- Meeting abstract
- Open Access
1140 A new method for measuring through-plane strain using slice following with inversion recovery (SFIR)
© Basha et al; licensee BioMed Central Ltd. 2008
- Published: 22 October 2008
- Slice Thickness
- Tissue Deformation
- Sinc Function
- Strain Profile
- Contrast Technique
MRI is a unique modality in imaging the motion of moving tissues including that of the heart. Tagging and phase contrast techniques have been used to noninvasively measure the myocardium motion. In this work, a new technique is proposed to measure the through-plane strain based on the changes in slice profile that occur due to the tissue deformation.
Slice following imaging
In order to capture the tissue deformation, complete knowledge about the slice profile in frequency domain is required. For a rectangular slice profile (s(t) = rect(t/B) and S(ωz) = Bsinc(Bωz), where B is the slice thickness), two samples at two different z-frequencies (tunings) are sufficient to fully describe the sinc function. This can be done by acquiring two images at two different points (tunings) in the kz direction by applying a suitable gradient moment in the z-direction during the refocusing lobe.
For a voxel with initial slice thickness B0, two intensities are acquired at two different tuning frequencies, I0 at ω0, and I1 at ω1. The new slice thickness at time t (Bt) can be estimated as Bt = sinc-1(I1/I0)/ω1. Then the local strain (εt) can be estimated as εt = (Bt/B0)-1.
To validate the proposed technique, a phantom study was conducted. A cubic phantom of side length 10 cm was compressed with a balloon blown with air and purged in constant time intervals, in the normal direction to the image plane. R-wave is simulated exactly before the balloon start to be blown. The balloon diameter was 2 cm during its maximum blowing. During the experiment, the balloon was positioned in one corner of the phantom.
In vivo studies
Two normal volunteers were consented and scanned using the proposed sequence. For all experiments, two slice following image sets were acquired at two different tunings (0,0.6). The two sets were used to estimate the strain in each voxel using the proposed algorithm.
A new technique is proposed for estimating the through plane tissue deformation from the normal slice following images. No special patterns (tags) are needed, so a high spatial resolution can be obtained.
This work was supported in part by grants from the national institute of heart, lung and blood R01HL072704 and R01HL61912, and Donald W. Reynolds Foundation grant.