Unilateral Magnetic Resonance Research Articles

Staged Bilateral MRI-Guided Focused Ultrasound Subthalamotomy for Parkinson Disease.

Unilateral magnetic resonance imaging (MRI)-guided focused ultrasound subthalamotomy (FUS-STN) improves cardinal motor features among patients with asymmetrical Parkinson disease (PD). The feasibility of bilateral FUS-STN is as yet unexplored. To assess the safety and effectiveness of staged bilateral FUS-STN to treat PD. This prospective, open-label, case series study was conducted between June 18, 2019, and November 7, 2023, at HM-CINAC, Puerta del Sur University Hospital, Madrid, Spain, and included 6 patients with PD who had been treated with unilateral FUS-STN contralateral to their most affected body side and whose parkinsonism on the untreated side had progressed and was not optimally controlled with medication. Staged bilateral FUS-STN. Primary outcomes were assessed 6 months after the second treatment and included safety (incidence and severity of adverse events after second treatment) and effectiveness in terms of motor change (measured with the Movement Disorders Society Unified Parkinson's Disease Rating Scale part III [MDS-UPDRS III]) in the off-medication state (ie, after at least 12 hours of antiparkinsonian drug withdrawal) compared with baseline (ie, prior to the first side ablation). Secondary outcomes included motor change in patients in the on-medication state (ie, after usual antiparkinsonian medication intake), motor complications (measured with the MDS-UPDRS IV), daily living activities (measured with the MDS-UPDRS I-II), quality of life (measured with the 39-item Parkinson's Disease Questionnaire), change in dopaminergic treatment, patient's global impression of change (measured with the Global Impression of Change [PGI-C] scale), and long-term (24-month) follow-up. Of 45 patients previously treated with unilateral FUS-STN, 7 were lost to follow-up, and 4 were excluded due to adverse events. Of the remaining 34 patients, 6 (median age at first FUS-STN, 52.6 years [IQR, 49.0-57.3 years]; 3 women [50%]) experienced progression of parkinsonism on the untreated body side and were included. At the time of the first FUS-STN, patients' median duration of disease was 5.7 years (IQR, 4.7-7.3 years). The median time between procedures was 3.2 years (IQR, 1.9-3.5 years). After the second FUS-STN, 4 patients presented with contralateral choreic dyskinesia, which resolved by 3 months. Four patients developed speech disturbances, which gradually improved but remained in a mild form for 2 patients at 6 months; 1 patient experienced mild imbalance and dysphagia during the first week after treatment, which subsided by 3 months. No behavioral or cognitive disturbances were found on neuropsychological testing. For patients in the off-medication state, MDS-UPDRS III scores improved by 52.6% between baseline and 6 months after the second FUS-STN (from 37.5 [IQR, 34.2-40.0] to 20.5 [IQR, 8.7-24.0]; median difference, 23.0 [95% CI, 7.0-33.7]; P = .03). The second treated side improved by 64.3% (MDS-UPDRS III score, 17.0 [IQR, 16.0-19.5] prior to the second treatment vs 5.5 [IQR, 3.0-10.2]; median difference, 9.5 [95% CI, 3.2-17.7]; P = .02). After the second procedure, all self-reported PGI-C scores were positive. Findings of this pilot study suggest that staged bilateral FUS-STN was safe and effective for the treatment of PD, although mild but persistent speech-related adverse events were observed among a small number of patients.

Automated evaluation of hip abductor muscle quality and size in hip osteoarthritis: Localized muscle regions are strongly associated with overall muscle quality

Limited information exists regarding abductor muscle quality variation across its length and which locations are most representative of overall muscle quality. This is exacerbated by time-intensive processes for manual muscle segmentation, which limits feasibility of large cohort analyses. The purpose of this study was to develop an automated and localized analysis pipeline that accurately estimates hip abductor muscle quality and size in individuals with mild-to-moderate hip osteoarthritis (OA) and identifies regions of each muscle which provide best estimates of overall muscle quality.Forty-four participants (age 52.7 ± 16.1 years, BMI 23.7 ± 3.4 kg/m2, 14 males) with and without mild-to-moderate radiographic hip OA were recruited for this study. Unilateral hip magnetic resonance (MR) images were acquired on a 3.0 T MR scanner and included axial T1-weighted fast spin echo and 3D axial Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation (IDEAL-IQ) spoiled gradient-recalled echo (SPGR) with multi-peak fat spectrum modeling and single T2* correction. A three dimensional (3D) V-Net convolutional neural network was trained to automatically segment the gluteus medius (GMED), gluteus minimus (GMIN), and tensor fascia lata (TFL) on axial IDEAL-IQ. Agreement between manual and automatic segmentation and associations between axial fat fraction (FF) estimated from IDEAL-IQ and overall muscle FF were evaluated.Dice scores for automatic segmentation were 0.94, 0.87, and 0.91 for GMED, GMIN, and TFL, respectively. GMED, GMIN, and TFL volumetric and FF measures were strongly correlated (r: 0.92–0.99) between automatic and manual segmentations, with 95% limits of agreement of [−1.99%, 2.89%] and [−9.79 cm3, 17.43 cm3], respectively. Axial FF was significantly associated with overall FF with the strongest correlations at 50%, 50%, and 65% the length of the GMED, GMIN, and TFL muscles, respectively (r: 0.93–0.97). An automated and localized analysis can provide efficient and accurate estimates of hip abductor muscle quality and size across muscle length. Specific regions of the muscle may be used to estimate overall muscle quality in an abbreviated evaluation of muscle quality.

Unilateral Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy Thalamotomy for Essential Tremor.

Essential tremor (ET) affects numerous adults, impacting quality of life (QOL) and often defying pharmacological treatment. Surgical interventions like deep brain stimulation (DBS) and lesional approaches, including radiofrequency, gamma-knife radiosurgery, and magnetic resonance imaging (MRI)-guided focused ultrasound, offer solutions but are not devoid of limitations. This retrospective, single-center, single-blinded pilot study aimed to assess the safety and efficacy of unilateral MRI-guided laser interstitial thermal therapy (MRIg-LITT) thalamotomy for medically intractable ET. Nine patients with ET, unresponsive to medications and unsuitable for DBS, underwent unilateral MRIg-LITT thalamotomy. We assessed tremor severity, QOL, cognitive function, and adverse events (AE) over a 12-month period. Tremor severity significantly improved, with a reduction of 83.37% at 12 months post-procedure. QOL scores improved by 74.60% at 12 months. Reported AEs predominantly included transient dysarthria, proprioceptive disturbances, and gait balance issues, which largely resolved within a month. At 3 months, 2 patients (22%) exhibited contralateral hemiparesis requiring physiotherapy, with 1 patient (11%) exhibiting persistent hemiparesis at 12 months. No significant cognitive impairment was detected post-procedure. Unilateral MRIg-LITT thalamotomy yielded substantial and enduring tremor alleviation and enhanced QOL in patients with ET that is resistant to medication. The AE profile was acceptable. Our findings support the need for additional research with expanded patient cohorts and extended follow-up to corroborate these outcomes and to refine the role of MRIg-LITT as a targeted and minimally invasive approach for ET management. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Outcomes of Focused Ultrasound Thalamotomy in Tremor Syndromes.

The current literature comparing outcomes after a unilateral magnetic resonance image-guided focused ultrasound (MRgFUS) thalamotomy between tremor syndromes is limited and remains a possible preoperative factor that could help predict the long-term outcomes. The aim was to report on the outcomes between different tremor syndromes after a unilateral MRgFUS thalamotomy. A total of 66 patients underwent a unilateral MRgFUS thalamotomy for tremor between November 2018 and May 2020 at St Vincent's Hospital Sydney. Each patient's tremor syndrome was classified prior to treatment. Clinical assessments, including the hand tremor score (HTS) and Quality of Life in Essential Tremor Questionnaire (QUEST), were performed at baseline and predefined intervals to 36 months. A total of 63 patients, comprising 30 essential tremor (ET), 24 dystonic tremor (DT), and 9 Parkinson's disease tremor (PDT) patients, returned for at least one follow-up. In the ET patients, at 24 months there was a 61% improvement in HTS and 50% improvement in QUEST compared to baseline. This is in comparison to PDT patients, where an initial benefit in HTS and QUEST was observed, which waned at each follow-up, remaining significant only up until 12 months. In the DT patients, similar results were observed to the ET patients: at 24 months there was a 61% improvement in HTS and 43% improvement in QUEST compared to baseline. These results support the use of unilateral MRgFUS thalamotomy for the treatment of DT, which appears to have a similar expected outcome to patients diagnosed with ET. Patients with PDT should be warned that there is a risk of treatment failure. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Improving the SNR of UMR sensor using LC resonator

Single-sided or unilateral magnetic resonance (UMR) technology has various benefits, such as an open structure, low cost, portability, and nondestructive measurement, in contrast to the conventional closed magnet structure. UMR is widely used in material analysis, well logging, and biomedicine. However, its development is constrained by its poor signal-to-noise ratio (SNR). To enhance the SNR of UMR sensor, a surface coil of LC resonator is added on the Radio Frequency (RF) coil. First, a method of calculating the current in the RF coil including LC resonator is derived. Next, the equivalent AC resistance of the coil is calculated using the partial-element equivalent-circuit (PEEC) method. Finally, the SNR of a UMR sensor incorporating LC resonator is analyzed, and its sensitivity map is provided. Experimental comparisons are made between the UMR sensor with and without a LC resonator. Results show that the SNR of the UMR can be enhanced by up to three times after the LC resonator is loaded. The SNR improves within 30 mm of the coil surface, and this beneficial effect steadily diminishes as the distance increases. This study offers a useful method for improving the signal of UMR sensors.

Proton transverse relaxation times depending on the unsaturated fatty acids: a magnetic resonance relaxometric study on beef fat samples

ABSTRACT The unsaturated fatty acid content of beef meat is an important property that affects the health and sense of taste of the consumer and determines price. Fresh beef fat samples were measured by a bilateral low-field time-domain proton magnetic resonance (MR) apparatus. The proton transverse relaxation time (T2) for 18 fat samples were measured at 40.0°C using the Carr-Purcell-Meiboom-Gill method. The results showed that T2 increased linearly with unsaturated fatty acid content. By using the linear dependence of T2 on the unsaturated fatty acid content, we successfully estimated the contents of oleic acid, total monounsaturated fatty acid, and total unsaturated fatty acid with root-mean-square errors of 2.5, 2.8, and 3.2 wt%, respectively. The proposed T2-relaxometry-based method could be performed using a portable unilateral MR surface scanner, which would enable in-vivo nondestructive noninvasive measurements of live cattle for the optimization of the feeding and fattening timing from calf to adult and for the best choice of the shipment timing in terms of the maximization of unsaturated fatty acid content of beef meat.

Optimized Unilateral Magnetic Resonance Sensor with Constant Gradient and Its Applications in Composite Insulators

In this study, an optimized unilateral magnetic resonance sensor with a three-magnet array is presented for assessing the aging of composite insulators in power grids. The sensor’s optimization involved enhancing the static magnetic field strength and the homogeneity of the RF field while maintaining a constant gradient in the direction of the vertical sensor surface and maximizing homogeneity in the horizontal direction. The center layer of the target area was positioned 4 mm from the coil’s upper surface, resulting in a magnetic field strength of 139.74 mT at the center point of the area, with a gradient of 2.318 T/m and a corresponding hydrogen atomic nuclear magnetic resonance frequency of 5.95 MHz. The magnetic field uniformity over a 10 mm × 10 mm range on the plane was 0.75%. The sensor measured 120 mm × 130.5 mm × 76 mm and weighed 7.5 kg. Employing the optimized sensor, magnetic resonance assessment experiments were conducted on composite insulator samples utilizing the CPMG (Carr–Purcell–Meiboom–Gill) pulse sequence. The T2 distribution provided visualizations of the T2 decay in insulator samples with different degrees of aging.

A Novel Portable Unilateral Magnetic Resonance Magnet for Noninvasive Quantification of Human Liver Fat

Fatty liver disease has become one of the common liver diseases seriously affecting people’s health and quality of life. Existing means to quantify liver fat content are usually invasive and high-cost. Our research aims to design a single-sided magnet to develop a low-cost, non-invasive, and lightweight unilateral magnetic resonance (UMR) system that can satisfy the needs for fatty liver screening and diagnosis. A novel single-sided permanent magnet with a pear-shaped magnetic field iso-surface was designed to avoid the excitation of subcutaneous tissue in the human body. The weight of the magnet was optimized to 12.9 kg, and the mean magnetic field strength of the region of interest (ROI) was 0.07 T. The radio frequency (RF) coil set, the pulse sequence, and the modeling method for measuring proton density fat fraction (PDFF) were also introduced. Experiments for phantoms and volunteers were carried out by the UMR system to verify the performance of detection. The phantom detection results show that the UMR system can effectively avoid the influence of the subcutaneous tissue part on PDFF detection, with reasonable accuracy (around 5% fat fraction error) and robustness (within 10% relative error). Compared with a conventional MRI scanner, measurement results of volunteers (around 3% fat fraction error) show the effectiveness of the UMR system for screening fatty liver diseases. The UMR system developed based on the proposed portable single-sided magnet could be a low-cost and reliable diagnostic tool for noninvasive fatty liver disease diagnosis.

Seizure outcome determinants in children after surgery for single unilateral lesions on magnetic resonance imaging: Role of preoperative ictal and interictal electroencephalography.

To determine whether an ictal electroencephalographic (EEG) recording as part of presurgical evaluation of children with a demarcated single unilateral magnetic resonance imaging (MRI) lesion is indispensable for surgical decision-making, we investigated the relationship of interictal/ictal EEG and seizure semiology with seizure-free outcome. Data were obtained retrospectively from consecutive patients (≤18 years old) undergoing epilepsy surgery with a single unilateral MRI lesion at our institution over a 6-year period. Video-telemetry EEG (VT-EEG) was classified as concordant or nonconcordant/noninformative in relation to the MRI lesion location. The odds of seizure-free outcome associated with nonconcordant versus concordant for semiology, interictal EEG, and ictal EEG were compared separately. Multivariate logistic regression was conducted to correct for confounding variables. After a median follow-up of 26 months (interquartile range=17-37.5), 73 (69%) of 117 children enrolled were seizure-free. Histopathological diagnoses included low-grade epilepsy-associated tumors, n=46 (39%); focal cortical dysplasia (FCD), n=33 (28%); mesial temporal sclerosis (MTS), n=23 (20%); polymicrogyria, n = 3 (3%); and nondiagnostic findings/gliosis, n=12 (10%). The odds of seizure freedom were lower with a nonconcordant interictal EEG (odds ratio [OR]=.227, 95% confidence interval [CI]=.079-.646, p=.006) and nonconcordant ictal EEG (OR=.359, 95% CI=.15-.878, p=.035). In the multivariate logistic regression model, factors predicting lower odds for seizure-free outcome were developmental delay/intellectual disability and higher number of antiseizure medications tried, with a nonsignificant trend for "nonconcordant interictal EEG." In the combined subgroup of patients with FCD and tumors (n=79), there was no significant relationship of VT-EEG factors and seizure outcomes, whereas in children with MTS and acquired lesions (n=25), a nonconcordant EEG was associated with poorer seizure outcomes (p=.003). An ictal EEG may not be mandatory for presurgical evaluation, particularly when a well-defined single unilateral MRI lesion has been identified and the interictal EEG is concordant.

Moisture Distribution during Water Absorption of Ordinary Portland Cement Mortars Obtained with Low-Field Unilateral Magnetic Resonance.

Moisture distribution in cement-based materials is important from the durability point of view. In the present study, a portable three-magnet array with an elliptical surface radio frequency coil was used to undertake magnetic resonance measurements of moisture content in ordinary Portland cement mortar and concrete samples. Measurements along the length of the samples during capillary water absorption produced moisture content profiles that were compared with reference profiles acquired using a magnetic resonance imaging instrument. Profiles obtained with the three-magnet array were similar in shape and in penetration depth to those acquired with magnetic resonance imaging. The correlation coefficient between the moisture content measured with both techniques was r2 = 0.97. Similar values of saturated permeability of the mortars with identical w/c ratio were computed with the Hydrus 1D software based on the moisture content profiles. Additionally, inverse Laplace transformation of the signal decays provided the water-filled pore size distribution in saturated and unsaturated regions of the samples. The three-magnet array was successfully used to acquire nuclear magnetic resonance signal from a concrete sample, which was not possible with the magnetic resonance imaging instrument using the single-point imaging technique.

The Human Muscle Size and Strength Relationship: Effects of Architecture, Muscle Force, and Measurement Location.

This study aimed to determine the best muscle size index of muscle strength by establishing if incorporating muscle architecture measurements improved the human muscle size-strength relationship. The influence of calculating muscle force and the location of anatomical cross-sectional area (ACSA) measurements on this relationship were also examined. Fifty-two recreationally active men completed unilateral isometric knee extension strength assessments and magnetic resonance imaging scans of the dominant thigh and knee to determine quadriceps femoris size variables (ACSA along the length of the femur, maximum ACSA (ACSAMAX), and volume (VOL)) and patellar tendon moment arm. Ultrasound images (two sites per constituent muscle) were analyzed to quantify muscle architecture (fascicle length, pennation angle) and, when combined with VOL (from magnetic resonance imaging), facilitated calculation of quadriceps femoris effective PCSA (EFFPCSA) as potentially the best muscle size determinant of strength. Muscle force was calculated by dividing maximum voluntary torque by the moment arm and addition of antagonist torque (derived from hamstring EMG). The associations of EFFPCSA (r = 0.685), ACSAMAX (r = 0.697), or VOL (r = 0.773) with strength did not differ, although qualitatively VOL explained 59.8% of the variance in strength, ~11%-13% greater than EFFPCSA or ACSAMAX. All muscle size variables had weaker associations with muscle force than maximum voluntary torque. The association of strength-ACSA at 65% of femur length (r = 0.719) was greater than for ACSA measured between 10%-55% and 75%-90% (r = -0.042-0.633) of femur length. In conclusion, using contemporary methods to assess muscle architecture and calculate EFFPCSA did not enhance the muscle strength-size association. For understanding/monitoring muscle size, the major determinant of strength, these findings support the assessment of muscle volume, which is independent of architecture measurements and was most highly correlated with strength.

Impact of 30 years' high-level rock climbing on the shoulder: an magnetic resonance imaging study of 31 climbers.

Rock climbers are particularly susceptible to shoulder injuries due to repetitive upper-limb movements on vertical or overhanging terrain. However, the long-term effects of prolonged climbing on the shoulder joints are still unknown. The purpose of this study was to analyze the prevalence of pain and degenerative changes in the shoulder joints after high-level rock climbing over at least 25 years. We hypothesized that specific climber-associated patterns of degeneration would be found. Thirty-one adult male high-level rock climbers were compared to an age- and sex-matched control group of 31 nonclimbers. All participants underwent a detailed interview, standardized clinical examination, and bilateral (climbers) or unilateral (nonclimbers, dominant side) magnetic resonance imaging (MRI) scans. Clinical and MRI findings of the groups were compared. The lifetime prevalence of shoulder pain in the rock climbers was 77%. The rock climbers had significantly more abnormalities in the labrum (82% vs. 52%; P = .002), long biceps tendon (53% vs. 23%; P = .006), and cartilage (28% vs. 3%; P = .005). These increased changes positively correlated with climbing intensity. There were no differences between the 2 groups with respect to rotator cuff tendon pathology (68% vs. 58%; P = .331) and acromioclavicular joint degeneration (88% vs. 90%; P = .713). Despite the increased degenerative changes in the rock climbers, their Constant score (CS) was still better than that of the nonclimbers (CS 94, interquartile range [IQR] 92-97, vs. CS 93, IQR 91-95; P = .019). Prolonged high-level rock climbing leads to a high prevalence of shoulder pain and increased degenerative changes to the labrum, long biceps tendon, and cartilage. However, it is not related to any restriction in shoulder function.

Who Can Avoid Biopsy of Magnetic Resonance Imaging-Negative Lobes without Compromising Significant Cancer Detection among Men with Unilateral Magnetic Resonance Imaging-Positive Lobes?

Objectives: To assess whether biopsy of multiparametric magnetic resonance imaging (MRI)-negative lobes can be avoided without compromising significant cancer (SC) detection among men with unilateral MRI-positive lobes. Methods: From April 2013 to April 2019, 322 men with elevated prostate-specific antigen (PSA <20 ng/mL) and unilateral MRI-positive lobes underwent targeted 4-core and systematic 14-core biopsy. MRI findings were prospectively collected and evaluated according to the Prostate Imaging-Reporting and Data System (PI-RADS) version 2, and scores ≥3 were considered positive. SC was defined as Gleason score ≥3 + 4 or maximal cancer length ≥5 mm. We developed predictive models of overall cancer and SC in MRI-negative lobes and evaluated the performance of these models. Results: Detection rates of overall cancer/SC were 69%/61% for the overall cohort, 58%/48% for MRI-positive lobes, and 36%/20% for MRI-negative lobes. Age ≥75 years, PSA density ≥0.3, and PI-RADS ≥4 were independently predictive of both overall cancer and SC in MRI-negative lobes; 1 point was assigned for each risk factor, and the predictive score was defined as the sum of points (0–3) for both overall cancer and SC. Areas under the curve of the model for overall cancer/SC were 0.67/0.71. In the decision curve analysis, the model was of value above the threshold probability of 13%/6% for detecting overall cancer/SC in MRI-negative lobes. Of 40 men with score 0, overall cancer/SC was detected in the MRI-negative lobe in 4 (10%)/1 (2.5%). Conclusion: Biopsies of MRI-negative lobes may be avoided without compromising SC detection using our predictive model.

Unilateral low-field magnetic resonance measurements of carbonation depth in unsaturated and saturated Portland cement mortars

Unilateral Nuclear Magnetic Resonance is used to characterize the carbonation depth in 0.60 w/c ratio unsaturated/saturated Portland cement mortars. A three-magnet array combined with a surface elliptical coil was utilized to obtain the Nuclear Magnetic Resonance signal at different positions along mortar samples. The T2 lifetime and signal intensity behaviors in the carbonated and non-carbonated zones were analyzed. Scanning Electron Microscopy images were used to identify the macro-porosity and micro-cracking in the samples. Results confirmed that the crossover point between profiles of T2 lifetime and signal intensity agree with the carbonation depth obtained by the phenolphthalein test. The carbonation depth at the position where the T2 lifetime begins to behave nearly constant is about 1.44 times the depth indicated by the phenolphthalein test. The spatial resolution was improved four times in comparison with previous research. Scanning Electron Microscopy images analysis confirmed a significant decrease in local porosity and crack area in the carbonated zone.

Optimized Portable Unilateral Magnetic Resonance Sensor for Assessing the Aging Status of Silicon Rubber Insulators

Silicone rubber insulators (SRIs) play an important role in high-voltage power transmission lines. Given that SRIs critically threaten the safe operation of the power grid, quantitatively assessing the aging status of SRIs in situ is crucial. In this article, a portable unilateral magnetic resonance (UMR) sensor with a U-shaped magnet structure and its measuring circuit were designed for the nondestructive detection of the aging status of SRIs in situ. First, the optimization efficiency of the magnet structure was improved through a uniform design method. Then, the planar radio frequency (RF) coil was designed by the finite-element method. Furthermore, the demagnetization effect of eddy currents induced in metal materials on the RF magnetic field was analyzed. We measured the SRI sheds at different service times and obtained the corresponding 1H transverse relaxation decay curves by importing the Carr- Purcell-Meiboom-Gill (CPMG) sequence. Finally, the transverse relaxation decay curves were postprocessed using inverse Laplace transformation, and the 1-D spectrum distributions of transverse relaxation time (T2) were obtained. The results reveal that T2 of the surface of the SRI shed decreases as the service time of the SRI increases. In addition, the difference in T2 between the surface and interior of the SRI shed increases. The comparison experiments demonstrate that the U-shaped sensor designed in this article is superior to the curved sensor previously designed by our team. The effect of temperature variation on SRIs aging assessment was considered at last.

Arc gradient coils design for unilateral magnetic resonance sensor based on Fourier series method

Arc gradient coils design for unilateral magnetic resonance sensor based on Fourier series method

Non-ketotic Hyperglycaemic Hemichorea with Unilateral Magnetic Resonance Imaging Putaminal Hyperintensity

Non-ketotic Hyperglycaemic Hemichorea with Unilateral Magnetic Resonance Imaging Putaminal Hyperintensity

NMR CAPIBarA: Proof of Principle of a Low-Field Unilateral Magnetic Resonance System for Monitoring of the Placenta during Pregnancy

A growing body of literature shows that the transverse relaxation times of the placenta change during pregnancy and may be an early indicator of disease. Magnetic resonance imaging (MRI) of pregnant women is not, however, currently used frequently despite this evidence. One significant barrier to adoption is the cost of undertaking an MRI scan and the over utilization of existing equipment. Low-field nuclear magnetic resonance (NMR) offers a low-cost alternative, capable of measuring transverse relaxation in a single point in space. Ultrasound imaging (US) is routinely used at several points during pregnancy but is not capable of early detection of pre-eclampsia, for example. It does, however, provide a technique that is capable of locating the placenta with ease. In combination with a single point low-field measurement, localised with ultrasound imaging allows access to this exciting technique without the need for an expensive traditional MRI. In this work, we present a unilateral system (NMR CAPIBarA), operating at a magnetic field of only 18mT, which measures transverse relaxation times at distances from its surface equivalent to the positioning of a human placenta. Data are presented to characterise the system using relation time standards covering the full transverse relaxation time range relevant for the developing placenta, which are also measured on a 1.5 T clinical MRI scanner.

Portable Unilateral NMR Measuring System for Assessing the Aging Status of Silicon Rubber Insulators

Silicon rubber insulators (SRIs) are widely used in power transmission lines as line support and as insulation between the line and the tower. Given that the aging of SRIs threatens the safety and stability of power grids, the accurate assessment of the aging status of SRIs is crucial. In this study, a portable unilateral magnetic resonance (UMR) measuring system for the nondestructive testing of the aging status of SRIs was proposed. The proposed NMR measurement system includes a mini UMR sensor and a measurement circuit. Details of the mini UMR sensor structure and low-cost circuit design were discussed. The Carr–Purcell–Meiboom–Gill sequence was used to record the 1H transverse relaxation curves of SRI sheds. Inverse Laplace transformation was employed to obtain the T2 distribution, and two peaks in the T2 distribution curve were observed. The long T2 component was selected to quantify the aging degree because of its stability compared with the short T2 component. To eliminate the inaccuracy of measurement introduced by the different chemical structures of SRIs produced by different companies, the aging status of the SRIs was represented by the changes in T2 between the surface and internal materials of the SRI.

Biportal Endoscopic Decompression of Exiting and Traversing Nerve Roots Through a Single Interlaminar Window Using a Contralateral Approach: Technical Feasibilities and Morphometric Changes of the Lumbar Canal and Foramen

Endoscopic surgery for lumbar stenosis is gaining acceptance because of the minimal muscle damage, short recovery times, reduced blood loss, and good clinical results. We report a novel technique of decompressing contralateral traversing and exiting nerve roots through a single interlaminar window, avoiding separate incision for foraminal decompression with minimal damage to facet joints and comparing morphometric changes after decompression. Between March and December 2017, 30 patients were evaluated retrospectively for clinical, radiologic, and morphometric outcomes. Patients with unilateral radiculopathy and magnetic resonance imaging (MRI) showing spinal stenosis at 2 levels (lateral recess and cranial level foraminal compression) were included. Clinical evaluation used a numerical rating scale (NRS) for leg pain and Oswestry Disability Index (ODI) scores, and radiologic evaluation used MRI. For morphometric analysis, the cross-sectional area of the intervertebral foramen (CSA-IVF), spinal canal (CSAC), and facet joint (CSA-FJ) was measured on MRI. Thirty levels were decompressed (no adverse events). NRS leg pain and ODI scores improved from 7.5±0.86 and 67.9 ± 9.7 preoperatively to 1.53 ± 0.86 and 15.7 ± 6.6 at last follow-up, respectively. CSAC improved from 99.34 ± 34.01 to 186.83 ± 41.41, indicating good canal decompression. CSA-IVF improved from 56.40 ± 19.28 to 97.60 ± 28.46, indicating good foraminal decompression. CSA-FJ improved from 231.37 ± 62.53 to 194.96 ± 50.56, indicating good foraminal decompression with less damage to facet joint. Morphometric changes were statistically significant (P < 0.05). Biportal endoscopic decompression of the lateral recess and cranial foramen through a single interlaminar window can be performed using a contralateral approach. In view of the good clinical and radiologic outcomes of patients, with notable improvements in morphometric measurements at stenosed segments, this surgical technique is worthy of further evaluation and application.