[en] Although two opposed portals has been used for the treatment of laryngeal cancer, there are some problems such as dermatitis caused by increasing of shooting out dose, or poor centering of the X-ray to the focus of lesion. Therefore we have examined the shape and location of the tumor and the surrounding tissues by computed tomography (CT) and laryngoscopy, and two anterior oblique portals with a wedge-filter was undertaken from the fore-neck. The CT examination has made it possible to understand steroscopy state of the focus of lesion and to get accurate treatment schedule of radiation angle and field according to the individual patients. On the other hand centering of the radiation dose to the focus was improved in two anterior oblique portals method, and the beam dose to the skin was also decreased. This method has enabled us applying the X-ray to the fore neck lesion, independently from the shoulder girdle. (author)

[en] Electron beam therapy has often been used for radiation therapy of carcinomas of the buccal mucosa, though side effects, including stomatitis and dermatitis, are known to exist. We experimented using the additional back scatter and transit with the phantom under a lead plate within the irradiation field, in order to better focus the dose on the target volume moreover, we fabricated a mouthpiece fitted with a lead plate shaped to the target volume, and with respect to the influence of the mouthpiece on stomatitis and dermatitis, obtained good clinical results. (author)

[en] The effectiveness of the extended-cycle process, in which processing time is longer than the manufacturer's recommendation, was investigated using four mammographic films, Konica New CM, Fuji UM-MA HC, Kodak Min-R 2000, and Kodak Min-R M. Fuji UR-2, a double-emulsion film, was used as a control. The sensitometric strips exposed by a sensitometer were processed in different combinations of developing temperatures ranging from 28 to 360degC, processing times from 45 to 210 sec and chemicals, Konica XD-9OC, Fuji RD-S and Kodak RP X-Omat. Those characteristics (average gradient, relative speed, base plus fog) obtained from characteristic curves were evaluated for the different developing temperatures, times and chemicals. Fuji UR-2 was scarcely affected, while mammographic films were greatly affected in the different combinations without an increase in base plus fog. For New CM, UM-MA HC and Min-R M, the average gradient and relative speed increased as developing temperature increased and developing time was extended, but the increases were limited with the combination of 360degC and 210 sec for New CM and UM-MA HC. For Min-R 2000, the average gradient was almost constant, and the relative speed increased like the other three mammographic films. Changes in average gradient and relative speed due to chemical variations showed increases or decreases from 6% to 9% compared with Konica chemical. These results suggested that the extended-cycle process for the above mammographic films has the possibility to contribute to dose reduction and advancement of contrast on mammography. (author)

[en] In the irradiation therapy of a wide local area such as to the retroperitoneal lymph node metastasis of the seminoma or to multiple lung metastasis, a double irradiation from separate two centers to two radiation fields has been used for decreasing the side effect in the patients. However, there have been some difficulties such as non-uniformity of the radiation doses and impossibilities of definite dicision of the whole radiation area by a linacgraphy. Authors have, thus, used an alternate irradiation system by applying X-rays to a half side blocked with a lead plate at the line of the center in the whole radiation area, and then to the another half. This system was compared with the double irradiation system used in general. In alternate irradiation system, spreading of the beam was negligible in the boundary area by blocking with a lead plate at the half line and a considerable uniformity of the radiation doses could obtained with confirmation of the block line. The whole radiation area was also well certified with one X-ray film. This system can be very useful for the wide local radiation. (author)

[en] In the field of radiology, new modalities have been developed and expanded. However, X-ray-based diagnostic imaging remains the main stream. Therefore, radiological technologists must provide dosimetry and other physical data related to radiation exposure. In this report, the basic information presented in our previous reports is supplemented with data regarding the relationships between exposure parameters and dose for inverter-type X-ray generators, which have been widely adopted in recent years. This report also describes the measurement of percentage depth dose. We also conducted a survey of medical facilities in Okayama prefecture to gather data concerning the radiographic parameters used for abdominal examinations, and calculated the patient dose from these data. We tabulated and calculated the patient dose for each hospital. The results showed a wide range of variation. The overall mean values were 0.337 cGy for the surface dose and 0.061 cGy for the dose at a depth of 9 cm. (author)

[en] The decelerator and bolus, which reduce radiant energy in electron beam radiotherapy, were investigated with respect to the interrelation between their quality of material, thickness and position, and the mean energy and depth-dose rate curve pattern. The date obtained indicated that an acryl decelerator fitted to the tube aperture had the disadvantage of entailing bremsstrahlung x-ray intervention as well as increased depth dose. An elastomeric bolus placed on the phantom surface, however, resulted in an increased surface dose and minimal x-ray intervention. When radiation was performed with the phantom surface held apart from the bolus, a build-up phenomenon occurred on the phantom surface with a consequent diminution of surface dose. It was concluded that a bolus is more effective than a decelerator fitted to the tube aperture for attenuation of radiant energy. It is more advantageous to irradiate with the bolus in contact with the skin in cases in which the target is localized in the superficial layer of the skin, and with the bolus apart from the skin in cases in which the target is situated deeper below the skin. (author)

[en] With single-emulsion films like those used in screen/film mammography, if the developing temperature is higher and/or the processing time is longer than recommended (i.e., extended-cycle process), film speed and/or film contrast are effectively increased. However, it can also be expected that radiographic noise will be increased by the extended-cycle process. Therefore, film graininess and radiographic mottle were investigated with standard- and extended-cycle processes in four single-screen/single-emulsion film systems for mammography, the Konica M-150/New CM, Fuji UM MAMMO Fine/UM-MA HC, Kodak Min-R 2000/Min-R 2000, and Kodak Min-R Medium/Min-R M. Investigation was carried out by measurement of the Wiener spectrum (WS). Results showed that the WS of film graininess increased in all films. The increase was greatest in Min-R M, and the rate of increase at 2.0 cycles/mm was 1.67 or more. The film showing the smallest increase was UM-MA HC, for which the rate of increase was 1.03-1.21. There were cases in which the spatial frequency at a 50 percent contribution rate of film graininess to radiographic mottle changed to a low spatial frequency. When only the increase in WS of radiographic mottle was examined, the increase was greatest in Min-R Medium/Min-R M, and the rate of increase at 2.0 cycles/mm was 1.65 or more. Min-R 2000/Min-R 2000 showed the least increase, and the rate of increase was 1.12-1.24. Increases in WS values were larger at 0.1-0.5 cycle/mm than at 2.0 cycles/mm when investigating the influence of trend using film graininess, and roller marks and so on could not be specified as a cause. (author)

[en] We applied an extended-cycle process, in which the processing time is longer than the manufacturer's recommendation, to a low-speed, high-resolution system in mammography and investigated to what extent sharpness, contrast, and speed would be maintained or increased and whether this process could be applied clinically. In this study, a single-screen/single-emulsion film, Konica M-100/CM-H, was used in the low-speed, high-resolution system, and M-200/CM-H was employed for comparison. Developing temperatures of 30, 32, and 34 degrees centigrade and a processing time of 210 seconds were selected as conditions of the extended-cycle process. M-100/CM-H with the extended-cycle process (M-100/E system) and M-200/CM-H with the standard-cycle process were compared at 34 and 90 seconds (M-200 system) in terms of contrast, speed, modulation transfer function (MTF), and Wiener spectrum (WS). In addition, the visibility of mammograms obtained using an RMI 165 phantom was evaluated by the method of paired comparisons. In the comparison of the M-200 system with the M-100/E system at 34 and 210 seconds, the speed was almost equal and the average gradient and MTF value at 2.5 cycles/mm increased about 20% and 8%, respectively. WS was higher due to the increase in quantum mottle with increases in the average gradient and MTF. In the scale of the method of paired comparisons, M-100/E systems showed better results. Moreover, entrance skin exposure in air of the M-100/E system at 34 and 210 seconds was almost equal to that of the M-200 system. These results suggested that it was possible to improve visibility by the extended-cycle process in a low-speed, high-resolution system. (author)

[en] A comparison of the image quality of a high resolution scan (HR scan) and a standard scan (ST scan) of a 7020 CT scanner was made by means of physical evaluation and psychological visual evaluation. According to the physical evaluation, it has been found that the HR scan was superior in modulation transfer function, but inferior in noise and contrast scale to the CT scan. Both the HR scan and the ST scan were satisfactory in uniformity and linearity. The ST scan was superior to the HR scan according to the psychological visual evaluation. This was probably due to the increase of noise in the HR scan. It may be concluded from the results of this comparison that the HR scan is suited to differentiate the fine structures in a high contrast area, while the ST scan is suited for a scan in a low contrast area. (author)

[en] We have often encountered patients with dental metal when employing the 10 MV X-ray beam therapy for head and neck tumors, and felt it important to investigate the effect of dental metal in relation to dose distribution. The absorbed dose rose abruptly in the vicinity of the metal reaching an interface value equal to 150% of the dose within the acrylic phantom. These results showed that an overdose occurred about 5 mm from the metal. We also learned that the overdose can be avoided by using a 5-mm thick tissue equivalent material. Six patients with dental metal were treated after first covering their metal with a 5-mm thick mouthpiece. No radiation stomatitis caused by the metal was observed in any of these cases. (author)