ABSTRACT Background Dysferlin plays a key role in cell membrane repair; its absence or malfunction in patients with dysferlin‐deficient limb girdle muscular dystrophy leads to muscle fibre death. Muscle magnetic resonance (MR) imaging allows non‐invasive and repeatable measurements that can report on pathological changes observed in dysferlinopathy patients (DP). We aimed to demonstrate the feasibility of utilising volume‐localised 23Na spectroscopy as a novel approach to characterise muscle Na+ content and biexponential T2* at rest, and dynamically post‐exercise, in patients with dysferlinopathy and in matched healthy controls. Methods Adult DP and age and sex matched healthy volunteers (HV) were recruited and scanned on a 3 T clinical MR scanner. Following baseline scans, participants performed physiotherapist‐guided isometric dorsiflexion contractions until tibialis anterior (TA) muscle exhaustion. Dynamic volume‐localised sodium‐23 (23Na)‐ and proton (1H)‐MR scans were acquired serially for 35 min post‐exercise. MR data were analysed to determine TA lipid content, change in TA sodium content, biexponential sodium T2* properties and TA water 1H T2. Results Ten DP (mean age ± standard deviation [SD]: 38.0 ± 10.8 years; 80% female) and 10 HV (mean age ± SD: 38.9 ± 11.5 years) were scanned. Baseline muscle water 1H T2 and sodium concentration were significantly higher in DP compared to matched controls (1H T2 DP [SD] = 33.8 [2.7] ms, 1H T2 HV = 29.3 [1.1] ms, p < 0.001; [23Na]DP = 36.2 [11.4] mM, [23Na]HV = 19.6 [3.1] mM, p < 0.001). 1H T2 and sodium content in healthy controls showed significant post‐exercise elevation with a slower time‐to‐peak for sodium content compared to 1H T2. 1H T2 and sodium content change post‐exercise was highly variable in the DP group. Notably, 23Na dynamics in one DP with normal muscle fat fraction were similar to HV. Biexponential 23Na T2* was measured at baseline in HV (T2*slow = 13.4 [2.3] ms, T2*fast = 2.2 [1.3] ms), and DP (T2*slow = 14.0 [1.5] ms and T2*fast = 1.0 [0.5] m). Equivalent measurements post‐exercise revealed an increase in the fraction of the slow‐relaxing component in HV (p < 0.05), consistent with oedematous changes. Conclusions Assessment of TA muscle fat fraction, 1H T2, sodium content and sodium T2* relaxation properties revealed differences at baseline and in post‐exercise dynamics between patients with dysferlinopathy and matched controls. Post‐exercise 23Na recovery dynamics followed a well‐defined time course in HV. Heterogeneous alterations in sodium content and MR relaxation properties in DP may reflect altered ion homeostasis associated with chronic muscle damage.

Post-exercise carbohydrate intake is required to replenish endogenous glycogen stores. Although adequate carbohydrate consumption has been reported to restore muscle glycogen contents within 24 h of post-exercise recovery, the time required to replenish liver glycogen contents is less evident. Twelve well-trained male cyclists (age: 25 ± 5 years; V̇O2peak: 67 ± 5 ml/min/kg; Wmax: 5.8 ± 0.7 W/kg) participated in this trial. Ultra-high-field (UHF) 13C magnetic resonance spectroscopy (13C MRS) was applied to assess muscle and liver glycogen concentrations before and immediately after glycogen-depleting exercise on two test days. This was followed by 12 h of recovery during which participants remained fasted (CON) or consumed 10 g carbohydrate per kg body mass (BM) in the form of sucrose-containing beverages (1.2 g/kg BM/h over the first 6 h) and carbohydrate-rich meals (CHO). Muscle and liver glycogen concentrations were again assessed at 6 and 12 h into recovery using 13C MRS. Furthermore muscle biopsies were collected to assess muscle glycogen concentrations using biochemical analysis. Exercise significantly reduced muscle (from 159 ± 32 to 56 ± 19 mmol/l; -64%) and liver (from 166 ± 40 to 110 ± 44 mmol/l; -34%) glycogen concentrations (P < 0.05), with no significant differences between test days (P > 0.05). In the absence of carbohydrate intake (CON) muscle and liver glycogen concentrations remained unchanged during recovery. After carbohydrate intake (CHO) muscle glycogen concentrations increased from 56 ± 19 to 88 ± 16 and 110 ± 19 mmol/l (or from 269 ± 90 to 418 ± 78 and 523 ± 92 in mmol/kg dry mass), after 0, 6 and 12 h of recovery, respectively, remaining well below pre-exercise values (i.e. 55% of pre-exercise at 6 h and 69% at 12 h). Liver glycogen concentrations increased from 110 ± 44 to 236 ± 39 and 258 ± 40 mmol/l, after 0, 6 and 12 h of recovery, respectively, exceeding pre-exercise values within 6 h of recovery (i.e. 142% of pre-exercise). A very strong correlation (r = 0.89, P < 0.001), good agreement (ICC: 0.87) and low bias (4.1 ± 23.7 mmol/l) were observed when comparing muscle glycogen concentrations assessed using 13C MRS and biochemical analyses. Sucrose ingestion (1.2 g/kg BM/h) fully restored liver glycogen concentrations well within 6 h of post-exercise recovery. Ingesting large amounts of carbohydrate (10 g/kg BM) did not allow muscle glycogen stores to be replenished within 12 h of post-exercise recovery. KEY POINTS: Carbohydrate ingestion is required to replenish muscle and liver glycogen stores after a strenuous bout of exercise. Carbon-13 magnetic resonance spectroscopy at ultra-high-field (7T) allows non-invasive measurement of both muscle and liver glycogen contents before and after exercise, and at 6 and 12 h of recovery with (CHO) and without (CON) carbohydrate ingestion (10 g per kg body mass). Exercise strongly reduces glycogen contents of both muscle and liver tissue. Without carbohydrate ingestion muscle and liver glycogen levels remain depleted. After ingestion of large amounts of carbohydrate both muscle and liver glycogen contents increase rapidly, with liver glycogen stores being fully repleted within 6 h. Ample carbohydrate ingestion allows rapid replenishment of liver but not muscle glycogen stores within 6 and 12 h of post-exercise recovery.

A carbohydrate-rich breakfast is commonly consumed by cyclists to compensate for an overnight decline in liver glycogen content and, as such, to maximize liver glycogen stores in the hours before exercise. However, the extent to which liver glycogen content increases in response to the intake of a carbohydrate-rich breakfast in well-trained cyclists remains unexplored. Twelve well-trained male cyclists (age: 25 ± 5 yr; V̇o2peak: 67 ± 5 mL·min-1·kg-1; Wmax: 5.8 ± 0.7 W·kg-1) participated in this trial. Carbon-13 magnetic resonance spectroscopy (13C-MRS) at 7 T and magnetic resonance imaging (MRI) at 3 T were applied to assess muscle and liver glycogen concentrations and volume, respectively, before and 3 h after ingesting a carbohydrate-rich breakfast providing 3 g carbohydrates per kg body mass. Following breakfast ingestion, muscle glycogen concentrations, muscle volumes, and total muscle glycogen content did not change (P > 0.05). Liver glycogen concentrations increased by ∼10% (from 164 ± 30 to 180 ± 33 mmol/L; P = 0.036), whereas liver volumes decreased by ∼6% (from 1.96 ± 0.28 to 1.84 ± 0.27 L; P < 0.001) in the 3 h following breakfast ingestion. Consequently, no net change in overall liver glycogen content was observed following breakfast ingestion (from 53 ± 15 to 54 ± 13 g; P = 0.516). Ingesting a carbohydrate-rich breakfast (providing 3 g carbohydrates per kg body mass) does not elevate liver or muscle glycogen content during the subsequent 3-h postprandial period.NEW & NOTEWORTHY This is the first study to simultaneously assess both muscle and liver glycogen content following ingestion of a practical carbohydrate-rich breakfast in well-trained cyclists. No changes were observed in muscle glycogen concentrations or content. Liver glycogen concentrations increased postprandially, but liver glycogen content remained unchanged due to a concurrent decline in liver volume. These findings highlight the importance of accounting for liver volume changes when interpreting postprandial liver glycogen storage responses.

Background By the time chronic lung allograft dysfunction (CLAD), with its main phenotypes bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS), is diagnosed by pulmonary function testing, irreversible damage to the lung allograft may already have occurred. Dynamic 19F-MRI of inhaled perfluoropropane may detect subtle changes in regional lung ventilation and provides a quantitative measure of regional lung function. We assessed feasibility of detecting regional ventilation dysfunction due to CLAD in lung transplant recipients. Methods Dynamic 19F-MRI was performed in ten lung transplant recipients, four without CLAD and six with CLAD (5 BOS, 1 RAS). Gas wash-in and washout dynamics were assessed and regional lung clearance index (RLCI) provided a quantitative metric of regional lung ventilation. Results BOS patients had substantially greater variation in regional ventilation compared with stable patients, with more regions of reduced ventilation, especially in the periphery. Tracer washout was homogeneous and rapid in stable patients but highly heterogeneous in CLAD. CLAD patients exhibited significant difference in RLCI between central and peripheral lung regions (p = 0.0016) and a wider interquartile range of RLCI for wash-in compared with stable patients (no CLAD 4.1, BOS 10.5, p = 0.036). FEV1 (% of baseline) negatively correlated with ventilation during wash-in, most strongly for the periphery (r = −0.844, p = 0.0021). Conclusions Dynamic 19F-MRI identified quantifiable differences in regional ventilation in lung transplant recipients with and without CLAD and was well tolerated. Larger longitudinal studies using this approach will determine if early detection of changes in regional ventilation in lung transplant patients allows earlier CLAD detection.

Background: People with bipolar disorder (BD) tend to show widespread cognitive impairment compared to healthy controls. Impairments in processing speed (PS), attention, and executive function (EF) may represent 'core' impairments that have a role in wider cognitive dysfunction. Cognitive impairments appear to relate to structural brain abnormalities in BD, but whether core deficits are related to particular brain regions is unclear and much of the research on brain-cognition associations is limited by univariate analysis and small samples. Methods: Euthymic BD patients (n=56) and matched healthy controls (n=26) underwent T1-weighted MRI scans and completed neuropsychological tests of PS, attention, and EF. We utilised public datasets to develop a normative model of cortical thickness (n=5,977) to generate robust estimations of cortical abnormalities in patients. Canonical correlation analysis was used to assess multivariate brain-cognition associations in BD, controlling for age, sex, and premorbid IQ. Results: BD showed impairments on tests of PS, attention, and EF, and abnormal cortical thickness in several brain regions compared to healthy controls. Impairments in tests of PS and EF were most strongly associated with cortical thickness in left inferior temporal, right entorhinal, and right temporal pole areas. Conclusion: Impairments in PS, attention, and EF can be observed in euthymic BD and may be related to abnormal cortical thickness in temporal regions. Future research should continue to leverage multivariate methods to examine complex brain-cognition associations in BD. Future research may benefit from exploring covariance between traditional brain structural morphological metrics such as cortical thickness, cortical volume, and surface area.

Pompe disease is a rare genetic disorder resulting from a deficiency of the enzyme alpha-glucosidase. Late onset Pompe patients (LOPD) develop slowly progressive muscle weakness affecting axial and proximal muscles of the limbs as well as respiratory muscles. Enzymatic Replacement Therapy (ERT) is the standard of care for LOPD patients, having a role in reducing glycogen levels in skeletal muscle. However, patients treated with ERT continue to progress and therefore new therapeutic strategies trying to reduce glycogen levels in muscle are being tested. Therefore, it is very relevant to identify a non-invasive method to measure muscle glycogen that could be easily implemented in clinical sites running clinical trials with these new drugs. We have tested carbon (C13) spectroscopy in a clinical 3 Tesla MRI scanner in patients with LOPD. We have designed a coil to capture the signal from carbon and process it using a customized software pipeline. We analysed the presence of glycogen in the Vastus lateralis in the Semitendinosus. In parallel we obtained Dixon images to study fat fraction (FF), and water T2 images, to study the presence of oedema. Clinical data and muscle function tests including time to walk 10 meters, NSAD and handheld dynamometry were obtained from all participants. We included a total of 10 patients with genetically confirmed LOPD and 9 age and gender-matched controls. Most of the LODP patients were in early stages of disease progression, all able to walk without assistance (median rPACT 30 (21-36) and median NSAD 47.5 (34-50.7). We identified a significant increase in FF in the Adductor magnus muscle (26.1% vs 5.2%, p=0.04) in all LOPD patients compared to controls that progressed over a one-year period. Water T2 was also increased in this muscle, but we did not identify changes over time. We were able to identify glycogen elevation in the Vastus lateralis and Semitendinosus of patients and controls, although we only observed significant differences in the Semitendinosus muscle in LOPD compared to controls, with a significant increase in 181% in glycogen content. We did not identify any correlation between glycogen content and FF or water T2 time. Muscle function tests correlated well with mean FF of the thighs, but we did not identify any correlation between muscle function and glycogen content. There were no significant differences in glycogen content in the muscles between ERT treated (n=6) and non-treated LOPD patients (n=4). Our results confirm that carbon spectroscopy is a useful tool to identify glycogen in the skeletal muscle of patients with LOPD and can be implemented in conventional 3 Tesla MRIs in non-specialized imaging centres or hospitals. Our data suggest that glycogen accumulates more in posterior muscles of the thigh than in anterior ones. Glycogen does not seem to correlate with other structural abnormalities nor muscle function in patients with LOPD.

Dysferlin plays a key role in cell membrane repair, and its absence or malfunction in patients with dysferlin-deficient limb girdle muscular dystrophy leads to muscle fibre death. Muscle magnetic resonance imaging (MRI) allows non-invasive and repeatable measurements that report on pathological changes observed in dysferlinopathy patients (DP) that lead to muscle dysfunction. We have employed a standardised leg exercise protocol and dynamic 1H- and 23Na-MR imaging and spectroscopy methods to quantify the impact of dysferlin-deficiency on muscle sodium homeostasis. Ten adult DP and 10 age and sex matched healthy volunteers (HV) were recruited and scanned by 23Na and 1H MR imaging and spectroscopy on a 3T clinical MR scanner. Participants performed physiotherapist-guided isometric dorsiflexion contractions to achieve tibialis anterior (TA) muscle exhaustion. Dynamic volume-localised 23Na- and 1H-MR spectroscopy scans were acquired serially for 35 minutes post-exercise. MR data were analysed to determine TA lipid content and the change in TA sodium content, sodium T2* relaxation properties, and TA water 1H T2 relaxation properties. Biexponential analysis of 23Na T2* data was performed to assess dynamic change in the fraction of fast- vs slow-relaxing 23Na. Baseline muscle water 1H T2 and sodium content were significantly higher in DP compared to matched controls. 1H T2 and sodium content dynamics in healthy controls showed post-exercise elevation with slower time-to-peak for sodium content compared to 1H T2. Magnitude of 1H T2 and sodium content post-exercise dynamic change was highly variable in the DP group. Notably, 23Na dynamics in a DP with normal muscle fat fraction were similar to that of the HV group. Biexponential analysis of 23Na T2* showed a post-exercise increase in the slow-relaxing component, consistent with oedematous changes. We have implemented volume-localised 23Na MR spectroscopy for measurement of tissue sodium dynamics with high temporal resolution. Assessment of TA muscle fat fraction, 1H T2, sodium content and sodium T2* relaxation properties revealed differences at baseline and differences in post-exercise dynamics between patients with dysferlinopathy and matched controls. Alterations in sodium content and in post-exercise sodium content and relaxation dynamics in DP may reflect altered ion homeostasis that worsens as chronic muscle damage increases.

Background Pulmonary function tests are central to diagnosis and monitoring of respiratory diseases but do not provide information on regional lung function heterogeneity. Fluorine 19 (19F) MRI of inhaled perfluoropropane permits quantitative and spatially localized assessment of pulmonary ventilation properties without tracer gas hyperpolarization. Purpose To assess regional lung ventilation properties using 19F MRI of inhaled perfluoropropane in participants with asthma, participants with chronic obstructive pulmonary disease (COPD), and healthy participants, including quantitative evaluation of bronchodilator response in participants with respiratory disease. Materials and Methods This prospective, dual-center study included participants with asthma or COPD from July 2019 to September 2022 and healthy participants from May 2018 to June 2019. Participants underwent conventional spirometry, proton MRI, and 19F MRI following inhalation of a 79% perfluoropropane and 21% oxygen gas mixture. Three-dimensional 19F MRI scans were acquired during a single breath hold. For participants with asthma or COPD, spirometric and MRI measurements were repeated following administration of nebulized salbutamol. Ventilation defect percentage (VDP) was calculated from perfluoropropane distribution. Linear mixed-effects models were used to assess differences in VDP between participant groups and before and after bronchodilator administration. Results Thirty-five participants with asthma (mean age, 50 years ± 18 [SD]; 21 male participants), 21 participants with COPD (mean age, 69 years ± 6; 14 male participants), and 38 healthy participants (mean age, 41 years ± 11; 20 male participants) were evaluated. 19F MRI-derived VDP was elevated in participants with COPD (geometric mean, 27.2%) and participants with asthma (geometric mean, 8.3%) compared with healthy participants (geometric mean, 1.8%; geometric mean ratio, 15.2 [95% CI: 11.1, 20.6] for COPD and 4.6 [95% CI: 3.2, 6.6] for asthma; P < .001 for both). After bronchodilator administration, VDP was reduced by 33% in participants with asthma (from 8.3% to 5.6%) and 14% in participants with COPD (from 27.2% to 23.3%; P < .001 for both). Conclusion 19F MRI of inhaled perfluoropropane was sensitive to changes in regional ventilation properties associated with lung disease and enabled quantification of changes following bronchodilator therapy. Published under a CC BY-NC-ND 4.0 license. Supplemental material is available for this article. See also the editorial by Unger in this issue.

Background: Lithium is an effective mood stabiliser, but its mechanism of action is incompletely defined. Even at very low doses, lithium may have neuroprotective effects, but it is not clear if these relate to brain lithium concentration in vivo. We have developed magnetic resonance imaging ( 7 Li-MRI) methods to detect lithium in the brain following supplementation at a very low dose. Methods: Lithium orotate supplements were taken by nine healthy adult male subjects (5 mg daily) for up to 28 days, providing 2 -7 % of the lithium content of a typical therapeutic lithium carbonate dose. One-dimensional 7 Li-images were acquired on a 3.0 T MRI scanner. All subjects were scanned on day 14 or 28; seven were scanned on both, one at baseline and one after 7 -days washout. Results: 7 Li-MR signal amplitude was broadly stable between days 14 and 28. Two subjects had notably higher 7 Li-signal intensities (approximately 2 -4 x) compared to other study participants. Limitations: Lithium adherence was self -reported by all participants without formal validation. The coarse spatial resolution necessary for detection of low concentrations of 7 Li exhibits imperfect spatial separation of signal from adjacent pixels. Conclusions: 7 Li-MRI performed using a clinical 3T scanner demonstrated detection of lithium in the brain at very low concentration, in the range of approximately 10 -60 mM. The methods are suited to studies assessing low dose lithium administration in psychiatric and neurodegenerative disorders, and permit the comparison of different lithium salt preparations at a time of emerging interest in the field.

Tolerogenic dendritic cell (tolDC) therapies aim to restore self-tolerance in patients suffering from autoimmune diseases. Phase 1 clinical trials with tolDC have shown the feasibility and safety of this approach, but have also highlighted a lack of understanding of their distribution in vivo. Fluorine-19 magnetic resonance imaging (19F-MRI) promises an attractive cell tracking method because it allows for detection of 19F-labelled cells in a non-invasive and longitudinal manner. Here, we tested the suitability of nanoparticles containing 19F (19F-NP) for labelling of therapeutic human tolDC for detection by 19F-MRI. We found that tolDC readily endocytosed 19F-NP with acceptable effects on cell viability and yield. The MRI signal-to-noise ratios obtained are more than sufficient for detection of the administered tolDC dose (10 million cells) at the injection site in vivo, depending on the tissue depth and the rate of cell dispersal. Importantly, 19F-NP labelling did not revert tolDC into immunogenic DC, as confirmed by their low expression of typical mature DC surface markers (CD83, CD86), low secretion of pro-inflammatory IL-12p70, and low capacity to induce IFN-γ in allogeneic CD4+ T cells. In addition, the capacity of tolDC to secrete anti-inflammatory IL-10 was not diminished by 19F-NP labelling. We conclude that 19F-NP is a suitable imaging agent for tolDC. With currently available technologies, this imaging approach does not yet approach the sensitivity required to detect small numbers of migrating cells, but could have important utility for determining the accuracy of injecting tolDC into the desired target tissue and their efflux rate.

Background: COPD and bronchiectasis are heterogenous diseases; spirometry rarely identifies the site of pathology, while lung structure assessed by CT may poorly correlate with functional severity. Aim: To evaluate the utility of 19F-MRI of inhaled perfluoropropane (PFP) for regional functional assessment of pulmonary ventilation in a patient with COPD and mild bronchiectasis. Methods: 19F-MR ventilation images were acquired during static (breath-hold) and dynamic imaging (multiple wash-in breaths), using a 79% PFP/21% O2 gas mixture. Images were segmented to calculate the ventilation defect percentage (VDP) and co-registered with CT images previously segmented for percentage low-attenuation (PLA) regions. Regions of ventilation defect were compared using the Dice similarity coefficient, and with spirometry. Results: Patient images and spirometric values are shown in Figure 1. VDP (derived from 19F-MRI) was 43.3%; PLA (derived from CT) was 21.7%; overlap=38%. The flow-volume loop showed an obstructive pattern typical of airways collapse. Conclusion: Regions of ventilation impairment were revealed by 19F-MRI where only mild bronchiectasis was reported on CT, highlighting the potential to provide important information regarding lung function that is not apparent on CT or spirometry alone. This technique could be beneficial in planning individualised patient treatments, such as cancer treatments or lung volume reduction in patients with COPD.