Differentiation of Glioblastoma from Brain Metastasis: Qualitative and Quantitative Analysis Using Arterial Spin Labeling MR Imaging

Abstract

Purpose: To evaluate the diagnostic performance of cerebral blood flow (CBF) by using arterial spin labeling (ASL) perfusion magnetic resonance (MR) imaging to differentiate glioblastoma (GBM) from brain metastasis.

Materials and methods: The institutional review board of our hospital approved this retrospective study. The study population consisted of 128 consecutive patients who underwent surgical resection and were diagnosed as either GBM (n = 89) or brain metastasis (n = 39). All participants underwent preoperative MR imaging including ASL. For qualitative analysis, the tumors were visually graded into five categories based on ASL-CBF maps by two blinded reviewers. For quantitative analysis, the reviewers drew regions of interest (ROIs) on ASL-CBF maps upon the most hyperperfused portion within the tumor and upon peritumoral T2 hyperintensity area. Signal intensities of intratumoral and peritumoral ROIs for each subject were normalized by dividing the values by those of contralateral normal gray matter (nCBFintratumoral and nCBFperitumoral, respectively). Visual grading scales and quantitative parameters between GBM and brain metastasis were compared. In addition, the area under the receiver-operating characteristic curve was used to evaluate the diagnostic performance of ASL-driven CBF to differentiate GBM from brain metastasis.

Results: For qualitative analysis, GBM group showed significantly higher grade compared to metastasis group (p = 0.001). For quantitative analysis, both nCBFintratumoral and nCBFperitumoral in GBM were significantly higher than those in metastasis (both p < 0.001). The areas under the curve were 0.677, 0.714, and 0.835 for visual grading, nCBFintratumoral, and nCBFperitumoral, respectively (all p < 0.001).

Conclusion: ASL perfusion MR imaging can aid in the differentiation of GBM from brain metastasis.

Fig 1. Representative MR images including ASL for each visual grade.

Grade 1, no demonstrable hyperpefusion; Grade 2, minimal hyperpefusion or only scattered hyperperfused spots; Grade 3, diffuse mild hyperpefusion or moderate-to-strong hyperpefusion area occupying ≤ 1/3 of enhancing portion on CE T1WI; Grade 4, diffuse moderate hyperpefusion or strong hyperpefusion area occupying > 1/3 and ≤ 2/3 of enhancing portion on T1WI; and Grade 5, strong hyperpefusion area occupying > 2/3 of enhancing portion on T1WI. T1WI = T1-weighted images, T2WI = T2-weighted images, CE = contrast-enhanced.

Fig 2. A bar chart of relative frequency of each visual grade in GBM and brain metastasis.

GBM occupies a larger proportion of grade 5 tumors than brain metastasis, whereas brain metastasis occupies a larger proportion of grade 1 tumors than GBM.

Fig 3

Receiver operating characteristic curves for (A) visual grading, (B) nCBF_intratumoral, and (C) nCBF_peritumoral. AUC = area under the receiver operating characteristic curve, nCBF_intratumoral = maximum value of normalized intratumoral blood flow, nCBF_peritumoral = maximum value of normalized peritumoral blood flow.

Fig 4. Comparison between GBM and brain metastasis.

Axial T2WI (A and E), pre- (B and F), post- contrast (C and G) T1WI images, and ASL images (D and H, both acquired from a 1.5 T scanner (Signa HDxt; GE Healthcare)). A–D: A 66-year-old male patient with GBM. ASL images reveal strong hyperperfusion along the rim-enhancing tumor margin at the left frontal lobe. Note that apparent perfusion in the left hemisphere is lower compared to the contralateral side, suggesting a labeling artifact arising from different labeling efficiency (D). Despite this labeling variability, the peritumoral hyperperfusion is clearly seen. E–H: A 59-year-old male patient with metastatic lung cancer. No significant hyperperfusion was noted within the left temporal mass.

Fig 5. Correlation plot between visual grade and nCBF_intratumoral using one-way analysis of variance.

Horizontal lines at the top of the graph indicate the relationship between corresponding visual grades. A horizontal line with an asterisk (*) indicates that nCBF_intratumoral values between the corresponding visual grades are significantly different.