Quantitative metrics for assessing IMRT plan conformity: A virtual phantom study

Abstract

Intensity Modulated Radiation Therapy (IMRT) is a complex form of radiation delivery for the treatment of malignant tumours and other diseases. In IMRT treatment planning, quantitative assessment is crucial to measure and improve the plan quality and treatment delivery. The search for simple and universal quantitative metrics to assess IMRT treatment plan quality has been identified as important, but as yet not entirely successful. The aim of this study was to assess the IMRT treatment plan quality from the perspective of planning conformity. Conformity index (CI) was adopted to quantify the plan conformity. Virtual phantoms were developed for the initial conformity assessment, in order to form a basis for treatment plan inter-comparisons amongst the different IMRT techniques. A series of multi organs at risk (OARs) phantoms was developed to simulate the planning target volume (PTV) and OARs for different configurations. Conformity assessments were undertaken on all the IMRT plans generated using the virtual phantoms. This study has demonstrated the successful development of virtual phantoms to assess objectively and systematically the IMRT treatment plan conformity.