MR-based keyhole SPECT for small animal imaging.
MR-based keyhole SPECT for small animal imaging.
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DOI：
10.1088/0031-9155/56/3/010
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发表时间：
2011-02-07
影响因子：
3.5
通讯作者：
Nalcioglu O
中科院分区：
文献类型：
--
作者：
Lee KS;Roeck WW;Gullberg GT;Nalcioglu O
多模态成像的基本原理是整合不同成像技术的优势，同时减少单个模态的缺点。这里提出的工作提出了一个有限的视野（LFOV）SPECT重建技术，可以实现多模态MR/SPECT系统，可用于获得同时的MRI和SPECT图像的小动物成像。在这项工作中使用组合MR/SPECT系统的原因是为了消除当MR图像用作SPECT的先验信息时两组图像之间的任何可能的配准不良。在核成像中，目标区域通常小于整个对象;因此，将探测器聚焦在LFOV上会产生各种优点，包括使用更小的核探测器（成本更低）、更小的重建区域（重建速度更快）以及在与具有放大倍数的针孔准直器结合使用时更高的空间分辨率。MR/SPECT系统可用于选择SPECT的感兴趣区域（ROI）。由全视场（FOV）MRI与初步SPECT图像组合获得的先验信息可以用于通过将计算限制到较小的FOV来减少SPECT重建的维度，同时减少由截断数据产生的伪影。由于该技术基于LFOV内的SPECT成像，因此将其称为锁孔SPECT（K-SPECT）方法。首先，获得使用较大FOV的整个对象的MRI图像，以确定覆盖靶器官的ROI的位置。一旦确定了ROI，将动物移动到射频（rf）线圈内，以将目标区域带入LFOV内，然后同时进行MRI和SPECT。SPECT图像的空间分辨率通过采用放大率>1的针孔准直器来提高，通过仔细计算每个针孔的接受角来避免复用。在我们的设计中，所有的针孔都集中在LFOV的中心。K-SPECT重建是通过使用由同时采集的MR图像获得的先验信息和从在没有任何先验输入的情况下重建的SPECT图像的ROI区域获得的放射性分布来生成自适应加权矩阵来实现的。使用数值幻影模拟的初步结果表明，在LFOV内的SPECT图像的图像分辨率得到改善，同时最大限度地减少由于所选择的放大率和新的重建技术的LFOV外的对象的部分所产生的伪影。对于使用K-SPECT重建技术的球形体模，场外伪影的均方根误差（RMSE）降低了60%，对于使用MOBY体模的心脏，降低了48.5-52.6%。KSPECT重建技术显著提高了空间分辨率和量化，同时减少了LFOV外的伪影，并降低了重建矩阵的维数。
The rationale for multi-modality imaging is to integrate the strengths of different imaging technologies while reducing the shortcomings of an individual modality. The work presented here proposes a limited-field-of-view (LFOV) SPECT reconstruction technique that can be implemented on a multi-modality MR/SPECT system that can be used to obtain simultaneous MRI and SPECT images for small animal imaging. The reason for using a combined MR/SPECT system in this work is to eliminate any possible misregistration between the two sets of images when MR images are used as a priori information for SPECT. In nuclear imaging the target area is usually smaller than the entire object; thus, focusing the detector on the LFOV results in various advantages including the use of a smaller nuclear detector (less cost), smaller reconstruction region (faster reconstruction) and higher spatial resolution when used in conjunction with pinhole collimators with magnification. The MR/SPECT system can be used to choose a region of interest (ROI) for SPECT. A priori information obtained by the full field-of-view (FOV) MRI combined with the preliminary SPECT image can be used to reduce the dimensions of the SPECT reconstruction by limiting the computation to the smaller FOV while reducing artifacts resulting from the truncated data. Since the technique is based on SPECT imaging within the LFOV it will be called the keyhole SPECT (K-SPECT) method. At first MRI images of the entire object using a larger FOV are obtained to determine the location of the ROI covering the target organ. Once the ROI is determined, the animal is moved inside the radiofrequency (rf) coil to bring the target area inside the LFOV and then simultaneous MRI and SPECT are performed. The spatial resolution of the SPECT image is improved by employing a pinhole collimator with magnification >1 by having carefully calculated acceptance angles for each pinhole to avoid multiplexing. In our design all the pinholes are focused to the center of the LFOV. K-SPECT reconstruction is accomplished by generating an adaptive weighting matrix using a priori information obtained by simultaneously acquired MR images and the radioactivity distribution obtained from the ROI region of the SPECT image that is reconstructed without any a priori input. Preliminary results using simulations with numerical phantoms show that the image resolution of the SPECT image within the LFOV is improved while minimizing artifacts arising from parts of the object outside the LFOV due to the chosen magnification and the new reconstruction technique. The root-mean-square-error (RMSE) in the out-of-field artifacts was reduced by 60% for spherical phantoms using the K-SPECT reconstruction technique and by 48.5–52.6% for the heart in the case with the MOBY phantom. The KSPECT reconstruction technique significantly improved the spatial resolution and quantification while reducing artifacts from the contributions outside the LFOV as well as reducing the dimension of the reconstruction matrix.
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影响因子：
3.5
作者：
Hamamura, Mark J.;Ha, Seunghoon;Nalcioglu, Orhan
通讯作者：
Nalcioglu, Orhan
影响因子：
1.8
作者：
Meikle, SR;Kench, P;Fulham, MJ
通讯作者：
Fulham, MJ
影响因子：
1.8
作者：
NALCIOGLU, O;CHO, ZH;LOU, RY
通讯作者：
LOU, RY
影响因子：
10.6
作者：
OGAWA, K;HARATA, Y;HASHIMOTO, S
通讯作者：
HASHIMOTO, S
影响因子：
3.5
作者：
Beekman, FJ;Vastenhouw, B
通讯作者：
Vastenhouw, B