Developing research skills in medical students online using an active research study.

BACKGROUND: Developing research skills and scholarship are key components of medical education. The COVID-19 pandemic necessitated that all teaching be delivered online. We introduced an approach to small group teaching in the academic year 2020-2021 online which involved students in an active (ongoing) research study to develop their research skills. METHODS: We acquired student feedback to evaluate their perspectives quantitatively on development of research and scholarship skills, teaching content and format, and tutor performance using this teaching approach. In addition, we captured free text responses from both students and tutors on the positives and negatives of our course, and their suggested improvements. We also compared summative assessment marks for the online/active research course (2020-2021) with those obtained from previous (2017-2019) and subsequent (2021-2023) teaching sessions. RESULTS: Students were largely positive about most aspects of the online course utilising an active research study (n = 13). Students agreed that they were able to acquire research skills, particularly related to data analysis, transferable skills, and giving scientific presentations. A one-way ANOVA revealed no significant difference for assessment marks across all five teaching years (two years prior and two years following the online/active research course), indicating that the course achieved the learning outcomes. Students enjoyed the convenience of online teaching and the availability of course resources, but least liked the lack of in-person interaction and laboratory training. Tutors enjoyed the collaborative aspects of online teaching, but least liked the lack of face-to-face interactions with students. CONCLUSIONS: Our study demonstrates that delivering online teaching which involves students in active research engages and motivates them to develop their research and scholarship skills. We recommend that educators consider incorporating a current research study in their undergraduate courses as this can enhance the student learning experience as well as the research project itself.

A comparative experimental study of visual brain event-related potentials to a working memory task: virtual reality head-mounted display versus a desktop computer screen.

Virtual reality head mounted display (VR HMD) systems are increasingly utilised in combination with electroencephalography (EEG) in the experimental study of cognitive tasks. The aim of our investigation was to determine the similarities/differences between VR HMD and the computer screen (CS) in response to an n-back working memory task by comparing visual electrophysiological event-related potential (ERP) waveforms (N1/P1/P3 components). The same protocol was undertaken for VR HMD and CS with participants wearing the same EEG headcap. ERP waveforms obtained with the VR HMD environment followed a similar time course to those acquired in CS. The P3 mean and peak amplitudes obtained in VR HMD were not significantly different to those obtained in CS. In contrast, the N1 component was significantly higher in mean and peak amplitudes for the VR HMD environment compared to CS at the frontal electrodes. Significantly higher P1 mean and peak amplitudes were found at the occipital region compared to the temporal for VR HMD. Our results show that successful acquisition of ERP components to a working memory task is achievable by combining VR HMD with EEG. In addition, the higher amplitude N1/P1 components seen in VR HMD indicates the potential utility of this VR modality in the investigation of early ERPs. In conclusion, the combination of VR HMD with EEG/ERP would be a useful approach to advance the study of cognitive function in experimental brain research.

Multiplexed ion beam imaging (MIBI) for characterization of the tumor microenvironment across tumor types.

An ability to characterize the cellular composition and spatial organization of the tumor microenvironment (TME) using multiplexed IHC has been limited by the techniques available. Here we show the applicability of multiplexed ion beam imaging (MIBI) for cell phenotype identification and analysis of spatial relationships across numerous tumor types. Formalin-fixed paraffin-embedded (FFPE) samples from tumor biopsies were simultaneously stained with a panel of 15 antibodies, each labeled with a specific metal isotope. Multi-step processing produced images of the TME that were further segmented into single cells. Frequencies of different cell subsets and the distributions of nearest neighbor distances between them were calculated using this data. A total of 50 tumor specimens from 15 tumor types were characterized for their immune profile and spatial organization. Most samples showed infiltrating cytotoxic T cells and macrophages present amongst tumor cells. Spatial analysis of the TME in two ovarian serous carcinoma images highlighted differences in the degree of mixing between tumor and immune cells across samples. Identification of admixed PD-L1+ macrophages and PD-1+ T cells in an urothelial carcinoma sample allowed for the detailed observations of immune cell subset spatial arrangement. These results illustrate the high-parameter capability of MIBI at a sensitivity and resolution uniquely suited to understanding the complex tumor immune landscape including the spatial relationships of immune and tumor cells and expression of immunoregulatory proteins.

A within-coil optical prospective motion-correction system for brain imaging at 7T.

PURPOSE: Motion artifact limits the clinical translation of high-field MR. We present an optical prospective motion correction system for 7 Tesla MRI using a custom-built, within-coil camera to track an optical marker mounted on a subject. METHODS: The camera was constructed to fit between the transmit-receive coils with direct line of sight to a forehead-mounted marker, improving upon prior mouthpiece work at 7 Tesla MRI. We validated the system by acquiring a 3D-IR-FSPGR on a phantom with deliberate motion applied. The same 3D-IR-FSPGR and a 2D gradient echo were then acquired on 7 volunteers, with/without deliberate motion and with/without motion correction. Three neuroradiologists blindly assessed image quality. In 1 subject, an ultrahigh-resolution 2D gradient echo with 4 averages was acquired with motion correction. Four single-average acquisitions were then acquired serially, with the subject allowed to move between acquisitions. A fifth single-average 2D gradient echo was acquired following subject removal and reentry. RESULTS: In both the phantom and human subjects, deliberate and involuntary motion were well corrected. Despite marked levels of motion, high-quality images were produced without spurious artifacts. The quantitative ratings confirmed significant improvements in image quality in the absence and presence of deliberate motion across both acquisitions (P < .001). The system enabled ultrahigh-resolution visualization of the hippocampus during a long scan and robust alignment of serially acquired scans with interspersed movement. CONCLUSION: We demonstrate the use of a within-coil camera to perform optical prospective motion correction and ultrahigh-resolution imaging at 7 Tesla MRI. The setup does not require a mouthpiece, which could improve accessibility of motion correction during 7 Tesla MRI exams.

Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia.

GUIDELINE SUMMARY: Chronic limb-threatening ischemia (CLTI) is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG) are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD) in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI) is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR) hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP) and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen) has not been established. Regenerative medicine approaches (eg, cell, gene therapies) for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative.

Clinical course of abdominal aortic aneurysms in Behçet disease: a retrospective analysis.

Arterial aneurysms are rare manifestations of Behçet Disease (BD) with high morbidity and mortality. This study aimed to investigate the clinical course of BD patients with abdominal aortic aneurysms (AAA). We retrospectively searched charts of BD patients, followed up between 1988 and 2011, to identify those with AAA with at least 6-month clinical and radiological follow-up data. Chart review revealed 12 patients (11 males) with AAA amongst 1224 patients; follow-up data from 11 patients were available. The most common symptoms were lower back and abdominal pain. The only pre-treatment complication was a spontaneous rupture. All but one patient received corticosteroid and cyclophosphamide pulses for the induction, and corticosteroid and azathioprine for the maintenance treatment; one patient received only the maintenance treatment. Two patients had surgical graft interposition, without postoperative complications. Seven patients had endovascular stenting; five of them (71.4%) showed radiological regression after 32.5 (13.4-53.8) months, while four (57%) had clinical improvement after 11.8 (0.2-29.4) months. However, one non-responsive patient developed stent infection and exsanguinated during percutaneous drainage, and one patient developed femoral artery pseudo-aneurysm at the catheter insertion site. Another patient developed a new aneurysm under the maintenance treatment. Medical treatment alone yielded radiological regression in one of two patients. Current immunosuppressive, surgical or endovascular approaches can provide clinical and radiological improvements lately in BD patients with AAA. Furthermore, complication rates seem to be high with interventional approaches. These findings suggest an unmet need for safer alternative treatments.

Prospective motion correction using coil-mounted cameras: Cross-calibration considerations.

PURPOSE: Optical prospective motion correction substantially reduces sensitivity to motion in neuroimaging of human subjects. However, a major barrier to clinical deployment has been the time-consuming cross-calibration between the camera and MRI scanner reference frames. This work addresses this challenge. METHODS: A single camera was mounted onto the head coil for tracking head motion. Two new methods were developed: (1) a rapid calibration method for camera-to-scanner cross-calibration using a custom-made tool incorporating wireless active markers, and (2) a calibration adjustment method to compensate for table motion between scans. Both methods were tested at 1.5T and 3T in vivo. Simulations were performed to determine the required mechanical tolerance for repositioning of the camera. RESULTS: The rapid calibration method is completed in a short (<30 s) scan, which is carried out only once per installation. The calibration adjustment method requires no extra scan time and runs automatically whenever the system is used. The mechanical tolerance analysis indicates that most motion (90% reduction in voxel displacement) could be corrected even with far larger camera repositioning errors than are observed in practice. CONCLUSION: The methods presented here allow calibration of sufficient quality to be carried out and maintained with no additional technologist workload. Magn Reson Med 79:1911-1921, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Cutaneous analgesia before transradial access for coronary intervention to prevent radial artery spasm.

AIM: Transradial access (TRA) for coronary intervention is increasingly used in current clinical practice. The aim of the present study was to evaluate the hypothesis that cutaneous analgesia before TRA for coronary intervention at a puncture site 30 minutes before puncture can reduce patient discomfort and the incidence of radial artery spasm (RAS). METHODS: Patients (n=104) undergoing planned coronary interventions using TRA were prospectively randomized to receive either 1 mL of 1% lidocaine subcutaneously (n=52) (control group) or subcutaneous lidocaine plus 5% lidocaine cream (n=52) cutaneously 30 minutes before puncture (treatment group). The primary endpoint was angiographically or clinically confirmed RAS. Secondary endpoints were the occurrence of patient discomfort in the forearm during the procedure and access-site crossover to the femoral artery. Patient discomfort was quantified with a visual analogue scale (VAS) score. RESULTS: Fifty-two patients in the treatment group (60.5±9.4 years of age and 16 female) and 52 patients in the control group (60.4±9.7 years of age and 16 female) were included in the final analysis. Radial artery spasm occurrence decreased in the treatment group compared to the control group (26.9% vs 9.6%; p=0.04) accompanied by a VAS score of 3.7±1.8 in the treatment group and 4.9±2.0 in the control group; p=0.02. The access site crossover rate did not differ between the groups (7.6% vs 21.1%; p=0.09). CONCLUSION: Cutaneous analgesia before TRA for coronary interventions is associated with a substantial reduction in the RAS and the procedure-related level of patient discomfort.

Extended hybrid-space SENSE for EPI: Off-resonance and eddy current corrected joint interleaved blip-up/down reconstruction.

INTRODUCTION: Geometric distortions along the phase encode direction caused by off-resonant spins are still a major issue in EPI based functional and diffusion imaging. If the off-resonance map is known it is possible to correct for distortions. Most correction methods operate as a post-processing step on the reconstructed magnitude images. THEORY AND METHODS: Here, we present an algebraic reconstruction method (hybrid-space SENSE) that incorporates a physics based model of off-resonances, phase inconsistencies between k-space segments, and T2*-decay during the acquisition. The method can be used to perform a joint reconstruction of interleaved acquisitions with normal (blip-up) and inverted (blip-down) phase encode direction which results in reduced g-factor penalty. RESULTS: A joint blip-up/down simultaneous multi slice (SMS) reconstruction for SMS-factor 4 in combination with twofold in-plane acceleration leads to a factor of two decrease in maximum g-factor penalty while providing off-resonance and eddy-current corrected images. CONCLUSION: We provide an algebraic framework for reconstructing diffusion weighted EPI data that in addition to the general applicability of hybrid-space SENSE to 2D-EPI, SMS-EPI and 3D-EPI with arbitrary k-space coverage along z, allows for a modeling of arbitrary spatio-temporal effects during the acquisition period like off-resonances, phase inconsistencies and T2*-decay. The most immediate benefit is a reduction in g-factor penalty if an interleaved blip-up/down acquisition strategy is chosen which facilitates eddy current estimation and ensures no loss in k-space encoding in regions with strong off-resonance gradients.

Trade-off between angular and spatial resolutions in in vivo fiber tractography.

Tractography is becoming an increasingly popular method to reconstruct white matter connections in vivo. The diffusion MRI data that tractography is based on requires a high angular resolution to resolve crossing fibers whereas high spatial resolution is required to distinguish kissing from crossing fibers. However, scan time increases with increasing spatial and angular resolutions, which can become infeasible in clinical settings. Here we investigated the trade-off between spatial and angular resolutions to determine which of these factors is most worth investing scan time in. We created a unique diffusion MRI dataset with 1.0 mm isotropic resolution and a high angular resolution (100 directions) using an advanced 3D diffusion-weighted multi-slab EPI acquisition. This dataset was reconstructed to create subsets of lower angular (75, 50, and 25 directions) and lower spatial (1.5, 2.0, and 2.5 mm) resolution. Using all subsets, we investigated the effects of angular and spatial resolutions in three fiber bundles-the corticospinal tract, arcuate fasciculus and corpus callosum-by analyzing the volumetric bundle overlap and anatomical correspondence between tracts. Our results indicate that the subsets of 25 and 50 directions provided inferior tract reconstructions compared with the datasets with 75 and 100 directions. Datasets with spatial resolutions of 1.0, 1.5, and 2.0 mm were comparable, while the lowest resolution (2.5 mm) datasets had discernible inferior quality. In conclusion, we found that angular resolution appeared to be more influential than spatial resolution in improving tractography results. Spatial resolutions higher than 2.0 mm only appear to benefit multi-fiber tractography methods if this is not at the cost of decreased angular resolution.

Altered Plasma MicroRNA Expression in Patients with Mitral Chordae Tendineae Rupture.

BACKGROUND: Mitral chordae tendineae rupture (MCTR) is a progressive disorder which leads to severe mitral regurgitation. Despite its importance, the precise pathogenetic mechanism of MCTR remains unclear. The study aim was to investigate the expression profile of circulating microRNAs (miRNAs) as being potentially involved in the development of MCTR. METHODS: Twenty-one patients with 'primary' MCTR, and 30 age- and gender-matched controls, were enrolled in the study. Comparisons were made between the expression levels of circulating miRNAs in MCTR patients and controls. Four target gene databases were used to predict target genes and pathways of differentially expressed miRNAs. RESULTS: Compared to controls, the expression of 22 miRNAs (hsa-miR-106b-5p, hsa-miR-126-3p, hsa-miR-150-5p, hsa-miR-17-5p, hsa-miR-195-5p, hsa-miR-19a-3p, hsa-miR-19b-3p, hsa-miR-20a-5p, hsa-miR-21-5p, hsa-miR-222-3p, hsa-miR-223-3p, hsa-miR-23a-3p, hsa-miR-25-3p, hsa-miR-92a-3p, hsa-miR-93-5p, hsa-miR-26b-5p, hsa-miR-30e-5p, hsa-miR-373-3p, hsa-miR-15b-5p, hsa-miR-16-5p, hsa-miR-191-5p, hsa-miR-26a-5p) were significantly down-regulated in the MCTR group. Bioinformatic analysis indicated that the following potential miRNA targets and pathways are commonly related to the development of MCTR: MMPs, TIMP-2,TGFBR2, VEGFA, PIK3R2, NRAS, PPP3CA, PPP3R1, PTGS 2 were predicted as putative targets of 13 of these miRNAs. CONCLUSIONS: The present study is the first to describe altered miRNA expression in patients with MCTR. Bioinformatic analysis has revealed that target genes involved in MCTR development were regulated by miRNAs.

Volume depletion provided by blood donation alters twist mechanics of the heart: Preload dependency of left ventricular torsion.

OBJECTIVES: The crucial role of twisting motion on both left ventricular (LV) contraction and relaxation has been clearly identified. However, the reports studying the association between LV torsion and loading conditions have revealed conflicting outcomes. Previously normal saline infusion was shown to increase LV rotation. Our aim was to test this phenomenon after volume depletion in healthy volunteer blood donors. DESIGN: A total of 26 healthy male volunteers were included in the study. LV end-diastolic and end-systolic diameter, LV ejection fraction, LV diastolic parameters, LV apical and basal rotation and peak systolic LV torsion were measured by speckle-tracking echocardiography before and after 450 mL blood donation. RESULTS: Blood donation led to a significant decrease in end-diastolic LV internal diameter (48.7 ± 0.4 versus 46.4 ± 0.4 mm; p < 0.001) and cardiac output (6.2 ± 1.0 versus 5.1 ± 0.7 L/min; p < 0.001). There was a significant decrease in the magnitude of peak systolic apical rotation (4.4 ± 1.9° versus 2.9 ± 1.5°; p < 0.001) but no change in basal rotation (2.6 ± 1.4° versus 2.7 ± 1.6°; p = 0.81). Peak systolic LV Torsion decreased after blood donation (6.9 ± 1.9° versus 5.7 ± 2.1°; p = 0.028). CONCLUSIONS: LV apical rotation and peak systolic LV torsion seem to be preload dependent. Preload reduction provided by 450-mL blood donation decreased LV torsion in healthy male volunteers. Volume dynamics should be taken into account in the evaluation of LV torsion.

Percutaneous approach to the treatment of a totally occluded abdominal aortic stent graft.

Aorto femoral bypass is usually the recommended therapy for diffuse disease involving the aorta and iliac arteries. In this case report, a case involving a chronic endovascular abdominal aortic stent graft occlusion in which percutaneous angioplasty was performed via a transbrachial and transfemoral approach is presented. This case emphasized that occlusion of an endovascular abdominal aortic stent graft can also be treated, primarily, with an endovascular technique.

Predictors of periprocedural complications of carotid artery stenting - a multivariate analysis of a single-centre experience.

BACKGROUND: Carotid artery stenting (CAS) is currently used as an alternative treatment to carotid endarterectomy (CEA). The objective of this study was to analyse our 5-year experience performing CAS. Secondarily, we sought to determine independent risk factors which predict periprocedural complications. PATIENTS AND METHODS: A total of 146 patients who underwent 153 CAS procedures were analysed. The majority of patients (123, 84.2%) had symptomatic carotid stenosis. Demographic and interventional data, angiographic lesion characteristics, and periprocedural complications were recorded. Using univariate and multivariate logistic regression analyses, risk factors associated with adverse clinical outcomes were determined. RESULTS: Periprocedural neurological complications, including four (2.7 %) major strokes, three (2 %) transient ischaemic attacks, one (0.7%) amaurosis fugax, and two (1.3 %) cases of hyperperfusion syndrome occurred in ten (6.8%) patients. The incidence of periprocedural complications significantly increased in female patients (r = 0.214, p = 0.009) and patients with longer lesions (r = 0.183, p = 0.027), contralateral stenosis ≥50 % (r = 0.222, p = 0.007), the presence of complicated plaques (r = 0.478, p < 0.001) and inadequate glycaemic control (r = 0.259, p = 0.002). Multivariate regression analysis also determined four variables to be potential independent risk factors for 30-day adverse events: higher age (Odds ratio [OR] = 1.283; 95 % CI, 1.051 to 1.566, p = 0.014); longer lesions (OR = 1.459, 95 % CI, 1.124 to 1.893, p = 0.004); higher tortuosity index (OR = 1.015, 95 % CI, 1.001 to 1.030, p = 0.034), and the presence of complicated plaque morphology (OR = 4.321, 95 % CI, 1.621 to 10.23, p = 0.001). CONCLUSIONS: Patient and lesion characteristics including age, lesion length, complicated plaque morphology and tortuosity index, may be associated with periprocedural complications.

Echocardiographic Evaluation of Biventricular Function in Patients with Euthyroid Hashimoto's Thyroiditis.

OBJECTIVE: The aim of this study was to evaluate the left (LV) and right (RV) ventricular function in euthyroid Hashimoto's thyroiditis (eHT) patients. SUBJECTS AND METHODS: Forty-five patients diagnosed with eHT and 45 age- and gender-matched control subjects were enrolled in this study. Echocardiographic parameters reflecting RV and LV functions such as chamber dimensions, ejection fraction, fractional shortening, conventional and tissue Doppler-derived early and late filling velocities (E, A, E', A'), isovolumic relaxation (IVRT) and contraction (IVCT) times, ejection time (ET), deceleration time (DT), Tei index, pulmonary acceleration time (PAcT) and tricuspid annular plane systolic excursion (TAPSE) of patients with eHT were compared to those of control subjects using the paired-samples t test or Wilcoxon signed-rank test. RESULTS: Regarding the LV function, compared to the controls patients with eHT had a higher LV-Tei index (0.6 ± 0.2 vs. 0.4 ± 0.1, p < 0.001), higher DT (p < 0.001) and IVRT (p < 0.001) values, and higher E/E' ratios (p = 0.04). In contrast, the peak E wave velocity (p = 0.02), E/A ratio (p = 0.01) and ET (p = 0.02) were significantly lower in the eHT group than amongst the controls. The RV, Tei index (0.40 ± 0.11 vs. 0.28 ± 0.07, p < 0.001), TAPSE (2.0 ± 0.3 vs. 2.2 ± 0.2 mm, p < 0.001), PAcT (124.3 ± 22.6 vs. 149.4 ± 18.3 ms, p < 0.001), A' (p = 0.007) and IVCT (p = 0.001) were significantly higher in patients with eHT than the controls. However, the tricuspid E/A ratio (p = 0.01), E' (p = 0.03) and E'/A' ratio (p = 0.001) were significantly lower in the eHT patients than the control group. CONCLUSIONS: This study demonstrated that both RV and LV functions were impaired in patients with eHT.

Perchlorate Exposure Through Water and Milk in Istanbul.

Perchlorate is a chemical pollutant that inhibits iodide uptake and may possibly impair thyroid function. Our previous study found widespread perchlorate exposure in non-pregnant, non-lactating, healthy women residing in Istanbul. The aim of this study is to assess the relative amounts of perchlorate exposure attributable to consumption of municipal water, bottled water and boxed milk available in Istanbul. Only trace levels of perchlorate were found in treated municipal water (58 % detectable, mean = 0.13 µg/L, maximum = 0.75 µg/L) and bottled water (7.4 % detectable, mean = 

Contact-free physiological monitoring using a markerless optical system.

PURPOSE: Physiological noise remains a major problem in MRI, particularly at higher imaging resolutions and field strengths. The aim of this work was to investigate the feasibility of using an MR-compatible in-bore camera system to perform contactless monitoring of cardiac and respiratory information during MRI of human subjects. METHODS: An MR-compatible camera was mounted on an eight-channel head coil. Video data of the skin was processed offline to derive cardiac and respiratory signals from the pixel signal intensity and from head motion in the patient head-feet direction. These signals were then compared with data acquired simultaneously from the pulse oximeter and the respiratory belt. RESULTS: The cardiac signal computed using the average image pixel intensity closely resembled the signal obtained using the pulse oximeter. Trigger intervals obtained from both systems matched to within 50 ms (one standard deviation). The respiratory signal computed from small in-plane movements closely matched the signal obtained from the respiratory belt. Simultaneous MR imaging did not appear to have an effect on the physiological signals acquired by means of the contact-free monitoring system. CONCLUSION: Contact-free monitoring of human subjects to obtain cardiac and respiratory information is feasible using a small camera and light emitting diode mounted on the head coil of an MRI scanner.

Real-time correction of rigid body motion-induced phase errors for diffusion-weighted steady-state free precession imaging.

PURPOSE: Diffusion contrast in diffusion-weighted steady-state free precession magnetic resonance imaging (MRI) is generated through the constructive addition of signal from many coherence pathways. Motion-induced phase causes destructive interference which results in loss of signal magnitude and diffusion contrast. In this work, a three-dimensional (3D) navigator-based real-time correction of the rigid body motion-induced phase errors is developed for diffusion-weighted steady-state free precession MRI. METHODS: The efficacy of the real-time prospective correction method in preserving phase coherence of the steady state is tested in 3D phantom experiments and 3D scans of healthy human subjects. RESULTS: In nearly all experiments, the signal magnitude in images obtained with proposed prospective correction was higher than the signal magnitude in images obtained with no correction. In the human subjects, the mean magnitude signal in the data was up to 30% higher with prospective motion correction than without. Prospective correction never resulted in a decrease in mean signal magnitude in either the data or in the images. CONCLUSIONS: The proposed prospective motion correction method is shown to preserve the phase coherence of the steady state in diffusion-weighted steady-state free precession MRI, thus mitigating signal magnitude losses that would confound the desired diffusion contrast.

Slab profile encoding (PEN) for minimizing slab boundary artifact in three-dimensional diffusion-weighted multislab acquisition.

PURPOSE: To propose a method for mitigating slab boundary artifacts in three-dimensional (3D) multislab diffusion imaging with no or minimal increases in scan time. METHODS: The multislab acquisition was treated as parallel imaging acquisition where the slab profiles acted as the traditional receiver sensitivity profiles. All the slabs were then reconstructed simultaneously along the slab direction using Cartesian-based sensitivity encoding (SENSE) reconstruction. The slab profile estimation was performed using either a Bloch simulation or a calibration scan. RESULTS: Both phantom and in vivo results showed negligible slab boundary artifacts after reconstruction using the proposed method. The performance of the proposed method is comparable to the state-of-the-art slab combination method without the scan time penalty that depends on the number of acquired volumes. The obtained g-factor map of the SENSE reconstruction problem showed a maximum g-factor of 1.7 in the region of interest. CONCLUSION: We proposed a novel method for mitigating slab boundary artifacts in 3D diffusion imaging by treating the multislab acquisition as a parallel imaging acquisition and reconstructing all slabs simultaneously using Cartesian SENSE. Unlike existing methods, the scan time increase, if any, does not scale with the number of image volumes acquired.