Daniel Stein

Deutsches Krebsforschungszentrum, Heidelburg, Baden-Württemberg, Germany

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Publications (9)6.95 Total impact

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    ABSTRACT: Randomized studies have already described the advantages of three dimensional (3D) presentations in understanding complex spatial interactions. However, the clinical setting is mainly characterized by presentations of two dimensional (2D) images. This study evaluates whether training on 3D presentation enhances the understanding of 2D images. A teaching module was used consisting of one learning part and two examination parts (EP). Students were randomized to training with either 2D or 3D. This study of 73 students showed that training on 3D presentations did not improve the ability to interpret 2D images. Further, the results revealed no significant differences between the results of Week 1 (2D: M = 6.5, SD = 1.8; 3D: M = 6.6, SD = 1.4; p > .95) and Week 2 (2D: M = 6.1, SD = 1.9; 3D: M = 6.0, SD = 1.4; p > .7). There were no significant gender differences. However, students randomized to 2D who completed only the first EP performed significantly worse if compared to students who completed both EP ( p = .04). This randomized controlled study shows that correct interpretation of 2D imaging does not differ in students trained with either 3D or 2D.
    Teaching and Learning in Medicine 04/2012; 24(2):140-8. · 0.94 Impact Factor
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    ABSTRACT: To investigate the diagnostic performance of a cine magnetic resonance imaging (MRI) sequence in the visualization and detection of impaired bowel peristalsis. In all, 91 consecutive patients (mean age 45 years) were prospectively examined on a 1.5 T system and stratified into a surgery group (n = 22) and a nonsurgery group (n = 69). A coronal fast imaging with steady-state precession (TrueFISP) sequence with 30 acquisitions per slice covered the abdomen in 10-15 slices each 7-12 mm thick (temporal resolution: 6-8 sec per frame). Image evaluation for reduced bowel peristalsis and relevant bowel stenosis was compared to surgical findings or clinical follow-up. Cine MRI reached 96% accuracy (94% sensitivity; 100% specificity) in detecting a relevant reduction in bowel peristalsis and 85% of relevant stenosis was identified in the surgery group. Twenty of 69 patients of the nonsurgery group showed reduced peristalsis on cine MR which was attributed to underlying disease; 49/69 patients in this group had no findings on cine MR and were uneventfully followed up. Cine MRI of the bowel provides functional information of bowel passage. The visualization of a reduction in peristalsis may improve the assessment of the functional impact of suspected bowel adhesions or stenosis. Standard bowel MR protocols can be easily complemented by cine MR, extending scan time by <4 minutes.
    Journal of Magnetic Resonance Imaging 01/2012; 35(4):859-67. · 2.57 Impact Factor
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    ABSTRACT: Accurate preoperative prediction of liver function, volume, and vessel anatomy is essential in preventing postoperative liver failure, optimizing safety, and ensuring optimal outcome in patients undergoing hepatic surgery. We propose that preoperative resection planning provides useful anatomical and volumetric data, allowing for sparing of liver tissue in surgical resections. The purpose of the present study was to evaluate the use of a novel resection planning tool. Thirteen patients undergoing hemihepatectomy were included. Preoperative resection planning was performed using the commercially available software Mint Liver. During resection planning, virtual resections were calculated based on Couinaud classification, Cantlie's line (standard), and individually by the operating surgeon (individual). Intraoperatively, volume and weight of the resected specimen were measured. A 14-day follow-up was conducted, and laboratory parameters were collected. Statistical analysis was performed, comparing virtual resection volumes (i.e., standard vs. individual) and secondarily virtual vs. actual resection volume. We found a significant difference (p = 0.001) in the comparison of standard vs. individual in all 13 cases, with an average 92.8 mL smaller resected volume, sparing 11.3% of liver parenchyma with virtual resection. No patients suffered from acute liver failure. Perioperative mortality was 0%. Mint Liver is capable of acquiring exact anatomical and volumetric knowledge prior to hepatic resections. Liver parenchyma can be spared by preoperative assessment of the resection plan. We propose that this tool could be an important addition to preoperative patient evaluation, especially in complex liver surgery and living donor liver transplantation where precise volumetry is the decisive factor.
    Langenbeck s Archives of Surgery 02/2011; 396(2):201-8. · 1.89 Impact Factor
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    ABSTRACT: Although non-rigid registration methods are available or under development for many specific problems in medicine, rigid and affine registration is an important task that is often performed for pre-aligning images before using non-rigid registration. In this paper, we present a free and open-source application for rigid and affine image registration, which is designed both for developers and for end-users. The application is based on the Medical Imaging Interaction Toolkit (MITK) and allows for inter-modality and intra-modality rigid 2D-2D and 3D-3D registration of medical images such as CT, MRI, or ultrasound. The framework as well as the application can be easily extended by adding new transforms, metrics and optimizers. Thus, developers of new algorithms are enabled to test and use their algorithms more quickly, spending less work on user interfaces. Additionally, the framework provides the possibility to use image masks to restrict the evaluation of metric values by the optimizer on certain areas of the images.
    Computer methods and programs in biomedicine 10/2010; 100(1):79-86. · 1.56 Impact Factor
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    ABSTRACT: Diseases of the intestinal tract often begin with changes altering the bowel tissue elasticity. Therefore, quantification of bowel motion would be desirable for diagnosis, treatment monitoring and follow-up. Dynamic MRI can capture such changes, but quantification requires non-rigid registration. Towards a computer-assisted quantification for bowel diseases, two innovative methods for detection of bowel motility restrictions have been developed and evaluated. Therefore a coronal 2D+t image will be extracted from a dynamic 3D MRI dataset and registered non-rigidly over multiple time steps. The first method generates a new image from the resulting motion maps by adding the absolute value of the vector for each pixel to the corresponding values in following time steps. The second method calculates the absolute values only from the lateral part of the vectors, skipping the coronal part, and thus removes large distortions due to movements caused by breathing. In this preliminary evaluation both methods will be compared in regard to 5 healthy subjects (volunteers) and 5 patients with proven restrictions in bowel motility. It was shown, that for the first method with respiration a classification of volunteers and patients is only partly possible. However, the second method turns out to be capable of classifying normal and restricted bowel peristalsis. For the second method the mean motion from patients motion maps are about 34.4% lower than that from volunteers motion maps. Therefore, for the first time such a classification is possible.
    Proc SPIE 03/2010;
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    ABSTRACT: PURPOSE Quantitative analysis of bowel peristalsis to differentiate between normal peristaltic motion and conditions with impaired peristalsis like adhesions or crohn’s disease. METHOD AND MATERIALS 12 patients (median 39yrs, age range 20-71, 3m,9f) were examined in a 1.5 Tesla MRI scanner (Symphony, Siemens, Germany) by coronal trufisp cine mri (10-12 slices, 30 measurements/slice, 7-10mm slice thickness) to image bowel peristalsis after oral intake of 2 liters of water and rectal filling with 2 liters of methyl cellulose. 7 patients referred for check-up without known bowel disease served as control group. 4 patients were examined because of symptoms of chronic bowel obstruction and 1 patient for evaluation of crohn’s disease. Bowel peristalsis with exclusion of breathing motion was measured by vector based registration of the lateral shift for each pixel in the cine sequence over 30 frames and expressed by motion maps. The average of all vectors (mm) summarized served as a single value reflecting overall bowel peristalsis. RESULTS Average motion of patients without bowel disorders was 35.22 ± 6.9 mm (range 28.51-48.89); patients with chronic bowel obstruction 27.76 ± 5.1 mm (range 24.1-35.38) and the patient with crohn’s disease 26.15 mm. Patients with chronic bowel obstruction and the patient with crohn’s disease underwent surgery which confirmed diffuse adhesions and active crohn’s disease with abscess formation. Patient with normal findings were followed for one year without any signs of bowel disorders. CONCLUSION Impairment of bowel peristalsis can be measured by vector based analysis of functional cine mri using motion maps and a single average value to express overall motion. Further refinement of this technique is needed to quantify regional changes in bowel peristalsis. CLINICAL RELEVANCE/APPLICATION impairment of bowel peristalsis is not appropriately assessed by imaging so far. Quantitative vector analysis by functional imaging is an objective method to identify clinical relevant conditions.
    Radiological Society of North America 2009 Scientific Assembly and Annual Meeting; 12/2009
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    ABSTRACT: Diseases of the lung often begin with regionally limited changes altering the tissue elasticity. Therefore, quantification of regional lung tissue motion would be desirable for early diagnosis, treatment monitoring, and follow-up. Dynamic MRI can capture such changes, but quantification requires non-rigid registration. However, analysis of dynamic MRI data of the lung is challenging due to inherently low image signal and contrast. Towards a computer-assisted quantification for regional lung diseases, we have evaluated two Demons-based registration methods for their accuracy in quantifying local lung motion on dynamic MRI data. The registration methods were applied on masked image data, which were pre-segmented with a graph-cut algorithm. Evaluation was performed on five datasets from healthy humans with nine time frames each. As gold standard, manually defined points (between 8 and 24) on prominent landmarks (essentially vessel structures) were used. The distance between these points and the predicted landmark location as well as the overlap (Dice coefficient) of the segmentations transformed with the deformation field were calculated. We found that the Demons algorithm performed better than the Symmetric Forces Demons algorithm with respect to average landmark distance (6.5 mm +/- 4.1 mm vs. 8.6 mm +/- 6.1 mm), but comparable regarding the Dice coefficient (0.946 +/- 0.018 vs. 0.961 +/- 0.018). Additionally, the Demons algorithm computes the deformation in only 10 seconds, whereas the Symmetric Forces Demons algorithm takes about 12 times longer.
    Proc SPIE 02/2009;
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    ABSTRACT: In diesem Beitrag werden zwei neuartige Methoden zur Detektion von Bewegungsstörungen des Darms vorgestellt und evaluiert. Dazu werden aus dynamischen 3D MRT Datensätzen jeweils ein geeigneter koronarer 2D+t Datensatz ausgewählt und über mehrere Zeitschritte registriert. Aus den entstehenden einzelnen Bewegungskarten wird in der ersten Methode ein neues Bild generiert, das für jeden Bildpunkt alle dazugehörigen Vektorbeträge addiert. Für die zweite Methode werden die Beträge nur aus den lateralen Vektorkomponenten der Verschiebungsvektoren berechnet und somit überwiegend die Atembewegung künstlich entfernt. In einer ersten Evaluation werden für beide Methoden 5 Probanden mit 5 Patienten mit nachgewiesener eingeschränkter Darmperistaltik verglichen. Es wurde festgestellt, dass für die erste Methode mit Atmung eine Klassifizierung zwischen Probanden und Patienten nur bedingt möglich ist. Für die zweite Methode konnte jedoch gezeigt werden, dass die mittlere Bewegung in den Bewegungskarten mit Krankheitsbild ungefähr 35% geringer ist und somit erstmals eine Klassifizierung zwischen normaler und eingeschränkter Darmperistaltik ermöglicht wird.
    Bildverarbeitung für die Medizin 2009: Algorithmen - Systeme - Anwendungen, Proceedings des Workshops vom 22. bis 25. März 2009 in Heidelberg; 01/2009
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    ABSTRACT: In diesem Beitrag wird ein Open-Source-Plug-In für die Entwicklungsumgebung Eclipse vorgestellt, mit dem ein Programmablauf in Form von Zustandsmaschinen grafisch modelliert werden kann. Außerdem bietet das Konzept mit der Debug-Funktion die Möglichkeit, während der Laufzeit einer Applikation alle verwendeten Zustandsmaschinen und deren Zustandsfolgen zu beobachten. Dadurch lassen sich erstellte Zustandsmaschinen auf ihre korrekte Arbeitsweise hin überprüfen. Durch die Debug-Funktion wird das Aufspüren von Fehlern im Programmdesign deutlich vereinfacht, was gerade für die Qualitätskontrolle von medizinischen Anwendungen wichtig ist. Die erstellten Zustandsmaschinen werden beim Speichern in eine XML-Beschreibung überführt. Diese kann von anderen Applikationen direkt weiter verwendet werden.
    Bildverarbeitung für die Medizin 2008, Algorithmen, Systeme, Anwendungen, Proceedings des Workshops vom 6. bis 8. April 2008 in Berlin; 01/2008