An evaluation of the radiation dose exposed to the patients in diagnosis is one of most important processes from a viewpoint of radiation protection, but its procedure in general is very complicated because a lot of conversion coefficients are required and these depend on diagnostic conditions. A computer program are newly developed in this report for calculating the patient dose and several parameters such as ESD (entrance surface dose) in plain film radiography, AGD (average glandular dose) in the breast, CTDI (computed tomography dose index), CTDIw (weighted CTDI) and DLP (dose length product) for X-ray CT examination. This program can also cope with different conditions in radiodiagnosis as well as the case without experimental data.
We examined a method to easily confirm scattering radiation dose rate in the vicinity of cineradiographic apparatus. As a result of experiment, the following things became clear. 1) Even if irradiation conditions are ddifferent, shape of distribution of scattering radiation dose rate is similar. 2) Even if cineradiographic apparatus is different, shape of distribution of scattering radiation dose rate is similar. 3) The exposure and scattering radiation dose rate have proportionality relation. We calculated scattering radiation dose rate in the vicinity of cineradiographic apparatus by using simple calculation method. A calculation value and measured value were in agreement within 40%. A simple calculation method can be used as teaching materials for education.
Indoor 222Rn concentration was measured using an electrostatic radon monitor of PMT-TEL (Pylon Co.). The variation of radon concentration was compared among three kinds of laboratories: Radioisotope (RI) use, Uranium-use and general use laboratories. The 222Rn concentration observed in RI Center under air conditioning was about 3 Bq/m3 close to the outside 222Rnlevel. The indoor radon level increased up to about 30 Bq/m3after the air conditioning was off. Radon exhalation rate was evaluated from increasing rate of radon concentrations after the air conditioning was stopped. In uranium use laboratories, the radon concentration was 40-70 Bq/m3 due to the storage of uranium compounds (about 12 kg). The negative correlation between radon concentration and atmospheric pressure was obtained when the variations of indoor temperature and relative humidity were small. On the other hand, the radon concentration was 5-15 Bq/m3 in general use laboratories of old 2nd building of Engineering, which had not so well shielded windows. In conclusion, indoor radon concentration in uranium use laboratories and RI center became high after air conditioning was off, and so it is recommended that the ventilation should be operated before entering the uranium use laboratories and RI center with well shielded facilities.
A registration system for radiation workers was newly developed at the University of Tokushima. This system is characterized by using the university network and the web page of the Radioisotope Research Center to print out the registration form and to receive the personal record in the form to our web server. As the result, the database for radiation workers could be constructed easily and simply. And the labor saving of the radiation safety management for the Radioisotope Research Center could be achievable. Developing cost was inexpensive and developing time was very short because of utilizing the commercial soft wares.
Skin absorbed doses due to subcutaneous leakage of radioactive pharmaceuticals were estimated by three calculating methods. The radioactive pharmaceuticals used in calculation were 67Ga-citrate, 99mTc-HMDP, 111In-Cl, 123I-IMP, 131I-Adosterol, 201Tl-Chloride which are used frequently and in large amount in the daily examination. Time taken to remove contamination, range of contamination and ratio of leakage were assumed to be 30 minutes, 10cm2 and 30% respectively. The skin absorbed doses calculated on this assumption were less than the threshold value that is found to cause skin disorders by Yamaguchi method. We confirmed the misprints of ICRU report 56 in the process of this cal-culation.