Manganese-Based Oral Contrast Agent for Liver Magnetic Resonance Imaging: Evaluation of the Time Course and Dose Response of Liver Signal Intensity Enhancement

Lesion Visualization of an Oral Manganese Contrast Agent Compared to Unenhanced MRI and Gadobenate Dimeglumine in Patients Undergoing Liver Magnetic Resonance Imaging for Evaluation of Colorectal Cancer Metastases: Centralized Assessment of a Randomized, Crossover, Phase II Study

OBJECTIVES

The primary objective of this study was to evaluate the visualization capability of orally administered manganese chloride tetrahydrate (ACE-MBCA [Ascelia Pharma-manganese-based contrast agent, also referred to as Orviglance or CMC-001]), a novel liver-specific contrast agent developed by Ascelia Pharma, as a liver-specific MRI contrast agent compared with that of the unenhanced MRI for focal liver lesions in a properly blinded study design. The secondary objective was to compare the performance of ACE-MBCA with gadobenate dimeglumine.

MATERIALS AND METHODS

Three independent readers analyzed MRI examinations from a previously completed randomized crossover clinical trial in a blinded manner in a centralized setting. The study included 20 consecutive adult patients with known or suspected liver metastases, who received both ACE-MBCA and gadobenate dimeglumine. The readers evaluated 6 types of MRI scans (unenhanced, enhanced, and combined MRI for both contrast agents) with lesion visualization [lesion border delineation (LBD) and lesion contrast (LC)] as primary outcome. To maintain the blinded nature of the study, all statistical analyses were performed by an independent statistician who was not involved in the image reading process. Differences in primary outcomes were performed using 1-sided paired t tests at a significance level of 0.025 for both parameters. For secondary outcomes (ACE-MBCA enhanced MRI visualization, lesion detection, size measurements, reader confidence, quantitative parameters, and image quality were compared with that of the other scans), descriptive statistics and 95% confidence intervals were used to evaluate differences between categories in comparative analyses, without formal hypothesis testing for most secondary endpoints.

RESULTS

ACE-MBCA-enhanced MRI demonstrated statistically significant superior scoring over unenhanced MRI for visualizing focal liver lesions, with mean LBD scores improving from 1.8-2.3 to 2.4-2.9 and LC scores ranging from 1.8-2.3 to 2.8-3.3 across all 3 readers (P < 0.001). Compared with unenhanced MRI, ACE-MBCA detected significantly more lesions across all readers (mean differences 0.4-0.8 lesions, 95% CI: 0.04-1.52), particularly for small lesions (<1 cm), where detection improved from 2-6 to 3-12 lesions. Liver-to-lesion contrast and contrast-to-noise ratios were also significantly higher after ACE-MBCA enhancement. All visualization parameters of ACE-MBCA were comparable to those of gadobenate dimeglumine, with no significant differences.

CONCLUSIONS

Compared with unenhanced MRI, ACE-MBCA MRI resulted in superior visualization and a greater number of detected liver lesions. ACE-MBCA and gadobenate dimeglumine performed similarly in the visualization and detection of colorectal liver metastases.

Manganese-derived biomaterials for tumor diagnosis and therapy

Manganese (Mn) is widely recognized owing to its low cost, non-toxic nature, and versatile oxidation states, leading to the emergence of various Mn-based nanomaterials with applications across diverse fields, particularly in tumor diagnosis and therapy. Systematic reviews specifically addressing the tumor diagnosis and therapy aspects of Mn-derived biomaterials are lacking. This review comprehensively explores the physicochemical characteristics and synthesis methods of Mn-derived biomaterials, emphasizing their role in tumor diagnostics, including magnetic resonance imaging, photoacoustic and photothermal imaging, ultrasound imaging, multimodal imaging, and biodetection. Moreover, the advantages of Mn-based materials in tumor treatment applications are discussed, including drug delivery, tumor microenvironment regulation, synergistic photothermal, photodynamic, and chemodynamic therapies, tumor immunotherapy, and imaging-guided therapy. The review concludes by providing insights into the current landscape and future directions for Mn-driven advancements in the field, serving as a comprehensive resource for researchers and clinicians.

Oral Manganese Chloride Tetrahydrate: A Novel Magnetic Resonance Liver Imaging Agent for Patients With Renal Impairment: Efficacy, Safety, and Clinical Implication

ABSTRACT

Manganese-based contrast agents (MBCAs) show promise to complement gadolinium-based contrast agents (GBCAs) in magnetic resonance imaging (MRI) of the liver. Management of patients with focal liver lesions and severely impaired renal function uses unenhanced liver MRI or GBCA-enhanced MRI. However, unenhanced MRI risks reducing patient's survival.Gadolinium-based contrast agents, which help to detect and visualize liver lesions, are associated with increased risk of nephrogenic systemic fibrosis in renally impaired patients, a severe adverse event (AE) with potentially fatal outcome. Therefore, use of GBCA in patients with impaired renal function requires careful consideration. Other concerns are related to tissue deposition in the brain and other organs due to lack of gadolinium clearance, which could lead to concerns also for other patient populations, for example, those exposed to multiple procedures with GBCA. Of particular concern are the linear chelates that remain available for liver MRI, where there is no replacement technology. This has highlighted the urgency for safer alternatives.An alternative may be the drug candidate Ascelia-MBCA (ACE-MBCA, Orviglance), oral manganese chloride tetrahydrate. This candidate effectively visualizes and detects focal liver lesions, as demonstrated in 8 clinical studies on 201 adults (healthy or with known or suspected focal liver lesions). ACE-MBCA has a low and transient systemic exposure, which is likely the reason for its beneficial safety profile. The AEs were primarily mild and transient, and related to the gastrointestinal tract. This new, orally administered product may offer a simple imaging approach, allowing appropriate patient management in renally impaired patients when use of GBCA requires careful consideration.In this review, we highlight the clinical development of ACE-MBCA-a novel, liver-specific contrast agent. We begin with a brief overview of manganese properties, addressing the need for MBCAs and describing their optimal properties. We then review key findings on the novel agent and how this allows high-quality MRIs that are comparable to GBCA and superior to unenhanced MRI. Lastly, we provide our view of future perspectives that could advance the field of liver imaging, addressing the medical needs of patients with focal liver lesions and severe renal impairment.Our review suggests that ACE-MBCA is a promising, effective, and well-tolerated new tool in the radiologist's toolbox.

Quantitative Ultrasound for Evaluation of Tumour Response to Ultrasound-Microbubbles and Hyperthermia

Objectives: Prior study has demonstrated the implementation of quantitative ultrasound (QUS) for determining the therapy response in breast tumour patients. Several QUS parameters quantified from the tumour region showed a significant correlation with the patient's clinical and pathological response. In this study, we aim to identify if there exists such a link between QUS parameters and changes in tumour morphology due to combined ultrasound-stimulated microbubbles (USMB) and hyperthermia (HT) using the breast xenograft model (MDA-MB-231). Method: Tumours grown in the hind leg of severe combined immuno-deficient mice were treated with permutations of USMB and HT. Ultrasound radiofrequency data were collected using a 25 MHz array transducer, from breast tumour-bearing mice prior and post-24-hour treatment. Result: Our result demonstrated an increase in the QUS parameters the mid-band fit and spectral 0-MHz intercept with an increase in HT duration combined with USMB which was found to be reflective of tissue structural changes and cell death detected using haematoxylin and eosin and terminal deoxynucleotidyl transferase dUTP nick end labelling stain. A significant decrease in QUS spectral parameters was observed at an HT duration of 60 minutes, which is possibly due to loss of nuclei by the majority of cells as confirmed using histology analysis. Morphological alterations within the tumour might have contributed to the decrease in backscatter parameters. Conclusion: The work here uses the QUS technique to assess the efficacy of cancer therapy and demonstrates that the changes in ultrasound backscatters mirrored changes in tissue morphology.

Dietary Manganese Exposure in the Adult Population in Germany-What Does it Mean in Relation to Health Risks?

Manganese is both an essential nutrient and a potential neurotoxicant. Therefore, the question arises whether the dietary manganese intake in the German population is on the low or high side. Results from a pilot total diet study in Germany presented here reveal that the average dietary manganese intake in the general population in Germany aged 14-80 years is about 2.8 mg day^-1 for a person of 70 kg body weight. This exposure level is within the intake range of 2-5 mg per person and day as recommended by the societies for nutrition in Germany, Austria, and Switzerland. No information on the dietary exposure of children in Germany can be provided so far. Although reliable information on health effects related to oral manganese exposure is limited, there is no indication from the literature that these dietary intake levels are associated with adverse health effects either by manganese deficiency or excess. However, there is limited evidence that manganese taken up as a highly bioavailable bolus, for example, uptake via drinking water or food supplements, could pose a potential risk to human health-particularly in certain subpopulations-when certain intake amounts, which are currently not well defined, are exceeded.

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.

Uptake and retention of manganese contrast agents for PET and MRI in the rodent brain

Manganese-enhanced magnetic resonance imaging (MRI) is an established neuroimaging method for signal enhancement, tract tracing, and functional studies in rodents. Along with the increasing availability of combined positron emission tomography (PET) and MRI scanners, the recent development of the positron-emitting isotope ⁵² Mn has prompted interest in the use of Mn²⁺ as a dual-modality contrast agent. In this work, we characterized and compared the uptake of systemically delivered Mn²⁺ and radioactive ⁵² Mn²⁺ in the rat brain for MRI and PET, respectively. Additionally, we examined the biodistribution of two formulations of ⁵² Mn²⁺ in the rat. In MRI, maximum uptake was observed one day following delivery of the highest MnCl₂ dose tested (60 mg/kg), with some brain regions showing delayed maximum enhancement 2-4 days following delivery. In PET, we observed low brain uptake after systemic delivery, with a maximum of approximately 0.2% ID/g. We also studied the effect of final formulation vehicle (saline compared with MnCl₂ ) on ⁵² Mn²⁺ organ biodistribution and brain uptake. We observed that the addition of bulk Mn²⁺ carrier to ⁵² Mn²⁺ in solution resulted in significantly reduced ⁵² Mn²⁺ uptake in the majority of organs, including the brain. These results lay the groundwork for further development of ⁵² Mn PET or dual Mn-enhanced PET-MR neuroimaging in rodents, and indicate several interesting potential applications of ⁵² Mn PET in other organs and systems. Copyright © 2016 John Wiley & Sons, Ltd.

Laser ablation inductively coupled plasma mass spectrometry imaging of metals in experimental and clinical Wilson's disease

Wilson's disease is an autosomal recessive disorder in which the liver does not properly release copper into bile, resulting in prominent copper accumulation in various tissues. Affected patients suffer from hepatic disorders and severe neurological defects. Experimental studies in mutant mice in which the copper-transporting ATPase gene (Atp7b) is disrupted revealed a drastic, time-dependent accumulation of hepatic copper that is accompanied by formation of regenerative nodes resembling cirrhosis. Therefore, these mice represent an excellent exploratory model for Wilson's disease. However, the precise time course in hepatic copper accumulation and its impact on other trace metals within the liver is yet poorly understood. We have recently established novel laser ablation inductively coupled plasma mass spectrometry protocols allowing quantitative metal imaging in human and murine liver tissue with high sensitivity, spatial resolution, specificity and quantification ability. By use of these techniques, we here aimed to comparatively analyse hepatic metal content in wild-type and Atp7b deficient mice during ageing. We demonstrate that the age-dependent accumulation of hepatic copper is strictly associated with a simultaneous increase in iron and zinc, while the intrahepatic concentration and distribution of other metals or metalloids is not affected. The same findings were obtained in well-defined human liver samples that were obtained from patients suffering from Wilson's disease. We conclude that in Wilson's disease the imbalances of hepatic copper during ageing are closely correlated with alterations in intrahepatic iron and zinc content.

MR signal changes on hepatobiliary imaging after oral ingestion of manganese chloride tetrahydrate: preliminary examination

PURPOSE

To clarify magnetic resonance (MR) signal changes during hepatobiliary imaging after oral ingestion of manganese chloride tetrahydrate (Bothdel Oral Solution 10) (MCT).

MATERIALS AND METHODS

Subjects were an MCT phantom, 10 healthy volunteers and 155 consecutive patients. The phantom study evaluated the relationship between MCT concentration and MR signal intensity. The volunteer study qualitatively and quantitatively analyzed the time course of hepatobiliary imaging immediately and 30, 60, 120 and 180 min after oral ingestion of MCT. The clinical study analyzed the incidence and factors affecting signal changes on additional MRCP with MCT as a final scan during routine clinical MRCP.

RESULTS

In the phantom study, a significant and excellent positive linear correlation was found between MCT concentration and R2* measurement (r(2) = 0.996, p < 0.01). In the volunteer study, biliary imaging and hepatic R2* values changed significantly after oral ingestion of MCT (p < 0.05). In the clinical study, a signal drop on MRCP with MCT was visually confirmed in 14.8 % of cases. Multivariate logistic regression found no factors significantly affecting signal drop.

CONCLUSION

We recommend performing MRCP early after oral ingestion of MCT, because signal changes occur even during routine MRCP.

A new manganese-based oral contrast agent (CMC-001) for liver MRI: pharmacological and pharmaceutical aspects

Manganese is one of the most abundant metals on earth and is found as a component of more than 100 different minerals. Besides being an essential trace element in relation to the metabolic processes in the body, manganese is also a paramagnetic metal that possesses similar characteristics to gadolinium with regards to T1-weighted (T1-w) magnetic resonance imaging (MRI). Manganese, in the form of manganese (II) chloride tetrahydrate, is the active substance in a new targeted oral contrast agent, currently known as CMC-001, indicated for hepatobiliary MRI. Under physiological circumstances manganese is poorly absorbed from the intestine after oral intake, but by the use of specific absorption promoters, L-alanine and vitamin D(3), it is possible to obtain a sufficiently high concentration in the liver in order to achieve a significant signal enhancing effect. In the liver manganese is exposed to a very high first-pass effect, up to 98%, which prevents the metal from reaching the systemic circulation, thereby reducing the number of systemic side-effects. Manganese is one of the least toxic trace elements, and due to its favorable safety profile it may be an attractive alternative to gadolinium-based contrast agents for patients undergoing an MRI evaluation for liver metastases in the future. In this review the basic pharmacological and pharmaceutical aspects of this new targeted oral hepatobiliary specific contrast agent will be discussed.

MRI of colorectal cancer liver metastases: comparison of orally administered manganese with intravenously administered gadobenate dimeglumine

OBJECTIVES

To compare the sensitivity of MRI to detect colorectal cancer liver metastases (CRLM) after ingestion of manganese-based contrast agent (CMC-001) with that of a comprehensive intravenous gadobenate dimeglumine protocol, and to assess the safety and acceptability of oral manganese.

METHODS

20 patients suspected of having 1-6 CRLM were included prospectively in this randomised cross-over study. Liver MRI was performed with a one-week interval at 1.5 T and included T1-w VIBE and T2-HASTE, before and after administration of 1.6 g CMC-001 or 0.1 mmol/kg gadobenate dimeglumine. The metastasis-to-liver signal intensity (SI) ratio was calculated. Standard of reference was histopathology after surgery, or combination of other imaging studies and/or follow up. Adverse events (AE) and clinicolaboratory tests were monitored.

RESULTS

Of 44 metastases, 41 were detected after CMC-001 (93%) and 42 after gadobenate dimeglumine (95%). Fifteen false-positive lesions were found after CMC-001 and 2 after gadobenate dimeglumine. The metastasis-to-liver SI ratio was significantly higher after CMC-001 than after gadobenate dimeglumine (0.51 and 0.21 respectively, P < 0.0001). More AE occurred after manganese compared to gadobenate dimeglumine.

CONCLUSIONS

CMC-001 is as sensitive as an extensive intravenous gadobenate dimeglumine protocol in detecting CRLM. It was relatively well tolerated but had higher rates of gastrointestinal AE.

KEY POINTS

• Liver MRI after ingestion of manganese is highly sensitive for detecting metastases • High false-positive rate necessitates further evaluation, in some cases • The MR examination time is short • Oral ingestion of manganese seems safe and relatively well tolerated by patients • Manganese compounds may be useful for liver metastasis surveillance after colorectal cancer.

Assessment and monitoring tumor vascularity with contrast-enhanced ultrasound maximum intensity persistence imaging

OBJECTIVES

Contrast-enhanced ultrasound imaging is increasingly being used in the clinic for assessment of tissue vascularity. The purpose of our study was to evaluate the effect of different contrast administration parameters on the in vivo ultrasound imaging signal in tumor-bearing mice using a maximum intensity persistence (MIP) algorithm and to evaluate the reliability of in vivo MIP imaging in assessing tumor vascularity. The potential of in vivo MIP imaging for monitoring tumor vascularity during antiangiogenic cancer treatment was further evaluated.

MATERIALS AND METHODS

In intraindividual experiments, varying contrast microbubble concentrations (5 × 10⁵, 5 × 10⁶, 5 × 10⁷, 5 × 10⁸ microbubbles in 100 μL saline) and contrast injection rates (0.6, 1.2, and 2.4 mL/min) in subcutaneous tumor-bearing mice were applied and their effects on in vivo contrast-enhanced ultrasound MIP imaging plateau values were obtained using a dedicated small animal ultrasound imaging system (40 MHz). Reliability of MIP ultrasound imaging was tested following 2 injections of the same microbubble concentration (5 × 10⁷ microbubbles at 1.2 mL/min) in the same tumors. In mice with subcutaneous human colon cancer xenografts, longitudinal contrast-enhanced ultrasound MIP imaging plateau values (baseline and at 48 hours) were compared between mice with and without antiangiogenic treatment (antivascular endothelial growth factor antibody). Ex vivo CD31 immunostaining of tumor tissue was used to correlate in vivo MIP imaging plateau values with microvessel density analysis.

RESULTS

In vivo MIP imaging plateau values correlated significantly (P = 0.001) with contrast microbubble doses. At 3 different injection rates of 0.6, 1.2, and 2.4 mL/min, MIP imaging plateau values did not change significantly (P = 0.61). Following 2 injections with the same microbubble dose and injection rate, MIP imaging plateau values were obtained with high reliability with an intraclass correlation coefficient of 0.82 (95% confidence interval: 0.64, 0.94). In addition, in vivo MIP imaging plateau values significantly correlated (P = 0.01; R² = 0.77) with ex vivo microvessel density analysis. Tumor volumes in treated and nontreated mice did not change significantly (P = 0.22) within 48 hours. In contrast, the change of in vivo MIP imaging plateau values from baseline to 48 hours was significantly different (P = 0.01) in treated versus nontreated mice.

CONCLUSIONS

Contrast-enhanced ultrasound MIP imaging allows reliable assessment of tumor vascularity and monitoring of antiangiogenic cancer therapy in vivo, provided that a constant microbubble dose is administered.