Ultrasound Propagation Velocity in Porcine Trabecular Vertebral Bone Following Single-Dose Stereotactic Radio Surgery
Julie P. Griffin, Paul M. Medin, Edmond Richer

Abstract
Recently, there has been a move towards single-fraction SRS treatments with doses as great as 24 Gy. This increase has resulted in concerns due to the increased rates of late onset vertebral fractures, possibly indicating that the maximum tolerance to radiation has been exceeded. The long-term effect of SRS on the structural integrity of bone is still unknown. This study uses Ultrasound Propagation Velocity (UPV), predictive of mechanical strength, as an indicator for changes in bone properties. SRS was administered to four Yucatan minipigs at 16 - 18 Gy from the fourth to the sixth cervical vertebrae, focused on half the vertebral body in the medial-lateral direction. The UPV was found to be statically different between the halves of irradiated vertebrae, absent in the non-irradiated vertebrae. These results infer that current accepted doses for single-fraction SRS do cause changes in the mechanical properties of bone.

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