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S J Supe

Publications and source records attributed to S J Supe.

14 recordsLinked to original sources
PubMed1992

Predictive role of TDF values in late rectal recto-sigmoid complications in irradiation treatment of cervix cancer.

Radiation-induced late rectal and recto-sigmoid complications for different doses per fraction were analyzed retrospectively in 203 cases of Stage IIIB carcinoma of the uterine cervix. The patients were treated with a combination of external irradiation and a single intracavitary insertion during January 1979 to December 1983. The external irradiation was randomised to deliver by four different fractionation regimens having dose per fraction of 2 Gy, 3 Gy, 4 Gy and 5.4 Gy. The doses for various fractionations were matched with the daily regimen using the time-dose factors (TDF) model. A single intracavitary insertion delivered a dose of 22 to 24 Gy to point A using Fletcher-Suit applicator. All patients had a minimum follow-up of 30 months. Thirty nine cases of late radiation induced rectal and recto-sigmoid complications were observed. The complication rate of 8.2% for daily treatment regimen delivering 2 Gy per fraction was increased to 33.3% for once weekly treatment regimen delivering 5.4 Gy per fraction (p = 0.041). Despite similar Time-Dose Factors (TDF) values in four different treatment regimens, the complication rate increased significantly in the once weekly regimen. The analysis suggest that the Time-Dose Factors (TDF) values do not predict correctly the late normal tissue reactions for different dose fractionation schedules.

Adult↗
PubMed1992

The predictive role of bioeffect dose models in radiation-induced late effects in glottic cancers.

Late radiation-induced laryngeal oedema for different doses per fraction was analyzed in 208 cases with squamous cell carcinoma of the vocal cord. The series comprised 156 cases with T1N0M0 and 52 cases with T2N0M0 lesions. Radical radiotherapy was given with three different regimens delivering 3.33 Gy, 2.5 Gy, and 2.25 Gy per fraction. There were 52 cases of late radiation-induced laryngeal oedema. A strong correlation (p less than 0.015) between the dose per fraction and the risk of the late complication in the vocal cord has been demonstrated. The analysis suggests that the empirical models like Nominal Standard Dose (NSD) or Time-Dose Factors (TDF) do not predict correctly the late normal tissue reactions for different dose fractionations. The analysis with extrapolated response dose (ERD) values of the linear-quadratic (L-Q) model also fail to correlate with the late complications (p greater than 0.5). Care should be exercised when using these bioeffect dose models to calculate regimens iso-effective for late damage, even when modest changes in fraction size from 2 to 3 Gy are contemplated.

Carcinoma, Squamous Cell↗
PubMed1991

Treatment of keloids by 90Sr-90Y beta-rays.

The use of radiations for the treatment of keloids was the topic of debate for years. Because of the benign nature of the keloids, surgery (keloidectomy) was treatment of choice. However, the use of surgery alone for arresting the keloids growth does not give satisfactory results due to the high frequency of recurrences. In this study 110 symptomatic cases were treated with 90Sr-90Y beta-radiation either alone for flat keloids or in combination with surgery for thick keloids. The results obtained with this method were found to be quite satisfactory. Patients were given four fractions of 5 Gy per fraction either as weekly or twice weekly schedules. Radiation dose of 2000 cGy given twice weekly in four fractions showed response in 86% of the cases as compared to 73% in those receiving four fractions of 5 Gy weekly. Further observations on different time dose fractionation schedules would open up newer dimensions in the radiotherapy of keloids.

Adolescent↗
PubMed1991

Importance of dose per fraction and estimation of an alpha/beta value for the late complications of the vocal cord.

The incidence of late complications for different sizes of dose per fraction is analysed in 208 cases with squamous cell carcinoma of the vocal cord. The series comprised 156 cases with T1N0M0 and 52 cases with T2N0M0 lesions. Radical radiotherapy was given with three different regimens having dose per fraction of 3.33 Gy, 2.5 Gy and 2.25 Gy. There were 46 cases of late radiation induced laryngeal oedema. Using this clinical data an alpha/beta value of 2.35 +/- 0.13 Gy was estimated for late complications of the vocal cord. It was found that there is strong correlation between size of dose per fraction and the risk of late complication in the vocal cord.

Carcinoma, Squamous Cell↗
PubMed1990

Dose equivalent response of a TLD badge--influence of body backscatter.

In personnel monitoring, operational quantities recommended by ICRU Publication No. 39 for photon radiation can be realized by calibrating dosimeters on a phantom and considering body backscatter photons by using established conversion factors. Personnel dosimeters used in this study are based on CaSO4:Dy Teflon thermoluminescence dosimeter discs (TLD) that have a highly photon energy-dependent response. Since body backscattered photons have lower energies than the incidence photons, methods for correcting for energy dependence of both the incident and body backscattered photons have to be developed. By using readouts of two TLD discs (one under a composite metal filter and the other without a metal filter) in an empirical relation valid at all energies, it is possible to correct for the effect of change in response from change in the photon energies. It was found that the new operational quantities recommended by ICRU could be estimated to within +/- 15% by a TLD badge design based on this method. Angular dependence limits for photons in accordance with the new international standards and a high beta dose-equivalent discrimination in the mixed fields of beta and low-energy x rays could also be achieved.

Equipment Design↗
PubMed1979

Isoeffect lines using TDF and CRE concepts.

In most of the radiotherapy centres the treatment planning is based on isodose lines. Isoeffect lines are also being drawn based on the concepts of TDFs and CREs. It was aimed in this work to find out whether the isoeffect lines based on the concepts of TDFs, CREs and the physical isodose lines are identical in all the treatment situations. Isoeffect lines for a few treatment schedules involving treatment of carcinoma of the bladder, treatment of cancer of the uterine cervix by combined intracavitary and external beam therapies and intracavitary therapy alone have been obtained and compared in the present study. The effect of treatment mode on the isoeffect lines is also studied. It is found that the isodose curves and the isoeffect lines using the TDF and CRE concepts are not identical in all situations. Therefore, the ultimate treatment plans based on theses isoeffect lines will not be exactly the same. The dependence of the isoeffect lines with the variation of the exponents of time and number of fractions used in the empirical relationship for NSD have also been investigated. Clinical trials have been initiated in the case of cancer of the bladder and cervix uterus based on the isodose curves and the isoeffect lines using CRE and TDF concepts.

Cobalt Radioisotopes↗
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↗