Frequency Limits of Sequential Readout for Sensing AC Magnetic Fields Using Nitrogen-Vacancy Centers in Diamond.

The nitrogen-vacancy (NV) centers in diamond have the ability to sense alternating-current (AC) magnetic fields with high spatial resolution. However, the frequency range of AC sensing protocols based on dynamical decoupling (DD) sequences has not been thoroughly explored experimentally. In this work, we aimed to determine the sensitivity of the ac magnetic field as a function of frequency using the sequential readout method. The upper limit at high frequency is clearly determined by Rabi frequency, in line with the expected effect of finite DD-pulse width. In contrast, the lower frequency limit is primarily governed by the duration of optical repolarization rather than the decoherence time (T2) of NV spins. This becomes particularly crucial when the repetition (dwell) time of the sequential readout is fixed to maintain the acquisition bandwidth. The equation we provide successfully describes the tendency in the frequency dependence. In addition, at the near-optimal frequency of 1 MHz, we reached a maximum sensitivity of 229 pT/Hz by employing the XY4-(4) DD sequence.

Postoperative rehabilitation using a digital healthcare system in patients with total knee arthroplasty: a randomized controlled trial.

INTRODUCTION: Digital healthcare systems based on augmented reality (AR) show promise for postoperative rehabilitation. We compared the effectiveness of AR-based rehabilitation and conventional rehabilitation after total knee arthroplasty (TKA). MATERIALS AND METHODS: We randomly allocated 56 participants to digital healthcare rehabilitation group (DR group) and conventional rehabilitation group (CR group). Participants in the CR group performed brochure-based home exercises for 12 weeks, whereas those in the DR group performed AR-based home exercises that showed each motion on a monitor and provided real-time feedback. The primary outcome was change in 4-m gait speed. The secondary outcomes were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, health-related quality of life [assessed by the EuroQoL 5-Dimension 5-Level (EQ5D5L) questionnaire], pain [measured using a numeric rating scale (NRS)], Berg Balance Scale (BBS), range of motion (ROM), and muscle strength. Outcomes were measured at baseline (T0) and 3 (T1), 12 (T2), and 24 (T3) weeks after randomization. RESULTS: There was no significant difference in baseline characteristics of participants between two groups, except age and body mass index. No group difference was observed in 4-m gait speed (0.37 ± 0.19 and 0.42 ± 0.28 for the DR and CR groups, respectively; p = 0.438). The generalized estimating equation model revealed no significant group by time interaction regarding for 4-m gait speed, WOMAC, EQ5D5L, NRS, BBS, ROM, and muscle strength score. All outcomes were significantly improved in both groups (p < 0.001). CONCLUSION: The use of a digital healthcare system based on AR improved the functional outcomes, pain, and quality of life of patients after TKA. AR-based rehabilitation may be useful treatment as an alternative to conventional rehabilitation. TRIAL REGISTRATION: ClinicalTrials.gov (identifier: NCT04513353). Registered on August 9, 2020. http://clinicaltrials.gov/ct2/show/NCT04513353 .

Aesthetic Reconstruction After Removal of Huge Epidermal Cyst Involving the Calvarium and Dura on the Scalp.

ABSTRACT: Epidermal or epidermoid cysts are one of the most frequent benign masses at the subepidermal level. They are typically smooth, movable, and fluctuant masses covered with stratified squamous epithelium. They rarely grow to a huge size, and only a few cases have been reported. A 69-year-old woman visited the authors' clinic for treatment of a well-defined huge mass in the right temporoparietal and occipital regions of the scalp that had regrown and spontaneously increased in size after excision 30 years prior. Computed tomography revealed a large lobulated mass with an air-fluid level and calvarial bone erosion invading the inner table in the right parietal region. Dural exposure was suspected based on magnetic resonance imaging, which depicted diffuse dural thickening with enhancement.The authors aesthetically excised the mass in cooperation with the Department of Neurosurgery using an inverted T-shaped excisional flap design for the reduction of the redundant scalp similar to that used in reduction mammoplasty surgery. Two months later there was no evidence of recurrence or complications, and the patient was satisfied with the results of the surgery.The authors report the case of a huge scalp mass with skull defect and propose an aesthetic treatment option for this unusual mass on the scalp.

Clinical Outcomes Following the Early Application of Multimodal Scar Programs for Facial Incisional Wounds.

BACKGROUND: Even though scars are major issues for patients who undergo facial lacerations, programs for their prevention and early management are not well established. The purpose of this study was to evaluate the clinical outcomes of prophylactic scar assessments and early scar interventions in patients with lacerations. PATIENTS AND METHODS: A total of 116 patients underwent suture line and scar prevention treatment in the emergency room from 2014 to 2015. In the retrospective study, 46 patients who met all the criteria were included in the study. They were assigned to one of the following two scar prevention programs: the standard scar program for prevention, which included taping, silicone sheets, and ointments, and the multimodality scar program for treatment, which included triamcinolone, botulinum toxins, or CO2 fractional lasers. The patterns of early scar program were investigated for the standard scar prevention program and the multimodality scar management program, and we evaluated the scar assessment scores of the patients at 3 and 6 months. RESULTS: Scar scores for the patients who received multimodality scar management showed statistically significant improvements in Patient Scar Assessment (PSA) scales, Stony Brook Scar Evaluation Scales (SBSES), Vancouver Scar Scale (VSS) scores, and Visual Analog Scar (VAS) scales (the p values were 0.008, 0.007, 0.017, and 0.01, respectively). CONCLUSION: The multimodality scar program is more effective for scar prevention than the standard scar program. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Clinical Features of Skin Infection After Rhinoplasty with Only Absorbable Thread (Polydioxanone) in Oriental Traditional Medicine: A Case Series Study.

BACKGROUND: Polydioxanone (PDO) is absorbable thread which is usually used for wound closure and face lifting. These days, PDO thread is used increasingly for aesthetic purposes such as correction of facial wrinkles, laxity and even rhinoplasty in many oriental traditional medicine clinics. As rhinoplasty with PDO thread increases, complications also increase. In this study, we will report on the clinical features of patients who got rhinoplasty using PDO thread. METHODS: From August 2018 to July 2019, seven patients (three males and four females) visited our clinic for complications after rhinoplasty with PDO thread. We checked ultrasonography and laboratory findings including wound cultures. We used conservative treatment using antibiotics and performed surgery on three patients. RESULTS: Three patients experienced severe complications with open wounds, abscesses and skin necrosis. Four patients experienced mild complications including redness and thread exposure without open wounds. The location of infection included the nasal tip and inner lining. Six patients had a history of rhinoplasty before. On ultrasonography, abscess formation was seen around the implant inserted before. During the operation, PDO thread cannot be seen except in one patient. CONCLUSIONS: PDO thread cannot be seen in radiologic findings and can cause severe infections like abscess formation with open wounds. In severe infections, massive debridement with the removal of the implant would be required. PDO thread is absorbed usually after six months; mild infection can be controlled by the conservative treatment. The best is not undergoing rhinoplasty with PDO thread for patients who had implants because of potential side effects. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Comparison of the Scar Prevention Effect Between a Carbon Dioxide Fractional Laser and a Continuous Ablative Carbon Dioxide Laser with a 595-nm Nd:YAG Laser.

PURPOSE: A linear surgical scar, when located in the head and neck region, can be a significant cosmetic concern. Laser skin resurfacing with a fractional laser and a pulsed dye laser has been proven to be useful for treating such scars. As alternatives, we used a classic ablative CO2 laser in continuous mode with a 1-mm spot size and a 595-nm Nd:YAG laser. We investigated the effect of the combination of the continuous CO2 laser and 595-nm Nd:YAG laser and compared it to the effect of fractional CO2 laser monotherapy on linear scars. METHODS: This was a retrospective, case-controlled study designed to compare the efficacy between fractional CO2 laser therapy and combination therapy with a conventional CO2 laser in continuous mode and a 595-nm Nd:YAG laser. Treatment efficacy was evaluated by two different scar scales: the Stony Brook Scar Evaluation Scale (SBSES) and the modified Vancouver Scar Scale (mVSS). Laser treatments were performed every month until the 6th month after surgery. RESULTS: The SBSES and mVSS scores improved over time in both the monotherapy and the combination therapy (P < 0.001). No significant differences were found between the therapies for all the subcategories of the SBSES. However, among all the subcategories of the mVSS, pigmentation showed a better prognosis with combination therapy (P = 0.04). CONCLUSION: Monotherapy and combination therapy can provide similar positive effects on linear scar improvement after repeated treatment, whereas combination therapy exerts more favorable anti-pigmentation effects than monotherapy. The combination of a continuous ablative CO2 laser with a 595-nm Nd:YAG laser can be used as a favorable alternative to a fractional CO2 laser. The 1-mm spot size of the CO2 laser beam may mimic the fractional laser form and offer more effective results for linear incision scars. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Clinical Impact of Highly Condensed Stromal Vascular Fraction Injection in Surgical Management of Depressed and Contracted Scars.

BACKGROUND: Recent research on stromal vascular fraction (SVF) has demonstrated the presence of numerous growth factors that aid in tissue regeneration and suggest the potential for scar treatment. This study was conducted to clinically show that adding stem cells can improve the surgical outcomes of scar formation. METHODS: Between March 2014 and February 2016, 17 patients underwent injections of fat and highly condensed SVF simultaneously with scar reduction surgeries and 15 patients received scar revision with or without simultaneous application of highly condensed SVF (4.90 × 107 stem cells/ml) at our institution. Clinical photographs were taken before and after surgery, and the scars were graded using the following standard scales: the Observer Scar Assessment Scale (OSAS), Stony Brook Scar Evaluation Scale (SBSES), Vancouver Scar Scale (VSS), and Visual Analog Scale (VAS). RESULTS: All patients showed improvement, registering significant increases in scar tissue scores (P < 0.05 in all four scoring systems). Patients in the SVF group showed more improved outcomes than patients in the non-SVF group for all scar tissue scores except the SBSES (OSAS, P = 0.029; SBSES, P = 0.281; VSS, P = 0.001; VAS, P = 0.021). Subcategories of these scales reflected more favorable outcomes in terms of height and pliability; however, there was no significant change in vascularity. CONCLUSIONS: SVF injections enhance tissue regeneration by contributing stem cells and growth factors to improve outcomes in scar revisions or tissue grafts. Harvesting the SVF through liposuction also provides a cosmetic benefit. Significant SVF-related gains in the scoring of scars indicate the merit of SVF as an aspect of conventional scar management. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Cyanobacterial Contribution to Travertine Deposition in the Hoyoux River System, Belgium.

Travertine deposition is a landscape-forming process, usually building a series of calcareous barriers differentiating the river flow into a series of cascades and ponds. The process of carbonate precipitation is a complex relationship between biogenic and abiotic causative agents, involving adapted microbial assemblages but also requiring high levels of carbonate saturation, spontaneous degassing of carbon dioxide and slightly alkaline pH. We have analysed calcareous crusts and water chemistry from four sampling sites along the Hoyoux River and its Triffoy tributary (Belgium) in winter, spring, summer and autumn 2014. Different surface textures of travertine deposits correlated with particular microenvironments and were influenced by the local water flow. In all microenvironments, we have identified the cyanobacterium Phormidium incrustatum (Nägeli) Gomont as the organism primarily responsible for carbonate precipitation and travertine fabric by combining morphological analysis with molecular sequencing (16S rRNA gene and ITS, the Internal Transcribed Spacer fragments), targeting both field populations and cultures to exclude opportunistic microorganisms responding favourably to culture conditions. Several closely related cyanobacterial strains were cultured; however, only one proved identical with the sequences obtained from the field population by direct PCR. This strain was the dominant primary producer in the calcareous deposits under study and in similar streams in Europe. The dominance of one organism that had a demonstrated association with carbonate precipitation presented a valuable opportunity to study its function in construction, preservation and fossilisation potential of ambient temperature travertine deposits. These relationships were examined using scanning electron microscopy and Raman microspectroscopy.

Toward a brain functional connectivity mapping modality by simultaneous imaging of coherent brainwaves.

Matching the proton-magnetic-resonance frequency to the frequency of a periodic neural oscillation (e.g., alpha or gamma band waves) by magnetic resonance imaging techniques, enables direct visualization of brain functional connectivity. Functional connectivity has been studied by analyzing the correlation between coherent neural oscillations in different areas of the brain. In electro- or magneto-encephalography, coherent source reconstruction in a source-space is very tricky due to power leaking from the correlation among the sources. For this reason, most studies have been limited to sensor-space analyses, which give doubtful results because of volume current mixing. The direct visualization of coherent brain oscillations can circumvent this problem. The feasibility of this idea was demonstrated by conducting phantom experiments with a SQUID-based, micro-Tesla NMR/MRI system. We introduce an experimental trick, an effective step-up of the measurement B-field in a pulse sequence, to decouple the magnetic resonance signal from the strong magneto-encephalographic signal at the same frequency.

Rosuvastatin attenuates inflammation, apoptosis and fibrosis in a rat model of cyclosporine-induced nephropathy.

BACKGROUND/AIM: Cyclosporine (CsA)-induced kidney injury is characterized by renal dysfunction with inflammatory cell infiltrations, apoptosis and fibrosis. Pleiotropic effects of statins may exert anti-inflammatory, antiapoptotic and antifibrotic actions beyond lipid control. The aim of this study is to investigate whether rosuvastatin (RUS) has anti-inflammatory, antiapoptotic and antifibrotic effects on chronic CsA-induced nephropathy in a rat model. METHODS: Male Sprague-Dawley rats fed a low-sodium diet were divided into three treatment groups: control (0.9% saline injection), CsA (15 mg/kg/day by subcutaneous injection), CsA + RUS (10 mg/kg/day by gastric gavage). Renal function, CsA level and lipid levels were measured at the end of 4 weeks. The expression of ED-1, transforming growth factor-ß(1) (TGF-ß(1)) and α-smooth muscle actin (α-SMA) for inflammation and fibrosis were examined by Western blot analysis. The expression levels of apoptosis-associated factors were examined by Western blot analysis. Apoptosis was evaluated using the terminal deoxynucleotidyl transferase-mediated biotin nick end-labeling (TUNEL) method. RESULTS: Kidney function was decreased in CsA-treated rats compared with controls, which was attenuated by RUS. RUS did not affect the lipid level or the blood CsA level. TUNEL staining showed that RUS inhibited CsA-induced tubular apoptosis. RUS decreased CsA-induced increased expression of Bax/Bcl-2 ratio. The expressions of ED-1, α-SMA, TGF-ß(1), Smad2/3, Smad4 and p-JNK were increased in CsA-treated rats, which were attenuated by RUS. Tubular atrophy and interstitial fibrosis in CsA-treated rats were attenuated by RUS supplementation. CONCLUSION: RUS supplementation attenuates proinflammatory and apoptosis-related factors and inhibits the fibrotic pathways including the smad-dependent and smad-independent pathways in a rat model of CsA-induced nephropathy.

Real-time pulse measurement of nano-scale field effect transistors: cancellation of displacement current and extraction of coupling capacitance.

Real-time pulse measurements of nano-scale field effect transistors (FETs) are reported. We demonstrate the direct monitoring of the real-time current of bottom-up assembled silicon nanowire FET and top-down fabricated gate-all-around silicon nanowire FET, both with the diameter of approximately 50 nm. We demonstrate that the displacement current can be cancelled out from the measured pulse responses. On the other hand, the displacement current also can be utilized to obtain the coupling capacitance between the gate and source of the FETs.

Chemical Analysis of an Isotopically Labeled Molecule Using Two-Dimensional NMR Spectroscopy at 34 µT.

Low-field nuclear magnetic resonance (NMR) spectroscopy, conducted at or below a few millitesla, provides only limited spectral information due to its inability to resolve chemical shifts. Thus, chemical analysis based on this technique remains challenging. One potential solution to overcome this limitation is the use of isotopically labeled molecules. However, such compounds, particularly their use in two-dimensional (2D) NMR techniques, have rarely been studied. This study presents the results of both experimental and simulated correlation spectroscopy (COSY) on 1-13C-ethanol at 34.38 µT. The strong heteronuclear coupling in this molecule breaks the magnetic equivalence, causing all J-couplings, including homonuclear coupling, to split the 1H spectrum. The obtained COSY spectrum clearly shows the spectral details. Furthermore, we observed that homonuclear coupling between 1H spins generated cross-peaks only when the associated 1H spins were coupled to identical 13C spin states. Our findings demonstrate that a low-field 2D spectrum, even with a moderate spectral line width, can reveal the J-coupling networks of isotopically labeled molecules.

Dual-Emissive Mn-Doped Lead Halide Perovskite Nanocrystals as Background-Suppressed Latent Fingerprint Detection Probes.

Diverse strategies have been developed to visualize latent fingerprints (LFPs) that are undetectable by the naked eye. Among them, fluorescence-based approaches have emerged as an attractive method for enabling high-resolution LFP imaging. However, the use of fluorescent probes for LFP detection remains challenging due to cumbersome processing, low selectivity, and high background interference. Here, we demonstrate highly efficient, sensitive, and background-free LFP detection with dual-color emission arising from manganese (Mn)-doped lead halide perovskite (CsPb(Cl1-yBry)3) nanocrystals (NCs). The resulting bright, fluorescent, solid-state nanopowder (NP) permits the visualization of LFP ridge structures and the resolution of level 1-3 LFP features. The dual-color emission of the Mn-doped perovskite NP provides a simple, robust, and effective route to overcome background interference, thereby increasing the resolution and sensitivity of the LFP detection. The combination of the high quantum efficiency and dual emission of Mn-doped perovskite NP offers great potential for forensic science.

Retrospective study of the efficacy of vascularized tissue transfer for treating antibiotic-resistant bacteria-infected wound: Comparison with clean and antibiotic-sensitive bacteria-infected wound.

ABSTRACT: If wounds are infected with bacteria resistant to an empirical antibiotic regimen, effective wound treatment will be delayed. This can delay wound healing and lengthen hospital stays, increasing the costs to patients. Long-term antibiotic use can also result in minor and major complications, such as diarrhea, antibiotic resistance, or life-threatening leukopenia. Multidrug-resistant (MDR) bacteria make wound treatment even more difficult. Traditionally, surgeons thought that adequate infection control should be established before soft tissue coverage. However, wounds infected by MDR do not heal well with this traditional method and there are no optimal treatment guidelines for MDR bacteria-contaminated wounds.We reviewed 203 patients who underwent vascularized flap surgery from 2012 to 2019 to cover wounds. Class IV and I wounds were compared according to the Centers for Disease Control and Prevention classification. Class IV was further classified as antibiotic-resistant (ARB) and antibiotic-sensitive (ASB) bacteria. Wound size, mode, location, pathogens, healing time, and basic demographics were evaluated. Data were compared using Cramer's V and one-way ANOVA or independent t tests.The average healing time was longer in the ARB (19.7 [range 7-44] days) and ASB (17.9 [range 2-36] days) groups than in the Clean group (16.5 [range 7-28] days). Healing time differed in the 3 groups (P = .036). It was longer in the class IV group than in the class I group (P = .01). However, it was not statistically different between the ARB and ASB groups (P = .164).In our study the difference in healing time was small when vascularized tissue transfer was done in ARB-infected wound compared with ASB-infected and clean wound. It is necessary to perform surgery using vascularized tissue for the infected wound of antibiotic-resistant bacteria.

Breast reconstruction after complications following breast augmentation with massive filler injections.

INTRODUCTION: Breast filler injections are less commonly used due to their associated complications, such as pain and foreign body reactions. Yet, these fillers are often administered illegally, resulting in aesthetic or life-threatening complications. These are treated by removing the foreign material, and the breasts are reconstructed using silicone implants or autologous tissue/fat injection. PATIENT CONCERNS: Case 1. A 45-year-old woman with polyacrylamide gel injections in both breasts visited our clinic for breast pain and tenderness. Grade I ptosis was observed in each breast, without skin necrosis and discoloration. Case 2. A 51-year-old woman, with unknown breast filler injections, visited our clinic for painful masses. Intraoperatively, massive amounts of foreign material had severely infiltrated the nearby tissues; thus, an immediate breast reconstruction could not be performed. Three months later, severe deformities including shrinkage and irregular breast skin surfaces were observed. DIAGNOSIS: Case 1. Multiple cystic lesions, fluid collection in the retromammary spaces, and diffuse infiltration were observed on mammography, computed tomography, and ultrasonography. Case 2. Multiple cystic lesions, calcified areas, and diffuse infiltrations in the axillae and retromammary spaces were observed on mammography, computed tomography, and ultrasonography. INTERVENTIONS: Case 1. The foreign material was removed and the breasts were reconstructed using silicone implants into subpectoral pocket with acellular dermal matrices (Alloderm, Lipocell Corporation). Case 2. A delayed reconstruction was undertaken using silicone implants covered by latissimus dorsi muscle flaps, 3 months after the foreign material removal. OUTCOMES: Case 1. The foreign material was removed and there were no complications such as foreign body reaction, capsular contracture. Ptosis was corrected and both breasts were symmetric with proper projection. Case 2. Residual foreign material was removed and there were no complications such capsular contracture, implant malposition. CONCLUSION: Massive injections of foreign materials into the breast can cause severe infiltration and associated foreign body reactions. By a near-complete removal of the foreign materials and breast reconstruction using silicone implants, we achieved satisfactory results, without complications such as wound disruption, capsular contracture, and implant malposition.

Usefulness of ultrasonography in determining the surgical excision margin in non-melanocytic skin cancer: A comparative analysis of preoperative ultrasonography and postoperative histopathology.

ABSTRACT: Skin cancer diagnoses are rising due to increasing ultraviolet ray exposure and an aging population. The complete surgical excision of skin cancer, including a normal tissue, has been the widely performed and determining the adequate safety margin is essential. In this study, we compared the preoperative thickness and width of skin cancer by ultrasonography with the measurements by histopathologic findings.A total of 211 patients were enrolled in this study and ultrasonography was performed on 30 patients. The width (long and short axis) and thickness of the skin cancers were measured using electronic calipers of ultrasonographic calipers preoperatively and microscope postoperatively.The skin cancers were basal cell carcinoma (n = 17), squamous cell carcinoma (n = 10), Merkel cell carcinoma (n = 1), mucinous carcinoma (n = 1), and sebaceous carcinoma (n = 1). The mean width (long and short axis) and thickness of the cancers measured by ultrasonography was 1.25 (0.76) cm, 0.96 (0.65) cm, and 0.37 (0.28) cm. The measurements by histopathology was 1.24 (0.84) cm, 0.95 (0.65) cm, and 0.27 (0.24) cm. Kendall's tau-b correlation coefficient between measurements by ultrasonography and histopathology was as follows: long axis, r = 0.733, P < .001; short axis, r = 0.671, P < .001; thickness, r = 0.740, P < .001. Spearman's rank correlation coefficient between measurements by ultrasonography and histopathology was as follows: long axis, r = 0.865, P < .001; short axis, r = 0.829, P < .001; thickness, r = 0.842, P < .001. The difference in mean thickness between the total excised tissue and the skin cancer was 0.29 (0.43) cm (range 0.05-0.40 cm) in basal cell carcinoma and 0.56 (0.58) cm (range 0.05-2.22 cm) in squamous cell carcinoma.Ultrasonography can accurately measure the width and thickness of skin cancer and predict the safety margins of the wide excision. Preoperative ultrasonography is a good diagnostic tool for surgical planning. Additional studies with larger populations are needed to quantify the range of vertical safety margins.

In-situ Overhauser-enhanced nuclear magnetic resonance at less than 1 µT using an atomic magnetometer.

The development of atomic magnetometers has led to nuclear magnetic resonance (NMR) in zero and ultralow magnetic fields without using cryogenic sensors. However, in-situ detection, meaning that a sample locates in the detection space beside a vapor cell, has been conducted only with parahydrogen-induced polarization. Other hyperpolarization techniques remain unexplored yet. In this work, we demonstrate that Overhauser dynamic nuclear polarization allows in-situ NMR detection with an atomic magnetometer at less than 1 µT. The 1H NMR signal of a nitroxide radical solution was observed at 13.83 Hz, which corresponds to 325 nT. Signal-to-noise ratio was 32 after sixteen averages. On the Larmor precession of 1H spins, a decaying oscillation was superimposed. We attribute it to a transient 87Rb spin precession in response to a non-adiabatic field variation. This work shows a new capability of zero- and ultralow-field NMR.

SQUID-based ultralow-field MRI of a hyperpolarized material using signal amplification by reversible exchange.

The signal amplification by reversible exchange (SABRE) technique is a very promising method for increasing magnetic resonance (MR) signals. SABRE can play a particularly large role in studies with a low or ultralow magnetic field because they suffer from a low signal-to-noise ratio. In this work, we conducted real-time superconducting quantum interference device (SQUID)-based nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI) studies in a microtesla-range magnetic field using the SABRE technique after designing a bubble-separated phantom. A maximum enhancement of 2658 for 1H was obtained for pyridine in the SABRE-NMR experiment. A clear SABRE-enhanced MR image of the bubble-separated phantom, in which the para-hydrogen gas was bubbling at only the margin, was successfully obtained at 34.3 µT. The results show that SABRE can be successfully incorporated into an ultralow-field MRI system, which enables new SQUID-based MRI applications. SABRE can shorten the MRI operation time by more than 6 orders of magnitude and establish a firm basis for future low-field MRI applications.

Dynamic nuclear polarisation of liquids at one microtesla using circularly polarised RF with application to millimetre resolution MRI.

Magnetic resonance imaging in ultra-low fields is often limited by mediocre signal-to-noise ratio hindering a higher resolution. Overhauser dynamic nuclear polarisation (O-DNP) using nitroxide radicals has been an efficient solution for enhancing the thermal nuclear polarisation. However, the concurrence of positive and negative polarisation enhancements arises in ultra-low fields resulting in a significantly reduced net enhancement, making O-DNP far less attractive. Here, we address this issue by applying circularly polarised RF. O-DNP with circularly polarised RF renders a considerably improved enhancement factor of around 150,000 at 1.2 µT. A birdcage coil was adopted into an ultra-low field MRI system to generate the circularly polarised RF field homogeneously over a large volume. We acquired an MR image of a nitroxide radical solution with an average in-plane resolution of 1 mm. De-noising through compressive sensing further improved the image quality.