Three-dimensional myocardial strain analysis based on short- and long-axismagnetic resonance tagged images using a 1D displacement field

A robust algorithm to estimate three-dimensional strain in the left-ventric ular heart wall, based on magnetic resonance (MR) grid-tagging in two sets of orthogonal image planes, is presented. Starting-point of this study was to minimize global interpolation and smoothing. Only the longitudinal displ acement was interpolated between long-axis images. Homogeneous strain analy sis was performed using small tetrahedrons. The method was tested using a s tack of short-axis images and three long-axis images in six healthy volunte ers. In addition, the method was subjected to an analytical test case, in w hich the effect of noise in tag point position on the observed strains was explored for normally distributed noise (0.5 mm RMS). In volunteers, the er ror in the longitudinal displacement due to interpolation between the long- axis image planes was -0.10 +/- 0.48 mm (mean +/- SD). The resulting error in the longitudinal strain epsilon(1) was -0.003 +/- 0.02. The analytical t est case was used to quantify the effects of three sources of errors on the observed strain. The SD of the difference between homogeneous strain and t rue strain was 0.06 for epsilon(r). The error due to the 3-D reconstruction was 0.004 for epsilon(r). The error in epsilon(r) resulting from simulated noise in the tag point position was 0.10. Equivalent results were obtained for all other strain parameters; thus, the error resulting from noise in t he tag paint position dominates the error introduced by approximations in t he method. Because the proposed method uses a minimum of global interpolati on and smoothing, it offers the prospect to detect small regions of aberran t contraction. (C) 2000 Elsevier Science Inc. All rights reserved.