Diana Wald

Automatic quantification of subcutaneous and visceral adipose tissue from whole‐body magnetic resonance images suitable for large cohort studies

To develop an automated method with which to distinguish metabolically different adipose tissues in a large number of subjects using whole‐body magnetic resonance imaging (MRI) datasets for improving the understanding of chronic disease risk predictions associated with distinct adipose tissue compartments.

Validation of Anthropometric Indices of Adiposity against Whole-Body Magnetic Resonance Imaging – A Study within the German European Prospective Investigation into Cancer and Nutrition (EPIC) Cohorts

Background In epidemiological studies, measures of body fat generally are obtained through anthropometric indices such as the body mass index (BMI), waist (WC), and hip circumferences (HC). Such indices, however, can only provide estimates of a person’s true body fat content, overall or by adipose compartment, and may have limited accuracy, especially for the visceral adipose compartment (VAT). Objective To determine the extent to which different body adipose tissue compartments are adequately predicted by anthropometry, and to identify anthropometric measures alone, or in combination to predict overall adiposity and specific adipose tissue compartments, independently of age and body size (height). Methods In a sub-study of 1,192 participants of the German EPIC (European Prospective Investigation into Cancer and Nutrition) cohorts, whole-body MRI was performed to determine adipose and muscle tissue compartments. Additional anthropometric measurements of BMI, WC and HC were taken. Results After adjusting for age and height, BMI, WC and HC were better predictors of total body volume (TBV), total adipose tissue (TAT) and subcutaneous adipose tissue (SAT) than for VAT, coronary adipose tissue (CAT) and skeletal muscle tissue (SMT). In both sexes, BMI was the best predictor for TBV (men: r = 0.72 [0.68–0.76], women: r = 0.80 [0.77–0.83]) and SMT (men: r = 0.52 [0.45–0.57], women: r = 0.48 [0.41–0.54]). WC was the best predictor variable for TAT (r = 0.48 [0.41–0.54]), VAT (r = 0.44 [0.37–0.50]) and CAT (r = 0.34 [0.26–0.41]) (men), and for VAT (r = 0.42 [0.35–0.49]) and CAT (r = 0.29 [0.22–0.37]) (women). BMI was the best predictor for TAT (r = 0.49 [0.43–0.55]) (women). HC was the best predictor for SAT (men (r = 0.39 [0.32–0.45]) and women (r = 0.52 [0.46–0.58])). Conclusions Especially the volumes of internal body fat compartments are poorly predicted by anthropometry. A possible implication may be that associations of chronic disease risks with the sizes of internal body fat as measured by BMI, WC and HC may be strongly underestimated.

Regular three-dimensional presentations improve in the identification of surgical liver anatomy - A randomized study

BackgroundThree-dimensional (3D) presentations enhance the understanding of complex anatomical structures. However, it has been shown that two dimensional (2D) “key views” of anatomical structures may suffice in order to improve spatial understanding. The impact of real 3D images (3Dr) visible only with 3D glasses has not been examined yet. Contrary to 3Dr, regular 3D images apply techniques such as shadows and different grades of transparency to create the impression of 3D.This randomized study aimed to define the impact of both the addition of key views to CT images (2D+) and the use of 3Dr on the identification of liver anatomy in comparison with regular 3D presentations (3D).MethodsA computer-based teaching module (TM) was used. Medical students were randomized to three groups (2D+ or 3Dr or 3D) and asked to answer 11 anatomical questions and 4 evaluative questions. Both 3D groups had animated models of the human liver available to them which could be moved in all directions.Results156 medical students (57.7% female) participated in this randomized trial. Students exposed to 3Dr and 3D performed significantly better than those exposed to 2D+ (p < 0.01, ANOVA). There were no significant differences between 3D and 3Dr and no significant gender differences (p > 0.1, t-test). Students randomized to 3D and 3Dr not only had significantly better results, but they also were significantly faster in answering the 11 anatomical questions when compared to students randomized to 2D+ (p < 0.03, ANOVA). Whether or not “key views” were used had no significant impact on the number of correct answers (p > 0.3, t-test).ConclusionThis randomized trial confirms that regular 3D visualization improve the identification of liver anatomy.

Lack of centrioles and primary cilia in STIL−/− mouse embryos

Although most animal cells contain centrosomes, consisting of a pair of centrioles, their precise contribution to cell division and embryonic development is unclear. Genetic ablation of STIL, an essential component of the centriole replication machinery in mammalian cells, causes embryonic lethality in mice around mid gestation associated with defective Hedgehog signaling. Here, we describe, by focused ion beam scanning electron microscopy, that STIL−/− mouse embryos do not contain centrioles or primary cilia, suggesting that these organelles are not essential for mammalian development until mid gestation. We further show that the lack of primary cilia explains the absence of Hedgehog signaling in STIL−/− cells. Exogenous re-expression of STIL or STIL microcephaly mutants compatible with human survival, induced non-templated, de novo generation of centrioles in STIL−/− cells. Thus, while the abscence of centrioles is compatible with mammalian gastrulation, lack of centrioles and primary cilia impairs Hedgehog signaling and further embryonic development.

An automatic segmentation and reconstruction of mandibular structures from CT-data

In any medical data analysis a good visualization of specific parts or tissues are fundamental in order to perform accurate diagnosis and treatments. For a better understanding of the data, a segmentation process of the images to isolate the area or region of interest is important to be applied beforehand any visualization step. In this paper we present a method for mandibular structure surface extraction and reconstruction from CT-data images. We tested several methods and algorithms in order to find a fast and feasible approach that could be applicable in clinical procedures, providing practical and efficient tools for mandibular structures analysis.

Computer-assisted analysis of annuloplasty rings

Over 40.000 annuloplasty rings are implanted each year in the United States to treat mitral regurgitation. The rings come in different sizes and shapes. However it is unclear, which ring is most suitable for the individual patient. Here we present a preoperative annuloplasty planning software to determine an eligible ring. It provides fast interactive methods to create 4D mitral annulus models based on arbitrary image data. Created models can be analyzed geometrically and compared to existing annuloplasty ring models. This way, forces caused by a specific annuloplasty ring can visualized, which enables preoperative simulation and eventually improves operation results. Using our software, we evaluated the size changes caused by five commercially available annuloplasty rings on the mitral annuli of 39 patients. The results suggest that the annuloplasty ring should be selected for each patient specifically.

Comparison of Segmentation Algorithms for the Zebrafish Heart in Fluorescent Microscopy Images

The zebrafish embryo is a common model organism for cardiac development and genetics. However, the current method of analyzing the embryo heart images is still mainly the manual and visual inspection through the microscope by scoring embryos visually - a very laborious and expensive task for the biologist. We propose to automatically segment the embryo cardiac chambers from fluorescent microscopic video sequences, allowing morphological and functional quantitative features of cardiac activity to be extracted. Several methods are presented and compared within a large range of images, varying in quality, acquisition parameters, and embryos position. Despite such variability in the images, the best method reaches a 70% of accuracy, allowing reducing biologists workload by automating some of the tedious manual segmentation tasks.

Intraoperative measurements on the mitral apparatus using optical tracking: a feasibility study

Mitral valve reconstruction is a widespread surgical method to repair incompetent mitral valves. During reconstructive surgery the judgement of mitral valve geometry and subvalvular apparatus is mandatory in order to choose for the appropriate repair strategy. To date, intraoperative analysis of mitral valve is merely based on visual assessment and inaccurate sizer devices, which do not allow for any accurate and standardized measurement of the complex three-dimensional anatomy. We propose a new intraoperative computer-assisted method for mitral valve measurements using a pointing instrument together with an optical tracking system. Sixteen anatomical points were defined on the mitral apparatus. The feasibility and the reproducibility of the measurements have been tested on a rapid prototyping (RP) heart model and a freshly exercised porcine heart. Four heart surgeons repeated the measurements three times on each heart. Morphologically important distances between the measured points are calculated. We achieved an interexpert variability mean of 2.28 +/- 1:13 mm for the 3D-printed heart and 2.45 +/- 0:75 mm for the porcine heart. The overall time to perform a complete measurement is 1-2 minutes, which makes the method viable for virtual annuloplasty during an intervention.

Automated quantification of adipose and skeletal muscle tissue in whole-body MRI data for epidemiological studies

The ratio between the amount of adipose and skeletal muscle tissue is an important determinant of metabolic health. Recent developments in MRI technology allow whole body scans to be performed for accurate assessment of body composition. In the present study, a total of 194 participants underwent a 2-point Dixon MRI sequence of the whole body. A fully automated image segmentation method quantifies the amount of adipose and skeletal muscle tissue by applying standard image processing techniques including thresholding, region growing and morphological operators. The adipose tissue is further divided into subcutaneous and visceral adipose tissue by using statistical shape models. All images were visually inspected. The quantitative analysis was performed on 44 whole-body MRI data using manual segmentations as ground truth data. We achieved 3.3% and 6.3% of relative volume difference between the manual and automated segmentation of subcutaneous and visceral adipose tissue, respectively. The validation of skeletal muscle tissue segmentation resulted in a relative volume difference of 7.8 ± 4.2% and a volumetric overlap error of 6.4 ± 2.3 %. To our knowledge, we are first to present a fully automated method which quantifies adipose and skeletal muscle tissue in whole-body MRI data. Due to the fully automated approach, results are deterministic and free of user bias. Hence, the software can be used in large epidemiological studies for assessing body fat distribution and the ratio of adipose to skeletal muscle tissue in relation to metabolic disease risk.

Gestaltung patientenspezifischer Annuloplastieringe

Mitralinsuffizienz ist eine weit verbreitete Krankheit, welche durch die Implantation von Annuloplastieringen behandelt werden kann. Die Wahl eines geeigneten Ringes gestaltet sich aufgrund uneindeutiger Mess- und Selektionskriterien jedoch schwierig. Durch das vorgestellte Verfahren zur patientenspezifischen Gestaltung von Annuloplastieringen wird eine gute Passgenauigkeit gewahrleistet. Das individuelle Ringdesign ermoglicht eine geringere maximale Deformation des Mitralannulus uber den Herzzyklus gegenuber den untersuchten kommerziellen Ringe, wodurch die Gefahr einer Ringdehinszenz gemindert werden kann. Durch die Herstellung eines entsprechenden implantierfahigen Annuloplastierings mit Hilfe von Rapid-Prototyping Technologien wird zus atzlich gezeigt, dass eine Einbindung in die Klinik zeitlich und preislich vertretbar ist.