Orth R C, Sinha P, Madsen E L, Frank G, Korosec F R, Mackie T R, Mehta M P
Department of Human Oncology, University of Wisconsin, Madison, USA.
Neurosurgery. 1999 Dec;45(6):1423-9; discussion 1429-31. doi: 10.1097/00006123-199912000-00030.
To test the spatial accuracy of coordinates generated from magnetic resonance imaging (MRI) scans, using the Brown-Roberts-Wells head frame and localizer system (Radionics, Inc., Burlington, MA).
An anthropomorphic head phantom, consisting of a two-dimensional lattice of acrylic spheres (4-mm diameter) spaced 10 mm apart and embedded in a brain tissue-mimicking gelatin-agar gel, was constructed. The intersphere distances for the target lattice positions in MRI and computed tomographic scan sets were compared. The data sets were fused, and differences in fiducial marker and intraphantom target positions were measured.
Intersphere distances were identical for the MRI and computed tomographic scan sets (10 +/- 0.1 mm). Differences in fiducial marker positions [maximal lateral difference, 0.97 mm; mean absolute lateral difference, 0.69 +/- 0.22 mm; maximal anteroposterior (AP) difference, 1.99 mm; mean absolute AP difference, 1.29 +/- 0.67 mm] were correlated with differences in intraphantom target positions (maximal lateral difference, 0.83 mm; mean absolute lateral difference, 0.28 +/- 0.24 mm; maximal AP difference, -1.97 mm; mean absolute AP difference, 1.63 +/- 25 mm; maximal vertical difference, -0.73 mm; mean absolute vertical difference, 0.34 +/- 0.21 mm). This suggested that improper fiducial rod identification and the subsequent transformation to stereotactic coordinate space were the greatest sources of spatial uncertainty.
With computed tomographic data as the standard, these differences resulted in maximal and minimal composite uncertainties of 2.06 and 1.17 mm, respectively. The measured uncertainties exceed recommended standards for radiosurgery but allow the possible use of MRI-based stereotactic treatment planning for certain intracranial lesions, if the errors are corrected using appropriate software. Clinicians must recognize that error magnitudes vary for different systems, and they should perform systematic, scheduled, institutional error analyses as part of their ongoing quality assurance processes. This phantom provides one tool for measuring such variances.
使用布朗 - 罗伯茨 - 韦尔斯头部框架和定位系统（Radionics公司，马萨诸塞州伯灵顿）测试磁共振成像（MRI）扫描生成坐标的空间准确性。
构建一个拟人化头部模型，该模型由直径4毫米、间距10毫米的丙烯酸球体二维晶格组成，并嵌入模拟脑组织的明胶 - 琼脂凝胶中。比较MRI和计算机断层扫描集中目标晶格位置的球间距离。将数据集融合，并测量基准标记和模型内目标位置的差异。
MRI和计算机断层扫描集的球间距离相同（10±0.1毫米）。基准标记位置的差异[最大横向差异为0.97毫米；平均绝对横向差异为0.69±0.22毫米；最大前后（AP）差异为1.99毫米；平均绝对AP差异为1.29±0.67毫米]与模型内目标位置的差异相关（最大横向差异为0.83毫米；平均绝对横向差异为0.28±0.24毫米；最大AP差异为 - 1.97毫米；平均绝对AP差异为1.63±25毫米；最大垂直差异为 - 0.73毫米；平均绝对垂直差异为0.34±0.21毫米）。这表明基准杆识别不当以及随后转换到立体定向坐标空间是空间不确定性的最大来源。
以计算机断层扫描数据为标准，这些差异分别导致最大和最小复合不确定性为2.06和1.17毫米。测量到的不确定性超过了放射外科的推荐标准，但如果使用适当软件校正误差，则允许对某些颅内病变使用基于MRI的立体定向治疗计划。临床医生必须认识到不同系统的误差大小不同，并且作为其持续质量保证过程的一部分，他们应该进行系统的、定期的、机构性的误差分析。这个模型提供了一种测量此类差异的工具。
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