| 1. |
- Rademakers, Frank, et al.
(författare)
-
Determining optimal noninvasive parameters for the prediction of left ventricular remodeling in chronic ischemic patients
- 2013
-
Ingår i: Scandinavian Cardiovascular Journal. - : Informa Healthcare. - 1401-7431 .- 1651-2006. ; 47:6, s. 329-334
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives. DOPPLER-CIP aims to determine the optimal noninvasive parameters (myocardial function, perfusion, ventricular blood flow, cell integrity) and methodology (ergometry, echocardiography, scintigraphy, MRI) in a given ischemic substrate that best predicts the impact of an intervention (or the lack thereof) on adverse morphological ventricular remodeling and functional recovery. Moreover, the relative predictive value of each of these parameters, in respect to the cost of extracting this information in order to enable optimization of cost-effectiveness for improved health care, will be determined by this project. Design. DOPPLER-CIP is a multi-center registry study. All patients with ischemic heart disease included in this study undergo at least two noninvasive stress imaging examinations at baseline. The presence/or absence of left ventricular (LV) remodeling will be assessed after a follow-up of 2 years, during which all cardiac events will be registered. Results. 676 patients were included. Currently, baseline data analysis is almost finished and the follow-up is ongoing. Conclusions. After completion, DOPPLER-CIP will provide evidence-based guidelines toward the most effective use of cardiac imaging in the chronically ischemic heart disease patient. The study will generate information, knowledge, and insight into the new imaging methodologies and into the pathophysiology of chronic ischemic heart disease.
|
|
| 2. |
- Galderisi, Maurizio, et al.
(författare)
-
Recommendations of the European Association of Echocardiography : how to use echo-Doppler in clinical trials
- 2011
-
Ingår i: European Journal of Echocardiography. - : Oxford University Press (OUP). - 1525-2167 .- 1532-2114. ; 12:5, s. 339-353
-
Tidskriftsartikel (refereegranskat)abstract
- The European Association of Echocardiography (EAE) has developed the present recommendations to assist clinical researchers in the design, implementation, and conduction of echocardiographic protocols for clinical trials and to guarantee their quality. Clinical trials should be designed and conducted based on the knowledge of the pathophysiology of the clinical condition studied, the technical characteristics of the echo-Doppler modalities, and the variability of the tested parameters. These procedures are important to choose the most reliable and reproducible techniques and parameters. Quality assurance must be guaranteed by adequate training of peripheral site operators to obtain optimal echo-Doppler data and by using a core laboratory for accurate and reproducible data analysis.
|
|
| 3. |
- Grönlund, Christer, et al.
(författare)
-
Simultaneous quantification of myocardial and blood flow velocities based on duplex mode ultrasound imaging
- 2013
-
Ingår i: Biomedical engineering online. - : BioMed Central (BMC). - 1475-925X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Ultrasound imaging of the heart is a commonly used clinical tool to assess cardiac function. The basis for this analysis is the quantification of cardiac blood flow and myocardial velocities. These are typically measured using different imaging modes and on different cardiac cycles. However, due to beat-to-beat variations such as irregular heart rhythm and transient events, simultaneous acquisition is preferred. There exists specialized ultrasound systems for this purpose; however, it would be beneficial if this could be achieved using conventional ultrasound systems due to their wide availability. The conventional Duplex mode ultrasound allows simultaneous acquisition, however at a highly reduced spatial and temporal resolution.METHODS: The aim of this work was to present and evaluate the performance of a novel method to recover myocardial tissue velocity using conventional Duplex ultrasound imaging, and to demonstrate its feasibility for the assessment of simultaneous blood flow and myocardial velocity in-vivo. The essence of the method was the estimation of the axial phase shift of robust echogenic structures between subsequent image frames. The performance of the method was evaluated on synthetic tissue mimicking B-mode image sequences at different frame rates (20--60 Hz) and tissue velocities (peak velocities 5-15cm/s), using cardiac deformation and displacement characteristics. The performance was also compared to a standard 2-D speckle tracking technique.RESULTS: The method had an overall high performance at frame rates above 25 Hz, with less than 15% error of the peak diastolic velocity, and less than 10 ms peak timing error. The method showed superior performance compared to the 2-D tracking technique at frame rates below 50 Hz. The in-vivo quantification of simultaneous blood flow and myocardial tissue velocities verified the echocardiographic patterns and features of healthy subjects and the specific patient group.CONCLUSIONS: A novel myocardial velocity quantification method was presented and high performance at frame rates above 25Hz was shown. In-vivo quantification of simultaneous myocardial and blood flow velocities was feasible using the proposed method and conventional Duplex mode imaging. We propose that the methodology is suitable for retrospective as well as prospective studies on the mechanics and hemodynamics of the heart.
|
|
| 4. |
- Hendrickx, Jan-Jaap, et al.
(författare)
-
Familial aggregation of pure tone hearing thresholds in an aging European population
- 2013
-
Ingår i: Otology and Neurotology. - : Lippincott Williams & Wilkins. - 1531-7129 .- 1537-4505. ; 34:5, s. 838-844
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate the familial correlations and intraclass correlation of age-related hearing impairment (ARHI) in specific frequencies. In addition, heritability estimates were calculated.STUDY DESIGN: Multicenter survey in 8 European centers.SUBJECTS: One hundred ninety-eight families consisting of 952 family members, screened by otologic examination and structured interviews. Subjects with general conditions, known to affect hearing thresholds or known otologic cause were excluded from the study.RESULTS: We detected familial correlation coefficients of 0.36, 0.37, 0.36, and 0.30 for 0.25, 0.5, 1, and 2 kHz, respectively, and correlation coefficients of 0.20 and 0.18 for 4 and 8 kHz, respectively. Variance components analyses showed that the proportion of the total variance attributable to family differences was between 0.32 and 0.40 for 0.25, 0.5, 1, and 2 kHz and below 0.20 for 4 and 8 kHz. When testing for homogeneity between sib pair types, we observed a larger familial correlation between female than male subjects. Heritability estimates ranged between 0.79 and 0.36 across the frequencies.DISCUSSION: Our results indicate that there is a substantial shared familial effect in ARHI. We found that familial aggregation of ARHI is markedly higher in the low frequencies and that there is a trend toward higher familial aggregation in female compared with male subjects.
|
|
| 5. |
- 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).
|
|
| 6. |
- 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.
|
|
| 7. |
- 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.
|
|
| 8. |
- 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.
|
|
| 9. |
- 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.
|
|
| 10. |
- 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.
|
|
