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- Fyrdahl, Alexander
(författare)
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Applications of the golden angle in cardiovascular MRI
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of radial trajectories has been seen as a potential solution to highly efficient cardiovascular magnetic resonance imaging (MRI). By acquiring a broad range of spatial frequencies per repetition time, the acquisition is time-efficient and robust against motion. Of particular interest is the golden angle profile order, which promises a near-uniform k-space coverage for an arbitrary number of readouts, enabling flexible data resorting, which is critical for efficient cardiovascular MRI. In Study I the use of 2D golden angle profile ordering is explored for imaging pulmonary embolisms. The insensitivity to motion and flow is used to reduce the artifacts that otherwise degrade images of the pulmonary vasculature when imaging with thin slices. It was found that the proposed technique could improve the image quality. Another source of artifacts arises when gradients are rapidly switched, and local induction of eddy currents may perturb spin equilibrium. In Study II, we propose a generalized golden angle profile orderings in 3D which reduces eddy-current artifacts. We demonstrate the efficacy of our generalization through numerical simulations, phantom imaging and imaging of a healthy volunteer. In Study III an improved 2D golden angle profile ordering was explored which resulted in a higher degree of k-space uniformity after physiological binning. This novel profile ordering was used in combination with a phase-contrast readout to enable quantification of myocardial tissue velocity and transmitral blood flow velocity, which are essential parameters for diastolic function assessment. When compared to echocardiography, it was found that MRI could accurately quantify myocardial tissue velocity, whereas transmitral blood flow velocity was underestimated. Study IV explored a further development of Study III by proposing a 3D version of the improved profile ordering. This novel ordering was used to acquire whole-heart functional images during free-breathing in less than one minute. Together, these results indicate that golden-angle-based imaging has the potential to improve cardiovascular MRI in several areas.
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| 2. |
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| 3. |
- 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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| 4. |
- Rysz, Susanne, et al.
(författare)
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The effect of levosimendan on survival and cardiac performance in an ischemic cardiac arrest model - A blinded randomized placebo -controlled study in swine
- 2020
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Ingår i: Resuscitation. - : Elsevier BV. - 0300-9572 .- 1873-1570. ; 150, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- Background: Survival after out-of-hospital cardiac arrest remains poor. Levosimendan could be a new intervention in this setting. Therefore, we conducted a blinded, placebo controlled randomized study investigating the effects of levosimendan on survival and cardiac performance in an ischemic cardiac arrest model in swine. Methods: Twenty-four anesthetised swines underwent experimentally-induced acute myocardial infarction and ventricular fibrillation. At the start of CPR, a bolus dose of levosimendan (12 μg kg-1) or placebo was given followed by a 24-h infusion (0.2 μg kg-1 min-1) after return of spontaneously circulation. Animals were evaluated by risk of death, post-resuscitation hemodynamics and infarction size by magnetic resonance imaging (MRI) up to 32 h post arrest. Results: Spontaneous circulation was restored in all (12/12) animals in the levosimendan group compared to two thirds (8/12) in the placebo group (P = 0.09). Protocol survival was higher for the levosimendan group (P = 0.02) with an estimated 88% lower risk of death compared to placebo (hazard ratio [95% confidence interval] 0.12 [0.01-0.96], P = 0.046). Cardiac output (CO) recovered 40% faster during the first hour of the intensive care period for the levosimendan group (difference 0.13 [0.01-0.26] L min-1P = 0.04). The placebo group required higher inotropic support during the intensive care period which masked an even bigger recovery in CO in the levosimendan group (58%). The MRI showed no difference in myocardial scar size or in myocardial area at risk. Conclusions: Levosimendan given intra-arrest and during the first 24-h of post-resuscitation care improved survival and cardiac performance in this ischemic cardiac arrest model. Institutional Protocol Number; KERIC 5.2.18-14933.
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