Solid-State MRI as a Noninvasive Alternative to Computed Tomography for Craniofacial Imaging

摘要 计算机断层扫描(CT)已经成为手术前和术后评估的标准成像方式 患有头面部骨骼病变的儿童患者。衰减系数之间的巨大差异 骨骼和软组织允许直接分割，从而能够以高空间分辨率创建3D模型 迷幻药。然而，人们越来越担心反复暴露于电离辐射的潜在不利影响-- 在婴儿期和儿童期。事实上，FDA已经发布了警告，告诫不要进行不必要的曝光- 让儿童接受X光检查，称尽管这种风险被认为相对较小，但它仍可能导致- 导致晚年罹患癌症的风险增加。因此，CT的非辐射替代品将特别有价值- 能够识别和管理这些患者，他们在一生中需要进行多次检查。 不幸的是，传统的mr不适合于骨成像，因为骨的强度表现为接近背景的强度。 到非常短的T2弛豫时间和相对较低的质子密度，因此很难与空气区分开来。这个 这一提议的前提是一种新的固态(SS)减影成像技术，利用骨骼 在激励期间和之后的信号衰减，以交错方式与捕获屈服地收集 最大限度地保留骨骼信号，实现卓越的骨骼选择性成像。以及一种新的k空间数据共享 利用差值图像中信号的稀疏性实现压缩感知重构 领域，假设该方法将实现高分辨率的全颅骨覆盖，产生3D渲染- 在不到三分钟的扫描时间内，Ings可与他们的CT模拟产品相媲美。这一假设将被严格地 以三个具体目标进行评价，首先是全面实施图像数据采集、重建和 正在处理(目标1)。随后，该方法在人类身体头骨上进行了测试，以比较其性能。 基于颅骨测量的准确性和与黄金标准CT数据的一致性。后者是用来量化的 二值化3D渲染图像的S？renson-Dice(SD)系数和形式中的颅骨测量精度 和谐相关系数(目标2)。最后对30例儿童进行了SS-MRI检查，并对检查结果进行了分析。 临床指征在高分辨率CT引导下进行颅面外科手术的青少年(目标3)。我们假设 新的方法优于与之竞争的梯度回波成像方法，后者无法区分 骨骼和背景(例如，鼻窦中的空气)-因此称为黑骨(BB)MRI。具体的假设 有待检验的是，相对于参考CT，SS MRI方法比BB方法更准确。 基于渲染的。该项目的成功实施将产生一种临床有效、无辐射的替代方案。 目的应用CT对儿童颅面畸形患者手术前后进行评估。超越了 在拟议的试点项目范围内，经过严格评估的方法将提供通向建立的门户 建立一个生长发育期间的颅面解剖数据库，能够识别异常的表观现象 类型。

Abstract Computed tomography (CT) has been the standard imaging modality for pre- and postsurgical evaluation of pediatric patients with craniofacial skeletal pathologies. The large difference in attenuation coefficients between bone and soft tissue allows for straightforward segmentation, enabling creation of 3D models at high spatial reso- lution. However, there is growing concern about potential adverse effects of repeated exposure to ionizing radia- tion during infancy and childhood. In fact, the FDA has issued warnings cautioning against unnecessarily expos- ing children to X-rays, stating that even though the risk is deemed relatively small, it could, nonetheless, contrib- ute to increased risk of cancer later in life. As a result, non-radiative alternatives to CT would be particularly valu- able to identify and manage these patients, who require multiple examinations over the course of their lifetime. Unfortunately, conventional MR is not suited for imaging bone, which appears with near background intensity due to very short T2 relaxation times and relatively low proton density, and thus is difficult to distinguish from air. The premise underlying this proposal is that a new solid-state (SS) subtraction imaging technique, making use of bone signal attenuation during and following excitation, collected in an interleaved fashion with an acquisition yielding maximal bone signal retention, allows for superior bone-selective imaging. Along with a new k-space data sharing approach and compressed sensing reconstruction, achieved by exploiting signal sparsity in the difference image domain, it is hypothesized that the method will achieve high-resolution whole-skull coverage, yielding 3D render- ings comparable to their CT analogs in less than three minutes of scan time. This hypothesis will be rigorously evaluated in three specific Aims, starting with full implementation of image data acquisition, reconstruction and processing (Aim 1). Subsequently, the methodology is tested in human cadaver skulls to compare its performance based on craniometric accuracy and agreement with the gold-standard CT data. The latter is quantified in terms of the SØrenson-Dice (SD) coefficient of the binarized 3D-rendered images, and craniometric accuracy in the form of the concordance correlation coefficient (Aim 2). Finally, the SS-MRI method is evaluated in 30 children and ad- olescents who are clinically indicated for craniofacial surgery guided by high-resolution CT (Aim 3). We posit that the new method is superior to a competing gradient-echo imaging method that is unable to distinguish between bone and background (e.g. air in the sinuses) – therefore denoted black-bone (BB) MRI. The specific hypothesis to be tested is that the SS MRI method is more accurate than its BB counterpart with respect to the reference CT- based renderings. Successful execution of this project should result in a clinically effective, radiation-free alterna- tive to CT for the pre- and post-surgical evaluation of pediatric patients with craniofacial abnormalities. Beyond the scope of the proposed pilot project, the rigorously evaluated method will provide a gateway toward establishment of a database of craniofacial anatomy during growth and development enabling recognition of abnormal pheno- types.