Equilibrium-phase MR angiography of the aortoiliac and renal arteries using a blood pool contrast agent

Contrast-enhanced MR Angiography without Gadolinium-based Contrast Material: Clinical Applications Using Ferumoxytol

Vascular imaging can be challenging because of the wide variability of contrast dynamics in different vascular territories and potential safety concerns in patients with renal insufficiency or allergies. Off-label diagnostic use of ferumoxytol, a superparamagnetic iron nanoparticle approved for therapy, is a promising alternative to gadolinium-based contrast agents for MR angiography (MRA). Ferumoxytol has exhibited a reassuring safety profile when used within the dose range recommended for diagnostic imaging. Because of its prolonged and stable intravascular residence, ferumoxytol can be used in its steady-state distribution for a wide variety of imaging indications, including some where conventional MRA is unreliable. In this article, authors discuss some of the major vascular applications of ferumoxytol and highlight how it may be used to provide highly diagnostic images and improve the quality, workflow, and reliability of vascular imaging. Keywords: MR Angiography, MRI Contrast Agent, Cardiac, Vascular © RSNA, 2022.

A Comprehensive Updated Review on Magnetic Nanoparticles in Diagnostics

Magnetic nanoparticles (MNPs) have been studied for diagnostic purposes for decades. Their high surface-to-volume ratio, dispersibility, ability to interact with various molecules and superparamagnetic properties are at the core of what makes MNPs so promising. They have been applied in a multitude of areas in medicine, particularly Magnetic Resonance Imaging (MRI). Iron oxide nanoparticles (IONPs) are the most well-accepted based on their excellent superparamagnetic properties and low toxicity. Nevertheless, IONPs are facing many challenges that make their entry into the market difficult. To overcome these challenges, research has focused on developing MNPs with better safety profiles and enhanced magnetic properties. One particularly important strategy includes doping MNPs (particularly IONPs) with other metallic elements, such as cobalt (Co) and manganese (Mn), to reduce the iron (Fe) content released into the body resulting in the creation of multimodal nanoparticles with unique properties. Another approach includes the development of MNPs using other metals besides Fe, that possess great magnetic or other imaging properties. The future of this field seems to be the production of MNPs which can be used as multipurpose platforms that can combine different uses of MRI or different imaging techniques to design more effective and complete diagnostic tests.

Ferucarbotran-loaded red blood cells as long circulating MRI contrast agents: first in vivo results in mice

AIM

The encapsulation of superparamagnetic iron oxide contrast agents in red blood cells (RBCs) could overcome their rapid removal by reticulo-endothelial system improving their stability in blood circulation.

MATERIALS & METHODS

Murine ferucarbotran-loaded RBCs were tested in vivo as new contrasting agents in MRI application.

RESULTS

A superior visualization of organs and cerebral vessels was evidenced in ferucarbotran-loaded RBCs-treated mice compared with the controls. The signal enhancement lasted for days, while the contrast from bulk ferucarbotran disappeared after few minutes.

CONCLUSION

Ferucarbotran-loaded RBCs showed to improve diagnostic imaging and their use may extend the time frame for MRI and magnetic resonance angiography since to date the time frame for data acquisition has been limited to the first pass.

Alternatives to GBCA: Are We There Yet?

Gadolinium has been widely used as the contrast agent of choice for magnetic resonance imaging (MRI). However, gadolinium administration is not always desired due to its inherent enhancement properties and potential side effects (nephrogenic systemic fibrosis). This article reviews gadolinium alternatives, iron-, and manganese- based agents, and their current clinical usage for contrast-enhanced MRI examinations.

Prolonged in vivo circulation time by zwitterionic modification of magnetite nanoparticles for blood pool contrast agents

Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron oxide particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoparticles via EDC/NHS [N-(3-dimethylaminopropyl)-N'-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic particles demonstrated five times lower macrophage cell uptake than the original particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoparticles had much longer in vivo circulation time than the original particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoparticles with carboxyl surface and to prolong their circulating time.

Basics of Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy

In this chapter, the basic principles of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) (Sects. 2.2, 2.3, and 2.4), the technical components of the MRI scanner (Sect. 2.5), and the basics of contrast agents and the application thereof (Sect. 2.6) are described. Furthermore, flow phenomena and MR angiography (Sect. 2.7) as well as diffusion and tensor imaging (Sect. 2.7) are elucidated.

Renal MR angiography

The high accuracy of renal MR angiography makes it well suited for diagnosing renal vascular disease. A comprehensive examination includes three-dimensional gadolinium MR angiography to assess lumenal anatomy and functional techniques to assess the hemodynamic significance of any stenosis identified. Postprocessing is critical to provide reformations, maximum intensity projections, and optional volume-rendered images to display arteries in an angiographic format for optimal demonstration of any vascular lesions. It is important to review source images to avoid missing pathologic findings. As MR imaging continues to develop, the renal MR angiography examination will likely expand to include extensive functional information about creatinine clearance, flow, and response to pharmacologic agents as well as spectroscopy, diffusion, perfusion, phase contrast, and other techniques.

Value of a blood pool contrast agent in MR venography of the lower extremities and pelvis: Preliminary results in 12 patients

The purpose of this study was to determine the value of a blood-pool contrast media (NC100150, Nycomed Imaging (now Amersham Health) Oslo, Norway) for evaluation of venous thrombosis of the deep veins of the pelvis and lower extremities. Twelve patients were prospectively evaluated with conventional X-ray venography (XRV) and MR venography (MRV) after injection of NC100150 (2 ml/kg body weight). The source images and 3D maximum intensity projection (MIP) were viewed on an independent workstation. Diagnosis was made in consensus from two radiologists. Diagnostic image quality was achieved in 87 veins with XRV and MRV. As determined by XRV, thrombus was present in 30 out of 87 veins (34.5%). There was agreement concerning absence or presence of thrombi in 83 out of 87 veins (95.4%; kappa = 0.9 +/- 0.05). Compared to XRV, overall sensitivity and specificity of blood-pool MRV were 93.3% and 96.5%, respectively. Two venous thromboses of the popliteal and posterior tibial vein were diagnosed in MRV, but not in XRV. Conversely, two venous thromboses below the knee had been missed by MRV. NC100150 allows prolonged and improved visualization of the peripheral vasculature and may overcome some limitations of gadolinium contrast media. A more complete examination of the proximal venous tree may be possible than with conventional XRV. Arterial and venous enhancement and motion artifacts can limit image interpretation.

Multicenter phase-II trial of safety and efficacy of NC100150 for steady-state contrast-enhanced peripheral magnetic resonance angiography

The aim of this study was to test the safety and efficacy of NC100150 injection for steady-state contrast-enhanced peripheral MR angiography in a multicentre phase-II trial. Thirty-three patients underwent steady-state NC100150 enhanced MR angiography (5 mg Fe/kg body weight) of the aortoiliac and femoropopliteal arteries. Safety assessment consisted of pre- and post-injection (2, 24 and 72 h) monitoring of vital signs, physical examination as well as laboratory and electrocardiographic parameters. To determine sensitivity and specificity for detection of haemodynamically significant stenoses (HSS; >50% reduction of luminal diameter) MR angiograms were compared with intra-arterial digital subtraction angiography (IA DSA), which was considered the standard of reference. In 33 patients a mean of 12.8 ml NC100150 was injected. Eleven patients reported 13 mild and 2 moderate adverse events. Five mild and one moderate adverse event were considered due to NC100150 injection. There were no significant changes in vital signs, laboratory or electrocardiographic parameters. Sensitivity and specificity (in percent) for detection of HSS were 87 and 64, 56 and 76, and 75 and 84, for iliac, femoral and popliteal arteries, respectively. NC100150 high-resolution steady-state MR angiography can be performed safely and is feasible for the detection of peripheral arterial HSS, but is as yet not a clinically useful alternative to conventional gadolinium-enhanced MR angiography.

Cost-effectiveness targets for multi-detector row CT angiography in the work-up of patients with intermittent claudication

PURPOSE

To determine the costs, sensitivity for detection of significant stenoses, and proportion of equivocal multi-detector row computed tomographic (CT) angiography results in the work-up of patients with intermittent claudication that would make this imaging examination cost-effective compared with gadolinium-enhanced magnetic resonance (MR) angiography.

MATERIALS AND METHODS

A decision model was used to compare the societal cost-effectiveness of a new imaging modality with that of gadolinium-enhanced MR angiography. Main outcome measures were quality-adjusted life years (QALYs) and lifetime costs. By using threshold analysis of a given willingness to pay per QALY, target values for costs, sensitivity for detection of significant stenoses, and proportion of cases requiring additional work-up with intraarterial digital subtraction angiography owing to equivocal results of the new modality were determined. The base case evaluated was that of 60-year-old men with severe intermittent claudication and assumed an incremental cost-effectiveness threshold of 100,000 US dollars per QALY.

RESULTS

If treatment were limited to angioplasty, a new imaging modality would be cost-effective if the costs were 300 US dollars and the sensitivity was 85%, even if up to 35% of patients needed additional work-up. When both angioplasty and bypass surgery were considered as treatment options, a new imaging modality was cost-effective if the costs were 300 US dollars, the sensitivity was higher than 94%, and 20% of patients required additional work-up.

CONCLUSION

Multi-detector row CT angiography, as compared with currently used imaging modalities such as MR angiography, has the potential to be cost-effective in the evaluation of patients with intermittent claudication.

Gadobenate dimeglumine-enhanced MR angiography of the abdominal aorta and renal arteries

OBJECTIVE

This study was conducted to determine the efficacy and safety of four different doses of gadobenate dimeglumine for contrast-enhanced three-dimensional MR angiography of the abdominal aorta and renal arteries.

SUBJECTS AND METHODS

Ninety-four patients with suspected abnormality of the abdominal aorta or renal arteries underwent unenhanced three-dimensional gradient-recalled echo time-of-flight MR angiography and contrast-enhanced MR angiography after the IV injection of one of four doses of gadobenate dimeglumine (0.025, 0.05, 0.1, and 0.2 mmol/kg of body weight). Efficacy was assessed on-site and by two blinded off-site reviewers in terms of change in total diagnostic quality score and diagnostic quality score per vessel segment from baseline unenhanced time-of-flight MR angiography to contrast-enhanced MR angiography. Secondary efficacy end points included lesion count and level of confidence in lesion characterization. Safety assessments comprised adverse event monitoring, physical evaluation, vital signs, ECG, and laboratory investigations.

RESULTS

A significant change in the total diagnostic quality score from unenhanced to contrast-enhanced MR angiography was observed at all doses. The change increased with increased dose, plateauing at the 0.1 mmol/kg dose level. More patients with lesions detected and increased reviewer confidence for lesion characterization were noted on contrast-enhanced MR angiography compared with unenhanced MR angiography, although no dose-related trends were observed. All doses were well tolerated, and no significant changes in safety parameters were observed.

CONCLUSION

Gadobenate dimeglumine is an effective and safe agent for contrast-enhanced MR angiography of the abdominal aorta and renal arteries. A dose of 0.1 mmol/kg of body weight appears to be the most suitable.

Use of a blood-pool contrast agent for MR-guided vascular procedures: feasibility of ultrasmall superparamagnetic iron oxide particles

RATIONALE AND OBJECTIVES

The purpose of this study was to examine the dose dependency of the intravascular signal intensity after injection of ultrasmall superparamagnetic iron oxide (USPIO) particles (SH U 555 C) in a rabbit model studied with a low-field-strength magnetic resonance (MR) imaging system. The results were used to facilitate MR-guided vascular procedures in a pig.

MATERIALS AND METHODS

All experiments were performed at 0.2 T. To determine the optimum USPIO (or SH U 555 C) dose for intravascular interventions, the authors acquired coronal three-dimensional MR angiographic images in 12 rabbits after injection of four dose levels (10, 20, 30, and 40 micromol of iron per kilogram body weight). The intraaortic signal intensities were measured in user-defined regions of interest. For numerical analysis, signal intensity enhancement was computed. Subsequently MR image-guided procedures were performed in USPIO-enhanced vessels in one pig.

RESULTS

The signal intensity evaluation shows a clear-cut dose dependence in both early and late phases after administration of SH U 555 C. A high-spatial-resolution MR angiogram acquired 20 minutes after injection yielded the best results with the highest dose (40 micromol of iron per kilogram); at that dose, intravascular enhancement was sufficient for vascular procedures for 60 minutes after injection.

CONCLUSION

SH U 555 C is a promising contrast agent for MR angiography and MR-guided vascular procedures in an open low-field-strength MR imager.

Assessment of T1 and T2* effects in vivo and ex vivo using iron oxide nanoparticles in steady state--dependence on blood volume and water exchange

Accurate knowledge of the relationship between contrast agent concentration and tissue relaxation is a critical requirement for quantitative assessment of tissue perfusion using contrast-enhanced MRI. In the present study, using a pig model, the relationship between steady-state blood concentration levels of an iron oxide nanoparticle with a hydrated diameter of 12 nm (NC100150 Injection) and changes in the transverse and longitudinal relaxation rates (1/T2* and 1/T1, respectively) in blood, muscle, and renal cortex was investigated at 1.5 T. Ex vivo measurements of 1/T2* and 1/T1 were additionally performed in whole pig blood spiked with different concentrations of the iron oxide nanoparticle. In renal cortex and muscle, 1/T2* increased linearly with contrast agent concentration with slopes of 101 +/-22 s(-1)mM(-1) and 6.5 +/-0.9 s(-1)mM(-1) (mean +/- SD), respectively. In blood, 1/T2* increased as a quadratic function of contrast agent concentration, with different quadratic terms in the ex vivo vs. the in vivo experiments. In vivo, 1/T1 in blood increased linearly with contrast agent concentration, with a slope (T1-relaxivity) of 13.9 +/- 0.9 s(-1)mM(-1). The achievable increase in 1/T1 in renal cortex and muscle was limited by the rate of water exchange between the intra- and extravascular compartments and the 1/T1-curves were well described by a two-compartment water exchange limited relaxation model.

Pre-clinical results with Clariscan (NC100150 Injection); experience from different disease models

A superparamagnetic nanoparticle (NC100150 Injection) was investigated in two different animal models; renal perfusion in pigs and tumour imaging in mice. In the pig model, qualitative first-pass perfusion maps following a bolus injection of NC100150 Injection enabled good visualisation of hypoperfused regions of the renal cortex following partial ligation of the renal artery. High temporal resolution was found to be essential to accurately capture the first passage of the contrast agent through the kidney due to the very rapid blood flow in normal renal cortex. In the tumour model (LS174T cells implanted in nude mice), NC100150 Injection was found to cause a gradual (over 60 min) signal increase on T1-w images in part of the tumours which was attributed to contrast agent leakage from the vascular space to the extravascular space in areas of increased capillary permeability. This observation is consistent with previous reports on the molecular cut-off size for vascular extraction for this tumour cell line. The specific enhancement of tumour tissue suggest potential utility of NC100150 Injection as an angiogenesis marker.