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.