Abstract
Despite a recent resurgence, intravoxel incoherent motion MRI faces practical challenges, including limited SNR and demanding acquisition and postprocessing requirements. A simplified approach using linear fitting of a subset of higher b-values has seen success in other organ systems. We sought to validate this method for evaluation of brain pathology by comparing perfusion measurements using simplified linear fitting to conventional biexponential fitting. Forty-nine patients with gliomas and 17 with acute strokes underwent 3T MRI, including DWI with 16 b-values (range, 0-900 s/mm2). Conventional intravoxel incoherent motion was performed using nonlinear fitting of the standard biexponential equation. Simplified intravoxel incoherent motion was performed using linear fitting of the log-normalized signal curves for subsets of b-values >200 s/mm2. Comparisons between ROIs (tumors, strokes, contralateral brain) and between models (biexponential and simplified linear) were performed by using 2-way ANOVA. The root mean square error and coefficient of determination (R2) were computed for the simplified model, with biexponential fitting as the reference standard. Perfusion maps using simplified linear fitting were qualitatively similar to conventional biexponential fitting. The perfusion fraction was elevated in high-grade (n = 33) compared to low-grade (n = 16) gliomas and was reduced in strokes compared to the contralateral brain (P < .001 for both main effects). Decreasing the number of b-values used for linear fitting resulted in reduced accuracy (higher root mean square error and lower R2) compared with full biexponential fitting. Intravoxel incoherent motion perfusion imaging of common brain pathology can be performed by using simplified linear fitting, with preservation of clinically relevant perfusion information.
Highlights
BACKGROUND AND PURPOSEDespite a recent resurgence, intravoxel incoherent motion MRI faces practical challenges, including limited SNR and demanding acquisition and postprocessing requirements
Intravoxel incoherent motion perfusion imaging of common brain pathology can be performed by using simplified linear fitting, with preservation of clinically relevant perfusion information
While early investigations were hampered by various technical limitations,[3] advances in field strength, gradient hardware, and echo-planar and parallel imaging technology have led to a resurgent interest in intravoxel incoherent motion (IVIM) for a wide range of clinical applications.[4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
Summary
The purpose of this study was: 1) to compare the perfusion fraction (f) estimates obtained using simplified linear fitting with those of conventional biexponential fitting, and 2) to examine the effect of reducing the number of b-values on the quality of the resulting perfusion maps
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