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. Author manuscript; available in PMC: 2007 Nov 11.
Published in final edited form as: Int J Radiat Oncol Biol Phys. 2007 Jun 14;68(5):1572–1578. doi: 10.1016/j.ijrobp.2007.02.054

Figure 1.

Figure 1

A laser/spirometer combined respiratory breathing tracking system for breathing tracking (top) and the computer interface (bottom). Computer screen is displayed to the patient via video glasses. The breathing guide moves from right to left with constant speed and the breathing phase indicator (red ball) moves up and down according to instantaneous breathing phases.