Design of a Linear Flexible Ultrasound Array Transducer for Real-time Tracking of the Scaphoid during Percutaneous Scaphoid Fixation

The scaphoid, accounting for over 90% of all carpal fractures, is the most commonly fractured bone in the wrist. Percutaneous Scaphoid Fixation (PSF) is a minimally invasive technique commonly employed for scaphoid fracture repair. However, the position of the scaphoid can vary with the motion of the hand during PSF, complicating the intervention. As such, real-time ultrasound motion tracking of the scaphoid during PSF could facilitate the intervention but would require a flexible transducer array to maintain contact during wrist motion. Flexible transducers offer a wider field of view and can be conformed during the procedure, reducing the impact of patient movement on image quality and tracking accuracy. This work presents a parametric simulation study to design an ultrasound array suited for tracking the scaphoid during PSF. Multiple linear arrays were simulated in k-Wave to image a CT-extracted scaphoid bone model moving at an imposed rotational velocity. The design with a center frequency of 7.5 MHz and element pitch of 1.5λ was found to provide a good compromise between tracking error and image contrast.