Marvin M. D. Williams

MICROANGIOGRAPHY OF BONE IN THE STUDY OF RADIATION CHANGES

In a study of possible vascular changes in bone following irradiation and an evaluation of microangiography in their demonstration, the right hind legs of 17 albino rats ten weeks old were irradiated, with an air-exposure dose of 1,020 r generated at 130 kv and filtered by 5 mm. Al. The animals were sacrificed two to thirty days thereafter. Both hind legs of each were perfused with either a 50 per cent suspension of finely divided barium sulfate (Micropaque) or a 25 per cent suspension of thorium dioxide (Thorotrast). The femurs were decalcified and embedded in wax, and sections 100 microns thick were made for microradiography. The primary equipment for radiography was a General Electric x-ray diffraction tube with a beryllium window and Kodak 2-in.-square high-resolution plates. The tube was operated at 15 kv, 25 ma, and the film was exposed for fifteen seconds. Micropaque provided good demonstration of the larger vessels in the cancellous bone and marrow cavity. Thorotrast, on the other hand, showed sma...

The effect of X-Rays on the electric potentials and the rate of oxidation of frog's skin

In a previous investigation, W~sL~A~s studied the effect of x-rays on the potent ial difference across frogs skin for a period of t ime following a lethal dose of irradiation. During the present investigation a smaller dose, which was not lethal, was used, and the effect produced was determined at intervals for a month following irradiation, iS was suggested in the previous report tha t the changes in potent ial difference were indicative of similar changes in the rate of oxygen consumption. In the present investigation measurements were made to test this assumption.

The Effect of Shockproof Cables and Condensers on Two-Valve Half-Wave Rectification1

Various changes in roentgen therapy equipment during the past few years have afforded an opportunity for comparing the quantity and quality of radiation produced by several types of rectifying circuits and particularly for observing the effect of the capacity of shockproof tubes and cables and of additional capacity, in the form of condensers, on two-valve half-wave rectification. Since all the machines were in regular use for treatment, it has not been possible to make all the changes in the circuits for which data might have been desired, and since the oscillographic equipment was not available at the time some of the circuits were in use, their voltage wave forms could not be obtained. The combinations of rectifying circuits, types of tubes, and types of connections between the rectifier and tubes which have been available are listed in Table I. Since the x-ray tube current was not always the same, the total intensity in roentgens per minute would not be expected to be the same; therefore, comparisons ...

An Electric Model of an X-Ray Machine

It is well known that the quantity and quality of radiation emitted by an x-ray tube vary with the wave forms of both the voltage applied to the tube and the current flowing through the tube. The voltage wave form depends primarily on the type of rectifying circuit used and to a lesser degree on the characteristics of other parts of the x-ray machine, such as the transformer, the primary circuit, and the x-ray tube. The current wave form depends, of course, on the voltage wave form, but is equally dependent on the characteristics of the x-ray tube unless the rectifying circuit supplies constant potential. Hence measurements of peak volts applied to the x-ray tube and of the average current flowing through the tube, which are the common factors measured, give no idea of the quantity and quality of the radiation which will be emitted from the tube. It would seem, therefore, to be of some value to radiologists to know the general type of wave forms produced by the more commonly used rectifying circuits and t...

Construction of Isodose Lines for 6 MV X Rays by the Decrement-Line Method

We have found that the decrement-line method for construction of isodose curves originally applied by Orchard to cobalt-60 gamma rays is satisfactory for x rays generated by a 6 MV linear accelerator. We made “SSD curves,” with 100 cm to the surface and the 100 per cent reference point at the depth of maximal build-up (1.6 cm), and “SAD curves,” with the 100 per cent reference point in the depth at a fixed distance from the target of 100 cm. With a remote locator and a Victoreen ratemeter ionization probe, we determined the locations having decrement values: 0.975, 0.95, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, at 4 or 5 depths, for 4 square field sizes in the SAD setup and for 6 fields in the SSD setup. The decrement lines can be regarded as straight lines with sufficient accuracy, and, in fact, decrement measurements would be needed only at two depths: 5 and 15 cm being suitable for the SSD setup, and 7.5 cm above and 7.5 cm below the reference point (axis) for the SAD setup. The decrement lin...

The Exponential Law of Tissue Recovery Applied to Radium and Radon Dosage

IT has often been assumed that tissue recovery from radiation effects follows an exponential law. By the use of this law in the saturation technic of radiation therapy, tissue recovery is calculated for the time between treatments. When a treatment lasts for only a short time, the tissue recovery during the period of treatment is negligible; but when a treatment lasts for many hours, as many radium and radon treatments do, the tissue recovery during this period may not be negligible. In some instances, it seems possible that a better correlation between tissue effect and the dose given might be obtained if the saturation dose, which takes into account the tissue recovery during the treatment, was considered rather than the total dose. The expression “tissue recovery from radiation effects” is indefinite because little is known about the effects of radiation on tissue. Most of the effects usually considered to be due to irradiation are probably secondary effects caused by a primary effect. The primary effe...

Changes in Electric Potentials and Rates of Oxidation of the Skin Subsequent to Roentgen Irradiation1

IN most of the experimental work which has been done on the effects of irradiation with roentgen rays on biologic materials, an end-effect only, or the effect at one definitely specified time after the irradiation, has been investigated. The purpose of the investigations now being reported was to determine the variations in the physiologic quantities of frogs skin, namely, the electric potential difference across the skin and the rate of consumption of oxygen of the skin as dependent on the time after irradiation. Other investigations have shown that there is some relation between the electric potentials and the rate of consumption of oxygen and that the magnitude of the potential difference may be taken as a “measure of life” or of the vitality of the skin. The literature regarding the correlation in living organisms between metabolic and electric gradients has been reviewed and additional evidence brought forth in papers by Child (3), Child and Hyman (4), and Hyman and Bellamy (8). The results of the m...

Radon Ointment Treatment of Irradiation Ulcers1

Large irradiation ulcers with accompanying necrosis, infection, and sloughing, and often eventual malignant changes, have long been a serious therapeutic problem. Treatments designed for ordinary deep burns are not effective; the ulceration produced by atrophy of the skin and vascular obliteration is extremely indolent. Probably the only effective treatment has been excision and skin grafting. Because of the usual infection and malignant changes, along with the reduced blood supply, satisfactory results have not been frequent. Fortunately, fewer of these extensive ulcerations are now seen than formerly. Better understanding of the biologic effects of irradiation and the more accurate determination of dosage have contributed to this improvement. The tissues of some patients, however, prove abnormally sensitive to roentgen and gamma rays. Furthermore, to arrest many deep-seated cancers, irradiation has to be pushed to the limits of tissue tolerance. Instances of slowly developing, severe injuries from irrad...

Recovery of Radium Tubes from Sewer

A search for three tubes of radium which had been lost in a sewer, and the recovery of the last of these tubes fifty-four days after it disappeared, involved the use and consideration for use of some equipment which it is believed had not previously been employed for such work. The successful conclusion of this search was due to the suggestions and cooperation received from the hospital authorities, employees of the city engineers department, members of the biophysics laboratory section, representatives of the insurance company, Prof. J. W. Buchta of the University of Minnesota, and numerous others whom we may have inconvenienced. The tubes each contained approximately 50 mg. of radium, sealed inside a glass tube, which in turn was sealed inside a tube of Monel metal whose outside dimensions were 27 mm. (1 1/16 inches) in length and 5.6 mm. (a little less than 1/4 inch) in diameter, with a wall thickness of 1.5 mm. At the time the tubes were lost, each was tied in a separate finger cot and had small piec...

Radiation from an Oil-Immersed Therapy Tube

The intensity of the radiation from a therapy tube immersed in a large tank of oil was found to decrease as the size of the diaphragm opening in the filter holder was decreased. The smallest diaphragm used was large enough to allow all the direct radiation from the target to reach the ionization chamber. Because this decrease in intensity seemed too great to be ascribed only to the absorption of radiation originating from parts of the tube other than the target, it seemed that an explanation might be that some of the radiation which passed through the larger diaphragms was scattered by the oil surrounding the tube. A diaphragm with a smaller opening would absorb part of the scattered radiation and thereby reduce the intensity of the radiation reaching the ionization chamber. The results reported here indicate that part of the decrease in intensity caused by the use of small diaphragms was due to the absorption of radiation which had been scattered by the oil; also, the quality of the radiation became hard...