Swamy Akash, Burström Gustav, Spliethoff Jarich W, Babic Drazenko, Ruschke Stefan, Racadio John M, Edström Erik, Terander Adrian Elmi, Dankelman Jenny, Hendriks Benno H W
Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, the Netherlands.
Department of In-body Systems, Philips Research, Royal Philips NV, High Tech Campus 34, 5656 AE, Eindhoven, the Netherlands.
Biomed Opt Express. 2019 Aug 1;10(8):4316-4328. doi: 10.1364/BOE.10.004316.
Safe and accurate placement of pedicle screws remains a critical step in open and minimally invasive spine surgery. The diffuse reflectance spectroscopy (DRS) technique may offer the possibility of intra-operative guidance for pedicle screw placement. Currently, Magnetic Resonance Imaging (MRI) is one of the most accurate techniques used to measure fat concentration in tissues. Therefore, the purpose of this study is to compare the accuracy of fat content measured invasively in vertebrae using DRS and validate it against the Proton density fat fraction (PDFF) derived via MRI. Chemical shift-encoding-based water-fat imaging of the spine was first performed on six cadavers. PDFF images were computed and manually segmented. 23 insertions using a custom-made screw probe with integrated optical fibers were then performed under cone beam computer tomography (CBCT). DR spectra were recorded at several positions along the trajectory as the optical screw probe was inserted turn by turn into the vertebral body. Fat fractions determined via DRS and MRI techniques were compared by spatially correlating the optical screw probe position within the vertebrae on CBCT images with respect to the PDFF images. The fat fraction determined by DRS was found to have a high correlation with those determined by MRI, with a Pearson coefficient of 0.950 (P< 0.001) as compared with PDFF measurements calculated from the MRI technique. Additionally, the two techniques were found to be comparable for fat fraction quantification within vertebral bodies (R = 0.905).
椎弓根螺钉的安全准确置入仍然是开放和微创脊柱手术中的关键步骤。漫反射光谱（DRS）技术可能为椎弓根螺钉置入提供术中指导的可能性。目前，磁共振成像（MRI）是用于测量组织中脂肪浓度的最准确技术之一。因此，本研究的目的是比较使用DRS侵入性测量椎骨中脂肪含量的准确性，并与通过MRI得出的质子密度脂肪分数（PDFF）进行验证。首先对六具尸体进行基于化学位移编码的脊柱水脂成像。计算并手动分割PDFF图像。然后在锥束计算机断层扫描（CBCT）下使用带有集成光纤的定制螺钉探头进行23次插入。随着光学螺钉探头逐圈插入椎体，在沿轨迹的几个位置记录DR光谱。通过将CBCT图像上椎骨内的光学螺钉探头位置与PDFF图像进行空间关联，比较了通过DRS和MRI技术确定的脂肪分数。发现通过DRS确定的脂肪分数与通过MRI确定的脂肪分数具有高度相关性，与从MRI技术计算的PDFF测量值相比，皮尔逊系数为0.950（P<0.001）。此外，发现这两种技术在椎体脂肪分数定量方面具有可比性（R = 0.905）。
