Quantitative characterizations of ultrashort echo (UTE) images for supporting air-bone separation in the head.
Quantitative characterizations of ultrashort echo (UTE) images for supporting air-bone separation in the head.
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DOI：
10.1088/0031-9155/60/7/2869
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发表时间：
2015-04-07
影响因子：
3.5
通讯作者：
Balter JM
中科院分区：
文献类型：
--
作者：
Hsu SH;Cao Y;Lawrence TS;Tsien C;Feng M;Grodzki DM;Balter JM
空气和骨的准确分离对于从MRI创建合成CT以支持放射肿瘤学工作流程至关重要。本研究比较了两种不同的超短回波时间序列在空气与骨分离中的作用，并评估了纠正图像强度不均匀性和考虑组织边界强度梯度以提高区分能力的后处理方法。根据机构审查委员会批准的前瞻性方案，对12名患者进行了CT和MRI扫描。测试的两个MRI序列是使用3D径向采集（UTE）的超短TE成像和使用径向采集的逐点编码时间减少（PETRA）。采集后，对两个MR图像体积进行梯度非线性校正。通过供应商提供的归一化方法校正MRI强度不均匀性，然后使用N4itk算法进一步校正。为了克服在空气组织边界的强度梯度，空间扩张，从0到4毫米，应用于阈值定义的空气区域从MR图像。通过比较预测（由MR图像定义）与“真实”空气和骨区域（由CT图像定义），在有和没有残余偏置场校正和局部空间扩展的情况下进行受试者工作特征（ROC）分析。与未校正相比，后处理校正使UTE图像的ROC曲线下面积（AUC）从0.944 ± 0.012增加到0.976 ± 0.003，PETRA图像的AUC从0.850 ± 0.022增加到0.887 ± 0.012。当扩大阈值定义的空气体积，如预期的那样，空气识别的灵敏度随着骨辨别的特异性的增加而降低，但是以非线性的方式。对于UTE和PETRA图像，1 mm空气面罩扩张分别使AUC增加1%和4%。UTE图像在分离空气和骨方面的辨别力明显高于PETRA图像。后处理策略提高了UTE和PETRA图像中空气与骨的区分能力，并减少了两种成像序列之间的差异。后处理的UTE和PETRA图像均显示出足以区分空气和骨的能力，以支持从MRI数据生成合成CT。
Accurate separation of air and bone is critical for creating synthetic CT from MRI to support Radiation Oncology workflow. This study compares two different ultrashort echo-time sequences in the separation of air from bone, and evaluates post-processing methods that correct intensity nonuniformity of images and account for intensity gradients at tissue boundaries to improve this discriminatory power. CT and MRI scans were acquired on 12 patients under an institution review board-approved prospective protocol. The two MRI sequences tested were ultra-short TE imaging using 3D radial acquisition (UTE), and using pointwise encoding time reduction with radial acquisition (PETRA). Gradient nonlinearity correction was applied to both MR image volumes after acquisition. MRI intensity nonuniformity was corrected by vendor-provided normalization methods, and then further corrected using the N4itk algorithm. To overcome the intensity-gradient at air-tissue boundaries, spatial dilations, from 0 to 4 mm, were applied to threshold-defined air regions from MR images. Receiver operating characteristic (ROC) analyses, by comparing predicted (defined by MR images) versus “true” regions of air and bone (defined by CT images), were performed with and without residual bias field correction and local spatial expansion. The post-processing corrections increased the areas under the ROC curves (AUC) from 0.944 ± 0.012 to 0.976 ± 0.003 for UTE images, and from 0.850 ± 0.022 to 0.887 ± 0.012 for PETRA images, compared to without corrections. When expanding the threshold-defined air volumes, as expected, sensitivity of air identification decreased with an increase in specificity of bone discrimination, but in a non-linear fashion. A 1-mm air mask expansion yielded AUC increases of 1% and 4% for UTE and PETRA images, respectively. UTE images had significantly greater discriminatory power in separating air from bone than PETRA images. Post-processing strategies improved the discriminatory power of air from bone for both UTE and PETRA images, and reduced the difference between the two imaging sequences. Both postprocessed UTE and PETRA images demonstrated sufficient power to discriminate air from bone to support synthetic CT generation from MRI data.
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DOI：
10.1186/1748-717x-8-51
发表时间：
2013-03-06
期刊：
Radiation oncology (London, England)
影响因子：
--
作者：
Rank CM;Tremmel C;Hünemohr N;Nagel AM;Jäkel O;Greilich S
通讯作者：
Greilich S
影响因子：
10.6
作者：
Sled, JG;Zijdenbos, AP;Evans, AC
通讯作者：
Evans, AC
影响因子：
5.7
作者：
Jonsson, Joakim H.;Johansson, Adam;Nyholm, Tufve
通讯作者：
Nyholm, Tufve
影响因子：
10.6
作者：
Tustison NJ;Avants BB;Cook PA;Zheng Y;Egan A;Yushkevich PA;Gee JC
通讯作者：
Gee JC
影响因子：
3.8
作者：
Johansson, Adam;Karlsson, Mikael;Nyholm, Tufve
通讯作者：
Nyholm, Tufve