[en] Ultrahigh speed CT is called electron beam scanning type CT, which is a new type CT using an electron gun, and its clinical application has been advanced mainly in USA and Japan. The features of this ultrahigh speed CT are short scanning time and repetition time, and the change of the shapes of organs like pulsing heart and the changes of the shapes and densities of organs like respiring lung can be known by this means. The equipment is IMATRON C-100 using an electron beam scanning type x-ray generator. There are three methods of photographing with the IMATRON C-100, that is, cine mode, flow mode and volume mode. These methods are briefly explained. The primary purpose of applying CT to heart diseases is the accurate diagnosis of cardiac infarction. The ultrahigh speed CT can do the excellent detection of ventricular aneurysm. Also its application to coronary artery calcification, myocardial diseases and heart tumors is described. As for its application to the radiation therapy of chest diseases, the change of lung density in radiotherapy, the change of the CT values of lungs, and the application to the treatment are reported. (K.I.)

[en] In the clinical application of high LET radiation for radiotherapy it is necessary to estabish a criterion as a basis on which assess the biological effect of the widely varied fractionated regimes including mixed and boost use with low LET radiation of photons. These assessements are based on a scale of the biological iso-effect of normal tissues for dose measured both for high and low LET radiation. The generalized NSD (GNSD) and TDF (GTDF) for normal tissues of skin, lung and spinal cord were introduced. RBE formula estimated by the GTDF function is compared with experimental data published. (author)

[en] Irradiated field was determined on the nine patients of brain tumor using a new patient Beam Pointer System (BPS) attached to CT scanner exploited at NIRS. This system consists of a CT scanner, a computer system and a lazer positioner. After determination of the precise location and volume of the brain tumor and its upper and lower boundary on the CT images, the precise irradiated field was determined as pointed out on the patient's skin by the lazer positioner. There were also shown on the CT images the dose distribution and the angle of the beam to be applied. We treated 2 recurrent pinealomas, 2 primary pinealomas, 3 recurrent medulloblastomas, 1 pons glioma and 1 recurrent hemangioblastoma using the BPS. The total dose was 33 to 87 in TDF (mean 60.5) and the irradiated field was 40 x 40 to 65 x 90 mm2 (mean 50.6 x 54.4 mm2). Five of the nine patients (case 1,2,3,6 and 9) were in good state after radiotherapy using BPS. Three patients (case 4,5 and 7) were dead one month, 19 months and 7 months after radiotherapy, respectively. Case 8 showed recurrence 18 months after the treatment. A fixing apparatus for the patient's head to be used during the irradiation was individually provided as made of Sofran-S to assure the better reproducibility of the irradiated field. (J.P.N.)

[en] Nine patients of brain tumor were subjected to radiotherapy using the Beam Pointer System (BPS). Precise irradiation field for the brain tumor, which was determined on the CT scan, was pointed out on the patient's skin by the Laser beam. A fixing apparatus for the patient's head was indivisually made of Sofran S to assure the better reproducibility of the irradiation field. There was found 2 to 5 mm of deviation in the repeated positioning of the head with BPS method. Six patients were treated effectively and 3 not successfully. (author)

[en] C₃H mice aged 56 - 70 days, weighing 27 - 37 g were used throughout this experiment. A transplantable fibrosarcoma arising spontaneously from C₃H mice was used. For experiment, 10⁴ tumor cells suspended in 0.025 ml of saline solution were injected into the cerebral hemisphere by a 26 gauge needle with a micrometer syringe under nembutal anesthesia. Whole brain irradiation was performed at 7 days after injection of the tumor cells and the radiation doses were 2,000 and 20,000 rads, respectively. The feature of x-rays were 200 kVp, 20 mA, 0.5 mm Cu + 0.5 mm Al filtration and TSD 20 cm. The dose-rate was 340 - 360 R/min. The articles of this study were as follows: a) Determination of LD₅₀ values for the mice, tumor-bearing in the brain or non-tumor-bearing; and b) Observation of clinical features and gross autopsy findings of the mice following irradiation. The LD₅₀ values for 2,000 rad irradiation in the tumor-bearing or non-tumor-bearing mice were 10.9 and 11.4 days, respectively. LD₅₀ values of 3.7 days and 4.3 days were the results for the tumor-bearing and non-tumor-bearing mice irradiated by 20,000 rad, respectively. On the other hand, the LD₅₀ value for the control group, i.e. non-irradiated mice, was 6.7 days. At postmortem examinations, gastrointestinal bleeding was observed frequently in mice bearing tumor in the brain. Whole brain irradiation is effective to prolong the life of tumor-bearing mice. However, in some instances, deaths have occurred earlier in tumor-bearing mice compared to the control group. (author)

[en] Three types of applicators (TAO type, Ganken type and Henshke type) for intracavitary radiotherapy for cancer of the uterine cervix have been used in Japan. An average age of patients with cervical cancer has been increasing, and in the elderly patients with the small vagina, it would be difficult to insert these, relatively large applicators. Two types of new applicators have been made for these patients. One is a disposable type and another is a revolver type. With these applicators, intracavitary radiotherapy for the cervical cancer in the elderly patients is performed with ease. (author)

[en] Proton beam radiotherapy at the NIRS was started in Oct. 1979. The range of proton beam with 70 MeV is 38 mm in water. One of the best advantage for proton beam has the possibility to avoid to dose to critical organ perfectly and to be fitted spread out preteau peak to target thickness. In this study of construction method for bolus, water was considered to be used as new bolus in clinical application of proton beam radiotherapy. These bolus were adopted as it was transparent, water equivalent material to be closed contact to the patient skin surface and convenient for clinical use. (author)

[en] Biological effectiveness of 70 MeV proton beam generated from the NIRS cyclotron was studied. Seventh generation of a squamous cell carcinoma which arose spontaneously in a C3H/f female mouse was monodispersed by trypsin, and 1.2 x 10₅ cells were transplanted s.c. into right hind legs of syngeneic male mice. Five days after transplantation, legs with tumors were irradiated under nembutal anaesthesia. Tumor sizes were measured periodically up to 60 days. Time required for a tumor to grow 12.0 mm in diameter was obtained from culculations by use of computer, and termed as TG (tumor growth) time. TGD (Tumor growth deley) time, a difference of TG time between experimental and control groups, was used as an endpoint for tumor. For measurement of skin reaction, hair on right hind legs were depilated by depilatory 7 days before irradiation. Skin reaction was scored every other day up to 35 days, and mean skin reactions were employed as another endpoint. 30 mm spread out Bragg peak (SOBP) in water was used in proton irradiation, and its dose rate was about 90 Gy/min. The reference beam used here was 200 kVp X-ray with dose rate of 2.4 Gy/min. In the first experiment, biological effect of modulated proton beam was examined as a function of penetration depth. Depth was varied by applying various thickness of lucite plates. Tumor and skin effects were found to be very similar to the physical depth-dose distribution. Secondly, we examined relative biological effectiveness (RBE) of proton beam in the spread out Bragg peak, being at 15 mm depth in Lucite. RBEs were 0.82 for skin and 0.79 for tumor. Thereby, therapeutic gain factor (TGF) of 0.96 was obtained in our system. (author)

[en] Experimental assay method were used to estimate the growth delay time of irradiated tumors. Average growth delay times were plotted on a semilogarithmic graph as a function of dose, and the relative biological effectiveness (RBE) was estimated. The RBE after a single dose irradiation increased with increasing dose, when the tumors were irradiated under aerobic conditions. The RBE needed to produce a growth delay of 20 or 50 days was 2.6 or 3.1, respectively. On the other hand, if the irradiation was given under hypoxic conditions, the RBE needed to produce 10 or 20 days' delay was 3.5 or 3.1, respectively. For the fractionated dose irradiations, a treatment regime of 3 times a week was used, i.e., six equal doses were given in two weeks. The growth delay time after a single 600 rads of fast neutrons was 21.8 days, while it was prolonged to 24.6 days if the same total dose was given in 6 fractions. A similar result was observed after a larger neutron dose. On the other hand, fractionated X-ray doses were less effective than a single dose. The growth delay time was 60.1 or 40.6 days for tumors irradiated with a single dose or six doses of 4800 rads. These results might indicate that some of the features of high LET radiations are that tumor cells irradiated with fast neutrons were capable of repairing sublethal damage less extensively than those irradiated with X-rays and that chronically hypoxic tumor cells might be sterilized more effectively by fast neutrons than by X-rays. The latter phenomenon might lead to extensive reoxygenation after neutron dose and that of fractionated neutron doses are effective. (Evans, J.)

[en] A method for calculating the biological equivalent dose in planning treatment with fast neutron therapy was proposed by authors. Its method was based on the concept of the NSD and the TDF factors defined by Ellis and Orton and is applied not only to fast neutron therapy only, but also to the boost and mixed therapy of x-rays and neutrons. The biological dose of this therapy is expressed as the TDF x-ray equivalent dose. Biological dose distribution estimated by computer, considering the effect of treatment schedule, was also discussed. (auth.)