Combined ultrasound and computed tomography for image‐guided acoustic therapy

Fusion of computed tomography (CT) and ultrasound (US) imaging is currently used for guiding interventional procedures, including biopsy, local drug delivery, and radiofrequency ablation. While US facilitates real‐time visualization of blood flow and tissue structure, CT provides a 3‐D view of an extended region of interest, can differentiate tissue types, and operate in a fluoroscopic mode for catheter placement. Our laboratory is working to extend this fusion to include US therapy and imaging co‐registered with CT. Here, we present methods for semi‐automated registration between tracked US and CT with the objective of imaging and guiding acoustic therapy in small animals. A calibration phantom and fiducial markers were used to generate accurate transformation between the real‐time US and pre‐acquired CT image stack. The mean error in the transducer calibration was 1.1 ± 0.76 mm with a maximum error of 3.1 mm. A target registration error of 1.7 ± 0.9 mm was observed in US and CT images of a dual‐modality...