Melatonin reduces brain injury following inflammation-amplified hypoxia-ischemia in a translational newborn piglet study of neonatal encephalopathy.

There is a need to develop therapies for neonatal encephalopathy (NE) in low- and middle-income countries (LMICs) where the burden of disease is greatest and therapeutic hypothermia (HT) is not effective. We aimed to assess the efficacy of melatonin following inflammation-amplified hypoxia-ischaemia (IA-HI) in the newborn piglet. The IA-HI model accounts for the contribution of infection/inflammation in this setting and HT is not cytoprotective. We hypothesised that intravenous melatonin (5% ethanol, at 20 mg/kg over 2 h at 1 h after HI + 10 mg/kg/12 h between 24 and 60 h) is safe and associated with: (i) reduction in magnetic resonance spectroscopy lactate/N-acetylaspartate (MRS Lac/sNAA); (ii) preservation of phosphorus MRS phosphocreatine/phosphate exchange pool (PCr/Epp); (iii) improved aEEG/EEG recovery and (iv) cytoprotection on immunohistochemistry. Male and female piglets underwent IA-HI by carotid artery occlusion and reduction in FiO2 to 6% at 4 h into Escherichia coli lipopolysaccharide sensitisation (2 µg/kg bolus + 1 µg/kg/h over 12 h). At 1 h after IA-HI, piglets were randomised to HI-saline (n = 12) or melatonin (n = 11). There were no differences in insult severity between groups. Target melatonin levels (15-30 mg/L) were achieved within 3 h and blood ethanol levels were <0.25 g/L. At 60 h, compared to HI-saline, melatonin was associated with a reduction of 0.197 log10 units (95% CrI [-0.366, -0.028], Pr(sup) 98.8%) in basal-ganglia and thalamic Lac/NAA, and 0.257 (95% CrI [-0.676, 0.164], Pr(sup) 89.3%) in white matter Lac/NAA. PCr/Epp was higher in melatonin versus HI-saline (Pr(sup) 97.6%). Melatonin was associated with earlier aEEG/EEG recovery from 19 to 24 h (Pr(sup) 95.4%). Compared to HI-saline, melatonin was associated with increased NeuN+ cell density (Pr(sup) 99.3%) across five of eight regions and reduction in TUNEL-positive cell death (Pr(sup) 89.7%). This study supports the translation of melatonin to early-phase clinical trials. Melatonin is protective following IA-HI where HT is not effective. These data guide the design of future dose-escalation studies in the next phase of the translational pipeline.

A simple, clinically usable whole-body MRI system of joint assessment in adolescents and young people with juvenile idiopathic arthritis.

OBJECTIVES: To introduce and evaluate a simple method for assessing joint inflammation and structural damage on whole-body MRI (WBMRI) in juvenile idiopathic arthritis (JIA), which is usable in clinical practice. METHODS: The proposed system utilises post-contrast Dixon WBMRI scans. Joints are assessed for synovitis (grade 0-2) and structural damage (present/absent) at 81 sites. The synovitis grading is based on features including above-normal intensity synovial enhancement, synovial hypertrophy, joint effusion, subarticular bone marrow oedema and peri-articular soft tissue oedema.This system was evaluated in a prospective study of 60 young people (47 patients with JIA and 13 controls with non-inflammatory musculoskeletal pain) who underwent a WBMRI. Three readers (blinded to diagnosis) independently reviewed all images and re-reviewed 20 individual scans. The intra- and inter-reader overall agreement (OA) and the intra- and inter-reader Gwet's agreement coefficients 2 (GAC2) were measured for the detection of a) participants with ≥1 joint with inflammation or structural damage and b) joint inflammation or structural damage for each joint. RESULTS: The inter-reader OA for detecting patients with ≥1 joint with inflammation, defined as grade 2 synovitis (G2), and ≥1 joint with structural damage were 80% and 73%, respectively. The intra-reader OA for readers 1-3 were 80-90% and 75-90% respectively. The inter-reader OA and GAC2 for joint inflammation (G2) at each joint were both ≥85% for all joints but were lower if grade 1 synovitis was included as positive. CONCLUSION: The intra- and inter-reader agreements of this WBMRI assessment system are adequate for assessing objective joint inflammation and damage in JIA.

Detection of inflammation by whole-body MRI in young people with juvenile idiopathic arthritis.

OBJECTIVES: To assess the frequency of joint inflammation detected by whole-body MRI (WBMRI) in young people (YP) with JIA and controls, and to determine the relationship between WBMRI-detected inflammation and clinical findings. METHODS: YP aged 14-24 years, with JIA (patients) or arthralgia without JIA (controls), recruited from one centre, underwent a WBMRI scan after formal clinical assessment. Consensus between at least two of the three independent radiologists was required to define inflammation and damage on WBMRI, according to predefined criteria. YP with JIA were deemed clinically active as per accepted definitions. The proportions of YP with positive WBMRI scans for joint inflammation (≥1 inflamed joint) as well as serum biomarkers were compared between active vs inactive JIA patients and controls. RESULTS: Forty-seven YP with JIA (25 active and 22 inactive patients) and 13 controls were included. WBMRI detected joint inflammation in 60% (28/47) patients with JIA vs 15% (2/13) controls (difference: 44%, 95% CI 20%, 68%). More active than inactive JIA patients had WBMRI-detected inflammation [76% (19/25) vs 41% (9/22), difference: 35% (95% CI 9%, 62%)], and this was associated with a specific biomarker signature. WBMRI identified inflammation in ≥ 1 clinically inactive joint in 23/47 (49%) patients (14/25 active vs 9/22 inactive JIA patients). CONCLUSIONS: WBMRI's validity in joint assessment was demonstrated by the higher frequency of inflammation in JIA patients vs controls, and in active vs inactive JIA patients. WBMRI found unsuspected joint inflammation in 49% YP with JIA, which needs further investigation of potential clinical implications.

First-in-human in-vivo depiction of paraganglioma metabolism by hyperpolarised 13C-magnetic resonance.

Phaeochromocytomas (PCC) and paragangliomas (PGL), cumulatively referred to as PPGLs, are neuroendocrine tumours arising from neural crest-derived cells in the sympathetic and parasympathetic nervous systems. Predicting future tumour behaviour and the likelihood of metastatic disease remains problematic as genotype-phenotype correlations are limited, the disease has variable penetrance and, to date, no reliable molecular, cellular or histological markers have emerged. Tumour metabolism quantification can be considered as a method to delineating tumour aggressiveness by utilising hyperpolarised 13 C-MR (HP-MR). The technique may provide an opportunity to non-invasively characterise disease behaviour. Here, we present the first instance of the analysis of PPGL metabolism via HP-MR in a single case.

Measuring response to treatment in axial spondyloarthritis using quantitative imaging biomarkers: a prospective observational cohort study.

OBJECTIVE: Objective assessments of disease activity and response to treatment in axial spondyloarthritis (axSpA) remain a challenge; quantitative imaging biomarkers (QIBs) of inflammation could enhance assessments of disease activity and therapeutic response. We aimed to determine the responsiveness of QIBs obtained from diffusion-weighted imaging (DW-MRI) and chemical shift-encoded MRI (CSE-MRI) using the partially automated Bone Edema and Adiposity Characterisation with Histograms (BEACH) software tool in axSpA patients undergoing biologic therapy. METHODS: We conducted a prospective longitudinal cohort study, including 30 patients with axSpA undergoing biologic therapy. Patients were scanned before and after biologic therapy using conventional MRI, DWI and CSE-MRI at 3T. Apparent diffusion coefficient (ADC) and proton density fat fraction (PDFF) were assessed using the BEACH tool (https://github.com/TJPBray/BEACH), and conventional MR images were assessed using established visual scoring methods by expert radiologists. Responsiveness - the ability of the MRI measurements to capture changes in disease occurring as a result of biologic therapy - was assessed using the standardized response mean (SRM). Inter-reader reliability of the ADC and PDFF maps was assessed using Bland-Altman limits of agreement analysis and the intraclass correlation coefficient. RESULTS: Responsiveness to therapy was moderate for ADC-based parameters (SRM 0.50) and comparable to established visual scoring methods for bone marrow oedema (SRM 0.53). Interobserver variability was lower for QIBs compared with conventional visual scores methods. CONCLUSIONS: QIBs measured using the BEACH tool are sensitive to changes in inflammation in axSpA following biologic therapy, with similar responsiveness and lower interobserver variability to visual scoring by expert radiologists. ADVANCES IN KNOWLEDGE: QIBs measured using the partially automated BEACH tool offer an objective measure of response to biologic therapy in axSpA.

Early assessment of injury with optical markers in a piglet model of neonatal encephalopathy.

BACKGROUND: Opportunities for adjunct therapies with cooling in neonatal encephalopathy are imminent; however, robust biomarkers of early assessment are lacking. Using an optical platform of broadband near-infrared spectroscopy and diffuse correlation spectroscopy to directly measure mitochondrial metabolism (oxCCO), oxygenation (HbD), cerebral blood flow (CBF), we hypothesised optical indices early (1-h post insult) after hypoxia-ischaemia (HI) predicts insult severity and outcome. METHODS: Nineteen newborn large white piglets underwent continuous neuromonitoring as controls or following moderate or severe HI. Optical indices were expressed as mean semblance (phase difference) and coherence (spectral similarity) between signals using wavelet analysis. Outcome markers included the lactate/N-acetyl aspartate (Lac/NAA) ratio at 6 h on proton MRS and TUNEL cell count. RESULTS: CBF-HbD semblance (cerebrovascular dysfunction) correlated with BGT and white matter (WM) Lac/NAA (r2 = 0.46, p = 0.004, r2 = 0.45, p = 0.004, respectively), TUNEL cell count (r2 = 0.34, p = 0.02) and predicted both initial insult (r2 = 0.62, p = 0.002) and outcome group (r2 = 0.65 p = 0.003). oxCCO-HbD semblance (cerebral metabolic dysfunction) correlated with BGT and WM Lac/NAA (r2 = 0.34, p = 0.01 and r2 = 0.46, p = 0.002, respectively) and differentiated between outcome groups (r2 = 0.43, p = 0.01). CONCLUSION: Optical markers of both cerebral metabolic and vascular dysfunction 1 h after HI predicted injury severity and subsequent outcome in a pre-clinical model. IMPACT: This study highlights the possibility of using non-invasive optical biomarkers for early assessment of injury severity following neonatal encephalopathy, relating to the outcome. Continuous cot-side monitoring of these optical markers can be useful for disease stratification in the clinical population and for identifying infants who might benefit from future adjunct neuroprotective therapies beyond cooling.

A multiparametric alternative to short inversion-time inversion recovery for imaging inflammation: T2water and fat fraction measurement using chemical shift-encoded turbo spin-echo MRI.

PURPOSE: Short-inversion-time inversion-recovery MRI is used widely for imaging bone and soft-tissue inflammation in rheumatic inflammatory diseases, but there is no widely available quantitative equivalent of this sequence. This limits our ability to objectively assess inflammation and distinguish it from other processes. To address this, we investigate the use of the widely available Dixon turbo spin echo (TSE Dixon) sequence as a practical approach to simultaneous water-specific T2 (T2water ) and fat fraction (FF) measurement. METHODS: We use a series of TSE Dixon acquisitions with varying effective TEs (TEeff ) to quantify T2water and FF. The validity of this approach is assessed in a series of phantom and in vivo experiments, with reference values provided by Carr-Purcell-Meiboom-Gill acquisitions, MRS, and phantoms. The effect of inflammation on parameter values is evaluated in patients with spondyloarthritis. RESULTS: The T2water estimates obtained from TSE Dixon were accurate compared with the reference values from Carr-Purcell-Meiboom-Gill and spectroscopy in both fat-free environments and in the presence of fat. FF measurements with T2water correction from TSE Dixon were accurate from 0% to 60% FF and were not confounded by T2water variations. In vivo imaging produced good quality images that were artifact free, produced plausible T2 values, separating and quantifying the effect of inflammation on T2water and FF. CONCLUSION: The T2water and FF measurements based on TSE Dixon with effective TE increments are accurate over a range of T2 and FF values and could provide a widely available quantitative alternative to the short-inversion-time inversion-recovery sequence for imaging inflamed tissue.

Volume of hyperintense inflammation (VHI): A quantitative imaging biomarker of inflammation load in spondyloarthritis, enabled by human-machine cooperation.

Qualitative visual assessment of MRI scans is a key mechanism by which inflammation is assessed in clinical practice. For example, in axial spondyloarthritis (axSpA), visual assessment focuses on the identification of regions with increased signal in the bone marrow, known as bone marrow oedema (BMO), on water-sensitive images. The identification of BMO has an important role in the diagnosis, quantification and monitoring of disease in axSpA. However, BMO evaluation depends heavily on the experience and expertise of the image reader, creating substantial imprecision. Deep learning-based segmentation is a natural approach to addressing this imprecision, but purely automated solutions require large training sets that are not currently available, and deep learning solutions with limited data may not be sufficiently trustworthy for use in clinical practice. To address this, we propose a workflow for inflammation segmentation incorporating both deep learning and human input. With this 'human-machine cooperation' workflow, a preliminary segmentation is generated automatically by deep learning; a human reader then 'cleans' the segmentation by removing extraneous segmented voxels. The final cleaned segmentation defines the volume of hyperintense inflammation (VHI), which is proposed as a quantitative imaging biomarker (QIB) of inflammation load in axSpA. We implemented and evaluated the proposed human-machine workflow in a cohort of 29 patients with axSpA who had undergone prospective MRI scans before and after starting biologic therapy. The performance of the workflow was compared against purely visual assessment in terms of inter-observer/inter-method segmentation overlap, inter-observer agreement and assessment of response to biologic therapy. The human-machine workflow showed superior inter-observer segmentation overlap than purely manual segmentation (Dice score 0.84 versus 0.56). VHI measurements produced by the workflow showed similar or better inter-observer agreement than visual scoring, with similar response assessments. We conclude that the proposed human-machine workflow offers a mechanism to improve the consistency of inflammation assessment, and that VHI could be a valuable QIB of inflammation load in axSpA, as well as offering an exemplar of human-machine cooperation more broadly.

Quantitative magnetic resonance imaging (qMRI) in axial spondyloarthritis.

Imaging, and particularly MRI, plays a crucial role in the assessment of inflammation in rheumatic disease, and forms a core component of the diagnostic pathway in axial spondyloarthritis. However, conventional imaging techniques are limited by image contrast being non-specific to inflammation and a reliance on subjective, qualitative reader interpretation. Quantitative MRI methods offer scope to address these limitations and improve our ability to accurately and precisely detect and characterise inflammation, potentially facilitating a more personalised approach to management. Here, we review quantitative MRI methods and emerging quantitative imaging biomarkers for imaging inflammation in axial spondyloarthritis. We discuss the potential benefits as well as the practical considerations that must be addressed in the movement toward clinical translation of quantitative imaging biomarkers.

MRI and the control of electromagnetic fields at work regulations 2016 - professional body guidance.

The Control of Electromagnetic Fields at Work Regulations (2016) implement the requirements of the EU Physical Agents (Electromagnetic Fields) Directive 2013 into UK Law. These regulations prohibit exposure of employees to electromagnetic fields above defined exposure limit values (ELVs). However, for MRI work activities, there is an exemption from this requirement provided that exposures are reduced to a level that is as low as is reasonably practicable. There are additional requirements for an adequate risk assessment, provision for staff training and monitoring of any health effects.This document provides specific guidance on achieving compliance with the regulations in the MRI setting. Consideration of what level of exposure is 'reasonable' is key to the proper application of these regulations. The ELVs, as defined in the regulations, are presented in terms of their relevance to exposures in the MRI-setting, what the direct and indirect effects of exposures are likely to be and what reasonable control measures can be put in place. Worked examples provide a step-by-step guide to achieving compliance with the regulations.For typical MRI working practices, it is unlikely that any permanent health effects will be experienced. Indeed, any effects that are experienced are likely to be transient and have no long-term consequences. Control measures to minimise the risks to workers in the MRI environment should already be in place in well-run units and there should be no need to implement additional control measures for exposures above the ELVs.

Quantification of Prostate Cancer Metabolism Using 3D Multiecho bSSFP and Hyperpolarized [1-13 C] Pyruvate: Metabolism Differs Between Tumors of the Same Gleason Grade.

BACKGROUND: Three-dimensional (3D) multiecho balanced steady-state free precession (ME-bSSFP) has previously been demonstrated in preclinical hyperpolarized (HP) 13 C-MRI in vivo experiments, and it may be suitable for clinical metabolic imaging of prostate cancer (PCa). PURPOSE: To validate a signal simulation framework for the use of sequence parameter optimization. To demonstrate the feasibility of ME-bSSFP for HP 13 C-MRI in patients. To evaluate the metabolism in PCa measured by ME-bSSFP. STUDY TYPE: Retrospective single-center cohort study. PHANTOMS/POPULATION: Phantoms containing aqueous solutions of [1-13 C] lactate (2.3 M) and [13 C] urea (8 M). Eight patients (mean age 67 ± 6 years) with biopsy-confirmed Gleason 3 + 4 (n = 7) and 4 + 3 (n = 1) PCa. FIELD STRENGTH/SEQUENCES: 1 H MRI at 3 T with T2 -weighted turbo spin-echo sequence used for spatial localization and spoiled dual gradient-echo sequence used for B0 -field measurement. ME-bSSFP sequence for 13 C MR spectroscopic imaging with retrospective multipoint IDEAL metabolite separation. ASSESSMENT: The primary endpoint was the analysis of pyruvate-to-lactate conversion in PCa and healthy prostate regions of interest (ROIs) using model-free area under the curve (AUC) ratios and a one-directional kinetic model (kP ). The secondary objectives were to investigate the correlation between simulated and experimental ME-bSSFP metabolite signals for HP 13 C-MRI parameter optimization. STATISTICAL TESTS: Pearson correlation coefficients with 95% confidence intervals and paired t-tests. The level of statistical significance was set at P < 0.05. RESULTS: Strong correlations between simulated and empirical ME-bSSFP signals were found (r > 0.96). Therefore, the simulation framework was used for sequence optimization. Whole prostate metabolic HP 13 C-MRI, observing the conversion of pyruvate into lactate, with a temporal resolution of 6 seconds was demonstrated using ME-bSSFP. Both assessed metrics resulted in significant differences between PCa (mean ± SD) (AUC = 0.33 ± 012, kP  = 0.038 ± 0.014) and healthy (AUC = 0.15 ± 0.10, kP  = 0.011 ± 0.007) ROIs. DATA CONCLUSION: Metabolic HP 13 C-MRI in the prostate using ME-bSSFP allows for differentiation between aggressive PCa and healthy tissue. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 1.

MAGORINO: Magnitude-only fat fraction and R* 2 estimation with Rician noise modeling.

PURPOSE: Magnitude-based fitting of chemical shift-encoded data enables proton density fat fraction (PDFF) and R 2 * $$ {R}_2^{\ast } $$ estimation where complex-based methods fail or when phase data are inaccessible or unreliable. However, traditional magnitude-based fitting algorithms do not account for Rician noise, creating a source of bias. To address these issues, we propose an algorithm for magnitude-only PDFF and R 2 * $$ {R}_2^{\ast } $$ estimation with Rician noise modeling (MAGORINO). METHODS: Simulations of multi-echo gradient-echo signal intensities are used to investigate the performance and behavior of MAGORINO over the space of clinically plausible PDFF, R 2 * $$ {R}_2^{\ast } $$ , and SNR values. Fitting performance is assessed through detailed simulation, including likelihood function visualization, and in a multisite, multivendor, and multi-field-strength phantom data set and in vivo. RESULTS: Simulations show that Rician noise-based magnitude fitting outperforms existing Gaussian noise-based fitting and reveals two key mechanisms underpinning the observed improvement. First, the likelihood functions exhibit two local optima; Rician noise modeling increases the chance that the global optimum corresponds to the ground truth. Second, when the global optimum corresponds to ground truth for both noise models, the optimum from Rician noise modeling is closer to ground truth. Multisite phantom experiments show good agreement of MAGORINO PDFF with reference values, and in vivo experiments replicate the performance benefits observed in simulation. CONCLUSION: The MAGORINO algorithm reduces Rician noise-related bias in PDFF and R 2 * $$ {R}_2^{\ast } $$ estimation, thus addressing a key limitation of existing magnitude-only fitting methods. Our results offer insight into the importance of the noise model for selecting the correct optimum when multiple plausible optima exist.

Brain temperature monitoring in newborn infants: Current methodologies and prospects.

Brain tissue temperature is a dynamic balance between heat generation from metabolism, passive loss of energy to the environment, and thermoregulatory processes such as perfusion. Perinatal brain injuries, particularly neonatal encephalopathy, and seizures, have a significant impact on the metabolic and haemodynamic state of the developing brain, and thereby likely induce changes in brain temperature. In healthy newborn brains, brain temperature is higher than the core temperature. Magnetic resonance spectroscopy (MRS) has been used as a viable, non-invasive tool to measure temperature in the newborn brain with a reported accuracy of up to 0.2 degrees Celcius and a precision of 0.3 degrees Celcius. This measurement is based on the separation of chemical shifts between the temperature-sensitive water peaks and temperature-insensitive singlet metabolite peaks. MRS thermometry requires transport to an MRI scanner and a lengthy single-point measurement. Optical monitoring, using near infrared spectroscopy (NIRS), offers an alternative which overcomes this limitation in its ability to monitor newborn brain tissue temperature continuously at the cot side in real-time. Near infrared spectroscopy uses linear temperature-dependent changes in water absorption spectra in the near infrared range to estimate the tissue temperature. This review focuses on the currently available methodologies and their viability for accurate measurement, the potential benefits of monitoring newborn brain temperature in the neonatal intensive care unit, and the important challenges that still need to be addressed.

Protocol for the Birth Asphyxia in African Newborns (Baby BRAiN) Study: a Neonatal Encephalopathy Feasibility Cohort Study.

BACKGROUND: Neonatal encephalopathy (NE) is a leading cause of child mortality worldwide and contributes substantially to stillbirths and long-term disability. Ninety-nine percent of deaths from NE occur in low-and-middle-income countries (LMICs). Whilst therapeutic hypothermia significantly improves outcomes in high-income countries, its safety and effectiveness in diverse LMIC contexts remains debated. Important differences in the aetiology, nature and timing of neonatal brain injury likely influence the effectiveness of postnatal interventions, including therapeutic hypothermia. METHODS: This is a prospective pilot feasibility cohort study of neonates with NE conducted at Kawempe National Referral Hospital, Kampala, Uganda. Neurological investigations include continuous video electroencephalography (EEG) (days 1-4), serial cranial ultrasound imaging, and neonatal brain Magnetic Resonance Imaging and Spectroscopy (MRI/ MRS) (day 10-14). Neurodevelopmental follow-up will be continued to 18-24 months of age including Prechtl's Assessment of General Movements, Bayley Scales of Infant Development, and a formal scored neurological examination. The primary outcome will be death and moderate-severe neurodevelopmental impairment at 18-24 months. Findings will be used to inform explorative science and larger trials, aiming to develop urgently needed neuroprotective and neurorestorative interventions for NE applicable for use in diverse settings. DISCUSSION: The primary aims of the study are to assess the feasibility of establishing a facility-based cohort of children with NE in Uganda, to enhance our understanding of NE in a low-resource sub-Saharan African setting and provide infrastructure to conduct high-quality research on neuroprotective/ neurorestorative strategies to reduce death and disability from NE. Specific objectives are to establish a NE cohort, in order to 1) investigate the clinical course, aetiology, nature and timing of perinatal brain injury; 2) describe electrographic activity and quantify seizure burden and the relationship with adverse outcomes, and; 3) develop capacity for neonatal brain MRI/S and examine associations with early neurodevelopmental outcomes.

A reproducible dynamic phantom for sequence testing in hyperpolarised 13C-magnetic resonance.

OBJECTIVE: To develop a phantom system which can be integrated with an automated injection system, eliminating the experimental variability that arises with manual injection; for the purposes of pulse sequence testing and metric derivation in hyperpolarised 13C-MR. METHODS: The custom dynamic phantom was machined from Ultem and filled with a nicotinamide adenine dinucleotide and lactate dehydrogenase mixture dissolved in phosphate buffered saline. Hyperpolarised [1-13C]-pyruvate was then injected into the phantom (n = 8) via an automated syringe pump and the conversion of pyruvate to lactate monitored through a 13C imaging sequence. RESULTS: The phantom showed low coefficient of variation for the lactate to pyruvate peak signal heights (11.6%) and dynamic area-under curve ratios (11.0%). The variance for the lactate dehydrogenase enzyme rate constant (kP) was also seen to be low at 15.6%. CONCLUSION: The dynamic phantom demonstrates high reproducibility for quantification of 13C-hyperpolarised MR-derived metrics. Establishing such a phantom is needed to facilitate development of hyperpolarsed 13C-MR pulse sequenced; and moreover, to enable multisite hyperpolarised 13C-MR clinical trials where assessment of metric variability across sites is critical. ADVANCES IN KNOWLEDGE: The dynamic phantom developed during the course of this study will be a useful tool in testing new pulse sequences and standardisation in future hyperpolarised work.

Hypothermia is not therapeutic in a neonatal piglet model of inflammation-sensitized hypoxia-ischemia.

BACKGROUND: Perinatal inflammation combined with hypoxia-ischemia (HI) exacerbates injury in the developing brain. Therapeutic hypothermia (HT) is standard care for neonatal encephalopathy; however, its benefit in inflammation-sensitized HI (IS-HI) is unknown. METHODS: Twelve newborn piglets received a 2 µg/kg bolus and 1 µg/kg/h infusion over 52 h of Escherichia coli lipopolysaccharide (LPS). HI was induced 4 h after LPS bolus. After HI, piglets were randomized to HT (33.5 °C 1-25 h after HI, n = 6) or normothermia (NT, n = 6). Amplitude-integrated electroencephalogram (aEEG) was recorded and magnetic resonance spectroscopy (MRS) was acquired at 24 and 48 h. At 48 h, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive brain cell death, microglial activation/proliferation, astrogliosis, and cleaved caspase-3 (CC3) were quantified. Hematology and plasma cytokines were serially measured. RESULTS: Two HT piglets died. aEEG recovery, thalamic and white matter MRS lactate/N-acetylaspartate, and TUNEL-positive cell death were similar between groups. HT increased microglial activation in the caudate, but had no other effect on glial activation/proliferation. HT reduced CC3 overall. HT suppressed platelet count and attenuated leukocytosis. Cytokine profile was unchanged by HT. CONCLUSIONS: We did not observe protection with HT in this piglet IS-HI model based on aEEG, MRS, and immunohistochemistry. Immunosuppressive effects of HT and countering neuroinflammation by LPS may contribute to the observed lack of HT efficacy. Other immunomodulatory strategies may be more effective in IS-HI. IMPACT: Acute infection/inflammation is known to exacerbate perinatal brain injury and can worsen the outcomes in neonatal encephalopathy. Therapeutic HT is the current standard of care for all infants with NE, but the benefit in infants with coinfection/inflammation is unknown. In a piglet model of inflammation (LPS)-sensitized HI, we observed no evidence of neuroprotection with cooling for 24 h, based on our primary outcome measures: aEEG, MRS Lac/NAA, and histological brain cell death. Additional neuroprotective agents, with beneficial immunomodulatory effects, require exploration in IS-HI models.

Cardiac-induced liver deformation as a measure of liver stiffness using dynamic imaging without magnetization tagging-preclinical proof-of-concept, clinical translation, reproducibility and feasibility in patients with cirrhosis.

PURPOSE: MR elastography and magnetization-tagging use liver stiffness (LS) measurements to diagnose fibrosis but require physical drivers, specialist sequences and post-processing. Here we evaluate non-rigid registration of dynamic two-dimensional cine MRI images to measure cardiac-induced liver deformation (LD) as a measure of LS by (i) assessing preclinical proof-of-concept, (ii) clinical reproducibility and inter-reader variability, (iii) the effects of hepatic hemodynamic changes and (iv) feasibility in patients with cirrhosis. METHODS: Sprague-Dawley rats (n = 21 bile duct ligated (BDL), n = 17 sham-operated controls) and fasted patients with liver cirrhosis (n = 11) and healthy volunteers (HVs, n = 10) underwent spoiled gradient-echo short-axis cardiac cine MRI studies at 9.4 T (rodents) and 3.0 T (humans). LD measurements were obtained from intrahepatic sub-cardiac regions-of-interest close to the diaphragmatic margin. One-week reproducibility and prandial stress induced hemodynamic changes were assessed in healthy volunteers. RESULTS: Normalized LD was higher in BDL (1.304 ± 0.062) compared with sham-operated rats (1.058 ± 0.045, P = 0.0031). HV seven-day reproducibility Bland-Altman (BA) limits-of-agreement (LoAs) were ± 0.028 a.u. and inter-reader variability BA LoAs were ± 0.030 a.u. Post-prandial LD increases were non-significant (+ 0.0083 ± 0.0076 a.u., P = 0.3028) and uncorrelated with PV flow changes (r = 0.42, p = 0.2219). LD measurements successfully obtained from all patients were not significantly higher in cirrhotics (0.102 ± 0.0099 a.u.) compared with HVs (0.080 ± 0.0063 a.u., P = 0.0847). CONCLUSION: Cardiac-induced LD is a conceptually reasonable approach from preclinical studies, measurements demonstrate good reproducibility and inter-reader variability, are less likely to be affected by hepatic hemodynamic changes and are feasible in patients with cirrhosis.

Multimodal Measurements of Brain Tissue Metabolism and Perfusion in a Neonatal Model of Hypoxic-Ischaemic Injury.

This is the first multimodal study of cerebral tissue metabolism and perfusion post-hypoxic-ischaemic (HI) brain injury using broadband near-infrared spectroscopy (bNIRS), diffuse correlation spectroscopy (DCS), positron emission tomography (PET) and magnetic resonance spectroscopy (MRS). In seven piglet preclinical models of neonatal HI, we measured cerebral tissue saturation (StO2), cerebral blood flow (CBF), cerebral oxygen metabolism (CMRO2), changes in the mitochondrial oxidation state of cytochrome c oxidase (oxCCO), cerebral glucose metabolism (CMRglc) and tissue biochemistry (Lac+Thr/tNAA). At baseline, the parameters measured in the piglets that experience HI (not controls) were 64 ± 6% StO2, 35 ± 11 ml/100 g/min CBF and 2.0 ± 0.4 µmol/100 g/min CMRO2. After HI, the parameters measured were 68 ± 6% StO2, 35 ± 6 ml/100 g/min CBF, 1.3 ± 0.1 µmol/100 g/min CMRO2, 0.4 ± 0.2 Lac+Thr/tNAA and 9.5 ± 2.0 CMRglc. This study demonstrates the capacity of a multimodal set-up to interrogate the pathophysiology of HIE using a combination of optical methods, MRS, and PET.

Melatonin and/or erythropoietin combined with hypothermia in a piglet model of perinatal asphyxia.

As therapeutic hypothermia is only partially protective for neonatal encephalopathy, safe and effective adjunct therapies are urgently needed. Melatonin and erythropoietin show promise as safe and effective neuroprotective therapies. We hypothesized that melatonin and erythropoietin individually augment 12-h hypothermia (double therapies) and hypothermia + melatonin + erythropoietin (triple therapy) leads to optimal brain protection. Following carotid artery occlusion and hypoxia, 49 male piglets (<48 h old) were randomized to: (i) hypothermia + vehicle (n = 12), (ii) hypothermia + melatonin (20 mg/kg over 2 h) (n = 12), (iii) hypothermia + erythropoietin (3000 U/kg bolus) (n = 13) or (iv) triple therapy (n = 12). Melatonin, erythropoietin or vehicle were given at 1, 24 and 48 h after hypoxia-ischaemia. Hypoxia-ischaemia severity was similar across groups. Therapeutic levels were achieved 3 hours after hypoxia-ischaemia for melatonin (15-30 mg/l) and within 30 min of erythropoietin administration (maximum concentration 10 000 mU/ml). Compared to hypothermia + vehicle, we observed faster amplitude-integrated EEG recovery from 25 to 30 h with hypothermia + melatonin (P = 0.02) and hypothermia + erythropoietin (P = 0.033) and from 55 to 60 h with triple therapy (P = 0.042). Magnetic resonance spectroscopy lactate/N-acetyl aspartate peak ratio was lower at 66 h in hypothermia + melatonin (P = 0.012) and triple therapy (P = 0.032). With hypothermia + melatonin, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelled-positive cells were reduced in sensorimotor cortex (P = 0.017) and oligodendrocyte transcription factor 2 labelled-positive counts increased in hippocampus (P = 0.014) and periventricular white matter (P = 0.039). There was no reduction in terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelled-positive cells with hypothermia + erythropoietin, but increased oligodendrocyte transcription factor 2 labelled-positive cells in 5 of 8 brain regions (P < 0.05). Overall, melatonin and erythropoietin were safe and effective adjunct therapies to hypothermia. Hypothermia + melatonin double therapy led to faster amplitude-integrated EEG recovery, amelioration of lactate/N-acetyl aspartate rise and reduction in terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelled-positive cells in the sensorimotor cortex. Hypothermia + erythropoietin double therapy was in association with EEG recovery and was most effective in promoting oligodendrocyte survival. Triple therapy provided no added benefit over the double therapies in this 72-h study. Melatonin and erythropoietin influenced cell death and oligodendrocyte survival differently, reflecting distinct neuroprotective mechanisms which may become more visible with longer-term studies. Staggering the administration of therapies with early melatonin and later erythropoietin (after hypothermia) may provide better protection; each therapy has complementary actions which may be time critical during the neurotoxic cascade after hypoxia-ischaemia.

Liver perfusion MRI in a rodent model of cirrhosis: Agreement with bulk-flow phase-contrast MRI and noninvasive evaluation of inflammation in chronic liver disease using flow-sensitive alternating inversion recovery arterial spin labelling and tissue T1.

Noninvasive measurements of liver perfusion and fibrosis in cirrhotic small animals can help develop treatments for haemodynamic complications of liver disease. Here, we measure liver perfusion in cirrhotic rodents using flow-sensitive alternating inversion recovery arterial spin labelling (FAIR ASL), evaluating agreement with previously validated caval subtraction phase-contrast magnetic resonance imaging (PCMRI) total liver blood flow (TLBF). Baseline differences in cirrhotic rodents and the haemodynamic effects of acute inflammation were investigated using FAIR ASL and tissue T1. Sprague-Dawley rats (nine bile duct ligated [BDL] and ten sham surgery controls) underwent baseline hepatic FAIR ASL with T1 measurement and caval subtraction PCMRI (with two-dimensional infra-/supra-hepatic inferior vena caval studies), induction of inflammation with intravenous lipopolysaccharide (LPS) and repeat liver FAIR ASL with T1 measurement after ~90 minutes. The mean difference between FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF was -51 ± 30 ml/min/100 g (Bland-Altman 95% limits-of-agreement ±258 ml/min/100 g). The FAIR ASL coefficient of variation was smaller than for caval subtraction PCMRI (29.3% vs 50.1%; P = .03). At baseline, FAIR ASL liver perfusion was lower in BDL rats (199 ± 32 ml/min/100 g vs sham 316 ± 24 ml/min/100 g; P = .01) but liver T1 was higher (BDL 1533 ± 50 vs sham 1256 ± 18 ms; P = .0004). Post-LPS FAIR ASL liver perfusion response differences were observed between sham/BDL rats (P = .02), approaching significance in sham (+78 ± 33 ml/min/100 g; P = .06) but not BDL rats (-49 ± 40 ml/min/100 g; P = .47). Post-LPS differences in liver tissue T1 were nonsignificant (P = .35). FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF agreement was modest, with significant baseline FAIR ASL liver perfusion and tissue T1 differences in rodents with advanced cirrhosis compared with controls. Following inflammatory stress, differences in hepatic perfusion response were detected between cirrhotic/control animals, but liver T1 was unaffected. Findings underline the potential of FAIR ASL in the assessment of vasoactive treatments for patients with chronic liver disease and inflammation.