Joseph Mantel

Automatic variation of field size and dose rate in rotation therapy.

Abstract A technique is presented for changing the field size and dose rate as a function of gantry angle independently or simultaneously during rotation therapy. Two computational methods for calculating the dose distribution using the above technique are described. A comparison of the effectiveness of this new technique relative to conventional approaches is discussed.

Intravenous xenon-133 for the determination of radionuclide first pass right ventricular ejection fraction

The use of intravenous xenon- 133 for determination of radionuclide first pass right ventricular ejection fraction is described. First pass determinations of right ventricular ejection fraction were made with both xenon- 133 and technetium-99m in 13 subjects (15 right ventricular ejection fraction determinations); results obtained with xenon- 133 show an excellent correlation (r = 0.98, p less than 0.002) with results obtained using technetium-99m. Because of rapid pulmonary elimination of xenon- 133 from the body, the use of this radioisotope allows multiple first pass right ventricular ejection fraction determinations within a short period of time, without significant radiation exposure for the patient.

A PROGRAMMABLE CALCULATOR TO ACQUIRE, VERIFY AND RECORD RADIATION TREATMENT PARAMETERS FROM A LINEAR ACCELERATOR?

Abstract A system has been developed for the utilization of a Wang 600-14 programmable calculator to acquire, verify and record treatment parameters from a linear accelerator. The hardware and software components and operation of the system are briefly described. The system is in use daily.

Recovery and Reconcentration of Radioactive Gases from the Cryogenic Trap

Procedures and equipment are presented for concentrating radioactive noble gases, collected in the cryogenic trap for storage or reuse. Two simple and straightforward procedures which have worked well are described, and some of the difficulties to be avoided are discussed.

X-ray depth-dose characteristics of the Toshiba LMR-16.

The depth-dose characteristics of the Toshiba LMR-16 linear accelerator for 14-MeV x rays have been measured at an SSD of 100 cm using diodes and ion chambers. The surface dose and build-up depth both exhibit a considerable variation with field size. A new central axis model has been developed which takes account of these variations, and the agreement between the measured and computed data using this model is found to be excellent. Formulas are also presented to estimate the surface dose, buildup depth, and output factor as a function of field size.

Large-Field Telecobalt Therapy with a Moving Table Physical Considerations!

The moving-table telecobalt technique, employing a fixed source and a moving medium, is considerably different from other methods. The inverse square law and published values of the tissue-to-air ratio cannot be used in depth-dose calculations, since the percentage depth dose is higher than that obtained from stationary-field values for an equal irradiated area at the same depth and source-to-surface distance. The moving-table percentage depth dose can be approximated by employing a “reciprocal law” and interpolated values of the tissue-to-air ratio.

A Data Acquisition System for Three-Dimensional Treatment Planning

The authors describe a coordinate measuring device developed to simplify manual acquisition of the digital information required for computerized three-dimensional treatment planning. This system has been used for two years and shown to be both fast and accurate. The time needed to digitize contour data is reduced to approximately one-tenth of that required for manual methods in most cases.

LARGE-FIELD TELECOBALT THERAPY WITH A MOVING TABLE: TECHNICAL ASPECTS.

A common planning problem is the treatment of large areas, 30 to 40 cm on a side. This can be done quite easily with parallel opposing fields if one has a therapy unit with a reasonable output at 80 to 100 cm and a design which permits positioning of the patient at these distances. Otherwise, segmental therapy or some form of a trunk bridge must be employed. The most popular segmental technic is the M. D. Anderson system which has been described as the “horizontal moving strip” (1). More recently, a vertical moving strip technic has been described by Aral and Spira (2). These require fields of many different sizes and long periods of time to give relatively modest doses. An even less desirable method is the use of adjoining fields. This gives quite inhomogeneous depth doses because of the penumbra of the cobalt source. The method which we are currently studying is that of moving the patient under the open shutter of a cobalt therapy unit for distances up to 60 cm. This is done by first positioning a trans...

A Miniscan System Utilizing an Electro-Pantographic Display

In an attempt to improve radioisotope scanning, we are currently exploring a simple, inexpensive means of improving scan interpretation by minifi-cation and improved Teledeltos dot scanning. These methods, along with some of our early experience, are presented below. A rectilinear scanner with a 5-in. crystal, utilizing photorecording and dot presentation, was modified as follows: Two pantographs were installed by attaching them to the printing arm (stylus) of the scanner, both moving simultaneously with the motion of the scanning arm (Fig. 1). Each pantograph is equipped with a connection to the scanner output and has its own stylus. It is thus possible to perform scans of varying sizes by making simple adjustments of the pantographs. The scans printed out by the pantograph styluses will have identical data, but will be printed in a relatively smaller, although geometrically similar area. This technic alone has some interpretative advantages. Seltzer (1) noted the advantages of minifying scans. The impro...

Xeroradiography in transverse axial tomography for radiation therapy treatment planning.

Xeroradiography improves the quality of the image in transverse axial tomography, though the radiation dose to the patient is increased. This technique is useful for planning of radiation therapy in the head and neck region.