AbstractID: 10105 Title: Managing the Imaging Dose during Image-Guided Radiation
Therapy
Radiographic image guidance has emerged as the new paradigm for patient positioning, target localization, and external
beam alignment in radiotherapy. Today, image-guided radiotherapy (IGRT) can involve 3DCT for treatment planning, fluoroscopy
and 4DCT for pre-treatment motion assessment, daily in-room CT for setup and evaluation of anatomical changes, and intra-fraction
x-ray imaging for target tracking. All of these image guidance techniques give a radiation dose to the patient. Consequently, the
adoption of IGRT methods has led to a significant increase in the patient’s concomitant radiation dose. Whereas the therapy dose has
always been analyzed in detail, in the past only cursory attention has been paid to imaging dose. It is now important for clinical
practitioners to pay close attention to the accumulation of imaging dose. The AAPM has recognized the importance of imaging dose
management by supporting Task Group 75’s report on the subject. This review is condensed from that report. Its purpose is to enable
the clinical practitioner to approach imaging dose with the same quantitative rigor as the therapeutic dose.
The educational objectives are the following:
(1) illustrate the varieties of transmission imaging in IGRT (emission imaging such as PET and SPECT will not be included);
(2) review the methods and issues in imaging dose estimation;
(3) summarize the characteristic doses associated with various imaging modalities and configurations;
(4) present the methodology for summing dose from multiple modalities;
(5) discuss the evaluation of risk;
(6) review dose management strategies.