Erich Sorantin

A Sequential 3D Thinning Algorithm and Its Medical Applications

Skeleton is a frequently applied shape feature to represent the general form of an object. Thinning is an iterative object reduction technique for producing a reasonable approximation to the skeleton in a topology preserving way. This paper describes a sequential 3D thinning algorithm for extracting medial lines of objects in (26, 6) pictures. Our algorithm has been successfully applied in medical image analysis. Three of the emerged applications (analysing airways, blood vessels, and colons) are also presented.

In vivo degradation performance of micro-arc-oxidized magnesium implants: A micro-CT study in rats

Biodegradable Mg alloys are of great interest for osteosynthetic applications because they do not require surgical removal after they have served their purpose. In this study, fast-degrading ZX50 Mg-based implants were surface-treated by micro-arc oxidation (MAO), to alter the initial degradation, and implanted along with untreated ZX50 controls in the femoral legs of 20 male Sprague-Dawley rats. Their degradation was monitored by microfocus computed tomography (μCT) over a total observation period of 24weeks, and histological analysis was performed after 4, 12 and 24weeks. While the MAO-treated samples showed almost no corrosion in the first week, they revealed an accelerated degradation rate after the third week, even faster than that of the untreated ZX50 implants. This increase in degradation rate can be explained by an increase in the surface-area-to-volume ratio of MAO-treated implants, which degrade inhomogeneously via localized corrosion attacks. The histological analyses show that the initially improved corrosion resistance of the MAO implants has a positive effect on bone and tissue response: The reduced hydrogen evolution (due to reduced corrosion) makes possible increased osteoblast apposition from the very beginning, thus generating a stable bone-implant interface. As such, MAO treatment appears to be very interesting for osteosynthetic implant applications, as it delays implant degradation immediately after implantation, enhances fracture stabilization, minimizes the burden on the postoperatively irritated surrounding tissue and generates good bone-implant connections, followed by accelerated degradation in the later stage of bone healing.

Segmentation of interwoven 3d tubular tree structures utilizing shape priors and graph cuts

The segmentation of tubular tree structures like vessel systems in volumetric datasets is of vital interest for many medical applications. We present a novel approach that allows to simultaneously separate and segment multiple interwoven tubular tree structures. The algorithm consists of two main processing steps. First, the tree structures are identified and corresponding shape priors are generated by using a bottom-up identification of tubular objects combined with a top-down grouping of these objects into complete tree structures. The grouping step allows us to separate interwoven trees and to handle local disturbances. Second, the generated shape priors are utilized for the intrinsic segmentation of the different tubular systems to avoid leakage or undersegmentation in locally disturbed regions. We have evaluated our method on phantom and different clinical CT datasets and demonstrated its ability to correctly obtain/separate different tree structures, accurately determine the surface of tubular tree structures, and robustly handle noise, disturbances (e.g., tumors), and deviations from cylindrical tube shapes like for example aneurysms.

Spiral-CT-based assessment of tracheal stenoses using 3-D-skeletonization

Demonstration of a technique for three-dimensional (3-D) assessment of tracheal-stenoses, regarding site, length and degree, based on spiral computed tomography (S-CT). S-CT scanning and automated segmentation of the laryngo-tracheal tract (LTT) was followed by the extraction of the LTT medial axis using a skeletonization algorithm. Orthogonal to the medial axis the LTT 3-D cross-sectional profile was computed and presented as line charts, where degree and length was obtained. Values for both parameters were compared between 36 patients and 18 normal controls separately. Accuracy and precision was derived from 17 phantom studies. Average degree and length of tracheal stenoses was found to be 60.5% and 4.32 cm in patients compared with minor caliber changes of 8.8% and 2.31 cm in normal controls (p /spl Lt/ 0.0001). For the phantoms an excellent correlation between the true and computed 3-D cross-sectional profile was found (p /spl Lt/ 0.005) and an accuracy for length and degree measurements of 2.14 mm and 2.53% respectively could be determined. The corresponding figures for the precision were found to be 0.92 mm and 2.56%. LTT 3-D cross-sectional profiles permit objective, accurate and precise assessment of LTT caliber changes. Minor LTT caliber changes can be observed even in normals and, in case of an otherwise normal S-CT study, can be regarded as artifacts.

Insulin and Hippocampus Activation in Response to Images of High-Calorie Food in Normal Weight and Obese Adolescents

Responsiveness to food cues, especially those associated with high‐calorie nutrients may be a factor underlying obesity. An increased motivational potency of foods appears to be mediated in part by the hippocampus. To clarify this, we investigated by means of 3‐T magnetic resonance imaging (MRI) the activation of the hippocampus and associated brain structures in response to pictures of high‐calorie and low‐calorie foods in 12 obese and 12 normal‐weight adolescents. To investigate the relationship between neuronal activation patterns (e.g., hippocampus) to the caloric content of food images and plasma insulin levels, we performed a multiple regression analysis. Interestingly, a significant positive correlation between fasting plasma levels of insulin, waist circumference, and right hippocampal activation was seen after stimulation with high‐caloric food images. BMI values did not correlate significantly with the hippocampal activation. On the other hand, we found a significant negative correlation in response to high‐caloric food images and the plasma levels of insulin in the medial right gyrus frontalis superior and in the left thalamus. In summary, our data show that insulin is importantly involved in the central regulation of food intake. The significant positive relationship between hippocampal activation after stimulation with high‐caloric food images, plasma insulin levels, and waist circumference suggests a permissive role of insulin signaling pathways in the hippocampal control of eating behavior. Interestingly, only the waist circumference, as a main indicator of abdominal obesity, correlated significantly with the hippocampal activation patterns, and not the BMI.

Systolic Right Ventricular Function in Children and Young Adults with Pulmonary Artery Hypertension Secondary to Congenital Heart Disease and Tetralogy of Fallot: Tricuspid Annular Plane Systolic Excursion (TAPSE) and Magnetic Resonance Imaging Data

OBJECTIVE   The tricuspid annular plane systolic excursion (TAPSE), as echocardiographic index to assess right ventricular (RV) systolic function, has not been investigated thoroughly in children and young adults with tetralogy of Fallot (TOF) and pulmonary artery hypertension secondary to congenital heart disease (PAH-CHD). PATIENTS   TAPSE values of 49 patients with PAH-CHD and 156 patients with TOF were compared with age-matched normal subjects. TAPSE values were also compared with RV ejection fraction (RVEF) and RV indexed end-diastolic volume (RVEDVi) determined by magnetic resonance imaging in PAH-CHD and TOF patients. RESULTS   Patients with a PAH-CHD showed a positive correlation between TAPSE with RVEF (r= 0.81; P < 0.001) and a negative correlation between TAPSE with RVEDVi (r=-0.67; P < 0.001). Similarly, in our TOF patients, a positive correlation between TAPSE with RVEF (r= 0.65; P < 0.001) and a negative correlation between TAPSE with RVEDVi (r=-0.42; P < 0.001) was seen. CONCLUSIONS   Significant pressure overload in PAH-CHD patients and volume overload in TOF patients lead to a decreased systolic RV function, determined by TAPSE and magnetic resonance imaging and to increased RVEDVi values, determined by MRI, with time.

Systolic right ventricular function in pediatric and adolescent patients with tetralogy of Fallot: echocardiography versus magnetic resonance imaging.

OBJECTIVE The tricuspid annular plane systolic excursion (TAPSE) as an echocardiographic index to assess right ventricular (RV) systolic function has not been investigated thoroughly in pediatric patients and adolescents with tetralogy of Fallot (TOF) after surgical repair. METHODS TAPSE was determined in 131 patients with TOF and 252 age-matched normal subjects. TAPSE values were compared with RV ejection fraction (EF) and indexed RV end-diastolic volume (EDVi) determined by magnetic resonance imaging in a cross-sectional study design. TAPSE values were also correlated to QRS duration (QRSd) determined by electrocardiogram. RESULTS The TAPSE values showed a positive correlation with age in normal subjects. The TAPSE was not decreased in infants and young children with TOF compared with normal subjects. A significant reduction of TAPSE values with increasing time after surgical repair was observed. After a mean of 7 years after surgical repair, the TAPSE values become significantly reduced compared with age-matched controls, being below the lower bound of -2 standard deviations. A positive correlation between TAPSE with RVEF and a negative correlation between TAPSE with RVEDVi were observed. A significant positive correlation was found between QRSd and RVEDVi, and a significant negative correlation was found between QRSd and RVEF. CONCLUSION Although TAPSE was initially preserved, impaired TAPSE was observed with increasing time after surgical repair in pediatric patients with TOF.

CT-based virtual tracheobronchoscopy in children: comparison with axial CT and multiplanar reconstruction: preliminary results

Background: 3D post-processing of spiral-CT (S-CT) data using perspective projection allows the generation of virtual views similar to endoscopy. Objective: To evaluate whether simultaneous reading of axial S-CT, multiplanar reconstruction (MPR) and virtual tracheobronchoscopy (VTB) is more precise and accurate than reading of axial S-CT and MPR alone in paediatric patients. Materials and methods: S-CT studies of 15 symptomatic and 4 normal patients were investigated. Two radiologists independently read two sets of images for airway abnormalities: first axial CT and MPR, followed by axial CT, MPR and VTB. A final decision was later made by consensus. All results were compared to fibre-optic bronchoscopy (FTB). Interobserver agreement was used as an indicator of precision for the display technique used. Results: At reading of axial S-CT and MPR an interobserver agreement of 89.5% (κ=0.776, P<0.00103) was found. Based on the consensus decision, a diagnostic accuracy of 89.5% at a sensitivity 86.6% and specificity of 100% (κ=0.776, 95% CI 0.491–1.062, P<0.00103) was achieved. At reporting on axial S-CT, MPR and VTB, all cases were classified correctly by both readers, indicating 100% accuracy, interobserver agreement, sensitivity and specificity (κ=1.00, 95% CI 1.0–1.0, P<0.000258). Conclusions: The simultaneous display of axial S-CT, MPR and VTB raises the precision, accuracy and sensitivity of radiological reports.

Virtual colon flattening

We present a new method to visualize virtual endoscopic views. We propose to flatten the organ by the direct projection of the surface onto a set of cylinders. Two sampling strategies are presented and the introduced distortions are studied. A non-photorealistic technique is presented to enhance the perception of the images. Finally, an approximate but real-time endoscopic fly-through is possible by using the data obtained by the projection technique.

Delayed presentation of congenital diaphragmatic hernia

Eight patients aged 1 month up to nine years with congenital diaphragmatic hernias (seven left sided postero-lateral, one right-sided antero-medial), who presented outside of the neonatal period, are reported, four are described in detail. Radiographic presentation was obvious in four patients, simulated inflammatory lung disease in one and pneumothorax in two. In one patient a Morgagni hernia was primarily missed. Two had previous normal chest X-rays. All cases with herniated bowel showed “connecting” bowel segements passing through the diaphragmatic deffect. Primarily the lack of awareness of delayed presentation of congenital diaphragmatic hernia in children with uncharacteristic thoracic and/or abdominal symptoms led to an undesirable time delay between first chest X-ray and surgery up to 16 months in four of our cases. Life threatening complications can be the consequence of delayed diagnosis as in one of our cases.