called high resolution CT that produces a sampling of the lung, and not continuous images.

Bronchial wall thickening can be seen on lung CTs and generally (but not always) implies inflammation of the bronchi.

An incidentally found nodule in the absence of symptoms (sometimes referred to as an incidentaloma) may raise concerns that it might represent a tumor, either benign or malignant. Perhaps persuaded by fear, patients and doctors sometimes agree to an intensive schedule of CT scans, sometimes up to every three months and beyond the recommended guidelines, in an attempt to do surveillance on the nodules., which cites
 * However, established guidelines advise that patients without a prior history of cancer and whose solid nodules have not grown over a two-year period are unlikely to have any malignant cancer. For this reason, and because no research provides supporting evidence that intensive surveillance gives better outcomes, and because of risks associated with having CT scans, patients should not receive CT screening in excess of those recommended by established guidelines.
 * However, established guidelines advise that patients without a prior history of cancer and whose solid nodules have not grown over a two-year period are unlikely to have any malignant cancer. For this reason, and because no research provides supporting evidence that intensive surveillance gives better outcomes, and because of risks associated with having CT scans, patients should not receive CT screening in excess of those recommended by established guidelines.
 * However, established guidelines advise that patients without a prior history of cancer and whose solid nodules have not grown over a two-year period are unlikely to have any malignant cancer. For this reason, and because no research provides supporting evidence that intensive surveillance gives better outcomes, and because of risks associated with having CT scans, patients should not receive CT screening in excess of those recommended by established guidelines.
 * However, established guidelines advise that patients without a prior history of cancer and whose solid nodules have not grown over a two-year period are unlikely to have any malignant cancer. For this reason, and because no research provides supporting evidence that intensive surveillance gives better outcomes, and because of risks associated with having CT scans, patients should not receive CT screening in excess of those recommended by established guidelines.

Angiography

Computed tomography angiography (CTA) is a type of contrast CT to visualize the arteries and veins throughout the body. This ranges from arteries serving the brain to those bringing blood to the lungs, kidneys, arms and legs. An example of this type of exam is CT pulmonary angiogram (CTPA) used to diagnose pulmonary embolism (PE). It employs computed tomography and an iodine-based contrast agent to obtain an image of the pulmonary arteries.

Cardiac
A CT scan of the heart is performed to gain knowledge about cardiac or coronary anatomy. Traditionally, cardiac CT scans are used to detect, diagnose, or follow up coronary artery disease. More recently CT has played a key role in the fast-evolving field of transcatheter structural heart interventions, more specifically in the transcatheter repair and replacement of heart valves.

The main forms of cardiac CT scanning are:
 * Coronary CT angiography (CCTA): the use of CT to assess the coronary arteries of the heart. The subject receives an intravenous injection of radiocontrast, and then the heart is scanned using a high-speed CT scanner, allowing radiologists to assess the extent of occlusion in the coronary arteries, usually to diagnose coronary artery disease.
 * Coronary CT calcium scan: also used for the assessment of severity of coronary artery disease. Specifically, it looks for calcium deposits in the coronary arteries that can narrow arteries and increase the risk of a heart attack. A typical coronary CT calcium scan is done without the use of radiocontrast, but it can possibly be done from contrast-enhanced images as well.

To better visualize the anatomy, post-processing of the images is common. Most common are multiplanar reconstructions (MPR) and volume rendering. For more complex anatomies and procedures, such as heart valve interventions, a true 3D reconstruction or a 3D print is created based on these CT images to gain a deeper understanding.

Abdomen and pelvis

CT is an accurate technique for diagnosis of abdominal diseases like Crohn's disease, GIT bleeding, and diagnosis and staging of cancer, as well as follow-up after cancer treatment to assess response. It is commonly used to investigate acute abdominal pain.

Non-enhanced computed tomography is today the gold standard for diagnosing urinary stones. The size, volume and density of stones can be estimated to help clinicians guide further treatment; size is especially important in predicting spontaneous passage of a stone.

Axial skeleton and extremities
For the axial skeleton and extremities, CT is often used to image complex fractures, especially ones around joints, because of its ability to reconstruct the area of interest in multiple planes. Fractures, ligamentous injuries, and dislocations can easily be recognized with a 0.2 mm resolution. With modern dual-energy CT scanners, new areas of use have been established, such as aiding in the diagnosis of gout.

Biomechanical use
CT is used in biomechanics to quickly reveal the geometry, anatomy, density and elastic moduli of biological tissues.

Industrial use
Industrial CT scanning (industrial computed tomography) is a process which uses X-ray equipment to produce 3D representations of components both externally and internally. Industrial CT scanning has been used in many areas of industry for internal inspection of components. Some of the key uses for CT scanning have been flaw detection, failure analysis, metrology, assembly analysis, image-based finite element methods and reverse engineering applications. CT scanning is also employed in the imaging and conservation of museum artifacts.

Aviation security
CT scanning has also found an application in transport security (predominantly airport security) where it is currently used in a materials analysis context for explosives detection CTX (explosive-detection device)  and is also under consideration for automated baggage/parcel security scanning using computer vision based object recognition algorithms that target the detection of specific threat items based on 3D appearance (e.g. guns, knives, liquid containers). Its usage in airport security pioneered at Shannon Airport in March 2022 has ended the ban on liquids over 100 ml there, a move that Heathrow Airport plans for a full roll-out on 1 December 2022 and the TSA spent $781.2 million on an order for over 1,000 scanners, ready to go live in the summer.

Geological use
X-ray CT is used in geological studies to quickly reveal materials inside a drill core. Dense minerals such as pyrite and barite appear brighter and less dense components such as clay appear dull in CT images.

Cultural heritage use
X-ray CT and micro-CT can also be used for the conservation and preservation of objects of cultural heritage. For many fragile objects, direct research and observation can be damaging and can degrade the object over time. Using CT scans, conservators and researchers are able to determine the material composition of the objects they are exploring, such as the position of ink along the layers of a scroll, without any additional harm. These scans have been optimal for research focused on the workings of the Antikythera mechanism or the text hidden inside the charred outer layers of the En-Gedi Scroll. However, they are not optimal for every object subject to these kinds of research questions, as there are certain artifacts like the Herculaneum papyri in which the material composition has very little variation along the inside of the object. After scanning these objects, computational methods can be employed to examine the insides of these objects, as was the case with the virtual unwrapping of the En-Gedi scroll and the Herculaneum papyri. Micro-CT has also proved useful for analyzing more recent artifacts such as still-sealed historic correspondence that employed the technique of letterlocking (complex folding and cuts) that provided a "tamper-evident locking mechanism". Further examples of use cases in archaeology is imaging the contents of sarcophagi or ceramics.

Recently, CWI in Amsterdam has collaborated with Rijksmuseum to investigate art object inside details in the framework called IntACT.

Micro organism research
Varied types of fungus can degrade wood to different degrees, one Belgium research group has been used X-ray CT 3 dimension with sub-micron resolution unveiled fungi can penetrate micropores of 0.6 μm under certain conditions.

Timber sawmill
Sawmills use industrial CT scanners to detect round defects, for instance knots, to improve total value of timber productions. Most sawmills are planning to incorporate this robust detection tool to improve productivity in the long run, however initial investment cost is high.

Presentation

The result of a CT scan is a volume of voxels, which may be presented to a human observer by various methods, which broadly fit into the following categories:
 * Slices (of varying thickness). Thin slice is generally regarded as planes representing a thickness of less than 3 mm. Thick slice is generally regarded as planes representing a thickness between 3 mm and 5 mm.
 * Projection, including maximum intensity projection and average intensity projection
 * Volume rendering (VR)

Technically, all volume renderings become projections when viewed on a 2-dimensional display, making the distinction between projections and volume renderings a bit vague. The epitomes of volume rendering models feature a mix of for example coloring and shading in order to create realistic and observable representations.

Two-dimensional CT images are conventionally rendered so that the view is as though looking up at it from the patient's feet. Hence, the left side of the image is to the patient's right and vice versa, while anterior in the image also is the patient's anterior and vice versa. This left-right interchange corresponds to the view that physicians generally have in reality when positioned in front of patients.

Grayscale
Pixels in an image obtained by CT scanning are displayed in terms of relative radiodensity. The pixel itself is displayed according to the mean attenuation of the tissue(s) that it corresponds to on a scale from +3,071 (most attenuating) to −1,024 (least attenuating) on the Hounsfield scale. A pixel is a two dimensional unit based on the matrix size and the field of view. When the CT slice thickness is also factored in, the unit is known as a voxel, which is a three-dimensional unit. Water has an attenuation of 0 Hounsfield units (HU), while air is −1,000 HU, cancellous bone is typically +400 HU, and cranial bone can reach 2,000 HU. The attenuation of metallic implants depends on the atomic number of the element used: Titanium usually has an amount of +1000 HU, iron steel can completely block the X-ray and is, therefore, responsible for well-known line-artifacts in computed tomograms. Artifacts are caused by abrupt transitions between low- and high-density materials, which results in data values that exceed the dynamic range of the processing electronics.

Windowing
CT data sets have a very high dynamic range which must be reduced for display or printing. This is typically done via a process of "windowing", which maps a range (the "window") of pixel values to a grayscale ramp. For example, CT images of the brain are commonly viewed with a window extending from 0 HU to 80 HU. Pixel values of 0 and lower, are displayed as black; values of 80 and higher are displayed as white; values within the window are displayed as a gray intensity proportional to position within the window. The window used for display must be matched to the X-ray density of the object of interest, in order to optimize the visible detail. Window width and window level parameters are used to control the windowing of a scan.

Multiplanar reconstruction and projections
Multiplanar reconstruction (MPR) is the process of converting data from one anatomical plane (usually transverse) to other planes. It can be used for thin slices as well as projections. Multiplanar reconstruction is possible as present CT scanners provide almost isotropic resolution.

MPR is used almost in every scan. The spine is frequently examined with it. An image of the spine in axial plane can only show one vertebral bone at a time and cannot show its relation with other vertebral bones. By reformatting the data in other planes, visualization of the relative position can be achieved in sagittal and coronal plane.

New software allows the reconstruction of data in non-orthogonal (oblique) planes, which help in the visualization of organs which are not in orthogonal planes. It is better suited for visualization of the anatomical structure of the bronchi as they do not lie orthogonal to the direction of the scan.

Curved-plane reconstruction (or curved planar reformation = CPR) is performed mainly for the evaluation of vessels. This type of reconstruction helps to straighten the bends in a vessel, thereby helping to visualize a whole vessel in a single image or in multiple images. After a vessel has been "straightened", measurements such as cross-sectional area and length can be made. This is helpful in preoperative assessment of a surgical procedure.

For 2D projections used in radiation therapy for quality assurance and planning of external beam radiotherapy, including digitally reconstructed radiographs, see Beam's eye view.

Volume rendering

A threshold value of radiodensity is set by the operator (e.g., a level that corresponds to bone). With the help of edge detection image processing algorithms a 3D model can be constructed from the initial data and displayed on screen. Various thresholds can be used to get multiple models, each anatomical component such as muscle, bone and cartilage can be differentiated on the basis of different colours given to them. However, this mode of operation cannot show interior structures.

Surface rendering is limited technique as it displays only the surfaces that meet a particular threshold density, and which are towards the viewer. However, In volume rendering, transparency, colours and shading are used which makes it easy to present a volume in a single image. For example, Pelvic bones could be displayed as semi-transparent, so that, even viewing at an oblique angle one part of the image does not hide another.

Dose versus image quality
An important issue within radiology today is how to reduce the radiation dose during CT examinations without compromising the image quality. In general, higher radiation doses result in higher-resolution images, while lower doses lead to increased image noise and unsharp images. However, increased dosage raises the adverse side effects, including the risk of radiation-induced cancer – a four-phase abdominal CT gives the same radiation dose as 300 chest X-rays. Several methods that can reduce the exposure to ionizing radiation during a CT scan exist.

 * 1) New software technology can significantly reduce the required radiation dose. New iterative tomographic reconstruction algorithms (e.g., iterative Sparse Asymptotic Minimum Variance) could offer super-resolution without requiring higher radiation dose.
 * 2) Individualize the examination and adjust the radiation dose to the body type and body organ examined. Different body types and organs require different amounts of radiation.
 * 3) Higher resolution is not always suitable, such as detection of small pulmonary masses.

Artifacts
Although images produced by CT are generally faithful representations of the scanned volume, the technique is susceptible to a number of artifacts, such as the following: Chapters 3 and 5

 * Streaks are often seen around materials that block most X-rays, such as metal or bone. Numerous factors contribute to these streaks: under sampling, photon starvation, motion, beam hardening, and Compton scatter. This type of artifact commonly occurs in the posterior fossa of the brain, or if there are metal implants. The streaks can be reduced using newer reconstruction techniques. Approaches such as metal artifact reduction (MAR) can also reduce this artifact. MAR techniques include spectral imaging, where CT images are taken with photons of different energy levels, and then synthesized into monochromatic images with special software such as GSI (Gemstone Spectral Imaging).

 * Partial volume effect: This appears as "blurring" of edges. It is due to the scanner being unable to differentiate between a small amount of high-density material (e.g., bone) and a larger amount of lower density (e.g., cartilage). The reconstruction assumes that the X-ray attenuation within each voxel is homogeneous; this may not be the case at sharp edges. This is most commonly seen in the z-direction (craniocaudal direction), due to the conventional use of highly anisotropic voxels, which have a much lower out-of-plane resolution, than in-plane resolution. This can be partially overcome by scanning using thinner slices, or an isotropic acquisition on a modern scanner.

 * Ring artifact: Probably the most common mechanical artifact, the image of one or many "rings" appears within an image. They are usually caused by the variations in the response from individual elements in a two dimensional X-ray detector due to defect or miscalibration. Ring artifacts can largely be reduced by intensity normalization, also referred to as flat field correction. Remaining rings can be suppressed by a transformation to polar space, where they become linear stripes. A comparative evaluation of ring artefact reduction on X-ray tomography images showed that the method of Sijbers and Postnov can effectively suppress ring artefacts.

 * Noise: This appears as grain on the image and is caused by a low signal to noise ratio. This occurs more commonly when a thin slice thickness is used. It can also occur when the power supplied to the X-ray tube is insufficient to penetrate the anatomy.

 * Windmill: Streaking appearances can occur when the detectors intersect the reconstruction plane. This can be reduced with filters or a reduction in pitch.

 * Beam hardening: This can give a "cupped appearance" when grayscale is visualized as height. It occurs because conventional sources, like X-ray tubes emit a polychromatic spectrum. Photons of higher photon energy levels are typically attenuated less. Because of this, the mean energy of the spectrum increases when passing the object, often described as getting "harder". This leads to an effect increasingly underestimating material thickness, if not corrected. Many algorithms exist to correct for this artifact. They can be divided into mono- and multi-material methods.

Advantages
CT scanning has several advantages over traditional two-dimensional medical radiography. First, CT eliminates the superimposition of images of structures outside the area of interest. Second, CT scans have greater image resolution, enabling examination of finer details. CT can distinguish between tissues that differ in radiographic density by 1% or less. Third, CT scanning enables multiplanar reformatted imaging: scan data can be visualized in the transverse (or axial), coronal, or sagittal plane, depending on the diagnostic task.

The improved resolution of CT has permitted the development of new investigations. For example, CT angiography avoids the invasive insertion of a catheter. CT scanning can perform a virtual colonoscopy with greater accuracy and less discomfort for the patient than a traditional colonoscopy. Virtual colonography is far more accurate than a barium enema for detection of tumors and uses a lower radiation dose.

CT is a moderate-to-high radiation diagnostic technique. The radiation dose for a particular examination depends on multiple factors: volume scanned, patient build, number and type of scan protocol, and desired resolution and image quality. Two helical CT scanning parameters, tube current and pitch, can be adjusted easily and have a profound effect on radiation. CT scanning is more accurate than two-dimensional radiographs in evaluating anterior interbody fusion, although they may still over-read the extent of fusion.

Cancer
The radiation used in CT scans can damage body cells, including DNA molecules, which can lead to radiation-induced cancer. The radiation doses received from CT scans is variable. Compared to the lowest dose X-ray techniques, CT scans can have 100 to 1,000 times higher dose than conventional X-rays. However, a lumbar spine X-ray has a similar dose as a head CT. Articles in the media often exaggerate the relative dose of CT by comparing the lowest-dose X-ray techniques (chest X-ray) with the highest-dose CT techniques. In general, a routine abdominal CT has a radiation dose similar to three years of average background radiation.

Large scale population-based studies have consistently demonstrated that low dose radiation from CT scans has impacts on cancer incidence in a variety of cancers. For example, in a large population-based cohort it was found that up to 4% of brain cancers were caused by CT scan radiation. Some experts project that in the future, between three and five percent of all cancers would result from medical imaging. An Australian study of 10.9 million people reported that the increased incidence of cancer after CT scan exposure in this cohort was mostly due to irradiation. In this group, one in every 1,800 CT scans was followed by an excess cancer. If the lifetime risk of developing cancer is 40% then the absolute risk rises to 40.05% after a CT. The risks of CT scan radiation are especially important in patients undergoing recurrent CT scans within a short time span of one to five years.

Some experts note that CT scans are known to be "overused," and "there is distressingly little evidence of better health outcomes associated with the current high rate of scans." On the other hand, a recent paper analyzing the data of patients who received high cumulative doses showed a high degree of appropriate use. This creates an important issue of cancer risk to these patients. Moreover, a highly significant finding that was previously unreported is that some patients received >100 mSv dose from CT scans in a single day, which counteracts existing criticisms some investigators may have on the effects of protracted versus acute exposure.

There are contrarian views and the debate is ongoing. Some studies have shown that publications indicating an increased risk of cancer from typical doses of body CT scans are plagued with serious methodological limitations and several highly improbable results, concluding that no evidence indicates such low doses cause any long-term harm. One study estimated that as many as 0.4% of cancers in the United States resulted from CT scans, and that this may have increased to as much as 1.5 to 2% based on the rate of CT use in 2007. Others dispute this estimate, as there is no consensus that the low levels of radiation used in CT scans cause damage. Lower radiation doses are used in many cases, such as in the investigation of renal colic.

A person's age plays a significant role in the subsequent risk of cancer. Estimated lifetime cancer mortality risks from an abdominal CT of a one-year-old is 0.1%, or 1:1000 scans. The risk for someone who is 40 years old is half that of someone who is 20 years old with substantially less risk in the elderly. The International Commission on Radiological Protection estimates that the risk to a fetus being exposed to 10 mGy (a unit of radiation exposure) increases the rate of cancer before 20 years of age from 0.03% to 0.04% (for reference a CT pulmonary angiogram exposes a fetus to 4 mGy). A 2012 review did not find an association between medical radiation and cancer risk in children noting however the existence of limitations in the evidences over which the review is based. CT scans can be performed with different settings for lower exposure in children with most manufacturers of CT scans as of 2007 having this function built in. Furthermore, certain conditions can require children to be exposed to multiple CT scans.

Current recommendations are to inform patients of the risks of CT scanning. However, employees of imaging centers tend not to communicate such risks unless patients ask.

Contrast reactions
In the United States half of CT scans are contrast CTs using intravenously injected radiocontrast agents. The most common reactions from these agents are mild, including nausea, vomiting, and an itching rash. Severe life-threatening reactions may rarely occur. Overall reactions occur in 1 to 3% with nonionic contrast and 4 to 12% of people with ionic contrast. Skin rashes may appear within a week to 3% of people.

The old radiocontrast agents caused anaphylaxis in 1% of cases while the newer, low-osmolar agents cause reactions in 0.01–0.04% of cases. Death occurs in about 2 to 30 people per 1,000,000 administrations, with newer agents being safer. There is a higher risk of mortality in those who are female, elderly or in poor health, usually secondary to either anaphylaxis or acute kidney injury.

The contrast agent may induce contrast-induced nephropathy. This occurs in 2 to 7% of people who receive these agents, with greater risk in those who have preexisting kidney failure, preexisting diabetes, or reduced intravascular volume. People with mild kidney impairment are usually advised to ensure full hydration for several hours before and after the injection. For moderate kidney failure, the use of iodinated contrast should be avoided; this may mean using an alternative technique instead of CT. Those with severe kidney failure requiring dialysis require less strict precautions, as their kidneys have so little function remaining that any further damage would not be noticeable and the dialysis will remove the contrast agent; it is normally recommended, however, to arrange dialysis as soon as possible following contrast administration to minimize any adverse effects of the contrast.

In addition to the use of intravenous contrast, orally administered contrast agents are frequently used when examining the abdomen. These are frequently the same as the intravenous contrast agents, merely diluted to approximately 10% of the concentration. However, oral alternatives to iodinated contrast exist, such as very dilute (0.5–1% w/v) barium sulfate suspensions. Dilute barium sulfate has the advantage that it does not cause allergic-type reactions or kidney failure, but cannot be used in patients with suspected bowel perforation or suspected bowel injury, as leakage of barium sulfate from damaged bowel can cause fatal peritonitis.

Side effects from contrast agents, administered intravenously in some CT scans, might impair kidney performance in patients with kidney disease, although this risk is now believed to be lower than previously thought.

Scan dose
The table reports average radiation exposures; however, there can be a wide variation in radiation doses between similar scan types, where the highest dose could be as much as 22 times higher than the lowest dose. A typical plain film X-ray involves radiation dose of 0.01 to 0.15 mGy, while a typical CT can involve 10–20 mGy for specific organs, and can go up to 80 mGy for certain specialized CT scans.

For purposes of comparison, the world average dose rate from naturally occurring sources of background radiation is 2.4 mSv per year, equal for practical purposes in this application to 2.4 mGy per year. While there is some variation, most people (99%) received less than 7 mSv per year as background radiation. Medical imaging as of 2007 accounted for half of the radiation exposure of those in the United States with CT scans making up two thirds of this amount. In the United Kingdom it accounts for 15% of radiation exposure. The average radiation dose from medical sources is ≈0.6 mSv per person globally as of 2007. Those in the nuclear industry in the United States are limited to doses of 50 mSv a year and 100 mSv every 5 years.

Lead is the main material used by radiography personnel for shielding against scattered X-rays.

Radiation dose units
The radiation dose reported in the gray or mGy unit is proportional to the amount of energy that the irradiated body part is expected to absorb, and the physical effect (such as DNA double strand breaks) on the cells' chemical bonds by X-ray radiation is proportional to that energy.

The sievert unit is used in the report of the effective dose. The sievert unit, in the context of CT scans, does not correspond to the actual radiation dose that the scanned body part absorbs but to another radiation dose of another scenario, the whole body absorbing the other radiation dose and the other radiation dose being of a magnitude, estimated to have the same probability to induce cancer as the CT scan. Thus, as is shown in the table above, the actual radiation that is absorbed by a scanned body part is often much larger than the effective dose suggests. A specific measure, termed the computed tomography dose index (CTDI), is commonly used as an estimate of the radiation absorbed dose for tissue within the scan region, and is automatically computed by medical CT scanners.

The equivalent dose is the effective dose of a case, in which the whole body would actually absorb the same radiation dose, and the sievert unit is used in its report. In the case of non-uniform radiation, or radiation given to only part of the body, which is common for CT examinations, using the local equivalent dose alone would overstate the biological risks to the entire organism.

Effects of radiation
Most adverse health effects of radiation exposure may be grouped in two general categories:
 * deterministic effects (harmful tissue reactions) due in large part to the killing/malfunction of cells following high doses;
 * stochastic effects, i.e., cancer and heritable effects involving either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive (germ) cells.

The added lifetime risk of developing cancer by a single abdominal CT of 8 mSv is estimated to be 0.05%, or 1 one in 2,000.

Because of increased susceptibility of fetuses to radiation exposure, the radiation dosage of a CT scan is an important consideration in the choice of medical imaging in pregnancy.

Excess doses
In October, 2009, the US Food and Drug Administration (FDA) initiated an investigation of brain perfusion CT (PCT) scans, based on radiation burns caused by incorrect settings at one particular facility for this particular type of CT scan. Over 200 patients were exposed to radiation at approximately eight times the expected dose for an 18-month period; over 40% of them lost patches of hair. This event prompted a call for increased CT quality assurance programs. It was noted that "while unnecessary radiation exposure should be avoided, a medically needed CT scan obtained with appropriate acquisition parameter has benefits that outweigh the radiation risks." Similar problems have been reported at other centers. These incidents are believed to be due to human error.

Procedure
CT scan procedure varies according to the type of the study and the organ being imaged. The patient is made to lie on the CT table and the centering of the table is done according to the body part. The IV line is established in case of contrast-enhanced CT. After selecting proper and rate of contrast from the pressure injector, the scout is taken to localize and plan the scan. Once the plan is selected, the contrast is given. The raw data is processed according to the study and proper windowing is done to make scans easy to diagnose.

Preparation
Patient preparation may vary according to the type of scan. The general patient preparation includes.
 * 1) Signing the informed consent.
 * 2) Removal of metallic objects and jewelry from the region of interest.
 * 3) Changing to the hospital gown according to hospital protocol.
 * 4) Checking of kidney function, especially creatinine and urea levels (in case of CECT).

Mechanism
[[File:ct-internals.jpg|thumb|right|CT scanner with cover removed to show internal components. Legend:

T: X-ray tube

D: X-ray detectors

X: X-ray beam

R: Gantry rotation]]

Computed tomography operates by using an X-ray generator that rotates around the object; X-ray detectors are positioned on the opposite side of the circle from the X-ray source. As the X-rays pass through the patient, they are attenuated differently by various tissues according to the tissue density. A visual representation of the raw data obtained is called a sinogram, yet it is not sufficient for interpretation. Once the scan data has been acquired, the data must be processed using a form of tomographic reconstruction, which produces a series of cross-sectional images. These cross-sectional images are made up of small units of pixels or voxels.

Pixels in an image obtained by CT scanning are displayed in terms of relative radiodensity. The pixel itself is displayed according to the mean attenuation of the tissue(s) that it corresponds to on a scale from +3,071 (most attenuating) to −1,024 (least attenuating) on the Hounsfield scale. A pixel is a two dimensional unit based on the matrix size and the field of view. When the CT slice thickness is also factored in, the unit is known as a voxel, which is a three-dimensional unit.

Water has an attenuation of 0 Hounsfield units (HU), while air is −1,000 HU, cancellous bone is typically +400 HU, and cranial bone can reach 2,000 HU or more (os temporale) and can cause artifacts. The attenuation of metallic implants depends on the atomic number of the element used: Titanium usually has an amount of +1000 HU, iron steel can completely extinguish the X-ray and is, therefore, responsible for well-known line-artifacts in computed tomograms. Artifacts are caused by abrupt transitions between low- and high-density materials, which results in data values that exceed the dynamic range of the processing electronics. Two-dimensional CT images are conventionally rendered so that the view is as though looking up at it from the patient's feet. Hence, the left side of the image is to the patient's right and vice versa, while anterior in the image also is the patient's anterior and vice versa. This left-right interchange corresponds to the view that physicians generally have in reality when positioned in front of patients.

Initially, the images generated in CT scans were in the transverse (axial) anatomical plane, perpendicular to the long axis of the body. Modern scanners allow the scan data to be reformatted as images in other planes. Digital geometry processing can generate a three-dimensional image of an object inside the body from a series of two-dimensional radiographic images taken by rotation around a fixed axis. These cross-sectional images are widely used for medical diagnosis and therapy.

Contrast
Contrast media used for X-ray CT, as well as for plain film X-ray, are called radiocontrasts. Radiocontrasts for CT are, in general, iodine-based. This is useful to highlight structures such as blood vessels that otherwise would be difficult to delineate from their surroundings. Using contrast material can also help to obtain functional information about tissues. Often, images are taken both with and without radiocontrast.

History
The history of X-ray computed tomography goes back to at least 1917 with the mathematical theory of the Radon transform. In October 1963, William H. Oldendorf received a U.S. patent for a "radiant energy apparatus for investigating selected areas of interior objects obscured by dense material". The first commercially viable CT scanner was invented by Godfrey Hounsfield in 1972.

It is often claimed that revenues from the sales of The Beatles' records in the 1960s helped fund the development of the first CT scanner at EMI. The first production X-ray CT machines were in fact called EMI scanners.

Etymology
The word tomography is derived from the Greek tome 'slice' and graphein 'to write'. Computed tomography was originally known as the "EMI scan" as it was developed in the early 1970s at a research branch of EMI, a company best known today for its music and recording business. It was later known as computed axial tomography (CAT or CT scan) and body section röntgenography.

The term CAT scan is no longer in technical use because current CT scans enable for multiplanar reconstructions. This makes CT scan the most appropriate term, which is used by radiologists in common vernacular as well as in textbooks and scientific papers.

In Medical Subject Headings (MeSH), computed axial tomography was used from 1977 to 1979, but the current indexing explicitly includes X-ray in the title.

The term sinogram was introduced by Paul Edholm and Bertil Jacobson in 1975.

Campaigns
In response to increased concern by the public and the ongoing progress of best practices, the Alliance for Radiation Safety in Pediatric Imaging was formed within the Society for Pediatric Radiology. In concert with the American Society of Radiologic Technologists, the American College of Radiology and the American Association of Physicists in Medicine, the Society for Pediatric Radiology developed and launched the Image Gently Campaign which is designed to maintain high-quality imaging studies while using the lowest doses and best radiation safety practices available on pediatric patients. This initiative has been endorsed and applied by a growing list of various professional medical organizations around the world and has received support and assistance from companies that manufacture equipment used in Radiology.

Following upon the success of the Image Gently campaign, the American College of Radiology, the Radiological Society of North America, the American Association of Physicists in Medicine and the American Society of Radiologic Technologists have launched a similar campaign to address this issue in the adult population called Image Wisely.

The World Health Organization and International Atomic Energy Agency (IAEA) of the United Nations have also been working in this area and have ongoing projects designed to broaden best practices and lower patient radiation dose.

Prevalence
Use of CT has increased dramatically over the last two decades. An estimated 72 million scans were performed in the United States in 2007, accounting for close to half of the total per-capita dose rate from radiologic and nuclear medicine procedures. Of the CT scans, six to eleven percent are done in children, an increase of seven to eightfold from 1980. Similar increases have been seen in Europe and Asia. In Calgary, Canada, 12.1% of people who present to the emergency with an urgent complaint received a CT scan, most commonly either of the head or of the abdomen. The percentage who received CT, however, varied markedly by the emergency physician who saw them from 1.8% to 25%. In the emergency department in the United States, CT or MRI imaging is done in 15% of people who present with injuries as of 2007 (up from 6% in 1998).

The increased use of CT scans has been the greatest in two fields: screening of adults (screening CT of the lung in smokers, virtual colonoscopy, CT cardiac screening, and whole-body CT in asymptomatic patients) and CT imaging of children. Shortening of the scanning time to around 1 second, eliminating the strict need for the subject to remain still or be sedated, is one of the main reasons for the large increase in the pediatric population (especially for the diagnosis of appendicitis). As of 2007, in the United States a proportion of CT scans are performed unnecessarily. Some estimates place this number at 30%. There are a number of reasons for this including: legal concerns, financial incentives, and desire by the public. For example, some healthy people avidly pay to receive full-body CT scans as screening. In that case, it is not at all clear that the benefits outweigh the risks and costs. Deciding whether and how to treat incidentalomas is complex, radiation exposure is not negligible, and the money for the scans involves opportunity cost.

Manufacturers
Major manufacturers of CT scanning devices and equipment are:

 * 🇺🇸 GE Healthcare
 * 🇩🇪 Siemens Healthineers
 * 🇯🇵 Canon Medical Systems Corporation (formerly Toshiba Medical Systems)
 * 🇳🇱 Koninklijke Philips N.V.
 * 🇯🇵 Fujifilm Healthcare (formerly Hitachi Medical Systems)
 * 🇨🇳 Neusoft Medical Systems
 * 🇨🇳 United Imaging

Research
Photon-counting computed tomography is a CT technique currently under development. Typical CT scanners use energy integrating detectors; photons are measured as a voltage on a capacitor which is proportional to the X-rays detected. However, this technique is susceptible to noise and other factors which can affect the linearity of the voltage to X-ray intensity relationship. Photon counting detectors (PCDs) are still affected by noise but it does not change the measured counts of photons. PCDs have several potential advantages, including improving signal (and contrast) to noise ratios, reducing doses, improving spatial resolution, and through use of several energies, distinguishing multiple contrast agents. PCDs have only recently become feasible in CT scanners due to improvements in detector technologies that can cope with the volume and rate of data required. As of February 2016, photon counting CT is in use at three sites. Some early research has found the dose reduction potential of photon counting CT for breast imaging to be very promising. In view of recent findings of high cumulative doses to patients from recurrent CT scans, there has been a push for scanning technologies and techniques that reduce ionising radiation doses to patients to sub-milliSievert (sub-mSv in the literature) levels during the CT scan process, a goal that has been lingering.

title: CT scan


text:
907

Year 907 (CMVII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar.

Byzantine Empire

 * Rus'–Byzantine War: Varangian prince Oleg of Novgorod leads the Kievan Rus' in a campaign against Constantinople, concluded by the Rus'–Byzantine Treaty (in which the city of Chernihiv in Ukraine is first mentioned). He lays siege to the Byzantine capital with some 2,000 ships (dugout boats), and secures trading rights from the world's leading center of commerce.

Europe

 * July 4–6 – Battle of Pressburg: At "Brezalauspurc" (probably modern-day Bratislava in Slovakia), the advancing East Frankish army (60,000 men) is annihilated by the Hungarians led by Grand Prince Árpád. Duke Luitpold and Archbishop Dietmar I are killed, together with 19 dukes, 2 bishops and 3 abbots. The East Frankish Kingdom loses control of the March of Pannonia.
 * Summer – The Hungarians invade Bavaria, causing great destruction, occupying many towns and, on their way home, defeating a Bavarian army at Lengenfeld. The Hungarian-Bavarian border is fixed on the Enns River.

Britain

 * Lady Æthelflæd of Mercia refortifies Chester against Viking attacks. King Edward the Elder founds Romsey Abbey (Hampshire).

Arabian Empire

 * Emir Isma'il ibn Ahmad dies after a 15-year reign in which he has extended his borders to Tabaristan and Khorasan. He establishes independence throughout the eastern part of his empire from his capital at Bukhara. Isma'il is succeeded by his son Ahmad Samani as ruler of the Samanid Empire.

China

 * The Five Dynasties and Ten Kingdoms period begins in China.
 * February 27 – Abaoji, ruler (khagan) of the confederation of Khitans, proclaims himself emperor and establishes the Liao dynasty, killing most of the other Khitan chieftains. He occupies territories along China's northern border including parts of Hebei and Shanxi provinces.
 * May 12
 * The short-lived Qi Kingdom is founded by the warlord Li Maozhen (Prince of Qi). His power is centered in Shaanxi province, in Northwest China. The Tang dynasty comes to an end after 289 years as Emperor Ai is forced to abdicate by chancellor Zhu Quanzhong.
 * The short-lived Wu Kingdom is founded by Yang Wo (Prince of Hongnong) in Jiangdu (South Central China). He refuses to acknowledge the rule of Zhu Quanzhong.
 * June 1 – Zhu Quanzhong (Zhu Wen) usurps the throne and proclaims himself the first emperor of Later Liang. China is controlled by successive short-lived kingdoms (until 960).
 * June 8 – The Chu Kingdom is founded by the warlord Ma Yin (Prince of Chu) in Changsha. Present-day Hunan and Guangxi provinces (Southern China) are under his control.
 * November 3 – The Former Shu Kingdom is founded by the warlord Wang Jian (Prince of Shu) in Chengdu. His power is centered in Sichuan province, in Southwest China.
 * December 1 – The Wuyue Kingdom is founded by the warlord Qian Liu in Hangzhou. His proclaims himself king, his power is centered in Jiangsu province (Eastern China).

Religion

 * February 1 – Nicholas I Mystikos is deposed as Patriarch of Constanstinople, (having fallen out with the Byzantine Emperor Leo VI), and is replaced by Euthymius I Syncellus.

Births

 * November 26 – Rudesind, Galician bishop (d. 977)
 * Bertha of Swabia, Frankish queen (approximate date)
 * Robert of Vermandois, Frankish nobleman (approximate date)
 * Wenceslaus I, duke of Bohemia (approximate date) (k. 935)

Deaths

 * May 2 – Boris I, ruler (knyaz) of the Bulgarian Empire
 * July 4
 * Dietmar I, archbishop of Salzburg
 * Luitpold, margrave of Bavaria
 * Alan I, duke ('king') of Brittany
 * Árpád, Grand Prince of the Hungarians (approximate date)
 * Herbert I, Frankish nobleman
 * Isma'il ibn Ahmad, emir of the Samanid Empire
 * Radelchis II, Lombard prince
 * Rudesind I, bishop of Dumium (Spain)

title: 907