TY - JOUR
T1 - A quality assurance phantom for electronic portal imaging devices
AU - Das, Indra J.
AU - Cao, Minsong
AU - Cheng, Chee Wai
AU - Misic, Vladimir
AU - Scheuring, Klaus
AU - Schüle, Edmund
AU - Johnstone, Peter A.S.
PY - 2011
Y1 - 2011
N2 - 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 3.8kg 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.
AB - 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 3.8kg 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.
KW - EPID
KW - Imager
KW - MTF
KW - QA
UR - https://www.scopus.com/pages/publications/79960509867
UR - https://www.scopus.com/inward/citedby.url?scp=79960509867&partnerID=8YFLogxK
U2 - 10.1120/jacmp.v12i2.3350
DO - 10.1120/jacmp.v12i2.3350
M3 - Article
C2 - 21587179
AN - SCOPUS:79960509867
SN - 1526-9914
VL - 12
SP - 391
EP - 403
JO - Journal of Applied Clinical Medical Physics
JF - Journal of Applied Clinical Medical Physics
IS - 2
ER -