StentDeform: Motion and deformation of aortic aneurysm stent grafts
Julian Mattes
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The enlargement of the aorta due to weakened walls of the aorta is called an aortic aneurysm [1]. If their diameter gets to large aortic aneurysm should be treated because of the perilous risk of rupture. A treatment established in the early nineties is the endovascular aneurysm repair in which a stent with a synthetic graft (stent graft) is placed inside the aorta. The advantage of this treatment compared to an open repair is a reduced exposure of the patient during and after the surgical intervention [2]. On the other hand, the process of aneurysm shrinkage, ongoing aneurismal disease, and damage or fatigue of graft material may result in leakage, graft migration, and kinking or buckling of the graft, which can subsequently cause rupture or occlusion [3]. Currently, few is known neither about these morphological changes and the migration of the graft nor about those of the aneurysm after an endovascular stent graft implantation, in particular their quantitative description is lacking. Such a description would help to detect week points of the stent graft, to better understand the mechanisms leading to dangerous changes in its morphology and their relation to the kind of graft used (and of its material). Moreover, it would hopefully suggest strategies to prevent the occurrence of dangerous morphological changes and yield an early indicator for the risk of their occurrence [4,5,6].

In this project we set up an image processing and spatial data analysis pipeline in order to quantify and to visualize the movements and deformations occurring in three dimensional CT image stacks of the abdominal aorta with aneurysm and stent acquired at different time points, usually separated by an interval of several months (see Figure 1). Here, we use image segmentation techniques implemented in the ITK library [7,8] and we use point set registration techniques [9,10,11] in order to determine parameters describing the occurring movements and deformations as well as the residual shape differences.

Publications

Julian Mattes, Iris Steingruber, Michael Netzer, Karl Fritscher, Helmut Kopf, Werner Jaschke, Rainer Schubert.

Spatio-temporal changes and migration of stent grafts after endovascular aortic aneurysm repair. CARS 2005 (in press)

References

[1] Cronenwett, J.L. et al. Abdominal aortic and iliac aneurysms. In R.B.Rutherford (Ed.),. Vascular Surgery, Saunders, 2000, 1246-1280
[2] Rutherford, R.B. and Krupski, W.C. Current status of open versus endovascular stent-graft repair of abdominal aortic aneurysm. J. Vasc. Surg. 39 (5), 2004
[3] Fillinger, M. Postoperative imaging after endovascular AAA repair. Seminars in Vas. Surg. 12.(4),1999, 327-338
[4] Czermak, B., Fraedrich, G., Schocke, M., Steingruber, I., Waldenberger, P., Perkmann, R., Rieger, M. Jaschke, W. Serial CT volume measurements after endovascular aortic aneurysm repair. J Endovas. Ther. (4) 2001, 380-389
[5] M. de Bruijne et al. Interactive segmentation of abdominal aortic aneurysms in CTA images. Med. Image Anal. (8) 2004, 127-138
[6] M. Breeuwer et al. Assessment of the rupture risk of AAAs by patient-specific hemodynamic
modelling – initial results CARS 2004, 1090-1095
[7] http://www.itk.org/index.htm
[8] Fritscher, K. , R. Schubert. A software framework for preprocessing and level-set segmentation
of medical image data. In: SPIE Medical Imaging 2005: Image Processing (in press)
[9] Lavallée, S., Szeliski, R.: Recovering the position and orientation of free-form objects from
image contours using 3D distance maps. IEEE Trans. Pat. Anal. Mach. Int. 17 (1995) 378-390
[10] J. Mattes et al.. Quantitative Analyse, Visualisierung und Bewegungskorrektur in dynamischen
Prozessen, 2001, (German Patent Pending 101 11 226.2, 101 44 629.2, PCT Patent Application)
[11] J. Mattes et al. A shape adapted motion model for non-rigid registration. In: SPIE Medical
Imaging 2002: Image Processing, 2002, 518-527
   

Partners: Iris Steingruber, Helmut Kopf, Werner Jaschke, Department of Diagnostic Radiology, Innsbruck Medical University

State: Ongoing, BSc thesis: Michael Netzer, Segmentierung von Stent, Aorta und Spinalkanal zur Analyse ihrer relativen Bewegung nach endovaskulärer Behandlung abdominaler Aneurysmen


(a)

(b)

(c)


Quantum Stent for an abdominal aortic aneurysm at two different time points (11 months difference) after rigid superimposition, viewed laterally (a), from the bottom (b), and from ahead (c);

 

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