The optimization of ultrasound measurement methodology for the detection of the effect of radiation on porcine vertebrae.

摘要

Each year, vertebral metastasis occurs in over 100,000 individuals in the United States. Stereotactic Radiosurgery (SRS) has provided positive results to help suffering cancer patients with their disabling pain. The increase in the familiarity of spinal SRS has allowed physicians to feel comfortable with raising the dosage in the last ten years. Unfortunately, a rise of vertebral fracture has paralleled this change in treatment. Ultrasound provides a non-invasive, non-destructive technique for measuring the strength of the bone based on the ultrasound velocity through the bone. In this study, previous methods for measuring the ultrasound velocity through a material were examined and calibrated specifically for the desired biological application.;A systematic approach for the calibration of the measurement methodology began with the investigation of varying test materials. It was concluded that having a reference wave when measuring the transient time of ultrasound through a material is imperative because of the amount of error that is eliminated. The relationship of the sample size and the wavelength of the propagating ultrasound wave were explored. It was determined that the most accurate ultrasound velocity results were found when the ultrasound wavelength was around the same size as the specimen, meaning that a high frequency (5 MHz) gave the best results.;The study continued with the porcine biological application. Swine have shown to be strong biological models for humans. Four Yucatan Minipigs were irradiated in their cervical spine at specified dosages. Once sacrificed, the physical effects of the SRS on the vertebrae could be visually observed. The ultrasound velocities were determined for the irradiated bone specimens. At 5 MHz, the bulk wave velocity in addition to the compression waves predicted from the Biot Theory was witnessed. The Young’s Modulus based from the bulk velocity demonstrated a strong correlation, consistently predicting that the high-dose irradiated vertebrae had a lower Young’s Modulus compared to the Young’s Modulus of the low-dose vertebrae.;The results obtained during this study of measurement methodology of ultrasound velocity provide a strong foundation for future work.