Unsupervised estimation of myocardial displacement from tagged MR sequences using nonrigid registration.
We propose a fully automatic cardiac motion estimation technique that uses nonrigid registration between temporally adjacent images to compute the myocardial displacement field from tagged MR sequences using as inputs (sources) both horizontally and vertically tagged images. We present a new multisource nonrigid registration algorithm employing a semilocal deformation model that provides controlled smoothness. The method requires no segmentation. We apply a multiresolution optimization strategy for better speed and robustness. The accuracy of the algorithm is assessed on experimental data (animal model) and healthy volunteer data by calculating the root mean square (RMS) difference in position between the estimated tag trajectories and manual tracings outlined by an expert. For the approximately 20000 tag lines analyzed (45 slices over 20-40 time frames), the RMS difference between the automatic tag trajectories and the manually segmented tag trajectories was 0.51 pixels (0.25 mm) for the animal data and 0.49 pixels (0.49 mm) for the human volunteer data. The RMS difference in the separation between adjacent tag lines (RMS_TS) was also assessed, resulting in an RMS_TS of 0.40 pixels (0.19 mm) in the experimental data and 0.52 pixels (0.56 mm) in the volunteer data. These results confirm the subpixel accuracy achieved using the proposed methodology.
Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-1061, USA.
Maria J
MJ
Ledesma-Carbayo
J Andrew
JA
Derbyshire
Smita
S
Sampath
Andrés
A
Santos
Manuel
M
Desco
Elliot R
ER
McVeigh
D000328:Adult; D000465:Algorithms; D000818:Animals; D004285:Dogs; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D009068:Movement; D009200:Myocardial Contraction; D010363:Pattern Recognition, Automated; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity