Resolution Study of Ultrasound Reflections in Bovine Vertebral Bones In-Vitro

Abstract

Spinal fusion is the most common surgery to correct severe spinal deformities. It involves insertion of screws through the pedicles of vertebrae. Due to the serious neurological or vascular injuries caused by cortical perforation of pedicle screw insertion, an ultrasound imaging method has the potential to vision the spinal vertebrae and provide real-time guidance for the insertion. The objective of this study is to investigate the optimal frequency required to resolve the reflections from the closely-spaced layer interfaces. An immersion pulse-echo experiment was set up to study a bovine spinous process in-vitro. Two ultrasound frequencies (3.5 MHz and 5.0 MHz) were considered. The results of our preliminary study are very promising. All interfaces are clearly identified for both frequencies. Strong reflection signals are obtained when the beam is normal to the interface; otherwise, the echoes are weak or nonexistent. Thickness measurements between interfaces are comparable with those from the micro-CT image.