Matthew Dwayne Bucknor MD, Presenter: Nothing to Disclose

Viola Rieke PhD, Abstract Co-Author: Nothing to Disclose

Youngho Seo PhD, Abstract Co-Author: Research Consultant, sanofi-aventis Group

Andrew Horvai, Abstract Co-Author: Nothing to Disclose

Loi Do, Abstract Co-Author: Nothing to Disclose

Randall A. Hawkins MD, PhD, Abstract Co-Author: Nothing to Disclose

Sharmila Majumdar PhD, Abstract Co-Author: Research Grant, Merck & Co, Inc

Thomas M. Link MD, PhD, Abstract Co-Author: Research funded, General Electric Company Research funded, InSightec Ltd

Maythem Saeed DVM, PhD, Abstract Co-Author: Nothing to Disclose

To monitor bone remodeling following MR guided high-intensity focused ultrasound (MRgHIFU) of the normal swine femur with MRI, CT, Na18F-PET and histopathology, as a function of sonication energy.

Experimental procedures received approval from the local institutional animal care and use committee. MRgHIFU ablations were created in the distal and proximal right femur of eight pigs. Energy dosed distally was higher (419±19 J) than the proximal target (324±17 J). Imaging was obtained before and after ablation using MRI (3T) and CT (64-slice). Animals were evaluated again at 3 and 6 weeks on MRI (n=8), CT (n=8), Na18F-PET (n=4) and histopathology (n=4). Ablation dimensions were measured on contrast enhanced MRI and cortical bone remodeling was measured on CT images.

MRI bone ablation sizes at 3 and 6 weeks following MRgHIFU were similar between distal (high energy) and proximal (low energy) lesions (average 8.7 x 21.9 x 16.4 mm). However, distal (high energy) ablations (n=8/8) demonstrated evidence of subperiosteal new bone formation on CT, with a subtle focus of new bone at 3 weeks and a larger ossification at 6 weeks. These morphologic changes were associated with increased uptake on Na18F-PET in 3/4 animals and confirmed by histopathology in 4/4. In contrast, proximal (low energy) ablations (8/8) demonstrated endosteal fat necrosis and subcortical osteonecrosis, but did not show evidence of new bone formation.

MRgHIFU ablation of bone can result in progressive remodeling with both subcortical necrosis and subperiosteal new bone formation. The exact pattern may be related to the energy dose used. MRI, CT and PET are suitable noninvasive techniques to monitor bone remodeling following MRgHIFU.

Specific parameter changes during MRgHIFU of bone could potentially be used to change the pattern of chronic remodeling after treatment. Higher energies might be preferable to stimulate new bone growth, for example, when treating a lytic bone metastasis, while relatively lower energies might be preferable for treatment of benign conditions.

Bucknor, M, Rieke, V, Seo, Y, Horvai, A, Do, L, Hawkins, R, Majumdar, S, Link, T, Saeed, M, MRI, CT, Na18F-PET, and Histopathological Monitoring of Bone Remodeling Following MR-guided High-intensity Focused Ultrasound.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14003559.html