| 11. |
|
|
| 12. |
- Läthén, Gunnar, et al.
(författare)
-
Momentum Based Optimization Methods for Level Set Segmentation
- 2009
-
Ingår i: Momentum Based Optimization Methods for Level Set Segmentation. - Berlin : Springer Berlin/Heidelberg. - 3642022553 - 9783642022555 - 9783642022562 ; , s. 124-136
-
Konferensbidrag (refereegranskat)abstract
- Segmentation of images is often posed as a variational problem. As such, it is solved by formulating an energy functional depending on a contour and other image derived terms. The solution of the segmentation problem is the contour which extremizes this functional. The standard way of solving this optimization problem is by gradient descent search in the solution space, which typically suffers from many unwanted local optima and poor convergence. Classically, these problems have been circumvented by modifying the energy functional. In contrast, the focus of this paper is on alternative methods for optimization. Inspired by ideas from the machine learning community, we propose segmentation based on gradient descent with momentum. Our results show that typical models hampered by local optima solutions can be further improved by this approach. We illustrate the performance improvements using the level set framework.
|
|
| 13. |
- Läthén, Gunnar, et al.
(författare)
-
Phase Based Level Set Segmentation of Blood Vessels
- 2008
-
Ingår i: Proceedings of 19th International Conference on Pattern Recognition. - : IEEE Computer Society. - 9781424421756 - 9781424421749 ; , s. 1-4
-
Konferensbidrag (refereegranskat)abstract
- The segmentation and analysis of blood vessels hasreceived much attention in the research community. Theresults aid numerous applications for diagnosis andtreatment of vascular diseases. Here we use level setpropagation with local phase information to capture theboundaries of vessels. The basic notion is that localphase, extracted using quadrature filters, allows us todistinguish between lines and edges in an image. Notingthat vessels appear either as lines or edge pairs, weintegrate multiple scales and capture information aboutvessels of varying width. The outcome is a “global”phase which can be used to drive a contour robustly towardsthe vessel edges. We show promising results in2D and 3D. Comparison with a related method givessimilar or even better results and at a computationalcost several orders of magnitude less. Even with verysparse initializations, our method captures a large portionof the vessel tree.
|
|
| 14. |
- Pettersson, Johanna, 1977-, et al.
(författare)
-
A hip surgery simulator based on patient specific models generated by automatic segmentation
- 2006
-
Ingår i: Medicine Meets Virtual Reality 14: Accelerating Change in Healthcare. - Amsterdam, Nederländerna : IOS Press. - 9781586035839 ; , s. 431-436
-
Konferensbidrag (refereegranskat)abstract
- The use of surgical simulator systems for education and preoperative planning is likely to increase in the future. A natural course of development of these systems is to incorporate patient specific anatomical models. This step requires some kind of segmentation process in which the different anatomical parts are extracted. Anatomical datasets are, however, usually very large and manual processing would be too demanding. Hence, automatic, or semi-automatic, methods to handle this step are required. The framework presented in this paper uses nonrigid registration, based on the morphon method, to automatically segment the hip anatomy and generate models for a hip surgery simulator system.
|
|
| 15. |
- Pettersson, Johanna, 1977-, et al.
(författare)
-
Automatic hip bone segmentation using non-rigid registration
- 2006
-
Ingår i: 18th International Conference on Pattern Recognition, 2006, ICPR 2006 (Volume:3 ). - : IEEE Computer Society. - 0769525210 ; , s. 946-949
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a method for automatic segmentation of bone from volumetric computed tomography (CT) data. Due to osteoporosis, which degenerates the bone density and hence decreases the intensity of the bone in the CT dataset, it is not possible to use conventional thresholding techniques to handle the segmentation. Furthermore we want to use prior knowledge about shapes and relations of the bones in the area of interest to be able to e.g. separate adjoining bones from each other. The method we suggest is the morphon algorithm in Knutsson and Andersson (2005). This is a non-rigid registration technique where an 2D or 3D image is iteratively deformed to match the corresponding structure in a target image. The method uses difference in local quadrature phase and certainty measures to estimate the deformations
|
|
| 16. |
- Pettersson, Johanna, 1977-, et al.
(författare)
-
Generation of patient specific bone models from volume data using morphons
- 2005
-
Ingår i: IFMBE Proceedings. - Umeå : IFMBE. ; , s. 199-200
-
Konferensbidrag (refereegranskat)abstract
- The use of simulator systems for surgical planning and training is growing as the systems become more advanced. One important feature of these systems is the possibility to work on real patient data. This paper presents a method for generating patient-specific models of the femoral bone and the pelvis to be used in a hip surgery simulator. The bones are segmented from volumetric CT data using the Morphon method [3], where a prototype pattern is iteratively morphed to fit the corresponding structure in the input data.
|
|
| 17. |
- Pettersson, Johanna, 1977-, et al.
(författare)
-
Non-rigid registration for automatic fracture segmentation
- 2006
-
Ingår i: Image Processing, 2006. - Atlanta : IEEE. - 1424404800 ; , s. 1185-1188
-
Konferensbidrag (refereegranskat)abstract
- Automatic segmentation of anatomical structures is often performed using model-based non-rigid registration methods. These algorithms work well when the images do not contain any large deviations from the normal anatomy. We have previously used such a method to generate patient specific models of hip bones for surgery simulation. The method that was used, the morphon method, registers two-or three-dimensional images using a multi-resolution deformation scheme. A prototype image is iteratively registered to a target image using quadrature filter phase difference to estimate the local displacement. The morphon method has in this work been extended to deal with automatic segmentation of fractured bones. Two features have been added. First, the method is modified such that multiple prototypes (in this case two) can be used. Second, normalised convolution is utilized for the displacement estimation, to guide the registration of the second prototype, based on the result of the registration of the first one
|
|
| 18. |
|
|
| 19. |
- Pettersson, Johanna, 1977-, et al.
(författare)
-
Segmentation and registration with the Morphon method, four different applications
- 2007
-
Ingår i: Proceedings of the {SSBA} Symposium on Image Analysis,2007.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Morphon method has shown to be a useful non-rigid registration method since it was first presented in 2005. This paper demonstrates how the method has been adapted for four different applications; hip fracture segmentation from CT data, hippocampus segmentation from MR data and registration the prostate and the head-neck region from CT data for radiotherapy planning.
|
|
| 20. |
- Pettersson, Johanna, et al.
(författare)
-
Simulation of Patient Specific Cervical Hip Fracture Surgery With a Volume Haptic Interface
- 2008
-
Ingår i: IEEE Transactions on Biomedical Engineering. - : IEEE. - 0018-9294 .- 1558-2531. ; 55:4, s. 1255-1265
-
Tidskriftsartikel (refereegranskat)abstract
- The interest for surgery simulator systems with anatomical models generated from authentic patient data is growing as these systems evolve.With access to volumetric patient data, e.g., from a computer tomography scan, haptic and visual feedback can be created directly from this dataset. This opens the door for patient specific simulations. Hip fracture surgery is one area where simulator systems is useful to train new surgeons and plan operations. To simulate the drilling procedure in this type of surgery, a repositioning of the fractured bone into correct position is first needed. This requires a segmentation process in which the bone segments are identified and the position of the dislocated part is determined. The segmentation must be automatic to cope with the large amount of data from the computer tomography scan. This work presents the first steps in the development of a hip fracture surgery simulation with patient specific models. Visual and haptic feedback is generated from the computer tomography data by simulating fluoroscopic images and the drilling process. We also present an automatic segmentation method to identify the fractured bone and determine the dislocation. This segmentation method is based on nonrigid registration with the Morphon method.
|
|
