Determination of PTV and ITV Margins for Pelvic Lymph Nodes Irradiation in Prostate Cancer Patients Using Multiple CBCT Imaging

Abstract

Pelvic lymph nodes (PLN) are commonly irradiated in men with prostate cancer. Based on the ICRU definition, the Planning Target Volume (PTV) margin added to the Clinical Target Volume (CTV) can be divided in a movement related Internal Margin (IM) and a Setup Margin (SM). Traditionally, it was assumed that PLN moved closely with bone structures. Image Guided Radiotherapy (IGRT) now enables a more precise bony anatomy positioning, reducing SM. Hence, the IM has a stronger relative impact on the PTV margin.