Abstract
Bone perfusion is an essential physiological measure reflecting vasculature status and tissue viability of the skeletal system. Arterial spin labeling (ASL), as a non-invasive and non-contrast enhanced perfusion imaging method, is an attractive approach for human research studies. To evaluate the feasibility of ASL perfusion imaging of knee bone marrow in the distal femoral condyle at a 3 T MRI scanner, a study was performed with eight healthy volunteers (three males and five females, 26 ± 2 years old) and two patients (male, 15 and 11 years old) with diagnosed stage II juvenile osteochondritis dissecans (JOCD). ASL imaging utilized a flow-sensitive alternating inversion recovery method for labeling and a single-shot fast spin echo sequence for image readout. In addition to quantitative knee bone marrow ASL imaging, studies were also performed to evaluate the effects of prolonged post-bolus delay and varied labeling size. ASL imaging was successfully performed with all volunteers. Despite the benefits of hyper-intensive signal suppression within bone marrow, the use of a prolonged post-bolus delay caused excessive perfusion signal decay, resulting in low perfusion signal-to-noise ratio (SNR) and poor image quality. Bone marrow perfusion signal changed with the labeling size, suggesting that the measured bone marrow perfusion signal is flow-associated. The means and standard deviations of bone marrow blood flow, spatial SNR, and temporal SNR from the quantitative perfusion study were 38.3 ± 5.2 mL/100 g/min, 3.31 ± 0.48, and 1.33 ± 0.31, respectively. The imaging results from JOCD patients demonstrated the potential of ASL imaging to detect disease-associated bone marrow perfusion changes. This study demonstrates that it is feasible to perform ASL imaging of knee bone marrow in the distal femoral condyle at 3 T.
Highlights
Perfusion is an essential physiological measure reflecting vasculature status and tissue viability
Study results from perfusion imaging using varied labeling sizes with three participants indicate that measured bone marrow perfusion signal changes with the size of Arterial spin labeling (ASL) labeling (Fig. 2)
Quantitative bone marrow perfusion imaging results from the study using a 600 ms post-bolus delay times (PBDs) are presented in Figs. 3 and 4: Fig. 3 shows label and control images and blood flow and noise maps from one representative participant; Fig. 4 presents a box and whiskers plot of bone marrow blood flow and spatial and temporal signal-to-noise ratio (SNR) from eight participants
Summary
Perfusion (or blood flow) is an essential physiological measure reflecting vasculature status and tissue viability. DCE MRI has been applied to measure bone marrow perfusion, the health risks of MRI with gadolinium-based contrast agents (e.g. nephrogenic systemic fibrosis)[14] have raised significant concerns for its routine applications[15]. In contrast to these imaging methods, arterial spin labeling (ASL) imaging utilizes endogenous blood water as an intrinsic agent to measure tissue perfusion[16]. As a non-radioactive, non-contrast-enhanced and non-invasive approach, ASL imaging eliminates the concerns on the exposure of ionizing radiation or the potential health risks of gadolinium-based contrast agents when they are applied for human research studies. The purpose of this study was to investigate the feasibility of knee bone marrow perfusion imaging using a pulsed ASL method at 3 T
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