Role of gastrointestinal ultrasound in image-guided radiation therapy: A review

Radiation therapy is one of the main modalities for cancer treatment. New radiotherapy techniques provide conformal radiation dose distribution and need higher accuracy in treatment delivery. Internal organ motions and displacements between and within the radiotherapy treatment fraction affect and weaken the reproducibility of delivering the planned irradiation to the target position. Image-guided radiation therapy (IGRT) can be used as a critical technology to improve patient positioning accuracy and reduce uncertainties in tumor target definition during treatment delivery. Ultrasound, a non-invasive imaging technique, is one of the important modalities in IGRT for accurate pre-treatment patient positioning and fiducial marker placement. The current study purposed to summarize recent advancements in ultrasound applications, techniques, and possible use in radiotherapy for cancers located in the abdomen and pelvic regions. We hope to give the readers a comprehensive understanding of the emerging clinical ultrasound-based IGRT applications and techniques.