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S J Supe

Publications and source records attributed to S J Supe.

30 records · Page 2Linked to original sources
PubMed1979

Gap corrections for brachytherapy.

With discrete radiation sources, it is a deliberate treatment policy to provide gaps between two implantations of radioactive sources. Gap correction formulae have been arrived at to evaluate the ultimate biological effect on tissue. These formulae do not maintain the identity of the CRE and TDF concepts and hence Supe and Supe have chosen for external beam treatments appropriate gap corrections which maintain the equivalence of the concepts. During the continuous radiation therapy the tissue cells have a tendency to clump together in the sensitive phase and hence the radiation dose is more effective in this mode of treatment. Consequently the mathematical expressions for the CRE and TDFs for continuous radiation therapy differ from those for external beam therapy. The formula for complex treatment schedules of external beam therapy will not apply to those in brachytherapy, have been arrived at. In order to simplify the evaluation of the effective biological effects Tables for value of (T1+G1/T1)-0.155 and CRE0.71 have been prepared. The formulae developed for the resultant CREs and TDFs for the combination of brachytherapy treatments with gaps are different than those for combinations of external beam therapy. The powers of CRE and the terms of the type (T1+G1/T1) have changed appreciably.

Brachytherapy↗
PubMed1978

CRE for brachytherapy.

Various methods suggested in literature for estimating the ret dose for brachytherapy treatments do not provide unique answers to treatment scheduling problems. These schemes are reviewed with the aim to find out the cause of disparity and to suggest the most consistent system. The variability of the various schemes with the variations of the exponent of time is studied and the CRE system with its minimum variation is advocated for use in solving brachytherapy treatment scheduling problems. The average value of the exponent of time and the corresponding normalizing constant is used to evaluate CRE for brachytherapy fro various dose rates with increasing periods of treatments. Use of the CRE for solving treatment scheduling problems is simplified by providing ready made estimation of CRE for various dose rates and treatment times. A nomogram is devised which gives CRE values for various values of exponent of time.

Humans↗
PubMed1976

Dosimetry for irregular shaped fields of beta rays.

The feasibility of using various shapes and sizes of field limiting devices and collimators with beta-ray eye applicators has necessitated the study of dosimetry for these fields. A method of calculating surface and depth doses for any shaped field from the data for circular fields is presented. The depth dose evaluation is based on a measured dose function which is defined as the dose rate at a particular depth for a particular circular field. The evaluated values for the surface and depth dose were compared with experimentally obtained values for three non-circular fields. The good agreement in these data indicates the practicability of the method suggested.

Radiation Dosage↗
PubMed1976

Variation of CRE with exponents of time and number of fractions.

The concept of NSD has been modified into TDF's by Orton and Ellis and CRE's by Kirk et al. It was aimed to study the variability of these new concepts on the exponents of time and number of fractions. It was found that TDF has larger variation with the exponents compared to that of CRE. The use of CRE and NSD for solving the treatment scheduling problems or for intercomparison of various regimes has been simplified by providing readymade estimation of CRE for various doses/fraction with increasing number of fractions. As there is increasing evidence for the change of exponents J and H, nomograms are presented to determine the CRE for various values of J and H. The variation of decay correction factors with the exponent H is also evaluated and is presented. This will help various radiotherapists to use CRE and the decay correction factors consistent with their clinical findings.

Humans↗
PubMed1975

Dosimetry of spherical Sr-90-Y-90 beta ray eye applicators.

A modification of the conventional extrapolation chamber to perform absolute dose measurements from surfaces of spherical beta applicators (type SIA.I, SIA.3, SIA.6) is described. A stack of Ilford N 550 films has been used in a spherical geometry to obtain the variation of surface dose, the depth dose data and the isodose curves. The results obtained are compared with data available in the literature.

Eye Diseases↗
PubMedDate not supplied

Hazards to the eye lens and gonads from hard beta rays.

Considerable attention has been paid to the protection against x and gamma radiation but comparatively less stress has been given to the possible hazard due to external radiation from high-energy beta rays. In order to evaluate the magnitude of this hazard, central-axis depth doses at different source-to-skin distances for 90Sr-90Y and 32P sources were measured. Isodose curves in a testicular phantom for a 90Sr-90Y source were measured. The data of Haybittle for 144Ce for 10 cm SSD has been included. From the measured data, the eye-lens epithelium dose may be as high as 51%, 21.5%, and 82%, respectively, for the three sources instead of 15% as has been conventionally assumed. The isodose curves obtained in the testicular phantom indicate that an appreciable amount of testicular tissue can be subjected to radiation exposures. The radiation hazards due to high-energy beta rays are not negligible and considerable care should be exercised while using these sources.

Humans↗