| 1. |
|
|
| 2. |
- Larsson, Malin, 1983-, et al.
(författare)
-
A new ultrasound-based approach to visualize target specific polymeric contrast agent
- 2011
-
Ingår i: 2011 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781457712524 ; , s. 1626-1629
-
Konferensbidrag (refereegranskat)abstract
- There are advantages of using a polymeric shelled contrast agent (CA) during ultrasound imaging instead of lipid shelled CA, e.g. particles can be attached to the surface, which enables an introduction of antibodies to the surface making the CA target specific. For this application it is essential to have a sensitive imaging technique suitable for polymeric CA. However, previously presented results have indicated difficulties in visualizing polymeric CA with commercially available contrast algorithms. Therefore a new subtraction algorithm (SA), was developed that define the difference between contrast and reference images. The aim of this study was to evaluate the response from a polymeric CA, when using the SA and compare it with existing contrast algorithms. Moreover, the possibility to detect a thin layer of CA was tested using the SA.Ultrasound short-axis images of a tissue-mimicking vessel phantom with a pulsating flow were obtained using a GE Vivid7 system (M12L) and a Philips iE33 system (S5-1). Repeated (n=91) contrast to tissue ratios (CTR) calculated at various mechanical index (MI) using the contrast algorithms pulse inversion (PI), power modulation (PM) and SA at a concentration of 105microbubbles/ml.The developed SA showed improvements in CTR compared to existing contrast algorithms. The CTRs were -0.99 dB ± 0.67 (MI 0.2), 9.46 dB ± 0.77 (MI 0.4) and 2.98 dB ± 0.60 (MI 0.8) with PI, 8.17 dB ± 1.15 (MI 0.2), 15.60 dB ± 1.29 (MI0.4) and 11.60 dB ± 0.73 (MI 0.8) with PM and 14.97 dB ± 3.97 (MI 0.2), 20.89 dB ± 3.54 (MI 0.4) and 21.93 dB ± 4.37 (MI 0.8) with the SA. In addition to this, the layer detection, when using the SA was successful.
|
|
| 3. |
|
|
| 4. |
- Larsson, Malin K., et al.
(författare)
-
Endocardial border delineation capability of a multimodal polymer-shelled contrast agent
- 2014
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundA novel polymer-shelled contrast agent (CA) with high mechanical and chemical stability was recently developed [1]. In excess to its ultrasound properties, it also supports targeted and multimodal imaging [2-4]. Even though these new possibilities have the potential to lead to new methodologies and approaches for non-invasive diagnosis, it is important that the fundamental diagnostic features in contrast-enhanced ultrasound are preserved. The aim of this study was therefore to examine the clinical use of the polymer-shelled CA by analyzing the left ventricular endocardial border delineation capability in a porcine model. In addition, physiological effects due to CA injections were studied.MethodsThe endocardial border delineation capability was assessed in a comparative study, which included three doses (1.5 ml, 3 ml and 5 ml, [5x108 MBs/ml]) of the polymer-shelled CA and the commercially available CA SonoVue® (1.5 ml, [2-5x108 MBs/ml]). Ultrasound images of the left ventricle were evaluated manually by blinded observers (n=3) according to a 6-segment model, in which each segment was graded as 0=not visible, 1=barely visible or 2=well visible, as well as semi-automatically by a segmentation software. Furthermore, duration of clinically useful contrast enhancement and changes in physiological parameters were evaluated.ResultsFor the highest dose of the polymer-shelled CA, the obtained segment scores, time for clinically sufficient contrast enhancement and semi-automatic delineation capability were comparable to SonoVue®. Moreover, neither dose of the polymer-shelled CA did affect the physiological parameters.ConclusionThis study demonstrated that the polymer-shelled CA can be used in contrast-enhanced diagnostic imaging without influence on major physiological parameters.
|
|
| 5. |
- Larsson, Malin K., et al.
(författare)
-
Endocardial border delineation capability of a novel multimodal polymer-shelled contrast agent
- 2014
-
Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 12, s. 24-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: A novel polymer-shelled contrast agent (CA) with multimodal and target-specific potential was developed recently. To determine its ultrasonic diagnostic features, we evaluated the endocardial border delineation as visualized in a porcine model and the concomitant effect on physiological variables. Methods: Three doses of the novel polymer-shelled CA (1.5 ml, 3 ml, and 5 ml [5 x 10(8) microbubbles (MBs)/ml]) and the commercially available CA SonoVue (1.5 ml [2-5 x 10(8) MBs/ml]) were used. Visual evaluations of ultrasound images of the left ventricle were independently performed by three observers who graded each segment in a 6-segment model as either 0 = not visible, 1 = weakly visible, or 2 = visible. Moreover, the duration of clinically useful contrast enhancement and the left ventricular opacification were determined. During anesthesia, oxygen saturation, heart rate, and arterial pressure were sampled every minute and the effect of injection of CA on these physiological variables was evaluated. Results: The highest dose of the polymer-shelled CA gave results comparable to SonoVue. Thus, no significant difference in the overall segment score distribution (2-47-95 vs. 1-39-104), time for clinically sufficient contrast enhancement (20-40 s for both) and left ventricular overall opacification was found. In contrast, when comparing the endocardial border delineation capacity for different regions SonoVue showed significantly higher segment scores for base and mid, except for the mid region when injecting 1.5 ml of the polymer-shelled CA. Neither high nor low doses of the polymer-shelled CA significantly affected the investigated physiological variables. Conclusions: This study demonstrated that the novel polymer-shelled CA can be used in contrast-enhanced diagnostic imaging without influence on major physiological variables.
|
|
| 6. |
- Larsson, Malin, et al.
(författare)
-
Visualization of multimodal polymer-shelled contrast agents using ultrasound contrast sequences : an experimental study in a tissue mimicking flow phantom
- 2013
-
Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 11, s. 33-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: A multimodal polymer-shelled contrast agent (CA) with target specific potential was recently developed and tested for its acoustic properties in a single element transducer setup. Since the developed polymeric CA has different chemical composition than the commercially available CAs, there is an interest to study its acoustic response when using clinical ultrasound systems. The aim of this study was therefore to investigate the acoustic response by studying the visualization capability and shadowing effect of three polymer-shelled CAs when using optimized sequences for contrast imaging. Methods: The acoustic response of three types of the multimodal CA was evaluated in a tissue mimicking flow phantom setup by measuring contrast to tissue ratio (CTR) and acoustic shadowing using five image sequences optimized for contrast imaging. The measurements were performed over a mechanical index (MI) range of 0.2-1.2 at three CA concentrations (10(6), 10(5), 10(4) microbubbles/ml). Results: The CTR-values were found to vary with the applied contrast sequence, MI and CA. The highest CTR-values were obtained when a contrast sequence optimized for higher MI imaging was used. At a CA concentration of 106 microbubbles/ml, acoustic shadowing was observed for all contrast sequences and CAs. Conclusions: The CAs showed the potential to enhance ultrasound images generated by available contrast sequences. A CA concentration of 106 MBs/ml implies a non-linear relation between MB concentration and image intensity.
|
|
| 7. |
- Widman, Erik, et al.
(författare)
-
Feasibility of shear wave elastography for plaque characterization
- 2014
-
Ingår i: IEEE International Ultrasonics Symposium, IUS. - 9781479970490 ; , s. 1818-1821
-
Konferensbidrag (refereegranskat)abstract
- Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque in the common carotid artery and quantitative characterization methods are needed. In this study, shear wave elastography (SWE) was used to characterize soft plaque mimicking inclusions in three atherosclerotic arterial phantoms by using phase velocity analysis in a static environment. The results were validated with axial tensile mechanical testing (MT). SWE measured a mean shear modulus of 5.8 ± 0.3 kPa and 25.0 ± 1.2 kPa versus 3.0 kPa and 30.0 kPa measured by mechanical testing in the soft plaques and phantom walls respectively. The results show good agreement between MT and SWE for both the plaque and phantom wall.
|
|
| 8. |
- Bjällmark, Anna, et al.
(författare)
-
Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging
- 2010
-
Ingår i: Heart and Vessels. - : Springer Science and Business Media LLC. - 0910-8327 .- 1615-2573.
-
Tidskriftsartikel (refereegranskat)abstract
- Cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD). The aim of this study was to investigate the changes in cardiovascular function induced by a single session of hemodialysis (HD) by the analysis of cardiovascular dynamics using wave intensity wall analysis (WIWA) and of systolic and diastolic myocardial function using tissue velocity imaging (TVI). Grey-scale cine loops of the left common carotid artery, conventional echocardiography and TVI images of the left ventricle were acquired before and after HD in 45 patients (17 women, mean age 54) with ESRD. The WIWA indexes, W1 preload-adjusted W1, W2 and preload-adjusted W2, and the TVI variables, isovolumic contraction velocity (IVCV), isovolumic contraction time (IVCT), peak systolic velocity (PSV), displacement, isovolumic relaxation velocity (IVRV), isovolumic relaxation time (IVRT), peak early diastolic velocity (E’) and peak late diastolic velocity (A’), were compared before and after HD. The WIWA measurements showed significant increases in W1 (p < 0.05) and preload-adjusted W1 (p < 0.01) after HD. W2 was significantly decreased (p < 0.05) after HD, whereas the change in preload-adjusted W2 was not significant. Systolic velocities, IVCV (p < 0.001) and PSV (p < 0.01), were increased after HD, whereas the AV-plane displacement were decreased (p < 0.01). For the measured diastolic variables, E’ was significantly decreased (p < 0.01) and IVRT was significantly prolonged (p < 0.05), after HD. A few correlations were found between WIWA and TVI variables. The WIWA and TVI measurements indicate that a single session of HD improves systolic function. The load dependency of the diastolic variables seems to be more pronounced than for the systolic variables. Preload-adjusted wave intensity indexes may contribute in the assessment of true LV contractility and relaxation.
|
|
| 9. |
- Eliasson, Pernilla, et al.
(författare)
-
Hypoxia mediates low cell-cycle activity and increases the proportion of long-term reconstituting hematopoietic stem cells during in vitro culture
- 2010
-
Ingår i: Experimental Hematology. - : Elsevier. - 0301-472X .- 1873-2399. ; 38:4, s. 301-310
-
Tidskriftsartikel (refereegranskat)abstract
- Objective. Recent evidence suggests that hematopoietic stem cells (HSCs) in the bone marrow (BM) are located in areas where the environment is hypoxic. Although previous studies have demonstrated positive effects by hypoxia, its role in HSC maintenance has not been fully elucidated, neither has the molecular mechanisms been delineated. Here, we have investigated the consequence of in vitro incubation of HSCs in hypoxia prior to transplantation and analyzed the role of hypoxia-inducible factor (HIF)-1 alpha. Materials and Methods. HSC and progenitor populations isolated from mouse BM were cultured in 20% or 1% O-2, and analyzed for effects on cell cycle, expression of cyclin-dependent kinase inhibitors genes, and reconstituting ability to lethally irradiated mice. The involvement of HIF-1 alpha was studied using methods of protein stabilization and gene silencing. Results. When long-term FLT3(-)CD34(-)Lin(-)Sca-1(+)c-Kit(+) (LSK) cells were cultured in hypoxia, cell numbers were significantly reduced in comparison to normoxia. This was due to a decrease in proliferation and more cells accumulating in G(0). Moreover, the proportion of HSCs with long-term engraftment potential was increased. Whereas expression of the cyclin-dependent kinase inhibitor genes p21(cip1), p27(Kip1), and p57(Kip2) increased in LSK cells by hypoxia, only p21(cip1) was upregulated in FLT3(-)CD34(-)LSK cells. We could demonstrate that expression of p27(KiP1) and p57(Kip2) was dependent of HIF-1 alpha. Surprisingly, overexpression of constitutively active HIF-1 alpha or treatment with the HIF stabilizer agent FG-4497 led to a reduction in HSC reconstituting ability. Conclusions. Our results imply that hypoxia, in part via HIF-1 alpha, maintains HSCs by decreasing proliferation and favoring quiescence.
|
|
| 10. |
- Falkmer, Marita, et al.
(författare)
-
Recognition of facially expressed emotions and visual search strategies in adults with Asperger syndrome
- 2011
-
Ingår i: RES AUTISM SPECTR DISORD. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:1, s. 210-217
-
Tidskriftsartikel (refereegranskat)abstract
- Can the disadvantages persons with Asperger syndrome frequently experience with reading facially expressed emotions be attributed to a different visual perception, affecting their scanning patterns? Visual search strategies, particularly regarding the importance of information from the eye area, and the ability to recognise facially expressed emotions were compared between 24 adults with Asperger syndrome and their matched controls. While wearing a head mounted eye tracker, the participants viewed 12 pairs of photos of faces. The first photo in each pair was cut up into puzzle pieces. Six of the 12 puzzle pieced photos had the eyes bisected. The second photo showed a happy, an angry and a surprised face of the same person as in the puzzle pieced photo. Differences in visual search strategies between the groups were established. Adults with Asperger syndrome had greater difficulties recognizing these basic emotions than controls. The distortion of the eye area affected the ability to identify emotions even more negatively for participants with Asperger syndrome.
|
|
| 11. |
- Falkmer, Marita, et al.
(författare)
-
The importance of the eye area in face identification abilities and visual search strategies in persons with Asperger syndrome
- 2010
-
Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 4:4, s. 724-730
-
Tidskriftsartikel (refereegranskat)abstract
- Partly claimed to explain social difficulties observed in people with Asperger syndrome, face identification and visual search strategies become important. Previous research findings are, however, disparate. In order to explore face identification abilities and visual search strategies, with special focus on the importance of the eye area, 24 adults with Asperger syndrome and matched controls viewed puzzle pieced photos of faces, in order to identify them as one of three intact photos of persons. Every second puzzle pieced photo had the eyes distorted. Fixation patterns were measured by an eye tracker. Adults with Asperger syndrome had greater difficulties in identifying faces than controls. However, the entire face identification superiority in controls was found in the condition when the eyes were distorted supporting that adults with Aspergers syndrome do use the eye region to a great extent in face identification. The visual search strategies in controls were more effective and relied on the use of the 'face information triangle', i.e. the two eyes and the mouth, while adults with Asperger syndrome had more fixations on other parts of the face, both when obtaining information and during the identification part, suggesting a less effective use of the 'face information triangle'.
|
|
| 12. |
- Falkmer, Marita, et al.
(författare)
-
The influences of static and interactive dynamic facial stimuli on visual strategies in persons with Asperger syndrome
- 2011
-
Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:2, s. 935-940
-
Tidskriftsartikel (refereegranskat)abstract
- Several studies, using eye tracking methodology, suggest that different visual strategies in persons with autism spectrum conditions, compared with controls, are applied when viewing facial stimuli. Most eye tracking studies are, however, made in laboratory settings with either static (photos) or non-interactive dynamic stimuli, such as video clips. Whether or not these results are transferable to a "real world" dialogue situation remains unclear. In order to examine the consistency of visual strategies across conditions, a comparison of two static conditions and an interactive dynamic "real world" condition, in 15 adults with Asperger syndrome and 15 matched controls, was made using an eye tracker. The static stimuli consisted of colour photos of faces, while a dialogue between the participants and the test leader created the interactive dynamic condition. A within-group comparison showed that people with AS, and their matched controls, displayed a high degree of stability in visual strategies when viewing faces, regardless of the facial stimuli being static or real, as in the interactive dynamic condition. The consistency in visual strategies within the participants suggests that results from studies with static facial stimuli provide important information on individual visual strategies that may be generalized to "real world" situations.
|
|
| 13. |
- Hayashi, Shirley Yumi, et al.
(författare)
-
Left ventricular mechanical dyssynchrony in patients with different stages of chronic kidney disease and the effects of hemodialysis
- 2013
-
Ingår i: Hemodialysis International. - : Wiley-Blackwell. - 1492-7535 .- 1542-4758. ; 17:3, s. 346-358
-
Tidskriftsartikel (refereegranskat)abstract
- Left ventricular (LV) dyssynchrony is a known cause of mortality in patients with heart failure and may possibly play a similar role in patients with chronic kidney disease (CKD) in whom sudden death is one of the most common and as yet not fully explained cause of death. LV synchronicity and its relationship with increased volume load and various biomarkers was analyzed in 145 patients including 53 patients with CKD stages 3 and 4 and in 92 CKD stage 5 patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) using color tissue Doppler imaging and tissue synchronization imaging. The HD patients were evaluated both before and after a single HD session. LV dyssynchrony was defined as a regional difference in time to peak systolic myocardial velocity, between 12 LV segments>105milliseconds. LV dyssynchrony was present in 54% of the patients with no difference between CKD 3 and 4 (58%), HD (48%), and PD (51%). LV dyssynchrony was independently associated with LV mass index and increased estimation of LV end-diastolic pressure. A single HD session resulted in significant changes in LV synchronicity variableswith improvement in 50% of the patientsespecially in patients with higher myocardial systolic velocities and lower LV mass index. Abnormalities in LV synchronicity are highly prevalent in CKD patients already prior to dialysis treatment and are associated with LV hypertrophy, LV dysfunction and load conditions, underlining the importance of volume status for LV synchronicity in CKD patients.
|
|
| 14. |
- Kremer, F., et al.
(författare)
-
Spatial compounding for 2D strain estimation in the mouse heart : a pilot study
- 2010
-
Konferensbidrag (refereegranskat)abstract
- Estimating cardiac strain in the mouse in the lateral direction usingspeckle tracking with adapted clinical equipment was shown to be challenging dueto the fast heart rate and the large speckle size relative to the wallthickness. Compounding axial motion estimates acquired from different insonationangles can potentially improve lateral strain estimates. Therefore, the aim ofthis study was to test the feasibility of this methodology in the murine heartbased on simulated data sets. A 3D kinematic model of a murine left ventriclewas simulated and filled randomly with scatterers. Ultrasound short-axis images(10mm 6mm) were obtained by assuming a linear array transducer. Beam steeringwas simulated at 3 different angles (22, 0, 22). Axial motion was estimated ineach data set by 1D cross-correlation. A dynamic programming approach wasintegrated in the motion estimation algorithm to avoid discontinuities. Axialcomponents were combined to reconstruct the in-plane motion vector. The 2Ddisplacement fields were subsequently accumulated over the whole cycle. Theprocedure was repeated for 10 different distributions of scatterers to acquire10 different RF data sets (5 for parameter tuning and 5 for comparing themethods). Radial and circumferential RMS strain errors calculated from theaccumulated motion fields were compared with those obtained with 2D speckletracking. Spatial compounding yielded significantly better radial (RMSE: 0.07370.0078 vs. 0.112 0.0094) as well as circumferential strain (RMSE: 0.102 0.0097vs. 0.281 0.054).
|
|
| 15. |
- Larsson, Matilda, et al.
(författare)
-
A novel measure to express tracking quality in ultrasound block matching
- 2010
-
Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 9781457703829 ; , s. 1636-1639
-
Konferensbidrag (refereegranskat)abstract
- Speckle de-correlation is a major problem in block matching based ultrasound methodologies as it limits the accuracy of the tracking result. It would be of benefit to have a quantitative measure expressing the local tracking quality as it would allow discarding unreliable motion estimates. We hypothesized that kernels showing sufficient gray scale pattern would more reliably track than kernels with more homogenous gray scale distributions. The aim of this study was to test this hypothesis in-silico. Ultrasound B-mode sequences were simulated from a kinematic model of the carotid artery. Two-dimensional motion was estimated using block matching with the normalized cross-correlation function as similarity measure. For each kernel, two measures of tracking quality were stored: the normalized cross-correlation coefficient (Ccc) and a measure of the amount of edges inside the kernel detected using a canny filter and counted on a pixel-by-pixel basis. As such, a quality measure (Cedge) between 0 (no edges) and 1 (nothing but edges) was obtained. Axial and lateral strains were subsequently obtained by linear regression in regions of interest (ROIs) with best/worst mean tracking quality scores. The root-mean-squared-error (RMSE) was significantly lower in regions with low Ccc (worst ROI) compared to ROIs with high Ccc. However, more edges in the kernel did indeed result in better overall tracking (lower RMSE). Thus, the proposed edge-detection method showed to be a better tracking quality measure than the commonly used Ccc.
|
|
| 16. |
- Larsson, Matilda, et al.
(författare)
-
Assessment of longitudinal strain in the Carotid artery wall using ultrasound-based Speckle tracking - validation in a sheep model
- 2013
-
Ingår i: Proceedings of the IEEE International Ultrasonics symposium, 2013.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Assessment of strain in the longitudinal direction of the arterial wall has been suggested to improve the evaluation of arterial stiffness and atherosclerosis. Recently, we showed the feasibility of ultrasound speckle tracking to assess carotid longitudinal strain in-silico and in-vitro. However, validation in the more challenging in-vivo setting is still lacking. The aim of this study was to validate longitudinal strain assessment in the common carotid artery (CCA) in an animal setup. The left CCAs of five sheep were exposed during Isoflurane anesthesia and sonomicrometry crystals were sutured onto the artery wall to obtain reference longitudinal strain. Ultrasound long-axis images were recorded at baseline and hypertension (Phenylephrine) and an in-house speckle tracking algorithm was applied to estimate longitudinal strain. The estimated strain curves varied cyclically throughout the cardiac cycles, showing a lengthening of the arterial segment in systole. A significant correlation between peak systolic estimated and reference strain was found (r=0.95, p < 0.001). The results indicate the feasibility of arterial longitudinal strain assessment in-vivo using ultrasound speckle tracking.
|
|
| 17. |
- Larsson, Matilda, et al.
(författare)
-
Carotid strain estimation using an ultrasound-based speckle tracking algorithm
- 2012
-
Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781467345613 ; , s. 1394-1397
-
Konferensbidrag (refereegranskat)abstract
- Carotid strain imaging using ultrasound-based speckle tracking has showed potential in risk stratification of cardiovascular diseases. However, assessing strain in the artery wall and in atherosclerotic plaques is challenging because of small dimensions and low deformations in relation to the applied ultrasound wavelength. High-resolution ultrasound has potential to improve the speckle tracking performance by increasing spatial resolution. The aim of this study was to compare carotid strain estimation by speckle tracking using standard clinical ultrasound and high-resolution ultrasound in an experimental setup. Ultrasound long-axis images were obtained using a standard clinical ultrasound system (Vivid7) and a high-resolution ultrasound system (Vevo2100) in dynamic phantoms mimicking the carotid artery. Speckle tracking was performed to estimate radial and longitudinal strain whereas sonomicrometry was used as reference. The results showed a significant better performance for speckle tracking applied on images from the high-resolution system compared to the standard clinical system.
|
|
| 18. |
- Larsson, Matilda, et al.
(författare)
-
In-vivo assessment of radial and longitudinal strain in the carotid artery using speckle tracking
- 2010
-
Ingår i: 2010 IEEE International Ultrasonics Symposium Proceedings. - : IEEE. - 9781457703829 ; , s. 1328-1331
-
Konferensbidrag (refereegranskat)abstract
- Ultrasound-based algorithms are commonly used to assess mechanical properties of arterial walls in studies of arterial stiffness and atherosclerosis. Speckle tracking based techniques used for estimation of myocardial strain can be applied on vessels to estimate strain of the arterial wall. Previous elastography studies in vessels have mainly focused on radial strain measurements, whereas the longitudinal strain has been more or less ignored. However, recently we showed the feasibility of speckle tracking to assess longitudinal strain of the carotid artery in-silico. The aim of this study was to test this methodology in-vivo. Ultrasound images were obtained in seven healthy subjects with no known cardiovascular disease (39 ± 14 years old) and in seven patients with coronary artery disease (CAD), (69 ± 4 years old). Speckle tracking was performed on the envelope detected data using our previous developed algorithm. Radial and longitudinal strains were estimated throughout two cardiac cycles in a region of interest (ROI) positioned in the posterior vessel wall. The mean peak systolic radial and longitudinal strain values from the two heart cycles were compared between the groups using a student's t-test. The mean peak radial strain was -39.1 ± 15.1% for the healthy group and -20.4 ± 7.5% for the diseased group (p = 0.01), whereas the mean peak longitudinal strain was 4.8 ± 1.1% and 3.2 ± 1.6% (p = 0.05) for the healthy and diseased group, respectively. Both peak radial and longitudinal strain values were thus significantly reduced in the CAD patient group. This study shows the feasibility to estimate radial and longitudinal strain in-vivo using speckle tracking and indicates that the method can detect differences between groups of healthy and diseased (CAD) subjects.
|
|
| 19. |
- Larsson, Matilda, et al.
(författare)
-
Ultrasound-Based Radial and Longitudinal Strain Estimation of the Carotid Artery : A Feasibility Study
- 2011
-
Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 58:10, s. 2244-2251
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrasound-based estimation of arterial wall elasticity is commonly used to assess arterial stiffness. However, previous elastography studies have mostly addressed radial strain measurements, and the longitudinal strain has been more or less ignored. This study shows the feasibility of a speckle-tracking-based algorithm for simultaneous estimation of radial and longitudinal strain in the carotid artery in silico. Additionally, these results were preliminarily confirmed in vivo.
|
|
| 20. |
- Larsson, Matilda, et al.
(författare)
-
Ultrasound-based speckle tracking for 3D Strain estimation of the Arterial wall - An experimental validation study in a tissue mimicking phantom
- 2011
-
Konferensbidrag (refereegranskat)abstract
- Arterial stiffness is an important risk factor for cardiovascular disease. As such, ultrasound-based methods have been proposed to assess arterial strain as a measure of stiffness. The aim of the current study was to validate our recently proposed speckle tracking (ST) algorithm to estimate the in-plane wall strain tensor in an experimental setup. Three polyvinyl alcohol phantoms mimicking the carotid artery were constructed with different mechanical properties (2, 3 and 4 freeze-thaw cycles). The phantoms were connected to a pump, programmed to generate carotid flow profiles at peak flows of 7, 14, 21, 28 and 35 ml/s. Long and short-axis ultrasound images were obtained using a Vivid7 Dimension system. Radial, longitudinal and circumferential strains were estimated using the ST algorithm (kernel size: 2.7λx2λ, normalized cross-correlation; spline inter-polation for subsample motion estimation; 40% window overlap). Sonomicrometry was used to acquire reference values of strain in the phantoms. Good agreement was found between the estimated radial, longitudinal and circumferential strain and the acquired reference strain. The correlation between estimated mean peak strain values and reference peak strain values was r = 0.92 (p < 0.001) for radial strain, r = 0.72 (p = 0.006) for longitudinal strain and r = 0.91 (p < 0.001) for circumferential strain.
|
|
| 21. |
- Larsson, Matilda, et al.
(författare)
-
Ultrasound speckle tracking for radial, longitudinal and circumferential strain estimation of the carotid artery : An in vitro validation via sonomicrometry using clinical and high-frequency ultrasound
- 2014
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 56, s. 399-408
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrasound speckle tracking for carotid strain assessment has in the past decade gained interest in studies of arterial stiffness and cardiovascular diseases. The aim of this study was to validate and directly contrast carotid strain assessment by speckle tracking applied on clinical and high-frequency ultrasound images in vitro. Four polyvinyl alcohol phantoms mimicking the carotid artery were constructed with different mechanical properties and connected to a pump generating carotid flow profiles. Gray-scale ultrasound long-and short-axis images of the phantoms were obtained using a standard clinical ultrasound system, Vivid 7 (GE Healthcare, Horten, Norway) and a high-frequency ultrasound system, Vevo 2100 (FUJIFILM, VisualSonics, Toronto, Canada) with linear-array transducers (12L / MS250). Radial, longitudinal and circumferential strains were estimated using an in-house speckle tracking algorithm and compared with reference strain acquired by sonomicrometry. Overall, the estimated strain corresponded well with the reference strain. The correlation between estimated peak strain in clinical ultrasound images and reference strain was 0.91 (p < 0.001) for radial strain, 0.73 (p < 0.001) for longitudinal strain and 0.90 (p < 0.001) for circumferential strain and for high-frequency ultrasound images 0.95 (p < 0.001) for radial strain, 0.93 (p < 0.001) for longitudinal strain and 0.90 (p < 0.001) for circumferential strain. A significant larger bias and root mean square error was found for circumferential strain estimation on clinical ultrasound images compared to high frequency ultrasound images, but no significant difference in bias and root mean square error was found for radial and longitudinal strain when comparing estimation on clinical and high-frequency ultrasound images. The agreement between sonomicrometry and speckle tracking demonstrates that carotid strain assessment by ultrasound speckle tracking is feasible.
|
|
| 22. |
|
|
| 23. |
- Nordenfur, Tim, 1990-, et al.
(författare)
-
Cardiac fusion imaging of 3D echocardiography and coronary computed tomography angiography
- 2014
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Background. The choice of treatment strategy for coronary artery disease is often based on: 1) anatomical information on stenosis locations, and 2) functional information on their haemodynamic relevance, e.g. myocardial deformation or perfusion. Inspecting a single fused image containing both anatomical and functional information, as opposed to viewing separate images side-by-side, facilitates this treatment choice. The aim of this study is to develop a novel cardiac fusion imaging technique to combine 3D+time echocardiography (3DE) (functional information) with coronary computed tomography angiography (CCTA) (anatomical information).Method. 3DE and CCTA data sets were obtained from 20 patients with suspected coronary artery disease. The coronary artery tree was segmented from the CCTA images. A semi-automatic fusion algorithm was developed to perform the following steps: The left ventricle (LV) 3D surfaces were segmented in the CCTA image and 3DE images and used to align the two data sets. The moving 3DE LV was then visualized along with the CCTA coronary arteries. Myocardial strain was estimated and visualized on the LV surface.Results. Preliminary fusion results from images of one patient have been obtained. The figure shows the CCTA coronary artery tree aligned with a) 3DE LV endocardium in end-systole, b) 3DE LV endocardium in end-diastole, and c) 3DE LV with colour-coded instantaneous longitudinal strain.Discussion. Preliminary results show that fusion of CCTA and 3DE images is feasible. However, the algorithm needs to be further developed to increase automation and include other functional parameters, such as myocardial perfusion. Moreover, a validation study to assess algorithm performance and diagnostic value in multiple patients will be performed.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Ughi, Giovanni J., et al.
(författare)
-
Automatic three-dimensional registration of intravascular optical coherence tomography images
- 2012
-
Ingår i: Journal of Biomedical Optics. - 1083-3668 .- 1560-2281. ; 17:2, s. 026005-
-
Tidskriftsartikel (refereegranskat)abstract
- Intravascular optical coherence tomography (IV-OCT) is a catheter-based high-resolution imaging technique able to visualize the inner wall of the coronary arteries and implanted devices in vivo with an axial resolution below 20 mu m. IV-OCT is being used in several clinical trials aiming to quantify the vessel response to stent implantation over time. However, stent analysis is currently performed manually and corresponding images taken at different time points are matched through a very labor-intensive and subjective procedure. We present an automated method for the spatial registration of IV-OCT datasets. Stent struts are segmented through consecutive images and three-dimensional models of the stents are created for both datasets to be registered. The two models are initially roughly registered through an automatic initialization procedure and an iterative closest point algorithm is subsequently applied for a more precise registration. To correct for nonuniform rotational distortions (NURDs) and other potential acquisition artifacts, the registration is consecutively refined on a local level. The algorithm was first validated by using an in vitro experimental setup based on a polyvinyl-alcohol gel tubular phantom. Subsequently, an in vivo validation was obtained by exploiting stable vessel landmarks. The mean registration error in vitro was quantified to be 0.14 mm in the longitudinal axis and 7.3-deg mean rotation error. In vivo validation resulted in 0.23 mm in the longitudinal axis and 10.1-deg rotation error. These results indicate that the proposed methodology can be used for automatic registration of in vivo IV-OCT datasets. Such a tool will be indispensable for larger studies on vessel healing pathophysiology and reaction to stent implantation. As such, it will be valuable in testing the performance of new generations of intracoronary devices and new therapeutic drugs.
|
|
| 27. |
|
|
| 28. |
- Ullmark, Peter, et al.
(författare)
-
Design & visuell kommunikation : examensbok 2010
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Publiceras i samband med den första utexamineringen från kandidatprogrammet Design & Visuell Kommunikation på Malmö högskola. Boken innehåller artiklar om designforskning såväl som personliga presentationer av programmets studenter och deras examensarbeten eller portfolios. Boken definierar vad Design & Visuell Kommunikation står för i studenternas mening.
|
|
| 29. |
- Widman, Erik, et al.
(författare)
-
In vivo radial and longitudinal carotid artery plaque strain estimation via ultrasound-based speckle tracking
- 2014
-
Ingår i: 2014 IEEE International Ultrasonics Symposium (IUS). - : IEEE Computer Society. - 9781479970490 ; , s. 523-526
-
Konferensbidrag (refereegranskat)abstract
- Our objective was to assess strain in common carotid artery (CCA) plaques using a previously validated speckle tracking algorithm. Radial and longitudinal strain was measured in 7 patients (77 ± 6 years) with carotid atherosclerosis and was compared with a quantitative visual assessment grading of plaques on the Gray-Weale scale by two experienced physicians. A greater pulse-pressure adjusted radial and longitudinal strain was found in echolucent plaques compared to echogenic plaques. This study shows the feasibility of ultrasound speckle tracking strain estimation in plaques and indicates the possibility to characterize plaques using speckle tracking strain in vivo.
|
|
| 30. |
- Widman, Erik, et al.
(författare)
-
Shear wave elastography for characterization of carotid artery plaques-A feasibility study in an experimental setup
- 2012
-
Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781467345613 ; , s. 6562400-
-
Konferensbidrag (refereegranskat)abstract
- Characterization of vulnerable plaques in the carotid artery is critical for the prevention of ischemic stroke. However, ultrasound-based methods for plaque characterization used in the clinics today are limited to visual assessment and evaluation of plaque echogenicity. Shear Wave Elastography (SWE) is a new tissue characterization technique based on radiation force-induced shear wave propagation with potential use in plaque vulnerability assessment. The purpose of this study was to develop an experimental setup to test the feasibility of SWE for carotid plaque characterization. A carotid artery phantom with a soft inclusion in the wall, mimicking a vulnerable plaque, was constructed (10% polyvinyl alcohol (PVA), 3% graphite) by exposing the vessel and plaque to three and one freeze-thaw cycles (6h freeze, 6h thaw) respectively. An Aixplorer SWE system (Supersonic Imagine) was used to measure the shear wave speed (cT) in the vessel wall and plaque. The Young's modulus (E) was then calculated via the Moens-Korteweg (M-K) equation. For comparison, eight cylinders (d = 4 cm, h = 4 cm) were constructed for mechanical testing from the same PVA batch, of which four were exposed to three freeze-thaw cycles (mimicking the vessel wall) and four to one freeze-thaw cycle (mimicking the plaque). The Young's moduli for the cylinders were obtained via a displacement controlled mechanical compression test (Instron 5567) by applying 5% strain. The mean shear wave speed was 2.6 (±0.7) m/s in the vessel wall, 1.8 (±0.7) m/s in the plaque, resulting in Evessel = 11.5 (±0.5) kPa, Eplaque = 4.3 (±0.5) kPa. The compression tests resulted in E = 64.2 (±11.1) kPa in the hard cylinder and E = 9.7 (±3.1) kPa in the soft cylinder. The results showed that it was possible to distinguish between the arterial wall and the plaque. The disagreement between mechanical testing and SWE can be explained by the fact that the shear wave does not propagate monochromatically in cylindrical geometry. To achieve a better calculation of the elastic modulus, the frequency dependency of the shear wave velocity must be considered.
|
|
| 31. |
- Widman, Erik, 1981-, et al.
(författare)
-
SHEAR WAVE ELASTOGRAPHY OF THE ARTERIAL WALL – WHERE WE ARE TODAY
- 2013
-
Konferensbidrag (refereegranskat)abstract
- 1. IntroductionShear Wave Elastography (SWE) is a recently developed noninvasive method for elastography assessment using ultrasound. The technique consists of sending an acoustic radiation force (pushing sequence) into the tissue that in turn generates an orthogonal low frequency propagating shear wave. The shear wave propagation is measured real time by high speed B-mode imaging. From the B-mode images, the shear wave is tracked via normalized cross-correlation and the speed is calculated, which is used to generate an elasticity map of the tissue’s shear modulus. To date, the technique has mostly been used in large homogeneous tissues such as breast and liver where it successfully detects lesions and tumors that are easily missed with normal B-mode ultrasound [1]. SWE could potentially be applied in vascular applications to assess elasticity of the arterial wall to characterize the stiffness as an early indicator of cardiac disease. Furthermore, SWE could aid in the characterization of plaques in the carotid artery, which is critical for the prevention of ischemic stroke2. Methods and ResultsAn initial study was performed using an Aixplorer SWE system (Supersonic Imagine, France) to measure the shear modulus in a polyvinyl alcohol phantom (PVA) vessel with a plaque inclusion (Figure 1). It was possible to distinguish the softer inclusion mean shear wave speed (2.1 m/s) from the arterial wall (3.5 m/s) on the SWE colour-map, but the Young’s Modulus calculation of the arterial wall (E=19.8 kPa) did not match the measured Young’s Modulus (E=53.1 kPa) from comparative mechanical testing.We have begun implementing various pushing sequences (single unfocused push, single focused push, line push, comb push) on a programmable ultrasound machine (Verasonics, USA) using a linear transducer (Philips L7-4) in a homogeneous PVA phantom. An algorithm for one dimensional cross-correlation tracking and shear wave speed estimation has been developed and initially tested in an experimental setup3. DiscussionAccording to our initial results, it is possible that SWE could be applied in vascular applications. However, the initial mechanical testing vs. SWE comparison indicated that further development to the post processing is needed before applying it on the carotid artery, which is a heterogeneous tissue with other wave propagation properties than e.g. breast tissue. The carotid artery has a difficult geometry to study for several reasons. The intima-media complex is very thin (< 1mm), and the vessel wall is not stationary. Furthermore, the cylindrical shape of the artery produces complex wave reflections within the arterial wall, which result in a polychromatic propagation of the shear wave. A few studies have applied techniques based on SWE to the arterial wall with promising results and a pilot study demonstrating the feasibility of the technique in-vivo has been published [2]. Still, a considerable effort is needed to validate and optimize the technique for the clinical vascular setting.
|
|
| 32. |
- Widman, Erik, 1981-, et al.
(författare)
-
Speckle tracking strain estimation of a carotid artery plaque phantom - Validation via sonomicrometry
- 2013
-
Ingår i: 2013 IEEE International Ultrasonics Symposium (IUS). - : IEEE conference proceedings. - 9781467356848 ; , s. 1757-1760
-
Konferensbidrag (refereegranskat)abstract
- Current clinical ultrasound-based methods for plaque characterization are limited to visual assessment of plaque echogenicity creating demand for quantitative diagnostic tools. Our objective was to validate radial and longitudinal speckle tracking (ST) strain in phantom plaques via sonomicrometry (sono), and to compare the peak plaque and arterial wall strain. Four carotid artery gel-phantoms with a soft wall inclusion, mimicking a vulnerable plaque, were constructed. The phantoms were connected to a programmable pump simulating a carotid flow. Cineloops were acquired using a GE Vivid E9 where radial and longitudinal strain were calculated using a normalized cross-correlation ST algorithm. The region of interest was adjusted according to the plaque size. Sonomicrometry was used as a reference measurement. The correlation between estimated mean peak strain and the reference peak strain was r = 0.96 (p < 0.001) radially and r = 0.75 (p ≤ 0.005) longitudinally. The soft plaque exhibited 35.1% (SD 16.9%) greater radial (p < 0.001) and 88.6% (SD 72.0%) greater longitudinal (p < 0.001) peak strain than the arterial wall when measured with speckle tracking. It was possible to estimate plaque strain by ST and to distinguish a soft plaque from the vessel wall via strain measurements.
|
|
| 33. |
- Widman, Erik, 1981-, et al.
(författare)
-
ULTRASOUND SPECKLE TRACKING STRAIN ESTIMATION IN CAROTID ARTERY PLAQUE PHANTOM WITH SONOMICROMETRY VALIDATION
- 2013
-
Konferensbidrag (refereegranskat)abstract
- 1. IntroductionCarotid artery plaque characterization is critical for the prevention of ischemic events. Since plaque stiffness has shown to correlate with plaque vulnerability, quantification of plaque strain throughout the heart cycle would be a useful diagnostic tool. Our previous work encompassed the development and validation of a 2D speckle tracking (ST) algorithm to evaluate arterial stiffness by measuring strain in the carotid artery wall in silico, in vitro, and in vivo. The focus of previous studies has been to quantify plaque strain in the radial direction but lack validation against a ground truth measurement. Our objective was to validate radial and longitudinal strain in plaques via sonomicrometry (sono), and compare the measured plaque and arterial wall strain. 2. MethodThree carotid artery phantoms with soft wall inclusions, mimicking a vulnerable plaque, were constructed (10% polyvinyl alcohol (PVA), 3% graphite) by exposing the vessel and plaque to three and one freeze-thaw cycles (12h freeze, 12h thaw) respectively, see Fig. 1a. The phantoms were embedded in a tissue mimicking mixture (3% Agar, 4% graphite) at approximately 1cm depth with a pump (CompuFlow 1000 MR) connected to the phantom lumen simulating the carotid blood flow. B-mode cineloops (GE Vivid E9, 9LD linear transducer, 10 MHz, 42 fps) recorded the vessel movement at 20 and 30 mL/s peak flows. The radial and longitudinal deformation of the plaque and vessel wall was estimated by an in house 2D ST (kernel size 5x2 wavelengths) algorithm throughout two consecutive cycles. The region of interest was adjusted according to the plaque size. Sono crystals were placed on the plaque and vessel wall and used as a reference of truth. 3. ResultsFig. 1b and 1c show sample radial and longitudinal strain curves of a phantom with 20mL/s lumen flow with good agreement between sono and ST. A strong correlation was found at radial (r=0.67, p=0.03) and longitudinal peak systolic strain (r=0.84, p<0.001) between sono and ST. The plaque exhibited 47,3% (SD 27,4%) greater radial and 62,3% (SD 83,5%) longitudinal peak strain than the arterial wall when measured with ST. These preliminary data show that it is possible to measure radial and longitudinal strain in plaques; however, more extensive analysis is required as is the feasibility in vivo.
|
|
| 34. |
- Zahnd, G., et al.
(författare)
-
A novel method to generate synthetic ultrasound data of the carotid artery based on in vivo observation as a tool to validate algorithm accuracy
- 2012
-
Ingår i: IEEE International Ultrasonics Symposium, IUS. ; , s. 1291-1294
-
Konferensbidrag (refereegranskat)abstract
- Ultrasound imaging represents a well designed modality to estimate the motion of biological tissues in vivo, from which relevant clinical information can be assessed. However, the lack of ground truth constitutes a challenging issue when it comes to evaluate the accuracy of computerized methods. Indeed, quantification of the reliability of experimental results often involves manual or visual human operations, which may introduce subjectivity and variability. Nonetheless, numerical simulation of the imaged tissues allow a comparison with a known reference. For this purpose, we propose in this work a realistic kinematic multi-layer model of the common carotid artery. A set of 10 models was generated by randomly positioning scatterers, on which intensity, specular reflection, and bi-dimensional motion over the duration of one cardiac cycle were applied. Two computerized methods, namely a block-matching method and a segmentation method, were also applied on our model using identical parameter settings as those used for in vivo clinical data, in the objective to assess their accuracy. The tracking errors were 42 ± 40 μm and 12 ± 10 μm in the longitudinal and radial directions, respectively. The segmentation errors were 28±18 μm for the lumen diameter, and 15±10 μm for the intima-media thickness. We conclude from these results that our model can constitute a reliable method to quantify the accuracy of computerized algorithms.
|
|
| 35. |
- Zahnd, G., et al.
(författare)
-
A novel method to generete synthetic ultrasound data of the carotid artery based on in vivo observation as a tool to validate algorithm accuracy
- 2012
-
Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). ; , s. 1674-1677
-
Konferensbidrag (refereegranskat)abstract
- Ultrasound imaging represents a well designed modality to estimate the motion of biological tissues in vivo, from which relevant clinical information can be assessed. However, the lack of ground truth constitutes a challenging issue when it comes to evaluate the accuracy of computerized methods. Indeed, quantification of the reliability of experimental results often involves manual or visual human operations, which may introduce subjectivity and variability. Nonetheless, numerical simulation of the imaged tissues allow a comparison with a known reference. For this purpose, we propose in this work a realistic kinematic multi-layer model of the common carotid artery. A set of 10 models was generated by randomly positioning scatterers, on which intensity, specular reflection, and bi-dimensional motion over the duration of one cardiac cycle were applied. Two computerized methods, namely a block-matching method and a segmentation method, were also applied on our model using identical parameter settings as those used for in vivo clinical data, in the objective to assess their accuracy. The tracking errors were 42 ± 40 μm and 12 ± 10 μm in the longitudinal and radial directions, respectively. The segmentation errors were 28±18 μm for the lumen diameter, and 15±10 μm for the intima-media thickness. We conclude from these results that our model can constitute a reliable method to quantify the accuracy of computerized algorithms.
|
|
| 36. |
- Zirath, Hanna, et al.
(författare)
-
MYC inhibition induces metabolic changes leading to accumulation of lipid droplets in tumor cells
- 2013
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 110:25, s. 10258-10263
-
Tidskriftsartikel (refereegranskat)abstract
- The MYC genes are the most frequently activated oncogenes in human tumors and are hence attractive therapeutic targets. MYCN amplification leads to poor clinical outcome in childhood neuroblastoma, yet strategies to modulate the function of MYCN do not exist. Here we show that 10058-F4, a characterized c-MYC/Max inhibitor, also targets the MYCN/Max interaction, leading to cell cycle arrest, apoptosis, and neuronal differentiation in MYCN-amplified neuroblastoma cells and to increased survival of MYCN transgenic mice. We also report the discovery that inhibition of MYC is accompanied by accumulation of intracellular lipid droplets in tumor cells as a direct consequence of mitochondrial dysfunction. This study expands on the current knowledge of how MYC proteins control the metabolic reprogramming of cancer cells, especially highlighting lipid metabolism and the respiratory chain as important pathways involved in neuroblastoma pathogenesis. Together our data support direct MYC inhibition as a promising strategy for the treatment of MYC-driven tumors.
|
|
