A comparison between blood oxygenation level‐dependent and cerebral blood volume contrast in the rat cerebral and cerebellar somatosensoric cortex during electrical paw stimulation

Abstract

To implement and optimize cerebral blood volume (CBV)-weighted functional magnetic resonance imaging (fMRI) in the rat cerebral and cerebellar cortex during electrical paw stimulation. fMRI of the cerebral and cerebellar cortex was performed during electrical paw stimulation on a 7-T MRI system (MRRS, Guilford, UK) comparing the blood oxygenation level-dependent (BOLD) and CBV-weighted contrast with different ultrasmall particles of iron oxide (USPIO) contrast doses (NC100150, 30 mg Fe/mL; Amersham Health, Oslo, Norway) and different TE. Doses of 15 and 20 mg/kg USPIO at TE = T*2 or TE = 14 msec almost doubled the contrast-to-noise ratio (CNR) of the activated areas in the cerebral cortex without affecting the overall signal-to-noise ratio (SNR) or the incidence of activation (100%). In the cerebellum the SNR decreased significantly with an increasing contrast dose. At a dose of 15 mg/kg, the CNR was slightly smaller than the CNR measured in the BOLD images, but the activation incidence seemed to be doubled. At 20 mg/kg, the CNR was slightly increased, but the activation incidence was lower. At both contrast doses the venous artifacts disappeared. A USPIO contrast dose of 20 mg/kg proved to be beneficial for fMRI in the rat, even though it affected the CNR and SNR in the cerebral and the cerebellar cortex differentially.