Decreased Muscular Perfusion in Dermatomyositis: Initial Results Detected by Inflow-Based Vascular-Space-Occupancy MRI

Abnormal arteriolar blood volume measured by 3D inflow-based vascular-space-occupancy (iVASO) MRI and resting-state BOLD fluctuations at 7 T in individuals with recent-onset schizophrenia

Background

We previously reported lower baseline arteriolar cerebral blood volumes (CBVa) in almost all gray matter regions in a cohort of individuals with schizophrenia of varying ages and disease duration. The extent to which decreased CBVa is also present in recent-onset schizophrenia, and how this impacts neurovascular coupling, remains to be determined. In this study, we sought to determine the extent of CBVa deficits in recent-onset schizophrenia and the relationship of CBVa to region-specific resting-state neural activity.

Methods

Using 7 T MRI, CBVa was measured in 90 regions using 3D inflow-based vascular-space-occupancy (iVASO) imaging in 16 individuals with recent-onset schizophrenia (disease duration: x̄ = 1.18 ± 1.4 years) and 12 age-matched controls. Resting-state functional MRI (rs-fMRI) was used to determine fractional amplitudes of low-frequency fluctuations (fALFF) and intrinsic connectivity (ICC) in spontaneous blood oxygen level-dependent (BOLD) signal. The region-specific relationship between CBVa and fALFF was determined as an index of neurovascular coupling.

Results

Compared with healthy participants, CBVa was lower in individuals with schizophrenia in almost all brain regions, with a global effect size of 0.23 and regional effect sizes up to 0.41. Individuals with schizophrenia also exhibited lower fALFF diffusely across cortical and subcortical gray matter regions. Ratios of mean regional CBVa to fALFF and ICC were significantly lower in patients in numerous brain regions.

Conclusion

These findings indicate that early-stage schizophrenia is characterized by widespread microvascular abnormalities and associated resting-state deficits in neural activity, suggesting that abnormalities in neurovascular coupling may contribute to the pathophysiology of schizophrenia.

On the optimization of 3D inflow-based vascular-space-occupancy (iVASO) MRI for the quantification of arterial cerebral blood volume (CBVa)

PURPOSE

The inflow-based vascular-space-occupancy (iVASO) MRI was originally developed in a single-slice mode to measure arterial cerebral blood volume (CBVa). When vascular crushers are applied in iVASO, the signals can be sensitized predominantly to small pial arteries and arterioles. The purpose of this study is to perform a systematic optimization and evaluation of a 3D iVASO sequence on both 3 T and 7 T for the quantification of CBVa values in the human brain.

METHODS

Three sets of experiments were performed in three separate cohorts. (1) 3D iVASO MRI protocols were compared to single-slice iVASO, and the reproducibility of whole-brain 3D iVASO MRI was evaluated. (2) The effects from different vascular crushers in iVASO were assessed. (3) 3D iVASO MRI results were evaluated in arterial and venous blood vessels identified using ultrasmall-superparamagnetic-iron-oxides-enhanced MRI to validate its arterial origin.

RESULTS

3D iVASO scans showed signal-to-noise ratio (SNR) and CBVa measures consistent with single-slice iVASO with reasonable intrasubject reproducibility. Among the iVASO scans performed with different vascular crushers, the whole-brain 3D iVASO scan with a motion-sensitized-driven-equilibrium preparation with two binomial refocusing pulses and an effective TE of 50 ms showed the best suppression of macrovascular signals, with a relatively low specific absorption rate. When no vascular crusher was applied, the CBVa maps from 3D iVASO scans showed large CBVa values in arterial vessels but well-suppressed signals in venous vessels.

CONCLUSION

A whole-brain 3D iVASO MRI scan was optimized for CBVa measurement in the human brain. When only microvascular signals are desired, a motion-sensitized-driven-equilibrium-based vascular crusher with binomial refocusing pulses can be applied in 3D iVASO.

Differential detection of metastatic and inflammatory lymph nodes using inflow-based vascular-space-occupancy (iVASO) MR imaging

PURPOSE

To investigate the potential value of inflow-based vascular-space-occupancy (iVASO) MR imaging in differentiating metastatic from inflammatory lymph nodes (LNs).

METHODS

Ten female New Zealand rabbits with 2.5-3.0 kg body weight were studied. VX2 cells and egg yolk emulsion were inoculated into left and right thighs, respectively, to induce ten metastatic and ten inflammatory popliteal LNs. Conventional MRI and iVASO were performed 2 h prior to, and 10, 20 days after inoculation (D0, D10, D20). The short-axis diameter (S), short- to long-axis diameter ratio (SLR), and arteriolar blood volume (BVa) at each time point and their longitudinal changes of each model were recorded and compared. At D20, all rabbits were sacrificed to perform histological evaluation after the MR scan.

RESULTS

The mean values of S, SLR and BVa showed no significant difference between the two groups at D0 (P = 0.987, P = 0.778, P = 0.975). The BVa of the metastatic group was greater than that of the inflammatory at both D10 and D20 (P < 0.05; P < 0.001), whereas the S and SLR of the metastatic group were greater only at D20 (P < 0.001; P = 0.001). Longitudinal analyses showed that the BVa of the metastatic group increased at both D10 and D20 (P = 0.004; P = 0.001), while that of the inflammatory group only increased at D10 (P = 0.024).

CONCLUSION

The BVa measured with iVASO has the potential to detect early metastatic LNs.