1. ABSTRACT a
Background: We sought to test the feasibility and accuracy of a new commercial 3D echo based strain analysis method in a controlled phantom study.
a Methods: We designed a pulsatile heart model in water tank for ultrasound scanning to study 5 freshly harvested pig hearts. Each heart was driven by a calibrated pulsatile pump through a latex balloon secured in the left ventricular (LV) cavity. Six sonomicrometry (sono) crystals were secured on anterior and lateral aspect of LV surface to acquire displacement data of longitudinal and circumferential cardiac motion to compute strain. Cardiac motion was scanned with a new 4Z1 matrix transducer on a Siemens SC2000 ultrasound system to acquire full volume 3D image loops at frame rate > 30 VPS. Studies were conducted at 5 stroke volumes (30-70ml). Echo data was analyzed for segmental strain in a new 4D strain program by Siemens.
a Results: Increasing stroke volume also increased the degree of myocardial stretching, which was detected both by sonomicrometry and 3D echo derived strain measurements. Echo derived strain analysis showed a slight overestimation (4.5 ± 2.75%) but a good correlation (r = 0.78) in circumferential strain measurements at all stroke volumes, when compared to sonomicrometry derived strain measurements in corresponding LV segments.
a Conclusions: This new 4D echo based strain analysis program provided accurate objective evaluation of dynamic cardiac function in this non-ischemic model.
CONCLUSIONS
This new 4D echo based strain analysis program detected incremental myocardial stretching accurately in a controlled phantom study and may provide a new clinical method for objective evaluation of dynamic heart function.
DISCLOSURES
No relationships to disclose:
Muhammad Ashraf
Amanda Barr
Manali Paralkar
Daniella Ohnemus
Simone Prather
Rebecca Luoh
Jill Panosian
Aarti Jayaraman
Occasional Consultant to Siemens:
David J. Sahn
Helene Houle
BACKGROUND
Strain imaging has attracted the attention of many imaging specialists in scientific community, and is increasingly accepted for non-invasive assessment of dynamic heart function. Many studies have found echo derived strain a useful tool to delineate segmental LV dysfunction and mechanical dyssynchrony. Obviously an accurate and reproducible assessment of LV deformation or strain is important for this purpose. Doppler based strain method is limited due to angle dependence of the signal, which excludes many myocardial areas especially in parasternal views. Although 2D feature tracking technique has overcome this limitation, it provides information limited to scanning plane, which is subject to computational errors due to through plane myocardial motion.
The introduction of 3D echo is one of the major recent advances in cardiac imaging, which is rapidly finding application in clinical practice. With improved resolution quality of 3D echo it is possible to track myocardial features through pyramidal volumes of 3D image loop and compute strain parameters in all segments of heart from the same dynamic image without any concerns about out of plane myocardial motion. We sought to test the accuracy and feasibility of a new 3D echo based strain method developed by Siemens Medical Solutions.
METHODS
For this study we designed a pulsatile pig heart model in a water tank to facilitate ultrasound imaging. Pulsatile flow was generated in this pig heart model at controlled rate by a calibrated pump connected to LV cavity using a latex balloon secured at mitral annulus. We studied five freshly harvested pig hearts. Each heart was driven at five different stroke volumes (30-70ml).
We attached 3-6 crystals in pairs as shown to acquire sono data of cardiac motion both in circumferential and longitudinal direction of LV.
For echo data we acquired full volume 3D loops with a new 4Z1 matrix transducer on a Siemens SC2000 ultrasound system at frame rate > 30 VPS.  
Echo images were analyzed offline for segmental strain in the new 3D feature tracking program. This new program defines myocardial boundaries of LV with user input and tracks myocardial features through successive volumes of 3D image loop.
We computed strain values from sonomicrometry by processing displacement data between crystal pairs in custom software. Sono derived peak strain values were compared to echo derived peak strain values.
A New 3D Echo Based Strain Method to Evaluate Cardiac Mechanics: Validation Against Sonomicrometry
Muhammad Ashraf MD; Amanda Barr; Manali Paralkar; Daniella Ohnemus; Simone Prather; Rebecca Luoh;
Helene Houle, PhD; Jill Panosian; Aarti Jayaraman, MD; David J. Sahn, MD, MACC
Oregon Health & Science University, Portland, OR; Siemens Medical Solutions, Mountain View, CA
RESULTS
Both 3D echo and sonomicrometry-derived peak circumferential strain values showed a correspondingly higher values at higher stroke volumes detecting the incremental stretching of myocardium with increasing pumped stroke volume.
When compared to each other at different stroke volumes, Both 3D echo and sonomicrometry derived peak circumferential strain values showed a positive linear correlation (r = 0.78).
Strain values computed from 3D echo showed slightly higher values of peak circumferential strain at each pumped stroke volume, when compared with sonomicrometry derived circumferential strain values at the same stroke volume (4.5 ± 2.75%).
New 4D Echo based strain analysis program developed by Siemens
Sonomicrometry and 4D echo derived circumferential strain at different stroke volumes
Sonomicrometry crystal position display (left) displacement data between crystals (upper right) and strain curves derived from it (bottom right)