Mechanical quality assurance using light field for linear accelerators with camera calibration

Kwangwoo Park, Wonhoon Choi, Ki Chang Keum, Ho Lee, Jeongmin Yoon, Chang Geol Lee, Ik Jae Lee, Jaeho Cho

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)398-402
Number of pages5
JournalPhysica Medica
Issue number2
Publication statusPublished - 2016 Feb 1

Bibliographical note

Publisher Copyright:
© 2016 Associazione Italiana di Fisica Medica.

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)


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