Susceptibility weighted imaging and quantitative susceptibility mapping of the cerebral vasculature using ferumoxytol

Abstract

Purpose To demonstrate the potential of imaging cerebral arteries and veins with ferumoxytol using susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM). Materials and Methods The relationships between ferumoxytol concentration and the apparent susceptibility at 1.5T, 3T, and 7T were determined using phantom data; the ability of visualizing subvoxel vessels was evaluated using simulations; and the feasibility of using ferumoxytol to enhance the visibility of small vessels was confirmed in three healthy volunteers at 7T(with doses 1 mg/kg to 4 mg/kg). The visualization of the lenticulostriate arteries and the medullary veins was assessed by two raters and the contrast-to-noise ratios (CNRs) of these vessels were measured. Results The relationship between ferumoxytol concentration and susceptibility was linear with a slope 13.3 ± 0.2 ppm·mg−1·mL at 7T. Simulations showed that SWI data with an increased dose of ferumoxytol, higher echo time (TE), and higher imaging resolution improved the detection of smaller vessels. With 4 mg/kg ferumoxytol, voxel aspect ratio = 1:8, TE = 10 ms, the diameter of the smallest detectable artery was approximately 50µm. The rating score for arteries was improved from 1.5 ± 0.5 (precontrast) to 3.0 ± 0.0 (post-4 mg/kg) in the in vivo data and the apparent susceptibilities of the arteries (0.65 ± 0.02 ppm at 4 mg/kg) agreed well with the expected susceptibility (0.71 ± 0.05 ppm). Conclusion The CNR for cerebral vessels with ferumoxytol can be enhanced using SWI, and the apparent susceptibilities of the arteries can be reliably quantified using QSM. This approach improves the imaging of the entire vascular system outside the capillaries and may be valuable for a variety of neurodegenerative diseases which involve the microvasculature.

Measurements of cerebral blood volume using quantitative susceptibility mapping, R2* relaxometry, and ferumoxytol‐enhanced MRI

“…However, QSM CBV estimates were similar to both R 2 *‐based approaches and no significant differences between CBV methods was found. It is likely that QSM underestimates susceptibility changes in venous blood after injecting ferumoxytol, as was observed in another study that injected a total dose of 4 mg FE/kg . In that study, researchers attributed the underestimation of venous blood susceptibility changes to problems with increased phase aliasing and effective vessel diameter.…”

“…It is likely that QSM underestimates susceptibility changes in venous blood after injecting ferumoxytol, as was observed in another study that injected a total dose of 4 mg FE/kg. 24 In that study, researchers attributed the underestimation of venous blood susceptibility changes to problems with increased phase aliasing and effective vessel diameter. In this study we used a multi-echo imaging approach, compared with the single-echo approach used in that study.…”

“…The application of QSM to steady‐state CBV mapping holds the potential to provide a more direct relationship to contrast concentration. Recent studies on blood pool contrast agents, such as ferumoxytol, in QSM‐based susceptibility have been encouraging, showing improvements in cerebrovascular imaging and iron quantification; however, QSM performance and solver dependence for imaging the microvasculature has not been extensively investigated.…”

Simultaneous MRI water‐fat separation and quantitative susceptibility mapping of carotid artery plaque pre‐ and post‐ultrasmall superparamagnetic iron oxide‐uptake

“…QSM removes blooming artifacts and background field effects and can directly quantify USPIO uptake. It has previously been shown that tissue susceptibility increases linearly with the concentration of USPIOs . Therefore, using a previously established scaling factor of 59.6 ppm mL/mg at 1.5T, it can be estimated that the plaques scanned in this study contained a mean concentration of 22 ± 10 µg/mL.…”

“…It has previously been shown that tissue susceptibility increases linearly with the concentration of USPIOs . Therefore, using a previously established scaling factor of 59.6 ppm mL/mg at 1.5T, it can be estimated that the plaques scanned in this study contained a mean concentration of 22 ± 10 µg/mL. For quantitative analysis it would be necessary to acquire a precontrast scan to determine the baseline susceptibility value within the plaque and determine the increase created by the USPIO uptake.…”