Dosimetric Implications of Number of Breathing Phases Used in the Definition of Internal Target Volume [ITV] in the Treatment of Non-Small Cell Lung Cancers Using Stereotactic Body Radiation Therapy (SBRT)

Determination of intrafraction motion in stereotactic body radiation therapy (SBRT) of non-small-cell lung cancer (NSCLC) usually involves generating an internal target volume (ITV) based on target segmentation in every one of the 10 phases of a 4-dimensional computed tomography (4DCT) dataset which increases dosimetry work load substantially. This study explores the feasibility of using a smaller number of phases to compile an ITV to get equivalent results.