Journal of Medical Physics 1994 19(2):55-58

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Journal of Medical Physics 1994 19(2):59-63

A retrospective analysis of 291 patients with cancer of the uterine cervix treated with a combination of external and intracavitary radiotherapy was carried out. Patients were treated with external radiotherapy dose of 45 Gy in 20 fractions, 5 fractions per week or 42 Gy in 14 fractions, 3 fractions per week. For brachytherapy the total dose was 24 to 32 Gy at a dose rate of 1.4 to 2.2 Gy per hour. Treatment results in terms of response, survival, recurrence and complication were correlated with Time Dose Fractionation (TDF) and Extrapolated Response Dose (ERD) values for point A(TDFTA and ERDTA) and for rectum (TDFTr and ERDTr) respectively. TDFTA and ERDTA values did not correlate with response, recurrence and survival rates (p value> 0.05). Correlations of TDFTA and ERDTA with overall complication rate (p value < 0.05) and with rectal complication rate (p value c 0.025) were excellent. Lack of correlation was observed between TDFTr and ERDTr for overall complication rate (p value> 0.1) and rectal complication rate (p value> 0.1). In the same group of patients, both models that have been used in this study showed statistically significant correlation in the assessment of overall and rectal complication rate. In order to limit Grade II and Ill rectal complications to acceptable level, in combined external and intracavitary treatments, TDFTA and ERDTA values of less than 151 and 93 respectively are suggested.]]>

Journal of Medical Physics 1994 19(2):64-69

To increase, the tumour control in advanced head and neck cancers, combined treatment modality like radiotherapy-chemotherapy has been in practice. A chemotherapeutic drug methotrexate has been used along with radiotherapy. The tumour regressions and normal tissue reactions with the combined mode of therapy have been compared with that due to radiotherapy alone. Time dose fractionation concepts of CRE, TDF, ERD were applied to the data. The changes brought about in the a/B values due to the combined action of radiotherapy and methotrexate are obtained from the data. The concept of Radiation Equivalent Chemical (REC) of environmental pollution has been extended to these combination treatments and is termed as Gray Equivalent Chemical (GEC). The patients receiving radiotherapy alone (control group) were treated using 25 to 30 fractions of 2 to 2.2 Gy given once a day with five fractions per week. Experimental groups were given 2.5 mg of methotrexate 2 hrs before the radiation dose. A dose of 2.25 Gy was delivered once a day and total dose was 45 Gy in 20 fractions in four weeks.]]>

Journal of Medical Physics 1994 19(2):70-73

The dose effect equation developed through the polynomial model as proposed in our earlier communication, has been found to be capable of providing a number of new insights into the clinical radiotherapy. In this paper we have proposed a graphical method for the application of dose-effect equation of the polynomial model to fractionated radiotherapy. The main features of the method are demonstrated with the help of suitable worked examples.]]>

Journal of Medical Physics 1994 19(2):74-77

The linear quadratic (LQ) model has recently been modified by incorporating a time factor. The modified LQ (MLQ) model has a number of applications in which the alterations of dose per fraction in fractionated radiotherapy may be used to bring out improved results with respect to early / late normal tissue and tumour reactions. In this paper, the MLQ model is used to determine the total dose for early / late normal tissue reactions and tumour response. The normal tissues are classified in three main groups on the basis of their reactions. Different values of a1 / a2 and k are used for the three groups of normal tissues and tumours to calculate the equivalent total doses for various treatment regimes.]]>

Journal of Medical Physics 1994 19(2):78-82

Quality assurance (QA) in brachytherapy is as important as quality assurance in external beam radiation therapy. Not much literature is available on QA of PC-based treatment planning systems to improve the accuracy of dose computations. In this paper, some useful quality assurance tests for brachytherapy are suggested for proper evaluation and use of treatment planning systems (TPS).]]>

Journal of Medical Physics 1994 19(2):83-85

Four patients with Stage I carcinoma of the penis were treated with radical external beam radiotherapy using individualized wax bolus. All patients are alive and doing well at the time of this report, 2 years after treatment. No patient had local recurrence and all had preservation of the organ and its function. Radiotherapy can be used as an alternative modality to surgery especially in the early stages of penile cancers.]]>

Journal of Medical Physics 1994 19(2):86-90

Detection of kinematically subtle coronary artery disease (CAD) is quite difficult when there is normal global left ventricular ejection fraction response to supine ergometric (isotonic) exercise. A new index of 'left ventricular synergic pumping efficiency' (LV-SPE) has been defined conceptually and mathematically. Hand-grip (isometric) stress induced change of LV-SPE has been found to be a very useful parameter in detecting CAD in the presence of minimally produced wall motion abnormalities, which are liable to be otherwise scintigraphically too blurred when evaluated by isotonic exercise methods and thus evade proper analysis.]]>

Journal of Medical Physics 1994 19(2):91-92

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