Development of a four-dimensional image-guided radiotherapy system with a gimbaled X-ray head.
OBJECTIVE
To develop and evaluate a new four-dimensional image-guided radiotherapy system, which enables precise setup, real-time tumor tracking, and pursuit irradiation.


METHODS
The system has an innovative gimbaled X-ray head that enables small-angle (+/-2.4 degrees ) rotations (pan and tilt) along the two orthogonal gimbals. This design provides for both accurate beam positioning at the isocenter by actively compensating for mechanical distortion and quick pursuit of the target. The X-ray head is composed of an ultralight C-band linear accelerator and a multileaf collimator. The gimbaled X-ray head is mounted on a rigid O-ring structure with an on-board imaging subsystem composed of two sets of kilovoltage X-ray tubes and flat panel detectors, which provides a pair of radiographs, cone beam computed tomography images useful for image guided setup, and real-time fluoroscopic monitoring for pursuit irradiation.


RESULTS
The root mean square accuracy of the static beam positioning was 0.1 mm for 360 degrees of O-ring rotation. The dynamic beam response and positioning accuracy was +/-0.6 mm for a 0.75 Hz, 40-mm stroke and +/-0.4 mm for a 2.0 Hz, 8-mm stroke. The quality of the images was encouraging for using the tomography-based setup. Fluoroscopic images were sufficient for monitoring and tracking lung tumors.


CONCLUSIONS
Key functions and capabilities of our new system are very promising for precise image-guided setup and for tracking and pursuit irradiation of a moving target.
Kamino
Yuichiro
Y
Mitsubishi Heavy Industries, Ltd., Tokyo, Japan.
Takayama
Kenji
K
Kokubo
Masaki
M
Narita
Yuichiro
Y
Hirai
Etsuro
E
Kawawda
Noriyuki
N
Mizowaki
Takashi
T
Nagata
Yasushi
Y
Nishidai
Takehiro
T
Hiraoka
Masahiro
M
D004867:Equipment Design; D009068:Movement; D010315:Particle Accelerators / Q000295:instrumentation; D011859:Radiography / Q000295:instrumentation; D011878:Radiotherapy / Q000295:instrumentation*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation; D013679:Technology, Radiologic / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed