Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull
Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull
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DOI：
10.2967/jnumed.114.149997
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发表时间：
2015-03-01
影响因子：
9.3
通讯作者：
Veit-Haibach, Patrick
中科院分区：
文献类型：
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作者：
Delso, Gaspar;Wiesinger, Florian;Veit-Haibach, Patrick
基于MR的衰减校正对于集成PET/MR成像很有帮助。其通常通过将MR图像分割成具有已知衰减特性的一组组织类别（例如，空气、肺、骨、脂肪、软组织）。然而，由于骨组织的低质子密度和快速衰减时间，利用MR成像进行骨识别是相当具有挑战性的。本文介绍了一种新的、最近发表的基于零回波时间（ZTE）的头部MR骨骼描绘和分割方法的临床评价。方法：2014年早些时候披露了一种基于质子密度加权ZTE成像的MR成像骨分割新范例。在这项研究中，我们审查了骨地图获得了15个临床数据集与PET/CT/MR三模态设置与此方法。为PET衰减校正目的采集的CT扫描用作评价的参考。由经验丰富的放射科医师和核医学医师根据ZTE和CT骨掩模之间的Jaccard距离进行定量测量，并对解剖准确性进行定性评分。结果：在整个头部评价的ZTE和CT骨掩模之间的平均Jaccard距离为52% +/- 6%（范围，38%-63%）。当仅考虑颅骨时，距离为39% ± 4%（范围，32%-49%）。这些结果超过了先前报道的使用双回波超短回波时间的尝试，其中Jaccard距离在47%-79%范围内（分别为顶骨和鼻部区域）。在解剖学上，颅骨被一致地良好分割，具有频繁但孤立的体素错误分类。具有高度解剖细节的气腔壁和骨/流体界面，例如内耳，仍然是一个挑战。结论：据我们所知，这是第一个基于ZTE序列的颅骨识别的临床评价。结果表明，质子密度加权中兴成像是一种有效的手段，获得高分辨率地图的骨组织与足够的解剖精度，例如，PET衰减校正。
MR-based attenuation correction is instrumental for integrated PET/MR imaging. It is generally achieved by segmenting MR images into a set of tissue classes with known attenuation properties (e.g., air, lung, bone, fat, soft tissue). Bone identification with MR imaging is, however, quite challenging, because of the low proton density and fast decay time of bone tissue. The clinical evaluation of a novel, recently published method for zero-echo-time (ZTE)-based MR bone depiction and segmentation in the head is presented here. Methods: A new paradigm for MR imaging bone segmentation, based on proton density-weighted ZTE imaging, was disclosed earlier in 2014. In this study, we reviewed the bone maps obtained with this method on 15 clinical datasets acquired with a PET/CT/MR trimodality setup. The CT scans acquired for PET attenuation-correction purposes were used as reference for the evaluation. Quantitative measurements based on the Jaccard distance between ZTE and CT bone masks and qualitative scoring of anatomic accuracy by an experienced radiologist and nuclear medicine physician were performed. Results: The average Jaccard distance between ZTE and CT bone masks evaluated over the entire head was 52% +/- 6% (range, 38%-63%). When only the cranium was considered, the distance was 39% +/- 4% (range, 32%-49%). These results surpass previously reported attempts with dualecho ultrashort echo time, for which the Jaccard distance was in the 47%-79% range (parietal and nasal regions, respectively). Anatomically, the calvaria is consistently well segmented, with frequent but isolated voxel misclassifications. Air cavity walls and bone/fluid interfaces with high anatomic detail, such as the inner ear, remain a challenge. Conclusion: This is the first, to our knowledge, clinical evaluation of skull bone identification based on a ZTE sequence. The results suggest that proton density-weighted ZTE imaging is an efficient means of obtaining high-resolution maps of bone tissue with sufficient anatomic accuracy for, for example, PET attenuation correction.