III.高線量率腔内照射時における直腸膀胱線量の測定(高線量率腔内治療時の技術的諸問題)

抄録

In the radiotherapy by a remote-afterloading method of cervix cancer, rectum and urinary bladder are the main portions of after effects of radiation. Therefore, in order to prevent the effects in advance, it is important to acquire the applied dose at rectum and at urinary bladder for each clinical case. At the same time the strict concerns for the radiotherapy are requied. In the dosimetry methods of rectum and urinary bladder, there are the methods which use an ionization-chamber type dosimeter, a semiconductor type dosimeter, of a thermo-fluorescency type dosimeter and the method using a computer. Since the early period of therapy activitied, the dose measurement of rectum and bladder has been carried out at this Osaka university hospital. In the remoteafte-rloading method, the overriding method for five steps is applied as the source inside uterus. Therefore, the measured value of dose is the cumulative value, and many measuring points are requested. From the measured dose and the calculated dose values by a computer, it is revealed that the dose at rectum is 70% of point A in average, and that the dose at bladder is 80% point A in average. In the actual dosimetry of rectum and urinary bladder, the following advantageous points are raised : 1. The direct reading is possible for the intra-cavity dose of rectum and urinary bladder. 2. The measured values work as the mean to confirm the calculation by a computer. 3. It can prevent the troubles which might occur during the exposure time. 4. It is effectively used for evaluation of the applied dose at point A. 5. It is effectively used for the analysis of after effects of radiation therapy. Therefore, it is recommendable to do the measurements for each clinical case. And these measurements lead to the prevention against the effects.