The effect of prolonged spaceflight on cerebrospinal fluid and perivascular spaces of astronauts and cosmonauts.

Long-duration spaceflight induces changes to the brain and cerebrospinal fluid compartments and visual acuity problems known as spaceflight-associated neuro-ocular syndrome (SANS). The clinical relevance of these changes and whether they equally affect crews of different space agencies remain unknown. We used MRI to analyze the alterations occurring in the perivascular spaces (PVS) in NASA and European Space Agency astronauts and Roscosmos cosmonauts after a 6-mo spaceflight on the International Space Station (ISS). We found increased volume of basal ganglia PVS and white matter PVS (WM-PVS) after spaceflight, which was more prominent in the NASA crew than the Roscosmos crew. Moreover, both crews demonstrated a similar degree of lateral ventricle enlargement and decreased subarachnoid space at the vertex, which was correlated with WM-PVS enlargement. As all crews experienced the same environment aboard the ISS, the differences in WM-PVS enlargement may have been due to, among other factors, differences in the use of countermeasures and high-resistive exercise regimes, which can influence brain fluid redistribution. Moreover, NASA astronauts who developed SANS had greater pre- and postflight WM-PVS volumes than those unaffected. These results provide evidence for a potential link between WM-PVS fluid and SANS.

Standardized reporting for Head CT Scans in patients suspected of traumatic brain injury (TBI): An international expert endeavor.

BACKGROUND AND PURPOSE: Traumatic brain injury (TBI) is a major source of health loss and disability worldwide. Accurate and timely diagnosis of TBI is critical for appropriate treatment and management of the condition. Neuroimaging plays a crucial role in the diagnosis and characterization of TBI. Computed tomography (CT) is the first-line diagnostic imaging modality typically utilized in patients with suspected acute mild, moderate and severe TBI. Radiology reports play a crucial role in the diagnostic process, providing critical information about the location and extent of brain injury, as well as factors that could prevent secondary injury. However, the complexity and variability of radiology reports can make it challenging for healthcare providers to extract the necessary information for diagnosis and treatment planning. METHODS/RESULTS/CONCLUSION: In this article, we report the efforts of an international group of TBI imaging experts to develop a clinical radiology report template for CT scans obtained in patients suspected of TBI and consisting of fourteen different subdivisions (CT technique, mechanism of injury or clinical history, presence of scalp injuries, fractures, potential vascular injuries, potential injuries involving the extra-axial spaces, brain parenchymal injuries, potential injuries involving the cerebrospinal fluid spaces and the ventricular system, mass effect, secondary injuries, prior or coexisting pathology).

Brain ventricular volume changes induced by long-duration spaceflight.

Long-duration spaceflight induces detrimental changes in human physiology. Its residual effects and mechanisms remain unclear. We prospectively investigated the changes in cerebrospinal fluid (CSF) volume of the brain ventricular regions in space crew by means of a region of interest analysis on structural brain scans. Cosmonaut MRI data were investigated preflight (n = 11), postflight (n = 11), and at long-term follow-up 7 mo after landing (n = 7). Post hoc analyses revealed a significant difference between preflight and postflight values for all supratentorial ventricular structures, i.e., lateral ventricle (mean % change ± SE = 13.3 ± 1.9), third ventricle (mean % change ± SE = 10.4 ± 1.1), and the total ventricular volume (mean % change ± SE = 11.6 ± 1.5) (all P < 0.0001), with higher volumes at postflight. At follow-up, these structures did not quite reach baseline levels, with still residual increases in volume for the lateral ventricle (mean % change ± SE = 7.7 ± 1.6; P = 0.0009), the third ventricle (mean % change ± SE = 4.7 ± 1.3; P = 0.0063), and the total ventricular volume (mean % change ± SE = 6.4 ± 1.3; P = 0.0008). This spatiotemporal pattern of CSF compartment enlargement and recovery points to a reduced CSF resorption in microgravity as the underlying cause. Our results warrant more detailed and longer longitudinal follow-up. The clinical impact of our findings on the long-term cosmonauts' health and their relation to ocular changes reported in space travelers requires further prospective studies.

Effect of Exposure to Gadodiamide and Brain Irradiation on T1 -Weighted Images and ADC Maps of the Dentate Nucleus.

BACKGROUND: Brain irradiation is considered a cofactor influencing the dentate nucleus (DN) signal intensity (SI) on unenhanced T1 -weighted images in patients exposed to gadolinium-based contrast agents (GBCAs). PURPOSE: To assess the effect of gadodiamide and whole-brain radiation therapy (WBRT) on T1 -weighted images and on apparent diffusion coefficient (ADC) maps of DN. STUDY TYPE: Single-center retrospective. POPULATION: In all, 125 patients who underwent brain MRIs were classified into four groups: 1) patients who did neither receive intravenous GBCAs injections nor irradiation (controls); 2) patients having ≥3 GBCAs-enhanced scans and no WBRT; 3) patients having WBRT and < 3 GBCAs-enhanced scans; and 4) patients having WBRT and ≥ 3 GBCAs-enhanced scans. FIELD STRENGTH/SEQUENCE: 1.5T magnet, echo-planar diffusion weighted imaging (DWI) and unenhanced T1 -weighted sequences. ASSESSMENT: The DN-to-pons SI ratio on unenhanced T1 -weighted images and ADC values of the DN were calculated. Values were compared between groups and relative to the cumulative gadolinium dose and to the time delay after WBRT. STATISTICAL TESTS: Statistical analysis included the Mann-Whitney U-test and Spearman's rank-order correlation. RESULTS: DN ADC values were not significantly different (P = 0.34) between patients exposed to gadodiamide (0.81 ± 0.06) and controls (0.83 ± 0.07). There were no differences in DN ADC values (P = 0.28) and DN-to-pons SI ratios (P = 0.42) between patients exposed to WBRT (ADC values: 0.85 ± 0.09; SI ratio: 1.11 ± 0.10) and controls (ADC values: 0.83 ± 0.06; SI ratio: 1.09 ± 0.06). There was a significant negative correlation between DN ADC values and the time (days) since the end of WBRT (r = - 0.33; 95% confidence interval [CI]: -0.55, -0.06; P < 0.05). DATA CONCLUSION: We did not find changes suggestive of gadolinium-related tissue microstructural damage of the DN. The ADC values of the DN are associated with the time from WBRT. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 5.

Exposure to gadolinium and neurotoxicity: current status of preclinical and clinical studies.

PURPOSE: Gadolinium is a rare-earth lanthanide metal that is known to have a direct neurotoxic effect. The scope of the present review is to summarize the current preclinical and clinical evidence on the association between exposure to gadolinium of the central nervous system and neurotoxicity. METHODS: A literature review was performed by searching for original research papers investigating on gadolinium exposure and neurotoxicity. RESULTS: Gadolinium is neurotoxic through multiple mechanisms, mainly involving Ca++ homeostasis and mitochondrial functions, as shown by preclinical in vitro studies. The available evidence related to the four different classes of gadolinium-based contrast agents commonly applied in clinical practice (i.e., linear and macrocyclic based on ligand structure, and ionic and non-ionic based on their net molecular charge) suggests that serial intravenous injections of gadolinium-based contrast agents and gadolinium brain depositions are not associated to histological changes, as confirmed by preclinical animal and human (MR imaging and autopsy) studies. CONCLUSION: To date, no cause-effect relationship has been demonstrated in patients between brain gadolinium exposure and clinical consequences specific to neurological toxicity.

Within-network brain connectivity in Crohn's disease patients with gadolinium deposition in the cerebellum.

PURPOSE: Patients with Crohn's disease (CD) undergo multiple gadolinium-based contrast agent injections across their lifespan to enhance signal intensity of the intestinal wall and differentiate active from quiescent inflammatory disease. Thus, CD patients are prone to gadolinium accumulation in the brain and represent a non-neurological population to explore gadolinium-related brain toxicity. Possible effects are expected to be greater on the cerebellar network due to the high propensity of the dentate nucleus to accumulate gadolinium. Herein, we provide a whole-brain network analysis of resting-state fMRI dynamics in long-term quiescent CD patients with normal renal function and MRI evidence of gadolinium deposition in the brain. METHODS: Fifteen patients with CD and 16 healthy age- and gender-matched controls were enrolled in this study. Relevant resting-state networks (RSNs) were identified using independent component analysis (ICA) from functional magnetic resonance imaging data. An unpaired two-sample t test (with age and sex as nuisance variables) was used to investigate between different RSNs. Clusters were determined by using threshold-free cluster enhancement and a family-wise error corrected cluster significance threshold of p < 0.05. RESULTS: Patients showed significantly decreased resting-state functional connectivity (p < 0.05, FWE corrected) of several regions of the right frontoparietal (FPR) and the dorsal attention (DAN) RSNs. No differences between the two groups were found in the functional connectivity maps of all the other RSNs, including the cerebellar network. CONCLUSION: Our findings suggest a non-significant impact of gadolinium deposition on within-network cerebellar functional connectivity of long-term quiescent CD patients.

Age-related changes to the craniocervical ligaments in asymptomatic subjects: a prospective MR study.

PURPOSE: The craniocervical junction (CCJ) is a complex of bony and ligamentous structure stabilizing CCJ. Nearly one-third of all traumatic injuries to the cervical spine involve the CCJ. Only little literature is available on this topic, and most of the studies are focused on anatomy, biomechanics or ligamentous injury in whiplash-associated disorders. We conducted a prospective study to investigate age-related changes in the craniocervical ligaments. METHODS: We included asymptomatic volunteers between 16 and 99 years old who had no history of whiplash or other cervical trauma. Volunteers underwent a three-dimensional turbo spin-echo proton density-weighted sequence with variable flip-angle distribution focused on the craniocervical ligaments. The six main ligaments of the craniocervical junction were evaluated for grade of degeneration on a four-point scale by two independent readers, blinded for age and sex. RESULTS: We included 102 volunteers. The mean age was 50.03 (16-94). Fifty-nine (58%) patients showed degeneration of at least one ligament of the CCJ. High-grade anomalous changes and multiligamentous involvement had a positive correlation with age (p < 0.001). The inter-rater agreement was fair to moderate, and the intra-rater agreement was moderate to substantial. CONCLUSION: The craniocervical ligaments show a variable degree of signal intensity and thickness in asymptomatic adults. We postulate that these changes can be due to normal aging or due to repetitive microtrauma. We propose a new grading system to evaluate changes to the craniocervical ligaments in asymptomatic volunteers. These slides can be retrieved under Electronic Supplementary Material.

Potential of a statistical approach for the standardization of multicenter diffusion tensor data: A phantom study.

BACKGROUND: Diffusion tensor imaging (DTI) parameters, such as fractional anisotropy (FA), allow examining the structural integrity of the brain. However, the true value of these parameters may be confounded by variability in MR hardware, acquisition parameters, and image quality. PURPOSE: To examine the effects of confounding factors on FA and to evaluate the feasibility of statistical methods to model and reduce multicenter variability. STUDY TYPE: Longitudinal multicenter study. PHANTOM: DTI single strand phantom (HQ imaging). FIELD STRENGTH/SEQUENCE: 3T diffusion tensor imaging. ASSESSMENTS: Thirteen European imaging centers participated. DTI scans were acquired every 6 months and whenever maintenance or upgrades to the system were performed. A total of 64 scans were acquired in 2 years, obtained by three scanner vendors, using six individual head coils, and 12 software versions. STATISTICAL TESTS: The variability in FA was assessed by the coefficients of variation (CoV). Several linear mixed effects models (LMEM) were developed and compared by means of the Akaike Information Criterion (AIC). RESULTS: The CoV was 2.22% for mean FA and 18.40% for standard deviation of FA. The variables "site" (P = 9.26 × 10-5 ), "vendor" (P = 2.18 × 10-5 ), "head coil" (P = 9.00 × 10-4 ), "scanner drift," "bandwidth" (P = 0.033), "TE" (P = 8.20 × 10-6 ), "SNR" (P = 0.029) and "mean residuals" (P = 6.50 × 10-4 ) had a significant effect on the variability in mean FA. The variables "site" (P = 4.00 × 10-4 ), "head coil" (P = 2.00 × 10-4 ), "software" (P = 0.014), and "mean voxel outlier intensity count" (P = 1.10 × 10-4 ) had a significant effect on the variability in standard deviation of FA. The mean FA was best predicted by an LMEM that included "vendor" and the interaction term of "SNR" and "head coil" as model factors (AIC -347.98). In contrast, the standard deviation of FA was best predicted by an LMEM that included "vendor," "bandwidth," "TE," and the interaction term between "SNR" and "head coil" (AIC -399.81). DATA CONCLUSION: Our findings suggest that perhaps statistical models seem promising to model the variability in quantitative DTI biomarkers for clinical routine and multicenter studies. LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:955-965.

Absence of dentate nucleus resting-state functional connectivity changes in nonneurological patients with gadolinium-related hyperintensity on T1 -weighted images.

BACKGROUND: The dentate nuclei of the cerebellum are the areas where gadolinium predominantly accumulates. It is not yet known whether gadolinium deposition affects brain functions. PURPOSE/HYPOTHESIS: To assess whether gadolinium-dependent high signal intensity of the cerebellum on T1 -weighted images of nonneurological adult patients with Crohn's disease is associated with modifications of resting-state functional connectivity (RSFC) of the cerebellum and dentate nucleus. STUDY TYPE: Observational, cross-sectional. POPULATION: Fifteen patients affected by Crohn's disease were compared with 16 healthy age- and gender-matched control subjects. All participants underwent neurological, neurocognitive-psychological assessment, and blood sampling. FIELD STRENGTH/SEQUENCE: 1.5-T magnet blood oxygenation level-dependent (BOLD) functional MRI. ASSESSMENT: High signal intensity on T1 -weighted images, cerebellum functional connectivity, neurocognitive performance, and blood circulating gadolinium levels. STATISTICAL TESTS: An unpaired two-sample t-test (age and sex were nuisance variables) was used to investigate between-group differences in cerebellar and dentate nucleus functional connectivity. Z-statistical images were set using clusters determined by Z > 2.3 and a familywise error (FWE)-corrected cluster significance threshold of P = 0.05. RESULTS: Dentate nuclei RSFC was not different (P = n.s.) between patients with gadolinium-dependent high signal intensity on T1 -weighted images and controls. Pre- and postcentral gyrus bilaterally and the right supplementary motor cortex showed a decrease of RSFC with the cerebellum hemispheres (P < 0.05 FWE-corrected) and was related to disease duration but not to gadodiamide cumulative doses (P = n.s.). DATA CONCLUSION: Crohn's disease patients with gadolinium-dependent hyperintense dentate nuclei on unenhanced T1 -weighted images do not show dentate nucleus RSFC changes. LEVEL OF EVIDENCE: 2 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:445-455.

Assessment of Anterolateral Complex Injuries by Magnetic Resonance Imaging in Patients With Acute Rupture of the Anterior Cruciate Ligament.

PURPOSE: To assess anterolateral complex (ALC) injuries in patients with acute anterior cruciate ligament (ACL) rupture on magnetic resonance imaging (MRI). METHODS: Patients with acute ACL rupture who underwent ACL surgery between 2015 and 2017 and underwent MRI within 6 weeks of the initial trauma were included. Two radiologists assessed magnetic resonance images retrospectively for the status of the ALC, including the iliotibial band (ITB), Kaplan fibers, and anterolateral ligament (ALL), as follows: grade 0, normal; grade 1, periligamentous edema; grade 2, partial tear; and grade 3, complete tear. The findings were analyzed using the Friedman test and weighted κ values. RESULTS: Sixty-nine MRI scans were reviewed. Of the 69 patients, 51% had associated injuries to the ITB (grade 1, n = 31; grade 2, n = 4), 33% had associated injuries to the Kaplan fibers (grade 1, n = 21; grade 2, n = 2), and 57% had associated injuries to the ALL (grade 1, n = 12; grade 2, n = 22; grade 3, n = 5). We found a significant difference in the frequency and grading between ITB, Kaplan fiber, and ALL injuries (P ≤ .032). Inter-reader agreement for assessing the ALC on MRI was almost perfect (κ ≥ 0.922). CONCLUSIONS: On the basis of MRI analysis, ALL injuries were found with varying degrees of severity and intensity with noted injuries to associated surrounding fibers in patients with acute ACL rupture. LEVEL OF EVIDENCE: Level IV, case series.

Diffusion kurtosis imaging with free water elimination: A bayesian estimation approach.

PURPOSE: Diffusion kurtosis imaging (DKI) is an advanced magnetic resonance imaging modality that is known to be sensitive to changes in the underlying microstructure of the brain. Image voxels in diffusion weighted images, however, are typically relatively large making them susceptible to partial volume effects, especially when part of the voxel contains cerebrospinal fluid. In this work, we introduce the "Diffusion Kurtosis Imaging with Free Water Elimination" (DKI-FWE) model that separates the signal contributions of free water and tissue, where the latter is modeled using DKI. THEORY AND METHODS: A theoretical study of the DKI-FWE model, including an optimal experiment design and an evaluation of the relative goodness of fit, is carried out. To stabilize the ill-conditioned estimation process, a Bayesian approach with a shrinkage prior (BSP) is proposed. In subsequent steps, the DKI-FWE model and the BSP estimation approach are evaluated in terms of estimation error, both in simulation and real data experiments. RESULTS: Although it is shown that the DKI-FWE model parameter estimation problem is ill-conditioned, DKI-FWE was found to describe the data significantly better compared to the standard DKI model for a large range of free water fractions. The acquisition protocol was optimized in terms of the maximally attainable precision of the DKI-FWE model parameters. The BSP estimator is shown to provide reliable DKI-FWE model parameter estimates. CONCLUSION: The combination of the DKI-FWE model with BSP is shown to be a feasible approach to estimate DKI parameters, while simultaneously eliminating free water partial volume effects. Magn Reson Med 80:802-813, 2018. © 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Advanced CT acquisition protocol with a third-generation dual-source CT scanner and iterative reconstruction technique for comprehensive prosthetic heart valve assessment.

OBJECTIVES: Multidetector CT (MDCT) is a valuable tool for functional prosthetic heart valve (PHV) assessment. However, radiation exposure remains a concern. We assessed a novel CT-acquisition protocol for comprehensive PHV evaluation at limited dose. METHODS: Patients with a PHV were scanned using a third-generation dual-source CT scanner (DSCT) and iterative reconstruction technique (IR). Three acquisitions were obtained: a non-enhanced scan; a contrast-enhanced, ECG-triggered, arterial CT angiography (CTA) scan with reconstructions at each 5 % of the R-R interval; and a delayed high-pitch CTA of the entire chest. Image quality was scored on a five-point scale. Radiation dose was obtained from the reported CT dose index (CTDI) and dose length product (DLP). RESULTS: We analysed 43 CT examinations. Mean image quality score was 4.1±1.4, 4.7±0.5 and 4.2±0.6 for the non-contrast-enhanced, arterial and delayed acquisitions, respectively, with a total mean image quality of 4.3±0.7. Mean image quality for leaflet motion was 3.9±1.4. Mean DLP was 28.2±17.1, 457.3±168.6 and 68.5±47.2 mGy.cm for the non-contrast-enhanced (n=40), arterial (n=43) and delayed acquisition (n=43), respectively. The mean total DLP was 569±208 mGy.cm and mean total radiation dose was 8.3±3.0 mSv (n=43). CONCLUSION: Comprehensive assessment of PHVs is possible using DSCT and IR at moderate radiation dose. KEY POINTS: • Prosthetic heart valve dysfunction is a potentially life-threatening condition. • Dual-source CT can adequately assess valve leaflet motion and anatomy. • We assessed a comprehensive protocol with three acquisitions for PHV evaluation. • This protocol is associated with good image quality and limited dose.

Super-resolution T1 estimation: Quantitative high resolution T1 mapping from a set of low resolution T1 -weighted images with different slice orientations.

PURPOSE: Quantitative T1 mapping is a magnetic resonance imaging technique that estimates the spin-lattice relaxation time of tissues. Even though T1 mapping has a broad range of potential applications, it is not routinely used in clinical practice as accurate and precise high resolution T1 mapping requires infeasibly long acquisition times. METHOD: To improve the trade-off between the acquisition time, signal-to-noise ratio and spatial resolution, we acquire a set of low resolution T1 -weighted images and directly estimate a high resolution T1 map by means of super-resolution reconstruction. RESULTS: Simulation and in vivo experiments show an increased spatial resolution of the T1 map, while preserving a high signal-to-noise ratio and short scan time. Moreover, the proposed method outperforms conventional estimation in terms of root-mean-square error. CONCLUSION: Super resolution T1 estimation enables resolution enhancement in T1 mapping with the use of standard (inversion recovery) T1 acquisition sequences. Magn Reson Med 77:1818-1830, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Diffusion tensor imaging of the anterior cruciate ligament graft.

PURPOSE: A great need exists for objective biomarkers to assess graft healing following ACL reconstruction to guide the time of return to sports. The purpose of this study was to evaluate the feasibility and reliability of diffusion tensor imaging (DTI) to delineate the anterior cruciate ligament (ACL) graft and to investigate its diffusion properties using a clinical 3T scanner. MATERIALS AND METHODS: DTI of the knee (b = 0, 400, and 800 s/mm2 , 10 diffusion directions, repeated 16 times for a total of 336 diffusion-weighted volumes) was performed at 3T in 17 patients between 3 and 7 months (mean, 4 months) following ACL reconstruction. Tractography was performed by two independent observers to delineate the ACL graft. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated within the graft. Interrater reliability was assessed using the intraclass correlation coefficient (ICC) and the scan-rescan reproducibility was evaluated based on the percentage coefficient of variance (%CV) across 20 repetition bootknife samples. RESULTS: In all subjects, tractography of the ACL graft was feasible. Quantitative evaluation of the diffusion properties of the ACL graft yielded the following mean ± SD values: FA = 0.23 ± 0.04; MD = 1.30 ± 0.11 × 10-3 mm2 /s; AD = 1.61 ± 0.12 × 10-3 mm2 /s, and RD = 1.15 ± 0.11 × 10-3 mm2 /s. Interrater reliability for the DTI parameters was excellent (ICC = 0.91-0.98). Mean %CVs for FA, MD, AD, and RD were 4.6%, 3.5%, 3.7%, and 4.4%, respectively. CONCLUSION: We demonstrated the feasibility and reliability of DTI for the visualization and quantitative evaluation of the ACL graft at 3T. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1423-1432.

A functional MRI study on how oxytocin affects decision making in social dilemmas: Cooperate as long as it pays off, aggress only when you think you can win.

We investigate if the neuropeptide oxytocin (OT), known to moderate social behaviour, influences strategic decision making in social dilemmas by facilitating the integration of incentives and social cues. Participants (N=29) played two economic games with different incentive structures in the fMRI scanner after receiving OT or placebo (following a double blind, within-subject design). Pictures of angry or neutral faces (the social cues) were displayed alongside the game matrices. Consistent with a priori hypotheses based on the modulatory role of OT in mesolimbic dopaminergic brain regions, the results indicate that, compared to placebo, OT significantly increases the activation of the nucleus accumbens during an assurance (coordination) game that rewards mutual cooperation. This increases appetitive motivation so that cooperative behaviour is facilitated for risk averse individuals. OT also significantly attenuates the amygdala, thereby reducing the orienting response to social cues. The corresponding change in behaviour is only apparent in the chicken (or anti-coordination) game, where aggression is incentivized but fatal if the partner also aggresses. Because of this ambiguity, decision making can be improved by additional information, and OT steers decisions in the chicken game in accordance with the valence of the facial cue: aggress when face is neutral; retreat when it is angry. Through its combined influence on amygdala and nucleus accumbens, OT improves the selection of a cooperative or aggressive strategy in function of the best match between the incentives of the game and the social cues present in the decision environment.

Benchmarking pediatric cranial CT protocols using a dose tracking software system: a multicenter study.

OBJECTIVES: To benchmark regional standard practice for paediatric cranial CT-procedures in terms of radiation dose and acquisition parameters. METHODS: Paediatric cranial CT-data were retrospectively collected during a 1-year period, in 3 different hospitals of the same country. A dose tracking system was used to automatically gather information. Dose (CTDI and DLP), scan length, amount of retakes and demographic data were stratified by age and clinical indication; appropriate use of child-specific protocols was assessed. RESULTS: In total, 296 paediatric cranial CT-procedures were collected. Although the median dose of each hospital was below national and international diagnostic reference level (DRL) for all age categories, statistically significant (p-value < 0.001) dose differences among hospitals were observed. The hospital with lowest dose levels showed smallest dose variability and used age-stratified protocols for standardizing paediatric head exams. Erroneous selection of adult protocols for children still occurred, mostly in the oldest age-group. CONCLUSION: Even though all hospitals complied with national and international DRLs, dose tracking and benchmarking showed that further dose optimization and standardization is possible by using age-stratified protocols for paediatric cranial CT. Moreover, having a dose tracking system revealed that adult protocols are still applied for paediatric CT, a practice that must be avoided. KEY POINTS: • Significant differences were observed in the delivered dose between age-groups and hospitals. • Using age-adapted scanning protocols gives a nearly linear dose increase. • Sharing dose-data can be a trigger for hospitals to reduce dose levels.

Super-resolution reconstruction of diffusion parameters from diffusion-weighted images with different slice orientations.

PURPOSE: Diffusion MRI is hampered by long acquisition times, low spatial resolution, and a low signal-to-noise ratio. Recently, methods have been proposed to improve the trade-off between spatial resolution, signal-to-noise ratio, and acquisition time of diffusion-weighted images via super-resolution reconstruction (SRR) techniques. However, during the reconstruction, these SRR methods neglect the q-space relation between the different diffusion-weighted images. METHOD: An SRR method that includes a diffusion model and directly reconstructs high resolution diffusion parameters from a set of low resolution diffusion-weighted images was proposed. Our method allows an arbitrary combination of diffusion gradient directions and slice orientations for the low resolution diffusion-weighted images, optimally samples the q- and k-space, and performs motion correction with b-matrix rotation. RESULTS: Experiments with synthetic data and in vivo human brain data show an increase of spatial resolution of the diffusion parameters, while preserving a high signal-to-noise ratio and low scan time. Moreover, the proposed SRR method outperforms the previous methods in terms of the root-mean-square error. CONCLUSION: The proposed SRR method substantially increases the spatial resolution of MRI that can be obtained in a clinically feasible scan time.

Anterolateral ligament abnormalities in patients with acute anterior cruciate ligament rupture are associated with lateral meniscal and osseous injuries.

OBJECTIVE: To determine the frequency of anterolateral ligament (ALL) injury in patients with acute anterior cruciate ligament (ACL) rupture and to analyse its associated injury patterns. METHODS: Ninety patients with acute ACL rupture for which MRI was obtained within 8 weeks after the initial trauma were retrospectively identified. Two radiologists assessed the status of the ALL on MRI by consensus. The presence or absence of an ALL abnormality was compared with the existence of medial and lateral meniscal tears diagnosed during arthroscopy. Associated collateral ligament and osseous injuries were documented with MRI. RESULTS: Forty-one of 90 knees (46 %) demonstrated ALL abnormalities on MRI. Of 49 knees with intact ALL, 15 (31 %) had a torn lateral meniscus as compared to 25 torn lateral menisci in 41 knees (61 %) with abnormal ALL (p = 0.008). Collateral ligament (p ≤ 0.05) and osseous injuries (p = 0.0037) were more frequent and severe in ALL-injured as compared with ALL-intact knees. CONCLUSION: ALL injuries are fairly common in patients with acute ACL rupture and are statistically significantly associated with lateral meniscal, collateral ligament and osseous injuries. KEY POINTS: • ALL injuries are fairly common in patients with acute ACL rupture. • ALL injuries are highly associated with lateral meniscal and osseous injuries. • MRI assessment of ACL-injured knees should include evaluation of the ALL.