Verification of Accuracy of CyberKnife Tumor-tracking Radiation Therapy Using Patient-specific Lung Phantoms.
OBJECTIVE
To investigate the accuracy of the CyberKnife Xsight Lung Tracking System (XLTS) compared with that of a fiducial-based target tracking system (FTTS) using patient-specific lung phantoms.


METHODS
Three-dimensional printing technology was used to make individualized lung phantoms that closely mimicked the lung anatomy of actual patients. Based on planning computed tomographic data from 6 lung cancer patients who underwent stereotactic ablative radiation therapy using the CyberKnife, the volume above a certain Hounsfield unit (HU) was assigned as the structure to be filled uniformly with polylactic acid material by a 3-dimensional printer (3D Edison, Lokit, Korea). We evaluated the discrepancies between the measured and modeled target positions, representing the total tracking error, using 3 log files that were generated during each treatment for both the FTTS and the XLTS. We also analyzed the γ index between the film dose measured under the FTTS and XLTS.


RESULTS
The overall mean values and standard deviations of total tracking errors for the FTTS were 0.36 ± 0.39 mm, 0.15 ± 0.64 mm, and 0.15 ± 0.62 mm for the craniocaudal (CC), left-right (LR), and anteroposterior (AP) components, respectively. Those for the XLTS were 0.38 ± 0.54 mm, 0.13 ± 0.18 mm, and 0.14 ± 0.37 mm for the CC, LR, and AP components, respectively. The average of γ passing rates was 100% for the criteria of 3%, 3 mm; 99.6% for the criteria of 2%, 2 mm; and 86.8% for the criteria of 1%, 1 mm.


CONCLUSIONS
The XLTS has segmentation accuracy comparable with that of the FTTS and small total tracking errors.
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Radiation Oncology, Kyung Hee University Medical Center, Kyung Hee University School of Medicine, Seoul, Republic of Korea.
Jinhong
J
Jung
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea. Electronic address: coocoori@gmail.com.
Si Yeol
SY
Song
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Sang Min
SM
Yoon
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Jungwon
J
Kwak
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
KyoungJun
K
Yoon
Department of Radiation Oncology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Republic of Korea.
Wonsik
W
Choi
Asan Institute for Life Science, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Seong-Yun
SY
Jeong
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Eun Kyung
EK
Choi
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Byungchul
B
Cho
D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000601:surgery; D057918:Fiducial Markers; D006801:Humans; D019344:Lactic Acid; D008168:Lung / Q000033:anatomy & histology; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D008488:Medical Illustration; D009068:Movement; D019047:Phantoms, Imaging; D011091:Polyesters; D011108:Polymers; D066330:Printing, Three-Dimensional; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012119:Respiration; D025321:Surgery, Computer-Assisted / Q000379:methods; D047368:Tumor Burden
D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)