PubMed · 4773305
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T H Moss. 1973. Mössbauer spectroscopy.. https://doi.org/10.1016/s0076-6879(73)27038-6
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PURPOSE: A modified teletherapy unit to achieve total body irradiation with a vertical beam in a conventional treatment room. METHODS AND MATERIALS: A standard 60C teletherapy unit has been modified to achieve total body irradiation with a vertical beam in a conventional treatment room. Patients are treated in prone and supine positions. Removal of the adjustable collimator assembly of this standard machine provides a circular field of 196 cm in diameter at 167 cm from the source. Second, the machine has been elevated by about 50 cm on a metallic base to enlarge irradiation field to obtain 248 cm in diameter at 210 cm from the source, and to encompass tall patients under better conditions. A special lead conical beam flattening filter, 10-mm thick at the center, was designed to compensate the spatial inhomogeneity of the beam. An instantaneous dose rate of 6.10(-2) Gy/min is attained at the L4 level (midplane) in an average 20-cm thick patient with a source activity of 5099 RHM (air kerma rate of 44.8 Gy.h-1.m2). Between February 2, 1984 and December 27, 1990, 244 total body irradiations were performed either by single dose (n = 69, 10 Gy were given to midplane at L4 level in about 6 to 8 h, 8 Gy to the lungs), or by fractionated dose (n = 175, 12 Gy were given in 6 fractions over 3 consecutive days to midplane at L4 level, 9 Gy to the lungs). RESULTS: The dose distribution is similar than the ones obtained by a linear accelerator with patients lying on their sides. CONCLUSION: Patients were treated in a comfortable and highly reproductible position. Organ shielding was easily achievable. This could be a less expensive and reasonable alternative to linear accelerator.
PURPOSE: This article describes the physical, technical, and dosimetric aspects of total body irradiation (TBI). METHODS AND MATERIALS: The continuous head swivel motion of a standard 60Cobalt unit has been used to obtain a sweeping beam that encompasses the entire length of the patient in TBI. A perspex beam flattener designed to remove the inverse square fall-off in beam intensity along the sweep axis provides a 90% field length of 200 cm in air at a treatment source-to-skin distance of 160 cm. The anterior-posterior parallel pair setup permits accurate placement of customized lead compensators to limit the dose to lungs. RESULTS: Measured beam profiles, dose buildup curves, and percentage depth dose for the technique are presented. With compensators in place, the variation in lung dose is shown to be within +/- 5% of the prescribed tumor dose. CONCLUSIONS: A sweeping beam TBI technique has been devised using a standard 60Cobalt unit. The technique allows the patient to be treated in supine and prone positions, which facilitates the accurate placement of lung compensators to limit the dose to lung tissue.
PURPOSE: This quality assurance program is designed for stereotactic radiosurgical units, gamma knife, to check and maintain the unit to preclude accidents and comply with current regulations. MATERIALS AND METHODS: Over 58 stereotactic radiosurgical units using 201 focused 60Co beams have been installed in the last 7 years and are in use at hospitals throughout the world, with at least 11 additional units being prepared to come on-line in the next year. This system has been in use at the University of Pittsburgh Medical Center (UPMC) for 7 years. A comprehensive quality assurance program has been developed. It includes the physics and dosimetry parameters and safety checks required by regulatory agencies. The program, based on over 7 years of experience in measurements, and used during the treatment of over 1500 patients, is separated into three aspects, namely physics, dosimetry, and safety. The UPMC program hopefully will indicate out-of-tolerance problems. Some quality assurance items are checked on a daily basis prior to patient treatment, while other aspects are checked on a weekly, monthly, and/or annual basis. A complete list of items with their respective time tables and tolerances is provided. RESULTS: Although experience shows very small margins of error, larger values were chosen to account for variations in equipment and techniques. CONCLUSIONS: Items included in this quality assurance program should indicate and/or preclude problems encountered in the use of this unit.