John C. Wood

YNIMG Journal 2022 Journal Article

Dynamic MR imaging of cerebral perfusion during bicycling exercise

• Isa H. Mast
• Koen P.A. Baas
• Harald T. Jørstad
• John C. Wood
• Aart J. Nederveen
• Adrianus J. Bakermans

Habitual physical activity is beneficial for cerebrovascular health and cognitive function. Physical exercise therefore constitutes a clinically relevant cerebrovascular stimulus. This study demonstrates the feasibility of quantitative cerebral blood flow (CBF) measurements during supine bicycling exercise with pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI) at 3 Tesla. Twelve healthy volunteers performed a steady-state exercise-recovery protocol on an MR-compatible bicycle ergometer, while dynamic pCASL data were acquired at rest, during moderate (60% of the age-predicted supine maximal heart rate (HRmax)) and vigorous (80% of supine HRmax) exercise, and subsequent recovery. These CBF measurements were compared with 2D phase-contrast MRI measurements of blood flow through the carotid arteries. Procedures were repeated on a separate day for an assessment of measurement repeatability. Whole-brain (WB) CBF was 41. 2 ± 6. 9 mL/100 g/min at rest (heart rate 63 [57-71] beats/min), remained similar at moderate exercise (102 [97-107] beats/min), decreased by 10% to 37. 1 ± 5. 7 mL/100 g/min (p = 0. 001) during vigorous exercise (139 [136-142] beats/min) and decreased further to 34. 2 ± 6. 0 mL/100 g/min (p < 0. 001) during recovery. Hippocampus CBF decreased by 12% (p = 0. 001) during moderate exercise, decreased further during vigorous exercise (-21%; p < 0. 001) and was even lower during recovery (-31%; p < 0. 001). In contrast, motor cortex CBF increased by 12% (p = 0. 027) during moderate exercise, returned to resting-state values during vigorous exercise, and decreased by 17% (p = 0. 006) during recovery. The inter-session repeatability coefficients for WB CBF were approximately 20% for all stages of the exercise-recovery protocol. Phase-contrast blood flow measurements through the common carotid arteries overestimated the WB CBF because of flow directed to the face and scalp. This bias increased with exercise. We have demonstrated the feasibility of dynamic pCASL-MRI of the human brain for a quantitative evaluation of cerebral perfusion during bicycling exercise. Our spatially resolved measurements revealed a differential response of CBF in the motor cortex as well as the hippocampus compared with the brain as a whole. Caution is warranted when using flow through the common carotid arteries as a surrogate measure for cerebral perfusion.

YNICL Journal 2019 Journal Article

Patients with sickle-cell disease exhibit greater functional connectivity and centrality in the locus coeruleus compared to anemic controls

• Ravi R. Bhatt
• Lonnie K. Zeltzer
• Julie Coloigner
• John C. Wood
• Tom D. Coates
• Jennifer S. Labus

YNICL Journal 2017 Journal Article

Hemoglobin and mean platelet volume predicts diffuse T1-MRI white matter volume decrease in sickle cell disease patients

• Soyoung Choi
• Adam M. Bush
• Matthew T. Borzage
• Anand A. Joshi
• William J. Mack
• Thomas D. Coates
• Richard M. Leahy
• John C. Wood

Sickle cell disease (SCD) is a life-threatening genetic condition. Patients suffer from chronic systemic and cerebral vascular disease that leads to early and cumulative neurological damage. Few studies have quantified the effects of this disease on brain morphometry and even fewer efforts have been devoted to older patients despite the progressive nature of the disease. This study quantifies global and regional brain volumes in adolescent and young adult patients with SCD and racially matched controls with the aim of distinguishing between age related changes associated with normal brain maturation and damage from sickle cell disease. T1 weighted images were acquired on 33 clinically asymptomatic SCD patients (age=21. 3±7. 8; F=18, M=15) and 32 racially matched control subjects (age=24. 4±7. 5; F=22, M=10). Exclusion criteria included pregnancy, previous overt stroke, acute chest, or pain crisis hospitalization within one month. All brain volume comparisons were corrected for age and sex. Globally, grey matter volume was not different but white matter volume was 8. 1% lower (p=0. 0056) in the right hemisphere and 6. 8% (p=0. 0068) in the left hemisphere in SCD patients compared with controls. Multivariate analysis retained hemoglobin (β=0. 33; p=0. 0036), sex (β=0. 35; p=0. 0017) and mean platelet volume (β=0. 27; p=0. 016) as significant factors in the final prediction model for white matter volume for a combined r2 of 0. 37 (p<0. 0001). Lower white matter volume was confined to phylogenetically younger brain regions in the anterior and middle cerebral artery distributions. Our findings suggest that there are diffuse white matter abnormalities in SCD patients, especially in the frontal, parietal and temporal lobes, that are associated with low hemoglobin levels and mean platelet volume. The pattern of brain loss suggests chronic microvascular insufficiency and tissue hypoxia as the causal mechanism. However, longitudinal studies of global and regional brain morphometry can help us give further insights on the pathophysiology of SCD in the brain.