Background

Novel magnetic resonance (MR) imaging techniques have led to the development of T1-w/T2-w ratio images or “myelin-sensitive maps (MMs)” to estimate and compare myelin content in vivo. Currently, raw image intensities in conventional MR images are unstandardized, preventing meaningful quantitative comparisons. We propose an improved workflow to standardize the MMs, which was applied to patients with classic trigeminal neuralgia (CTN) and trigeminal neuralgia secondary to multiple sclerosis (MSTN), to assess the validity and feasibility of this clinical tool.

Methods

T1-w and T2-w images were obtained for 17 CTN patients and 17 MSTN patients using a 3 T scanner. Template images were obtained from ICBM152. Multiple sclerosis (MS) plaques in the pons were labelled in MSTN patients. For each patient image, a Gaussian curve was fitted to the histogram of its intensity distribution, and transformed to match the Gaussian curve of its template image.

Results

After standardization, the structural contrast of the patient image and its histogram more closely resembled the ICBM152 template. Moreover, there was reduced variability in the histogram peaks of the gray and white matter between patients after standardization (p < 0.001). MM intensities were decreased within MS plaques, compared to normal-appearing white matter (NAWM) in MSTN patients (p < 0.001) and its corresponding regions in CTN patients (p < 0.001).

Conclusions

Images intensities are calibrated according to a mathematic relationship between the intensities of the patient image and its template. Reduced variability among histogram peaks allows for interpretation of tissue-specific intensity and facilitates quantitative analysis. The resultant MMs facilitate comparisons of myelin content between different regions of the brain and between different patients in vivo. MM analysis revealed reduced myelin content in MS plaques compared to its corresponding regions in CTN patients and its surrounding NAWM in MSTN patients. Thus, the standardized MM serves as a non-invasive, easily-automated tool that can be feasibly applied to clinical populations for quantitative analyses of myelin content.

中文翻译：

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标准化三叉神经痛中的 T1-w/T2-w 比率图像以估计体内脱髓鞘程度

背景

新型磁共振 (MR) 成像技术导致了 T1-w/T2-w 比率图像或“髓磷脂敏感图 (MM)”的发展，以估计和比较体内髓磷脂含量。目前，传统 MR 图像中的原始图像强度未标准化，无法进行有意义的定量比较。我们提出了一种改进的工作流程来标准化 MM，将其应用于经典三叉神经痛 (CTN) 和继发于多发性硬化症 (MSTN) 的三叉神经痛患者，以评估该临床工具的有效性和可行性。

方法

使用 3 T 扫描仪获得了 17 名 CTN 患者和 17 名 MSTN 患者的 T1-w 和 T2-w 图像。模板图像来自 ICBM152。在 MSTN 患者中，脑桥中的多发性硬化 (MS) 斑块被标记。对于每个患者图像，将高斯曲线拟合到其强度分布的直方图，并对其进行变换以匹配其模板图像的高斯曲线。

结果

标准化后，患者图像及其直方图的结构对比度更接近 ICBM152 模板。此外，标准化后患者之间灰质和白质直方图峰值的变异性降低（p < 0.001）。与 MSTN 患者 ( p < 0.001 ) 和 CTN 患者的相应区域( p < 0.001)中出现正常的白质 (NAWM) 相比，MS 斑块内的 MM 强度降低。

结论

根据患者图像的强度与其模板之间的数学关系来校准图像强度。直方图峰之间的变异性降低，可以解释组织特异性强度并促进定量分析。由此产生的 MM 有助于比较大脑不同区域和体内不同患者之间的髓磷脂含量。MM 分析显示，与 CTN 患者的相应区域和 MSTN 患者周围的 NAWM 相比，MS 斑块中的髓磷脂含量降低。因此，标准化的 MM 可作为一种非侵入性、易于自动化的工具，可切实应用于临床人群，用于定量分析髓磷脂含量。