BACKGROUND AND PURPOSE Quantitative susceptibility mapping has been previously used to differentiate lesions in patients with brain tumors. The aim of this work was to characterize the response of magnetic susceptibility differences in malignant brain tumors and surrounding edema to hyperoxic and hypercapnic respiratory challenges. METHODS Images of malignant brain tumor patients (2 glioblastoma multiforme, 2 anaplastic astrocytoma, 1 brain metastasis) with clinical MRI exams (contrast-enhanced T1w) were acquired at 3T. 3D multi-gradient-echo data sets were acquired while the patients inhaled medical-air (21% O2), oxygen (100% O2), and carbogen (95% O2, 5% CO2). Susceptibility maps were generated from real and imaginary data. Regions of interest were analyzed with respect to respiration-gas-induced susceptibility changes. RESULTS Contrast-enhancing tumor regions with high baseline magnetic susceptibility exhibited a marked susceptibility reduction under hyperoxic challenges, with a stronger effect (-0.040 to -0.100ppm) under hypercapnia compared to hyperoxia (-0.010 to -0.067ppm). In contrast, regions attributed to necrotic tissue and to edema showed smaller changes of opposite sign, i.e. paramagnetic shift. There was a correlation between malignant tumor tissue magnetic susceptibility at baseline under normoxia and the corresponding susceptibility reduction under hypercapnia and - to a lesser degree - under hyperoxia. CONCLUSION In this small cohort of analysis, quantification of susceptibility changes in response to respiratory challenges allowed a complementary, functional differentiation of tumorous sub-regions. Those changes, together with the correlations observed between baseline susceptibility under normoxia and susceptibility reduction with challenges, could prove helpful for a non-invasive characterization of local tumor microenvironment.

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病灶对高氧挑战的磁化反应：恶性脑肿瘤微环境的生物标志物？

背景和目的定量磁化率图谱先前已用于区分脑肿瘤患者的病变。这项工作的目的是表征恶性脑肿瘤和周围水肿的磁化率差异对高氧和高碳酸血症性呼吸挑战的反应。方法在3T时，通过临床MRI检查（对比增强的T1w）获取恶性脑肿瘤患者（多形性胶质母细胞瘤2例，间变性星形细胞瘤2例，脑转移1例）的图像。在患者吸入医用空气（21％O2），氧气（100％O2）和碳源（95％O2、5％CO2）的同时，获取了3D多梯度回波数据集。磁化率图是从真实和虚构数据生成的。分析了感兴趣区域的呼吸气体引起的磁化率变化。结果高基线磁化率的增强造影剂区域在高氧挑战下表现出显着的磁化率降低，与高氧（-0.010至-0.067ppm）相比，在高碳酸血症下效果更佳（-0.040至-0.100ppm）。相反，归因于坏死组织和水肿的区域显示出相反符号的较小变化，即顺磁位移。常氧下基线时的恶性肿瘤组织磁化率与高碳酸血症下（以及较低程度）高氧下相应的磁化率降低之间存在相关性。结论在这一小规模的分析中，对应对呼吸挑战的药敏性变化进行定量分析，可以实现肿瘤亚区域的互补，功能分化。那些变化，