Effect of ultrasound probe on dose delivery during real-time ultrasound-guided tumor tracking

Ultrasound is a noninvasive and less costly modality for real-time imaging of soft tissues. It has the capability of tracking soft tissue at levels of submillimeter precision even in the presence of radiation beams. The effect of a transducer on radiation dose is not fully known. The best imaging location for an ultrasound transducer happens to coincide with the path of an anterior-posterior beam in intensity modulated radiation therapy (IMRT). This study indicates a significant change in dose when this juxtaposition occurs. If the anterior-posterior beam is avoided in IMRT planning, however, the effect of the transducer on radiotherapy is found to be negligible.