Nephrogenic systemic fibrosis and gadolinium: a perfect storm

Is perfect the enemy of good? Weighing the evidence for biparametric MRI in prostate cancer

The role of multiparametric MRI in diagnosis, staging and treatment planning for prostate cancer is well established. However, there remain several challenges to widespread adoption. One such challenge is the duration and cost of the examination. Abbreviated exams omitting contrast-enhanced sequences may help address this challenge. In this review, we will discuss the rationale for biparametric MRI for detection and characterization of clinically significant prostate cancer prior to biopsy and synthesize the published literature. We will weigh up the advantages and disadvantages to this approach and lay out a conceptual cost/benefit analysis regarding adoption of biparametric MRI.

Gadolinium Neutron Capture Therapy (GdNCT) Agents from Molecular to Nano: Current Status and Perspectives

157Gd (natural abundance = 15.7%) has the highest thermal neutron capture cross section (σ) of 254,000 barns (1 barn = 10-28 m2) among stable (nonradioactive) isotopes in the periodic table. Another stable isotope, 155Gd (natural abundance = 14.8%), also has a high σ value of 60,700 barns. These σ values are higher than that of 10B (3840 barns, natural abundance = 19.9%), which is currently used as a neutron-absorbing isotope for boron neutron capture therapy agents. Energetic particles such as electrons and γ-rays emitted from Gd-isotopes after neutron beam absorption kill cancer cells by damaging DNAs inside cancer-cell nuclei without damaging normal cells if Gd-chemicals are positioned in cancer cells. To date, various Gd-chemicals such as commercial Gd-chelates used as magnetic resonance imaging contrast agents, modified Gd-chelates, nanocomposites containing Gd-chelates, fullerenes containing Gd, and solid-state Gd-nanoparticles have been investigated as gadolinium neutron capture therapy (GdNCT) agents. All GdNCT agents had exhibited cancer-cell killing effects, and the degree of the effects depended on the GdNCT agents used. This confirms that GdNCT is a promising cancer therapeutic technique. However, the commercial Gd-chelates were observed to be inadequate in clinical use because of their low accumulation in cancer cells due to their extracellular and noncancer targeting properties and rapid excretion. The other GdNCT agents exhibited higher accumulation in cancer cells, compared to Gd-chelates; consequently, they demonstrated higher cancer-cell killing effects. However, they still displayed limitations such as poor specificity to cancer cells. Therefore, continuous efforts should be made to synthesize GdNCT agents suitable in clinical applications. Herein, the principle of GdNCT, current status of GdNCT agents, and general design strategy for GdNCT agents in clinical use are discussed and reviewed.

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

Toxicity Evaluation of a Novel Magnetic Resonance Imaging Marker, CoCl2-N-Acetylcysteine, in Rats

C4 (cobalt dichloride-N-acetylcysteine [1% CoCl₂:2% NAC]) is a novel magnetic resonance imaging contrast marker that facilitates visualization of implanted radioactive seeds in cancer brachytherapy. We evaluated the toxicity of C4. Rats were assigned to control (0% CoCl₂:NAC), low-dose (0.1% CoCl₂:2% NAC), reference-dose (C4), and high-dose (10% CoCl₂:2% NAC) groups. Agent was injected into the left quadriceps femoris muscle of the rats. Endpoints were organ and body weights, hematology, and serum chemistry and histopathologic changes of tissues at 48 hours and 28 and 63 days after dosing. Student's t tests were used. No abnormalities in clinical signs, terminal body and organ weights, or hematologic and serum chemistry were noted, and no gross or histopathologic lesions of systemic tissue toxicity were found in any treatment group at any time point studied. At the site of injection, concentration-dependent acute responses were observed in all treatment groups at 48 hours after dosing and were recovered by 28 days. No myofiber degeneration or necrosis was observed at 28 or 63 days in any group. In conclusion, a single intramuscular dose of C4 produced no acute or chronic systemic toxicity or inflammation in rats, suggesting that C4 may be toxicologically safe for clinical use in cancer brachytherapy.

Gadolinium deposition and the potential for toxicological sequelae - A literature review of issues surrounding gadolinium-based contrast agents

Every year, approximately 30 million magnetic resonance imaging scans are enhanced with gadolinium-based contrast agents (GBCAs) worldwide. Although the development of nephrogenic systemic fibrosis in patients with renal impairment is well-documented, over recent years it has become apparent that exposure to GBCAs can potentially result in gadolinium deposition within human bone and brain tissue even in the presence of normal renal function. This review will address some of the controversies surrounding the safety of GBCA administration based on evidence from in vivo experiments, animal studies and clinical studies. We additionally evaluate the potential risk of toxicity from exposure to gadolinium in light of new guidance published by the US Food and Drug Administration and the European Medicines Agency, and discuss whether gadolinium deposition disease exists as a new diagnosis.

Neuroradiological evaluation of demyelinating disease

Central nervous system inflammatory demyelinating disease can affect patients across the life span. Consensus definitions and criteria of all of the different acquired demyelinating diseases that fall on this spectrum have magnetic resonance imaging criteria. The advances of both neuroimaging techniques and important discoveries in immunology have produced an improved understanding of these conditions and classification. Neuroimaging plays a central role in the accurate diagnosis, prognosis, disease monitoring and research efforts that are being undertaken in this disease. This review focuses on the imaging spectrum of acquired demyelinating disease.

Introductory Chemistry: A Molar Relaxivity Experiment in the High School Classroom

Dotarem and Magnevist, two clinically available magnetic resonance imaging (MRI) contrast agents, were assessed in a high school science classroom with respect to which is the better contrast agent. Magnevist, the more efficacious contrast agent, has negative side effects because its gadolinium center can escape from its ligand. However, Dotarem, though a less efficacious contrast agent, is a safer drug choice. After the experiment, students are confronted with the FDA warning on Magnevist, which enabled a discussion of drug efficacy versus safety. We describe a laboratory experiment in which NMR spin lattice relaxation rate measurements are used to quantify the relaxivities of the active ingredients of Dotarem and Magnevist. The spin lattice relaxation rate gives the average amount of time it takes the excited nucleus to relax back to the original state. Students learn by constructing molar relaxivity curves based on inversion recovery data sets that Magnevist is more relaxive than Dotarem. This experiment is suitable for any analytical chemistry laboratory with access to NMR.

Safety of older generations of gadolinium in mild-to-moderate renal failure

Nephrogenic systemic fibrosis (NSF) is a rare disease that is mostly reported in patients with chronic kidney disease (CKD) who have received gadolinium as a contrast in imaging techniques. The exact pathogenetic role of renal failure or gadolinium is not known. The aim of this study is to show whether mild-to-moderate renal failure is a risk for NSF as it is described in severe renal failure. In this cross-sectional study, we enrolled 164 patients with serum creatinine levels >1.5 mg/dL who were in different stages of CKD and had received gadolinium (gadopentetate). The average lag time between the gadolinium administration and the study was 4 months. The most prevalent skin symptom was itching (19%) and the least frequent was induration and papules (<1%). At the follow-up, all skin lesions were relieved. No patients had characteristic lesions of NSF. Twenty-five percent of patients had acute kidney injury at the time of gadolinium exposure. No patients had liver disease and only five were receiving erythropoietin. None of our patients were taking immunosuppressive agents, but all of them suffered from cardiovascular diseases. We conclude that in patients with mild-to-moderate renal failure, it seems that gadolinium is associated with no or very low risk for NSF. We did not find any NSF in patients with severe renal failure. However, because of the rarity of NSF, the low number of such patients in the study, and the high mortality, the use of gadolinium in these patients should be avoided.

Vascular abnormalities correlate with decreased soft tissue volumes in idiopathic clubfoot

BACKGROUND

Lower extremity vascular anomalies have been described for patients with clubfoot but few imaging studies have investigated effects on soft tissues such as fat and muscle. To make these assessments we need noninvasive, noncontrast agents to more safely image children.

QUESTIONS/PURPOSES

We describe a novel noninvasive imaging protocol to identify vascular and soft tissue abnormalities in the lower limbs of patients with clubfoot and determine whether these abnormalities are present in patients who had recurrent clubfoot.

PATIENTS AND METHODS

Three-dimensional noncontrast-enhanced MR angiography was used to identify vascular, bone, and soft tissue abnormalities in patients with clubfoot. We determined whether these abnormalities were more common in patients who had experienced recurrent clubfoot.

RESULTS

Four patients with isolated unilateral clubfoot had arterial anomalies in the clubfoot limb. All patients had less muscle volume in the affected limb, and nine of 11 patients (82%) had less subcutaneous fat, with a mean difference of 0.56 cm(3) ± 0.36 cm(3) (range, 0.08-1.12 cm(3)). Vascular anomalies and decreased fat and muscle volumes were present in all three patients with recurrent clubfoot.

CONCLUSIONS

We found a high frequency of vascular and soft tissue anomalies in the affected limbs of patients with unilateral clubfoot that may correlate with response to treatment.

Longitudinal evaluation of cartilage repair tissue after microfracture using T2-mapping: a case report with arthroscopic and MRI correlation

A man sustained a left knee injury which led to full-thickness chondral defects of the trochlear groove and lateral femoral condyle. Both areas were treated with microfractures and evaluated at 5 months and 2 years with standard MRI scans, T2 relaxation maps, and arthroscopy. At 5-months post-microfracture repair, the patient complained of recurrent anterior knee pain. While standard MRI imaging was inconclusive with regards to a potential recurrent defect at the trochlear groove microfracture area, T2 relaxation maps established the integrity of the surface layer which was confirmed by arthroscopic evaluation. At 2 years, imaging studies revealed repair tissue loss with low T2 values at the trochlear repair site. The failure of the trochlear site and the integrity of the lateral femoral condyle repair sites were confirmed by arthroscopy. This case report is the first one to provide a correlation of T2 mapping MRI findings with arthroscopic confirmation in the context of microfracture repairs. The study provides evidence for the clinical utility of T2 relaxation maps for the postoperative assessment of microfractures and raises the potential for T2 mapping MRI as a tool to evaluate these repair procedures.

Advanced kidney disease, gadolinium and nephrogenic systemic fibrosis: the perfect storm

PURPOSE OF REVIEW

Studies of a rare systemic fibrosing condition-entitled nephrogenic systemic fibrosis (NSF) are linked to gadolinium-based contrast (GBC) agent exposure in patients with advanced kidney disease. However, many patients with kidney disease are exposed to GBC agents, yet they do not develop this devastating disorder.

RECENT FINDINGS

NSF appears more likely to develop when the combination of advanced kidney disease, linear GBC agent exposure, and the presence of unique patient features converge. Linear GBC agents are more likely to promote NSF, probably due to chelate-Gd binding instability +/- underlying proinflammatory effects. Patients with advanced acute or chronic kidney disease (CKD) are at highest risk, in contrast to those with lower stages of CKD (stages I-III). Finally, whereas exposure to GBC agents in patients with advanced kidney disease is required for NSF to develop, it does not appear sufficient. Additional patient-specific co-factors, such as metabolic disorders, vascular injury, and inflammation, may also be necessary for NSF to occur.

SUMMARY

NSF develops when 'the perfect storm' of factors is present: unstable/pro-inflammatory GBC agent exposure, advanced kidney disease, and unique patient factors. Recognizing this combination of factors will hopefully allow this devastating condition to become of historical interest only.

Nephrogenic systemic fibrosis and management of high-risk patients

The purpose of this work is to provide current information on the rapidly evolving subject of nephrogenic systemic fibrosis (NSF), to establish the radiologic approach to the management of high-risk patients for NSF, and to assess the probabilistic risk of NSF compared to contrast induced nephropathy (CIN), as encountered with iodinated contrast media used in computed tomographic (CT) imaging. NSF is a disease process of considerable concern following gadolinium-containing contrast agents (GCCA) exposure in patients with diminished renal function. To minimize the possibility of NSF development in high-risk patients, GGCAs should not be used when they are not necessary, or the GCCAs, that have not at present been associated with NSF development, should be used at the lowest possible diagnostic dose, when they are necessary. Contrast-induced nephropathy is also a great risk in this patient population following the adminstration of iodinated contrast media (CM). In patients with diminished renal function who are not on regular dialysis, the risk of CIN following the administration of iodinated CM is higher than the risk of NSF following the administration of the most stable GCCAs. Risk benefit analysis should be performed prior to the administration of all CM, and the best combination of safety and diagnostic accuracy should be sought. Concern of NSF or CIN should not prevent the use of contrast agents in magnetic resonance imaging or computed tomography when they are deemed essential.