An Endoscopic Concentric Ring Sector-Vortex Ultrasound Phased Array Applicator for Pancreatic Tumor Ablation

An endoscopic ultrasound phased array applicator is introduced, consisting of a phased array transducer enclosed in a distensible reflector balloon that is filled with water. The applicator can be collapsed for delivery and expanded close to the target position to enhance its therapeutic capabilities. Acoustic and biothermal simulations were performed for a 64-element cylindrical phased array transducer composed of 8 tubular transducers, each divided into 8 sectors, in water medium and 3D generalized tissue medium. The transducer-reflector design mimics the focal quality of a large diameter combined concentric-ring sector-vortex phased array. Simulation results indicated that transducer arrays (1.5 MHz, 9 mm OD x 20 mm length, 8 rings, 8 sectors), balloon sizes (42 - 50 mm expanded diameter, 20 - 60 mm focal depth), phasing mode (0 - 4) and sonication durations (120 s) can produce spatially-localized focal intensity patterns (Axial FWHM: 3 -19 mm, Transverse FWHM: 2 - 8 mm) and ablative thermal lesions (width: 3.6 - 27 mm, length: 5 - 22.5 mm) in generalized pancreatic tissue across a 20 - 70 mm depth range. The results of this study demonstrated the feasibility of a novel ultrasound applicator design that can be collapsed for compact endoluminal or laparoscopic delivery and deployed close to the target to emulate a large concentric-ring sector-vortex phased array capable of focusing, deep penetration, electronic steering and volumetric thermal ablation.