Tetsuo Inada

Irradiation synchronized with respiration gate

A respiratory gating technique was developed for radiotherapy of tumors unable to remain stable due to respiration. Irradiation was started and stopped with a microwave oscillator of a linear accelerator controlled by gating signals at specific points in the respiratory cycle. This technique was tested in a phantom specially designed to simulate a patient with lung cancer and in clinical therapy for lung tumors of seven patients. A mask was used to check ventilation in the phantom and airbags were used to measure thoracoabdominal pressure in patients and in the phantom; this enabled us to detect the excursion of the tumors. Low sensitivity film for verification demonstrated the efficacy of this technique. The gated irradiation was proved to ensure more precise radiotherapy for tumors located close to the diaphragm.

Spot scanning system for proton radiotherapy

In order to provide a uniform and desirable dose distribution over a large radiation field, spot beam scanning is one of the most useful methods. A new spot beam scanning system was constructed for a 70 MeV proton beam. The lateral dose distribution was uniform with +/- 2.5% for an 18 cm square field. It was possible to control the dose at each point in the radiation field by this spot scanning method. This system has been confirmed to be satisfactory for delivering a proton beam in the desired field shape and dose level.

Intraoperative radiotherapy for advanced carcinoma of the biliary system

Since November 1973, intraoperative radiotherapy has been performed on five patients with unresectable, advanced carcinoma of the bile duct at the hepatic hilus and six patients with unresectable carcinoma of the gallbladder. A treatment cone with a diameter ranging from 4–10 cm was directly applied at the lesion. A single dose of 2500–3000 rad with 11 to 20 meV electrons was delivered. In all patients, recanalization of the obstructed bile duct was observed by the postoperative cholangiography. The local efficacy was confirmed histopathologically in eight autopsied materials and a specimen resected 105 days after radiotherapy. Mean survival time of patients with unresectable tumors was 10.9 ± 5.6 (SD) months after this radiotherapy. Intraoperative radiotherapy increased the effectiveness and length of palliation for the unresectable lesion.

Protective effect of zinc against lethality in irradiated mice

The protective effect of zinc against radiation hazard was observed by comparing LD50(30) values of irradiated mice with and without the administration of zinc before irradiation. Two hundred male mice, 7 weeks old, were irradiated with an intestinal dose at 5.62, 6.31, 7.08, 7.94, 8.91, or 10.00 Gy, with or without oral administration of zinc from 10 days prior to gamma irradiation until the end of the study. The reduction of mortalities in zinc-administered mice in comparison to controls was most prominent at the dose of 7.94 Gy, i.e., the mortality rate in the zinc-administered group was 0.44 and that in the control group was 1.00. At a dose of 8.91 Gy, zinc-administered mice survived significantly longer than controls. The LD50(30) of zinc-administered mice was 7.70 Gy, while that of the control was 6.90 Gy. In zinc-administered mice the acceleration of turnover and elevated excretion of radioactive zinc were observed, while the concentration of stable zinc in organs remained constant. The effect of zinc was not observed in experiments in vitro using human melanoma cells. Therefore it can be assumed that the protective effect of zinc against radiation would correlate with the homeostatic mechanism of zinc which exists in the whole body of mammalians.

Three-dimensional beam scanning for proton therapy

Abstract An important goal of radiation therapy is to localize the dose in the target volume. The favorable properties of proton beams, such as a well-determined range and straight penetration through tissues, have been used to develop a three-dimensional beam scanning method. This system consists of a two-dimensional beam scanning system and an energy degrader of variable thickness which are both controlled by a beam monitor that is connected to a minicomputer. A typically conformed dose distribution with the three-dimensional beam scanning system was measured by a specially designed multiwire ionization chamber. The results have shown that the system works satisfactorily and considerably reduces the radiation dose outside the target volume.

Broad beam three‐dimensional irradiation for proton radiotherapy

A three-dimensional irradiation system using scatterers for lateral spreading is proposed. This system, which is applicable to proton beams, is easily achieved by ordinary techniques using a movable multileaf collimator, a variable thickness water column, and a computer for their control. Target volumes of convex shape can be irradiated in a three-dimensional way by this method.

Induction and Repair of DNA Lesions in Cultured Human Melanoma Cells Exposed to a Nitrogen-ion Beam

Induction and repair kinetics of DNA lesions after exposure to nitrogen ions (N-ions) were studied in comparison to those after 180 kVp X-rays. DNA lesions in human melanoma cells (HMV-I) irradiated with 95 MeV N-ions (0-6 Gy, l.e.t.D = 530 keV micron-1 or with X-rays (0.9 Gy) were assayed by alkaline elution. The N-ion r.b.e. for DNA lesion induction was approximately 0.7. About 85 per cent of the lesions induced by N ions were rejoined with a time-course similar to the rejoining of DNA lesions produced by X-rays. These lesions were considered to be induced by delta-rays around the N-ion tracks. The fraction of residual DNA lesions remaining after a 6 h post-irradiation incubation was higher for N-ions than for X-rays. Unlike the case for X-rays, DNA-protein crosslinks were included in the residual DNA lesions after N-ion irradiation.

Time resolved properties of acoustic pulses generated in water and in soft tissue by pulsed proton beam irradiation—A possibility of doses distribution monitoring in proton radiation therapy

Time-resolved acoustic pulses generated in water and in soft tissue by pulsed proton beam irradiation were observed. The spatial resolution of depth dose distribution in the clinically applied beam intensity is estimated about 3 mm by means of TOF measurement. The dependence of the acoustic signal intensity on the temperature of medium was examined. Proportionality of acoustic pulse intensity to absorbed dose per pulse was confirmed as well. These results suggest the possibility of clinical application to monitor dose distribution in the patients body during irradiation of pulsed proton beam.

A proton profile monitor using an amorphous silicon photodiode array

An amorphous silicon photodiode array originally manufactured for facsimile has been applied to an imaging system for proton beam measurements. A Gd/sub 2/O/sub 2/S phosphor sheet and a CsI(Tl) scintillator strip for proton-to-light conversion were tested to obtain good sensitivity. Proton depth dose distribution measurements for cancer therapy are presented. >

A comparison of biological effects of modulated carbon-ions and fast neutrons in human osteosarcoma cells

PURPOSEnTo compare the biological effects of a 135 MeV/u carbon-ion beam and 13 MeV fast neutron beam using human osteosarcoma cells.nnnMETHODS AND MATERIALSnWe have studied the clonogenic cell survival, recovery of potentially lethal damage (PLD) in plateau phase cells, and spheroid cure in multicellular spheroid after irradiation at various positions in the plateau and spread out Bragg peak (SOBP) of a 135 MeV/u carbon-ion beam and with 13 MeV neutrons. The carbon beam had a 4-cm range in water and a range filter was used to produce a 3-cm extended-peak region. The reference radiation was 137Cs gamma-rays.nnnRESULTSnThe relative biological effectiveness (RBE) values for 10% survival level of plateau phase cells for carbon-ions at the position of plateau, proximal peak, midpeak, and distal peak within the SOBP, and neutrons were 1.71, 2.48, 2.63, 3.47, and 2.29, respectively. Corresponding RBE values at 1% level were 1.64, 1.93, 2.06, 2.49, and 2.05. The extent of recovery from PLD was reduced after carbon-ions at proximal peak, midpeak, and distal peak, and neutrons, although not substantially reduced after carbon-ions at plateau. The RBE values for 50% spheroid cure level of spheroids for carbon-ions at the position of plateau, proximal peak, midproximal peak, middistal peak, and distal peak within the SOBP, and neutrons were 1.69, 1.88, 1.87, 1.94, 2.03, and 1.90, respectively.nnnCONCLUSIONSnThe biological parameters measured all indicate an approximately comparable biological effectiveness between 75-80 KeV/microns carbon-ions of the SOBP and 13 MeV neutrons in the human tumor model studied in vitro.