Relaxivity of Ferumoxytol at 1.5 T and 3.0 T

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Abstract

<div class="section"> <a class="named-anchor" id="S1">  </a> <h5 class="section-title" id="d3640817e199">Objectives</h5> To determine the relaxation properties of ferumoxytol, an off-label alternative to gadolinium based contrast agents (GBCA), under physiological conditions at 1.5T and 3.0T. </div><div class="section"> <a class="named-anchor" id="S2">  </a> <h5 class="section-title" id="d3640817e204">Materials and Methods</h5> Ferumoxytol was diluted in gradually increasing concentrations (0.26–4.2 mM) in saline, human plasma and human whole blood. MR relaxometry was performed at 37˚C at 1.5T and 3.0T. Longitudinal and transverse relaxation rate constants (R1, R2, R2*) were measured as a function of ferumoxytol concentration and relaxivities (r1, r2, r2*) were calculated. </div><div class="section"> <a class="named-anchor" id="S3">  </a> <h5 class="section-title" id="d3640817e209">Results</h5> A linear dependence of R1, R2 and R2* on ferumoxytol concentration was found in saline and plasma with lower R1 values at 3.0T and similar R2 and R2* values at 1.5T and 3.0T (1.5T: r1 saline = 19.9 ± 2.3 s −1mM −1, r1 plasma = 19.0 ± 1.7 s −1mM −1; r2 saline = 60.8 ± 3.8 s −1mM −1; r2 plasma = 64.9 ± 2.3 s −1mM −1; r2* saline = 60.4 ± 1.3 s −1mM −1; r2* plasma = 64.4 ± 0.3 s −1mM −1; 3.0T: r1 saline = 10.0 ± 0.3 s −1mM −1, r1 plasma = 9.5 ± 0.2 s −1mM −1; r2 saline = 62.3 ± 3.7 s −1mM −1; r2 plasma = 65.2 ± 1.8 s −1mM −1; r2* saline = 57.0 ± 3.6 s −1mM −1; r2* plasma = 55.7 ± 4.4 s −1mM −1). The dependence of relaxation rates on concentration in blood was nonlinear. Formulas from 2 nd order polynomial fittings of the relaxation rates were calculated to characterize the relationship between R1 blood and R2 blood with ferumoxytol. </div><div class="section"> <a class="named-anchor" id="S4">  </a> <h5 class="section-title" id="d3640817e337">Conclusions</h5> Ferumoxytol demonstrates strong longitudinal and transverse relaxivities. Awareness of the nonlinear relaxation behavior of ferumoxytol in blood is important for ferumoxytol-enhanced MRI applications and for protocol optimization. </div>

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MR imaging relaxation times of abdominal and pelvic tissues measured in vivo at 3.0 T: preliminary results.

Neil Rofsky, D Alsop, Alex de Crespigny … (2004)

To measure T1 and T2 relaxation times of normal human abdominal and pelvic tissues and lumbar vertebral bone marrow at 3.0 T. Relaxation time was measured in six healthy volunteers with an inversion-recovery method and different inversion times and a multiple spin-echo (SE) technique with different echo times to measure T1 and T2, respectively. Six images were acquired during one breath hold with a half-Fourier acquisition single-shot fast SE sequence. Signal intensities in regions of interest were fit to theoretical curves. Measurements were performed at 1.5 and 3.0 T. Relaxation times at 1.5 T were compared with those reported in the literature by using a one-sample t test. Differences in mean relaxation time between 1.5 and 3.0 T were analyzed with a two-sample paired t test. Relaxation times (mean +/- SD) at 3.0 T are reported for kidney cortex (T1, 1,142 msec +/- 154; T2, 76 msec +/- 7), kidney medulla (T1, 1,545 msec +/- 142; T2, 81 msec +/- 8), liver (T1, 809 msec +/- 71; T2, 34 msec +/- 4), spleen (T1, 1,328 msec +/- 31; T2, 61 msec +/- 9), pancreas (T1, 725 msec +/- 71; T2, 43 msec +/- 7), paravertebral muscle (T1, 898 msec +/- 33; T2, 29 msec +/- 4), bone marrow in L4 vertebra (T1, 586 msec +/- 73; T2, 49 msec +/- 4), subcutaneous fat (T1, 382 msec +/- 13; T2, 68 msec +/- 4), prostate (T1, 1,597 msec +/- 42; T2, 74 msec +/- 9), myometrium (T1, 1,514 msec +/- 156; T2, 79 msec +/- 10), endometrium (T1, 1,453 msec +/- 123; T2, 59 msec +/- 1), and cervix (T1, 1,616 msec +/- 61; T2, 83 msec +/- 7). On average, T1 relaxation times were 21% longer (P .05) in T1 relaxation time between the results of this study and the results of other studies for liver, kidney, spleen, and muscle tissue were found. T1 relaxation times are generally higher and T2 relaxation times are generally lower at 3.0 T than at 1.5 T, but the magnitude of change varies greatly in different tissues. Copyright RSNA, 2004

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Gadolinium deposition in the brain: summary of evidence and recommendations.

Vikas Gulani, Fernando Calamante, Scott B Reeder … (2017)

Emerging evidence has linked MRI signal changes in deep nuclei of the brain with repeated administration of gadolinium-based contrast agents. Gadolinium deposits have been confirmed in brain tissue, most notably in the dentate nuclei and globus pallidus. Although some linear contrast agents appear to cause greater MRI signal changes than some macrocyclic agents, deposition of gadolinium has also been observed with macrocyclic agents. However, the extent of gadolinium deposition varies between agents. Furthermore, the clinical significance of the retained gadolinium in the brain, if any, remains unknown. No data are available in human beings or animals to show adverse clinical effects due to the gadolinium deposition in the brain. On behalf of the International Society for Magnetic Resonance in Medicine, we present recommendations for the clinical and research use of gadolinium-based contrast agents. These recommendations might evolve as new evidence becomes available.

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Emerging applications for ferumoxytol as a contrast agent in MRI.

Mustafa Bashir, Lubna Bhatti, Daniele Marin … (2015)

Ferumoxytol is an ultrasmall superparamagnetic iron oxide (USPIO) agent initially approved by the Food and Drug Administration (FDA) as an iron replacement therapy for patients with anemia due to chronic renal failure. Recently, ferumoxytol has been investigated extensively as an intravenous contrast agent in magnetic resonance imaging (MRI). Since it causes regional T1 and T2 * shortening in vivo, conventional pulse sequences can be used following ferumoxytol administration to demonstrate signal enhancement or loss. Ferumoxytol can be administered as a rapid bolus and has a long intravascular half-life on the order of 14-15 hours, making it a potentially useful agent for vascular and perfusion-weighted MRI. In comparison to other USPIOs, ferumoxytol is less limited by allergic and idiosyncratic reactions. Furthermore, since ferumoxytol is an iron-based agent with no potential for causing nephrogenic systemic fibrosis, it may be useful as an alternative to gadolinium-based contrast agents in patients with compromised renal function. Ferumoxytol is ultimately taken up by macrophages/the reticuloendothelial system in the liver, spleen, and lymph nodes, and this uptake mechanism is being explored as a novel imaging technique for vascular lesions, tumors, and lymph nodes. This article reviews the properties of ferumoxytol relevant to MRI as well as many of the uses for the agent currently under investigation. © 2014 Wiley Periodicals, Inc.