Warning sounded on overuse of CT scans in Japan

Main Category: Public Health
Article Date: 15 Apr 2004 - 0:00 PDT


A research group of the National Institute of Radiological Sciences, Japan, has found that a person in Japan is annually exposed to three times more radiation than a decade ago due to an increase in computerized tomography (CT) testing, The Yomiuri Shimbun (Japanese Newspaper) learned Wednesday.

The Japan Radiological Society is preparing instructions on how to prevent excessive use of the testing equipment and reduce exposure in light of a report released in January by British researchers that said 3.2 percent of Japanese cancer patients are presumed to have developed the disease as a result of exposure to radiation from radiographic examinations.

The research group of the Chiba-based institute sent questionnaires to about 1,000 medical institutions, randomly selected from about 9,900 institutions owning CT equipment.

The group sought details of CT tests conducted during a specific week in 2000, including how many tests were conducted and on what parts of the body, what voltage levels were used, what the length of patient examinations was and which models of CT equipment were used.

Based on the data collected, the research group estimated the frequency of CT scanning tests and how much radiation each person had been exposed to that year.

According to the group, there are 11,050 CT scanning machines in use (in Japan), twice the number recorded in a 1989 survey.

In 2000, 36.55 million CT tests were conducted and an estimated 290 out of every 1,000 people received CT scanning tests, three times more than in 1989.

According to the survey, the population of Japan was annually exposed to an average of 2.3 milli-sieverts of radiation, almost three times the 0.8 milli-sievert level found in previous research and the equivalent radiation dosage of 115 chest X-rays.

The exposure is equal to the annual average of 2.4 millisieverts of natural radiation.

The group said that about half of the world's CT equipment was owned by medical institutions in Japan, adding, "It is not an exaggeration to say that half of the CT scanning tests practiced around the world are conducted in Japan, too."

In the United States, insurance firms and medical associations regulate the number of CT scanning machines in a specific area. Insurance firms closely study the necessity of each CT test and whether it should be covered by insurance.

However, as there are no laws governing CT scanning in Japan, CT tests tend to be overused.

Sukehiko Koga, head of the Japan Association on Radiological Protection in Medicine, said CT scanning has the advantage of revealing a lot of information about symptoms. "However," he added, "It is important to judge the necessity of each test."

From:
http://www.yomiuri.co.jp/newse/20040415wo71.htm

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