Measurement of arteriolar blood volume in brain tumors using MRI without exogenous contrast agent administration at 7T

Abstract

Purpose Arteriolar cerebral-blood-volume (CBVa) is an important perfusion parameter that can be measured using inflow-based vascular-space-occupancy (iVASO) MRI without exogenous contrast agent administration. The purpose of this study is to assess the potential diagnostic value of CBVa in brain tumor patients by comparing it with total-CBV (including arterial, capillary and venous vessels) measured by dynamic-susceptibility-contrast (DSC) MRI. Methods Twelve brain tumor patients were scanned using iVASO (on 7T as part of a research project) and DSC (on 3T as part of routine clinical protocols) MRI. Region-of-interest analysis was performed to compare the resulting perfusion measures between tumoral and contralateral regions, and to evaluate their associations with tumor grades. Results CBVa measured by iVASO-MRI significantly correlated with WHO grade (ρ=0.37, P=0.04). Total-CBV measured by DSC-MRI showed a trend of correlation with WHO grade (ρ=0.28, P=0.5). Signal-to-noise ratio was comparable (P>0.1) between the two methods, while contrast-to-noise ratio between tumoral and contralateral regions was higher in iVASO-CBVa than DSC-CBV in WHO II/III patients (P<0.05) but comparable in WHO IV patients (P>0.1). A trend of positive correlation between DSC-CBV and iVASO-CBVa was observed (R2=0.28, P=0.07). Conclusion In this initial patient study, CBVa demonstrated a stronger correlation with WHO grade than total-CBV. Further investigation with a larger cohort is warranted to validate whether CBVa can be a better classifier than total-CBV for the stratification of brain tumors, and whether iVASO-MRI can be a useful alternative method for the assessment of tumor perfusion, especially when exogenous contrast agent administration is difficult in certain patient populations.

Association of Glioma Grading With Inflow‐Based Vascular‐Space‐Occupancy MRI: A Preliminary Study at 3T

“…Of note, thalamus is subject to invasion by the tumor located at midline regions or its mass effect. The ratios of both CBVa_max and nCBVa_max between different grades in our present study were comparable to those previously reported, which may indicate that the method used in the present study is reasonable and feasible …”

“…However, the measurement of CBVa is based on the arterial transit time of gray matter (GM), leading to diminished sensitivity of iVASO‐MRI in normal WM regions due to a much longer arterial transit time in WM (>2 sec). Therefore, using GM rather than WM or mirrored region (too much WM may be involved) as an internal reference is usually recommended . However, placing ROIs on cortex is subject to a partial volume effect, as well as the inclusion of large meningeal vessels.…”

“…Therefore, using GM rather than WM or mirrored region (too much WM may be involved) as an internal reference is usually recommended. 16,34 However, placing ROIs on cortex is subject to a partial volume effect, as well as the inclusion of large meningeal vessels. Therefore, we used thalamus contralateral to the tumor side in this study.…”

“…Research on the potential value of this technique in brain tumor is very limited so far. In a pilot study at 7T, CBVa derived from iVASO showed a significant correlation with glioma grade . Its clinical value in the management of cerebral gliomas needs to be further investigated.…”

“…In a pilot study at 7T, CBVa derived from iVASO showed a significant correlation with glioma grade. 16 Its clinical value in the management of cerebral gliomas needs to be further investigated. In this study we investigated the potential value of iVASO MRI in helping to determine cerebral glioma grading at 3T.…”