Bucknor Matthew D, Rieke Viola, Seo Youngho, Horvai Andrew E, Hawkins Randall A, Majumdar Sharmila, Link Thomas M, Saeed Maythem
From the Department of Radiology and Biomedical Imaging, University of California-San Francisco, 185 Berry St, Suite 350, San Francisco, CA 94107-5705.
Radiology. 2015 Feb;274(2):387-94. doi: 10.1148/radiol.14132605. Epub 2014 Oct 8.
To serially monitor bone remodeling in the swine femur after magnetic resonance (MR) imaging-guided high-intensity focused ultrasound (HIFU) ablation with MR imaging, computed tomography (CT), sodium fluorine 18 (Na(18)F)-positron emission tomography (PET), and histopathologic examination, as a function of sonication energy.
Experimental procedures received approval from the local institutional animal care and use committee. MR imaging-guided HIFU was used to create distal and proximal ablations in the right femurs of eight pigs. The energy used at the distal target was higher (mean, 419 J; range, 390-440 J) than that used at the proximal target (mean, 324 J; range, 300-360 J). Imaging was performed before and after ablation with 3.0-T MR imaging and 64-section CT. Animals were reevaluated at 3 and 6 weeks with MR imaging (n = 8), CT (n = 8), Na(18)F-PET (n = 4), and histopathologic examination (n = 4). Three-dimensional ablation lengths were measured on contrast material-enhanced MR images, and bone remodeling in the cortex was measured on CT images.
Ablation sizes at MR imaging 3 and 6 weeks after MR imaging-guided HIFU ablation were similar between proximal (low-energy) and distal (high-energy) lesions (average, 8.7 × 21.9 × 16.4 mm). However, distal ablation lesions (n = 8) demonstrated evidence of subperiosteal new bone formation at CT, with a subtle focus of new ossification at 3 weeks and a larger focus of ossification at 6 weeks. New bone formation was associated with increased uptake at Na(18)F-PET in three of four animals; this was confirmed at histopathologic examination in four of four animals.
MR imaging-guided HIFU ablation of bone may result in progressive remodeling, with both subcortical necrosis and subperiosteal new bone formation. This may be related to the use of high energies. MR imaging, CT, and PET are suitable noninvasive techniques to monitor bone remodeling after MR imaging-guided HIFU ablation.
采用磁共振成像（MR）、计算机断层扫描（CT）、氟-18 钠（Na(18)F）正电子发射断层扫描（PET）及组织病理学检查，对猪股骨在磁共振成像引导下高强度聚焦超声（HIFU）消融后的骨重塑进行系列监测，作为超声能量的函数。
实验程序获得当地机构动物护理和使用委员会的批准。使用磁共振成像引导的高强度聚焦超声在 8 头猪的右侧股骨上进行远端和近端消融。远端靶点使用的能量（平均 419 J；范围 390 - 440 J）高于近端靶点（平均 324 J；范围 300 - 360 J）。在消融前后分别用 3.0-T 磁共振成像和 64 层 CT 进行成像。在 3 周和 6 周时，对动物进行再次评估，采用磁共振成像（n = 8）、CT（n = 8）、Na(18)F-PET（n = 4）及组织病理学检查（n = 4）。在对比剂增强磁共振图像上测量三维消融长度，在 CT 图像上测量皮质骨的骨重塑。
磁共振成像引导下高强度聚焦超声消融后 3 周和 6 周时，近端（低能量）和远端（高能量）病变在磁共振成像上的消融大小相似（平均 8.7×21.9×16.4 mm）。然而，远端消融病变（n = 8）在 CT 上显示有骨膜下新骨形成的证据，在 3 周时有一个细微的新骨化灶，在 6 周时有一个更大的骨化灶。在四只动物中的三只，新骨形成与 Na(18)F-PET 摄取增加相关；在四只动物中的四只经组织病理学检查得到证实。
磁共振成像引导下高强度聚焦超声骨消融可能导致进行性重塑，伴有皮质下坏死和骨膜下新骨形成。这可能与高能量的使用有关。磁共振成像、CT 和 PET 是监测磁共振成像引导下高强度聚焦超声消融后骨重塑的合适无创技术。
