Modeling Patient-Specific Deformable Mitral Valves

Medical imaging has advanced enormously over the last few decades, revolutionizing patient diagnostics and care. At the same time, additive manufacturing has emerged as a means of reproducing physical shapes and models previously not possible. In combination, they have given rise to 3-dimensional (3D) modeling, an entirely new technology for physicians. In an era in which 3D imaging has become a standard for aiding in the diagnosis and treatment of cardiac disease, this visualization now can be taken further by bringing the patient's anatomy into physical reality as a model. The authors describe the generalized process of creating a model of cardiac anatomy from patient images and their experience creating patient-specific dynamic mitral valve models. This involves a combination of image processing software and 3D printing technology. In this article, the complexity of 3D modeling is described and the decision-making process for cardiac anesthesiologists is summarized. The management of cardiac disease has been altered with the emergence of 3D echocardiography, and 3D modeling represents the next paradigm shift.

The role of visual and direct force feedback in robotics-assisted mitral valve annuloplasty

BACKGROUND

The objective of this work was to determine the effect of both direct force feedback and visual force feedback on the amount of force applied to mitral valve tissue during ex vivo robotics-assisted mitral valve annuloplasty.

METHODS

A force feedback-enabled master-slave surgical system was developed to provide both visual and direct force feedback during robotics-assisted cardiac surgery. This system measured the amount of force applied by novice and expert surgeons to cardiac tissue during ex vivo mitral valve annuloplasty repair.

RESULTS

The addition of visual (2.16 ± 1.67), direct (1.62 ± 0.86), or both visual and direct force feedback (2.15 ± 1.08) resulted in lower mean maximum force applied to mitral valve tissue while suturing compared with no force feedback (3.34 ± 1.93 N; P < 0.05).

CONCLUSIONS

To achieve better control of interaction forces on cardiac tissue during robotics-assisted mitral valve annuloplasty suturing, force feedback may be required.

Comparative study of all Salmonella enterica serovar Enteritidis strains isolated from food and food animals in Greece from 2008 to 2010 with clinical isolates

The aim of the present work was to study the epidemiology of Salmonella enterica serovar Enteritidis (S. Enteritidis) in Greece, comparing all the food and food animal isolates during a 3-year period with clinical isolates. Submission of the generated data to the PulseNet Europe database was carried out in order to study the population structure of this particular serovar and indicate possible connections with European strains. One hundred and sixty-eight (168) S. Enteritidis strains of human, animal, and food origin, isolated during the period 2008-2010 in Greece, were studied. Strains were characterized by phenotypic (antibiotic resistance) and molecular [pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST)] methods. PFGE revealed 39 XbaI, 48 BlnI, and 80 XbaI-BlnI distinct pulsotypes, suggesting several clones circulating through the food chain and multiple sources of transmission. Submission to the PulseNet Europe database indicated that PFGE profile SENTXB.0001, the most common PFGE profile in Europe, was also predominant in Greece (33.3 %). MLST showed that all the strains studied shared the same sequence type (ST11), representing the most common ST in Europe. High rates of resistance to nalidixic acid were observed among human and poultry isolates (~25 %), indicating the potential fluoroquinolone treatment failure. Our data suggest that strains originating from multiple reservoirs circulated in Greece through the food chain during the study period. Predominant profiles in Greece were common to PulseNet Europe profiles, indicating similarities between the S. Enteritidis populations in Greece and Europe.

Diagnostic quality assessment of compressed sensing accelerated magnetic resonance neuroimaging

PURPOSE

To determine the efficacy of compressed sensing (CS) reconstructions for specific clinical magnetic resonance neuroimaging applications beyond more conventional acceleration techniques such as parallel imaging (PI) and low-resolution acquisitions.

MATERIALS AND METHODS

Raw k-space data were acquired from five healthy volunteers on a 3T scanner using a 32-channel head coil using T2 -FLAIR, FIESTA-C, time of flight (TOF), and spoiled gradient echo (SPGR) sequences. In a series of blinded studies, three radiologists independently evaluated CS, PI (GRAPPA), and low-resolution images at up to 5× accelerations. Synthetic T2 -FLAIR images with artificial lesions were used to assess diagnostic accuracy for CS reconstructions.

RESULTS

CS reconstructions were of diagnostically acceptable quality at up to 4× acceleration for T2 -FLAIR and FIESTA-C (average qualitative scores 3.7 and 4.3, respectively, on a 5-point scale at 4× acceleration), and at up to 3× acceleration for TOF and SPGR (average scores 4.0 and 3.7, respectively, at 3× acceleration). The qualitative scores for CS reconstructions were significantly better than low-resolution images for T2 -FLAIR, FIESTA-C, and TOF and significantly better than GRAPPA for TOF and SPGR (Wilcoxon signed rank test, P < 0.05) with no significant difference found otherwise. Diagnostic accuracy was acceptable for both CS and low-resolution images at up to 3× acceleration (area under the ROC curve 0.97 and 0.96, respectively.)

CONCLUSION

Mild to moderate accelerations are possible for those sequences by a combined CS and PI reconstruction. Nevertheless, for certain sequences/applications one might mildly reduce the acquisition time by appropriately reducing the imaging resolution rather than the more complicated CS reconstruction. J. Magn. Reson. Imaging 2016;44:433-444.

The DTI Challenge: Toward Standardized Evaluation of Diffusion Tensor Imaging Tractography for Neurosurgery

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) tractography reconstruction of white matter pathways can help guide brain tumor resection. However, DTI tracts are complex mathematical objects and the validity of tractography-derived information in clinical settings has yet to be fully established. To address this issue, we initiated the DTI Challenge, an international working group of clinicians and scientists whose goal was to provide standardized evaluation of tractography methods for neurosurgery. The purpose of this empirical study was to evaluate different tractography techniques in the first DTI Challenge workshop.

METHODS

Eight international teams from leading institutions reconstructed the pyramidal tract in four neurosurgical cases presenting with a glioma near the motor cortex. Tractography methods included deterministic, probabilistic, filtered, and global approaches. Standardized evaluation of the tracts consisted in the qualitative review of the pyramidal pathways by a panel of neurosurgeons and DTI experts and the quantitative evaluation of the degree of agreement among methods.

RESULTS

The evaluation of tractography reconstructions showed a great interalgorithm variability. Although most methods found projections of the pyramidal tract from the medial portion of the motor strip, only a few algorithms could trace the lateral projections from the hand, face, and tongue area. In addition, the structure of disagreement among methods was similar across hemispheres despite the anatomical distortions caused by pathological tissues.

CONCLUSIONS

The DTI Challenge provides a benchmark for the standardized evaluation of tractography methods on neurosurgical data. This study suggests that there are still limitations to the clinical use of tractography for neurosurgical decision making.

Vertebroplasty Performance on Simulator for 19 Surgeons Using Hierarchical Task Analysis

We present a unique simulator-based methodology for assessing both technical and nontechnical (cognitive) skills for surgical trainees while immersed in a complete medical simulation environment. Further, we have included two crisis scenarios which allow for the evaluation of the effect of cognitive strategy selection on the low-level surgical skills. Training these mixed-mode scenarios can thereby be evaluated on our platform, allowing for improved assessment and a stronger foundation for credentialing, with the potential to reduce the occurrence of adverse events in the operating room. Scientific evaluation and validation of our work is conducted together with 19 junior surgeons in order to achieve the following goals: 1) to provide a qualitative measure of usability, 2) to assess vertebroplasty technical performance of the surgeon, and 3) to explore the relationship between mental workload and surgical performance during crisis. Our results indicate that: 1) the surgeons scored the face validity of our modeled simulation environment very highly ( 4.68 ±0.48, using a 5-point Likert scale), 2) surgeon training enabled completion of tasks more quickly, and 3) the introduction of crisis scenarios negatively affected the surgeons' objective performance. Taken together, our results underscore the need to develop realistic simulation environments that prepare young residents to respond to emergent events in the operating room.

A multi-country Salmonella Enteritidis phage type 14b outbreak associated with eggs from a German producer: ‘near real-time’ application of whole genome sequencing and food chain investigations, United Kingdom, May to September 2014

Binary file ES_Abstracts_Final_ECDC.txt matches

Phenotypic and molecular characterization of multidrug-resistant Salmonella enterica serovar Hadar in Greece, from 2007 to 2010

All 120 strains of Salmonella enterica serovar Hadar isolated during 2007-2010 in Greece were characterized by phenotypic and molecular methods. High rates of resistance to nalidixic acid (92%) and low levels of ciprofloxacin resistance (88%) were observed. Pulsenet-pulsed field gel electrophoresis profile SHADXB.0001 was predominant in Greece (58%) as in Europe but PT1, a rare phage type in Europe, was frequent in Greece (56%). The SHADXB.0001 and PT1 clone (38%) were found in humans, animals and food of animal origin with R-type ApSpTNxpCp being predominant (25%). The data indicate that this clone (possibly endemic) was circulating through the food chain in Greece during the study period.

High-resolution 3-dimensional late gadolinium enhancement scar imaging in surgically corrected Tetralogy of Fallot: clinical feasibility of volumetric quantification and visualization

BACKGROUND

The extent of surgical scarring in Tetralogy of Fallot (TOF) may be a marker of adverse outcomes and provide substrate for ventricular arrhythmia. In this study we evaluate the feasibility of high resolution three dimensional (3D) late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) for volumetric scar quantification in patients with surgically corrected TOF.

METHODS

Fifteen consecutive patients underwent 3D LGE imaging with 3 Tesla CMR using a whole-heart, respiratory-navigated technique. A novel, signal-histogram based segmentation technique was tested for the quantification and modeling of surgical scar. Total scar volume was compared to the gold standard manual expert segmentation. The feasibility of segmented scar fusion to matched coronary CMR data for volumetric display was explored.

RESULTS

Image quality sufficient for 3D scar segmentation was acquired in fourteen patients. Mean patient age was 32.2 ± 11.9 years (range 21 to 57 years) with mean right ventricle (RV) ejection fraction (EF) of 53.9 ± 9.2% and mean RV end diastolic volume of 117.0 ± 41.5 mL/m². The mean total scar volume was 11.1 ± 8.2 mL using semi-automated 3D segmentation with excellent correlation to manual expert segmentation (r = 0.99, bias = 0.89 mL, 95% CI -1.66 to 3.44). The mean segmentation time was significantly reduced using the novel semi-automated segmentation technique (10.1 ± 2.6 versus 45.8 ± 12.6 minutes). Excellent intra-observer and good inter-observer reproducibility was observed.

CONCLUSION

3D high resolution LGE imaging with semi-automated scar segmentation is clinically feasible among patients with surgically corrected TOF and shows excellent accuracy and reproducibility. This approach may offer a valuable clinical tool for risk prediction and procedural planning among this growing population.

A multi-country outbreak of Salmonella Newport gastroenteritis in Europe associated with watermelon from Brazil, confirmed by whole genome sequencing: October 2011 to January 2012

In November 2011, the presence of Salmonella Newport in a ready-to-eat watermelon slice was confirmed as part of a local food survey in England. In late December 2011, cases of S. Newport were reported in England, Wales, Northern Ireland, Scotland, Ireland and Germany. During the outbreak, 63 confirmed cases of S. Newport were reported across all six countries with isolates indistinguishable by pulsed-field gel electrophoresis from the watermelon isolate.A subset of outbreak isolates were whole-genome sequenced and were identical to, or one single nucleotide polymorphism different from the watermelon isolate.In total, 46 confirmed cases were interviewed of which 27 reported watermelon consumption. Further investigations confirmed the outbreak was linked to the consumption of watermelon imported from Brazil.Although numerous Salmonella outbreaks associated with melons have been reported in the United States and elsewhere, this is the first of its kind in Europe.Expansion of the melon import market from Brazil represents a potential threat for future outbreaks. Whole genome sequencing is rapidly becoming more accessible and can provide a compelling level of evidence of linkage between human cases and sources of infection,to support public health interventions in global food markets.

Sirolimus: a therapeutic advance for dermatologic disease

Sirolimus, also known as rapamycin (SRL, Rapamune®), was approved in 1999 by the US Food and Drug Administration to prevent graft rejection in renal transplantation. As a member of the mammalian target of rapamycin (mTOR) inhibitor class, its potent immunosuppressant, anti-angiogenic and anti-proliferative properties are well recognized. When compared to other immunosuppressants, SRL has a lower risk of renal, neurologic and lymphoproliferative complications. It has become a promising treatment modality for angiofibromas, Kaposi's sarcoma and other inflammatory and malignant disorders of the skin. With the recent discovery that mTOR inhibitors extend the lifespan of mice, sirolimus and other rapamycin analogs (rapalogs) are emerging as therapeutic targets for the treatment and prevention of age-related diseases.

Regional assessment of cardiac left ventricular myocardial function via MRI statistical features

Automating the detection and localization of segmental (regional) left ventricle (LV) abnormalities in magnetic resonance imaging (MRI) has recently sparked an impressive research effort, with promising performances and a breadth of techniques. However, despite such an effort, the problem is still acknowledged to be challenging, with much room for improvements in regard to accuracy. Furthermore, most of the existing techniques are labor intensive, requiring delineations of the endo- and/or epi-cardial boundaries in all frames of a cardiac sequence. The purpose of this study is to investigate a real-time machine-learning approach which uses some image features that can be easily computed, but that nevertheless correlate well with the segmental cardiac function. Starting from a minimum user input in only one frame in a subject dataset, we build for all the regional segments and all subsequent frames a set of statistical MRI features based on a measure of similarity between distributions. We demonstrate that, over a cardiac cycle, the statistical features are related to the proportion of blood within each segment. Therefore, they can characterize segmental contraction without the need for delineating the LV boundaries in all the frames. We first seek the optimal direction along which the proposed image features are most descriptive via a linear discriminant analysis. Then, using the results as inputs to a linear support vector machine classifier, we obtain an abnormality assessment of each of the standard cardiac segments in real-time. We report a comprehensive experimental evaluation of the proposed algorithm over 928 cardiac segments obtained from 58 subjects. Compared against ground-truth evaluations by experienced radiologists, the proposed algorithm performed competitively, with an overall classification accuracy of 86.09% and a kappa measure of 0.73.