Biplanar quadrature coil for versatile low-field extremity MRI

Funding This work is supported by the Swiss National Science Foundation (Grant Numbers 170575, 186861, and 198905). Acknowledgments The authors warmly thank Prof. Dr. André Constantinesco for sharing his expertise in low-field technologies, as well as for his generosity and strong support especially during the early days of the AMT Center, when the platform was still in the making.Peer reviewedPublisher PD

Fast, interleaved, Look‐Locker–based T1 mapping with a variable averaging approach : Towards temperature mapping at low magnetic field

The authors thank COST Action CA15209 for insightful discussions. This research was funded by the Swiss National Science Foundation (Grant Nos. 170575, 186861, and 198905). Open access funding provided by Universitat Basel.Peer reviewedPublisher PD

Biplanar quadrature coil for versatile low-field extremity MRI

Biplanar magnets offer extended flexibility in MRI, particularly appealing due to unmatched accessibility to the patient. At low field strength (<0.2 T), such geometries could be particularly suitable for interventional settings or purpose-built applications such as musculoskeletal imaging. In the proposed work, we present a dual-channel, biplanar coil array for low-field MRI featuring almost fully open access when sited in a biplanar magnet. The proposed detector relies on the assembly of two orthogonal biplanar coils (single transmit channel, two receive channels in quadrature) respectively interfaced with custom inductive couplers. Simulations of the B1 field in each element were performed before the quadrature coil was built and used at ∼ 0.1 T (4.33 MHz). Once assembled, the best performance in our setup was achieved in undermatched conditions in place of conventional 50-Ω matching. Phantom images display the extended coverage of the quadrature coil, with similar SNR from each individual biplanar coil. The combined images show an expected SNR gain of 2 that confirms good decoupling between the two channels (−36 dB). To the best of our knowledge, the proposed coil represents the first implementation of a biplanar geometry at low field and the first quadrature detection for a biplanar design. The open design and overall good sensitivity of our biplanar design enabled fast and quasi-isotropic 3D imaging with (1.6 × 1.6 × 2.2) mm3 resolution in vivo in human extremities

Nanodiamond-enhanced MRI via in situ hyperpolarization

Nanodiamonds are of interest as nontoxic substrates for targeted drug delivery and as highly biostable fluorescent markers for cellular tracking. Beyond optical techniques, however, options for noninvasive imaging of nanodiamonds in vivo are severely limited. Here, we demonstrate that the Overhauser effect, a proton–electron polarization transfer technique, can enable high-contrast magnetic resonance imaging (MRI) of nanodiamonds in water at room temperature and ultra-low magnetic field. The technique transfers spin polarization from paramagnetic impurities at nanodiamond surfaces to 1H spins in the surrounding water solution, creating MRI contrast on-demand. We examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous in situ hyperpolarization via the Overhauser mechanism, in combination with the excellent in vivo stability of nanodiamond, raises the possibility of performing noninvasive in vivo tracking of nanodiamond over indefinitely long periods of time

Quantitative MRI to Characterize the Nucleus Pulposus Morphological and Biomechanical Variation According to Sagittal Bending Load and Radial Fissure, an ex vivo Ovine Specimen Proof-of-Concept Study

Background and context: Low back pain is a dramatic burden worldwide. Discography studies have shown that 39% of chronic low back pain patients suffer from discogenic pain due to a radial fissure of intervertebral disc. This can have major implications in clinical therapeutic choices. The use of discography is restricted because of its invasiveness and interest in it remains low as it represents a static condition of the disc morphology. Magnetic Resonance Imaging (MRI) appears to be less invasive but does not describe the biomechanical dynamic behavior of the fissure.Purpose: We aimed to seek a quantitative MRI protocol combined with ex vivo sagittal loading to analyze the morphological and biomechanical changes of the intervertebral disc structure and stress distribution.Study design: Proof of concept.Methods: We designed a proof-of-concept ovine study including 3 different 3.0 T-MRI sequences (T2-weighted, T1 and T2 mapping). We analyzed 3 different mechanical states (neutral, flexion and extension) on a fresh ovine spine specimen to characterize an intervertebral disc before and after puncturing the anterior part of the annulus fibrosus. We used a mark tracking method to calculate the bending angles and the axial displacements of the discal structures. In parallel, we created a finite element model to calculate the variation of the axial stress and the maximal intensity shear stress, extrapolated from our experimental boundary conditions.Results: Thanks to an original combination of specific nuclear relaxation time quantifications (T1, T2) of the discal tissue, we characterized the nucleus movement/deformation into the fissure according to the synchronous mechanical load. This revealed a link between disc abnormality and spine segment range of motion capability. Our finite element model highlighted significant variations within the stress distribution between intact and damaged disc.Conclusion: Quantitative MRI appears to provide a new opportunity to characterize intra-discal structural morphology, lesions and stress changes under the influence of mechanical load. This preliminary work could have substantial implications for non-invasive disc exploration and could help to validate novel therapies for disc treatment

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Développement et validation de l’élastographie pour le diagnostic des pathologies hépatiques chroniques

Le but de cette thèse était d’apporter un certain nombre d’améliorations techniques et méthodologiques à l’élastographie par résonance magnétique afin d’assurer le confort du patient, mais aussi de mieux comprendre les phénomènes impliqués dans le changement des propriétés mécaniques du foie. Ainsi, cette thèse a été construite de manière à améliorer les méthodes et les valider sur modèles animaux. La faisabilité clinique était étudiée en parallèle. Cette thèse repose principalement sur deux études expérimentales. En effet, différents modèles animaux ont été utilisés afin de mettre en relief le rôle de l’élastographie par résonance magnétique dans le diagnostic des maladies chroniques du foie. Ce doctorat a débouché sur deux publications en premier auteur. La première valide la méthode sur foie entier chez des rats avec fibrose hépatique induite au tétrachlorure de carbone et montre que les paramètres visco-élastiques sont corrélés à la quantité de fibrose. La deuxième étude, plus complexe, intègre différents modèles animaux afin d’apporter un début de réponse au rôle de l’élastographie par IRM dans le diagnostic des maladies à foie stéatosique. Il s’agissait de rats nourris avec une diète standard, une diète déficiente en choline jusqu’à 8 semaines pour induire une stéatohépatite, une diète enrichie en acide orotique pendant 2 semaines pour induire une stéatose simple, ou de rats ayant reçu une injection unique de CCl4 pour provoquer une lésion hépatique aigue. Les résultats principaux montraient une augmentation de la viscosité chez les rats à stéatose simple et une augmentation à la fois de l’élasticité et de la viscosité chez les rats avec lésion hépatique aigue. De plus, il a été montré chez les rats avec stéatohépatite une augmentation de l’élasticité et de la viscosité en l’absence de fibrose établie, alors que l’activation de la fibrogenèse était enclenchée, accompagnée d’une légère inflammation. L’analyse multivariée de tous les rats a montré que les changements d’élasticité sont principalement expliqués par l’activation des cellules stellaires (et donc de la fibrogenèse), alors que les changements de viscosité pourraient être expliqués par la présence de graisse. Ainsi, cette thèse a permis d’améliorer le confort du patient (matelas d'IRM et séquence rapide) pour faciliter l’intégration de cet examen en routine clinique, mais également de valider l’élastographie comme marqueur de la fibrose et des propriétés mécaniques des tissus. Pour finir, cette thèse a mis en avant le rôle potentiel de l’élastographie par IRM pour la détection précoce des patients à risque dans le cadre des stéatohépatites.(SBIM 3) -- UCL, 200

Fast acquisition of propagating waves in humans with low-field MRI: Toward accessible MR elastography

Most commonly used at clinical magnetic fields (1.5 to 3 T), magnetic resonance elastography (MRE) captures mechanical wave propagation to reconstruct the mechanical properties of soft tissue with MRI. However, in terms of noninvasively assessing disease progression in a broad range of organs (e.g., liver, breast, skeletal muscle, and brain), its accessibility is limited and its robustness is challenged when magnetic susceptibility differences are encountered. Low-field MRE offers an opportunity to overcome these issues, and yet it has never been demonstrated in vivo in humans with magnetic fields <1.5 T mainly because of the long acquisition times required to achieve a sufficient signal-to-noise ratio. Here, we describe a method to accelerate 3D motion-sensitized MR scans at 0.1 T using only 10%; k; -space sampling combined with a high-performance detector and an efficient encoding acquisition strategy. Its application is demonstrated in vivo in the human forearm for a single motion-encoding direction in less than 1 min