Differentiation of glioblastoma multiforme and single brain metastasis by peak height and percentage of signal intensity recovery derived from dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging

Abstract

Background and purpose: Glioblastoma multiforme (GBM) and single brain metastasis (MET) are the 2 most common malignant brain tumors that can appear similar on anatomic imaging but require vastly different treatment strategy. The purpose of our study was to determine whether the peak height and the percentage of signal intensity recovery derived from dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion MR imaging could differentiate GBM and MET.

Materials and methods: Forty-three patients with histopathologic diagnosis of GBM (n=27) or MET (n=16) underwent DSC perfusion MR imaging in addition to anatomic MR imaging before surgery. Regions of interest were drawn around the nonenhancing peritumoral T2 lesion (PTL) and the contrast-enhancing lesion (CEL). T2* signal intensity-time curves acquired during the first pass of gadolinium contrast material were converted to the changes in relaxation rate to yield T2* relaxivity (Delta R2*) curve. The peak height of maximal signal intensity drop and the percentage of signal intensity recovery at the end of first pass were measured for each voxel in the PTL and CEL regions of the tumor.

Results: The average peak height for the PTL was significantly higher (P=.04) in GBM than in MET. The average percentage of signal intensity recovery was significantly reduced in PTL (78.4% versus 82.8%; P=.02) and in CEL (62.5% versus 80.9%, P<.01) regions of MET compared with those regions in the GBM group.

Conclusions: The findings of our study show that the peak height and the percentage of signal intensity recovery derived from the Delta R2* curve of DSC perfusion MR imaging can differentiate GBM and MET.

Fig 1.

A 46-year-old man with right parietal and corpus callosal GBM. Transverse T2* susceptibility echo-planar perfusion image (left) and contrast-enhanced SPGR T1-weighted image (right) (A) and corresponding T2* susceptibility signal intensity time curves of T2 lesion (red) and contrast-enhancing lesion (green) (B) demonstrate variation in signal intensity characteristics in the tumor. T2* susceptibility signal intensity time curve (C, left) is converted to ΔR2* curve (right) by using the following formula: ΔR2* = −ln(S_t/S₀)/TE, where ln is natural log and S_t and S₀ are signal intensities at time t and 0. In the ΔR2* curve (right), the peak height is represented as a, and the percentage of signal intensity recovery is the percentile of b/a. Transverse contrast-enhanced SPGR T1-weighted image (D) is overlaid with areas of abnormal peak height (blue) and percentage of signal intensity recovery less than 50% (red) and shows a large area of increased vascularity (blue) with a peripheral region of high permeability (red) in this GBM.

Fig 2.

Left occipital single breast cancer metastasis in a 62-year-old woman. Transverse contrast-enhanced SPGR T1-weighted image (left) and a strip of T2* susceptibility signal intensity time curve through normal brain and left occipital metastatic brain tumor demonstrate increased peak height and marked loss in signal intensity recovery in the tumor (2 voxels on right) consistent with vascular and permeable metastatic tumor vasculature.

Fig 3.

Axial contrast-enhanced SPGR T1-weighted images (left) and T2* relaxivity signal intensity time curves (right) in GBM (A) and breast cancer metastasis (B) show a marked difference in percentage of signal intensity recovery at the end of the first pass where GBM has far more than 50% signal intensity recovery to the baseline compared with the metastasis.

Fig 4.

Abnormal peak height and percentage of signal intensity recovery maps in a GBM (A) and a breast cancer metastasis (B). The blue overlay represents an area of abnormal peak height (greater than twice the normal brain) and pink overlay depicts area of less than 50% signal intensity recovery of T2* relaxivity curve. A, Top row, left frontal GBM in a 45-year-old man. Axial (2 left images) and coronal (2 right images) contrast-enhanced T1-weighted images show a large area of peak height abnormality (blue) but only a small area of less than 50% signal intensity recovery (arrow, pink), suggesting highly vascular but not permeable vessels. B, Bottom row, left occipital breast cancer metastasis in a 62-year-old woman. Axial (2 left images) and coronal (2 right images) contrast-enhanced T1-weighted images demonstrate large areas of both abnormal peak height (blue) and less than 50% signal intensity recovery (pink), suggesting vascular but also highly permeable microvasculature of the metastatic tumor.

Fig 5.

Estimated probability and observed glioma (GBM) curve based on logistic regression analysis. Y-axis represents the estimated probability that a tumor is not a GBM, and the x-axis represents the average percentage of signal intensity recovery (celAvg_Recov) within the contrast-enhancing lesion of the tumor. This curve shows that when a cutoff of ≤66% signal intensity recovery is used, there is 100% specificity to correctly predict that a tumor is not a GBM with a sensitivity of 69%. The small circle (○) represents GBM, and the plus sign (+) represents metastasis. The shaded area is the confidence interval.