Reduction of ultrasound propagation velocity in porcine vertebrae following stereotactic radiosurgery

• Published in: The Journal of the Acoustical Society of America Vol. 128; no. 4_Supplement; p. 2363
• Main Authors: Pollard, Julie E., Steinmann-Hermsen, Jessica, Medin, Paul M., Boike, Thomas, Richer, Edmond
• Format: Journal Article
• Language: English
• Published: 01-10-2010
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.3508386

Vertebral metastasis occurs in over 100 000 individuals in the United States. Stereotactic radiosurgery (SRS) has helped cancer patients with disabling pain. Over the last 10 years, the use of spinal SRS grew exponentially and typical dosage increased significantly from 10–12 Gy to 16–22 Gy. Yet the tolerance of the vertebrae to high doses of radiation is poorly understood, and the increase in dosage resulted in a correlated rise in vertebral fracture. Yucatan minipigs were radiated with doses 16–18 Gy from third to sixth cervical vertebrae. Radiated volume was parallel to spine and focused on half of the vertebral body, resulting in high dose and low dose irradiated regions. Cubic samples were obtained from the two halves of the irradiated vertebrae 1 year after SRS. Control samples were obtained from nonradiated vertebrae. Ultrasound propagation velocity in bone is an indicator of its mechanical strength. Velocity was measured by correlation with a reference wave, obtaining the phase shift using Hilbert transform. Consistently, high-dose irradiated specimen exhibited a reduction in ultrasound velocity between 1.2% and 15.4%, with an average of 6.9%. Young’s modulus was reduced on average by 15%. This research could provide indicators for safe, effective doses in clinical SRS.