ExacTrac X-ray 6 degree-of-freedom image-guidance for intracranial non-invasive stereotactic radiotherapy: Comparison with kilo-voltage cone-beam CT

Ma, Jinli; Chang, Zheng; Wang, Zhiheng; Jackie Wu, Q.; Kirkpatrick, John P.; Yin, Fang-Fang

doi:10.1016/j.radonc.2009.09.009

« Previous Next »Radiotherapy & Oncology
Volume 93, Issue 3 , Pages 602-608, December 2009

ExacTrac X-ray 6 degree-of-freedom image-guidance for intracranial non-invasive stereotactic radiotherapy: Comparison with kilo-voltage cone-beam CT

Jinli Ma
- Department of Radiation Oncology, Fudan University Cancer Hospital, Shanghai, China
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
- Corresponding author. Address: Department of Radiation Oncology, Fudan University Cancer Hospital, Shanghai 200032, China.
Zheng Chang
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
Zhiheng Wang
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
Q. Jackie Wu
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
John P. Kirkpatrick
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
Fang-Fang Yin
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA

Received 23 May 2009; received in revised form 25 August 2009; accepted 27 September 2009. published online 21 October 2009.

Abstract

Background and purpose

To compare the residual setup errors measured with ExacTrac X-ray 6 degree-of-freedom (6D) and cone-beam computed tomography (CBCT) for a head phantom and patients receiving intracranial non-invasive fractionated stereotactic radiotherapy (SRT).

Materials and methods

Setup data were collected on a Novalis Tx treatment unit for an anthropomorphic head phantom and 18 patients with intracranial tumors. Initial corrections were determined and corrected with the ExacTrac system only, and then the residual setup error was determined by means of three different procedures. These procedures included registrations of ExacTrac X-ray images with the corresponding digitally reconstructed radiographs (DRRs) using the ExacTrac 6D fusion, and registrations of CBCT images with the planning CT using both online 3D fusion and offline 6D fusion. The difference in residual setup errors between ExacTrac system and CBCT was computed. The impact of rotations on the difference was evaluated.

Results

A modest difference in residual setup errors was found between ExacTrac system and CBCT. The root-mean-square (RMS) of the differences observed for translations was typically <0.5mm for phantom, and <1.5mm for patients, respectively. The RMS of the differences for rotation(s) was however <0.2 degree for phantom, and <1.0 degree for patients, respectively. The impact of rotation on the setup difference was minor but not negligible.