Investigating the effect of blood susceptibility on phase contrast in the human brain

Fast high resolution whole brain T2* weighted imaging using echo planar imaging at 7T

“…Further reduction in scan time is expected from coils with more receive elements, which will allow for higher acceleration factors from parallel imaging. 3D EPI allows fast mapping of phase contrast and can hence contribute to research on the origins of this contrast (Petridou et al, 2010), as well as to accurate susceptibility mapping . 3D EPI using non-isotropic voxel sizes may prove beneficial for venography based on susceptibility-weighted imaging (Haacke et al, 2004).…”

Multi-echo fMRI of the cortical laminae in humans at 7T

“…This issue has been extensively investigated in literature Lee et al, 2010;Petridou et al, 2010) in an attempt to explain the difference in signal-phase between WM and Two profiles are highlighted, one that is oriented parallel to the voxel matrix (green) and one that is oriented obliquely at approximately 45°. On the right the sampled profiles are shown where the black dots indicate the voxels' centres of masses.…”

“…the static magnetic field perturbation), it is highly likely that any cause explaining why there are laminar variations in the phase of gradient-echo images is also responsible for these variations showing up in our T 2 ⁎ profiles. The consensus is that the phase effects mentioned cannot be explained by blood susceptibility Petridou et al, 2010) and are likely caused by myeloarchitecture . This is supported by comparing the T 2 ⁎ profile in Fig.…”

Characterizing the contrast of white matter and grey matter in high-resolution phase difference enhanced imaging of human brain at 3.0 T

“…The contrast observed between cortex and white matter (arrows) is substantially greater in TE (b; grade=3) than in VE (a; grade=1) or PADRE (c; grade=2) images Although the contrast both between and within grey and white matter could be observed with the PADRE technique, its precise origin is still unknown. Several potential mechanisms, including deoxyhaemoglobin [24,25], iron concentration [20,26], and myelin [27,28], have been suggested.…”

“…The paramagnetic deoxygenated red blood cells in the capillary bed and intracortical venules may contribute substantial phase shifts in grey matter. However, investigations in both humans and rats [24,25] have suggested that the contribution of intravascular deoxyhaemoglobin to the phase contrast of grey and white matter is relatively small, even negligible. In our study, VE images that selectively enhanced the negative phase contrast-which arises mainly from the veins-showed poor contrast between white matter and cortical grey matter, potentially further excluding the notion of deoxyhaemoglobin dependence.…”