Perfusion imaging of brain tumors using arterial spin-labeling: correlation with histopathologic vascular density

Abstract

Background and purpose: We investigated the relationship between tumor blood-flow measurement based on perfusion imaging by arterial spin-labeling (ASL-PI) and histopathologic findings in brain tumors.

Materials and methods: We used ASL-PI to examine 35 patients with brain tumors, including 11 gliomas, 9 meningiomas, 9 schwannomas, 1 diffuse large B-cell lymphoma, 4 hemangioblastomas, and 1 metastatic brain tumor. As an index of tumor perfusion, the relative signal intensity (SI) of each tumor (%Signal intensity) was determined as a percentage of the maximal SI within the tumor per averaged SI within normal cerebral gray matter on ASL-PI. Relative vascular attenuation (%Vessel) was determined as the total microvessel area per the entire tissue area on CD-34-immunostained histopathologic specimens. MIB1 indices of gliomas were also calculated. The differences in %Signal intensity among different histopathologic types and between high- and low-grade gliomas were compared. In addition, the correlations between %Signal intensity and %Vessel or MIB1 index were evaluated in gliomas.

Results: Statistically significant differences in %Signal intensity were observed between hemangioblastomas versus gliomas (P < .005), meningiomas (P < .05), and schwannomas (P < .005). Among gliomas, %Signal intensity was significantly higher for high-grade than for low-grade tumors (P < .05). Correlation analyses revealed significant positive correlations between %Signal intensity and %Vessel in 35 patients, including all 6 histopathologic types (rs = 0.782, P < .00005) and in gliomas (rs = 0.773, P < .05). In addition, in gliomas, %Signal intensity and MIB1 index were significantly positively correlated (rs = 0.700, P < .05).

Conclusion: ASL-PI may predict histopathologic vascular densities of brain tumors and may be useful in distinguishing between high- and low-grade gliomas and in differentiating hemangioblastomas from other brain tumors.

Fig 1.

Relative maximal %Signal intensity in 4 histopathologic types of brain tumors. Statistically significant differences between hemangioblastomas and gliomas (P < .005), and meningiomas (P < .05) and schwannomas (P < .005) are revealed (Kruskal-Wallis test with Scheffé post hoc analysis).

Fig 2.

Scatter chart of %Signal intensity determined by ASL-PI and the %Vessel determined by histopathologic examination with regression lines in 35 tumors of 6 histopathologic types and 11 gliomas. Note the positive correlations between %Signal intensity and %Vessel in 35 cases ({x: %Signal intensity; y: %Vessel}, y = 9.71x + 1.49, r² = 0.627; rs = 0.782, P < .00005) and in gliomas (y = 1.16x + 1.49, r² = 0.514; rs = 0.773, P < .05).

Fig 3.

Scatter chart of %Signal intensity determined by ASL-PI and MIB1 index determined by histopathologic examination with a regression line in 12 gliomas. Note the positive correlation between %Signal intensity and MIB1 index in gliomas ({x: %Signal intensity; y: %Vessel}, y = 2.30x + 1.67, r² = 0.397; rs = 0.700, P < .05).

Fig 4.

The relative maximal %Signal intensity in high- and low-grade gliomas. Note the significant difference between high- and low-grade gliomas (P < .05).

Fig 5.

A 61-year-old woman with hemangioblastoma; postcontrast T1WI (TR/TE = 525/17 ms) (A), T2WI (2500/15 ms) (B), perfusion image by ASL (C), and CD-34–immunostained histopathologic specimen with the dark gray color overlaid on vessel lumen areas (×20) (D). A, Postcontrast T1WI shows a strongly enhanced mass (arrow) in the right cerebellar hemisphere. B, T2WI shows a high-signal-intensity mass (arrow) with surrounding edema. C, Perfusion image by ASL shows remarkably high signal intensity (%Signal intensity = 524%) (arrow). D, The image analysis of the CD-34–immunostained histopathologic specimen shows attenuated vascular proliferation (%Vessel = 36.0%).

Fig 6.

A 44-year-old woman with glioblastoma; postcontrast T1WI (591/17 ms) (A), T2WI (2800/93 ms) (B), perfusion image by ASL (C), and CD-34–immunostained histopathologic specimen with the dark gray color overlaid on vessel lumen areas (×20) (D). A, Postcontrast T1WI reveals a ringlike enhancing mass (arrow) in the left cerebral hemisphere. B, T2WI shows the high-intensity mass (arrow) with peritumoral edema. C, On the perfusion image by ASL, the tumor was depicted as a high-intensity area (%Signal intensity = 265%) with a central low perfusion area (arrow). Image analysis of the CD-34–immunostained histopathologic specimen shows scattered vascular proliferation (%Vessel = 2.97%).