Determination of total activity and its distribution in cathetron source pencils.

High intensity remote-controlled afterloading devices such as Cathetron, employ tiny source elements which facilitate free movement through the curvature of the guide tubes. As the activities involved are in the curie level and a number of sources are assembled together in the form of a pencil, conventional methods cannot be employed for determining the activity of individual sources. This paper deals with the determination of the total activity of a source pencil from the measured exposure rate and an autoradiographic method used to determine the activity of individual sources.

Dosimetry of cathetron applicators in intracavitary therapy.

Theoretical computations have been done to obtain dose distributions in the paracervical and sagittal planes for various loadings of Cathetron applicators. Uterine catheters of various sizes and shapes and various loadings of ovoid catheters have been considered for the dosimetry. Experimental measurements have been made to verify the computed dose distributions. The computed dose distributions have also been compared with those of a conventional Manchester loading. Although the ratio of dose contribution to point A from vaginal sources to that from the uterine sources is found to be significantly different for Cathetron therapy from the conventional Manchester system, the isodose distributions in the paracervical plane are in good agreement. However, the differences in the isodose distributions in the sagittal plane indicates a higher dose to the rectal region for Cathetron therapy, which can be reduced by the use of rectal retractors.

Clinical dosimetry of the rectum in cathetron applications for treatment of carcinoma of the uterine cavity.

Rectal dose measurements have been carried out for 60 patients undergoing Cathetron therapy for the treatment of carcinoma of the uterine cervix at the Cancer Hospital, Indore. The measurements show that the maximum rectal dose occurred around 8 cm from the anal verge. In most of the cases (approximately 75%) the maximum rectal dose lies between 50 and 85% of the dose at point A. The combined biologically effective doses from intracavitary and external beam therapy regimes in this centre and the clinical complications have been compared with those of other centres. Although no immediate serious rectal complications have been observed, it is desirable to check the rectal dose using monitoring source pencils, so that the applicators and rectal retractor can be readjusted, if necessary, to minimise the dose.

Carcinogenic effect of radiation on the mouse embryo; physical aspects of radiation dosimetry.

The doses received by the embryos from abdominal irradiation of the females at the time of pregnancy may adversely affect the offspring. The dose to the embryo will depend on the depth of the embryo from the surface, the distance of the embryo from the central axis of the beam and on the photon energy. A knowledge of the dose as well as the percentage depth dose in this region will be necessary for the meaningful correlation between the radiation dose and the neoplasm formation due to prenatal irradiation. This paper presents the results of our experimental investigation of the percentage depth doses in a mouse phantom. The results of theoretical computation of percentage depth doses to off-axis points are found to be in good agreement with the experimental values.