Modelling the Arctic wave-affected marginal ice zone: a comparison with ICESat-2 observations.

We evaluate marginal ice zone (MIZ) extent in a wave-ice 25 km-resolution coupled model, compared with pan-Arctic wave-affected sea-ice regions derived from ICESat-2 altimetry over the period December 2018-May 2020. By using a definition of the MIZ based on the monthly maximum of the wave height, we suggest metrics to evaluate the model taking into account the sparse coverage of ICESat-2. The model produces MIZ extents comparable to observations, especially in winter. A sensitivity study highlights the need for strong wave attenuation in thick, compact ice but weaker attenuation as sea ice forms, as the model underestimates the MIZ extent in autumn. This underestimation may be due to limited wave growth in partially covered ice, overestimated sea-ice concentration or the absence of other processes affecting floe size. We discuss our results in the context of other definitions of the MIZ based on floe size and sea-ice concentration, as well as the potential impact of wave-induced fragmentation on ice dynamics, found to be minor at the climate scales investigated here. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.

Characterization of left atrial geometry and function in patients with hypertrophic cardiomyopathy: a cardiac magnetic resonance imaging study.

OBJECTIVE: Left atrial (LA) remodelling is an interesting pathological aspect in hypertrophic cardiomyopathy (HCM) which has not been yet fully understood. Also, a comprehensive evaluation of LA alterations in HCM is still lacking. Cardiac magnetic resonance imaging (cMRI) can precisely characterize LA function and structure. We sought to thoroughly assess LA remodelling using cMRI in patients with HCM. PATIENTS AND METHODS: We enrolled 105 patients with HCM and 105 healthy controls. LA parameters determined by cMRI comprise LA volume (LAV), total ejection fraction (LATF), total strain LA- εt, passive ejection fraction (LAPF), passive strain LA-εe, active ejection fraction (LAAF), active strain LA-εa. LA sphericity index (LASI) and LA strain were also determined. Parameters of LV systolic and diastolic functions were also assessed. RESULTS: LAV and LASI were significantly increased, while LA phasic functions were decreased in patients with HCM (p<.001). LATF was inversely correlated with LV long-axis strain (r= -0.466, p<.0001) and mass (r= -0.515, p<.0001), and as well with filling pressures, described by E/E' (r= -0.424, p<.0001). LA volumes, phasic functions and geometry were negatively associated with LV measurements, whereas a positive correlation between the LATF and LA strain (r = 0.496, p<.0001) was found. In addition, LAV was closely related to diastolic dysfunction severity (p<.0001). CONCLUSIONS: In patients with HCM, all three LA phasic functions were impaired, being directly related to LA enlargement. LASI and LA strain predicted LA reservoir function impairment.

A three-dimensional mathematical and computational model of necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is a severe disease that affects the gastrointestinal (GI) tract of premature infants. Different areas of NEC research have often been isolated from one another and progress on the role of the inflammatory response in NEC, on the dynamics of epithelial layer healing, and on the positive effects of breast feeding have not been synthesized to produce a more integrated understanding of the pathogenesis of NEC. We seek to synthesize these areas of research by creating a mathematical model that incorporates the current knowledge on these aspects. Unlike previous models that are based on ordinary differential equations, our mathematical model takes into account not only transient effects but also spatial effects. A system of nonlinear transient partial differential equations is solved numerically using cell-centered finite differences and an explicit Euler method. The model is used to track the evolution of a prescribed initial injured area in the intestinal wall. It is able to produce pathophysiologically realistic results; decreasing the initial severity of the injury in the system and introducing breast feeding to the system both lead to healthier overall simulations, and only a small fraction of epithelial injuries lead to full-blown NEC. In addition, in the model, changing the initial shape of the injured area can significantly alter the overall outcome of a simulation. This finding suggests that taking into account spatial effects may be important in assessing the outcome for a given NEC patient. This model can provide a platform with which to test competing hypotheses regarding pathological mechanisms of inflammation in NEC, suggest experimental approaches by which to clarify pathogenic drivers of NEC, and may be used to derive potential intervention strategies.

Image quality improvement of composed whole-spine MR images by applying a modified homomorphic filter--first results in cases of multiple myeloma.

To establish a modified homomorphic filter (BiFiC) for post-processing of composed MR images in clinical routine and to evaluate it in special regards to image quality and diagnostic safety. Twenty-three whole-spine examinations were post-processed with the filter. Qualitative image evaluation included documentation of lesions and their visualization at original and post-processed images. Variations of signal intensities were calculated pixel by pixel and visualized by color-coded maps. Quantitative data evaluation was conducted by region-by-region analysis with standardized regions of interests. The BiFiC filter could be implemented successfully on the scanner's software platform and used within clinical routine. Color-coded maps could demonstrate that the BiFiC filter improves the signal uniformity in all cases, including images with metallic artifacts caused by implants. The subjective image quality of the post-processed images was improved in 22 out of the 23 MR examinations; in one case it was rated as equal. All pathologies were visualized on post-processed images without the need of additional contrast adjustments. The implemented BiFiC filter significantly improves image signal homogeneity. The algorithm can consequently be integrated into clinical routine as an automatic image post-processing step.

[Generating statements at whole-body imaging with a workflow-optimized software tool--first experiences with multireader analysis]. / Befunderstellung bei der Ganzkörperbildgebung mittels einer workflowoptimierten Befundungssoftware--Erste Erfahrungen einer Multireader-Analyse.

INTRODUCTION: Due to technical innovations in sectional diagram methods, whole-body imaging has increased in importance for clinical radiology, particularly for the diagnosis of systemic tumor disease. Large numbers of images have to be evaluated in increasingly shorter time periods. The aim was to create and evaluate a new software tool to assist and automate the process of diagnosing whole-body datasets. MATERIAL AND METHODS: Thirteen whole-body datasets were evaluated by 3 readers using the conventional system and the new software tool. The times for loading the datasets, examining 5 different regions (head, neck, thorax, abdomen and pelvis/skeletal system) and retrieving a relevant finding for demonstration were acquired. Additionally a Student T-Test was performed. For qualitative analysis the 3 readers used a scale from 0 - 4 (0 = bad, 4 = very good) to assess dataset loading convenience, lesion location assistance, and ease of use. Additionally a kappa value was calculated. RESULTS: The average loading time was 39.7 s (+/- 5.5) with the conventional system and 6.5 s (+/- 1.4) (p < 0.01) with the new software tool. For the different regions (conventional system/new software tool), the time reduction for readers 1, 2, and 3 were as follows: in the head region 35.9 % (p < 0.01)/49.9 % (p < 0.01)/54.3 % (p < 0,01), in the neck region 48.5 % (p < 0.01)/52.6 % (p < 0.01)/59.4 % (p < 0.05), in the thorax region 59.1 % (p < 0.01)/56.2 % (p < 0.05)/62.1 % (p < 0.05), in the abdominal region 61.9 % (p < 0.01)/62.7 % (p < 0.05)/47.9 % (p < 0.01) and in the pelvis region 73.1 % (p < 0.01)/63.7 % (p < 0.05)/55 % (p < 0.01), respectively. 148.2 s (+/- 94.8) compared to 2.5 s (+/- 0.5) were required to retrieve a previously described finding (p < 0.01). With and without the new software tool the same number of metastases was found (p < 0.01, k > 0.9). The qualitative analysis showed a significant advantage with respect to convenience (p < 0.01, k > 0.9). CONCLUSION: Use of the new software can achieve a significant time savings when working with whole-body datasets with a constant quality of findings and a significant advantage with respect to convenience. As a result, the problem of evaluating examinations with thousands of images can be approached systematically.

[Treatment of osteochondritis dissecans of the knee: one-step procedure with bone grafting and matrix-supported autologous chondrocyte transplantation]. / Einzeitige Rekonstruktion osteochondraler Defekte am Kniegelenk bei Osteochondrosis dissecans.

AIM: The aim of this study was to establish and assess a one-step reconstruction procedure of deep osteochondral defects of the knee joint with bone grafting and matrix-supported autologous chondrocyte transplantation in osteochondritis dissecans. METHOD: Between 2004 and 200622 patients with osteochondral defects in the weight-bearing zone of the femoral condyles(ICRS OCD III and IV) were reconstructed simultaneously with bone grafting and matrix-supported autologous chondrocyte transplantation (NOVOCART 3D). All patients were analysed prospectively. RESULTS: 17 Males and 5 females(age 28.3, range: 17-49 years) were surgically treated with the above-mentioned novel method. Before reconstruction osteochondral defects had an average defect area of 4.8 (2.4-9.0) cm2 and a depth of between 4 and 15 mm. For reconstruction an average of 2.6 (1-6) monocortical cancellous bone cylinders (diameter 8mm) was used to fill the osseous defect and to reconstruct the subchondral bone plate with adequate positioning of the monocortical layer of the graft. Then a Matrix-ACT was used to cover the reconstructed subchondral bone plate. The average follow-up was 16 (6-36) months. The average Tegner activity score was 4 (3-7) of 10. The Lysholm-Gillquistscore and the Cincinnati Sports Medicine and Orthopedic Center score were significantly improved postoperatively. The IKDC-2000 questionnaire was also significantly increased by 50%. CONCLUSION: The simultaneous reconstruction of deep osteochondral detects of the knee joint with bone grafting and matrix-supported autologous chondrocyte transplantation in osteochondritis dissecans is a biological, one-step alternative to previously reported methods with encouraging first results.

[MRI monitoring of autologous hyaline cartilage grafts in the knee joint: a follow-up study over 12 months]. / MRT-Monitoring autologer Chondrozytentransplantate im Kniegelenk: Eine Verlaufsstudie über 12 Monate.

PURPOSE: To evaluate the suitability of different MR sequences for monitoring the stage of maturation of hyaline cartilage grafts in the knee joint and the early detection of complications like hypertrophy. In addition, it was analyzed whether indirect MR arthrography can indicate debonding of the graft. MATERIALS AND METHODS: MRI examinations were performed in 19 patients, aged 17 - 48 years, with autologous transplantation of a hyaline cartilage tissue graft after knee trauma. Examination dates were prior to transplantation to localize the defect, and 6 weeks, 3, 6 and 12 months after transplantation to control morphology and maturation of the autologous graft. Standard T2- and proton-density-weighted turbo spin echo (TSE) sequences and T1-weighted spin echo (SE) sequences were used, as well as gradient echo (GRE) sequences with and without magnetization transfer (MT) prepulses. In some cases, indirect MR arthrography was performed. RESULTS: Cartilage defect and the hyaline cartilage graft could be detected in all 19 patients. Hypertrophy of the graft could be found early in 3 patients and debonding in 1 patient. For depicting the graft a short time after surgery, T2-weighted TSE-sequences showed the best results. Six and 12 months after transplantation, spoiled 3D-GRE-sequences like FLASH3D (fast low angle shot) showed reduced artifacts due to magnetic residues from the surgery. Difference images from GRE-sequences with and without MT pulse provided high contrast between cartilage and surrounding tissue. The quantification of the MT effect showed an assimilation of the graft to the original cartilage within 12 months. Indirect MR arthrography showed subchondral contrast medium even 12 months after transplantation in 3 patients. CONCLUSION: MRI allows a reliable depiction of the hyaline graft and provides very early detection of complications like hypertrophy. The MT effect seems to be correlated with maturation of the graft and allows selective depiction of normal cartilage and engrafted cartilage.

Characterization of seven novel mutations in seven patients with GAMT deficiency.

Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessive error of creatine synthesis characterized by cerebral creatine deficiency, accumulation of guanidinoacetate, mental retardation, epilepsy and extrapyramidal signs. So far, six mutations have been identified in seven patients. We investigated seven new patients by screening the promoter, 3'UTR, and six exons and exon/intron boundaries using direct sequencing and denaturing gradient gel electrophoresis. The clinical and biochemical phenotype was characterized by scoring the degree of main clinical manifestations and by determination of urinary guanidinoacetate concentrations and of GAMT activity in fibroblasts / lymphoblasts, respectively. We identified 7 novel mutations, including c.64dupG (exon 1; 4/14 alleles); c.59G>C (exon 1; 3/14 alleles); c.491delG (exon 5; 2/14 alleles); c.160G>C (exon 1; 2/14 alleles); and c.152A>C (exon 1; 1/14 alleles); c.526dupG (exon 5; 1/14 alleles); c.521G>A (exon 5; 1/14 alleles), and two polymorphisms c.626C>T (exon 6) and c.459+71G>A (intron 4). Frameshift and missense mutations in exon 1 were prevalent in the 4 patients with the severe phenotype, however a clear genotype-phenotype correlation has not been established in the limited number of patients characterized so far.