| 1. |
- Marlevi, David, doktorand, et al.
(författare)
-
Combined spatiotemporal and frequency-dependent shear wave elastography enables detection of vulnerable carotid plaques as validated by MRI
- 2020
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- Fatal cerebrovascular events are often caused by rupture of atherosclerotic plaques. However, rupture-prone plaques are often distinguished by their internal composition rather than degree of luminal narrowing, and conventional imaging techniques might thus fail to detect such culprit lesions. In this feasibility study, we investigate the potential of ultrasound shear wave elastography (SWE) to detect vulnerable carotid plaques, evaluating group velocity and frequency-dependent phase velocities as novel biomarkers for plaque vulnerability. In total, 27 carotid plaques from 20 patients were scanned by ultrasound SWE and magnetic resonance imaging (MRI). SWE output was quantified as group velocity and frequency-dependent phase velocities, respectively, with results correlated to intraplaque constituents identified by MRI. Overall, vulnerable lesions graded as American Heart Association (AHA) type VI showed significantly higher group and phase velocity compared to any other AHA type. A selection of correlations with intraplaque components could also be identified with group and phase velocity (lipid-rich necrotic core content, fibrous cap structure, intraplaque hemorrhage), complementing the clinical lesion classification. In conclusion, we demonstrate the ability to detect vulnerable carotid plaques using combined SWE, with group velocity and frequency-dependent phase velocity providing potentially complementary information on plaque characteristics. With such, the method represents a promising non-invasive approach for refined atherosclerotic risk prediction.
|
|
| 2. |
- Marlevi, David, doktorand, et al.
(författare)
-
Multigrid reconstruction in tomographic imaging
- 2020
-
Ingår i: IEEE Transactions on Radiation and Plasma Medical Sciences. - : Institute of Electrical and Electronics Engineers (IEEE). - 2469-7311 .- 2469-7303. ; 4:3, s. 300-310
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we present an efficient methodology for multigrid tomographic image reconstruction from non-truncated projection data. By partitioning the reconstruction domain and adapting the forward and backward operators, an image can be reconstructed accurately within multiple domains of varying discretisation or regularisation. We demonstrate the efficacy of the multigrid reconstruction principle using simulated data for quantitative assessment and experimental measurements from a μ-CT scanner for a clinically relevant use case scenario. A major advantage of using multiple reconstruction grids is the possibility to drastically reduce the number of unknowns in the inverse problem, and thereby the associated computational cost. This cost reduction helps to enlarge the class of available algorithms in applications with strict limitations on computation time or resources, and it enables full system resolution reconstruction of subregions that would otherwise be infeasible for the full field of view. The numerical experiments, along with a brief error analysis, show that the expected artefacts from coarse discretisation outside the region of interest become noticeable only for large differences in discretisation between subregions.
|
|
| 3. |
- Marlevi, David, doktorand, et al.
(författare)
-
Non-invasive estimation of relative pressure in turbulent flow using virtual work-energy
- 2020
-
Ingår i: Medical Image Analysis. - : Elsevier B.V.. - 1361-8415 .- 1361-8423. ; 60
-
Tidskriftsartikel (refereegranskat)abstract
- Vascular pressure differences are established risk markers for a number of cardiovascular diseases. Relative pressures are, however, often driven by turbulence-induced flow fluctuations, where conventional non-invasive methods may yield inaccurate results. Recently, we proposed a novel method for non-turbulent flows, νWERP, utilizing the concept of virtual work-energy to accurately probe relative pressure through complex branching vasculature. Here, we present an extension of this approach for turbulent flows: νWERP-t. We present a theoretical method derivation based on flow covariance, quantifying the impact of flow fluctuations on relative pressure. νWERP-t is tested on a set of in-vitro stenotic flow phantoms with data acquired by 4D flow MRI with six-directional flow encoding, as well as on a patient-specific in-silico model of an acute aortic dissection. Over all tests νWERP-t shows improved accuracy over alternative energy-based approaches, with excellent recovery of estimated relative pressures. In particular, the use of a guaranteed divergence-free virtual field improves accuracy in cases where turbulent flows skew the apparent divergence of the acquired field. With the original νWERP allowing for assessment of relative pressure into previously inaccessible vasculatures, the extended νWERP-t further enlarges the method's clinical scope, underlining its potential as a novel tool for assessing relative pressure in-vivo.
|
|
