Perfusion-related parameters in intravoxel incoherent motion MR imaging compared with CBV and CBF measured by dynamic susceptibility-contrast MR technique

Abstract

Perfusion-related parameters obtained by intravoxel incoherent motion (IVIM) MR imaging (MRI) were compared with cerebral blood volume and flow (CBV and CBF), retrieved by dynamic susceptibility-contrast (DSC) MRI. Twenty-eight volunteers (average age 68.5 years) were investigated. Spin-echo echo-planar imaging with IVIM-encoding gradients was employed (36 different b values, 0-1200 s/mm2). The perfusion fraction and the pseudo-diffusion coefficient were calculated for regions in thalamus gray matter and frontal white matter, using asymptotic and full fitting. In DSC-MRI, a Gd-DTPA-BMA contrast-agent bolus was monitored using simultaneous-dual FLASH. Deconvolution of the measured tissue concentration-versus-time curve with an arterial input function from the carotid artery was applied, and maps of CBV and CBF were calculated. The correlation between the perfusion fraction and CBV was r=0.56 (p<0.0000006) using asymptotic fitting, and r=0.35 (p<0.0004) when full fitting was applied. Average CBF was 41.5 ml/(min 100 g), to be compared with the IVIM-based value of 63.6 ml/(min 100 g), obtained from the median value of the pseudo-diffusion coefficient in combination with assumptions about capillary network structure. The IVIM concept provided results that agreed reasonably with conventional CBV and CBF. The non-linear fitting to noisy signal data was problematic, in accordance with previously presented simulations.