Plan Quality Index – An Integrated Dosimetric Approach for Plan Evaluation with Consideration of Quality of Dose Coverage to Tumors and Quality of Organs’ Sparing

Abstract

Purpose: To find an integrated solution for plan evaluation with multiple dosimetric parameters in order to ensure quality of target dose coverage and sparing of organs collectively. Materials and Methods: A mathematical logical expression called Plan Quality Index (PQI) was formulated. It includes two integrated indices 1.Integrated Dosimetric Index for tumor (IDITumor) dose coverage and 2.Integrated Dosimetic Index (IDIorgans) for Organs At Risk (OARs). PQI was used to select better dosimetric plan form multiple VMAT plans of a Nasopharynx case. In addition, the PQI was used for comparison of VMAT and IMRT plans of 64 patients with Head and Neck cancer. The plan with lesser PQI was considered as a better dosimetric plan. For statistical comparison between two techniques, paired‘t' and Wilcoxon signed rank test were used with consideration p< 0.05 as a statistically significant. Results: The unambiguous evaluation results with PQI showed that VMAT plan was achieved the entire given dose constraints significantly better than IMRT plan in all the patients (p<0.001). Conclusion: Plan evaluation with PQI can be an unambiguous method. It evaluates the quality of tumor dose coverage (IDITumor) and sparing of OARs (IDIorgans) collectively. It enables to change the priority of evaluation criteria of a specified structure based on the clinical requirements. It does not require any specialized program. It can be calculated using ordinary excel program. Using the single value as PQI, the effective determination of a quality plan among many plans can be possible and it can be used for comparison of different techniques.