Biomedical subjects

U B Tripathi

Publications and source records attributed to U B Tripathi.

8 recordsLinked to original sources

PubMed2005

Dosimetry parameters of BARC OcuProsta I-125 seed source.

A new model of 125I seed source, named OcuProsta seed, was designed and fabricated by Radiopharmaceuticals Division of Bhabha Atomic Research Centre for ophthalmic and interstitial applications. AAPM TG 43 recommended dosimetry parameters for this seed source were determined experimentally using TLD as well as by Monte Carlo (MC) simulation. Measured and MC calculated values of the dose rate constant (DRC) are 0.95 +/- 0.065 cGyh(-1)U(-1) and 0.972 +/- 0.005 cGyh(-1)U(-1), respectively. The mean of measured and calculated DRC (lambda = 0.96 cGyh(-1)U(-1)) was recommended for the clinical dosimetry of OcuProsta seed. Measured and MC calculated radial dose function, g(r), anisotropy function, F(r,theta), anisotropy factor and anisotropy constants are also found to be in good agreement to each other. Dosimetry parameters of OcuProsta seed were compared with the published values of similar in-design 125I seed sources. The DRC of BARC OcuProsta seed is very close to Amersham 6711 seed and is also comparable to the DRC of Best model 2301, Syncor PharmaSeed and Isotron selectSeed within the uncertainty of measurement/calculation. The g(r) of OcuProsta seed shows a difference of up to 10% in comparison to the g(r) values of the similar in-design seed sources. The values of anisotropy function of OcuProsta are 7-13% different from the anisotropy function of Amersham 6711 and Syncor PharmaSeed. The anisotropy constant of OcuProsta is close to Amersham 6711 seed while it is about 9% smaller than the anisotropy constant of Best model 2301 and Synchor PharmaSeed.

Algorithms↗

PubMed1993

Dose computation for irregular fields in cobalt-60 beam.

Dose computation in large irregular fields used for treating certain malignant tumors cannot be done by equivalent field methods. The present methods available for such dose computations are accurate but complicated and tedious and are amenable to only computers. This paper describes an algorithm (a semiempirical formula) of dose computation in an irregular field. Attempt is also made to estimate the dose outside the field border and in the shielded region. The dose values computed with this method at different depths in mantle and inverted Y-field in a cobalt-60 beam are compared with the experimentally measured values. The method proves to be simple and accurate. The calculations can be done even manually with a calculator and a statistical table in the absence of computer facility. It also successfully estimates the dose in the shielded region and in the penumbra.

Algorithms↗

PubMed1988

A simple computational approach to irregular field dosimetry.

Treatment of certain malignant tumors requires very large and irregular fields. The dose computations in such field configurations are quite complicated and tedious and hence accessible to computer methods only. This paper describes an easy method for estimating dose to any point in such irregular fields except those which are in the shielded region. For radiotherapy centres which do not have access to a computer, this paper presents an algorithm that can be used with a desk calculator for dose computation at any point. The dose values calculated using this algorithm at different points and at different depths in the mantle and inverted Y-fields agree within +/- 3% with the values computed using detailed sector integration method of Clarkson.

Algorithms↗

PubMed1980

Formulae for TAR and SAR calculation for Co-60 beam.

Tissue-air ratio (TAR) and scatter-air ratio (SAR) are very important concepts in radiation dosimetry. In absence of any analytical relation for computation of these quantities a number of empirical equations have been fitted to experimentally measured data. This paper describes the derivation of analytical formulae from first principles. The resultant equations are very simple and can even be evaluated with the help of a slide rule. The computed values of TAR and SAR agree within 1% with the experimental data of Gupta and Cunningham (1966).

Air↗

PubMed1980

Formulae for contour and inhomogeneity correction.

Standard data for treatment of the patient are usually obtained in a large homogeneous phantom having a flat surface, and the radiation beam is made to be incident normally on it. The actual patient is neither homogeneous nor has a flat surface. This paper derives suitable expressions--using the total dose formula of Tripathi and Kelkar--for correcting the obliquity of the body surfaces and inhomogeneities such as bone, lung, etc. inside the body. The results obtained thus compare very well with the experimentally measured data. These equations are very simple and can readily be used with standard data to yield corrected dose distributions.

Bone and Bones↗

PubMed1979

A simple formula for depth dose calculation for Co-60 teletherapy beam dosimetry.

Knowledge of dose at all the points of interest, in the plane of tumour, is essential for treatment planning. A very simple formula for scatter dose calculation along the central axis of a Co-60 beam has been derived. This formula uses primary dose at depth d, scatter air ratio at the depth of maximum ionisation and the effective depth of the volume, irradiating the medium. The method for calculation of percentage depth dose at any point in the principal plane has been explained in detail. The simple form of the formulation will help in improving the treatment plans for treatments of lesions using Co-60 teletherapy machines.

Cobalt Radioisotopes↗

PubMed1975

Use of tissue-to-air ratio in computation of specific absorbed fraction.

This paper describes a new approach for computing specific absorbed fractions that can be used for estimating doses that result from the internal administration of radiopharmaceuticals. This approach uses the concept of the tissue-to-air ratio (TAR) which can either be calculated or experimentally determined for the radionuclides of interest. Good agreement exists between the specific absorbed fraction values obtained using measured and computed values of TAR. This implies that the measured values of TAR can be used to obtain specific absorbed fractions for all radionuclides.

Absorption↗

PubMedDate not supplied

A general formula for computation of tissue-air ratios for radionuclides commonly used in brachytherapy.

Tissue-air ratio values for different radionuclides have been computed from first principles. The computed data have been used to derive a general formula applicable to most commonly used radionuclides in brachytherapy. There is good agreement between the values obtained from the present formulation and other reported values. For depths beyond 10 cm, no reported values are available for comparison, but on the basis of the self-consistency of the formalism it is reasonable to expect the accuracy of the computed values to be within +/- 2% at any depth up to 30 cm.

Brachytherapy↗