title: Increased blood oxygen level-dependent (BOLD) sensitivity in the mouse somatosensory cortex during electrical forepaw stimulation using a cryogenic radiofrequency probe.
abstract: Functional MRI (fMRI) based on the blood oxygen level-dependent (BOLD) contrast is widely used in preclinical neuroscience. The small dimensions of rodent brain place high demands on spatial resolution, and hence on the sensitivity of the fMRI experiment. This work investigates the performance of a 400-MHz cryogenic quadrature transceive radiofrequency probe (CryoProbe) with respect to the enhancement of the BOLD sensitivity. For this purpose, BOLD fMRI experiments were performed in mice during electrical forepaw stimulation using the CryoProbe and a conventional room temperature surface coil of comparable dimensions. Image signal-to-noise ratio (SNR) and temporal SNR were evaluated as quality measures for individual images and for fMRI time series of images, resulting in gains (mean ± standard deviation) with factors of 3.1 ± 0.7 and 1.8 ± 1.0 when comparing the CryoProbe and room temperature coil. The CryoProbe thermal shield temperature did not affect the noise characteristics, with temporal noise levels being 63 ± 16% of the corresponding room temperature value. However, a significant effect on BOLD amplitudes was found, which was attributed to temperature-dependent baseline cerebral blood volumes. Defined local thermal conditions were found to be a critical parameter for achieving an optimal and reproducible fMRI signal. In summary, the CryoProbe represents an attractive alternative for the enhancement of image SNR, temporal SNR and BOLD sensitivity in mouse fMRI experiments.
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Switzerland.
authors.forename: Christof
authors.initials: C
authors.lastname: Baltes
authors.forename: Simone
authors.initials: S
authors.lastname: Bosshard
authors.forename: Thomas
authors.initials: T
authors.lastname: Mueggler
authors.forename: David
authors.initials: D
authors.lastname: Ratering
authors.forename: Markus
authors.initials: M
authors.lastname: Rudin
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology; D001931:Brain Mapping; D003080:Cold Temperature; D004558:Electric Stimulation; D005260:Female; D005552:Forelimb / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D010100:Oxygen / Q000097:blood*; D011846:Radio Waves; D012535:Scalp / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D013113:Spin Labels
chemical_list: D013113:Spin Labels; D010100:Oxygen