Comparative analysis of stereotactic radiosurgery treatment plans in brain cases with one and two tumour changes using conformity indices

Abstract

Aim

To analyse (quantitatively-statistically) conformity indices calculated for stereotactic radiosurgery treatment plans with one and two isocentres in cases of brain tumour.

Materials/Methods

A retrospective study of 33 patients with brain tumours treated between April 2005 and January 2006 was performed in the Radiotherapy Department of the Oncology Centre in Łódź. Stereotactic surgery was performed in all patients. All treatment plans were divided into two groups: plans with one isocentre and plans with two isocentres. For each treatment plan various kinds of conformity parameters were calculated and optimal prescription isodose level was determined.

Results

All conformity indices are within ranges and were accepted. Their values are lower in plans with two isocentres in comparison to plans with one isocentre.

Conclusions

Conformity indices are very helpful in the analysis of treatment plans, but they do not give real insight into all aspects of plans. Prescription isodose should completely enclose PTV volume. Optimal prescription isodose does not cover PTV; thus from a clinical point of view it is inapplicable.