| 1. |
- Firouznia, Marjan, et al.
(författare)
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Dataset and code for "FK-means: Automatic Atrial Fibrosis Segmentation using Fractal-guided K-means Clustering with Voronoi-Clipping Feature Extraction of Anatomical Structures" : FKmeans for fibrosis segmentation
- 2023
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Annan publikationabstract
- Assessment of left atrial (LA) fibrosis from late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) adds to the management of patients with atrial fibrillation (AF). However, accurate assessment of fibrosis in the LA wall remains challenging. Excluding anatomical structures in the LA proximity using clipping techniques can reduce misclassification of LA fibrosis. A novel FK-means approach for combined automatic clipping and automatic fibrosis segmentation was developed. This approach combines a feature-based Voronoi diagram with a hierarchical 3D K-means fractal-based method. The proposed automatic Voronoi clipping method was applied on LGE MRI data and achieved a Dice score of 0.75, similar as the score obtained by a deep learning method (3D UNet) for clipping (0.74). The automatic fibrosis segmentation method, which utilizes the Voronoi clipping method, achieved a Dice score of 0.76. This outperformed a 3D U-Net method for clipping and fibrosis classification, which had a Dice score of 0.69. Moreover, the proposed automatic fibrosis segmentation method achieved a Dice score of 0.90, using manual clipping of anatomical structures. The findings suggest that the automatic FK-means analysis approach enables reliable LA fibrosis segmentation and that clipping of anatomical structures in the atrial proximity can add to the assessment of atrial fibrosis.
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| 2. |
- Firouznia, Marjan, et al.
(författare)
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FK-means: automatic atrial fibrosis segmentation using fractal-guided K-means clustering with Voronoi-clipping feature extraction of anatomical structures
- 2023
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Ingår i: Interface Focus. - : ROYAL SOC. - 2042-8898 .- 2042-8901. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- Assessment of left atrial (LA) fibrosis from late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) adds to the management of patients with atrial fibrillation. However, accurate assessment of fibrosis in the LA wall remains challenging. Excluding anatomical structures in the LA proximity using clipping techniques can reduce misclassification of LA fibrosis. A novel FK-means approach for combined automatic clipping and automatic fibrosis segmentation was developed. This approach combines a feature-based Voronoi diagram with a hierarchical 3D K-means fractal-based method. The proposed automatic Voronoi clipping method was applied on LGE-MRI data and achieved a Dice score of 0.75, similar to the score obtained by a deep learning method (3D UNet) for clipping (0.74). The automatic fibrosis segmentation method, which uses the Voronoi clipping method, achieved a Dice score of 0.76. This outperformed a 3D UNet method for clipping and fibrosis classification, which had a Dice score of 0.69. Moreover, the proposed automatic fibrosis segmentation method achieved a Dice score of 0.90, using manual clipping of anatomical structures. The findings suggest that the automatic FK-means analysis approach enables reliable LA fibrosis segmentation and that clipping of anatomical structures in the atrial proximity can add to the assessment of atrial fibrosis.
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| 3. |
- Forte, Mari Nieves Velasco, et al.
(författare)
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Visualization of coronary arteries in paediatric patients using whole-heart coronary magnetic resonance angiography: comparison of image-navigation and the standard approach for respiratory motion compensation
- 2019
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - : BMC. - 1097-6647 .- 1532-429X. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- AimsTo investigate the use of respiratory motion compensation using image-based navigation (iNAV) with constant respiratory efficiency using single end-expiratory thresholding (CRUISE) for coronary magnetic resonance angiography (CMRA), and compare it to the conventional diaphragmatic navigator (dNAV) in paediatric patients with congenital or suspected heart disease.MethodsiNAV allowed direct tracking of the respiratory heart motion and was generated using balanced steady state free precession startup echoes. Respiratory gating was achieved using CRUISE with a fixed 50% efficiency. Whole-heart CMRA was acquired with 1.3mm isotropic resolution. For comparison, CMRA with identical imaging parameters were acquired using dNAV. Scan time, visualization of coronary artery origins and mid-course, imaging quality and sharpness was compared between the two sequences.ResultsForty patients (13 females; median weight: 44kg; median age: 12.6, range: 3months-17years) were enrolled. 25 scans were performed in awake patients. A contrast agent was used in 22 patients. The scan time was significantly reduced using iNAV for awake patients (iNAV 7:481:26 vs dNAV 9:48 +/- 3:11, P=0.01) but not for patients under general anaesthesia (iNAV=6:55 +/- 1:50 versus dNAV=6:32 +/- 2:16; P=0.32). In 98% of the cases, iNAV image quality had an equal or higher score than dNAV. The visual score analysis showed a clear difference, favouring iNAV (P=0.002). The right coronary artery and the left anterior descending vessel sharpness was significantly improved (iNAV: 56.8%+/- 10.1% vs dNAV: 53.7%+/- 9.9%, Pamp;lt;0.002 and iNAV: 55.8%+/- 8.6% vs dNAV: 53%+/- 9.2%, P=0.001, respectively).Conclusion p id=Par4 iNAV allows for a higher success-rate and clearer depiction of the mid-course of coronary arteries in paediatric patients. Its acquisition time is shorter in awake patients and image quality score is equal or superior to the conventional method in most cases.
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| 4. |
- Gomez, Alberto, et al.
(författare)
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Mechanically Powered Motion Imaging Phantoms: Proof of Concept
- 2019
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Ingår i: 2019 41ST ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC). - : IEEE. - 9781538613115 - 9781538613122 ; , s. 2723-2726
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Konferensbidrag (refereegranskat)abstract
- Motion imaging phantoms are expensive, bulky and difficult to transport and set-up. The purpose of this paper is to demonstrate a simple approach to the design of multi-modality motion imaging phantoms that use mechanically stored energy to produce motion. We propose two phantom designs that use mainsprings and elastic bands to store energy. A rectangular piece was attached to an axle at the end of the transmission chain of each phantom, and underwent a rotary motion upon release of the mechanical motor. The phantoms were imaged with MRI and US, and the image sequences were embedded in a 1D non linear manifold (Laplacian Eigenmap) and the spectrogram of the embedding was used to derive the angular velocity over time. The derived velocities were consistent and reproducible within a small error. The proposed motion phantom concept showed great potential for the construction of simple and affordable motion phantoms.
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| 5. |
- Henningsson, Markus, et al.
(författare)
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Black-Blood Contrast in Cardiovascular MRI
- 2022
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Ingår i: Journal of Magnetic Resonance Imaging. - : WILEY. - 1053-1807 .- 1522-2586. ; 55:1, s. 61-80
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Forskningsöversikt (refereegranskat)abstract
- MRI is a versatile technique that offers many different options for tissue contrast, including suppressing the blood signal, so-called black-blood contrast. This contrast mechanism is extremely useful to visualize the vessel wall with high conspicuity or for characterization of tissue adjacent to the blood pool. In this review we cover the physics of black-blood contrast and different techniques to achieve blood suppression, from methods intrinsic to the imaging readout to magnetization preparation pulses that can be combined with arbitrary readouts, including flow-dependent and flow-independent techniques. We emphasize the technical challenges of black-blood contrast that can depend on flow and motion conditions, additional contrast weighting mechanisms (T-1, T-2, etc.), magnetic properties of the tissue, and spatial coverage. Finally, we describe specific implementations of black-blood contrast for different vascular beds. Level of Evidence 5 Technical Efficacy Stage 5
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| 6. |
- Henningsson, Markus, 1982-
(författare)
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Cartesian dictionary-based native T-1 and T-2 mapping of the myocardium
- 2022
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 87:5, s. 2347-2362
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Tidskriftsartikel (refereegranskat)abstract
- Purpose To implement and evaluate a new dictionary-based technique for native myocardial T-1 and T-2 mapping using Cartesian sampling. Methods The proposed technique (Multimapping) consisted of single-shot Cartesian image acquisitions in 10 consecutive cardiac cycles, with inversion pulses in cycle 1 and 5, and T-2 preparation (TE: 30 ms, 50 ms, and 70 ms) in cycles 8-10. Multimapping was simulated for different T-1 and T-2, where entries corresponding to the k-space centers were matched to acquired data. Experiments were performed in a phantom, 16 healthy subjects, and 3 patients with cardiovascular disease. Results Multimapping phantom measurements showed good agreement with reference values for both T-1 and T-2, with no discernable heart-rate dependency for T-1 and T-2 within the range of myocardium. In vivo mean T-1 in healthy subjects was significantly higher using Multimapping (T-1 = 1114 +/- 14 ms) compared to the reference (T-1 = 991 +/- 26 ms) (p < 0.01). Mean Multimapping T-2 (47.1 +/- 1.3 ms) and T-2 spatial variability (5.8 +/- 1.0 ms) was significantly lower compared to the reference (T-2 = 54.7 +/- 2.2 ms, p < 0.001; spatial variability = 8.4 +/- 2.0 ms, p < 0.01). Increased T-1 and T-2 was detected in all patients using Multimapping. Conclusions Multimapping allows for simultaneous native myocardial T-1 and T-2 mapping with a conventional Cartesian trajectory, demonstrating promising in vivo image quality and parameter quantification results.
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| 7. |
- Henningsson, Markus, et al.
(författare)
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DIY-handeln i UK - en branschstudie
- 2009. - 01
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Ingår i: Affärsutveckling inom trämanufaktur och möbler - Hur skapas effektivare värdekedjor?. - Stockholm : Vinnova. - 9789185959396 ; , s. 143-158
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Den engelska marknaden för DIY (Do It Yourself) ligger långt framme i sin utveckling. Marknaden på detaljistsidan har under den senaste tioårsperioden konsoliderats till fyra huvudkedjor och dessa kedjor har utvidgat sitt sortiment till att omfatta allt flera produktkategorier, med fokus på flera s k mjuka produkter som tapeter, möbler och även vitvaror. Detaljistkedjornas inköpsstrategier har utvecklats mot att kraftigt minska antalet leverantörer per produktkategori och kategorin sågade trävaror är inget undantag. Trävaror räknas in som en av ”the ugglies”, dvs produkter av bulkkaraktär som har en låg marginal. Detta får som följd att detaljistkedjorna kräver att leverantören själv ska ta hand om logistiken, vilket är en av de vikigaste utgångspunkterna för att komma till fråga som ledare för en av produktkategorierna. Andra krav som står högt på prioriteringslistan är produktutveckling där konsumentens behov är står i centrum. Sammantaget, vill de engelska detaljisterna ge sina konsumenter ett brett sortiment för ”one stop shopping”, vilket gör dem beroende av starka leverantörer som tar egna initiativ och ansvar för sina produktkategorier. Leverantörerna av sågade trävaror ska ytterst bidra till att detaljistkedjorna tjänar pengar och är lönsamma.
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| 8. |
- Henningsson, Markus, et al.
(författare)
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Inflow artifact reduction using an adaptive flip-angle navigator restore pulse for late gadolinium enhancement of the left atrium
- 2020
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Ingår i: Magnetic Resonance in Medicine. - : WILEY. - 0740-3194 .- 1522-2594. ; 84:6, s. 3308-3315
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Late gadolinium enhancement (LGE) of the left atrium is susceptible to artifacts arising from the right pulmonary veins, caused by inflowing blood tagged by the navigator restore pulse. The purpose of this study was to evaluate a new method to reduce the inflow artifact using an adaptive flip-angle restore pulse. Methods A low-restore angle reduces the inflow artifact but may lead to a poor navigator SNR. The proposed approach aims to determine the patient-specific restore angle, which optimizes the trade-off between inflow artifacts and navigator SNR. Three-dimensional LGE with adaptive navigator restore (3D LGE(A)) was implemented by incrementing the flip angle of the restore pulse from a starting value of 0 degrees, based on the navigator normalized cross-correlation. Magnetic resonance imaging experiments were performed on a 1.5T scanner. The value of 3D LGE(A) was compared with 3D LGE with a constant 180 degrees restore pulse (3D LGE(180)) in 22 patients with heart diseases. The values of 3D LGE(A) and 3D LGE(180) were compared in terms of pulmonary vein blood signal relative to reference blood in the descending aorta (PVrel) and visual scoring to determine level of motion artifacts using a 4-point scale (1 = severe artifacts; 4 = no artifacts). Results The value of PVrel was significantly lower for 3D LGE(A) than for 3D LGE(180) (1.16 +/- 0.23 vs. 1.59 +/- 0.29, P < .001). Furthermore, visual scoring of the motion artifacts yielded no difference (P = .78). Conclusion Adaptively adjusting the navigator restore flip angle based on the navigator normalized cross-correlation reduces the 3D LGE inflow artifact without affecting image quality or the scan time.
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| 9. |
- Henningsson, Markus, et al.
(författare)
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Myocardial arterial spin labeling in systole and diastole using flow-sensitive alternating inversion recovery with parallel imaging and compressed sensing
- 2021
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Ingår i: NMR in Biomedicine. - : WILEY. - 0952-3480 .- 1099-1492. ; 34:2
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative myocardial perfusion can be achieved without contrast agents using flow-sensitive alternating inversion recovery (FAIR) arterial spin labeling. However, FAIR has an intrinsically low sensitivity, which may be improved by mitigating the effects of physiological noise or by increasing the area of artifact-free myocardium. The aim of this study was to investigate if systolic FAIR may increase the amount of analyzable myocardium compared with diastolic FAIR and its effect on physiological noise. Furthermore, we compare parallel imaging acceleration with a factor of 2 with compressed sensing acceleration with a factor of 3 for systolic FAIR. Twelve healthy subjects were scanned during rest on a 3 T scanner using diastolic FAIR with parallel imaging factor 2 (FAIR-PI2(D)), systolic FAIR with the same acceleration (FAIR-PI2(S)) and systolic FAIR with compressed sensing factor 3 (FAIR-CS3(S)). The number of analyzable pixels in the myocardium, temporal signal-to-noise ratio (TSNR) and mean myocardial blood flow (MBF) were calculated for all methods. The number of analyzable pixels using FAIR-CS3(S) (663 +/- 55) and FAIR-PI2(S) (671 +/- 58) was significantly higher than for FAIR-PI2(D) (507 +/- 82; P = .001 for both), while there was no significant difference between FAIR-PI2(S) and FAIR-CS3(S). The mean TSNR of the midventricular slice for FAIR-PI2(D) was 11.4 +/- 3.9, similar to that of FAIR-CS3(S,) which was 11.0 +/- 3.3, both considerably higher than for FAIR-PI2(S,) which was 8.4 +/- 3.1 (P < .05 for both). Mean MBF was similar for all three methods. The use of compressed sensing accelerated systolic FAIR benefits from an increased number of analyzable myocardial pixels compared with diastolic FAIR without suffering from a TSNR penalty, unlike systolic FAIR with parallel imaging acceleration.
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| 10. |
- Henningsson, Markus, et al.
(författare)
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Non-contrast myocardial perfusion in rest and exercise stress using systolic flow-sensitive alternating inversion recovery
- 2022
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer. - 0968-5243 .- 1352-8661. ; 35:5, s. 711-718
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Tidskriftsartikel (refereegranskat)abstract
- Objective To evaluate systolic flow-sensitive alternating inversion recovery (FAIR) during rest and exercise stress using 2RR (two cardiac cycles) or 1RR intervals between inversion pulse and imaging. Materials and methods 1RR and 2RR FAIR was implemented on a 3T scanner. Ten healthy subjects were scanned during rest and stress. Stress was performed using an in-bore ergometer. Heart rate, mean myocardial blood flow (MBF) and temporal signal-to-noise ratio (TSNR) were compared using paired t tests. Results Mean heart rate during stress was higher than rest for 1RR FAIR (85.8 +/- 13.7 bpm vs 63.3 +/- 11.1 bpm; p < 0.01) and 2RR FAIR (83.8 +/- 14.2 bpm vs 63.1 +/- 10.6 bpm; p < 0.01). Mean stress MBF was higher than rest for 1RR FAIR (2.97 +/- 0.76 ml/g/min vs 1.43 +/- 0.6 ml/g/min; p < 0.01) and 2RR FAIR (2.8 +/- 0.96 ml/g/min vs 1.22 +/- 0.59 ml/g/min; p < 0.01). Resting mean MBF was higher for 1RR FAIR than 2RR FAIR (p < 0.05), but not during stress. TSNR was lower for stress compared to rest for 1RR FAIR (4.52 +/- 2.54 vs 10.12 +/- 3.69; p < 0.01) and 2RR FAIR (7.36 +/- 3.78 vs 12.41 +/- 5.12; p < 0.01). 2RR FAIR TSNR was higher than 1RR FAIR for rest (p < 0.05) and stress (p < 0.001). Discussion We have demonstrated feasibility of systolic FAIR in rest and exercise stress. 2RR delay systolic FAIR enables non-contrast perfusion assessment during stress with relatively high TSNR.
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