A quality assurance phantom for electronic portal imaging devices.

Indra J. Das, Minsong Cao, Chee Wai Cheng, Vladimir Misic, Klaus Scheuring, Edmund Schüle, Peter A S Johnstone

Research output: Contribution to journalArticle

Abstract

Electronic portal imaging device (EPID) plays an important role in radiation therapy portal imaging, geometric and dosimetric verification. Consistent image quality and stable radiation response is necessary for proper utilization that requires routine quality assurance (QA). A commercial 'EPID QC' phantom weighing 3.8 kg with a dimension of 25 × 25 × 4.8 cm3 is used for EPID QA. This device has five essential tools to measure the geometric accuracy, signal-to-noise ratio (SNR), dose linearity, and the low- and the high-contrast resolutions. It is aligned with beam divergence to measure the imaging and geometric parameters in both X and Y directions, and can be used as a baseline check for routine QA. The low-contrast tool consists of a series of holes with various diameters and depths in an aluminum slab, very similar to the Las Vegas phantom. The high-resolution contrast tool provides the modulation transfer function (MTF) in both the x- and y-dimensions to measure the focal spot of linear accelerator that is important for imaging and small field dosimetry. The device is tested in different institutions with various amorphous silicon imagers including Elekta, Siemens and Varian units. Images of the QA phantom were acquired at 95.2 cm source-skin-distance (SSD) in the range 1-15MU for a 26 × 26 cm2 field and phantom surface is set normal to the beam direction when gantry is at 0° and 90°. The epidSoft is a software program provided with the EPID QA phantom for analysis of the data. The preliminary results using the phantom on the tested EPID showed very good low-contrast resolution and high resolution, and an MTF (0.5) in the range of 0.3-0.4 lp/mm. All imagers also exhibit satisfactory geometric accuracy, dose linearity and SNR, and are independent of MU and spatial orientations. The epidSoft maintains an image analysis record and provides a graph of the temporal variations in imaging parameters. In conclusion, this device is simple to use and provides testing on basic and advanced imaging parameters for daily QA on any imager used in clinical practices.

Original languageEnglish
Pages (from-to)3350
Number of pages1
JournalJournal of Applied Clinical Medical Physics
Volume12
Issue number2
StatePublished - 2011

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assurance
Quality assurance
Imaging techniques
Equipment and Supplies
electronics
geometric accuracy
Image sensors
Signal-To-Noise Ratio
modulation transfer function
linearity
Optical transfer function
signal to noise ratios
Signal to noise ratio
gantry cranes
dosage
Particle Accelerators
high resolution
Silicon
linear accelerators
Aluminum

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Das, I. J., Cao, M., Cheng, C. W., Misic, V., Scheuring, K., Schüle, E., & Johnstone, P. A. S. (2011). A quality assurance phantom for electronic portal imaging devices. Journal of Applied Clinical Medical Physics, 12(2), 3350.

A quality assurance phantom for electronic portal imaging devices. / Das, Indra J.; Cao, Minsong; Cheng, Chee Wai; Misic, Vladimir; Scheuring, Klaus; Schüle, Edmund; Johnstone, Peter A S.

In: Journal of Applied Clinical Medical Physics, Vol. 12, No. 2, 2011, p. 3350.

Research output: Contribution to journalArticle

Das, IJ, Cao, M, Cheng, CW, Misic, V, Scheuring, K, Schüle, E & Johnstone, PAS 2011, 'A quality assurance phantom for electronic portal imaging devices.', Journal of Applied Clinical Medical Physics, vol. 12, no. 2, pp. 3350.
Das IJ, Cao M, Cheng CW, Misic V, Scheuring K, Schüle E et al. A quality assurance phantom for electronic portal imaging devices. Journal of Applied Clinical Medical Physics. 2011;12(2):3350.
Das, Indra J. ; Cao, Minsong ; Cheng, Chee Wai ; Misic, Vladimir ; Scheuring, Klaus ; Schüle, Edmund ; Johnstone, Peter A S. / A quality assurance phantom for electronic portal imaging devices. In: Journal of Applied Clinical Medical Physics. 2011 ; Vol. 12, No. 2. pp. 3350.
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