"3D absolute shape measurement of live rabbit hearts with a superfast two-frequency phase-shifting technique," Opt. Express , (2013)

[52] Y. Wang*, J. I. Laughner, I. R. Efimov, and S. Zhang, "3D absolute shape measurement of live rabbit hearts with a superfast two-frequency phase-shifting technique," Opt. Express 21(5), 5822-5832, 2013 (Cover feature)  (Selected for May 22, 2013 issue of The Virtual Journal for Biomedical Optics); doi: 10.1364/OE.21.005822


This paper presents a two-frequency binary phase-shifting technique to measure three-dimensional (3D) absolute shape of beating rabbit hearts. Due to the low contrast of the cardiac surface, the projector and the camera must remain focused, which poses challenges for any existing binary method where the measurement accuracy is low. To conquer this challenge, this paper proposes to utilize the optimal pulse width modulation (OPWM) technique to generate high-frequency fringe patterns, and the error-diffusion dithering technique to produce low-frequency fringe patterns. Furthermore, this paper will show that fringe patterns produced with blue light provide the best quality measurements compared to fringe patterns generated with red or green light; and the minimum data acquisition speed for high quality measurements is around 800 Hz for a rabbit heart beating at 180 beats per minute.

"Mapping cardiac surface mechanics with structured light imaging," American Journal of Physiology: Heart and Circular Physiology, (2012)

J. I. Laughner, S. Zhang, H. Li, C. C. Shao, and I. R. Efimov, "Mapping cardiac surface mechanics with structured light imaging," American Journal of Physiology: Heart and Circular Physiology 303(6), H712-H720, 2012 (Image of the week of October 1, 2012, American Journal of Physiology); doi: 10.1152/ajpheart.00269.2012

Cardiovascular disease often manifests as a combination of pathological electrical and structural heart remodeling. The relationship between mechanics and electrophysiology is crucial to our understanding of mechanisms of cardiac arrhythmias and the treatment of cardiac disease. While several technologies exist for describing whole heart electrophysiology, studies of cardiac mechanics are often limited to rhythmic patterns or small sections of tissue. Here, we present a comprehensive system based on ultrafast three-dimensional (3-D) structured light imaging to map surface dynamics of whole heart cardiac motion. Additionally, we introduce a novel nonrigid motion-tracking algorithm based on an isometry-maximizing optimization framework that forms correspondences between consecutive 3-D frames without the use of any fiducial markers. By combining our 3-D imaging system with nonrigid surface registration, we are able to measure cardiac surface mechanics at unprecedented spatial and temporal resolution. In conclusion, we demonstrate accurate cardiac deformation at over 200,000 surface points of a rabbit heart recorded at 200 frames/s and validate our results on highly contrasting heart motions during normal sinus rhythm, ventricular pacing, and ventricular fibrillation.