Image metric-based correction (autofocusing) of motion artifacts in high-resolution trabecular bone imaging.
OBJECTIVE
To evaluate the performance of the autofocusing (AF) motion correction technique in high-resolution trabecular bone imaging where image signal-to noise ratio (SNR) is limited.


METHODS
Raw data from 26 clinical three-dimensional (3D) wrist exams were motion corrected using AF for both in-plane rotation and translation. Changes in image metrics (a measurement of image sharpness) and structural parameters subsequently computed, were used to gauge the performance of the AF algorithm, and comparisons were made with translation-only navigator-corrected results.


RESULTS
On average, AF generated images with higher image sharpness compared to the navigator echo technique. The average normalized gradient squared (NGS) metric improved by 0.40%, 0.73%, and 0.84%, respectively, following translation-only navigator, translation-only AF and combined rotation/translation AF. For all structural parameters, the rotation/translation AF resulted in an approximately two-fold greater change compared to the navigator technique.


CONCLUSIONS
The data provide evidence that errors from subtle translational and rotational motion in the structural parameters in high-resolution trabecular bone images are alleviated by AF and that the resulting improvements are superior to translation-only 2D navigator correction.
Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania, USA.
Wei
W
Lin
Glenn A
GA
Ladinsky
Felix W
FW
Wehrli
Hee Kwon
HK
Song
D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D015663:Osteoporosis, Postmenopausal / Q000473:pathology*; D014955:Wrist Joint / Q000473:pathology*