IGRT induced dose burden for a variety of imaging protocols at two different anatomical sites

BACKGROUND AND PURPOSE: Increase in positioning accuracy and treatment adaptation is supported by image guidance. The downside is the concomitant imaging dose. In this study, we report on the total dose picture for different styles of image guidance.

MATERIALS AND METHODS: Dose was measured in the Alderson phantom using TLD's. IGRT technology investigated included CBCT at the linac and simulator, multislice-CT and kV and MV planar imaging. Clinically used imaging protocols were applied and the total dose picture was assessed for four different sequences of imaging for a prostate and a head and neck treatment.

RESULTS: The different imaging geometries for the various imaging modalities resulted in fairly different dose distributions. Head and neck doses up to 100 mGy and higher were found for portal imaging and multislice-CT. Depending on the IGRT sequence used maximum total dose varies between 120 and 1500 mGy. In prostate maximum doses between 40 and 100 mGy were found for portal imaging and CBCT at the linac. Here the maximum total dose varies between 120 and 2250 mGy depending on the sequence used.

DISCUSSION: Factors like patient dimensions, age and sex can influence the applicability of presented values. Careful consideration of imaging dose especially for very intense imaging sequences is recommended.