Reducing Gadolinium Contrast With Artificial Intelligence

Gadolinium contrast is an important agent in magnetic resonance imaging (MRI), particularly in neuroimaging where it can help identify blood-brain barrier breakdown from an inflammatory, infectious, or neoplastic process. However, gadolinium contrast has several drawbacks, including nephrogenic systemic fibrosis, gadolinium deposition in the brain and bones, and allergic-like reactions. As computer hardware and technology continues to evolve, machine learning has become a possible solution for eliminating or reducing the dose of gadolinium contrast. This review summarizes the clinical uses of gadolinium contrast, the risks of gadolinium contrast, and state-of-the-art machine learning methods that have been applied to reduce or eliminate gadolinium contrast administration, as well as their current limitations, with a focus on neuroimaging applications. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 1.

Gadolinium-Based Contrast Agents in Pregnant Women: A Literature Review of MRI Safety

Gadolinium-based contrast agents (GBCAs) are commonly used in magnetic resonance imaging (MRI) to enhance the visualisation and characterisation of the region of interest/lesion. Internal structures are well seen with MRI with good spatial resolution. Although MRI is generally considered safe during pregnancy, concerns have been raised regarding the safety of GBCAs, particularly during the first trimester. Limited studies have been conducted to assess the safety of GBCAs in pregnant women, with conflicting results. A comprehensive literature search was conducted using PubMed, SpringerLink, Medscape, ResearchGate and Wiley Online Library. The search terms included various combinations of MRI, pregnancy, first trimester, gadolinium contrast agents, foetus, risk, and toxicity. The search criteria were articles published in English in the last 20 years and indexed in the MEDLINE or Embase databases. The majority of studies found no definitive evidence that GBCAs are harmful during pregnancy, particularly during the first trimester. Some studies reported no increased risk of adverse outcomes in infants exposed to GBCAs during the first trimester. However, other studies showed inconsistent results. Retrospective cohort studies provided some reassurance regarding the safety of GBCAs when indicated in pregnant women but did not address potential long-term adverse outcomes in infants exposed to GBCAs during gestation. The literature review also highlights the importance of further evaluating the subacute and chronic effects of GBCA exposure in infants. The safety of GBCAs during pregnancy, particularly during the first trimester, remains uncertain. More large-scale, long-term studies are needed to clarify the safety of GBCAs in pregnant women and their potential effects on foetal and neonatal outcomes. Until conclusive evidence is available, healthcare providers should carefully weigh the benefits and risks of using GBCAs during pregnancy and consider alternative imaging modalities, such as non-contrast MRI or ultrasound, when necessary.

Magnetic Targeting of Gadolinium Contrast to Enhance MRI of the Inner Ear in Endolymphatic Hydrops

OBJECTIVES

1. Determine the feasibility and efficiency of local magnetic targeting delivery of gadolinium (Gad) contrast to the inner ear in rodents. 2. Assess any potential ototoxicity of magnetic targeting delivery of Gad in the inner ear. 3. Study the utility of magnetic targeting delivery of Gad to visualize and quantify endolymphatic hydrops (EH) in a transgenic mouse model.

STUDY DESIGN

Controlled in vivo animal model study.

METHODS

Paramagnetic Gad was locally delivered to the inner ear using the magnetic targeting technique in both rat and mouse models. Efficiency of contrast delivery was assessed using magnetic resonance imaging (MRI). Ototoxicity of Gad was examined with histology of the cochlea and functional audiological tests. The Phex mouse model was used to study EH, hearing loss, and balance dysfunction. Magnetic targeting delivery of Gad contrast was used in the Phex mouse model to visualize the effects of EH using MRI.

RESULTS

Magnetic targeting improved the delivery of Gad to the inner ear and the technique was reproducible in both rat and mouse models. The delivery method did not result in microstructural damage or any significant hearing loss in a normal animal. Magnetic targeting of Gad in the Phex mouse model allowed detailed visualization and quantification of EH.

CONCLUSION

This study provided the first evidence of the effectiveness and efficiency of the local magnetic targeting delivery of gadolinium contrast to the inner ear and its application to the visualization and quantification of EH. Laryngoscope, 133:914-923, 2023.

Intracranial meningioma surveillance using volumetrics from T2-weighted MRI

BACKGROUND AND PURPOSE

The gold standard for imaging of meningiomas is MRI with gadolinium-based contrast agent. Due to increased costs, time, and uncertain chronic effects of gadolinium exposure, use of noncontrast T2-weighted imaging (T2WI) in lieu of contrast-enhanced MRI has been an increasing focus of research across various diagnostic scenarios. The purpose of this study was to evaluate the diagnostic accuracy of T2WI in detecting changes in meningioma tumor volume.

METHODS

Imaging and clinical data were reviewed for 82 consecutive patients undergoing MR-surveillance of intracranial meningioma. Using volumetric-T2WI, two neuroradiologists independently calculated tumor volumes. Measurements were compared to a baseline study contrast-enhanced T1 tumor volume. Using contrast-enhanced sequences as the reference standard, statistical analysis was performed to determine the accuracy of T2WI in detecting changes of meningioma volume.

RESULTS

Using only T2WI, readers detected meningioma volume change ≥ 20% in 19/82 patients and volume change <20% in 63/82 patients. Reader accuracy for detecting change in tumor volume on T2WI ≥ 20% was 0.85, sensitivity 0.65, specificity 0.93, positive predictive value (PPV) 0.79, and negative predictive value (NPV) 0.87. For meningiomas >1 ml, reader accuracy for detecting change in tumor volume on T2WI ≥20% was 0.90, sensitivity 0.78, specificity 0.95, PPV 0.88, and NPV 0.91. Change in tumor volume on T2WI ≥20% was detected with 100% accuracy for posterior fossa meningiomas. Inter-reader agreement for all meningiomas was moderate (κ = 0.45) improving to substantial agreement (κ = 0.77) with tumor volumes >1 ml.

CONCLUSION

Volumetric-T2WI detects changes in meningioma volume with comparable accuracy to gold standard T1 postcontrast imaging, particularly with higher tumor volumes and posterior fossa locations.

Benign or Malignant Characterization of Soft-Tissue Tumors by Using Semiquantitative and Quantitative Parameters of Dynamic Contrast-Enhanced Magnetic Resonance Imaging

PURPOSE

To evaluate the efficacy of the semiquantitative and quantitative parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in differentiating between benign and malignant soft-tissue tumors.

METHODS

A total of 45 patients with pathologically confirmed soft-tissue tumors (15 benign and 30 malignant tumors) underwent DCE-MRI. The semiquantitative parameters assessed were as follows: time to peak (TTP), maximum concentration (MAX Conc), area under the curve of time-concentration curve (AUC-TC), and maximum rise slope (MAX Slope). Quantitative DCE-MRI was analyzed with the extended Tofts-Kety model to assess the following quantitative parameters: volume transfer constant (Ktrans), microvascular permeability reflux constant (Kep), and distribute volume per unit tissue volume (Ve). Data were evaluated using the independent t test or Mann-Whitney U test and receiver operating characteristic (ROC) curves.

RESULTS

The TTP (P = .0035), MAX Conc (P = .0018), AUC-TC (P = .0018), MAX Slope (P = .0018), Ktrans (P = .0018), and Kep (P = .0035) were significantly different between the benign and malignant soft-tissue tumors. The AUC of the ROC curve demonstrated the diagnostic potential of TTP (0.778), MAX Conc (0.849), AUC-TC (0.831), MAX Slope (0.847), Ktrans (0.836), Kep (0.778), and Ve (0.638).

CONCLUSIONS

The use of semiquantitative and quantitative parameters of DCE-MRI enabled differentiation between benign and malignant soft-tissue tumors. The values of TTP were lower, while those of MAX Conc, AUC-TC, MAX Slope, Ktrans, and Kep were higher in malignant than in benign tumors.

Retrospective analysis of non-laboratory-based adverse drug reactions induced by intravenous radiocontrast agents in a Joint Commission International-accredited academic medical center hospital in China

The authors retrospectively analyzed the pattern and characteristics of non-laboratory-based adverse drug reactions (ADRs) induced by intravenous radiocontrast agents in a large-scale hospital in China during 2014-2015. There were 314 ADR cases among 118,208 patients receiving enhanced CT or MRI examinations. The frequency of moderate/severe ADRs defined by Chinese Society of Radiology (ie, severe vomiting, systematic urticaria, facial swelling, dyspnea, vasovagal reaction, laryngeal edema, seizure, trembling, convulsions, unconsciousness, shock, death, and other unexpected adverse reactions) was rare (0.0431%), whereas the mild ADRs were uncommon (0.2225%) and accounted for 83.76% of ADRs. Frequency of ADRs induced by iodinated contrast agents was related with examination site, sex, and type of patient settings (P<0.01) and was higher compared with gadolinium contrast agents (0.3676% vs 0.0504%, P<0.01). From 2014 to 2015, frequencies of total and moderate/severe ADRs induced by iodinated contrast agents decreased significantly (0.4410% vs 0.2947%, P<0.01; 0.0960% vs 0.0282%, P<0.01, respectively). Frequency of ADRs differed among different iodinated contrast and gadolinium contrast (P<0.05) agents. Iopromide's ADR frequency in 2014 was significantly higher compared with iopamidol, ioversol, or iohexol (P<0.01). Frequency of moderate/severe ADRs induced by iodixanol was 4.1-5.4 times that of iohexol, iopromide, or iopamidol. Rash was the predominant ADR subtype (84.39%) and occurred more frequently with iodixanol compared with iohexol, iopamidol, or ioversol (P<0.01). Overall, 21.97% of ADR cases had allergy history or atopy traits, and these cases experienced ADRs earlier than the negative ones (17.19 min vs 85.34 min, P<0.01). The mean time to onset of ADRs was increased in patients receiving iodixanol compared with other iodinated contrast agents (323.77 min vs 42.36 min, P<0.01). Overall, 37.26% of ADRs occurred within 5 min and 84.08% of ADRs occurred within 30 min. Efficient quality improvement in decreasing ADRs induced by radiocontrast agents has been achieved by multidisciplinary collaboration.

Cardiovascular magnetic resonance imaging in hypertrophic cardiomyopathy: Current state of the art

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy with a prevalence of 1:500 (0.2%) in the general population. Sudden cardiac death (SCD) is the most feared presentation of HCM. Therefore, it is essential to identify individuals at high risk in order to prevent SCD. The absence of conventional risk factors does not nullify the risk of HCM related SCD. Although echocardiography is currently the most widely used imaging modality, cardiac magnetic resonance (CMR) allows detailed characterization of the HCM phenotype, which makes it possible to differentiate HCM from other causes of left ventricular hypertrophy. CMR has the potential to further refine risk stratification. Late gadolinium enhancement (LGE) on CMR is a high-risk feature and there is emerging data to suggest that the presence of LGE should be employed as a marker for major adverse outcomes such as SCD, arrhythmias, systolic and diastolic heart failure. Hence, LGE on CMR may be considered an additional risk factor for SCD in HCM patients and should be incorporated in decision-making for implant-able cardioverter defibrillator implantation to aid primary prevention. Novel markers such as the extent of myocardial fibrosis on CMR must be accounted for comprehensive risk stratifica-tion of HCM patients. The purpose of this review is to discuss the current status and emerging role of CMR in HCM.

Hyperintensity in the Dentate Nucleus on Nonenhanced T1-Weighted Magnetic Resonance Imaging Suggests Dechelation of Contrast Agents

With the exception of renal failure patients, gadolinium-based contrast agents (GBCAs) for magnetic resonance imaging (MRI) have a high tolerance and acceptability in patients needing to undergo an enhanced MRI. Now that enhanced MRIs are becoming increasingly popular and nephrogenic systemic fibrosis cases are becoming a rarity, a common belief is that these GBCAs are essentially "biologically inert" materials. However, recent reports have emerged querying the link between these GBCAs and hyperintensity in the dentate nucleus on unenhanced T1-weighted MRI in some patients. This review article outlines the basic chemistry and characteristics of currently approved GBCAs, summarizes the described research findings of gadolinium deposition in the dentate nucleus, and identifies areas for future research.

Effect of intravenous gadolinium-DTPA on diffusion-weighted imaging of brain tumors: a short temporal interval assessment

PURPOSE

To determine the effect of intravenous administration of gadolinium (Gd) contrast medium (Gd-DTPA) on diffusion-weighted imaging (DWI) for the evaluation of normal brain parenchyma vs. brain tumor following a short temporal interval.

MATERIALS AND METHODS

Forty-four DWI studies using b values of 0 and 1000 s/mm(2) were performed before, immediately after, 1 min after, 3 min after, and 5 min after the administration of Gd-DTPA on 62 separate lesions including 15 meningioma, 17 glioma and 30 metastatic lesions. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and apparent diffusion coefficient (ADC) values of the brain tumor lesions and normal brain tissues were measured on pre- and postcontrast images. Statistical analysis using paired t-test between precontrast and postcontrast data were obtained on three brain tumors and normal brain tissue.

RESULTS

The SNR and CNR of brain tumors and the SNR of normal brain tissue showed no statistical differences between pre- and postcontrast (P > 0.05). The ADC values on the three cases of brain tumors demonstrated significant initial increase on the immediate time point (P < 0.01) and decrease on following the 1 min time point (P < 0.01) after contrast. Significant decrease of ADC value was still found at 3min and 5min time point in the meningioma group (P < 0.01) with gradual normalization over time. The ADC values of normal brain tissues demonstrated significant initial elevation on the immediately postcontrast DWI sequence (P < 0.01).

CONCLUSION

Contrast medium can cause a slight but statistically significant change on the ADC value within a short temporal interval after the contrast administration. The effect is both time and lesion-type dependent.

Nephrogenic systemic fibrosis: current concepts

Nephrogenic systemic fibrosis (NSF) was first described in 2000 as a scleromyxedema-like illness in patients on chronic hemodialysis. The relationship between NSF and gadolinium contrast during magnetic resonance imaging was postulated in 2006, and subsequently, virtually all published cases of NSF have had documented prior exposure to gadolinium-containing contrast agents. NSF has been reported in patients from a variety of ethnic backgrounds from America, Europe, Asia and Australia. Skin lesions may evolve into poorly demarcated thickened plaques that range from erythematous to hyperpigmented. With time, the skin becomes markedly indurated and tethered to the underlying fascia. Extracutaneous manifestations also occur. The diagnosis of NSF is based on the presence of characteristic clinical features in the setting of chronic kidney disease, and substantiated by skin histology. Differential diagnosis is with scleroderma, scleredema, scleromyxedema, graft-versus-host disease, etc. NSF has a relentlessly progressive course. While there is no consistently successful treatment for NSF, improving renal function seems to slow or arrest the progression of this condition. Because essentially all cases of NSF have developed following exposure to a gadolinium-containing contrast agent, prevention of this devastating condition involves the careful avoidance of administering these agents to individuals at risk.