MRI of EMS-controlled involuntary muscle contraction is feasible and allows offline calculation of velocity, strain and strain rate maps, which appear to depend significantly on the stimulation current used. Magn Reson Med 77:664-672, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Objectives To determine the prevalence of organ impairment in long COVID patients at 6 and 12 months after initial symptoms and to explore links to clinical presentation. Design Prospective cohort study. Participants Individuals. Methods In individuals recovered from acute COVID-19, we assessed symptoms, health status, and multi-organ tissue characterisation and function. Setting Two non-acute healthcare settings (Oxford and London). Physiological and biochemical investigations were performed at baseline on all individuals, and those with organ impairment were reassessed. Main outcome measures Primary outcome was prevalence of single- and multi-organ impairment at 6 and 12 months post COVID-19. Results A total of 536 individuals (mean age 45 years, 73% female, 89% white, 32% healthcare workers, 13% acute COVID-19 hospitalisation) completed baseline assessment (median: 6 months post COVID-19); 331 (62%) with organ impairment or incidental findings had follow-up, with reduced symptom burden from baseline (median number of symptoms 10 and 3, at 6 and 12 months, respectively). Extreme breathlessness (38% and 30%), cognitive dysfunction (48% and 38%) and poor health-related quality of life (EQ-5D-5L < 0.7; 57% and 45%) were common at 6 and 12 months, and associated with female gender, younger age and single-organ impairment. Single- and multi-organ impairment were present in 69% and 23% at baseline, persisting in 59% and 27% at follow-up, respectively. Conclusions Organ impairment persisted in 59% of 331 individuals followed up at 1 year post COVID-19, with implications for symptoms, quality of life and longer-term health, signalling the need for prevention and integrated care of long COVID. Trial Registration: ClinicalTrials.gov Identifier: NCT04369807

ACKNOWLEDGMENTS This is a pre-print of an article published in Magnetic Resonance Materials in Physics, Biology and Medicine.The final authenticated version is available online at: https://doi.org/10.1007/s10334-019-00787-7. ABSTRACT ObjectNeuromuscular electrical stimulation (NMES)-induced isometric contraction is feasible during MRI and can be combined with acquisition of volumetric dynamic MR data, in a synchronous and controlled way. Since NMES is a potent resource for rehabilitation, MRI synchronized with NMES presents a valuable validation tool. Our aim was to show how minimal NMES-induced muscle contraction characterization, as evaluated through phase contrast MRI, differs between senior and young volunteers. Materials and MethodsSimultaneous NMES of the quadriceps muscle and phase contrast imaging were applied at 3T to 11 senior (75±3 years) and 6 young volunteers (29±7 years). A current sufficient to induce muscle twitch without knee extension was applied to both groups. ResultsStrain vectors were extracted from the velocity fields and strain datasets were compared with non-parametric tests and descriptive statistics. Strain values were noticeably different between both groups at both current intensities and significant differences were observed in the regions of interest between the two electrodes. DiscussionIn conclusion, NMES-synchronized MRI could be successfully applied in senior volunteers with strain results clearly different from the younger volunteers. Also, differences within the senior group were detected both in the magnitude of strain and in the position of maximum strain pixels.

The results of the current study show that velocity measurements with a unidirectional encoded through-plane PC sequence lead to a significant underestimation of velocity values in tortuous vessels. In all 3 evaluated segments of the distal internal carotid artery, multidirectional velocity encoding revealed significantly higher PV values than those of unidirectional velocity encoding. These results indicate that multidirectional encoding should be preferred to unidirectional encoding for velocity measurements in tortuous vessels. Furthermore, 4D PC-MRI is superior to 2D-3dir in 2 of 3 locations. However, single-slice measurements with multidirectional velocity encoding have higher SNR and may be an alternative to 4D PC-MRI with a scan time of only approximately 90 seconds per slice.