| 1. |
- Lindström, Lena, et al.
(författare)
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Lack of effect of synthetic pericardial substitute on right ventricular function after coronary artery bypass surgery : An echocardiographic and magnetic resonance imaging study
- 2000
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Ingår i: Scandinavian Cardiovascular Journal. - 1401-7431 .- 1651-2006. ; 34:3, s. 331-338
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Tidskriftsartikel (refereegranskat)abstract
- Abnormal right heart function after cardiac surgery is a well-known finding. Inadequate preservation during the operation and restricted cardiac motion due to pericardial adhesions have been proposed as underlying mechanisms. This study focuses on the impact of a pericardial substitute implantation on right ventricular function, using echocardiography and magnetic resonance imaging. A test group of six patients (mean age 54 years) was examined before surgery, and 4-15 days and 5-9 months after coronary artery bypass surgery, where the pericardium was closed with a biodegradable pericardial patch. A group of 11 patients (mean age 63 years) in whom the pericardium was left open served as controls. Tricuspid annulus motion was markedly decreased, abnormal septal motion was present and decreased systolic to diastolic ratio in the vena cava superior flow was present in all patients in both groups one week after surgery. At the late follow-up, all patients still had decreased tricuspid annulus motion, while 17% of the patients in the test group and 22% of the patients in the control group (ns) demonstrated normal septal motion. We conclude that closing the pericardium with a biodegradable patch does not affect the postoperative changes in right heart function normally seen after open-heart surgery.
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| 2. |
- Westin, Carl-Fredrik, et al.
(författare)
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Three-dimensional adaptive filtering in magnetic resonance angiography
- 2001
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 14:1, s. 63-71
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Tidskriftsartikel (refereegranskat)abstract
- In order to enhance 3D image data from magnetic resonance angiography (MRA), a novel method based on the theory of multidimensional adaptive filtering has been developed. The purpose of the technique is to suppress image noise while enhancing important structures. The method is based on local structure estimation using six 3D orientation selective filters, followed by an adaptive filtering step controlled by the local structure information. The complete filtering procedure requires approximately 3 minutes of computational time on a standard workstation for a 256 × 256 × 64 data set. The method has been evaluated using a mathematical vessel model and in vivo MRA data (both phase contrast and time of flight (TOF)). 3D adaptive filtering results in a better delineation of small blood vessels and efficiently reduces the high-frequency noise. Depending on the data acquisition and the original data type, contrast-to-noise ratio (CNR) improvements of up to 179% (8.9 dB) were observed. 3D adaptive filtering may provide an alternative to prolonging the scan time or using contrast agents in MRA when the CNR is low.
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| 3. |
- Wigström, Lars, et al.
(författare)
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M-mode magnetic resonance imaging : a new modality for assessing cardiac function
- 1995
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Ingår i: Clinical Physiology. - 0144-5979 .- 1365-2281. ; 15:4, s. 397-407
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic resonance imaging (MRI) studies of the heart have been used for some years, but there are few tools available to quantify cardiac motion. A method has been developed that creates an M-mode MRI image, analogous to the one used in echocardiography, to display motion along a line as a function of time. The M-mode image is created from MRI images acquired with an ordinary gradient echo cine sequence. In a cinematographic display of the images, a cursor line can be positioned in order to determine the orientation of the measurement. A resampling algorithm then calculates the appearance of the M-mode image along the cursor line. The MRI method has been compared to echocardiographic M-mode in a phantom study and by measuring mitral and tricuspid annulus motion in 20 normal subjects. The phantom study showed no significant differences between MRI and echocardiographic M-mode measurements (difference mm). The annulus motion exhibits a similar pattern using both methods and the measured amplitudes are in close agreement. M-mode MRI provides similar information to echocardiography, but the cursor line can be placed arbitrarily within the image plane and the method is thus not limited to certain acoustic windows. This makes M-mode MRI a promising technique for assessing cardiac motion.
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| 4. |
- Wigström, Lars, et al.
(författare)
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Temporally resolved 3D phase-contrast imaging
- 1996
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 36:5, s. 800-803
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Tidskriftsartikel (refereegranskat)abstract
- A conventional 3D phase contrast acquisition generates images with good spatial resolution, but often gives rise to artifacts due to pulsatile flow. 2D cine phase contrast, on the other hand, can register dynamic flow, but has a poor spatial resolution perpendicular to the imaging plane. A combination of both high spatial and temporal resolution may be advantageous in some cases, both in quantitative flow measurements and in MR angiography. The described 3D cine phase contrast pulse sequence creates a temporally resolved series of 3D data sets with velocity encoded data.
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| 5. |
- Al-Ahmad, A., et al.
(författare)
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Time-resolved three-dimensional imaging of the left atrium and pulmonary veins in the interventional suite-A comparison between multisweep gated rotational three-dimensional reconstructed fluoroscopy and multislice computed tomography
- 2008
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Ingår i: Heart Rhythm. - : Elsevier BV. - 1547-5271. ; 5:4, s. 513-519
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cardiac computed tomography (CT) is commonly used to visualize left atrial (LA) anatomy for ablation of atrial fibrillation. We have developed a new imaging technique that allows acquisition and visualization of three-dimensional (3D) cardiac images in the catheter lab. Objective: We sought to compare LA and pulmonary vein (PV) dimensions acquired using gated multisweep rotational fluoroscopy (C-arm CT) system and multislice computed tomography (MSCT) in an in vivo porcine model. Methods: A Siemens AXIOM Artis dTA C-arm system (Siemens AG, Medical Solutions) was modified to allow acquisition of four bidirectional sweeps during synchronized acquisition of the electrocardiogram signal to allow retrospective gating. C-arm CT image volumes were then reconstructed. Gated MSCT (SOMATOM Sensation 16 and 64, Siemens AG, Medical Solutions) and C-arm CT images were acquired in six animals. The two main PV diameters were measured in orthogonal axes. LA volumes were calculated. C-arm CT measurements were compared with the MSCT measurements. Results: The average PV diameters using the C-arm CT were 2.24 × 1.35 cm, versus 2.27 × 1.38 cm for CT. The average difference was 0.034 cm (1.9%) between the C-arm CT and standard CT. The average LA volume using MSCT was 49.1 ± 12.7 cm3, as compared with 51.0 ± 8.7 cm3 obtained by the C-arm CT. The average difference between the C-arm CT and the MSCT was 1.9 cm3 (3.7%). There were no significant differences in either the PV or LA measurements. Conclusions: Visualization of 3D cardiac anatomy during ablation procedures is possible and highly accurate. The 3D cardiac reconstructions acquired during ablation procedures will be valuable for procedural planning and guidance. © 2008 Heart Rhythm Society.
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| 6. |
- Bolger, Ann F, 1957-, et al.
(författare)
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Transit of blood flow through thehuman left ventricle mapped by cardiovascular magnetic resonance
- 2007
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - : Informa UK Limited. - 1097-6647 .- 1532-429X. ; 9:5, s. 741-747
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:The transit of blood through the beating heart is a basic aspect of cardiovascular physiology which remains incompletely studied. Quantification of the components of multidirectional flow in the normal left ventricle (LV) is lacking, making it difficult to put the changes observed with LV dysfunction and cardiac surgery into context.METHODS:Three dimensional, three directional, time resolved magnetic resonance phase-contrast velocity mapping was performed at 1.5 Tesla in 17 normal subjects, 6 female, aged 44+/-14 years (mean+/-SD). We visualized and measured the relative volumes of LV flow components and the diastolic changes in inflowing kinetic energy (KE). Of total diastolic inflow volume, 44+/-11% followed a direct, albeit curved route to systolic ejection (videos 1 and 2), in contrast to 11% in a subject with mildly dilated cardiomyopathy (DCM), who was included for preliminary comparison (video 3). In normals, 16+/-8% of the KE of inflow was conserved to the end of diastole, compared with 5% in the DCM patient. Blood following the direct route lost or transferred less of its KE during diastole than blood that was retained until the next beat (1.6+/-1.0 millijoules vs 8.2+/-1.9 millijoules, p<0.05); whereas, in the DCM patient, the reduction in KE of retained inflow was 18-fold greater than that of the blood tracing the direct route.CONCLUSION:Multidimensional flow mapping can measure the paths, compartmentalization and kinetic energy changes of blood flowing into the LV, demonstrating differences of KE loss between compartments, and potentially between the flows in normal and dilated left ventricles.
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| 7. |
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| 8. |
- Brandt, Einar, et al.
(författare)
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Segmentation of echo cardiographic image sequences using spatio-temporal information
- 1999
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Ingår i: Medical Image Computing and Computer-Assisted Intervention – MICCAI’99. - Berlin : Springer. - 354066503X ; , s. 410-419
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Bokkapitel (refereegranskat)abstract
- This paper describes a new method for improving border detection in image sequences by including both spatial and temporal information. The method is based on three dimensional quadrature filters for estimating local orientation. A simplification that gives a significant reduction in computational demand is also presented. The border detection framework is combined with a segmentation algorithm based on active contours or ’snakes’, implemented using a new optimization relaxation that can be solved to optimality using dynamical programming. The aim of the study was to compare segmentation performance using gradient based border detection and the proposed border detection algorithm using spatio-temporal information. Evaluation is performed both on a phantom and in-vivo data from five echocardiographic short axis image sequences. It could be concluded that when temporal information was included weak and incomplete boundaries could be found where gradient based border detection failed. Otherwise there was no significant difference in performance between the new proposed method and gradient based border detection.
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| 9. |
- Carlhall, C., et al.
(författare)
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Reply [2]
- 2006
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 291:5
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Annan publikation (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Carlhäll, Carljohan, 1973-, et al.
(författare)
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Contribution of mitral annular dynamics to LV diastolic filling with alteration in preload and inotropic state
- 2007
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 293:3, s. G1473-H1479
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Tidskriftsartikel (refereegranskat)abstract
- Mitral annular (MA) excursion during diastole encompasses a volume that is part of total left ventricular (LV) filling volume (LVFV). Altered excursion or area variation of the MA due to changes in preload or inotropic state could affect LV filling. We hypothesized that changes in LV preload and inotropic state would not alter the contribution of MA dynamics to LVFV. Six sheep underwent marker implantation in the LV wall and around the MA. After 7–10 days, biplane fluoroscopy was used to obtain three-dimensional marker dynamics from sedated, closed-chest animals during control conditions, inotropic augmentation with calcium (Ca), preload reduction with nitroprusside (N), and vena caval occlusion (VCO). The contribution of MA dynamics to total LVFV was assessed using volume estimates based on multiple tetrahedra defined by the three-dimensional marker positions. Neither the absolute nor the relative contribution of MA dynamics to LVFV changed with Ca or N, although MA area decreased (Ca, P < 0.01; and N, P < 0.05) and excursion increased (Ca, P < 0.01). During VCO, the absolute contribution of MA dynamics to LVFV decreased (P < 0.001), based on a reduction in both area (P < 0.001) and excursion (P < 0.01), but the relative contribution to LVFV increased from 18 ± 4 to 45 ± 13% (P < 0.001). Thus MA dynamics contribute substantially to LV diastolic filling. Although MA excursion and mean area change with moderate preload reduction and inotropic augmentation, the contribution of MA dynamics to total LVFV is constant with sizeable magnitude. With marked preload reduction (VCO), the contribution of MA dynamics to LVFV becomes even more important.
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