Evaluation of an infrared camera and X-ray system using implanted fiducials in patients with lung tumors for gated radiation therapy.
OBJECTIVE
To report on the initial clinical use of a commercially available system to deliver gated treatment using implanted fiducials, in-room kV X-rays, and an infrared camera tracking system.


METHODS
ExacTrac Adaptive Gating from BrainLab is a localization system using infrared cameras and X-rays. Gating signals are the patient's breathing pattern obtained from infrared reflectors on the patient. kV X-rays of an implanted fiducial are synchronized to the breathing pattern. After localization and shift of the patient to isocenter, the breathing pattern is used to gate the radiation. Feasibility tests included localization accuracy, radiation output constancy, and dose distributions with gating. Clinical experience is reported on treatment of patients with small lung lesions.


RESULTS
Localization accuracy of a moving target with gating was 1.7 mm. Dose constancy measurements showed insignificant change in output with gating. Improvements of dose distributions on moving targets improved with gating. Eleven patients with lung lesions were implanted with 20 mmx0.7 mm gold coil (Visicoil). The implanted fiducial was used to localize and treat the patients with gating. Treatment planning and repeat computed tomographic scans showed that the change in center of gross target volume (GTV) to implanted marker averaged 2.47 mm due in part to asymmetric tumor shrinkage.


CONCLUSIONS
ExacTrac Adaptive Gating has been used to treat lung lesions. Initial system evaluation verified its accuracy and usability. Implanted fiducials are visible in X-rays and did not migrate.
Willoughby
Twyla R
TR
Department of Radiation Oncology, M. D. Anderson Cancer Center Orlando, Orlando, FL 32806, USA. twyla.willoughby@orhs.org
Forbes
Alan R
AR
Buchholz
Daniel
D
Langen
Katja M
KM
Wagner
Thomas H
TH
Zeidan
Omar A
OA
Kupelian
Patrick A
PA
Meeks
Sanford L
SL
D002138:Calibration; D004867:Equipment Design; D005240:Feasibility Studies; D006801:Humans; D007259:Infrared Rays; D008175:Lung Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D009068:Movement; D019736:Prostheses and Implants; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D012119:Respiration; D014057:Tomography, X-Ray Computed