Cardiovascular MRI with ferumoxytol

Abstract

The practice of contrast-enhanced magnetic resonance angiography (CEMRA) has changed significantly in the span of a decade. Concerns regarding gadolinium (Gd)-associated nephrogenic systemic fibrosis in those with severely impaired renal function spurred developments in low-dose CEMRA and non-contrast MRA as well as efforts to seek alternative MR contrast agents. Originally developed for MR imaging use, ferumoxytol (an ultra-small superparamagnetic iron oxide nanoparticle), is currently approved by the US Food and Drug Administration for the treatment of iron deficiency anaemia in adults with renal disease. Since its clinical availability in 2009, there has been rising interest in the scientific and clinical use of ferumoxytol as an MR contrast agent. The unique physicochemical and pharmacokinetic properties of ferumoxytol, including its long intravascular half-life and high r1 relaxivity, support a spectrum of MRI applications beyond the scope of Gd-based contrast agents. Moreover, whereas Gd is not found in biological systems, iron is essential for normal metabolism, and nutritional iron deficiency poses major public health challenges worldwide. Once the carbohydrate shell of ferumoxytol is degraded, the elemental iron at its core is incorporated into the reticuloendothelial system. These considerations position ferumoxytol as a potential game changer in the field of CEMRA and MRI. In this paper, we aim to summarise our experience with the cardiovascular applications of ferumoxytol and provide a brief synopsis of ongoing investigations on ferumoxytol-enhanced MR applications.

Figure1 (A-E)

A 90 year old male patient with renal failure undergoing vascular evaluation for transcatheter aortic valve replacement (TAVR). First pass imaging with ferumoxytol (A,C) on thin maximum intensity projection (MIP) (A) and volume rendered (VR) (C) reconstructions show similar bright and uniform arterial enhancement as on steady state images (B,D,E), where arteries and veins show equal signal intensity. In E, the systemic veins have been made more transparent. Note extensive irregularity and tortuosity in the aorto-iliac vessels. This study was acquired at 3.0T.

Figure1 (A-E)

A 90 year old male patient with renal failure undergoing vascular evaluation for transcatheter aortic valve replacement (TAVR). First pass imaging with ferumoxytol (A,C) on thin maximum intensity projection (MIP) (A) and volume rendered (VR) (C) reconstructions show similar bright and uniform arterial enhancement as on steady state images (B,D,E), where arteries and veins show equal signal intensity. In E, the systemic veins have been made more transparent. Note extensive irregularity and tortuosity in the aorto-iliac vessels. This study was acquired at 3.0T.

Figure 2 (A-C)

A 53 year old female with chronic, treated type A dissection and an endovascular thoracic aortic stent had ferumoxytol imaging because of severe renal impairment. Thin MIP images in A show the vascular enhancement status on first pass (left), two minutes post injection (middle) and one hour post injection. Differential enhancement of true and false (arrows) lumens is obvious on first pass, with uniform and stable enhancement of both lumens once the steady state is established. Volume rendered images of the first pass (B) and steady state (C) distribution phases show substantially similar anatomic information. Note the outline of the endovascular stent struts in the thoracic aorta. This study was acquired at 3.0T.

Figure 2 (A-C)

A 53 year old female with chronic, treated type A dissection and an endovascular thoracic aortic stent had ferumoxytol imaging because of severe renal impairment. Thin MIP images in A show the vascular enhancement status on first pass (left), two minutes post injection (middle) and one hour post injection. Differential enhancement of true and false (arrows) lumens is obvious on first pass, with uniform and stable enhancement of both lumens once the steady state is established. Volume rendered images of the first pass (B) and steady state (C) distribution phases show substantially similar anatomic information. Note the outline of the endovascular stent struts in the thoracic aorta. This study was acquired at 3.0T.

Figure 2 (A-C)

A 53 year old female with chronic, treated type A dissection and an endovascular thoracic aortic stent had ferumoxytol imaging because of severe renal impairment. Thin MIP images in A show the vascular enhancement status on first pass (left), two minutes post injection (middle) and one hour post injection. Differential enhancement of true and false (arrows) lumens is obvious on first pass, with uniform and stable enhancement of both lumens once the steady state is established. Volume rendered images of the first pass (B) and steady state (C) distribution phases show substantially similar anatomic information. Note the outline of the endovascular stent struts in the thoracic aorta. This study was acquired at 3.0T.

Figure 3

A 64 year old female with a pacemaker and renal impairment undergoing evaluation for TAVR placement. Pre-contrast black blood HASTE images (top row) show extensive intravascular signal due to slow flow, despite double inversion pulses. Post-ferumoxytol HASTE images (bottom row) with exactly the same parameters show complete suppression of the intravascular and intracardiac blood signal. This study was acquired at 1.5T.

Figure 4 (A,B)

An 87 year old male with aortic stenosis, sinus bradycardia and renal transplant undergoing evaluation for TAVR placement. Volume rendered images in the steady state distribution of ferumoxytol (A) display the entire aorto-iliac anatomy as well as the patent renal transplant artery and vein in the pelvis. Gated, spoiled gradient echo cine images show the aortic valve leaflets and the relationship of the left coronary artery ostium to the annulus (B).

Figure 4 (A,B)

An 87 year old male with aortic stenosis, sinus bradycardia and renal transplant undergoing evaluation for TAVR placement. Volume rendered images in the steady state distribution of ferumoxytol (A) display the entire aorto-iliac anatomy as well as the patent renal transplant artery and vein in the pelvis. Gated, spoiled gradient echo cine images show the aortic valve leaflets and the relationship of the left coronary artery ostium to the annulus (B).

Figure 5

A 46 year old female with end stage renal failure and liver disease with extensive venous thrombosis. Undergoing evaluation for organ transplantation. Volume rendered acquisition with steady state ferumoxytol (left and right frames) show detailed vascular anatomy of the thorax, abdomen and pelvis, including a hugely dilated left gonadal vein and pelvic varices. A CT venogram (middle frame) performed shortly prior to MRI suffers from contrast dilution with poorer vascular definition. Note the left sided venous catheter extending proximally through the occluded IVC. The MRI study was acquired at 3.0T.

Figure 6

A 19 month old male with stridor and no prior history of congenital heart disease. Volume rendered reconstruction from a single frame of a 4-D MUSIC acquisition (6A) from the anterior (left frame) and superior (right frame) perspective show a complete vascular ring due to a double arch, with normal cardiac chamber anatomy. Labels: RA right atrium; RV right ventricle; LV left ventricle, Ao ascending aorta; DAo descending aorta; LCCA left common carotid artery; RCCA right common carotid artery. Dynamic evaluation of the 4D MUSIC data confirmed compression of the trachea, summarized in 6B. This study was acquired at 3.0T.

Figure 6

A 19 month old male with stridor and no prior history of congenital heart disease. Volume rendered reconstruction from a single frame of a 4-D MUSIC acquisition (6A) from the anterior (left frame) and superior (right frame) perspective show a complete vascular ring due to a double arch, with normal cardiac chamber anatomy. Labels: RA right atrium; RV right ventricle; LV left ventricle, Ao ascending aorta; DAo descending aorta; LCCA left common carotid artery; RCCA right common carotid artery. Dynamic evaluation of the 4D MUSIC data confirmed compression of the trachea, summarized in 6B. This study was acquired at 3.0T.