Body size interacts with the structure of the central nervous system: A multi-center in vivo neuroimaging study

Clinical research emphasizes the implementation of rigorous and reproducible study designs that rely on between-group matching or controlling for sources of biological variation such as subject's sex and age. However, corrections for body size (i.e. height and weight) are mostly lacking in clinical neuroimaging designs. This study investigates the importance of body size parameters in their relationship with spinal cord (SC) and brain magnetic resonance imaging (MRI) metrics. Data were derived from a cosmopolitan population of 267 healthy human adults (age 30.1±6.6 years old, 125 females). We show that body height correlated strongly or moderately with brain gray matter (GM) volume, cortical GM volume, total cerebellar volume, brainstem volume, and cross-sectional area (CSA) of cervical SC white matter (CSA-WM; 0.44≤r≤0.62). In comparison, age correlated weakly with cortical GM volume, precentral GM volume, and cortical thickness (-0.21≥r≥-0.27). Body weight correlated weakly with magnetization transfer ratio in the SC WM, dorsal columns, and lateral corticospinal tracts (-0.20≥r≥-0.23). Body weight further correlated weakly with the mean diffusivity derived from diffusion tensor imaging (DTI) in SC WM (r=-0.20) and dorsal columns (-0.21), but only in males. CSA-WM correlated strongly or moderately with brain volumes (0.39≤r≤0.64), and weakly with precentral gyrus thickness and DTI-based fractional anisotropy in SC dorsal columns and SC lateral corticospinal tracts (-0.22≥r≥-0.25). Linear mixture of sex and age explained 26±10% of data variance in brain volumetry and SC CSA. The amount of explained variance increased at 33±11% when body height was added into the mixture model. Age itself explained only 2±2% of such variance. In conclusion, body size is a significant biological variable. Along with sex and age, body size should therefore be included as a mandatory variable in the design of clinical neuroimaging studies examining SC and brain structure.

[The elective planetary health: Climate, environment and health at the faculty of medicine in Würzburg: Concept, didactic methods and evaluation results]

BACKGROUND

The connections between climate, environment, and health as well as the concept of planetary health need to be integrated into the education of health professionals, as is increasingly demanded both internationally and nationally. Planetary health education should also aim to foster transformative action for climate protection and sustainability. In recent years, innovative teaching formats and objective catalogues have emerged internationally. In Germany, these topics have not yet been integrated into medical education everywhere. Since 2021, the Faculty of Medicine in Würzburg has offered an elective course as a first step of a longitudinal curriculum currently in development. The design, content, structure, and results of the evaluation are discussed in this article and will be used for quality assurance as well as the (further) development of this kind of educational interventions elsewhere.

METHODOLOGY

We developed an elective course for students in their second to tenth semester with 30 onsite and online face-to-face teaching units and an additional project phase. We used an innovative mix of didactic methods with online simulations, training in climate-sensitive health counselling, and interdisciplinary climate communication as well as local sustainability projects in small groups, with a large amount of peer-teaching. A quantitative and qualitative evaluation was done immediately after the teaching units through feedback rounds and online with the evaluation software Evasys®, using closed and open-ended questions exploring learning progress (summer semester) and achievement of learning objectives (winter semester), motivation to participate, acceptance of teaching methods, attitudes, relevance, and further interest. The evaluation questionnaire was slightly modified for the winter semester.

RESULTS

In the summer and winter semester of 2021/2022, a total of 34 students (17 per semester) participated in the elective course; of these, 33 participated in the written evaluation. The evaluation in the summer semester (n = 17) showed a significant increase in self-assessed learning gain, the evaluation in the winter semester (n = 16) indicated a substantial achievement of learning objectives (mean = 3.96 of a 5-point Likert scale). Participants of both semesters (n = 33) regarded peer-teaching as a suitable method (mean = 4.2) and well-implemented (mean = 4.3). The topics were considered highly relevant but not adequately integrated into the main curriculum. There was a high level of interest in local impacts of climate and environmental changes and local measures for climate protection and sustainability. The specific projects in small groups may serve as examples of how transformative action can be promoted in education.

DISCUSSION

In the current dynamic development of the widely demanded integration of planetary health education into curricula, this elective course shows a possible and well-accepted example with a combination of various innovative didactic methods aiming at the levels of knowledge, attitudes, skills, and self-efficacy (or confidence) alike. The positive evaluation by the students and the high interest in local sustainability projects show the potential for future integration into the main curriculum.

CONCLUSION

The elective can serve as an inspiration to tackle the challenge of taking the steps from knowledge to action in planetary health education. While an elective cannot replace the integration of all relevant aspects of planetary health into the main curriculum, it can serve as a space for piloting of future curricular educational interventions and offer opportunities for developing transformative competencies.

Pre-post evaluation of the emotions and motivations for transformative action of medical students in Germany after two different planetary health educational interventions

BACKGROUND

Climate change is the greatest threat to human health. Medical students, as future health-care workers, are important in promoting sustainable behaviours, which are strongly associated with individuals' emotional responses to climate change. At Würzburg University Hospital (Würzburg, Germany), a one-term optional course (40 learning units) about planetary health and two lectures within the curricular course Environmental Medicine were introduced in 2021. We aimed to examine the effects of these courses on the emotions and motivations of students in acting against climate change.

METHODS

We surveyed medical students from both courses during four consecutive terms during 2021-23 with a pre-post design using an anonymous online questionnaire on EvaSys. The survey consisted of 20 closed questions based on a 5-point Likert scale and six open questions. Quantitative data were analysed with SPSS version 28.0.1.1. Qualitative data were analysed with Kuckartz' qualitative content analysis.

FINDINGS

458 students were initially involved (349 [76%] in the lectures and 109 [24%] in the optional course) and 396 students were involved until the final date (288 [73%] in the lectures and 108 [27%] in the optional course). Mean response rate was 389 (85%) of 458 students pre-survey and 315 (80%) of 396 post-survey. The most frequently reported initial emotions of medical students from both cohorts were "helplessness" (220 [57%] of 389), "fear" (197 [51%]), and "disappointment" (171 [44%]). Only 82 (21%) of 389 students reported having "motivation to act" and 45 (12%) reported having "confidence". When comparing 176 matched pre-lecture and post-lecture Likert scale values of reported emotions, we observed a significant decrease in "helplessness" (mean difference -0·37, 95% CI -0·2 to -0·53; p<0·0001; d=0·34) and "disappointment" (-0·35, -0·2 to -0·49; p<0·0001; d=0·36) and a significant increase in "confidence" (0·67, 0·82 to 0·51; p<0·0001; d=0·65 and "motivation to act" (0·4, 0·53 to 0·27; p<0·0001; d=0·46). Students associated these changes with options for action offered in the lecture.

INTERPRETATION

This pre-post evaluation provides evidence for a positive effect of planetary health education at the university level. Educators should focus on options for action and create space for improving emotional resilience within courses.

FUNDING

None.

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

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.

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.

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 multi-parameter mapping (MPM) in the cervical cord: A multi-center multi-vendor quantitative MRI study

MRI based multicenter studies which target neurological pathologies affecting the spinal cord and brain - including spinal cord injury (SCI) - require standardized acquisition protocols and image processing methods. We have optimized and applied a multi-parameter mapping (MPM) protocol that simultaneously covers the brain and the cervical cord within a traveling heads study across six clinical centers (Leutritz et al., 2020). The MPM protocol includes quantitative maps (magnetization transfer saturation (MT), proton density (PD), longitudinal (R1), and effective transverse (R2*) relaxation rates) sensitive to myelination, water content, iron concentration, and morphometric measures, such as cross-sectional cord area. Previously, we assessed the repeatability and reproducibility of the brain MPM data acquired in the five healthy participants who underwent two scan-rescans (Leutritz et al., 2020). This study focuses on the cervical cord MPM data derived from the same acquisitions to determine its repeatability and reproducibility in the cervical cord. MPM matrices of the cervical cord were generated and processed using the hMRI and the spinal cord toolbox. To determine reliability of the cervical MPM data, the intra-site (i.e., scan-rescan) coefficient of variation (CoV), inter-site CoV, and bias within region of interests (C1, C2 and C3 levels) were determined. The range of the mean intra- and inter-site CoV of MT, R1 and PD was between 2.5% and 12%, and between 1.1% and 4.0% for the morphometric measures. In conclusion, the cervical MPM data showed a high repeatability and reproducibility for key imaging biomarkers and hence can be employed as a standardized tool in multi-center studies, including clinical trials.

Multi-parameter quantitative mapping of R1, R2*, PD, and MTsat is reproducible when accelerated with Compressed SENSE

Multi-parameter mapping (MPM) magnetic resonance imaging (MRI) provides quantitative estimates of the longitudinal and effective transverse relaxation rates R1 and R2*, proton density (PD), and magnetization transfer saturation (MTsat). Thereby, MPM enables better comparability across sites and time than conventional weighted MRI. However, for MPM, several contrasts must be acquired, resulting in prolonged measurement durations and thus preventing MPM's application in clinical routines. State-of-the-art imaging acceleration techniques such as Compressed SENSE (CS), a combination of compressed sensing and sensitivity encoding, can be used to reduce the scan time of MPM. However, the accuracy and precision of the resulting quantitative parameter maps have not been systematically evaluated. In this study, we therefore investigated the effect of CS acceleration on the fidelity and reproducibility of MPM acquisitions. In five healthy volunteers and in a phantom, we compared MPM metrics acquired without imaging acceleration, with the standard acceleration (SENSE factor 2.5), and with Compressed SENSE with acceleration factors 4 and 6 using a 32-channel head coil. We evaluated the reproducibility and repeatability of accelerated MPM using data from three scan sessions in gray and white matter volumes-of-interest (VOIs). Accelerated MPM provided precise and accurate quantitative parameter maps. For most parameters, the results of the CS-accelerated protocols correlated more strongly with the non-accelerated protocol than the standard SENSE-accelerated protocols. Furthermore, for most VOIs and contrasts, coefficients of variation were lower when calculated from data acquired with different imaging accelerations within a single scan session than from data acquired in different scan sessions. These results suggest that MPM with Compressed SENSE acceleration factors up to at least 6 yields reproducible quantitative parameter maps that are highly comparable to those acquired without imaging acceleration. Compressed SENSE can thus be used to considerably reduce the scan duration of R1, R2*, PD, and MTsat mapping, and is highly promising for clinical applications of MPM.

Open-access quantitative MRI data of the spinal cord and reproducibility across participants, sites and manufacturers

In a companion paper by Cohen-Adad et al. we introduce the spine generic quantitative MRI protocol that provides valuable metrics for assessing spinal cord macrostructural and microstructural integrity. This protocol was used to acquire a single subject dataset across 19 centers and a multi-subject dataset across 42 centers (for a total of 260 participants), spanning the three main MRI manufacturers: GE, Philips and Siemens. Both datasets are publicly available via git-annex. Data were analysed using the Spinal Cord Toolbox to produce normative values as well as inter/intra-site and inter/intra-manufacturer statistics. Reproducibility for the spine generic protocol was high across sites and manufacturers, with an average inter-site coefficient of variation of less than 5% for all the metrics. Full documentation and results can be found at https://spine-generic.rtfd.io/ . The datasets and analysis pipeline will help pave the way towards accessible and reproducible quantitative MRI in the spinal cord.

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.

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 R1 and R2⋆, proton density PD and magnetisation transfer MT 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.