The worldwide prevalence of Non-alcoholic Fatty Liver Disease (NAFLD) raises concerns about associated risk factors, such as obesity and type 2 Diabetes Mellitus, for leading causes of disability and death. Besides Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS), functional imaging with Positron Emission Tomography (PET) could contribute to a deeper understanding of the pathophysiology of NAFLD. Here we describe a novel approach using the PET tracer [¹⁸F]FTHA, which is an analog of long-chain free fatty acids (FFA) and is taken up by tissues to enter mitochondria or to be incorporated into complex lipids for further export as very-low-density lipoprotein (VLDL). Male Sprague Dawley rats, after 6 weeks on a high-fat diet (HFD), were used as a model of diet induced NAFLD, while a standard diet (SD) served as a control group. Liver fat was estimated by MR spectroscopy at a 9.4 T system for phenotyping. To measure hepatic FFA uptake, rats underwent 60 min dynamic [¹⁸F]FTHA-PET scans after unrestricted access to food (HFD: n = 6; SD: n = 6) or overnight (≤16h) fasting (HFD: n = 6; SD: n = 5). FFA removal was assessed from incorporated ¹⁸F-residual in de novo synthesized VLDL out of plasma. MRS of the liver confirmed the presence of NAFLD (>5.6% fat). Under non-fasting conditions, hepatic [¹⁸F]FTHA uptake was significantly increased in NAFLD: SUVmean (p = 0.03) within [0; 60] min interval, SUVmean (p = 0.01) and SUVmax (p = 0.03) within [30; 60] min interval. SUVs for hepatic uptake under fasting conditions were not significantly different between the groups. Analysis of FFA removal demonstrated elevated values of ¹⁸F-residue in the VLDL plasma fraction of the healthy group compared to the NAFLD (p = 0.0569). Our novel approach for assessing FFA metabolism using [¹⁸F]FTHA demonstrated differences in the hepatic FFA uptake and FFA incorporation into VLDL between healthy and NAFLD rats. [¹⁸F]FTHA-PET could be used to study metabolic disturbances involved in the progression of NAFLD.

Tumor neoangiogenesis is an important hallmark of cancer progression, triggered by alternating selective pressures from the hypoxic tumor microenvironment. Non-invasive, non-contrast-enhanced multiparametric MRI combining blood-oxygen-level-dependent (BOLD) MRI, which depicts blood oxygen saturation, and intravoxel-incoherent-motion (IVIM) MRI, which captures intravascular and extravascular diffusion, can provide insights into tumor oxygenation and neovascularization simultaneously. Our objective was to identify imaging markers that can predict hypoxia-induced angiogenesis and to validate our findings using multiplexed immunohistochemical analyses. We present an in vivo study involving 36 female athymic nude mice inoculated with luminal A, Her2+, and triple-negative breast cancer cells. We used a high-field 9.4-tesla MRI system for imaging and subsequently analyzed the tumors using multiplex immunohistochemistry for CD-31, PDGFR-β, and Hif1-α. We found that the hyperoxic-BOLD-MRI-derived parameter ΔR2* discriminated luminal A from Her2+ and triple-negative breast cancers, while the IVIM-derived parameter fIVIM discriminated luminal A and Her2+ from triple-negative breast cancers. A comprehensive analysis using principal-component analysis of both multiparametric MRI- and mpIHC-derived data highlighted the differences between triple-negative and luminal A breast cancers. We conclude that multiparametric MRI combining hyperoxic BOLD MRI and IVIM MRI, without the need for contrast agents, offers promising non-invasive markers for evaluating hypoxia-induced angiogenesis.

Alterations in tricarboxylic acid (TCA) cycle metabolism are associated with hepatic metabolic disorders. Elevated hepatic acetate concentrations, often attributed to high caloric intake, are recognized as a pivotal factor in the etiology of obesity and metabolic syndrome. Therefore, the assessment of acetate breakdown and TCA cycle activity plays a central role in understanding the impact of diet‐induced alterations on liver metabolism. Magnetic resonance‐based deuterium metabolic imaging (DMI) could help to unravel the underlying mechanisms involved in disease development and progression, however, the application of conventional deuterated glucose does not lead to substantial enrichment in hepatic glutamine and glutamate. This study aimed to demonstrate the feasibility of DMI for tracking deuterated acetate breakdown via the TCA cycle in lean and diet‐induced fatty liver (FL) rats using 3D DMI after an intraperitoneal infusion of sodium acetate‐d3 at 9.4T. Localized and nonlocalized liver spectra acquired at 10 time points post‐injection over a 130‐min study revealed similar intrahepatic acetate uptake in both animal groups (AUC_FL = 717.9 ± 131.1 mM▯min⁻¹, AUC_lean = 605.1 ± 119.9 mM▯min⁻¹, p = 0.62). Metabolic breakdown could be observed in both groups with an emerging glutamine/glutamate (Glx) peak as a downstream metabolic product (AUC_FL = 113.6 ± 23.8 mM▯min⁻¹, AUC_lean = 136.7 ± 41.7 mM▯min⁻¹, p = 0.68).This study showed the viability of DMI for tracking substrate flux through the TCA cycle, underscoring its methodological potential for imaging metabolic processes in the body.

Background: One of the main features of several metabolic disorders is dysregulation of hepatic glucose and lipid metabolism. Deuterium metabolic imaging (DMI) allows for assessing the uptake and breakdown of ²H‐labeled substrates, giving specific insight into nutrient processing in healthy and diseased organs. Thus, DMI could be a useful approach for analyzing the differences in liver metabolism of healthy and diseased subjects to gain a deeper understanding of the alterations related to metabolic disorders.Purpose: Evaluating the feasibility of DMI as a tool for the assessment of metabolic differences in rodents with healthy and fatty livers (FLs).Study Type: Animal Model.Population: 18 male Sprague Dawley rats on standard (SD, n = 9, healthy) and high‐fat diet (HFD, n = 9, FL disease).Field Strength/Sequence: Phase‐encoded 1D pulse‐acquire sequence and anatomy co‐registered phase‐encoded 3D pulse‐acquire chemical shift imaging for ²H at 9.4T.Assessment: Localized and nonlocalized liver spectroscopy was applied at eight time points over 104 minutes post injection. The obtained spectra were preprocessed and quantified using jMRUI (v7.0) and the resulting amplitudes translated to absolute concentration (mM) according to the ²H natural abundance water peak.Statistical Tests: Two‐way repeated measures ANOVA were employed to assess between‐group differences, with statistical significance at P < 0.05.Results: DMI measurements demonstrated no significant difference (P = 0.98) in the uptake of [6,6′‐²H₂]glucose between healthy and impaired animals (AUC_SD = 1966.0 ± 151.5 mM ‐ minutes vs. AUC_HFD = 2027.0 ± 167.6 mM·minutes). In the diseased group, the intrahepatic uptake of palmitic acid d‐31 was higher (AUC_HFD = 57.4 ± 17.0 mM·minutes, AUC_SD = 33.3 ± 10.5 mM·minutes), but without statistical significance owing to substantial in‐group variation (P = 0.73).Data Conclusion: DMI revealed higher concentrations of palmitic acid in rats with FL disease and no difference in hepatic glucose concentration between healthy and impaired animals. Thus, DMI appears to be a useful tool for evaluating metabolism in rodents with FL disease.Level of Evidence: 2Technical Efficacy: Stage 3.

Hyperoxic BOLD-MRI targeting tumor hypoxia may provide imaging biomarkers that represent breast cancer molecular subtypes without the use of injected contrast agents. However, the diagnostic performance of hyperoxic BOLD-MRI using different levels of oxygen remains unclear. We hypothesized that molecular subtype characterization with hyperoxic BOLD-MRI is feasible independently of the amount of oxygen. Twenty-three nude mice that were inoculated into the flank with luminal A (n = 9), Her2⁺ (n = 5), and triple-negative (n = 9) human breast cancer cells were imaged using a 9.4 T Bruker BioSpin system. During BOLD-MRI, anesthesia was supplemented with four different levels of oxygen (normoxic: 21%; hyperoxic: 41%, 71%, 100%). The change in the spin–spin relaxation rate in relation to the normoxic state, $\Delta R_2{}^{*}$, dependent on the amount of erythrocyte-bound oxygen, was calculated using in-house MATLAB code. $\Delta R_2{}^{*}$ was significantly different between luminal A and Her2⁺ as well as between luminal A and triple-negative breast cancer, reflective of the less aggressive luminal A breast cancer’s ability to better deliver oxygen-rich hemoglobin to its tissue. Differences in $\Delta R_2{}^{*}$ between subtypes were independent of the amount of oxygen, with robust distinction already achieved with 41% oxygen. In conclusion, hyperoxic BOLD-MRI may be used as a biomarker for luminal A breast cancer identification without the use of exogenous contrast agents.