Length Strain Research Articles

Reproducibility and Optimization of Analysis Parameters of Tissue Doppler-Derived Strain and Strain Rate Measurements for Very Low Birth Weight Infants

To assess the effects of region of interest (ROI) size and strain length (SL) on the quality of analysis and to determine the feasibility and reproducibility of tissue Doppler-derived cardiac strain (S) and strain rate (SR) measurements for preterm infants <1500g birth weight. The beat-to-beat variation (BBV) for different combinations of ROI width (RW), ROI length (RL), and SL was determined from 60 good quality images of left and right free walls and the interventricular septum. We examined the impact of RW, RL, and SL on BBV and estimated inter- and intra-operator variability. BBV was smallest for RW=2mm. Raising SL (even at the cost of RL) led to a decrease in BBV. Several combinations provided a low BBV without significant difference. Coefficients of variation for intra- and inter-operator variability ranged from 15.1% to 65.2%. Both were lower for systolic than for diastolic values. Tissue Doppler imaging-derived S and SR measurements are feasible in very low birth weight infants. Reproducibility is comparable to older infants for systolic S and SR. For optimal analysis quality, SL and RW should be high while RL should be small (though inside segment size). Best results were obtained with RW=2mm, RL=1mm, and SL=6mm.

Feasibility and reliability of strain and strain rate measurement in neonates by optimizing the analysis parameters settings

The optimal combination of region-of-interest (ROI) size and strain length (SL) allowing two-segment strain and strain rate analyses in term neonates was investigated. The impact of different ROI sizes and SLs on the strain and strain rate beat-to-beat variation (BBV) was assessed in 80 good-quality tissue velocity images. Both BBVs decreased with increased ROI length and with increased SL ( p < 0.05). There were no significant differences in the BBVs for ROI width 2, 3 and 4 mm ( p > 0.05). Among the combinations eligible for two segment analysis, the lowest BBVs were found using SL 10 mm, ROI length 1 mm and ROI width 3 mm. Using this combination, the mean difference between the single-cycle value and two-cycle compound value for peak systolic strain rate was 6.2%, peak systolic strain was 2.9% and end systolic strain was 3.2% of the two-cycle compound mean values. Hence, strain and strain rate measurement in tissue velocity images in neonates is feasible and reliable. (E-mail: eirikpda@start.no)

2085: In vitro strain measurement in the porcine antrum using ultrasound Doppler strain rate imaging

Objectives: Strain rate imaging (SRI) enables study of deformation in soft tissues. The aim of this study was to evaluate the accuracy of SRI in measuring strain in the porcine antral wall in vitro.Methods: An experimental set-up enabled controlled distension of a porcine stomach in a saline reservoir. Radial strain obtained by SRI was compared with radial strain calculated from B-mode ultrasonography. Circumferential strain obtained by SRI was compared with circumferential strain calculated from sonomicrometry.Results: The agreement between radial strain values measured by SRI and B-mode, along and across several ultrasound beams, using US frequency 6.7 MHz and strain length (SL) = 1.9 mm was = -1.0 ± 12.1% and 0.5 ± 13.4%, respectively (mean difference ± 2SD%) and it was better than with SL 1.2 mm. Compared with sonomicrometry, SRI-determined circumferential strain using 6.7 MHz and SL = 1.9 mm was less accurate, whether averaging along or across several US beams (-9.2 ± 46.7% and 13.8 ± 51.2%, respectively).Conclusions: SRI gave accurate measurement of radial strain of the antral wall, but seemed to be less accurate for measurement of circumferential strain in vitro. Objectives: Strain rate imaging (SRI) enables study of deformation in soft tissues. The aim of this study was to evaluate the accuracy of SRI in measuring strain in the porcine antral wall in vitro. Methods: An experimental set-up enabled controlled distension of a porcine stomach in a saline reservoir. Radial strain obtained by SRI was compared with radial strain calculated from B-mode ultrasonography. Circumferential strain obtained by SRI was compared with circumferential strain calculated from sonomicrometry. Results: The agreement between radial strain values measured by SRI and B-mode, along and across several ultrasound beams, using US frequency 6.7 MHz and strain length (SL) = 1.9 mm was = -1.0 ± 12.1% and 0.5 ± 13.4%, respectively (mean difference ± 2SD%) and it was better than with SL 1.2 mm. Compared with sonomicrometry, SRI-determined circumferential strain using 6.7 MHz and SL = 1.9 mm was less accurate, whether averaging along or across several US beams (-9.2 ± 46.7% and 13.8 ± 51.2%, respectively). Conclusions: SRI gave accurate measurement of radial strain of the antral wall, but seemed to be less accurate for measurement of circumferential strain in vitro.

In vitro strain measurement in the porcine antrum using ultrasound doppler strain rate imaging

Strain rate imaging (SRI) enables study of deformation in soft tissues. The aim of this study was to evaluate the accuracy of SRI in measuring strain in the porcine antral wall in vitro. An experimental set-up enabled controlled distension of a porcine stomach in a saline reservoir. Radial strain obtained by SRI was compared with radial strain calculated from B-mode ultrasonography. Circumferential strain obtained by SRI was compared with circumferential strain calculated from sonomicrometry. The agreement between radial strain values measured by SRI and B-mode, along and across several ultrasound (US) beams, using US frequency 6.7 MHz and strain length (SL) = 1.9 mm was = –1.0 ± 12.1% and 0.5 ± 13.4%, respectively (mean difference ± 2SD%) and it was better than with SL 1.2 mm. Compared with sonomicrometry, SRI-determined circumferential strain using 6.7 MHz and SL = 1.9 mm was less accurate, whether averaging along or across several US beams (–9.2 ± 46.7% and 13.8 ± 51.2%, respectively). In conclusion, SRI gave accurate measurement of radial strain of the antral wall, but seemed to be less accurate for measurement of circumferential strain for this in vitro set-up. (E-mail: aymen.ahmed@med.uib.no)

Radial Strain Gradient Across the Normal Myocardial Wall in Open-chest Pigs Measured with Doppler Strain Rate Imaging

One of the reasons for the large variation in radial strain measured with Doppler strain rate imaging in normal myocardium might be the different strain length (SL) used during analyses. The aim of this study was to evaluate the effect of different SL settings on strain recordings and the method's ability to detect transmural radial strain gradients. In 8 anesthetized pigs (mean weight 54 kg) epicardial echocardiography was performed. Strain analysis was carried out by defining the wall as a 1-, 2-, 3-, and 4-layer structure with suitable regions of interest. Peak ejection strain was measured with SL settings of 2 to 14 mm. The systolic (ejection) strain showed large variation with SL. Sampling in one layer gave no significant reduction in strain for increasing SL. The strain in the subepicardial layer was low and decreased when the wall was divided into several layers (15.9 +/- 4.8% [2 layers]-2.1 +/- 2.4% [4 layers]; both measurements with SL = 4 mm). The method could separate 4 layers with SL of 4 mm or less, 3 layers with SL of 6 mm or less, and 2 layers with SL of 8 mm or less. When measuring radial strain in the myocardial wall the SL must be low to evaluate transmural strain gradients. With correct settings of SL and region of interest, strain in 4 layers can be distinguished. As a rule of thumb the SL should be set to approximately half the systolic thickness of the wall or half the wall layer.