The serial large-field angiography is undoubtedly useful in the roentgenographic evaluation on the vascular diseases involving systemically throughout the body or lower extremity. The large-field angiography has been routinely performed in the arterial or venous ailments of the extremities in our Department of Radiology since 1965,using a long cassette (90×25cm) holding a differential intensifying screen for the whole-limb angiography. A new automatic roll-film changer for the large-field angiography was constructed by Dr.Suzuki (Director of our Department) in 1977. The changer is equipped with a combination of intensifying screens (90×25cm) for the whole-limb angiography and a 90×25cm stationary grid. The program of film changing can be set at 1 exposure per 1,2,3,4 or 5 second period on the program selector, and a total of 20 serial angiograms can be obtained. In addition to results on basic experiment, some of clinical experience on the changer is presented.
In the simultaneous bi-plane system, one of the most important problems is the deterioration of radiographic image quality by the scattered X-rays from many direction. We met with good results by using the rare earth substance for the sake of deteriorating the side scattered X-rays. Then we compared the effects of elimination of the side scattered X-rays by using aluminum with that by using some rare earth substance and studied by X-ray spectrum theoretically. From the above-mentioned things, we got the best effect when the absorption edge of rare earth substance agreed with the region of energy of the side scattered X-rays.
An attempt has been made to develop heavy atom containing transparent plastic filters which are identical with conventional aluminum or copper filters in X-ray attenuating property. These transparent filters can be used as fixed at the front of a conventional multilayer collimator without obstructing the optical detection of the field size of X-ray exposure. It has become a serious problem that recent increasing use of X-ray in diagnostics, namely increasing patient exposure, may cause baneful influence upon the patients. To reduce such patient exposure, the I.C.R.P. has recommended the proper use of metal filters made of aluminum or copper with regards to the applied tube potential. These filters are generally used as fixed at the X-ray tube window or used at the front of a multilayer collimator as added filters. In the former case, an exchange of filters to select the best one with regards to the applied tube potential needs complicated works, and in the latter, the use of the added filters also needs complicated works to confirm field size before each radiography. These troublesome works have at times resulted in improper uses of the filters although the effective selection of filters is known to be useful to the reduction of patient exposure. Therefore, the problem of reduction of patient exposure by means of filtration still remains practically unsolved. To offer practical added filters which do not possess above mentioned disadvantages of metal filters, we tried to develop transparent added filters. Transparent plastics as the material of the filters were loaded with heavy atoms to equalize X-ray attenuating property with aluminum or copper.
This irradiation unit was designed for γ-ray irradiation of thermoluminescence dosimeters (TLD) used for personnel or environmental monitoring. In view of the variabilities involved in the measurements due to the kind of phosphors, direction of beam etc., a rotary type irradiation was used in order to minimize the variation and to actuallize the working conditions, performance of the unit can be summarized as follows. 1. Each of ten TLD is set on the shaft of each of ten pulse timing motors which is driven under the following conditions : P.V. 100Volts, 10mA, 50Hz, 20RPM. 2. These motors were proved for continuous driving for over one year, so that a long time continuous irradiation is possible. (Present use is from one day to four weeks.) 3. Each TL element (i.e. the position of motor shaft) is set concentric to the position of a radiation source (^<226>Ra 107μg), and the distance from the source can be changed freely from 130 to 20cm. 4. Fitting and removal of the radiation source to and from the unit can be made conveniently. The results of testing, this rotary type γ-irradiator proved satisfactory the unit can be used effectively for TLD examinations.
The purpose of this paper is to present a description of a proposal of the segment method, its use and its performance. When film is used for the recording system, the trucation error is caused by its nonlinearity inevitably. This truncation error may be decreased by the slit multiple exposure technique. However, the method by which LSF can be measured more simply and exactly than the slit method is required. We designed the segment method in place of the slit method. Except that the X-ray intensity distribution obtained by the slit method is plus and the intensity distribution by the segment method is minus, both distributions are equivalent. It was found that LSF of the slit method corrected with the multiple exposure technique agrees with that of the segment single exposure method. This new method is available for LSF measurement with film.
In recent year, X-ray photographs can be obtained by very low dose with high sensitivity photographic system. Such very low dose makes the image quality inferior because of the fluctuation of x-ray quanta so called "quantum noise". The prosess of the x-ray image formation was evaluated from a point of view that the x-ray images are formed by the accumulation of x-ray quanta distributed randomly. And the condition that the image of a simple-shaped small object can be recognized into background quanta was investigated. Under the assumption that the quanta absorbed by an object are N_s and that the average number of background quanta per area which is in the same projected area of the object is N_b, the condition that N_s is recognizable in background is mathematically led to the following formula : [numerical formula] Then the validity of this formula was experimentally shown using a computer and a simulation system by a gammacamera.
In the courses of radiation therapy, the Energy Imparted to an interested volume in the irradiated body is an important value, as well as that to the whole irradiated body, which suggests possible reactions due to irradiations. In this report, the Energy Imparted for 60-Co gamma rays was calculated based on following two components ; 1) The ratio of the energy quantities which are absorbed in a flat layer perpendicular to incident beam, to the energy quantities which are entered into whole irradiated volume. 2) The ratio of the energy quantities which are absorbed in an interested area of the layer, to the energy quantities which are absorbed in whole area of the layer. The ratio 1) was calculated theoretically, and the ratio 2) was obtained by applying the simulated equations to the Decrement Value, which was derived from the values actually measured. As results, the value of the Energy Imparted calculated theoretically showed a good correspondence to the values obtained from isodose curves, which were measured actually for 60-Co gamma ray irradiations.
CT image of CT-1010 is limited because of many artifacts induced in taking a photograph of the posterior cranial fossa. We have experimented and discussed these artifacts. As a result, the following ones are recognized. 1. the band-like artifacts between both petrous portions 2. the retroclival artifacts 3. the radiated artifacts around internal occipital protuberance 4. the ring-like artifacts in the posterior fossa 5. the apical artifacts 6. Other artifacts-pseudocortex artifacts and overshadowing-produced artifacts-are also shown. We have advocated that a trial of decreasing the artifacts would be acquired by scanning of more high angle to Reid's base line.
A questionnaire about X-ray generators and X-ray tubes was issued to the nation wide members of the JSRT by Radiography and X-ray Generator Characteristics Study Group. Thirty three answers returned and the percentage was 47. The questions are about hospitals, numbers of generators and their models, power supply, X-ray tubes, the dynamic characteristics of generators and radiographic shortest exposure time, etc. The result shows that they have 159 of 12 peak, 36 of 6 peak, and 325 of 2 peak generators. Three phase 12 and 6 peak generators are doubled in numbers compared with our former survey in 1975. The dynamic characteristics of X-ray generators show less improvement than former one. To solve this problem, both user and manufacturer must pay more attention to the characteristics, technologically in radiography and in the design field.
Explanations were given as to the characteristic of the MIRD Committtee method for estimating the internal radiation doses due to the radioisotope administration, with special emphasis on the comparison with the method described in the ICRP Publication 2. The method evolved in the MIRD pamphlets have actually developed the accuracy of the calculation of the absorbed energy per disintegration of the radionuclide deposited in various organs, and it became more important to evaluate exactly the cumulated activity A^^〜 in the internal organs concerned. Some examples were selected for explaining how the MIRD pamphlets could practically be used, in which the author emphasized that the precise evaluation of the retention function, especially of its long-term components, was quite important for improving the accuracy of the dose assessment. The method for obtaining the "S" value for the organ mass that is different from that of the MIRD phantom was described. The author finally discussed the problem of estimating the mass of each internal organ out of the anthropometrical parameters such as body height and body weight.
It is now generally accepted that clear demonstration of the morphological characteristics of malignant microcalcifications on mammography film is indispensable to obtain precise radiological diagnoses of breast cancer especially in its early stage. Those pathognonic calcifications are actually very minute, their average size are around 0.1mm in diameter. The conventional contact mammography, however, hardly depicts those microcalcifications namely, those smaller than 0.3mm in diameter were usually erazed out mainly because of the geometric blur, of the scattering x-ray and of the quantum mottles of film and intensifying screen. The x-ray exposure doses are another controversial problem in conventional contact mammography especially in the case of mass screening program. They are usually reaching around 1R. of skin dosis per single view of mammography. These high doses of x-ray exposure have been invited by the employment of low sensitivity of recording system which has been employed to avoid unsharpness of mammographic images. The main purpose of this study is to find the appropriate range of characteristics of x-ray to enhance subject contrast of such as breast gland which is consisted of the materials with extremely small x-ray absorption differences each other, and to find the way to eliminate avoidable x-ray scattering to enhance film contrast, as well as to explore the suitable size of focal spot of x-ray tube to be able to clearly demonstrate the majority of the microcalcifications without detrimental geometric blur. Also, some psychological considerations were our concern to increase the diagnostic accuracy rate which can have intimate relationship with the size of the images of microcalcifications. Fortunately, recently available high-speed fine-grain films and rare-earth intensifying screens have been providing us the chance to challenge the study to minimize x-ray exposure doses in mamography ; this circumstance should be added to the study purpose furthermore. The following results were obtained by both fundamental and clinical studies : 1. Magnification power required 2× to 2.5×, to precisely recognize the microcalcifications and other pathognomonic finding of tumor findings of early breast cancer. This range of enlargement technique significantly reduced scattering x-ray to reach films due to "Groedel's effect". 2. The effective focal spot size to be used in the abovely mentioned technique should be smaller than 0.1mm in longest diametert to avoid geometric blur. 3. For standard size of breast, 25kVp was most appropriate tube voltage to produce well contrasted pathognomonic findings. 4. Tungsten anode delivered appreciably ideal quality of x-rays for soft tissue roentgenography. 5. The combination of Lo-D film (Du Pont) and LM screen (Toshiba) showed the best results among other many currently available receptor systems. 6. Target-Film Distance at 70cm was practically most convenient. 7. The skin surface dose in average was 0.43rad. per each projection of mammography. This low range of exposure was made possible by the introduction of high-speed recording system, The graininess of this sort of film and screen was well compensated by the enlargement of images. 8. The clinical diagnosing accuracies significantly improved by the application of this particular technique, especially of the breast and thyroid malignancies.