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The International Congress of Radiology (ICR) is a meeting of radiologists for the exchange of ideas and the harmonisation of international standards and practice, first held in 1925 in London and held at regular intervals since then. Since 1994 it has become a biennial event. Until 1953 each congress was organised by radiological society of the host country, but in that year, a formal organisation, the International SOciuety for Rodiology was set up to provide continuity between the congresses.

At the second congress, held in 1928 in Stockholm, three international commissions were set up - the International Commission for Radiological Protection (ICRP), the International Commission for Radiological Units (ICRU) and the International Commission for Radiological Education (ICRE). The latter two have become fully functional organisations in their own right while the latter has remained a sub-committee of the ICR.

International Congress of Radiology[edit]

Within years of Röntgen discovering X-Rays in 1896, they were being used for imaging fractured bones. Various societies sprung up in different countries where ideas were exchanged between like-minded people and national standards for the measurement of X-Ray intensity developed. These societies also tried to address the problems associated with the dangers of X-Rays, particularly cancer.

By the end of the First World War a number of proposals on how to measure the intensity of X-Rays had been made, but there was little agreement between the various parties concerend.[1] In 1925 the British Institute of Radiology, under the leadership of Thurstan Holland[2][3] invited delegates from a number of countries to attend the First International Congress on Radiation in London. This congress set up a framework for future meetings - future congresses would meet every three years in a different country, would be organised by the host country. The host country would nominate the chairman of the congress. It was also established that three commissions should be set up which would meet at the congresses:

  • The International Commission of Radiation Units & Measures (ICRU)
  • The International Commission on Radiological Protection (ICRP)
  • The International Commission on Radiological Education (ICRE)

Until the outbreak of the Second World War, congresses were held every three years. The 1940 congress was due to meet in Berlin in 1940, but was suspended due to the war. Apart from some copies of records kept by the 1973 Congress secretary-general, Benjamin Orndoff, the records of the congresss, which had been handed to the German organisers in preparation for the next congress in Germany, were lost during the Second World War.[4]

The second congress was held in Stockholm under the chairmanship of Manne Siegbahn where the three commissions proposed in London met for the first time. Subsequent meetings were held in Paris (1931), Zurich (1934) and Chicago (1937).

After the war, the British Institute of Radiology organised the sixth Congress which was held in London, exactly 25 years after the first congress and in the same hall as the first congress. A total of 3364 people from 54 countries including 1,742 radiologists registered for the congress.[5] The incumbent chairman of the ICR, Arthur C. Christie, who had been nominated thirteen years previously was unable to attend the London conference, so Orndoff, the secretary-general of that congress deputised handing the presidency to Ralston Paterson. The congress also saw a resumption of the work of the three international commissions.

At the seventh congress, held in Copenhagen in 1953, the organisational details of the conference were overhauled and an executive committee under the chairmanship of Lauriston S Taylor was set up to ovesee the organisation of future congresses and to provide continuity between congresses.

Before the Second world war, the location of the congresses was dictated largely by the places of residence of the delegates who had to travel by rail or sea - a delegate from the westermn seaboard of the United States would have to commit a month to attend a week-long ICR congress in Europe. The advent of air travel removed this restriction and subsequent congresses have since been held in many parts of the world. The following congresses have been held to date (or are scheduled):[4][6]

International Society of Radiology[edit]

The 1950 congress provided an occasion for workers in the radiology industry to meet for the first time in over a decade and to discuss the direction future congresses should take. At the 1953 congress, under the guidance of Flemming Norgaard in Copenhagen the International Society of Radiology was set up to oversee the organisation of the International Congresses of Radiology rather than the ad hoc arrangement whereby the organisation of the next congress was left entirely in the hands of the host country. A permanent committee would also provide continuity between congresses. Norgard became the first secretary-general of the Society, but as a gesture to the host country, the first president of the ISR was the chairman of the organising committee of the Copenhagen ICR.[7]

After World War II, the congresses resumed where they began, in London in 1950. By now, a very few delegates braved international air travel which was beginning to replace more leisurely trains and ships. The program featured presentations of advances drawn from scientific discoveries born in wartime needs. Much was said about new megavoltage sources of x-rays and other radiation forms for cancer treatment. The cornucopia of artificial isotopes from cyclotrons and reactors promised new dimensions in organ imaging and targeted radiation treatment. After a wartime hiatus, the international commissions resumed their activities agreeing to meet in 1953.

By 1953, when the congress met in Copenhagen, there was general agreement that the ad hoc arrangement by which national sponsors passed along the burden of meetings was not satisfactory. With the leadership of Flemming Norgaard, the International Society of Radiology came into being. Bylaws were drawn up, working committees in education and meeting planning were organized, national society dues were set. Dr. Norgaard agreed to serve as the society's first secretary-general. The radiologist from the sponsoring society who had been president of a congress was, by that token, president of the ISR until the next meeting. A small executive committee was created. The president of the organizing group for the next congress was then president-elect of the international society and would become president when his congress occurred.

ISR - registered in Illinois

The International Congress of Radiology is a bi-annual convention of radiologists. [1] - Intro to early days by US agency

web page for virtual congress [2]

International Commission of Radiation Units & Measures[edit]

The International Commission on Radiation Units and Measurements (ICRU) is a standardization body set up in 1925 by the International Congress of Radiology, originally as the X-Ray Unit Commmittee until 1950. Its objective "is to develop concepts, definitions and recommendations for the use of quantities and their units for ionizing radiation and its interaction with matter, in particular with respect to the biological effects induced by radiation".[8] During the first two decades of its existance, its formal meetings were held during the International Congress of Radiology, but from 1950 onwards, when its mandate was extended, it has met annually.

A hand-held gieger counter used for detecting radioactivity.

Until 1953, the president of the ICRU was a national of the country that was hosting the ICR, but in that yeat it was decided to elect a permanent commission - the first permanent chairman being Laurent Taylor who had been a member of the commission since 1928 and secretary since 1934. Taylor served until 1969 and on his retirement was accorded the position of honorary chairman which we held until his death in 2004, aged 102.[9]

The commission has a maximum fifteen members who serve for four years and who, since 1950, have been nominated by the incumbent commissioners. Members are selected for their scientific ability and is widely regarded as the foremost panel of experts in radiation medicine and in the other fields of ICRU endeavor. The commission is funded by the sale of reports, by grants from the European Commission, the US National Cancer Institute and the International Atomic Energy Agency and indirectly by organisations and companies who provide meeting venues. Commissioners, many of whom have full time university or research centre appointments, have their expenses reimbursed, but otherwise they receive no remuneration from the ICRU.

In the late 1950's the ICRU was invited by the CGPM to join other scientific bodies to work with the International Committee for Weights and Measures (CIPM) in the development of a system of units that could be used consistently over many disciplines. This body, initially known as the "Commission for the System of Units" (renamed in 1964 as the "Consultative Committee for Units") was responsible overseeing the development of the International System of Units (SI).[10]

In the late 1950's the ICRU started publishing reports on an irregular basis - on average two to three a year. In 2001 the publication cycle was regularised and reports are now published bi-annually under the banner "Journal of the ICRU".[11][12]

The commission has been responsible for defining and introducing the following units of measure on behalf of the industry. The number of different units for various quantities is indicative of changes of thinking in world metrology, especially the movement from cgs to SI units.[13]

Quantity Name Symbol Unit Year
Exposure (X) röntgen R esu / 0.001293 g of air 1928
Absorbed dose (D) erg•g-1 1950
rad rad 100 erg•g-1 1953
gray Gy J•kg-1 1974
Activity (A) curie c 3.7 × 1010 s-1 1953
bequerrel Bq s-1 1974
Dose equivalent (H) röntgen equivalent man rem 100 erg•g-1 1971
sievert Sv J•kg-1 1977
Fluence (Φ) (reciprocal area) cm-2 or m-2 1962

The Commission's secretariat is in Stockholm and its legal status is that of of British charity (Not-for-profit organisation).

International Commission on Radiological Protection[edit]

The International Commission on Radiological Protection (ICRP) is an advisory body providing recommendations and guidance on radiation protection; It was founded in 1928 at the second International Congress of Radiology (ICR) and was then called the International X-ray and Radium Protection Committee (IXRPC).[14]

Also established 1928 ( This reference has a good overview of structures - pg 29/30

Summary safety report

Then it was restructured to better take account of uses of radiation outside the medical area, and given its present name, in 1950. ICRP is a not-for-profit organisation in the United Kingdom and currently has its scientific secretariat in Ottawa, Canada.

The ICRP defined the reference man in 1974.


Budget $375,000 Scientific secretariat located at Swedish Radiation Protection Authority

The Swedish Radiation Protection Authority and the Radiation Protection Division of the UK Health Protection Agency (formerly the National Radiological Protection Board) both provide fully serviced offices, free of charge, for the Commission. In addition, the Swedish Radiation Protection Authority provides the services of 50% of a full-time secretarial assistant, and support to cover office expenses and incidentals. The value of the latter donated services is estimated to be in the range of US$ 12,500 per annum, although it is difficult to quantify a precise amount.

Membership of the Commission or one of its Committees is highly coveted and regarded widely as a great honour for the members as well as for their organisations/employers (which support ICRP by making the members’ time available without charge, often also contribute to their costs of attending meetings, and in many cases provide substantial additional resources without charge to the Commission). Thus, the problem is not to find candidates but to select the right ones. In addition to the obvious primary requirement,internationally acknowledged top level expertise, the Commission is working actively to ensure ethnic and gender diversity.

International Commission on Radiological Education[edit]

The International Commission for Radiological Education was the third of the three commissions established in 1928 at the second ICR. Its early records appear to have been lost during the Second World War. It under the auspices of the International Congress of Radiology and is funded by the International Society for Radiology. The commission's mandate is to coordinate the activities of radiologists in the field of education and to investigate educational standards and facilites in all countries in respect of radiological subjects.[16] .

External links[edit]

Sugested pictures

file Electron capture NT.PNG
Subaquatic radiographytext


One gray is the absorption of one joule of energy, in the form of ionizing radiation, per kilogram of matter.

For xrays and gamma rays, these are the same units as the sievert (Sv). For alpha particles one gray is twenty sievert. To avoid any risk of confusion between the absorbed dose (by matter) and the equivalent dose (by biological tissues), one must use the corresponding special units, gray is used instead of the joule per kilogram for absorbed dose and the sievert instead of the joule per kilogram for the dose equivalent. The word "gray" is both the singular and plural spelling.

The gray was defined in 1975 in honour of Louis Harold Gray (1905–1965) who, in 1940, first proposed a similar concept, "that amount of neutron radiation which produces an increment of energy in unit volume of tissue equal to the increment of energy produced in unit volume of water by one röntgen of radiation".[17]

This SI unit is named after Louis Harold Gray. As with every International System of Units (SI) unit named for a person, the first letter of its symbol is upper case (Gy). However, when an SI unit is spelled out in English, it should always begin with a lower case letter (gray)—except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.— Based on The International System of Units, section 5.2.

Leading up to the gray[edit]

Wilhelm Röntgen first discovered X-Rays in 1896 and within a few years they were being used to examine broken bones. One of the earliest techniques of measuring the intensity of X-Rays was to measure their ionisation potential in air. Initially various countries developed their own standards, but in order to promote international cooperation, the International Commission on Radiation Units and Measurements (ICRU), first proposed as a separate body in 1925, met in Stockholm in 1928 and under the chairmanship of Rolf Sievert[Note 1] proposed that one unit X-Ray dose should be defined as the quanitity of X-rays that would produce one esu of charge in one cubic centimetre of dry air at 0 °C and a standard atmosphere. This unit was named the röntgen in honour of Röntgen who had died five years previously. At the 1937 meeting of the ICRU, this definition was extended to apply to gamma radiation as well as X-Rays.[1] This technique, although appropriate for the technology of the day, had the disadvantage that it was not a direct measure of either the intensity X-rays or of their absorbtion, but rather was a measurement of the effect of the X-Rays in a specific circumstance.[18]

In 1940, Gray, who had been studying the effect of neutron damage on human tissue, together with Mayneord and Read published a paper in which a unit of measure, dubbed the "gram roentgen" (symbol: gr) defined as "that amount of neutron radiation which produces an increment in energy in unit volume of tissue equal to the increment of energy produced in unit volume of water by one rontgen of radiation"[17] was proposed. This unit was found to be equivalent to 88 ergs/cm3 in air. In 1953 the ICRU adopted the "rem", equal to 100 erg/g as the new unit of measure of absorbed radiation. The rem was directly equivalent to the gram roentgen, but expressed in coherent cgs units.[1]

At the same time is was becoming increasingly obvious that the definition of the roentgen was unsound and many calls were made for its redefintion. In 1962 it was redefined[19] as 0.258 mC/kg. The definition of the roentgen had the advantage over the gray of being simpler to measure, but the gray is independent of the primary ioniying radiation[20]. Although of importance in biological work, the gray difficult to measure directly, but can be done by measuring the kerma (kinetic energy release per unit mass) as all energy appears as thermal energy, but in practice increases in temperature are small.[20]


  1. ^ The chairman of the ICRU meetings was a national of the country hosting the meeting


  1. ^ a b c Guill, JH; Moteff, John (June 1960). "Dosimetry in Europe and the USSR". Third Pacific Area Meeting Papers - Materials in Nuclear Applications - American Society Technical Publication No 276. Symposium on Radiation Effects and Dosimetry - Third Pacific Area Meeting American Society for Testing Materials, October 1959, San Francisco, 12-16 October 1959. Baltimore: ASTM International. p. 64. LCCN 60-14734. Retrieved 15 May 2012.  line feed character in |booktitle= at position 74 (help) Cite error: Invalid <ref> tag; name "GM" defined multiple times with different content (see the help page).
  2. ^ Shanks, S. Cochrane (1950). "The Sixth International Congress". British Journal of Radiology. British Institute of Radiology. Retrieved 23 May 2012.  Unknown parameter |no= ignored (help)
  3. ^ Cary, Austin (May 2011). "Charles Thurstan Holland:Pioneer of Liverpool Radiology" (PDF). The Invisible Light: The Journal of The Radiology History and Heritage Charitable Trust: 20. Retrieved 23 May 2012.  Unknown parameter |no= ignored (help)
  4. ^ a b Linton, Otha W. "History". International Society of Radiology. Retrieved 25 May 2012. 
  5. ^ "The Sixth International Congress of Radiology". Radiological Society of North America, Inc. 1950. Retrieved 25 May 2012. 
  6. ^ Newsletter (PDF). International Society of Radiology. September 2011 Retrieved 22-May-2012.  Check date values in: |access-date= (help); Missing or empty |title= (help)
  7. ^ Linton, Otha W. "History". ISR website. Bethseda, Maryland: International Society of Radiology. Retrieved 30 June 2012. 
  8. ^ Wambersie, A; Menzel, HG (26–30 August 2002). The ICRU: General Objectives and Achievments with regard to Occupational Radiation Protection (PDF). Occupational Radiation Protection: Protecting workers against exposure to ionising radiation. pp. 99 – 110. Retrieved 31 May 2012.  Unknown parameter |locatio= ignored (help)
  9. ^ "Emeritus and founder member L S Taylor dies". International Commission on Radiological Protection. 1 December 2004. Retrieved 18 June 2012. 
  10. ^ "CCU: Consultative Committee for Units". International Bureau of Weights and Measures (BIPM). Retrieved 18 May 2012. 
  11. ^ "Reports". International Commission on Radiation Units and Measurements. Retrieved 3 June 2012. 
  12. ^ "Journal of the ICRU". Oxford University Press. 2012. Retrieved 3 June 2012. 
  13. ^ "International Commission on Radiation Units and Measurements" (PDF). International Commission on Radiation Units and Measurements. 14 March 2012. Retrieved 1 June 2012. 
  14. ^ Clarke, R.H.; and J. Valentin (2009). "The History of ICRP and the Evolution of its Policies" (PDF). Annals of the ICRP. ICRP Publication 109. 39 (1): pp. 75–110. doi:10.1016/j.icrp.2009.07.009. Retrieved 12 May 2012.  Cite uses deprecated parameter |coauthors= (help)
  15. ^ "International Commission on Radiological Protection: Report and Accounts for the year ended 31 December 2006" (PDF). [British] Charity Commissioners. 15 October 2007. Retrieved 3 June 2012. 
  16. ^ "International COmmission for Radiological Education and Information (I.C.R.E)". Australasian Radiology. 15 (1): 6 – 15. February 1971. Retrieved 1 June 2012. 
  17. ^ a b Gupta, S. V. (2009-11-19). "Louis Harold Gray". Units of Measurement: Past, Present and Future : International System of Units. Springer. p. 144. ISBN 978-3-642-00737-8. Retrieved 2012-05-14. 
  18. ^ Lovell, S (1979). An introduction to Radiation Dosimetry. Cambridge, United Kingdom: Cambridge University Press. pp. 52 – 64. ISBN 0 521 22436 5. Retrieved 15 May 2012.  More than one of |at= and |pages= specified (help)
  19. ^ Anderson, Pauline C. The Dental Assistant (7th ed.). Albany, NY: Delmar. p. 554. ISBN 0-7668-1113-1.  Unknown parameter |last 2= ignored (help); |first2= missing |last2= in Authors list (help); More than one of |at= and |page= specified (help)
  20. ^ a b Lovell, S (1979). An introduction to Radiation Dosimetry. Cambridge, United Kingdom: Cambridge University Press. pp. 43 – 51. ISBN 0 521 22436 5. Retrieved 15 May 2012.  More than one of |at= and |pages= specified (help)