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Quality assurance of a system for improved target localization and patient

set-up that combines real-time infrared tracking

and stereoscopic X-ray imaging

Dirk Verellen * , Guy Soete, Nadine Linthout, Swana Van Acker, Patsy De Roover,

Vincent Vinh-Hung, Jan Van de Steene, Guy Storme

Department of Radiotherapy, Oncologic Center, Academic Hospital, Free University of Brussels (AZ-VUB), Laarbeeklaan 101, B-1090 Brussels, Belgium

Received 5 December 2001; received in revised form 11 October 2002; accepted 25 October 2002

Abstract

Background and purpose

: The aim of this study is to investigate the positional accuracy of a prototype X-ray imaging tool in combination

with a real-time infrared tracking device allowing automated patient set-up in three dimensions.

Material and methods

: A prototype X-ray imaging tool has been integrated with a commercially released real-time infrared tracking

device. The system, consisting of two X-ray tubes mounted to the ceiling and a centrally located amorphous silicon detector has been

developed for automated patient positioning from outside the treatment room prior to treatment. Two major functions are supported: (a)

automated fusion of the actual treatment images with digitally reconstructed radiographs (DRRs) representing the desired position; (b)

matching of implanted radio opaque markers. Measurements of known translational (up to 30.0 mm) and rotational (up to 4.0

) set-up errors

in three dimensions as well as hidden target tests have been performed on anthropomorphic phantoms.

Results

: The system’s accuracy can be represented with the mean three-dimensional displacement vector, which yielded 0.6 mm (with an

overall SD of 0.9 mm) for the fusion of DRRs and X-ray images. Average deviations between known translational errors and calculations

varied from

0.3 to 0.6 mm with a standard deviation in the range of 0.6–1.2 mm. The marker matching algorithm yielded a three-

dimensional uncertainty of 0.3 mm (overall SD: 0.4 mm), with averages ranging from 0.0 to 0.3 mm and a standard deviation in the range

between 0.3 and 0.4 mm.

Conclusions

: The stereoscopic X-ray imaging device integrated with the real-time infrared tracking device represents a positioning tool

allowing for the geometrical accuracy that is required for conformal radiation therapy of abdominal and pelvic lesions, within an acceptable

time-frame.

Keywords:

Automated patient positioning; Intra-fractional correction of three-dimensional set-up errors; Infrared markers; Stereoscopic X-ray imaging

1. Introduction

alities, the patient positioning procedures should follow

with equal pace and should, ideally, be integrated in the

Radiotherapy and Oncology 67 (2003) 129–141

Radiotherapy and Oncology 2003;67:129-141

Int. J. Radiation Oncology Biol. Phys. 2012;82(5):1627-1635

Workfl w ith stereoscopic x-rays and 6DOF

positioning achieves sub-millimeter and sub-

degree accuracy

l

6DOF positioning with 6DOF tables