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首页> 外文期刊>Medical Physics >Use and uncertainties of mutual information for computed tomography/ magnetic resonance (CT/MR) registration post permanent implant of the prostate.
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Use and uncertainties of mutual information for computed tomography/ magnetic resonance (CT/MR) registration post permanent implant of the prostate.

机译：永久性植入前列腺后，计算机断层扫描/磁共振（CT / MR）配准的相互信息的使用和不确定性。

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Post-implant dosimetric analysis for permanent implant of the prostate benefits from the use of a computed tomography (CT) dataset for optimal identification of the radioactive source (seed) positions and a magnetic resonance (MR) dataset for optimal description of the target and normal tissue volumes. The CT/MR registration process should be fast and sufficiently accurate to yield a reliable dosimetric analysis. Since critical normal tissues typically reside in dose gradient regions, small shifts in the dose distribution could impact the prediction of complication or complication severity. Standard procedures include the use of the seed distribution as fiducial markers (seed match), a time consuming process that relies on the proper identification of signals due to the same seed on both datasets. Mutual information (MI) is more efficient because it uses image data requiring minimal preparation effort. A comparison of MI registration and seed-match registration was performed for twelve patients. MI wasapplied to a volume limited to the prostate and surrounding structures, excluding most of the pelvic bone structures (margins around the prostate gland were approximately 2 cm right-left, approximately 1 cm anterior-posterior, and approximately 2 cm superior-inferior). Seeds were identified on a 2 mm slice CT dataset using an automatic seed identification procedure on reconstructed three-dimensional data. Seed positions on the 3 mm slice thickness T2 MR data set were identified using a point-and-click method on each image. Seed images were identified on more than one MR slice, and the results used to determine average seed coordinates for MR images and matched seed pairs between CT and MR images. On average, 42% (19%-64%) of the seeds (19-54 seeds) were identified and matched to their CT counterparts. A least-squares method applied to the CT and MR seed coordinates was used to produce the optimum seed-match registration. MI registration and seed match registration angle differences averaged 0.5 degrees, whichwas not significantly different from zero. Translation differences averaged 0.6 (1.2 standard deviation) mm right-left, -0.5(1.5) mm posterior-anterior, and -1.2(2.0) mm inferior-superior. Registration error estimates were approximately 2 mm for both the MI and seed-match methods. The observed standard deviations in the offset values were consistent with propagation of error. Registration methods as applied here using mutual information and seed matching are consistent, except for a small systematic difference in the inferior-superior axis for a minority of cases (approximately 15%). Cases registered with mutual information and with bony anatomy misregistration of greater than approximately 5 mm should be evaluated for rescan or seed-match registration. The improvement in efficiency of use for the MI registration method is substantial, approximately 30 min compared to several hours using seed match registration.
机译：永久性植入前列腺的植入后剂量学分析得益于使用计算机断层扫描（CT）数据集来最佳识别放射源（种子）位置，以及使用磁共振（MR）数据集来最佳地描述靶标和正常情况组织体积。 CT / MR配准过程应快速且足够准确，以进行可靠的剂量分析。由于关键的正常组织通常位于剂量梯度区域，因此剂量分布的微小变化可能会影响并发症或并发症严重程度的预测。标准程序包括使用种子分布作为基准标记（种子匹配），这是一个耗时的过程，由于两个数据集上的种子相同，因此需要正确识别信号。互信息（MI）效率更高，因为它使用需要最少准备工作的图像数据。对十二名患者进行了MI登记和种子匹配登记的比较。 MI适用于限于前列腺及其周围结构的体积，但不包括大部分骨盆骨结构（前列腺周围的边缘大约为左右2 cm，前后大约1 cm，上下大约2 cm）。在重建的三维数据上使用自动种子识别程序在2 mm切片CT数据集上识别种子。在每个图像上使用点击方法确定3mm切片厚度T2 MR数据集上的种子位置。在一个以上的MR切片上识别出种子图像，并将结果用于确定MR图像的平均种子坐标以及CT和MR图像之间匹配的种子对。平均而言，鉴定出42％（19％-64％）的种子（19-54种子）并与它们的CT对应物匹配。使用应用于CT和MR种子坐标的最小二乘法来产生最佳种子匹配配准。 MI配准和种子配准配准角差平均为0.5度，与零没有显着差异。左右平移平均为0.6（1.2标准偏差）mm，前后平均为-0.5（1.5）mm，上下均-1.2（2.0）mm。 MI和种子匹配方法的配准误差估计均为约2 mm。偏移值中观察到的标准偏差与误差传播一致。这里使用互信息和种子匹配的注册方法是一致的，除了在少数情况下下上轴有一个小的系统差异（大约15％）。相互信息注册且骨骼解剖失准大于5 mm的病例应进行重新扫描或种子匹配注册评估。 MI注册方法的使用效率显着提高，与使用种子匹配注册的几个小时相比，大约需要30分钟。

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