Analysis of Respiratory and Non-respiratory Motions for Patients during 4D Gated CT Simulation Procedure
Jian-Yue Jin, PhD, Munther Ajlouni,
MD, Samuel Ryu, MD, Qing
Chen, MS, Shidong Li, PhD, and Benjamin Movsas, MD
Motion control is essential for improving the radiation targeting. The patient motion signal is usually mixed with quasi-periodic respiratory motion and irregular non-respiratory motions. We have developed a technique to extract these two different motions from two correlated motion signals obtained by external markers placed on different surface areas of a patient. This study analyzes the respiratory and non-respiratory motions for patients undergoing a 4D-gated-CT simulation procedure.
Total of 24 patients were studied. Five infrared external markers were placed on a patient¡¯s chest and abdominal surfaces. The position information of each marker was recorded every 0.06-0.08 seconds. The duration of recording ranged 10-25 minutes for different patients. A computer program was written which not only calculated the respiratory and non-respiratory components in real-time, but also calculated the amplitude, the inhale, exhale and total time duration in a respiratory cycle for each cycle and for each marker. The phase information at each moment, the number of irregular cycles and the total number of cycles were also computed.
The average respiratory amplitude of a patient on the abdominal surface ranged 1.8-23.3 mm, with the mean of 7.6¡À4.5 mm, versus a range of 0.75-3.5 mm and the mean of 1.7¡À0.8 mm on the chest surface for all patients. Eight out of twenty-four patients showed some phase differences between the abdominal and chest respiratory signals. The average inhale, exhale and total times ranged 0.76-2.96, 1.01-4.09 and 2.05-7.05 seconds, respectively, with the mean of 1.33¡À0.49, 2.10¡À0.70 and 3.44¡À1.08 seconds, respectively. The percentage of irregular cycles ranged 0.7%-28%, with the mean of 12%¡À11%. For the extracted non-respiratory signals, the respiratory ripples was reduced to <0.5mm for most of the patients. There were slow-drifts as well as some sharp-motions, with 10/24 and 4/24 patients showed > 2mm and > 3mm slow-drift, respectively. The maximal drift was 6.5mm.