Positioning accuracy of cone-beam computed tomography in combination with a HexaPOD robot treatment table.
OBJECTIVE
To scrutinize the positioning accuracy and reproducibility of a commercial hexapod robot treatment table (HRTT) in combination with a commercial cone-beam computed tomography system for image-guided radiotherapy (IGRT).


METHODS
The mechanical stability of the X-ray volume imaging (XVI) system was tested in terms of reproducibility and with a focus on the moveable parts, i.e., the influence of kV panel and the source arm on the reproducibility and accuracy of both bone and gray value registration using a head-and-neck phantom. In consecutive measurements the accuracy of the HRTT for translational, rotational, and a combination of translational and rotational corrections was investigated. The operational range of the HRTT was also determined and analyzed.


RESULTS
The system performance of the XVI system alone was very stable with mean translational and rotational errors of below 0.2 mm and below 0.2 degrees , respectively. The mean positioning accuracy of the HRTT in combination with the XVI system summarized over all measurements was below 0.3 mm and below 0.3 degrees for translational and rotational corrections, respectively. The gray value match was more accurate than the bone match.


CONCLUSIONS
The XVI image acquisition and registration procedure were highly reproducible. Both translational and rotational positioning errors can be corrected very precisely with the HRTT. The HRTT is therefore well suited to complement cone-beam computed tomography to take full advantage of position correction in six degrees of freedom for IGRT. The combination of XVI and the HRTT has the potential to improve the accuracy of high-precision treatments.
Meyer
Jürgen
J
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand. juergen.meyer@canterbury.ac.nz
Wilbert
Jürgen
J
Baier
Kurt
K
Guckenberger
Matthias
M
Richter
Anne
A
Sauer
Otto
O
Flentje
Michael
M
D006257:Head; D019047:Phantoms, Imaging; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012371:Robotics / Q000295:instrumentation*; D012399:Rotation; D013679:Technology, Radiologic / Q000379:methods