Fei Baowei, Wheaton Andrew, Lee Zhenghong, Duerk Jeffrey L, Wilson David L
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
Phys Med Biol. 2002 Mar 7;47(5):823-38. doi: 10.1088/0031-9155/47/5/309.
A three-dimensional (3D) mutual information registration method was created and used to register MRI volumes of the pelvis and prostate. It had special features to improve robustness. First, it used a multi-resolution approach and performed registration from low to high resolution. Second, it used two similarity measures, correlation coefficient at lower resolutions and mutual information at full resolution, because of their particular advantages. Third, we created a method to avoid local minima by restarting the registration with randomly perturbed parameters. The criterion for restarting was a correlation coefficient below an empirically determined threshold. Experiments determined the accuracy of registration under conditions found in potential applications in prostate cancer diagnosis, staging, treatment and interventional MRI (iMRI) guided therapies. Images were acquired in the diagnostic (supine) and treatment position (supine with legs raised). Images were also acquired as a function of bladder filling and the time interval between imaging sessions. Overall studies on three patients and three healthy volunteers, when both volumes in a pair were obtained in the diagnostic position under comparable conditions, bony landmarks and prostate 3D centroids were aligned within 1.6 +/- 0.2 mm and 1.4 +/- 0.2 mm, respectively, values only slightly larger than a voxel. Analysis suggests that actual errors are smaller because of the uncertainty in landmark localization and prostate segmentation. Between the diagnostic and treatment positions, bony landmarks continued to register well, but prostate centroids moved towards the posterior 2.8-3.4 mm. Manual cropping to remove voxels in the legs was necessary to register these images. In conclusion, automatic, rigid body registration is probably sufficiently accurate for many applications in prostate cancer. For potential iMRI-guided treatments, the small prostate displacement between the diagnostic and treatment positions can probably be avoided by acquiring volumes in similar positions and by reducing bladder and rectal volumes.
创建了一种三维（3D）互信息配准方法，并将其用于骨盆和前列腺的磁共振成像（MRI）容积配准。该方法具有提高鲁棒性的特殊特性。首先，它采用了多分辨率方法，从低分辨率到高分辨率进行配准。其次，由于其特殊优势，它使用了两种相似性度量，即较低分辨率下的相关系数和全分辨率下的互信息。第三，我们创建了一种通过使用随机扰动参数重新启动配准来避免局部最小值的方法。重新启动的标准是相关系数低于根据经验确定的阈值。实验确定了在前列腺癌诊断、分期、治疗以及介入性MRI（iMRI）引导治疗等潜在应用条件下配准的准确性。在诊断（仰卧位）和治疗位置（双腿抬起的仰卧位）采集图像。还根据膀胱充盈情况和成像会话之间的时间间隔采集图像。对三名患者和三名健康志愿者进行的总体研究表明，当在可比条件下在诊断位置获取一对中的两个容积时，骨标志和前列腺三维质心分别在1.6±0.2毫米和1.4±0.2毫米内对齐，这些值仅略大于一个体素。分析表明，由于标志定位和前列腺分割的不确定性，实际误差较小。在诊断和治疗位置之间，骨标志继续配准良好，但前列腺质心向后移动了2.8 - 3.4毫米。为了配准这些图像，需要手动裁剪以去除腿部的体素。总之，自动刚体配准对于前列腺癌的许多应用可能足够准确。对于潜在的iMRI引导治疗，通过在相似位置获取容积以及减少膀胱和直肠容积，可能可以避免诊断和治疗位置之间前列腺的小位移。
