Clinical application of a CT based treatment planning system

An AECL (TP-11) treatment planning system has been modified to allow multiple CT scans to be used directly for dosage calculation and display. This CT/TP-11 system has incorporated the "equivalent tissue-air ratio method" to make corrections for the effects of tissue heterogeneity and the three-dimensional nature of patient shape. In test situations, using an anatomical phantom, an accuracy of ca. 2% has been attained. An investigation has also been made to assess the importance of the reproducibility of patient position and its effect on the validity of such dosage calcualtions. When representing an advance in sophistication of existing facilities, this system has also been designed with practically in mind.