| 1. |
- Castor, S, et al.
(författare)
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Assessment of fetal pulmonic stenosis by ultrasonography
- 1996
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Ingår i: Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography. - : Elsevier BV. - 0894-7317. ; 9:6, s. 805-13
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Tidskriftsartikel (refereegranskat)
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| 2. |
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| 3. |
- Escobar Kvitting, John-Peder, 1976-, et al.
(författare)
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How accurate is visual assessment of synchronicity in myocardial motion? An in vitro study with computer-simulated regional delay in myocardial motion : clinical implications for rest and stress echocardiography studies
- 1999
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 12:9, s. 698-705
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Tidskriftsartikel (refereegranskat)abstract
- Asynchronicity in echocardiographic images is normally assessed visually. No prior quantitative studies have determined the limitations of this approach. To quantify visual recognition of myocardial asynchronicity in echocardiographic images, computer-simulated delay phantom loops were generated from a 3.3 MHz digital image data from a normal left ventricular short-axis heart cycle acquired at 55 frames per second. Six expert observers visually assessed 30 abnormal and 3 normal loops with differing computer-induced delay patterns on 3 occasions and in this optimally simulated environment could recognize only single delays of 89 ms or more. This was improved to 71 ms or more by use of side-by-side (normal versus abnormal) comparative review. Thus visual assessment of clinically important regional delay in rest or stress echo images is limited.
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| 4. |
- Flachskampf, Frank A, et al.
(författare)
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Overestimation of flow velocity through leaks in mechanical valve prostheses and through small orifices by continuous-wave Doppler.
- 1997
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 10:9, s. 904-914
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Tidskriftsartikel (refereegranskat)abstract
- The reliability of continuous-wave Doppler flow velocity measurements through small regurgitant lesions, such as in prosthetic leakage, has not been systematically analyzed. To evaluate the accuracy of continuous-wave Doppler in prosthetic valve leakage and small orifices in an in vitro, steady-flow model-flow velocities through the leaks of twelve intact mechanical prostheses and through six circular nozzles (area 0.5 to 20 mm2) were measured at pressure drops between 30 and 105 mm Hg. These results were compared with those predicted by the modified Bernoulli equation. Laser Doppler anemometry of flow velocities through the nozzles was also performed. Despite high correlation, there was substantial overestimation of Bernoulli predicted velocities by echo Doppler in the prosthetic leaks (mean +12.3% +/- 9.4%; range 90.3% to 143.4%). In the nozzles < or = 10 mm2, but not in the largest (20 mm2) nozzle, there was also overestimation of the Bernoulli predicted velocities (mean +6.2% +/- 2%). Laser Doppler anemometry of flow velocities through the nozzles showed slightly lower values than predicted by the Bernoulli equation. Thus, continuous-wave echo Doppler overestimates flow velocities through small orifices. This apparently is, at least in part, due to transit time effects and should be taken into account when using echo Doppler in small (< 10 mm2) orifices, such as in mild to moderate regurgitant lesions and prosthetic valve leakage.
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| 5. |
- Fyrenius, Anna, et al.
(författare)
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Pitfalls in Doppler evaluation of diastolic function : insights from 3-dimensional magnetic resonance imaging
- 1999
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Ingår i: Journal of the American Society of Echocardiography. - Amsterdam : Elsevier Science B.V.. - 0894-7317 .- 1097-6795. ; 12:10, s. 817-826
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasound-Doppler assessment of diastolic function is subject to velocity errors caused by angle sensitivity and a fixed location of the sample volume. We used 3-dimensional phase contrast magnetic resonance imaging (MRI) to evaluate these errors in 10 patients with hypertension and in 10 healthy volunteers. The single (Doppler) and triple (MRI) component velocity was measured at early (E) and late (A) inflow along Doppler-like sample lines or 3-dimensional particle traces generated from the MRI data. Doppler measurements underestimated MRI velocities by 9.4% ± 8.6%; the effect on the E/A ratio was larger and more variable. Measuring early and late diastolic inflows from a single line demonstrated the error caused by their 3-dimensional spatial offset. Both errors were minimized by calculating the E/A ratio from maximal E and A values without constraint to a single line. Alignment and spatial offset are important sources of error in Doppler diastolic parameters. Improved accuracy may be achieved with the use of maximal E and A velocities from wherever they occur in the left ventricle.
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| 6. |
- Strotmann, Jörg M., et al.
(författare)
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Anatomic M-mode echocardiography : a new approach to assess regional myocardial function - A comparative in vivo and in vitro study of both fundamental and second harmonic imaging modes
- 1999
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 12:5, s. 300-307
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To evaluate the accuracy of anatomic M-mode echocardiography (AMM).Methods: Eight phantoms were rotated on a device at different insonation depths (IDs) in a water beaker. They were insonated with different transducer frequencies in fundamental imaging (FI) and second harmonic imaging (SHI), and the diameters were assessed with conventional M-mode echocardiography (CMM) and AMM with the applied angle correction (AC) after rotation. In addition, left ventricular wall dimensions were measured with CMM and AMM in FI and SHI in 10 volunteers.Results: AC had the greatest effect on the measurement error in AMM followed by ID (AC: R2 = 0.295, ID: R2 = 0.268; P < .0001). SHI improved the accuracy, and a difference no longer existed between CMM and AMM with an AC up to 60 degrees. In vivo the limit of agreement between AMM and CMM was -1.7 to +1.8 mm in SHI.Conclusion: Within its limitations (AC < 60 degrees; ID < 20 cm), AMM could be a robust tool in clinical practice.
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| 7. |
- Sun, Y, et al.
(författare)
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Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images.
- 1995
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795 .- 0735-1097 .- 1558-3597. ; 8:6, s. 904-914
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Tidskriftsartikel (refereegranskat)abstract
- A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (+/- 10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.
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| 8. |
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| 9. |
- Bolger, A F, et al.
(författare)
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Understanding continuous-wave Doppler signal intensity as a measure of regurgitant severity.
- 1997
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 10:6, s. 613-622
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Tidskriftsartikel (refereegranskat)abstract
- Continuous-wave Doppler signal intensity is commonly expected to reflect the severity of mitral regurgitation. Physical principles predict that alignment of the imaging beam, flow velocity, and turbulence can also be important or even dominant determinants of continuous-wave Doppler signal intensity. The reliability of tracking regurgitant severity with continuous-wave Doppler signal intensity was assessed in vitro with varying volume, velocity, turbulence, and beam alignment. The conditions wherein continuous-wave Doppler signal intensity increased with regurgitant volume were specific but poorly predictable combinations of orifice size, flow volume, and perfect beam alignment. Under other conditions flow velocity and turbulence effects dominated, and continuous-wave Doppler signal intensity did not reflect changing regurgitant volume. Continuous-wave Doppler signal intensity-based impressions of regurgitant severity may be unreliable and even misleading under some circumstances.
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| 14. |
- Wilkenshoff, Ursula M., et al.
(författare)
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Regional mean systolic myocardial velocity estimation by real-time color Doppler Myocardial Imaging: A new technique for quantifying regional systolic function
- 1998
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Ingår i: Journal of the American Society of Echocardiography. - : Elsevier BV. - 0894-7317 .- 1097-6795. ; 11:7, s. 683-692
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Tidskriftsartikel (refereegranskat)abstract
- A new color Doppler myocardial imaging (CDMI) system with high spatial and temporal resolution and novel postprocessing modalities has been developed that could allow quantifiable stress echocardiography. The purpose of this study was to determine whether regional myocardial systolic velocities could be accurately and reproducibly measured both at rest and during bicycle ergometry by using CDMI. Thirty normal subjects were examined with CDMI at rest, and peak mean systolic myocardial velocities (MSV) were measured for 34 predetermined left ventricular myocardial segments. Interobserver variability and intraobserver variability were established for all segments. Submaximal bicycle ergometry was performed in 20 normal subjects by using standardized weight-related increases in workload. MSV were measured at each step of exercise for 16 left ventricular stress echo segments. At rest, a base-apex gradient in regional MSV was recorded with highest longitudinal shortening velocities at the base. A similar pattern was noted for circumferential shortening MSV. Measurements were predictable and highly reproducible with low interobserver and intraobserver variability for 26 of 34 segments. Reproducibility was poor for basal anteroseptal segments in all views and mid anterior, anteroseptal, and septal segments in the short-axis views. During exercise, mid and basal segments of all walls showed a significant increase of MSV between each workload step and for apical segments between alternate steps. The resting base-apex velocity gradient observed at rest remained in all walls throughout ergometry. Thus a CDMI system with improved spatial and temporal resolution and postprocessing analysis modalities provided reproducible and accurate quantification of segmental left ventricular circumferential and longitudinal contraction both at rest and during exercise.
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