A quality assurance phantom for electronic portal imaging devices

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’...

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Vydáno v:Journal of applied clinical medical physics Ročník 12; číslo 2; s. 391 - 403
Hlavní autoři: Das, Indra J., Cao, Minsong, Cheng, Chee‐Wai, Misic, Vladimir, Scheuring, Klaus, Schüle, Edmund, Johnstone, Peter A.S.
Médium: Journal Article
Jazyk:angličtina
Vydáno: United States John Wiley & Sons, Inc 02.02.2011
John Wiley and Sons Inc
Témata:
Accuracy
Algorithms
Aluminum
Automation
Copper
Dosimetry
EPID
Equipment Design
Humans
imager
Localization
Materials Testing
Models, Statistical
MTF
Particle Accelerators - instrumentation
Phantoms, Imaging
Quality
Quality Control
Radiation Monitoring - methods
Radiation therapy
Radiometry - instrumentation
Radiometry - methods
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted - instrumentation
Radiotherapy Planning, Computer-Assisted - methods
Reproducibility of Results
Sensors
Silicon - chemistry
Software
Technical Notes
Germany
ISSN:1526-9914, 1526-9914
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Popis
Shrnutí: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 1–15 MU 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. PACS number: 87.57 C‐, 87.57 N‐
Bibliografie:ObjectType-Article-1
SourceType-Scholarly Journals-1
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Conflict of Interest statement: Authors KS and ES are employees of the PTW that markets the device.
ISSN:1526-9914
1526-9914
DOI:10.1120/jacmp.v12i2.3350