A study on the rotational therapy employing 60-Co teletherapy unit with aluminum therapy table

Kim, C H; Moon, Philip S

Abstract

A study was made on the dose rate calculation of the rotational 60 Co teletherapy, employing aluminum therapy table which has no known dimensions of the table thickness. Two methods were used in order to determine the thickness of aluminum therapy table. One was by estimation of table thickness and the other was by measurements of radiation dose rates. These two results wre compared and found to be in good agreement. For the radiation dose rate measurement, paraffia wax phantom and patients of carcinoma of the utrine cervix were employed. Since paraffin wax was known to be a tissue-equivalent materia, the results of measurement for both objects were in good agreement, and the measurements with phantom were justified. The calculation method of the dose rate on the 60 Coteletherapy was thoroughly explained in order to use for the calculation of the axis dose rate with and withoutaluminum therapy table. Two equations for the correction of the axis dose rate through the aluminum therapy table were derived for most frequently used angle positions, and also an equation for conversion from aluminum thickness to tissue-equivalent material thickness was derived for Tissue-Air-Ratio calculation of 60 Co teletherapy.