Stadlbauer A, Nimsky C, Gruber S, Moser E, Hammen T, Engelhorn T, Buchfelder M, Ganslandt O
Department of Neurosurgery, University of Erlangen-Nuremberg, Germany.
AJNR Am J Neuroradiol. 2007 Mar;28(3):462-9.
The underlying changes in the neuronal connectivity adjacent to brain tumors cannot always be depicted by conventional MR imaging. The hypothesis of this study was that preoperative sensorimotor deficits are associated with impairment in pyramidal fiber bundles. Hence, we investigated the potential of combined quantitative diffusion tensor (DT) fiber tracking and MR spectroscopic imaging (MRSI) to determine changes in the pyramidal tract adjacent to gliomas.
Quantitative DT fiber tracking and proton MRSI were performed in 20 patients with gliomas with WHO grades II-IV. Eight patients experienced preoperative sensorimotor deficits. Mean diffusivity (MD), fractional anisotropy (FA), and number of fibers per voxel (FpV) were calculated for the pyramidal tract of the ipsilateral and contralateral hemisphere. Metabolite concentrations for choline-containing compounds (Cho), creatine (Cr), and N-acetylaspartate (NAA) were computed, using LCModel, for all voxels located at the pyramidal tracts.
For the whole pyramidal tract, quantitative DT fiber tracking resulted in significantly lower FpV and FA values (P < .001), but not MD values, for the ipsilateral hemisphere. For the section of the fiber bundle closest to the lesion, we found significantly decreased FpV and FA (P < .001) and increased MD (P = .002). MRSI showed, for the same volumes of interest, significantly decreased NAA (P = .001), increased Cho (P = .034) and Cho/NAA (P = .001) for the ipsilateral pyramidal tract. In patients suffering sensorimotor deficits, we found significantly lower FA (P = .022) and higher MD values (P = .026) and a strongly negative correlation between FA and MD (R = -0.710, P = .024) but no correlation in patients without deficits (R = 0.078, ns).
Quantitative DTI was able to show significant differences in diffusivity of the pyramidal tract in patients with sensorimotor deficits in relation to patients without them. The additional use of proton MRSI may be helpful to discern whether these diffusivity changes in fiber tracts are caused by tumor infiltration or peritumoral edema.
传统磁共振成像（MR）并不总能显示脑肿瘤周围神经元连接的潜在变化。本研究的假设是术前感觉运动功能障碍与锥体纤维束受损有关。因此，我们研究了联合定量扩散张量（DT）纤维追踪和磁共振波谱成像（MRSI）来确定胶质瘤周围锥体束变化的潜力。
对20例世界卫生组织（WHO）II-IV级胶质瘤患者进行了定量DT纤维追踪和质子MRSI检查。8例患者术前有感觉运动功能障碍。计算同侧和对侧半球锥体束的平均扩散率（MD）、各向异性分数（FA）和每体素纤维数（FpV）。使用LCModel计算位于锥体束的所有体素中含胆碱化合物（Cho）、肌酸（Cr）和N-乙酰天门冬氨酸（NAA）的代谢物浓度。
对于整个锥体束，定量DT纤维追踪显示同侧半球的FpV和FA值显著降低（P <.001），但MD值无显著变化。对于最靠近病变的纤维束部分，我们发现FpV和FA显著降低（P <.001），MD升高（P =.002）。MRSI显示，对于相同的感兴趣体积，同侧锥体束的NAA显著降低（P =.001），Cho升高（P =.034），Cho/NAA升高（P =.001）。在有感觉运动功能障碍的患者中，我们发现FA显著降低（P =.022），MD值升高（P =.026），FA与MD之间呈强负相关（R = -0.710，P =.024），而在无功能障碍的患者中无相关性（R = 0.078，无显著性差异）。
定量扩散张量成像（DTI）能够显示有感觉运动功能障碍的患者与无功能障碍的患者在锥体束扩散率方面的显著差异。质子MRSI的额外应用可能有助于辨别纤维束中的这些扩散率变化是由肿瘤浸润还是瘤周水肿引起的。
