The first clinical implementation of a real-time six degree of freedom target tracking system during radiation therapy based on Kilovoltage Intrafraction Monitoring (KIM).
We present the first clinical implementation of a real-time six-degree of freedom (6DoF) Kilovoltage Intrafraction Monitoring (KIM) system which tracks the cancer target translational and rotational motions during treatment. The method was applied to measure and correct for target motion during stereotactic body radiotherapy (SBRT) for prostate cancer.



Patient: A patient with prostate adenocarcinoma undergoing SBRT with 36.25Gy, delivered in 5 fractions was enrolled in the study. 6DoF KIM technology: 2D positions of three implanted gold markers in each of the kV images (125kV, 10mA at 11Hz) were acquired continuously during treatment. The 2D→3D target position estimation was based on a probability distribution function. The 3D→6DoF target rotation was calculated using an iterative closest point algorithm. The accuracy and precision of the KIM method was measured by comparing the real-time results with kV-MV triangulation.



Of the five treatment fractions, KIM was utilised successfully in four fractions. The intrafraction prostate motion resulted in three couch shifts in two fractions when the prostate motion exceeded the pre-set action threshold of 2mm for more than 5s. KIM translational accuracy and precision were 0.3±0.6mm, -0.2±0.3mm and 0.2±0.7mm in the Left-Right (LR), Superior-Inferior (SI) and Anterior-Posterior (AP) directions, respectively. The KIM rotational accuracy and precision were 0.8°±2.0°, -0.5°±3.3° and 0.3°±1.6° in the roll, pitch and yaw directions, respectively.



This treatment represents, to the best of our knowledge, the first time a cancer patient's tumour position and rotation have been monitored in real-time during treatment. The 6 DoF KIM system has sub-millimetre accuracy and precision in all three translational axes, and less than 1° accuracy and 4° precision in all three rotational axes.
Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Australia.
Doan Trang
DT
Nguyen
Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Australia.
Ricky
R
O'Brien
Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Australia.
Jung-Ha
JH
Kim
Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Australia.
Chen-Yu
CY
Huang
Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Australia.
Lee
L
Wilton
Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Australia; School of Mathematical and Physical Sciences, The University of Newcastle, Australia.
Peter
P
Greer
School of Mathematical and Physical Sciences, The University of Newcastle, Australia.
Kimberley
K
Legge
Northern Sydney Cancer Centre, Royal North Shore Hospital, Australia.
Jeremy T
JT
Booth
Department of Oncology, Aarhus University Hospital, Denmark.
Per Rugaard
PR
Poulsen
School of Mathematical and Physical Sciences, The University of Newcastle, Australia.
Jarad
J
Martin
Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Australia. Electronic address: paul.keall@sydney.edu.au.
Paul J
PJ
Keall
D000230:Adenocarcinoma / Q000532:radiotherapy*; D000465:Algorithms; D003199:Computer Systems; D054893:Cone-Beam Computed Tomography / Q000379:methods; D057918:Fiducial Markers; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012399:Rotation
Intrafraction motion; Prostate SBRT treatment; Prostate cancer radiotherapy; Tumour motion; Tumour rotation; Tumour translation