Research

A model-based time-reversal of left ventricular motion improves cardiac motion analysis using tagged MRI data

Tareq Alrefae¹ , Irina V Smirnova² , Larry T Cook³ and Mehmet Bilgen⁴

¹  Physics, Kuwait University, Khaldia, Kuwait

²  Physical Therapy and Rehabilitation Science, The University of Kansas Medical Center, Kansas City, Kansas, USA

³  Radiology, The University of Kansas Medical Center, Kansas City, Kansas, USA

⁴  Radiology and Radiological Science, Medical University of South Carolina, Charleston, South Carolina, USA

author email corresponding author email

BioMedical Engineering OnLine 2008, 7:15doi:10.1186/1475-925X-7-15

Published:	19 May 2008

Abstract

Background

Myocardial motion is an important observable for the assessment of heart condition. Accurate estimates of ventricular (LV) wall motion are required for quantifying myocardial deformation and assessing local tissue function and viability. Harmonic Phase (HARP) analysis was developed for measuring regional LV motion using tagged magnetic resonance imaging (tMRI) data. With current computer-aided postprocessing tools including HARP analysis, large motions experienced by myocardial tissue are, however, often intractable to measure. This paper addresses this issue and provides a solution to make such measurements possible.

Methods

To improve the estimation performance of large cardiac motions while analyzing tMRI data sets, we propose a two-step solution. The first step involves constructing a model to describe average systolic motion of the LV wall within a subject group. The second step involves time-reversal of the model applied as a spatial coordinate transformation to digitally relax the contracted LV wall in the experimental data of a single subject to the beginning of systole. Cardiac tMRI scans were performed on four healthy rats and used for developing the forward LV model. Algorithms were implemented for preprocessing the tMRI data, optimizing the model parameters and performing the HARP analysis. Slices from the midventricular level were then analyzed for all systolic phases.

Results

The time-reversal operation derived from the LV model accounted for the bulk portion of the myocardial motion, which was the average motion experienced within the overall subject population. In analyzing the individual tMRI data sets, removing this average with the time-reversal operation left small magnitude residual motion unique to the case. This remaining residual portion of the motion was estimated robustly using the HARP analysis.

Conclusion

Utilizing a combination of the forward LV model and its time reversal improves the performance of motion estimation in evaluating the cardiac function.