Eric G. Mayer

The Potential of Localized Heating as an Adjunct to Radiation Therapy1

Experimental studies have shown that (a) tumor cells may be more sensitive to heat than normal cells; (b) hyperthermia inactivates cellular repair mechanisms for radiation damage; and (c) heat may lower the OER for ionizing radiation (anoxic cells are at least as sensitive to hyperthermia as oxygenated cells). Localized hyperthemia produced by localized current fields in the range of 100 kHz-10 MHz by direct contact electrodes offers two major advantages: the eletrode configurations may be manipulated to obtain desired thermal dose distributions, and, since the mode of heating is essentially instantaneous, accurate temperature control can be maintained during treatment.

Complications of irradiation related to apparent drug potentiation by adriamycin

Abstract Clinical observations were made on 18 patients who were treated with combined irradiation and chemotherapy. A total of 21 irradiation reactions were noted, remarkable for their severity and persistence. Adriamycin (ADM) was the one drug common to all chemotherapeutic regimens. The reactions involved skin, esophagus, heart, lung and oral mucosa. No consistent pattern was established between the type or severity of reaction and the dose of drug or irradiation, nor of the temporal relationship of one to the other. It appears that ADM toxicity may potentiate irradiation reactions and that a “standard” total dose may be equivalent to a dose of irradiation on the order of 1000 rad. Since ADM persists in body tissues for prolonged periods of time, irradiation reactions may occur unexpectedly. All reactions improved, but eventual long-term effects cannot be determined at this time. A plea is made for controlled observations to determine safe schedules for the combination of these agents.

RELATIONSHIP OF TIME DOSE FACTORS TO TUMOR CONTROL AND COMPLICATIONS IN THE TREATMENT OF CUSHING'S DISEASE BY IRRADIATION?

Abstract The records of the Radiotherapy Division of the Radiology Department of Vanderbilt University Hospital were reviewed for the period 1952–1970. During those 19 years 45 patients with a well-documented diagnosis of Cushings disease were treated initially by external irradiation of the pituitary. All of the patients were treated with megavoltage equipment using photons. When the results of irradiation are compared against total doses of radiation, it is evident that the control rate is unsatisfactory at doses less than 4000 rad and the maximum benefits of irradiation are evident in the 4500–5000 rad dose range. It is also clear that the complication rate increases as the dose exceeds 4800 rad. If the various treatment regimens of irradiation are converted to “equivalent” doses by the Nominal Standard Dose (NSD) or Time-Dose-Fractionation (TDF) methods, the relationship between “dose” and efficacy of therapy and complications is demonstrated. In order to reduce the possibility of treatment-related morbidity, the use of three or more small (4 × 4 cm) treatment portals or rotational techniques is recommended to a pituitary dose of 4600–5000 rad treating 5 days a week for 5–6 weeks.

Part II: High Daily Dose Experience Without Laminectomy'

COMPRESSION OF THE spinal cord is a medical emergency. If treatment is unsuccessful, transection of the cord results in lack of sensation, paralysis of limbs, and loss of sphincter control. When the compression is the result of lymphoma or metastatic carcinoma, management has classically consisted of laminectomy and tumor resection. Most centers utilize radiation therapy postoperatively in low to regular daily dose schedules as an adjuvant to the surgical attack, occasionally with the simultaneous administration of chemotherapy. The rationale evolved has been based upon the emergency nature of spinal cord compression and the dire consequences of failure to halt its progression. Because immediate decompression is considered essential, laminectomy is the procedure of choice. Some physicians believe that surgical decompression also reduces the risk of radiation edema due to tumor or spinal cord swelling, which may heighten the risk of further cord compression before relief is obtained. The statistics in the ...

Age as a prognostic indicator in carcinoma of the lung.

Selected elderly patients with squamous cell carcinoma localized to the lung should be considered for radical irradiation. Age should not be used as a negative prognostic indicator. This group of patients has a lower incidence of distant metastasis and local control may produce long-term survival. Radical irradiation is well tolerated, particularly as a split course, and serious complications are few.

10 MV x-ray beam characteristics from a new 18 MeV linear accelerator.

Abstract The dosimetic properties of interest in a megavoltage therapy X-ray beam are per cent depth dose, skin sparing, penumbra, radiation field flatness and symmetry. The 10 MV X-ray beam from the Varian Associates Clinac 18 Linear Accelerator is studied with regard to these points. The primary points of interest are a 50% depth dose for a 10 × 10 cm 2 field at 18.0 cm in water and a depth of maximum dose of 2.4 ± 0.1 cm in water. Transmission measurements in aluminum and lead yielded 50% transmission thicknesses of 73.2 and 13.4 mm respectively. The flatness of the fields are parametrized as function of field size and depth. Decrement line plots are graphed and isodose curves for selected field sizes are presented.

Patient repositioning and motion detection using a video cancellation system

Abstract A video cancellation technique has been developed for patient repositioning and patient motion detection in radiation oncology departments. The system uses a closed circuit television (CCTV) camera and monitor plus a video disc recorder. The method utilizes the live image from the CCTV and a stored image of the desired treatment set up from the video disc. The images are processed in a video subtraction mode and viewed in cancellation. Repositioning errors of a millimeter are detectable and patient movements of the same magnitude are readily visualized.

Evaluation of B-Mode Ultrasound as a Means of Improving Radium Dosimetry in the Treatment of Gynecologic Cancer

The radiation dose to the base of the bladder and anterior rectal wall during radium applications for gynecologic cancer is a function of the distances between the source and the bladder and rectum. Precise measurement of these distances depends on a number of factors and cannot be obtained with current radiographic localization techniques. B-mode ultrasound is useful as a means of supplementing available information. While it is not necessarily more accurate than standard radiographs, it offers a three-dimensional appreciation of pelvic anatomy and does appear to be more accurate than transverse axial tomography.

Method for gantry angle repositioning on rotational teletherapy equipment

Repositioning errors for given angles have been found to be as large as +/-0.5 degrees. Errors of this magnitude are undesirable and unnecessary. To overcome this difficulty, a small laser was mounted to the counterweight of our accelerator with its light beam projected at 90 degrees to the axis of the x-ray beam. The light beam is used as a lever arm to indicate large distances (0.125 in.) for small changes in gantry angle (0.1 degrees). Gantry angles can easily be respositioned within 0.1 degrees. Routine use of the laser beam indicator has reduced the time taken to reposition the gantry.