A spreadsheet to determine the volume ratio for target and breast in partial breast irradiation

Abstract

The technical feasibility of Partial Breast Irradiation (PBI) using external beam radiotherapy depends on the ratio between the evaluation planning target volume (PTV-eval) and the whole breast volume ("PBI volume ratio" = PVR). We aimed to develop a simple method to determine PVR using measurements performed at the time of the planning CT scan. A PVR calculation tool was developed using a Microsoft Excel spreadsheet to determine the PTV from three orthogonal dimensions of the seroma cavity and a given margin on the CT scans. The breast volume is estimated from the separation and breast height in five equally spaced CT slices. The PTV-eval and whole breast volume were determined for 29 patie..