Reliability of spinal cord measures based on synthetic T1_{1}-weighted MRI derived from multiparametric mapping (MPM)

Short MRI acquisition time, high signal-to-noise ratio, and high reliability are crucial for image quality when scanning healthy volunteers and patients. Cross-sectional cervical cord area (CSA) has been suggested as a marker of neurodegeneration and potential outcome measure in clinical trials and is conventionally measured on T$_{1}$-weigthed 3D Magnetization Prepared Rapid Acquisition Gradient-Echo (MPRAGE) images. This study aims to reduce the acquisition time for the comprehensive assessment of the spinal cord, which is typically based on MPRAGE for morphometry and multi-parameter mapping (MPM) for microstructure. The MPRAGE is replaced by a synthetic T$_{1}$-w MRI (synT$_{1}$-w) estimated from the MPM, in order to measure CSA. SynT$_{1}$-w images were reconstructed using the MPRAGE signal equation based on quantitative maps of proton density (PD), longitudinal (R$_{1}$) and effective transverse (R$_{2}$*) relaxation rates. The reliability of CSA measurements from synT$_{1}$-w images was determined within a multi-center test-retest study format and validated against acquired MPRAGE scans by assessing the agreement between both methods. The response to pathological changes was tested by longitudinally measuring spinal cord atrophy following spinal cord injury (SCI) for synT$_{1}$-w and MPRAGE using linear mixed effect models. CSA measurements based on the synT$_{1}$-w MRI showed high intra-site (Coefficient of variation [CoV]: 1.43% to 2.71%) and inter-site repeatability (CoV: 2.90% to 5.76%), and only a minor deviation of -1.65 mm$^{2}$ compared to MPRAGE. Crucially, by assessing atrophy rates and by comparing SCI patients with healthy controls longitudinally, differences between synT$_{1}$-w and MPRAGE were negligible. These results demonstrate that reliable estimates of CSA can be obtained from synT$_{1}$-w images, thereby reducing scan time significantly

hMRI - A toolbox for quantitative MRI in neuroscience and clinical research

Neuroscience and clinical researchers are increasingly interested in quantitative magnetic resonance imaging (qMRI) due to its sensitivity to micro-structural properties of brain tissue such as axon, myelin, iron and water concentration. We introduce the hMRI-toolbox, an open-source, easy-to-use tool available on GitHub, for qMRI data handling and processing, presented together with a tutorial and example dataset. This toolbox allows the estimation of high-quality multi-parameter qMRI maps (longitudinal and effective transverse relaxation rates and , proton density and magnetisation transfer saturation) that can be used for quantitative parameter analysis and accurate delineation of subcortical brain structures. The qMRI maps generated by the toolbox are key input parameters for biophysical models designed to estimate tissue microstructure properties such as the MR g-ratio and to derive standard and novel MRI biomarkers. Thus, the current version of the toolbox is a first step towards in vivo histology using MRI (hMRI) and is being extended further in this direction. Embedded in the Statistical Parametric Mapping (SPM) framework, it benefits from the extensive range of established SPM tools for high-accuracy spatial registration and statistical inferences and can be readily combined with existing SPM toolboxes for estimating diffusion MRI parameter maps. From a user's perspective, the hMRI-toolbox is an efficient, robust and simple framework for investigating qMRI data in neuroscience and clinical research

A travelling heads study investigating qMRI metrics on cortical regions

Technological advances in magnetic resonance imaging (MRI) have facilitated numerous studies on neural architecture, such as studies addressing pathology, behaviour or individual differences in brain activity. It is important, however, to first ascertain what variation can arise due to site-specific scanner properties (hard- and software). A certain amount of noise in MR images can indeed be attributable to such properties, even when the same scanner is used across different sites. Reproducibility across sites is possible with the use of quantitative MRI metrics (qMRI), where physical properties assigned to voxels allow for non-invasive analysis of brain tissue including sensitivity to iron and myelin content. Leutritz et al. (2020) investigated intra-site (scan-rescan) and intersite (between sites) variability on Siemens and Philips scanners through multi-parameter mapping techniques (MPM). The authors found intra-site scan-rescan coefficients of variance (CoV) ranging between 4% and 16% across parameters, with similar results for inter-site CoV. The current study implements a similar strategy to Leutritz et al. (2020) in that it investigates inter-site and interscanner variability in a "travelling heads" type of study. Using scanners by the same manufacturer (but two different models), the study investigates qMRI metrics for inter-site and inter-scanner differences and their corresponding effects on cortical regions.peer-reviewe

Ursachenaufklärung des MRT-Phasenkontrastes im Hochfeld mit Bezug auf die Wasser-Makromolekül-Wechselwirkung

von Tobias Leutrit

Combatting the occurrence of needle-stick injuries in a medical school: why is it still an issue?

Abstract Background Needle-stick injuries (NSIs) pose a safety risk for healthcare workers with great potential for serious infections. The aim was to determine numbers and causes of NSIs as well as the frequency with which medical students report NSIs in the final stages of study. Methods An online questionnaire was developed and made available in January and February 2023 to all undergraduate medical students (n = 423) in the last 1.5 years of their degree course at Würzburg University, Germany. Results The response rate was 19.6% (n = 84). Among respondents, 27.4% (n = 23) reported at least one NSI. Occurrence was particularly frequent in surgery, obstetrics and gynaecology, and internal medicine. Assisting with procedures, suturing, and blood sampling were considered high-risk activities. Lack of concentration, distraction, and time pressure played a role in incidents. Respondents did not report 18.8% of NSIs with the main reasons being fear of the consequences, self-assessment of the injury as minor, or the opinion of supervisors that reporting was unnecessary. Students with previous practice on simulators or patients were significantly more likely to suffer NSIs. Instructions from occupational health specialists beforehand correlated with fewer NSIs. Conclusion We assume that trained students are more experienced in handling invasive procedures, leading to a greater adoption of corresponding activities and thus an increased risk of injuries in absolute numbers. This does not counter the need for didactic interventions prior to workplace-based training to raise awareness of NSI risks. Simultaneously, concepts must be developed and implemented to support reporting and alleviate fears regarding consequences

Factors associated with medical students’ career choice in different specialties: a multiple cross-sectional questionnaire study at a German medical school

Abstract Background Given the shortage and unequal distribution of physicians across specialties, we aimed to evaluate factors associated with medical students’ career choices, including background, personality traits, educational experience, personal interests, lifestyle considerations, and the awareness of work requirements. Methods We conducted multiple cross-sectional surveys of students; a 159-item online questionnaire was designed and students from three different stages of the six-year medical degree course (outset, clinical phase, and on graduation) were invited to complete the survey. Data were collected between May 2021 and April 2023. Results The questionnaire was sent to 1406 students, of whom 683 replied (49%); 481 respondents were female (70%). The top specialty choices across the respondents were internal medicine, surgery, and general practice, with anaesthesiology, paediatric and adolescent medicine (ranging 11–15%), and obstetrics and gynaecology also receiving interest, with 6% undecided. In particular, female students lost interest in surgery during the course of study in favour of the other options. The choice of general practice was associated with more vocational training, prior positive experiences with the specialty, and lower grades in the university entry examination. Clinical clerkships in a specific (freely chosen) specialty aligned with career choice, while the final practical year did not have an impact on career decision-making. All students highly desired regulated working hours and work-life-balance; however, students choosing surgery rated these items as less important. Willingness to work in a hospital environment was highly associated with choosing anaesthesiology and surgery, whereas rural areas and practices were associated with general practice. Higher scores at agreeableness were associated with choosing paediatric and adolescent medicine by more female students, whereas lower neuroticism values were associated with the choice of anaesthesiology. Conclusions The results highlight the intricate nature of decision-making and shed light on various aspects that contribute to the process of selecting a specialty. By identifying and addressing influencing factors, we can develop targeted interventions and policies to enhance diversity and distribution across medical specialisations and to aim for high-quality and equitable healthcare that matches the specific needs of both individuals and the population as a whole. Graphical Abstrac

Multiparameter mapping of relaxation (R1, R2*), proton density and magnetization transfer saturation at 3 T: A multicenter dual-vendor reproducibility and repeatability study

Multicenter clinical and quantitative magnetic resonance imaging (qMRI) studies require a high degree of reproducibility across different sites and scanner manufacturers, as well as time points. We therefore implemented a multiparameter mapping (MPM) protocol based on vendor's product sequences and demonstrate its repeatability and reproducibility for whole-brain coverage. Within ~20 min, four MPM metrics (magnetization transfer saturation [MT], proton density [PD], longitudinal [R1], and effective transverse [R2*] relaxation rates) were measured using an optimized 1 mm isotropic resolution protocol on six 3 T MRI scanners from two different vendors. The same five healthy participants underwent two scanning sessions, on the same scanner, at each site. MPM metrics were calculated using the hMRI-toolbox. To account for different MT pulses used by each vendor, we linearly scaled the MT values to harmonize them across vendors. To determine longitudinal repeatability and inter-site comparability, the intra-site (i.e., scan-rescan experiment) coefficient of variation (CoV), inter-site CoV, and bias across sites were estimated. For MT, R1, and PD, the intra- and inter-site CoV was between 4 and 10% across sites and scan time points for intracranial gray and white matter. A higher intra-site CoV (16%) was observed in R2* maps. The inter-site bias was below 5% for all parameters. In conclusion, the MPM protocol yielded reliable quantitative maps at high resolution with a short acquisition time. The high reproducibility of MPM metrics across sites and scan time points combined with its tissue microstructure sensitivity facilitates longitudinal multicenter imaging studies targeting microstructural changes, for example, as a quantitative MRI biomarker for interventional clinical trials

Item format statistics and readability of extended matching questions as an effective tool to assess medical students

Testing based on multiple choice questions (MCQ) is one of the most established forms of assessment, not only in the medical field. Extended matching questions (EMQ) represent a specific type of MCQ designed to require higher levels of cognition, such as problem-solving. The purpose of this evaluation was to assess the suitability and efficiency of EMQ as an assessment method. EMQ were incorporated into the end-of-semester examination in internal medicine, in which 154 students participated, and compared with three established MCQ types. Item and examination quality were investigated, as well as readability and processing time. EMQ were slightly more difficult to score; however, both item discrimination and discrimination index were higher when compared to other item types. EMQ were found to be significantly longer and required more processing time, but readability was improved. Students judged EMQ as clearly challenging, but attributed significantly higher clinical relevance when compared to established MCQ formats. Using the Spearman-Brown prediction, only ten EMQ items would be needed to reproduce the Cronbach’s alpha value of 0.75 attained for the overall examination. EMQ proved to be both efficient and suitable when assessing medical students, demonstrating powerful characteristics of reliability. Their expanded use in favor of common MCQ could save examination time without losing out on statistical quality

Reliability of spinal cord measures based on synthetic T1-weighted MRI derived from multiparametric mapping (MPM)

Short MRI acquisition time, high signal-to-noise ratio, and high reliability are crucial for image quality when scanning healthy volunteers and patients. Cross-sectional cervical cord area (CSA) has been suggested as a marker of neurodegeneration and potential outcome measure in clinical trials and is conventionally measured on T1-weigthed 3D Magnetization Prepared Rapid Acquisition Gradient-Echo (MPRAGE) images. This study aims to reduce the acquisition time for the comprehensive assessment of the spinal cord, which is typically based on MPRAGE for morphometry and multi-parameter mapping (MPM) for microstructure. The MPRAGE is replaced by a synthetic T1-w MRI (synT1-w) estimated from the MPM, in order to measure CSA. SynT1-w images were reconstructed using the MPRAGE signal equation based on quantitative maps of proton density (PD), longitudinal (R1) and effective transverse (R2*) relaxation rates. The reliability of CSA measurements from synT1-w images was determined within a multi-center test-retest study format and validated against acquired MPRAGE scans by assessing the agreement between both methods. The response to pathological changes was tested by longitudinally measuring spinal cord atrophy following spinal cord injury (SCI) for synT1-w and MPRAGE using linear mixed effect models. CSA measurements based on the synT1-w MRI showed high intra-site (Coefficient of variation [CoV]: 1.43% to 2.71%) and inter-site repeatability (CoV: 2.90% to 5.76%), and only a minor deviation of -1.65 mm2 compared to MPRAGE. Crucially, by assessing atrophy rates and by comparing SCI patients with healthy controls longitudinally, differences between synT1-w and MPRAGE were negligible. These results demonstrate that reliable estimates of CSA can be obtained from synT1-w images, thereby reducing scan time significantly