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. Author manuscript; available in PMC: 2016 May 1.
Published in final edited form as: Radiother Oncol. 2015 Apr 15;115(2):217–222. doi: 10.1016/j.radonc.2015.03.029

Figure 2.

Figure 2

Spectral Coherence and the consistency of respiration. The top left curve shows the tumor trajectory in the SI direction for a patient with consistent breathing, while the bottom left curve shows the trajectory of a patient with inconsistent breathing. The Fourier Transform (FFT) of consistent motion is dominated by a single frequency, while the FFT of inconsistent motion contains contributions from many frequencies. Spectral Coherence (right) is defined as the percentage of the motion spectrum below a given threshold value (denoted by the dashed line). The SC is high (0.99) in the patient with consistent breathing, and low (0.95) in the patient with inconsistent breathing.