Keywords: Biology, Models, Methods, Diffusion/other diffusion imaging techniques, inflammation, brain, degeneration, demyelination

Motivation: Validation of MRI-extracted biomarkers is seldom performed, and when available,
Is normally underpowered and based on correlation.

Goal(s): Here we present an innovative framework for validating microstructural MRI biomarkers by eliciting cell-specific responses.

Approach: The framework is based on injection of neurotoxins in rats, followed by MRI exploration and histology.

Results: We successfully isolated conditions associated to neurodegenerative, demyelinating and inflammatory pathologies and demonstrated sensitivity and specificity of MRI- derived biomarkers.

Impact: This framework impulse a much-needed change in paradigm for MRI validation by challenging the biological content of MRI derived biomarkers, refine and test new models for microstructural imaging and bridge the gap between advances in MRI physics and clinical applications.

Keywords: Biomarkers, Alzheimer's Disease

Motivation: Nicotinamide riboside (NR) supplementation has increased in popularity for treating neurodegenerative diseases and is attributed to elevated NAD⁺ levels. Effective monitoring of NR-mediated changes may highlight metabolic underpinnings of NR in dementia.

Goal(s): This study uses glutamate-CEST MRI to monitor changes in glutamate levels following NR supplementation in wild-type and 5XFAD mouse models of AD.

Approach: Mice (WT and AD) were treated with NR or a vehicle (placebo) for 12 weeks followed by GluCEST MRI.

Results: There was a significant GluCEST increase in AD mice compared to WT. Following NR, GluCEST decreased in AD mice, primarily in the hippocampus.

Impact: NR supplementation may help alleviate excitotoxicity in AD, thereby preventing neuronal cell death/degeneration. GluCEST provides an effective method for assessing changes in glutamate levels, allowing for monitoring excitotoxicity in patients presenting symptoms of AD and the effects of NR treatment.

Keywords: Neurofluids, Neurofluids, Contrast Agent, Quantitative MR, Glymphatic System

Motivation: Quantitative MR provides the opportunity of quantifying concentration of contrast agent and its transport in cerebrospinal fluid (CSF) in the whole brain. 

Goal(s): To develop a fast multi-parametric mapping method tailored to dynamically and quantitatively assessing Gd-DTPA transport in mouse brain.

Approach: We designed and validated a new 3D MR fingerprinting (MRF) sequence with subspace-based reconstruction to simultaneously track T₁ and T₂ changes in mouse brain following intrathecal contrast infusion with a temporal resolution of <4.5 min at 9.4T. 

Results: Dynamic T₁ and T₂ changes allowed direct quantification of transport kinetics in different brain regions between multiple subjects without normalization. 

Impact: We present the first 3D MR fingerprinting method for dynamic quantification of contrast agent transport in rodent brains. With unprecedented speed, accuracy, and robustness, our method offers unlimited opportunities for multi-parametric quantification in various preclinical imaging applications.  

Keywords: Large Animals, Nonhuman Primates, Normal development, normal development, large animals-nonhuman primates, ultra-high resolution diffusion MRI, common coordinate framework

Motivation: Integrating a spatially resolved and molecularly defined cell atlas with studies of developing brain function, neurophysiology, and behavior will require an anatomical common coordinate framework (CCF). Ultra-high-resolution diffusion-MRI (dMRI) improves anatomical determinations and provides rich contrasts and microstructural information.

Goal(s): To build the first dMRI-based anatomical CCF for infant marmoset brains.

Approach: Ultra-high resolution dMRI at 9.4T was performed on a 10-month-old marmoset brain. Anatomical regions were delineated. 

Results: An ultra-high-resolution CCF for the infant marmoset brain at isotropic 0.1mm diffusion MR imaging resolution, characterized by comprehensive labels of fine neuroanatomical structures and coordinate framework.

Impact: The first infant marmoset brain CCF will allow integrating spatially resolved, molecularly defined cell atlas with studies of developing brain function, neurophysiology, and behavior. It will provide insights into evolution and human-specific features of brain development relevant to brain disorders.

Keywords: Preclinical Image Analysis, Data Analysis, template, Allen brain

Motivation: Overcoming sex bias in preclinical research requires unbiased tools. Equitable sex representation in the creation of the atlas is seldom achieved, but failing to do so might introduce bias in the analysis.

Goal(s): Our goal was to create a mouse MRI template that includes animals of both sexes, incorporating both structural and diffusion contrasts, and then compare it with a single-sex template.

Approach: We scanned a large cohort of mice, including both sexes, to generate a template and registered the Allen annotation to it.

Results: Using single-sex templates generates spurious sex differences that are not present when using resources with equitable sex representation.

Impact: The MouseX DW-Allen Atlas is the first mouse MRI template that adopts the Allen annotation and is built with both sexes. It fills an important gap in preclinical imaging research, promotes gender equality, and fosters collaborative and multi-approach science.

Keywords: Spectroscopy, Metabolism, MRS, hepatic encephalopathy, sex-difference, SPECIAL

Motivation: The lack of preclinical studies on potential sex-differences in the pathophysiology of hepatic encephalopathy (HE) prevents a comprehensive understanding of the disease.  

Goal(s): To study the effect of sex on the neurometabolic profiles measured with ¹H MRS.

Approach: We compared ¹H MRS metabolite concentrations in the hippocampus and striatum of young male versus female rats with HE.

Results: We observed overall stronger neurometabolic effects of the disease on male versus female HE rats, including weight loss and decrease in brain antioxydants levels (Asc, GSH), likely hampering the capacity of male animals to counteract oxidative stress, important player in the pathophysiology of HE.

Impact: Sex-differences, often overlooked in preclinical studies, investigated here showed distinct ¹H MRS neurometabolic profiles in female versus male rats with hepatic encephalopathy (HE), opening a new window of investigation for patients with HE. 

Keywords: Small Animals, Metabolism, Diabetes, Lipids, MRS

Motivation: Obesity is one of the main risk factors for type 2 diabetes and is also associated with an increased cardiovascular risk. However, the transition from the early states of impaired glucose intolerance to a more progressive disease stage still remains elusive.

Goal(s): To identify biomarkers and time points for early therapeutic interventions to stop further transition.

Approach: We used an established mouse model exposed for 9 weeks to a diabetogenic diet and longitudinally monitored important organs/tissues by MRI+MRS. 

Results: Using MRS we could detect massive accumulation of lipids in all organs which preceded even a sigificant weight gain in DD-fed mice.

Impact: MRS of intramyocellular lipids was most sensitive to reveal in vivo very early alterations in the prediabetic state and, thus, may also be used in humans to identify patients at the transition point from prediabetes to diabetes. 

Keywords: Biology, Models, Methods, Cancer, preclinical, biomarkers, elastography

Motivation: Invasive lobular carcinoma (ILC) is a major subtype of breast cancer but remains very difficult to detect until late stage. There is a lack of sensitive imaging techniques for the diagnosis of ILC.

Goal(s): To define clinically-translatable MRI biomarkers of the heterogeneous tumour microenvironment in ILC.

Approach: A Mouse-INtraDuctal (MIND) model was used to emulate late stage ILC. Multiparametric MRI was performed on ~10 month-old tumours.

Results: ILC exhibited bimodal ADC and stiffness profiles. Invasive tumour regions displayed low ADC and elevated stiffness compared to lobular in situ regions.

Impact: Multiparametric MRI can inform on the evolving microenvironment within MIND model of invasive lobular carcinoma.
Invasive regions displayed restricted water diffusion and elevated stiffness, highlighting the utility of DWI and MRE as informative techniques for detecting and assessing invasiveness.

Keywords: Probes & Targets, Molecular Imaging

Motivation: It is in urgent need to develop an imaging method to reveal the intrinsic ‘cold’ or ‘hot’ status of tumor microenvironment for glioma patients, which would offer guidance for planning therapeutic regimen, and thus maximize the therapeutic efficacy and reduce unnecessary treatment.

Goal(s): To visualize the inflammatory status of glioma tumor microenvironment non-invasively using myeloperoxidase responsive NaGdF₄-based nanoprobes under MRI.

Approach: Different glioma models with different inflammatory status were created and imaged with our nanoprobes under 11.7 T at T1WI (n = 6 each group). 

Results: MPO-enriched ‘hot’ gliomas showed patchy hypointense T1 signal while MPO-rare ‘cold’ gliomas presented moderate hyperintensity in T1WI. 

Impact: Depending on the level of MPO in tumor microenvironment, nanoprobes will get self-assembled in various degree, thus altering T1 relaxation time. By using this, it is promising to monitor the tumor inflammatory status for glioma patients thus guide clinical treatment.

Keywords: Preclinical Image Analysis, Elastography, Cancer, HCC

Motivation: The biomechanical interplay between hepatocellular carcinoma (HCC) and the hosting liver is poorly understood.

Goal(s): To characterize the development of HCC and its interactions with the surrounding liver using imaging-based biophysical properties.

Approach: We investigated longitudinally HCC and the host liver in an orthotopic mouse model using MR elastography (MRE) and diffusion-weighted imaging (DWI).

Results: During tumor development, the host liver became softer with reduced viscosity and restricted water diffusivity while HCC became stiffer, less viscous and restricted water diffusivity.

Impact: Preclinical MRE is a useful tool to study biomechanical properties of tumors and the tumor environment. In a mouse model of hepatocellular carcinoma, we showed for the first time how liver tumors shape their biomechanical niche in the hosting liver.

Keywords: Preclinical Image Analysis, Diffusion/other diffusion imaging techniques, liver fibrosis, multiparametric MRI, T1rho

Motivation: Early detection and noninvasive assessment of liver fibrosis are significant in clinical practice.

Goal(s): Liver biopsy have some drawbacks for staging liver fibrosis. We aimed to investigated the value of T1ρ, DKI, and IVIM in assessment of liver fibrosis and established an optimal diagnostic model.

Approach: Twenty four thioacetamide (TAA)-treated rats and six control rats were included in this experimental study. All rats were scanned with 3.0T MRI machine. Corresponding imaging parameters were measured and compared among different fibrosis stages.

Results: T1ρ and MD derived from DKI had better diagnostic performance than other parameters. Their combination model further improved the diagnostic efficiency.

Impact: T1ρ and DKI could easily incorporated into routine liver MR imaging. The model combining T1ρ and MD derived from DKI was promising to be a noninvasive biomarker to detect and accurately stage liver fibrosis in the clinical practice.

Keywords: Probes & Targets, Tumor

Motivation: gadolinium widely used in MRI clincally show low detecting efficiency for early pancreatic cancer(<2 cm). It is thus urgent to develop safe and effective contrast agents to address this issue. 

Goal(s): This study aims to investigate the potential of cancer cell membrane coated Mn(II) nanoprobes (PMNP@CMs) in MRI for precise diagnosis of early pancreatic cancer.

Approach: PMNP@CMs were prepared for MRI of pancreatic cancer to explore the imaging effects in vivo and in vitro compared with gadolinium. 

Results: PMNP@CMs showed more predominant MRI effect than gadolinium and may be considered as safe and efficient contrast agents to realize diagnosis for early pancreatic cancer.

Impact: This work has developed a nano magnetic resonance imaging contrast agent (PMNP@CMs) that is more advantageous than gadolinium and can achieve precise diagnosis of early pancreatic cancer.

Keywords: Biology, Models, Methods, Cancer, prostate, metabolomics

Motivation: The progression of prostate cancer is marked by both RB1 and T53 inactivation and higher ¹⁸FDG-PET uptake, but it's unclear whether RB1 or TP53 inactivation drives increased glucose import.

Goal(s): Can metabolic changes be used as a biomarker for RB1 and TP53 loss?

Approach: Metabolomic analysis by NMR and IC-MS for a comprehensive measure of metabolic changes ex vivo and and hyperpolarized MRI to measure the Warburg effect in vivo.

Results: ¹⁸FDG uptake was unaffected by loss of either RB1 or TP53. RB1 and TP53 did induce a series of other metabolic changes which could be detected in vivo by hyperpolarized MRI

Impact: Neuroendrocrine prostate cancer is a life-threatening progression of prostate cancer that is characterized by mutations in two key genes. Hyperpolarized MRI may enhance early diagnosis of NEPC without biopsy.

Keywords: Biology, Models, Methods, Preclinical, Diaphragm, Small Animals, Thorax, 3D CINE imaging

Motivation: The pathophysiology of diaphragm dysfunction in mechanically ventilated patients is not fully understood and adequate animal models are required to accommodate further research. 

Goal(s): Our goal was to develop a method to image 3D thoracic movement during mechanical ventilation of mice and rats at different pressure levels of mechanical ventilation. 

Approach: With our setup we visualized the movement of the thorax in mice and rats using self-gated 3D pseudo-radial k-space sampling.

Results: Imaging was feasible in both animal types and increase of pressure resulted in a decrease of mean diaphragm excursion of 0.9 and 1.3 mm in mouse and rat respectively.

Impact: Our proposed setup allows controlled mechanical ventilation and MR imaging of 3D thorax movement in mice and rats. This can be used to study the pathophysiology behind mechanical ventilation-induced respiratory muscle dysfunction, and ultimately guiding clinical practice in respiratory care.

Keywords: Preclinical Image Analysis, Diffusion/other diffusion imaging techniques

Motivation: The orientation of the cardiomyocytes can be probed non-invasively with diffusion imaging. In-vivo, this is typically assessed by the orientation of the primary eigenvector in a diffusion tensor model, although questions remain about the ability of this model to probe complex cardiomyocyte arrangements.

Goal(s): To assess the agreement of cardiomyocyte orientation measures given by a diffusion tensor and a more robust q-ball model.

Approach: A diffusion tensor model was compared to a q-ball diffusion model in a healthy porcine heart.

Results: Median angular deviations of 7.8 and 10.8 degrees were found for the main diffusion direction between the two models.

Impact: We provide an estimate of cardiomyocyte angular orientation differences between a diffusion tensor model and a more robust diffusion q-ball model with a higher angular resolution in a healthy porcine heart.

Keywords: Small Animals, CEST & MT

Motivation: There is a gap in exploring the progression of acute kidney injury (AKI) caused by rhabdomyolysis (RM).

Goal(s): Investigate the feasibility of CEST MRI for assessing the progression of RM-induced AKI in a mouse model.

Approach: The RM-AKI model was established by intramuscular injection of glycerol solution and examined longitudinally by CEST (days 1, 3, 7, 15, 30). CEST quantification parameters and their diagnostic performance were compared.

Results: MTR presented a significant difference, and showed the best diagnostic performance for AKI and moderate negative correlations with pathological changes.

Impact: MTR has potential clinical utility for assessing renal diseases.

Keywords: Small Animals, Preclinical, Sodium MRI

Motivation: Currently, there is a lack of research in ²³Na-MRI, investigating the renal sodium concentration gradient in Sepsis-Induced acute kidney injury (AKI).  

Goal(s): This study aimed to investigate sodium concentration changes across the renal parenchyma and to compare them with T₁, T₂, and T₂* alterations as well as kidney perfusion. 

Approach: 38 mice (N=19 as control and N=19 with septic AKI) were investigated by multi-parametric MRI. 

Results: In septic AKI, thrombi developed in kidneys and caused renal hypoperfusion. Lack of blood supply to kidneys resulted in sodium retention at cortex and little sodium output at pelvis even in the absence of detectable edema.

Impact: This study helps to better understand the radiological pathology of sepsis-induced acute kidney injury in ²³Na-MRI. It connects the concept of altered sodium concentration with changes in renal perfusion, T₁, T₂, and T₂* relaxation constants.

Keywords: Epilepsy, Deuterium

Motivation: Children with Dravet syndrome, a drug-resistant epilepsy, often show a positive response to the ketogenic diet (KD) where the TCA cycle is driven mainly by ketones.

Goal(s): To monitor TCA cycle metabolism of ketone body β-hydroxybutyrate in wild-type and Dravet mouse models comparing normal diet (ND) vs. KD.

Approach: Deuterium (²H) single-voxel brain MRS is applied to wild-type and Dravet mouse models following subcutaneous administration of [3,4,4,4-²H₄]β-hydroxybutyrate.

Results: Mice on KD vs. ND show enhanced brain uptake of β-hydroxybutyrate (p < 0.001) with subsequent increase in glutamine+glutamate (“Glx”) production (p < 0.002), evidence that the KD upregulates brain monocarboxylate transporters.

Impact: Deuterium metabolic imaging quantification of TCA cycle flux in individual Dravet patients may (i) assess metabolic dysfunction, (ii) assist in selecting the best treatment option, and (iii) allow optimization of the diet. Hence development of a personalized treatment plan.

Keywords: Small Animals, Metabolism, Deuterium metabolic imaging; Tumor; Glycolytic enzyme

Motivation: Enzyme expression plays a crucial role in tumor metabolism, influencing tumor development and response to therapy. However, there is a lack of non-invasive techniques to measure the expression of glycolytic enzymes in research and clinics.

Goal(s): Verify whether Deuterium metabolic imaging (DMI), a promising non-invasive technique, can effectively monitor the expression changes of glycolysis enzyme in vivo.

Approach: Utilize deuterium MRS/MRI to monitor metabolic flux in two groups of mice with control tumor and HK2 knockdown tumor.

Results: DMI can indirectly monitor the expression changes of glycolytic enzymes represented by HK2 in vivo by measuring metabolic flux.

Impact: This study provides a non-invasive technique for measuring glycolytic enzyme expression of tumors in vivo. The proposed method might have clinical potential in cancer treatment management and response monitoring in a timely manner.

Keywords: Biomarkers, Quantitative Imaging

Motivation: Diagnostic delay and uncertainty are common problems faced by patients suffering from endometriosis. Although laparoscopy remains the gold-standard for diagnosis, quantitative MRI (qMRI) could offer an alternative non-invasive approach.

Goal(s): To use qMRI to characterise endometriotic lesions.

Approach: Quantitative analysis of multiparametric MRI data (including T1 MOLLI, T2* and PDFF parametric maps) to characterise tissue metrics obtained from patients suffering with chronic pelvic pain who subsequently underwent a diagnostic laparoscopy.

Results: Endometriomas have characteristic qMRI values different to other tissues in the female pelvis.

Impact: The distinctive parametric characteristics of endometriomas provides a foundation for the development of a non-invasive diagnostic tool that can detect endometriotic lesions within the pelvis.