Mechanical quality assurance using light field for linear accelerators with camera calibration. Issue 2 (February 2016)

• Record Type: Journal Article
• Authors: Park, Kwangwoo; Choi, Wonhoon; Keum, Ki Chang; Lee, Ho; Yoon, Jeongmin; Lee, Chang Geol; Lee, Ik Jae; Cho, Jaeho
• Is Part Of: Physica medica. Volume 32:Issue 2(2016)
• Page Start: 398
• Page End: 402
• Publication Date: 2016-02
• Subjects: Camera calibration -- Light field -- Lens distortion -- Mechanical isocenter -- Quality assurance (QA); Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2016.01.003
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: We had performed mechanical QA using digital camera. For use of camera, calibration should be prerequisite for quantitative measurement to reduce distortions. Both camera and camera calibration provided the method for mechanical QA without loss of precisions. We suggest how to calibrate camera and how to do mechanical QA using camera. Abstract: Mechanical Quality Assurance (QA) is important to assure spatially precise delivery of external-beam radiation therapy. As an alternative to the conventional-film based method, we have developed a new tool for mechanical QA of LINACs which uses a light field rather than radiation. When light passes through the collimator, a shadow is projected onto a piece of translucent paper and the resulting image is captured by a digital camera via a mirror. With this method, we evaluated the position of the LINAC isocenter and the accuracy of the gantry, collimator, and couch rotation. We also evaluated the accuracy of the digital readouts of the gantry, collimator, and couch rotation. In addition, the treatment couch position indicator was tested. We performed camera calibration as an essential pre-requisite for quantitative measurements of the position of isocenter, the linear motion of the couch, and the rotation angles of the gantry and collimator. Camera calibration reduced the measurement error to submillimeter based on uncertainty in pixel size of the image, while, without calibration, the measurement error of up to 2 mm could occur for an object with a length of 5 cm.