The present study aims at applying the theory of entropy to evaluating radiographic images in psychological sense, and based on the degree of uncertainty, "perception" can be introduced in evaluating such images. As a result, it has become possible to quantitatively evaluate it in terms of the transmitted information obtained from observers. The transmitted information obtained from the skull radiograms was greatest in the case of radiologic technologists, follwed by neurosurgeons and nonprofessionals. The degree of agreement of rating among observers and of rating in two repeated observations were higher with respect to radiologic technologists.
In october 1975,the first home manufactured CT unit (Hitachi) was installed in our university hospital. Since that time several methods how to set a level of scan in CT examination were investigated and reported by us. At first we discussed on the slit scanography which was used to determine a most adequated level for the examination of CT scanner. After that, two dimensional image, reconstructed from the data of CT detector, was introduced into clinical use, and some CT unit, ie. Scoutview of GE CT/T 8800 and others, has adopted at present these methods, which we called a "Computed Radiography" (CR) system. To improve the quality of the CR image and to find a new radiological technique by CT for clinical applications, efforts were made in our hospital. The conclusions obtained are as follows ; Advantages 1. As far the digital data are accumlated and memorized in this system, CR image can be modified in many way and be displayed on the CRT. The contrast resolution of the system are as well superior than that of the conventional radiography. 2. As the lineality of the detector sensitivity is superior to the conventional screen film system, quantitative analysis of the image can be practiced. 3. The CR image enables to confirm the level of the scan without moving the patient to another table. In addition of gantry inclination as well as swing angle of the CT table can easily be measured. 4. The X Ray dose of CR system reduces to 1/5 in comparison with the routine X Ray radiography of the skull and the abdomen. Disadvantage 1. The conspicuous disadvantage of the CT image comparared with the conventional X-ray radiography is an insufficient ability in spatial resolution which, however, will be solved in near future.
About 1,500 cases of gynechological cancer have been treated using high dose rate interacavitary irradiation since 1968 up to the present at NIRS-hospital. Five year crude survival rates of intact cervix cancer in each stages were 85.9% (67/78) in stage 1,69.3% (95/137) in stage 2,54.4% (112/206) in stage 3 and 20% (12/60) in stage 4 respectively. Incidence of moderate radiation complications in high dose intracavitary irradiation were 6.2% on rectum and 4.4% on urinary bladder respectively, however, there was no difference with that of in low dose rate intracavitary irradiation. The optimal dose to point A' were estimated as 2,900 rad in high dose rate intracavitary irradiation and 5,000 rad in low dose rate one, so the dose rate effect was 1.7. The merit or demerit of high dose rate irradiations was disscussed.
Recently remotely controlled high dose rate brachytherapy apparatus is diffusing rapidly. We can irradiate several hundreds rad in a few minutes by appling this equipment. Therefore a slight error of irradiation time produce decrease of cure rate or increase of radiation injury. So it is necessary to compute the dose and dose distribution with accuracy and speedy before treatment. In this paper, we investigated technical problems in the calculation method. 1. There are two method to compute a position of source. The first method is two perpendicular radiography. In this case, we must set X-ray beam angle carefully to get a accurate data. The second is stereoradiography. There is a possibility that error of Z direction rise. Therefore we must measure the place as precisely as possible. 2. The situation of point A is fixed by rotation of co-ordinates or construction. 3. The formulas of dose calculation have been reported by many authers. But we can obtain similar numerical value by using Misberger's, Ponnunni's, Morimoto's formula. 4. Compensation of capsule absorption can be computed using energy absorption coefficient. But gynecological disease, error is so small that it is not necessary to correct capsule absorption. (However, it is influenced by shape of source capsule.) 5. In order to obtain the dose at point A, the simple method is being used. We can compute the point A dose from tandem source using distance between ring and tandem source, and tandem intensity. The dose at point A from ovoid source is calculated using a chart method or distance between point A and ovoid source. We could obtain the dose at point A within 10% error by using these method. 6. The value of dose rate is most essential quantity in dose calculation. So we must measure it accurately. 7. In over-ride system, tandem source moves slowly. Therefore it is necessary to compensate moving time. 8. Moving distance of tandem source ought to be lesser than 1.5cm. Further more, we examined the relation among intensity of sources, ovoid space and distance between tandem and ovoid source.
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.
The important factors to use remote afterloading system (RALS) are to calculated the correct radiation dose distribution, to deliver the exact dose to point A, to minimize the radiation injury, and to operate the cycling source with safety and accuracy. Therefore, we need to have excelent method for radiotherapy and perfect system for the safety. The next steps are as follows, (1) Equipment and staff (Radiotherapist, Radiophysicist, Radiotechnologist). (2) Safety care and exposure dose. (3) Training program and educational system from the international point of view.
Enploying a small amount of Radium-226 or Cesium-137 source was to be used hitherto for the treatment of carcinoma of the uterine cervix in used After-loading tachniques. It was involves, however, radiation risk to the staff and patient. The long treatment time are also a pain (strain) on the patient. In recent years, we have developed a remote control after-loading unit, which was named as RALSTRON, which was complete eliminated the disadvantage of conventional radium therapy. This unit also has disadvantage, however, that the design for the remote after-loader for intracavitary applicators present considerable difficulties, because many sources of different active lengths and loading patterns are rquired. A solution solution to this problem was caried out by using small point source, placed in Tanden applicator, of high activity and moving them back slowly during the treatment. Recently, this unit was installed many haspitals about 80 units in Japan, and are used. In this paper are given about an mechanism and safety devices of this unit.