Tissue Dose Rate Research Articles

Mixed radiation dosimetry of a plutoniumberyllium neutron source.

The dose rate delivered to an assumed standard tissue by the fast- neutron and gamma -radiation from a standard 1 c plutonium-beryllium neutron source was determined by measurements with ethylene-filled polyethylene and CO²-filled Teflon ionization chambers. The resulting ionization currents as measured with a calibrated vibrating-reed electrometer were used to obtain a measure of both the gamma - and fast-neutron components of the emitted radiatdon. The tissue dose rate due to the fast neutron extrapolated to 1 cm from the source was found to be 1.74 rads/hr. The gamma -component was found to contribute 0.16 rad/hr. From the neutron dosc rate and the neutron spectrum for Pu- Be, the emission rate of the source was calculated to be 1.65 x 10 neutrons/ sec-c. A discussion of the neutron and gamma spectra of the emitted radiation from this source and some aspects of ionization chamber design are also included in this report. (auth)

A Substance Observed within the Vascular System of Dogs Receiving Lethal Exposures of Whole-Body X-Irradiation

Forty-one purebred beagles between 10 and 12 months of age were exposed to whole-body X-irradiation throughout various seasons in 1955. These dogs were raised and cared for in a manner similar to that described in a previous report (1). The dogs were exposed to irradiation by being taken into the Department of Radiology. Each dog was placed on a table in the standing position while being suspended from an overhead bar by cotton towels used as a sling around the neck and abdomen. The dog's feet were secured to the table top by muslin straps to avoid excessive movement. No adverse effects or undue excitement on the part of the dogs has been observed when this method of restraint is used, as the animals are regularly examined on a similar table for preliminary conditioning. A 250-kvp 30-ma Maxitron unit was used with a Thoraeus No. II filter having a HVL of 2.65 mm Cu. The target-skin distance was 135 cm, and the average tissue dose rate was 8.9 r/min. The dogs received a bilateral exposure; after one-half of the dose was delivered, the dogs were rotated 180 degrees so as to receive the remaining dose through the opposite side. The average thickness of the dogs discussed in this report was 10.5 cm at the tenth rib. To estimate the tissue dose, a dog of average size (10 kg) was sacrificed and a Victoreen r-meter (No. 1397) was placed at various positions in and on the body. The dog was placed in the X-ray beam and exposed in the same manner as the experimental animals. It was ascertained that the tissue dose along the central longitudinal axis of the dog's trunk varied from 291 r to 300 r. The skin dose varied from

The treatment of lung cancer with radiation and radiomimetic drugs.

The encouraging results obtained by Roswit and his associates (4) by combining roentgen irradiation with nitrogen mustard in the treatment of pulmonary carcinoma prompted the writers to undertake this form of therapy between 1950 and 1954. Although the response of pulmonary carcinoma to nitrogen mustard is limited, it is sufficient to suggest that if it were combined with radiation better palliation might then be achieved. Results from irradiation alone are only fair. With the addition of nitrogen mustard, an increase in mean survival from 9.4 months to 12.8 months from onset of symptoms has been reported. In experiments on mice, Karnofsky et al. (2) found that the toxicity of mustard, as measured by its lethal effect, was reduced by preliminary irradiation. In view of this apparent decrease in the effectiveness of the drug, it was decided to give the irradiation following rather than preceding the administration of the mustard, a procedure which had also been tried by others. It gradually became apparent, however, that the magnitude of the systemic reaction, particularly the hernocytic depression, limited the amount of radiation which could be given. Several ways of avoiding this were possible: The dose of mustard could be reduced, there could be a delay between the administration of mustard and irradiation to allow recovery, or the irradiation could be spread over a much longer period of time. None of these seemed desirable, so that in our later patients, the x-ray therapy was given first, followed at once by nitrogen mustard while the tissues were undergoing their fullest radiation reaction. The lower systemic toxicity which could be expected seemed an advantage and Klopp's work (3) indicated that there would be no impairment of effectiveness of the mustard. Material and Methods Our pulmonary cancer series numbered 38 patients, 32 males and 6 females, and included 20 squamous-cell, 8 undifferentiated, and 3 anaplastic carcinomas and 2 adenocarcinomas. The diagnosis in the remaining 5 was based on the finding of neoplastic cells in sputum. In all except 12 obviously inoperable patients exploratory thoracotomy was done, with partial resection of the tumor (19 cases) or pneumonectomy (7 cases). Patients with evidence of generalized carcinoma were not accepted for treatment. No patient with a recorded white blood count under 5,000 received chemotherapy. The radiation was given at 250 kvp, h.v.1, 1.5 mm, Cu, and focal-skin distance 50 cm. The treatment was directed to both the primary tumor and the mediastinum. A tissue dose rate of about 1,000 r per week was maintained. Six patients received intravenous nitrogen mustard initially and 6 following irradiation. The dose was 0.2 mg. per kilogram of body weight on each of four successive nights.