Assessment of diagnostic accuracy of perfusion MR imaging in primary and metastatic solitary malignant brain tumors

Abstract

Purpose: The purpose of this study was to estimate the diagnostic accuracy of relative cerebral blood volume (rCBV) measurement in preoperative grading and differentiation of solitary intra-axial malignant brain tumors.

Methods: Thirty-six low-grade glial tumors (LGGTs), 22 high-grade glial tumors (HGGTs), and 17 metastases (METs) were prospectively evaluated by MR imaging and standard dynamic susceptibility contrast-enhanced gradient echo, echoplanar imaging during first pass of a bolus injection of contrast material. Normalized rCBV values from tumoral (rCBV(T)) and peritumoral (rCBV(P)) areas were calculated by standard software and statistically tested independently.

Results: The mean differences of rCBV(T) and rCBV(P) values between LGGT (2.30 +/- 1.12 and 1.18 +/- 0.24) and HGGT (5.42 +/- 1.52 and 2.17 +/- 0.82) (P < .001); HGGTs and METs (3.21 +/- 0.98 and 0.97 +/- 0.09) (P < .001); and LGGTs and METs (P < .05 and P < .001, respectively) were significant. No clear cutoff value was present. A clear rCBV(T) cutoff value of 2.6 was detected for differentiation of low- (1.75 +/- 0.38; LGA) versus high-grade (4.78 +/- 0.99; HGA) astrocytomas when nonastrocytic glial tumors were excluded. The rCBV(T) values were linearly correlated with degree of malignancy (r = 0.869; P < .001). Cutoff rCBV(P) values of 1.1 and 1.2 were quite effective in differentiation of METs from LGGTs and HGGTs, respectively. The overall efficacy of rCBV was higher in grading than in differentiation.

Conclusion: The diagnostic accuracy of rCBV measurement is higher in grading of glial brain tumors than in differentiation of HGGTs from solitary intra-axial METs. The astrocytic and nonastrocytic glial tumors have to be evaluated separately for precise grading.

Fig 1.

A 22-year-old man with low-grade oligoastocytoma (WHO II) in left frontoparietal lobe. A, Axial T2-weighted spin-echo image (2295/90) shows hyperintense mass involving left insula and temporal operculum. B, Tumor does not demonstrate contrast-enhancement on axial T1-weighted image (583/15), which suggests a LGGT. C, Gradient-echo axial perfusion MR image (627/30) with rCBV color overlay map shows a low rCBV_T value of 1.50 and rCBV_P value of 1.18, in keeping with LGGTs. D, Time-signal intensity and gamma-variate fitted curves from tumoral (red), peritumoral (blue), and normal (purple) areas show prominent decrease in signal intensity from tumoral area. Decreased signal intensity in peritumoral area is at least equal to that of normal gray matter.

Fig 2.

A 22-year-old man with centrally located glioblastoma multiforme (WHO IV). A, Tumor shows heterogeneous hyperintensity with prominent peritumoral edema and/or tumoral infiltration (arrow) on axial T2-weighted SE image (2295/90). B, There is a significant heterogeneous enhancement in tumoral borders but not in peritumoral area (arrow) on axial T1-weighted image (583/15). C, Gradient-echo axial perfusion MR image (627/30) with rCBV color overlay map shows both high rCBV_T value of 6.58 and rCBV_P value of 2.21, which are consistent with HGGT. Peritumoral increased rCBV (arrow) shows tumoral infiltration outside the tumoral margins, which is not perceptible on T2- and contrast-enhanced T1-weighted images. D, Time-signal intensity and gamma-variate fitted curves from tumoral (red), peritumoral (blue), and normal (purple) areas show prominent decrease in signal intensity from tumoral and peritumoral areas, when compared with signal intensity of normal gray matter.

Fig 3.

Scatter plots of the tumoral (A–C) and peritumoral (D–E) rCBV values of different tumor groups show that higher rCBV values are linearly related to higher degree malignancy. Lines are fitted by linear regression with 95% confidence interval. LGGT indicates low-grade glial tumor; HGGT, high-grade glial tumor; MET, metastasis; LGA, low-grade astrocytoma; LGMT, low-grade mixed tumor; HGA, high-grade astrocytoma; HGMT, high-grade mixed tumor; DAS, diffuse astrocytoma; PAS, pilocytic astrocytoma; AAS, anaplastic astrocytoma; GBM, glioblastoma multiforme.

Fig 4.

Correlation plots of individual data points show linear correlation between tumoral and peritumoral rCBV values of different tumor groups. Lines are fitted by linear regression with 95% confidence interval.

Fig 5.

A 51-year-old man with cystic METs from lung carcinoma located in right temporal lobe. A, Axial T2-weighted spin-echo image (2295/90), shows hyperintense cystic mass with peritumoral edema and/or infiltration (arrows). B, Axial contrast-enhanced T1-weighted image (583/15) reveals an irregularly ringlike enhancing mass without any peritumoral contrast enhancement (arrows). C, Gradient-echo axial perfusion MR image (627/30) with rCBV color overlay map shows a high rCBV_T value of 3.05 but low rCBV_P value of 1.05, which is consistent with METs. No rCBV increase is present on peritumoral area (arrows). D, Time-signal intensity and gamma-variate fitted curves from tumoral (red), peritumoral (green), and normal (blue) areas show prominent decrease in signal intensity from tumoral area. Decreased signal intensity in peritumoral area is at least equal to or less than that of normal gray matter.

Fig 6.

A 20-year-old man with pilocytic astocytoma (WHO I) in the brain stem. A, Axial T2-weighted spin-echo image (2295/90), shows hyperintense mass involving brain stem without significant peritumoral edema. B, Tumor strongly enhances on postcontrast axial T1-weighted image (583/15), which suggests a HGGT. C, Gradient-echo axial perfusion MR image (627/30) with rCBV color overlay map shows no significant perfusion with a low rCBV_T value of 1.14 and rCBV_P value of 0.88, in keeping with a LGGT. Very low rCBV_P value helps to differentiate it from low-grade astrocytomas (WHO II). D, Time-signal intensity and gamma-variate fitted curves from tumoral (red), peritumoral (blue), and normal (yellow) areas show prominent decrease in signal intensity from tumoral area. Decreased signal intensity in peritumoral area is similar to that of normal gray matter.