SMU nets nearly $600K to study ultrasound in bone strength assessment
Metastasis from renal cancer in the lateral aspects of the lumbar vertebra L2. The image shows the lesion on axial PET/CT taken before spinal radiosurgery. Image source: European Cyberknife Center Munich
Southern Methodist University (SMU) in Dallas has received a $596,000 grant from the National Institutes of Health’s (NIH) Neurological Disorders and Stroke Institute to study the role of ultrasound in determining the effects of radiation on bone.

The 15-month grant will help lead author Edmond Richer, PhD, associate professor of engineering at SMU, and colleagues research cervical fractures that have been found to occur six to eight months following stereotactic radiosurgery in patients with vertebral metastases.

The study builds on prior research conducted by Richer and will focus on the use of ultrasound to determine bone strength. “Currently, the most accepted method by hospitals is bone mineral density measurement,” he noted, and explained that while this method can tell how much mineral is in the bone, it is not necessarily indicative of bone strength. “Bone mineral density is not the whole measure of bone strength," Richer offered.     

Vertebral metastases occur in approximately 100,000 cancer patients annually, most of whom have major lung, breast, prostate, renal and myeloma malignancies. Noninvasive stereotactic radiosurgery used for treating spinal tumors requires sophisticated instruments that deliver a precise amount of radiation to the targeted lesion and a fracture rate of up to 39 percent has been reported in post-radiosurgery patients who receive high doses of radiation, explained the researchers.

"We began looking at the history of radiosurgery, and as algorithms and instruments have become more refined in the computation of doses and the delivery of radiation, the number of required treatments has decreased to a single procedure," Richer said in an interview. The current concern for radiation oncologists rests on what happens to bone strength when treatments are reduced from six lower-grade doses, each a month apart, to a single high-grade dose.

While attempting to leverage ultrasound technology to complement bone mineral density measurements, Richer and colleagues discovered that bone elasticity is a factor influencing bone strength. Although quantification of bone elasticity may not replace measurement of bone minerals, it can be a useful complementary measure, he noted. 
With this in mind, Richer and his colleagues designed an ultrasound system for the determination of bone elasticity. Between 30 to 40 percent of bone strength cannot be quantified by bone mineral density alone, and Richer believes his instrument can supplement this measurement.

Multiple applications
Additionally, the ultrasound system, which is currently under FDA review, was designed to help physicians diagnose osteoporosis, noted Richer. According to his research, a class of osteoporosis medications can trigger severely suppressed bone remodeling in some patients. “This instrument turned out to be very accurate in detecting this condition,” he explained. 

Richer and his team developed three ultrasound systems and sent them to different U.S. hospitals for testing last year. With help from the grant, approximately 2,000 people will be monitored for a length of three years, noted Richer, in the hopes of “detecting and predicting bone strength and probability of fractures.”

Through their research, the investigators have found that bone cannot heal itself after fracture following a high dose of radiation treatment in one session. Determining a threshold amount to ensure safety in radiosurgery and whether this threshold varies from patient to patient is a top concern and research goal, shared Richer.

“The long-term implication for the research is finding counter measures for preventing bone fractures after radiation treatments, as well as establishing guidelines for radiation oncologists regarding the safe amount of radiation dose they can expose a patient to in one setting,” Richer concluded.