Objective

Amide proton transfer (APT) weighted chemical exchange saturation transfer (CEST) imaging is increasingly used to investigate high-grade, enhancing brain tumours. Non-enhancing glioma is currently less studied, but shows heterogeneous pathophysiology with subtypes having equally poor prognosis as enhancing glioma. Here, we investigate the use of CEST MRI to best differentiate non-enhancing glioma from healthy tissue and image tumour heterogeneity.

Materials & Methods

A 3D pulsed CEST sequence was applied at 3 Tesla with whole tumour coverage and 31 off-resonance frequencies (+6 to -6 ppm) in 18 patients with non-enhancing glioma. Magnetisation transfer ratio asymmetry (MTRasym) and Lorentzian difference (LD) maps at 3.5 ppm were compared for differentiation of tumour versus normal appearing white matter. Heterogeneity was mapped by calculating volume percentages of the tumour showing hyperintense APT-weighted signal.

Results

LDamide gave greater effect sizes than MTRasym to differentiate non-enhancing glioma from normal appearing white matter. On average, 17.9 % ± 13.3 % (min–max: 2.4 %–54.5 %) of the tumour volume showed hyperintense LDamide in non-enhancing glioma.

Conclusion

This works illustrates the need for whole tumour coverage to investigate heterogeneity in increased APT-weighted CEST signal in non-enhancing glioma. Future work should investigate whether targeting hyperintense LDamide regions for biopsies improves diagnosis of non-enhancing glioma.

中文翻译：

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用脉冲 3D CEST MRI 绘制 3 T 非增强型胶质瘤中的肿瘤异质性

客观的

酰胺质子转移 (APT) 加权化学交换饱和转移 (CEST) 成像越来越多地用于研究高级增强脑肿瘤。目前对非增强型胶质瘤的研究较少，但显示出异质的病理生理学，其中亚型的预后与增强型胶质瘤一样差。在这里，我们研究了使用 CEST MRI 来最好地区分非增强型胶质瘤与健康组织和图像肿瘤异质性。

材料与方法

3D 脉冲 CEST 序列在 18 名非增强型神经胶质瘤患者中以 3 特斯拉覆盖整个肿瘤和 31 个非共振频率（+6 至 -6 ppm）。比较了 3.5 ppm 的磁化传递比不对称 (MTRasym) 和洛伦兹差异 (LD) 图，以区分肿瘤与正常出现的白质。通过计算显示高信号 APT 加权信号的肿瘤体积百分比来绘制异质性。

结果

LDamide 比 MTRasym 产生更大的效果，以区分非增强型神经胶质瘤和正常出现的白质。平均而言，17.9 % ± 13.3 % (min–max: 2.4 %–54.5 %) 的肿瘤体积在非增强型胶质瘤中显示出高信号 LDamide。

结论

这项工作说明需要整个肿瘤覆盖来研究非增强型胶质瘤中增加的 APT 加权 CEST 信号的异质性。未来的工作应该调查针对活检的高信号 LDamide 区域是否可以改善非增强型胶质瘤的诊断。