AAPM Banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

You are not logged in Access to this article requires a subscription. Log In

Medical Physics / Volume 38 / Issue 12 / RADIATION THERAPY PHYSICS

Med. Phys. 38, 6539 (2011); http://dx.doi.org/10.1118/1.3660773 (14 pages)

A feasibility study of using couch-based real time dosimetric device in external beam radiotherapy

Ramachandran Prabhakar, Jim Cramb, and Tomas Kron

Physical Sciences, Peter MacCallum Cancer Centre, Locked Bag 1, A’ Beckett Street, Victoria 8006, Australia

View MapView Map

(Received 12 January 2011; accepted 26 October 2011; revised 18 October 2011; published online 21 November 2011)

Full Text: Read Online (HTML) | Download PDF | Buy PDF (US$30) | View Cart
Purpose: Measurement of actual dose delivered during radiotherapy treatment aids in checking the accuracy of dose delivered to the patient. In this study, a couch-based real time dosimetric device has been proposed to measure the exit or entrance dose to a patient during external beam radiotherapy. The utility and feasibility of such a device using a 2D array of diodes has been demonstrated.
Methods: Two MAPCHECK devices: MAPCHECK (1175) and MAPCHECK 2 (both SunNuclear) were embedded in a foam block in the treatment couch of a Varian 21iX linear accelerator. The angular dependence of the detector response for both devices was studied before implementing the MAPCHECKs for experimental purposes. An Alderson Rando head phantom was scanned with the MAPCHECK and MAPCHECK 2 devices separately and four different treatment plans were generated with target volumes at three different positions simulating typical clinical situations. The analytical anisotropic algorithm (AAA) was used to compute the doses in an Eclipse treatment planning system (Varian Medical Systems). The Rando phantom with the MAPCHECK device was exposed in Clinac 21iX linear accelerator. The measured dose distribution was compared with the calculated dose distribution to check for the accuracy in dose delivery.
Results: Measured and computed dose distribution were found to agree with more than 93% of pixels passing at 3% and 3 mm gamma criteria for all the treatment plans. The couch-based real time dosimetry system may also be applied for noncoplanar beams where electronic portal imaging device (EPID) is not practical to measure the dose. Other advantages include checking the beam stability during the patient treatment, performing routine morning quality assurance (QA) tests in the linear accelerator, and to perform pretreatment verification of intensity modulated radiation therapy (IMRT). One of the drawbacks of this system is that it cannot be used for measuring the dose at 90° or 270° gantry angles.
Conclusions: This preliminary study shows that a 2D array of detectors may be used as part of the treatment couch for real time patient dosimetry in studying the dose delivered to the patient in real time and also for performing routine quality assurance.

© 2011 American Association of Physicists in Medicine

Article Outline

  1. INTRODUCTION
  2. METHODS AND MATERIALS
    1. The detector arrays
    2. Angular dependence of detector response
    3. Measurements with an anthropomorphic phantom
    4. Setup error
  3. RESULTS
    1. Angular dependence of detector response
    2. Anthropomorphic phantom
    3. Setup error
  4. DISCUSSION
  5. CONCLUSION
Digital Object Identifier
http://dx.doi.org/10.1118/1.3660773

KEYWORDS and PACS

Keywords

dosimetry, linear accelerators, phantoms, quality assurance, radiation therapy, external beam radiotherapy, treatment verification, real time dosimetry, 2D array detectors, couch

PACS

PUBLICATION DATA

ISSN

0094-2405 (print)  

Publisher

$abstract.society.value is a Member of CrossRef American Association of Physicists in Medicine

For access to fully linked references, you need to log in.

Figures (11)

Access to article objects (figures, tables, multimedia) requires a subscription; log in to view available files.
(Access to supplementary files, where available, is free for this journal.)



Close

Medical Physics is an official science journal of the AAPM and of the COMP/CCPM/IOMP
William R. Hendee, Editor
Departments of Radiology, Radiation Oncology, Biophysics, Community and Public Health, Medical College of Wisconsin
One Physics Ellipse
College Park, Maryland 20740
301-209-3352

© 2012, American Association of Physicists in Medicine. Individual readers of this journal, and nonprofit libraries acting for them, are freely permited to make fair use of the material in it, such as to copy an article for use in teaching or research. (For other kinds of copying see "Copying Fees.") Permission is granted to quote from this journal in scientific works with the customary acknowledgment of the source. To reprint a figure, table, or other excerpt requires, in addition, AAPM may require that permission also be obtained from one of the authors. Address inquiries and notices to Penny Slattery, Journal Manager, Medical Physics Journal, AAPM, One Physics Ellipse, College Park, MD 20740-3846; email: journal@aapm.org.

close