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- Andersson, Thord, et al.
(author)
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Consistent intensity inhomogeneity correction in water-fat MRI
- 2015
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In: Journal of Magnetic Resonance Imaging. - : Wiley-Blackwell. - 1053-1807 .- 1522-2586. ; 42:2
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Journal article (peer-reviewed)abstract
- PURPOSE: To quantitatively and qualitatively evaluate the water-signal performance of the consistent intensity inhomogeneity correction (CIIC) method to correct for intensity inhomogeneitiesMETHODS: Water-fat volumes were acquired using 1.5 Tesla (T) and 3.0T symmetrically sampled 2-point Dixon three-dimensional MRI. Two datasets: (i) 10 muscle tissue regions of interest (ROIs) from 10 subjects acquired with both 1.5T and 3.0T whole-body MRI. (ii) Seven liver tissue ROIs from 36 patients imaged using 1.5T MRI at six time points after Gd-EOB-DTPA injection. The performance of CIIC was evaluated quantitatively by analyzing its impact on the dispersion and bias of the water image ROI intensities, and qualitatively using side-by-side image comparisons.RESULTS: CIIC significantly ( P1.5T≤2.3×10-4,P3.0T≤1.0×10-6) decreased the nonphysiological intensity variance while preserving the average intensity levels. The side-by-side comparisons showed improved intensity consistency ( Pint≤10-6) while not introducing artifacts ( Part=0.024) nor changed appearances ( Papp≤10-6).CONCLUSION: CIIC improves the spatiotemporal intensity consistency in regions of a homogenous tissue type.
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| 3. |
- Cros, Olivier, et al.
(author)
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Mastoid structural properties determined by imaging analysis of high resolution CT-scanning
- 2010
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In: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 263:1-2, s. 242-243
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Journal article (peer-reviewed)abstract
- Hypothesis: The structure of the mastoid air cells can be described by quantitative imaging analysis of high-resolution CT-scans, which may contribute to understand its function in normal and pathological ears. Background: Negative middle ear pressure is a common factor in middle ear diseases resulting from an imbalance between mastoid gas exchange and Eustachian tube function. While the Eustachian tube function has been the main focus of research, more recent studies indicate that the mastoid may play an active role in pressure regulation. The mastoid structure with numerous air cells reflects a large area to volume ratio (AV-ratio) adapted to efficient gas exchange. Imaging analysis applied to high resolution CT-scanning can describe quantitative measures, which may reveal important information about mastoid function and its role in healthy and diseased ears. Materials and methods: Quantitative analysis was performed on a series of unselected high resolution CT-scans (voxel size: 0.29 _ 0.29 _ 0.625 mm) from 36 ears in 24 patients. Area and volume were determined using Cavalieri’s method, i.e. by summing cross-sectional areas. The AV-ratio was computed for each scan. Results: Mean area was 69 cm2 (range: 23–134cm2), mean volume was 4 cm3 (range: 1.3–10.8 cm3), and mean AV-ratio was 16 cm-1 (range: 11.2–21.0 cm-1). The area correlated linearly to the volume by A = 17.2*V-0.2. Conclusion: The area and volume values corresponded with previous studies, and the additional AV-ratio reflected the functional properties of the mastoid in terms of capability for gas exchange. Due to a series of similarities between structure and function of the lungs and mastoid, it seems likely to propose a tree-structure of dividing mastoid cells. In respiratory research, analysis describing the dimensions of series of bronchi generations has been applied, and based on current results; our aim of future research is to establish similar details of mastoid tree-structure. Funding source: Various private Danish funds.
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| 4. |
- Dahlqvist Leinhard, Olof, et al.
(author)
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Quantification of abdominal fat accumulation during hyperalimentation using MRI
- 2009
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In: Proceedings of the ISMRM Annual Meeting (ISMRM'09), 2009. - Berkeley, CA, USA : International Society for Magnetic Resonance in Medicine. ; , s. 206-
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Conference paper (other academic/artistic)abstract
- There is an increasing demand for imaging methods that can be used for automatic, accurate and quantitative determination of the amounts of abdominal fat. Such methods are important as they will allow the evaluation of some of the risk factors underlying the ’metabolic syndrome’. The metabolic syndrome is becoming common in large parts of the world, and it appears that a dominant risk factor for developing this syndrome is abdominal obesity. Subjects that are afflicted with the metabolic syndrome are exposed to a high risk for developing a large range of diseases such as type 2 diabetes, cardiac failure, and stroke. The aim of this work
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| 6. |
- Leinhard, Olof Dahlqvist, et al.
(author)
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Quantitative Abdominal Fat Estimation Using MRI
- 2008
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In: Proceedings - International Conference on Pattern Recognition. - : IEEE Computer Society. - 9781424421749 - 9781424421756 ; , s. 1-4
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Conference paper (peer-reviewed)abstract
- This paper introduces a new method for automaticquantification of subcutaneous, visceral and nonvisceralinternal fat from MR-images acquired usingthe two point Dixon technique in the abdominal region.The method includes (1) a three dimensionalphase unwrapping to provide water and fat images, (2)an image intensity inhomogeneity correction, and (3) amorphon based registration and segmentation of thetissue. This is followed by an integration of the correctedfat images within the different fat compartmentsthat avoids the partial volume effects associated withtraditional fat segmentation methods. The method wastested on 18 subjects before and after a period of fastfoodhyper-alimentation showing high stability andperformance in all analysis steps.
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| 7. |
- Moreno, Rodrigo, 1973-, et al.
(author)
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Anisotropy Estimation of Trabecular Bone in Gray-Scale : Comparison Between Cone Beam and Micro Computed Tomography Data
- 2015
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In: Developments in Medical Image Processing and Computational Vision. - Cham : Springer. - 9783319134062 - 9783319134079 ; , s. 207-220
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Book chapter (peer-reviewed)abstract
- Measurement of anisotropy of trabecular bone has clinical relevance in osteoporosis. In this study, anisotropy measurements of 15 trabecular bone biopsies from the radius estimated by different fabric tensors on images acquired through cone beam computed tomography (CBCT) and micro computed tomography (micro-CT) were compared. The results show that the generalized mean intercept length (MIL) tensor performs better than the global gray-scale structure tensor, especially when the von Mises-Fisher kernel is applied. Also, the generalized MIL tensor yields consistent results between the two scanners. These results suggest that this tensor is appropriate for estimating anisotropy in images acquired in vivo through CBCT.
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| 8. |
- Moreno, Rodrigo, 1973-, et al.
(author)
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Correlations between fabric tensors computed on cone beam and microcomputed tomography images
- 2014
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In: Computational Vision and Medical Image Processing IV. - : CRC Press. - 9781138000810 ; , s. 393-398
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Conference paper (peer-reviewed)abstract
- Computational Vision and Medical Image Processing. VIPIMAGE 2013contains invited lectures and full papers presented at VIPIMAGE 2013 - IV ECCOMAS Thematic Conference on Computational Vision and Medical Image Processing (Funchal, Madeira Island, Portugal, 14-16 October 2013). International contributions from 16 countries provide a comprehensive coverage of the current state-of-the-art in the fields of: 3D Vision; Computational Bioimaging and Visualization; Computational Vision and Image Processing applied to Dental Medicine; Computational Vision; Computer Aided Diagnosis, Surgery, Therapy, and Treatment; Data Interpolation, Registration, Acquisition and Compression; Image Processing and Analysis; Image Segmentation; Imaging of Biological Flows; Medical Imaging; Physics of Medical Imaging; Shape Reconstruction; Signal Processing; Simulation and Modeling; Software Development for Image Processing and Analysis; Telemedicine Systems and their Applications; Trabecular Bone Characterization; Tracking and Analysis of Movement; Virtual Reality.Related techniques covered in this book include the level set method, finite element method, modal analyses, stochastic methods, principal and independent components analysis and distribution models. Computational Vision and Medical Image Processing. VIPIMAGE 2013 is useful to academics, researchers and professionals in Biomechanics, Biomedical Engineering, Computational Vision (image processing and analysis), Computer Sciences, Computational Mechanics and Medicine.
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| 9. |
- Moreno, Rodrigo, et al.
(author)
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Estimation of Trabecular Thickness in Gray-Scale Images Through Granulometric Analysis
- 2012
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In: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 9780819489630
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Conference paper (other academic/artistic)abstract
- This paper extends to gray-scale the method proposed by Hildebrand and Ru ̈egsegger for estimating thickness of trabecular bone, which is the most used in trabecular bone research, where local thickness at a point is defined as the diameter of the maximum inscribed ball that includes that point. The proposed extension takes advantage of the equivalence between this method and the opening function computed for the granulometry generated by the opening operation of mathematical morphology with ball-shaped structuring elements of different radii. The proposed extension (a) uses gray-scale instead of binary mathematical morphology, (b) uses all values of the pattern spectrum of the granulometry instead of the maximum peak as used for binary images, (c) corrects bias on local thickness estimations generated by partial volume effects, and (d) uses the gray-scale as a weighting function for global thickness estimation. The proposed extension becomes equivalent to the original method when it is applied to binary images. A new non-flat structuring element is also proposed in order to reduce the discretization errors generated by traditional flat structuring elements. Translation invariance can be attained by up-sampling the images through interpolation by a factor of two. Results for synthetic and real images show that the quality of the measurements obtained through the original method strongly depend on the binarization process, whereas the measurements obtained through the proposed extension does not. Consequently, the proposed extension is more appropriate for images with limited resolution where binarization is not trivial.
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| 10. |
- Moreno, Rodrigo, 1973-, et al.
(author)
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Evaluation of the plate-rod model assumption of trabecular bone
- 2012
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In: 9th IEEE International Symposium on Biomedical Imaging (ISBI), 2012. - : IEEE Press. - 9781457718571 ; , s. 470-473
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Conference paper (peer-reviewed)abstract
- Trabecular bone has traditionally been assumed to be composed of plate- and rod-like trabeculae. This paper proposes a method to numerically evaluate the appropriateness of this assumption. In a first step, local constancy of thickness is estimated by comparing the maximum and mean diameter of the maximum inscribed balls centered at the medial axis/surface that includes every local point. In a second step, deviations from null curvature at the medial axis/surface are locally measured by comparing the geodesic and Euclidean distances from a point to its neighbors in the medial axis/surface. Finally, these two measurements are combined in order to locally estimate the compliance of the dataset with the plate-rod model assumption. Experiments on synthetic datasets show that the proposed measurements can be used to decide the compliance of a 3D shape with the plate-rod model. Results on micro computed tomography images show that the plate-rod model is more valid for a vertebra than for a radius. Thus, especially for the radius, measurements based on this model should be complemented with the proposed measurements.
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