Registration accuracy for MR images of the prostate using a subvolume based registration protocol.
Registration accuracy for MR images of the prostate using a subvolume based registration protocol.
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DOI：
10.1186/1748-717x-6-73
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发表时间：
2011-06-16
期刊：
影响因子：
--
通讯作者：
Nyholm T
中科院分区：
文献类型：
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作者：
Jonsson JH;Brynolfsson P;Garpebring A;Karlsson M;Söderström K;Nyholm T
近年来，由于与计算机断层扫描相比具有上级软组织对比度，将磁共振成像（MRI）整合到外部放射治疗工作流程中的研究工作量相当大。图像配准是许多应用中的必要步骤，例如，在患者定位和具有重复成像的治疗反应评估中。在这项研究中，我们调查之间的依赖关系的配准精度和注册体积的大小为基础的刚性配准协议的MR图像的前列腺的子体积。在放射治疗过程中，使用T2加权序列对10名患者进行了4次成像。使用均方距离度量和用于不同尺寸的配准体积的阶跃梯度优化器将图像彼此配准。使用配准图像中手动定义的前列腺之间的质心距离评价配准的精度。通过最小化这些距离的标准差来确定配准体积的最佳尺寸。我们发现，前列腺的位置是最不确定的前后（AP）方向使用传统的全容积注册。在AP方向上，使用针对前列腺优化的配准体积的前列腺体积之间的平均质心距离的标准差的改善为3.9 mm（p < 0.001）。最佳配准体积尺寸为0 mm边缘，添加到前列腺，如第一个图像系列中所述。用于治疗设置或治疗评估的前列腺的重复MR成像都需要高精度组织配准。通过基于子体积的配准，与基于整个骨盆的配准的几毫米相比，前列腺配准不确定性可以降低到1 mm（1 SD）的量级。
In recent years, there has been a considerable research effort concerning the integration of magnetic resonance imaging (MRI) into the external radiotherapy workflow motivated by the superior soft tissue contrast as compared to computed tomography. Image registration is a necessary step in many applications, e.g. in patient positioning and therapy response assessment with repeated imaging. In this study, we investigate the dependence between the registration accuracy and the size of the registration volume for a subvolume based rigid registration protocol for MR images of the prostate. Ten patients were imaged four times each over the course of radiotherapy treatment using a T2 weighted sequence. The images were registered to each other using a mean square distance metric and a step gradient optimizer for registration volumes of different sizes. The precision of the registrations was evaluated using the center of mass distance between the manually defined prostates in the registered images. The optimal size of the registration volume was determined by minimizing the standard deviation of these distances. We found that prostate position was most uncertain in the anterior-posterior (AP) direction using traditional full volume registration. The improvement in standard deviation of the mean center of mass distance between the prostate volumes using a registration volume optimized to the prostate was 3.9 mm (p < 0.001) in the AP direction. The optimum registration volume size was 0 mm margin added to the prostate gland as outlined in the first image series. Repeated MR imaging of the prostate for therapy set-up or therapy assessment will both require high precision tissue registration. With a subvolume based registration the prostate registration uncertainty can be reduced down to the order of 1 mm (1 SD) compared to several millimeters for registration based on the whole pelvis.