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- Dunås, Tora, et al.
(författare)
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Automatic labeling of cerebral arteries in magnetic resonance angiography
- 2016
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 29:1, s. 39-47
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Tidskriftsartikel (refereegranskat)abstract
- In order to introduce 4D flow magnetic resonance imaging (MRI) as a standard clinical instrument for studying the cerebrovascular system, new and faster postprocessing tools are necessary. The objective of this study was to construct and evaluate a method for automatic identification of individual cerebral arteries in a 4D flow MRI angiogram. Forty-six elderly individuals were investigated with 4D flow MRI. Fourteen main cerebral arteries were manually labeled and used to create a probabilistic atlas. An automatic atlas-based artery identification method (AAIM) was developed based on vascular-branch extraction and the atlas was used for identification. The method was evaluated by comparing automatic with manual identification in 4D flow MRI angiograms from 67 additional elderly individuals. Overall accuracy was 93 %, and internal carotid artery and middle cerebral artery labeling was 100 % accurate. Smaller and more distal arteries had lower accuracy; for posterior communicating arteries and vertebral arteries, accuracy was 70 and 89 %, respectively. The AAIM enabled fast and fully automatic labeling of the main cerebral arteries. AAIM functionality provides the basis for creating an automatic and powerful method to analyze arterial cerebral blood flow in clinical routine.
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- Helms, Gunther
(författare)
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Segmentation of human brain using structural MRI
- 2016
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 29:2
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Forskningsöversikt (refereegranskat)abstract
- Segmentation of human brain using structural MRI is a key step of processing in imaging neuroscience. The methods have undergone a rapid development in the past two decades and are now widely available. This non-technical review aims at providing an overview and basic understanding of the most common software. Starting with the basis of structural MRI contrast in brain and imaging protocols, the concepts of voxel-based and surface-based segmentation are discussed. Special emphasis is given to the typical contrast features and morphological constraints of cortical and sub-cortical grey matter. Besides the use for voxel-based morphometry, basic applications in quantitative MRI, cortical thickness estimations, and atrophy measurements as well as assignment of cortical regions and deep brain nuclei are briefly discussed. Finally, some fields for clinical applications are given.
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- Holst, Karen, et al.
(författare)
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Projection-based respiratory-resolved left ventricular volume measurements in patients using free-breathing double golden-angle 3D radial acquisition.
- 2019
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 32:3, s. 331-341
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Tidskriftsartikel (refereegranskat)abstract
- To refine a new technique to measure respiratory-resolved left ventricular end-diastolic volume (LVEDV) in mid-inspiration and mid-expiration using a respiratory self-gating technique and demonstrate clinical feasibility in patients.Ten consecutive patients were imaged at 1.5T during 10min of free breathing using a 3D golden-angle radial trajectory. Two respiratory self-gating signals were extracted and compared: from the k-space center of all acquired spokes, and from a superior-inferior projection spoke repeated every 64ms. Data were binned into end-diastole and two respiratory phases of 15% respiratory cycle duration in mid-inspiration and mid-expiration. LVED volume and septal-lateral diameter were measured from manual segmentation of the endocardial border.Respiratory-induced variation in LVED size expressed as mid-inspiration relative to mid-expiration was, for volume, 1±8% with k-space-based self-gating and 8±2% with projection-based self-gating (P=0.04), and for septal-lateral diameter, 2±2% with k-space-based self-gating and 10±1% with projection-based self-gating (P=0.002).Measuring respiratory variation in LVED size was possible in clinical patients with projection-based respiratory self-gating, and the measured respiratory variation was consistent with previous studies on healthy volunteers. Projection-based self-gating detected a higher variation in LVED volume and diameter during respiration, compared to k-space-based self-gating.
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IVIM reveals increased blood perfusion of liver metastases after oral intake of Salovum®
- 2015
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661.
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Proceedings (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Introduction Elevated interstitial fluid pressure (IFP) of tumours impairs perfusion, which hinders anti-cancer drugs and oxygen to reach tumour cells1-3. AF-16, a 16 amino acid long sequence from the amino terminal end of the endogenous protein Antisecretory Factor (AF), supresses IFP in animal models of solid tumours4, and could improve drug delivery to tumour cells. Salovum®, a spray-dried egg yolk powder with high content of antisecretory peptides, should be tested on humans, but requires non-invasive tumour IFP/perfusion assessment methods. The IntraVoxel Incoherent Motion (IVIM) model applied to multi-b DWI enables measurement of tissue diffusion (D), pseudo-diffusion (D*) and voxel volume fraction of actively perfused capillaries (f) 5. The aim of this study was to investigate if f could be used to monitor changes induced by Salovum® in colorectal liver metastases in vivo Subjects and Methods Previously untreated patients (n=6) with colorectal liver metastases were imaged before, and 24h after intake of Salovum®, using IVIM-MRI (3T Philips, 16‐channel receiver; Single-shot, SE‐EPI (breath-hold); FOV covering liver, 3x3x5mm3 voxels; TR/TE/NSA/SENSE=1900ms/50ms/2/2; 11 b‐values (0-600); acquisition~10 min. MATLAB-based images processing comprised 1) Inter-scan image registration (volume preserving free-form deformation6); 2) Voxelwise fitting of D and A [eq.2] to S(b200-600) (for b>200, [eq.1] reduces to [eq.2], assuming D<2cm) on DWI (b=600), transfer of ROIs to corresponding f-maps for calculation of median ROI f before and after Salovum® intake and 4) Mann-Whitney U-test for statistical significance (α-level=0.05). Results Liver and metastases were well visualised on DWIs and f-maps Median f in metastatic tissue increased after intake of Salovum® in 5/6 patients, but decreased in one patient (Fig.2) (p<0.0001). Discussion/Conclusion The increased perfusion fraction on day 2 may offer a “window of opportunity” for improved transport of drugs to tumour cells. The increase in f was small, and perhaps not clinically significant, suggesting that additional time points after Salovum® intake and dose escalation be investigated, as well as intra-tumour effect heterogeneity. The proposed IVIM approach is a promising, non-invasive method for studying Salovum® induced changes in liver metastases in vivo. Further optimisation and fractionation studies should be conducted, and IVIM derived parameters should be compared to other techniques for perfusion or IFP measurements. References 1Rofstad,E.K.,et al.,Neoplasia. 2009;11(11):1243-51. 2Milosevic,M.F.,et al.,1999;43(5):1111-23. 3Wiig, H.,et al.,1982;42(2):159-64. 4Al-Olama, M.et al., 2011;50(7):1098-104. 5Le Bihan, D., et al., 1988;168(2):497-505. 6Rueckert, D., et al., 1999;18(8):712-21.
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- Jalnefjord, Oscar, 1989, et al.
(författare)
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Comparison of methods for estimation of the intravoxel incoherent motion (IVIM) diffusion coefficient (D) and perfusion fraction (f)
- 2018
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 31:6, s. 715-723
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Intravoxel incoherent motion (IVIM) shows great potential in many applications, e.g., tumor tissue characterization. To reduce image-quality demands, various IVIM analysis approaches restricted to the diffusion coefficient (D) and the perfusion fraction (f) are increasingly being employed. In this work, the impact of estimation approach for D and f is studied. Materials and methods: Four approaches for estimating D and f were studied: segmented IVIM fitting, least-squares fitting of a simplified IVIM model (sIVIM), and Bayesian fitting of the sIVIM model using marginal posterior modes or posterior means. The estimation approaches were evaluated in terms of bias and variability as well as ability for differentiation between tumor and healthy liver tissue using simulated and in vivo data. Results: All estimation approaches had similar variability and ability for differentiation and negligible bias, except for the Bayesian posterior mean of f, which was substantially biased. Combined use of D and f improved tumor-to-liver tissue differentiation compared with using D or f separately. Discussion: The similar performance between estimation approaches renders the segmented one preferable due to lower numerical complexity and shorter computational time. Superior tissue differentiation when combining D and f suggests complementary biologically relevant information.
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