Hyperpolarized carbon 13 MRI in liver diseases: Recent advances and future opportunities

In vivo Hyperpolarized Metabolic Imaging to Monitor the Progression of Hepatitis B Virus (HBV)-Related Hepatitis to Liver Fibrosis

PURPOSE

This study aimed to assess metabolic changes to monitor the progression from normal liver to hepatitis B virus (HBV)-related hepatitis and liver fibrosis using hyperpolarized 13C magnetic resonance imaging (MRI).

PROCEDURES

Hepatitis was induced in mice (n = 16) via hydrodynamic injection of HBV 1.2 plasmid (25 μg). Among them, liver fibrosis was induced in the mice (n = 8) through weight-adapted administration of thioacetamide with ethanol. Normal control mice (n = 8) were injected with a phosphate buffer solution. Subsequently, a hyperpolarized 13C MRI was performed on the mouse liver in vivo. The level of hepatitis B surface antigen (HBsAg) in blood serum was measured. Statistical analysis involved comparing the differential metabolite ratios, blood biochemistry values, and body weight among the three groups using the Kruskal-Wallis one-way analysis of variance.

RESULTS

HBsAg was absent in the normal and fibrosis groups, while it was detected in the hepatitis group. The ratios of [1-13C] lactate/pyruvate, [1-13C] alanine/pyruvate, [1-13C] lactate/total carbon, and [1-13C] alanine/total carbon were significantly lower in the normal control group than in the hepatitis and fibrosis groups (p < 0.05). Moreover, these ratios were significantly higher in the fibrosis group than in the hepatitis group (p < 0.05). However, no significant differences were observed in either [1-13C] pyruvate-hydrate/pyruvate or [1-13C] pyruvate-hydrate/total carbon among the three groups.

CONCLUSIONS

The levels of [1-13C] lactate and [1-13C] alanine in vivo may serve as valuable indicators for differentiating between HBV-related hepatitis, liver fibrosis, and normal liver.

Hyperpolarized Carbon-13 Magnetic Resonance Imaging: Technical Considerations and Clinical Applications

Hyperpolarized (HP) carbon-13 (13C) MRI represents an innovative approach for noninvasive, real-time assessment of dynamic metabolic flux, with potential integration into routine clinical MRI. The use of [1-13C]pyruvate as a probe and its conversion to [1-13C]lactate constitute an extensively explored metabolic pathway. This review comprehensively outlines the establishment of HP 13C-MRI, covering multidisciplinary team collaboration, hardware prerequisites, probe preparation, hyperpolarization techniques, imaging acquisition, and data analysis. This article discusses the clinical applications of HP 13C-MRI across various anatomical domains, including the brain, heart, skeletal muscle, breast, liver, kidney, pancreas, and prostate. Each section highlights the specific applications and findings pertinent to these regions, emphasizing the potential versatility of HP 13C-MRI in diverse clinical contexts. This review serves as a comprehensive update, bridging technical aspects with clinical applications and offering insights into the ongoing advancements in HP 13C-MRI.

Quo Vadis Hyperpolarized 13C MRI?

Over the last two decades, hyperpolarized 13C MRI has gained significance in both preclinical and clinical studies, hereby relying on technologies like PHIP-SAH (ParaHydrogen-Induced Polarization-Side Arm Hydrogenation), SABRE (Signal Amplification by Reversible Exchange), and dDNP (dissolution Dynamic Nuclear Polarization), with dDNP being applied in humans. A clinical dDNP polarizer has enabled studies across 24 sites, despite challenges like high cost and slow polarization. Parahydrogen-based techniques like SABRE and PHIP offer faster, more cost-efficient alternatives but require molecule-specific optimization. The focus has been on imaging metabolism of hyperpolarized probes, which requires long T1, high polarization and rapid contrast generation. Efforts to establish novel probes, improve acquisition techniques and enhance data analysis methods including artificial intelligence are ongoing. Potential clinical value of hyperpolarized 13C MRI was demonstrated primarily for treatment response assessment in oncology, but also in cardiology, nephrology, hepatology and CNS characterization. In this review on biomedical hyperpolarized 13C MRI, we summarize important and recent advances in polarization techniques, probe development, acquisition and analysis methods as well as clinical trials. Starting from those we try to sketch a trajectory where the field of biomedical hyperpolarized 13C MRI might go.

[6,6'-2 H2 ] fructose as a deuterium metabolic imaging probe in liver cancer

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths. Imaging plays a crucial role in the early detection of HCC, although current methods are limited in their ability to characterize liver lesions. Most recently, deuterium metabolic imaging (DMI) has been demonstrated as a powerful technique for the imaging of metabolism in vivo. Here, we assess the metabolic flux of [6,6'-2 H2 ] fructose in cell cultures and in subcutaneous mouse models at 9.4 T. We compare these rates with the most widely used DMI probe, [6,6'-2 H2 ] glucose, exploring the possibility of developing 2 H fructose to overcome the limitations of glucose as a novel DMI probe for detecting liver tumors. Comparison of the in vitro metabolic rates implies their similar glycolytic metabolism in the TCA cycle due to comparable production rates of 2 H glutamate/glutamine (glx) for the two precursors, but overall higher glycolytic metabolism from 2 H glucose because of a higher production rate of 2 H lactate. In vivo kinetic studies suggest that HDO can serve as a robust reporter for the consumption of the precursors in liver tumors. As fructose is predominantly metabolized in the liver, deuterated water (HDO) produced from 2 H fructose is probably less contaminated from whole-body metabolism in comparison with glucose. Moreover, in studies of the normal liver, 2 H fructose is readily converted to 2 H glx, enabling the characterization of 2 H fructose kinetics. This overcomes a major limitation of previous 2 H glucose studies in the liver, which were unable to confidently discern metabolic flux due to overlapped signals of 2 H glucose and its metabolic product, 2 H glycogen. This suggests a unique role for 2 H fructose metabolism in HCC and the normal liver, making it a useful approach for assessing liver-related diseases and the progression to oncogenesis.

Enhancing Cancer Diagnosis with Real-Time Feedback: Tumor Metabolism through Hyperpolarized 1-13C Pyruvate MRSI

This review article discusses the potential of hyperpolarized (HP) 13C magnetic resonance spectroscopic imaging (MRSI) as a noninvasive technique for identifying altered metabolism in various cancer types. Hyperpolarization significantly improves the signal-to-noise ratio for the identification of 13C-labeled metabolites, enabling dynamic and real-time imaging of the conversion of [1-13C] pyruvate to [1-13C] lactate and/or [1-13C] alanine. The technique has shown promise in identifying upregulated glycolysis in most cancers, as compared to normal cells, and detecting successful treatment responses at an earlier stage than multiparametric MRI in breast and prostate cancer patients. The review provides a concise overview of the applications of HP [1-13C] pyruvate MRSI in various cancer systems, highlighting its potential for use in preclinical and clinical investigations, precision medicine, and long-term studies of therapeutic response. The article also discusses emerging frontiers in the field, such as combining multiple metabolic imaging techniques with HP MRSI for a more comprehensive view of cancer metabolism, and leveraging artificial intelligence to develop real-time, actionable biomarkers for early detection, assessing aggressiveness, and interrogating the early efficacy of therapies.

Multinuclear MRI in Drug Discovery

The continuous development of magnetic resonance imaging broadens the range of applications to newer areas. Using MRI, we can not only visualize, but also track pharmaceutical substances and labeled cells in both in vivo and in vitro tests. ¹H is widely used in the MRI method, which is determined by its high content in the human body. The potential of the MRI method makes it an excellent tool for imaging the morphology of the examined objects, and also enables registration of changes at the level of metabolism. There are several reports in the scientific publications on the use of clinical MRI for in vitro tracking. The use of multinuclear MRI has great potential for scientific research and clinical studies. Tuning MRI scanners to the Larmor frequency of a given nucleus, allows imaging without tissue background. Heavy nuclei are components of both drugs and contrast agents and molecular complexes. The implementation of hyperpolarization techniques allows for better MRI sensitivity. The aim of this review is to present the use of multinuclear MRI for investigations in drug delivery.