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- Floreby, Lars
(författare)
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Image Analysis and Enhancement with Applications in Medicine
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of six parts in which methods for image analysis and processing are studied. Two-dimensional medical images, image sequences, and three-dimensional image volumes are considered. In the first part, the concept of optical flows (OF) is employed for restoring the contracting/expanding ventricle motion in ultrasonic echocardiograms. Radial velocities obtained by a scalar approach are summed up to time series representing the motion in different sectors of a circular region in the image. In part two, dynamic programming (DP) is used for matching closed deformable contours to the inner boundary of an annular-shaped, bright object in simulated speckle images. Adjustment of method parameters, scale and resolution aspects, search strategies, and spatio-temporal behavior is considered. Application examples consisting of echocardiographic sequences are also given. Part three presents an image enhancement method based on lowpass pyramid decomposition and modified reconstruction. By retaining only the pixels corresponding to detected edges at each reconstruction stage, edge-preserving noise suppression can be obtained. The method is applied to simulated speckle images, to an ultrasonic image from phantom measurements, and to an echocardiographic image. In part four, the algorithm from part three is reformulated to use morphological operations for smoothing before downsampling, reconstruction, and edge detection. Enhancement of speckle image is evaluated. Part five is concerned with the registration of abdominal slices from CT and SPECT using Compton scatter images as a basis for determination of the patient boundary. Contour estimation is performed by interactive thresholding and an automatic deformable boundary technique. In part six, closed boundary finding in medical 3-D image sets is carried out by optimizing Fourier surfaces of gradually increasing order. Algorithmic performance is evaluated for simulated images based on the anthropomorphic Zubal phantom, and various noise levels. Application examples are given for SPECT images acquired from Monte Carlo simulatations and patient measurements.
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| 2. |
- Sattar, Farook, et al.
(författare)
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Image Enhancement based on a Nonlinear Multiscale Method
- 1997
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Ingår i: IEEE Transactions on Image Processing. - New York : IEEE. - 1057-7149 .- 1941-0042. ; 6:6, s. 888-895
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Tidskriftsartikel (refereegranskat)abstract
- An image enhancement method that reduces speckle noise and preserves edges is introduced. The method is based on a new nonlinear multiscale reconstruction scheme that is obtained by successively combining each coarser scale image with the corresponding modified interscale image. Simulation results are included to demonstrate the performance of the proposed method.
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| 3. |
- Sjögreen Gleisner, Katarina, et al.
(författare)
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Registration of abdominal CT and SPECT images using Compton scatter data
- 1997
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Ingår i: Information Processing in Medical Imaging. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540630463 ; 1230, s. 232-244
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Bokkapitel (refereegranskat)abstract
- The present study investigates the possibility to utilize Compton scatter data for registration of abdominal SPECT images. A method for registration to CT is presented, based on principal component analysis and cross-correlation of binary images representing the interior of the patient. Segmentation of scatter images is performed with two methods, thresholding and a deformable contour method. To achieve similarity of organ positions between scans, a positioning device is applied to the patient. Evaluation of the registration accuracy is performed with a) a 131I phantom study, b) a Monte Carlo simulation study of an anthropomorphic phantom, and c) a 123I patient trial. For a) r.m.s. distances between positions that should be equal in CT and SPECT are obtained to 1.0±0.7 mm, which thus for a rigid object is at sub pixel level. From b) results show that r.m.s. distances depend on the slice activity distribution. With a symmetrical distribution deviations are in the order of 5 mm. In c) distances between markers on the patient boundary are at the maximum 16 mm and on an average 10 mm. It is concluded that by utilizing the available Compton scatter data, valuable positioning information is achieved, that can be used for registration of SPECT images.
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