Verification and compensation of respiratory motion using an ultrasound imaging system.
OBJECTIVE
The purpose of this study was to determine if it is feasible to use ultrasound imaging as an aid for moving the treatment couch during diagnosis and treatment procedures associated with radiation therapy, in order to offset organ displacement caused by respiratory motion. A noninvasive ultrasound system was used to replace the C-arm device during diagnosis and treatment with the aims of reducing the x-ray radiation dose on the human body while simultaneously being able to monitor organ displacements.


METHODS
This study used a proposed respiratory compensating system combined with an ultrasound imaging system to monitor the compensation effect of respiratory motion. The accuracy of the compensation effect was verified by fluoroscopy, which means that fluoroscopy could be replaced so as to reduce unnecessary radiation dose on patients. A respiratory simulation system was used to simulate the respiratory motion of the human abdomen and a strain gauge (respiratory signal acquisition device) was used to capture the simulated respiratory signals. The target displacements could be detected by an ultrasound probe and used as a reference for adjusting the gain value of the respiratory signal used by the respiratory compensating system. This ensured that the amplitude of the respiratory compensation signal was a faithful representation of the target displacement.


RESULTS
The results show that performing respiratory compensation with the assistance of the ultrasound images reduced the compensation error of the respiratory compensating system to 0.81-2.92 mm, both for sine-wave input signals with amplitudes of 5, 10, and 15 mm, and human respiratory signals; this represented compensation of the respiratory motion by up to 92.48%. In addition, the respiratory signals of 10 patients were captured in clinical trials, while their diaphragm displacements were observed simultaneously using ultrasound. Using the respiratory compensating system to offset, the diaphragm displacement resulted in compensation rates of 60%-84.4%.


CONCLUSIONS
This study has shown that a respiratory compensating system combined with noninvasive ultrasound can provide real-time compensation of the respiratory motion of patients.
Department of Mechanical Engineering, National Taipei University of Technology, Number 1, Section 3, Chung-Hsiao E. Road, Taipei 10608, Taiwan.
Ho-Chiao
HC
Chuang
Department of Mechanical Engineering, National Taipei University of Technology, Number 1, Section 3, Chung-Hsiao E. Road, Taipei 10608, Taiwan.
Hsiao-Yu
HY
Hsu
Department of Mechanical Engineering, National Taipei University of Technology, Number 1, Section 3, Chung-Hsiao E. Road, Taipei 10608, Taiwan.
Wei-Hung
WH
Chiu
Department of Mechanical Engineering, National Taipei University of Technology, Number 1, Section 3, Chung-Hsiao E. Road, Taipei 10608, Taiwan.
Der-Chi
DC
Tien
Shin Kong Wu Ho-Su Memorial Hospital, Number 95, Wen-Chang Road, Shih-Lin District, Taipei 11101, Taiwan.
Ren-Hong
RH
Wu
Shin Kong Wu Ho-Su Memorial Hospital, Number 95, Wen-Chang Road, Shih-Lin District, Taipei 11101, Taiwan.
Chung-Hsien
CH
Hsu
D003964:Diaphragm / Q000000981:diagnostic imaging / Q000502:physiology; D005240:Feasibility Studies; D005471:Fluoroscopy; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D009068:Movement; D019047:Phantoms, Imaging; D012119:Respiration; D014463:Ultrasonography; D055815:Young Adult