Real-time monitoring the alignment of x-ray beam relative to treatment target during radiation treatment based on ultrasound and x-ray acoustic dual-modality imaging (Conference Presentation)

Abstract

The strategy of Intensity-modulated radiotherapy (IMRT) is to deliver precise radiation doses to targeted area while minimizing the dose to surrounding healthy tissue. The intrafractional variations such as the movement of the patient or the respiratory motion, which most likely to cause misalignment during a session of radiotherapy, may compromise the outcome of the detailed dose delivery. This study examines the feasibility of real-time monitoring the alignment of the X-ray beam relative to treatment target during radiotherapy based on ultrasound (US) and X-ray acoustic (XA) dual-modality imaging. A dual-modality imaging system, which utilizes the US phase array for both US imaging and XA signal acquisition, was established based on the Verasonics US system. 2D US image achieved can be used to locate the target cancerous tissue, while 2D XA image acquired will show the shape and location of the X-ray field inside the same imaging plane quasi simultaneously. A phantom holding a large piece of veal liver, where parts of the liver tissue were removed from the middle and embedded with different types of bio-tissues (muscle, fat or kidney), was shot by the beams generated and modulated by a medical linear accelerator. The fusion images integrated with XA and US images quantitatively demonstrated whether the X-ray beam was delivered to the embedded bio-tissue with any mismatch in its shape or any shifts off the accurate position. The experiment results suggest that the US-XA dual-modality imaging is a potential tool for real-time monitoring the geometric alignment during radiotherapy.