Clinical assessment and characterization of a dual tube kilovoltage X-ray localization system in the radiotherapy treatment room.
BACKGROUND
Although flat-panel based X-ray imaging has been well tested in diagnostic radiology, its use as an image-guided-radiotherapy (IGRT) system in a treatment room is new and requires systematic assessment.


METHODS
BrainLab Novalis IGRT system was used for this study. It consists of two floor mounted kV X-ray tubes projecting obliquely into two flat-panel detectors mounted on the ceiling. The system automatically fuses the 2D localization images with 3D simulation CT image to provide positioning guidance. The following characteristics of the system were studied: (1) Coincidence of the isocenters between the IGRT and Linac; (2) Image quality; (3) Exposure; (4) Linearity, uniformity and repeatability.


RESULTS
(1) Localization accuracy and coincidence of the isocenters between the IGRT and Linac was better than 1-mm. (2) The spatial resolution was quantified using the relative modulation-transfer-function with f50=0.7-0.9 lp/mm. The variation of contrast-noise-ratio with technical settings was measured. (3) The maximal exposure of an image was less than 95 mR. An empirical relation between the exposure and the X-ray technical setting was derived. (4) The linearity, uniformity and repeatability of the system generally meet the requirements.


CONCLUSIONS
The system can be safely and reliably used as a target localization device.
Lee
Sung-Woo
SW
Radiation Oncology, St. Anne's Hospital, Fall River, Massachusetts.
Jin
Jian-Yue
JY
Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan.
Guan
Huaiqun
H
Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan.
Martin
Flavious
F
Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan.
Kim
Jae Ho
JH
Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan.
Yin
Fang-Fang
FF
Department of Radiation Oncology, Duke University Medical Center, North Carolina, U.S.A.
D004867:Equipment Design; D019544:Equipment Failure Analysis; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods; D014963:X-Ray Intensifying Screens