Dosimetric properties of an amorphous silicon electronic portal imaging device for verification of dynamic intensity modulated radiation therapy

  • Greer P
  • Popescu C
  • 3

    Readers

    Mendeley users who have this article in their library.
  • N/A

    Citations

    Citations of this article.

Abstract

Dosimetric properties of an amorphous silicon electronic portal imaging device (EPID) for verification of dynamic intensity modulated radiation therapy (IMRT) delivery were investigated. The EPID was utilized with continuous frame-averaging during the beam delivery. Properties studied included effect of buildup, dose linearity, field size response, sampling of rapid multileaf collimator (MLC) leaf speeds, response to dose-rate fluctuations, memory effect, and reproducibility. The dependence of response on EPID calibration and a dead time in image frame acquisition occurring every 64 frames were measured. EPID measurements were also compared to ion chamber and film for open and wedged static fields and IMRT fields. The EPID was linear with dose and dose rate, and response to MLC leaf speeds up to 2.5 cm s(-1) was found to be linear. A field size dependent response of up to 5% relative to dmax ion-chamber measurement was found. Reproducibility was within 0.8% (1 standard deviation) for an IMRT delivery recorded at intervals over a period of one month. The dead time in frame acquisition resulted in errors in the EPID that increased with leaf speed and were over 20% for a 1 cm leaf gap moving at 1.0 cm s(-1). The EPID measurements were also found to depend on the input beam profile utilized for EPID flood-field calibration. The EPID shows promise as a device for verification of IMRT, the major limitation currently being due to dead-time in frame acquisition.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

  • P. B. Greer

  • C. C. Popescu

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free