John S. Laughlin

THERMOGRAPHY IN THE MANAGEMENT OF CANCER: A PRELIMINARY REPORT

The direct measurement of infrared emission from the human body by a special infrared camera, thermograph, has been pioneered by Lawson,’ Williams and Handley,Z B a r n e ~ , ~ . ~ and Ger~hon-Cohen.~ Their thermograms or “heat photographs” have confirmed the classical clinical observations that some tumors are “hot” while others are “cold.” This early report concerns the use of the Barnes Infrared Camera on 200 patients with benign and malignant tumors in varied anatomical sites. In 1800, Sir William Herschel5 observed that the sun’s spectrum contained electromagnetic energy of longer wavelengths than visible red. He found these infrared waves by diffracting sunlight through a prism into the visible spectrum. By placing thermometers throughout the visible spectrum and beyond the visible red, invisible heat or infrared was noted. Infrared refers specifically to the electromagnetic energy of wavelengths which exist between visible light and microwaves. Every object whose temperature is above zero emits this particular type of radiant energy. In the past 20 years very sensitive detectors have been developed primarily for military use. When combined with modern optical and electronic systems a practical record for accurately measuring and scanning has become available. The Barnes Infrared camera transforms the invisible energy, infrared, emitted from the patient into visible light which is recorded on an ordinary Polaroid black and white film. This picture, thermogram, is a quantitative heat map of the patient. By comparing the light (hot spots) and the dark (cold spots) of similar anatomical areas one can accurately compare the temperature of the skin overlying the tumor, The target scanning mirror represents a sweep pattern of 20’ wide and 10’ high. The radiometer head is equipped with a filter which cuts off wavelengths shorter than 1.8 microns. This allows accurate measurements to be made in daylight or darkness. Scan times range from 6 to 12 minutes depending on the size of the anatomicai area to be observed. Detail as small as !h inch can be obtained from a distance of 10 feet with an accuracy of 95 degree Fahrenheit. While we usually think of the body temperature measured by the oral or rectal thermometer as being rather stable this is not always true when applied to the skin. The skin temperature is lower than the internal temperature. It is influenced by the conduction from heat sources within the body, vascularity of the area, heat loss due to sweating, air convection currents and by infrared energy exchange with every object in the immediate line of sight. By keeping the patient undressed and reclining for 15 to 20 minutes in a room without drafts at approximately 70’F. these variables can be controlled for all practical purposes. A 45’ front faced mirror enables the patient to recline in comfort and decreases motion which would be transferred to the thermogram. After learning the simple technical details of using the Barnes Camera we studied a few patients with clinically hot lesions, i.e. abscesses, contusions, cellulitis, etc. Next a few patients with obvious peripheral vascular disease, necrotic wounds,

CALORIMETRIC DETERMINATION OF ABSORBED DOSE AND GFe +++ OF THE FRICKE DOSIMETER WITH 10-Mev AND 20-Mev ELECTRONS

The construction and operation details of a local absorbed dose microcalorimeter are presented. This calorimeter measures the absorbed dose rate at any desired point within an irradiated medium. The measurement is specific to a sufficiently limited region (2.0 cm in dia, 0.3 cm deep) that the measurement is essentially at a point and no integration or averaging process is necessary to qualify either the absorbed dose, or its rate. The system is sufficiently sensitive to provide about 1% accuracy at dose rates of 50 rads/min. The application of this calorimeter to 10-Mev and 20-Mev incident electrons is described. The use of a secondary standard (Victoreen 25-r chamber) under specified conditions is given together with details of calibration for use with high-energy electrons. The influence of the polarization effect was noted. The Fricke ferrous sulfate dosirieter was also calibrated for these energies of electrons. Samples of dosimeter solution were exposed in a geometry identical with that of the small sensitive region of the calorimeter. A value of G/sub Fe// sup 3+/ of 15.32 plus or minus 0.34 was obtained for 10-Mev electrons, and a value of 15.17 plus or minus 0.28 for 20-Mev electrons. (auth)

Comprehensive electron-beam treatment planning.

This report on electron-beam treatment planning is based on experience with both the electrons in the 6to 24-mev range from the Allis-Chalmers betatron and those in the 15to 35-mev range from the Brown-Boveri betatron. It is based primarily on treatment-planning experience in the United States, particularly as applied at the Memorial Hospital in New York since 1955. The treatmentplanning method in use at Memorial Hospital provides a systematic method for determining the actual dose distributions in a patient, taking into consideration wedges, surface irregularities, and tissue heterogeneities. The term comprehensive in the title of this report implies such corrections. Because of the large volume of cases treated at Memorial, it has been necessary to develop a system that could be routinely applied, making use of approximations wherever possible. Where indicated, even greater individualization can be accomplished by using the variation of correction factors with depth rather than averages. Annually, approximately 500 cases receive comprehensive treatment planning for external radiation as well as the 150 to 200 cases that receive comprehensive implant dosimetry planning. Since the absorption of electrons is determined by quite different processes from those applicable to x-rays, this system was based on the specific characteristics of electron absorption.’” Corrections in this system are applied by representing an isodose distribution by several depth-dose distributions along rays emanating from a virtual ~ o u r c e . ~ ’ ~ Segments of unit density depth-dose distributions are translated sequentially along a ray by an amount dependent on location, extent, and electron density of the inhomogeneous region. To examine the influence of inhomogeneities, the distribution of dose produced in a pressed wood phantom in which various materials were inserted was measured by either film or small cavity ionization chamber methods. Recent measurements have also employed highimpact polystyrene, a fairly new tissue-equivalent material, which is opaque and very convenient, especially for film measurements. The data in the following figures were obtained with 6to 20-mev electrons through the following field sizes

A computer method for radiation treatment planning

Automatic computation methods were first developed and applied to the problem of radiation therapy treatment planning by the Physics staff at Memorial Hospital and Sloan-Kettering Institute in 1954 and reported in 1955 [1]. The field of radiation from a single port was stored as a matrix in a library of punched cards, and a sorter and accounting machine were used to combine various fields for rotation, cycling and multi-port therapy. This system was in continuous routine use from then until 1961, when the equipment was replaced by a Bendix G15-D digital computer. Subsequent work by Sterling [2] followed essentially the same method of describing the radiation field as used by the Physics staff at Memorial Hospital [1], except that more powerful equipment has been used. An analytic expression for the dose distribution produced by rotation had been previously applied successfully in 1951 to treatment planning with high-energy X-rays [3].

REALISTIC TREATMENT PLANNING.

Some ionizing radiations in specified energy ranges have physical properties which make them useful in treating human cancers, although this method of treatment has limitations. The author describes the limitations which make radiation therapy difficult as compared with such methods as surger. The advantages and problems of the application of high‐energy x‐rays and electron sources are discussed. The author discusses specialized instruments and techniques developed for use in modern radiation therapy. The application of these techniques has required the development of systems for comprehensive treatment planning to be made available to many patients.

The Radiation Chemistry of Aqueous Ferrous Sulfate-Benzoic Acid Solutions

>The effects of Cl/sup -/ and O/sub 2/ observed when other organic compounds were introduced into the Fricke dosimeter were also observed with a ferrous sulfate-benzoic acid system, although ferric yield was considerably more reproducible in this case than in previously tried systems, The conclusion that peroxides are formed was reinforced by the fact that ferrous ion is oxidized by benzoic acid solutions which have previously been irradiated. The production of hydroxy isomers of benzoic acid was found to occur to a greater extent in this system (G = 1.9 molecules per 100 ev; G/sub m/ = 3.1; G/sub p/ = 1.6) than in alkaline solution of benzoic acid alone as investigated by Armstrong et al. (G/ sub o/ = 0.67 molecule/ev; G/sub m/ = 0.37; G/sub p/ == 0.37), and in different ratios from those found by Armstrong (o/m/p = 9: 5: 5) or by Loebl et al., who irradiated at pH 3 and got ratios of 5: 2: 10. These discrepancies might indicate either differences in analytic technique or a fundamental difference in mechanism due to the presence of ferrous ion. (auth)

THE RELATIVE BIOLOGICAL EFFECTIVENESS OF 180-Kevp AND 22.5-Mevp X-RAYS DETERMINED FROM THE DOSE-SURVIVAL CURVE OF SACCHAROMYCES CEREVISIAE

The use of supervoltage X-rays for deep therapy has stimulated interest in the relative biological effectiveness (RBE) of such radiation compared to that conventionally employed (200 to 400 kevp). For betatron X-rays of about 20to 31Mev peak energy, reported RBE values have ranged from 0.4 to 1.0 (1-7); for betatron electron beams of about 3 to 6 Mev, from 0.4 to 1.45 (8). Although this range of values may be due to differences inherent in the nature of biological systems, it may also stem, at least in part, from the limited precision of the methods employed and from differences in the basic concepts underlying the dosimetry, e.g., air dose (roentgens), tissue dose, and absorbed dose (rads). We have defined the RBE of supervoltage X-rays as the ratio of absorbed dose of standard X-rays (180 kevp) to that of supervoltage X-rays (22.5 Mevp) when both produce the same biological effect. In the present experiments, employing the X-ray beams of the 180-kvp machine and the 22.5-Mev betatron at the SloanKettering Institute, the biological effect was measured in terms of the dose-survival curve of a microorganism. The technical problems involved in the determination

The Memorial Implant Dosimetry Automated System

Abstract The current status of computer programs and procedures for implant dosimetry at Memorial Hospital is reported. The implant dosimetry programs and associated procedures have been given the name MIDAS: Memorial Implant Dosimetry Application System. A short history of MIDAS, as well as program objectives, conventions, assumptions and organization are discussed and a complete sample case is shown with explanatory annotations.

Dosimetry of localized beams.

In some biological experiments aimed at evaluating the localized effect of radiation on specific parts or organs of animals, x-ray fields of about 1.0 to 1.5 cm. diameter must be used. Typical examples are the irradiation of tumor implants in mice or hamsters, and the irradiation of knee joints of young mice. Small fields are also necessary in order to achieve uniform irradiation in some bacteriological and chemical experiments which require doses of the order of 100,000 r and can thus be carried out practically only at small target distances. Figure 1 shows the use of a localized beam for the irradiation of the knee joint of a young mouse. This particular experiment was undertaken in an attempt to correlate the decrease in the production of alkaline phosphatase in the knee joint with the energy absorbed by the soft tissue in bone; it is an extension to higher energies of similar investigations carried out with x-ray beams with peak energies of 100 kev, 180 kev, and 1,000 kev (1). Only the knee joint is i...

Calibration of the absorbed dose produced in water by betatron electrons with the benzoic-acid dosimeter.

Monitoring of betatron electron beams used for therapy in the United States during the past decade has most frequently been done with a transmission ionization chamber, the output of which is calibrated periodically in terms of the reading of a Victoreen ionization chamber surrounded by sufficient additional plastic material to obtain the maximum response (1, 2). These monitor measurements may be converted to absorbed dose by calculation (3) or by calibration with the absorbed dose calorimeter (4). This conversion is more conveniently accomplished through the use of a suitable chemical dosimeter. Such an approach is also more direct than the use of calculated conversion factors, which necessarily involve major assumptions. In the experiments to be described here the benzoic-acid dosimeter has been used to determine the absorbed dose rate produced by betatron electrons at the depth of relative maximum dose in water. These measurements have been related to the conventional and arbitrary specification of bet...