イリョウ ヒバク ノ ゲンジョウ
Current topics on radiation exposure to patients (medical exposure)
medical radiation exposure
X-ray-induced skin injury
Interventional radiology （fluoroscopically-guided） techniques are being used by an increasing number of clinicians not adequately trained in radiation safety or radiobiology. In 1994, Food and Drug Administration of the United States first gave warning to the risk of serious X-ray-induced skin injuries including intractable ulcers among patients who received fluoroscopically-guided procedures. The Japan Radiological Society reacted promptly, and gave a warning in 1995, and the first report on radiation skin injury during prolonged fluoroscopy in Japan appeared in 1998 on a dermatological journal. Since then many cases have been reported on dermatological journals. Radiation skin injuries occurred mainly during cardiac studies, but cases of abdominal studies also have been reported. Recently there was a case report of skin malignancy in a long standing radiation induced ulcer. The international commission on radiation protection published“Publication 85 Avoidance of Radiation Injuries from Medical Interventional Procedures”in 2000. This document can be summarized in the following three major points : 1）The risk of radiation injury should be explained to the patient prior to IVR （informed consent. 2） Protocols should be prepared to define the number of images to be taken and the fluoroscopy time for each procedure of IVR so that standard radiation doses can be calculated. 3） If the cumulative absorbed dose to the patient’s skin exceeds 3 Gy （1 Gy for procedures likely to be repeated）, the site and dose of radiation given should be recorded in the patient’s record. If the dose is more than 3 Gy, the patient should be followed up 10 to 14 days after the procedure.
It is very important to measure the cumulative absorbed dose of the skin, but very difficult. We developed a very reliable system for the measurement using a self-developing reflecting-type sheet film and reported their usefulness.
CT examinations also have been increasing dramatically in Japan. There was a report of estimation of possible risk of cancer after CT examination based on a hypothesis. Although there has been no evidence of real risk of low dose radiation exposure such as CT reported, we should try to use CT appropriately. Especially we must try to reduce CT dose to children or young adults, because they are more sensitive to radiation and live longer than adults.
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