Verification of Monitor unit calculations for eclipse Treatment Planning System by in- house developed spreadsheet

Computerized treatment planning is a rapidly evolving modality that depends on hardware and software efficiency. Despite ICRU recommendations suggesting 5% deviation in dose delivery the overall uncertainty shall be less than 3.5% as suggested by B.J. Minjnheer. J. In house spreadsheets are developed by the medical physicists to cross-verify the dose calculated by the Treatment Planning System (TPS).
The monitor unit verification calculation (MUVC) verification was tested for pre-approved and executed treatment plans taken from the TPS. A total of 108 square fields and 120 multileaf-collimators (MLC) shaped fields for Head & Neck cancers, cervical and esophageal cancers were taken for evaluation. In house developed spreadsheet based on Microsoft Excel was developed. The dose calculation parameters such as Output Factor (O.F), Percentage Depth Dose (PDD) and off axis ratio (OAR) data were taken from the TPS.
The overall MU ratio fell within the range of 0.999 to 1.02 for square field geometries showing deviation of 1% between the TPS calculation and the spread sheet calculation. The MU ratios were 0.995 for Head & Neck plans & 1.012 for cervix plans with the standard deviation of 0.024 & 0.029 respectively. However we observed the mean MU ratio for Esophagus plan was 1.026 with the standard deviation of 0.040.
The spreadsheet was tested for most of the routine treatment sites and geometries. It has good agreement with the Eclipse TPS version 13.8 for homogenous treatment sites such as head &and neck and carcinoma cervix.