Beeler Whitney H, Paradis Kelly C, Gemmete Joseph J, Chaudhary Neeraj, Kim Michelle M, Smith Sean R, Paradis Eric, Matuszak Martha M, Park Paul, Archer Paul G, Szerlip Nicholas J, Spratt Daniel E
Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan, USA.
Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
World Neurosurg. 2019 Feb;122:e655-e666. doi: 10.1016/j.wneu.2018.10.118. Epub 2018 Oct 26.
Underestimation of the spinal cord's volume or position during spine stereotactic radiosurgery can lead to severe myelopathy, whereas overestimation can lead to tumor underdosage. Spinal cord delineation is commonly achieved by registering a magnetic resonance imaging (MRI) study with a computed tomography (CT) simulation scan or by performing myelography during CT simulation (myelosim). We compared treatment planning outcomes for these 2 techniques.
Twenty-three cases of spine stereotactic radiosurgery were analyzed that had both a myelosim and corresponding MRI study for registration. The spinal cord was contoured on both imaging data sets by 2 independent blinded physicians, and Dice similarity coefficients were calculated to compare their spatial overlap. Two treatment plans (16 Gy and 18 Gy) were created using the MRI and CT contours (92 plans total). Dosimetric parameters were extracted and compared by modality to assess tumor coverage and spinal cord dose.
No differences were found in the partial spinal cord volumes contoured on MRI versus myelosim (4.71 ± 1.09 vs. 4.55 ± 1.03 cm; P = 0.34) despite imperfect spatial agreement (mean Dice similarity coefficient, 0.68 ± 0.05). When the registered MRI contours were used for treatment planning, significantly worse tumor coverage and greater spinal cord doses were found compared with myelosim planning. For the 18-Gy plans, 10 of 23 MRI cases (43%) exceeded the spinal cord or cauda dose constraints when using myelosim as the reference standard.
Significant spatial, rather than volumetric, differences were found between the MRI- and myelosim-defined spinal cord structures. Tumor coverage was compromised with MRI-based planning, and the high spinal cord doses were a concern. Future work is necessary to compare thin-cut, volumetric MRI registration or MRI simulation with myelosim.
在脊柱立体定向放射治疗期间，脊髓体积或位置的低估可导致严重的脊髓病，而高估则可导致肿瘤剂量不足。脊髓轮廓的勾画通常是通过将磁共振成像（MRI）研究与计算机断层扫描（CT）模拟扫描进行配准，或在CT模拟期间进行脊髓造影（脊髓造影模拟）来实现的。我们比较了这两种技术的治疗计划结果。
分析了23例脊柱立体定向放射治疗病例，这些病例既有脊髓造影模拟又有相应的用于配准的MRI研究。两名独立的不知情医生在两个成像数据集上勾勒出脊髓轮廓，并计算Dice相似系数以比较它们的空间重叠。使用MRI和CT轮廓创建了两个治疗计划（16 Gy和18 Gy，共92个计划）。提取剂量学参数并按方式进行比较，以评估肿瘤覆盖范围和脊髓剂量。
尽管空间一致性不完善（平均Dice相似系数为0.68±0.05），但在MRI与脊髓造影模拟上勾勒出的部分脊髓体积没有差异（4.71±1.09 vs. 4.55±1.03 cm；P = 0.34）。当使用配准的MRI轮廓进行治疗计划时，与脊髓造影模拟计划相比，发现肿瘤覆盖明显更差，脊髓剂量更高。对于18 Gy的计划，以脊髓造影模拟作为参考标准时，23例MRI病例中有10例（43%）超过了脊髓或马尾剂量限制。
在MRI和脊髓造影模拟定义的脊髓结构之间发现了显著的空间差异，而非体积差异。基于MRI的计划会损害肿瘤覆盖，高脊髓剂量令人担忧。未来有必要开展工作，将薄层容积MRI配准或MRI模拟与脊髓造影模拟进行比较。
