Brain Imaging Center, University Frankfurt, Germany.
Neuroimage. 2012 Oct 15;63(1):540-52. doi: 10.1016/j.neuroimage.2012.06.076. Epub 2012 Jul 14.
Most methods for mapping proton densities (PD) in brain tissue are based on measuring all parameters influencing the signal intensity with subsequent elimination of any weighting not related to PD. This requires knowledge of the receiver coil sensitivity profile (RP), the measurement of which can be problematic. Recently, a method for compensating the influence of RP non-uniformities on PD data at a field strength of 3T was proposed, based on bias field correction of spoiled gradient echo image data to remove the low spatial frequency bias imposed by RP variations from uncorrected PD maps. The purpose of the current study was to present and test an independent method, based on the well-known linear relationship between the longitudinal relaxation rate R1 and 1/PD in brain tissue. For healthy subjects, RP maps obtained with this method and the resulting PD maps are very similar to maps based on bias field correction, and quantitative PD values acquired with the new independent method are in very good agreement with literature values. Furthermore, both methods for PD mapping are compared in the presence of several pathologies (multiple sclerosis, stroke, meningioma, recurrent glioblastoma).
大多数用于绘制脑组织质子密度（PD）的方法都基于测量影响信号强度的所有参数，随后消除与 PD 无关的任何加权。这需要了解接收线圈灵敏度分布（RP），但测量 RP 可能会出现问题。最近，提出了一种在 3T 场强下补偿 RP 不均匀性对 PD 数据影响的方法，该方法基于对spoiled gradient echo 图像数据的偏置场校正，以消除由 RP 变化引起的未校正 PD 图中低空间频率偏置。本研究的目的是提出并测试一种基于组织中纵向弛豫率 R1 和 1/PD 之间的已知线性关系的独立方法。对于健康受试者，用该方法获得的 RP 图和由此产生的 PD 图与基于偏置场校正的图非常相似，用新的独立方法获得的定量 PD 值与文献值非常吻合。此外，在存在多种疾病（多发性硬化、中风、脑膜瘤、复发性胶质母细胞瘤）的情况下比较了这两种 PD 绘图方法。
