Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-26T17:13:45.729Z Has data issue: false hasContentIssue false
  • English
  • Français

Dosimetric properties of fluoroscopic EPID for transit dosimetry

Published online by Cambridge University Press:  30 October 2014

Akbar Anvari ,
Seyed Mahmoud Reza Aghamiri ,
Seyed Rabi Mahdavi ,
Parham Alaei  and
Mohammad Mohammadi
Akbar Anvari*
Affiliation:
Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran, Iran
Seyed Mahmoud Reza Aghamiri
Affiliation:
Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran, Iran
Seyed Rabi Mahdavi
Affiliation:
Department of Medical Physics, Iran University of Medical Sciences, Tehran, Iran
Parham Alaei
Affiliation:
Department of Radiation Oncology, University of Minnesota, Minneapolis, Minnesota, USA
Mohammad Mohammadi
Affiliation:
Department of Medical Physics, Royal Adelaide Hospital, Adelaide, SA, Australia
*
Correspondence to: Akbar Anvari, Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran 19839-63113, Iran. Tel: +98 9196260656. E-mail: A_Anvari@sbu.ac.ir
Get access Rights & Permissions [Opens in a new window]

Abstract

The aim of this work was to evaluate dose response of fluoroscopic EPID for transit dosimetry applications. Properties studied included warm up time, build-up thickness evaluation, dose history, linearity, stability, and short and long-term reproducibility of EPID response, as well as field size dependence.

Pixel value matrices of electronic portal images in DICOM format were analysed in central and 8 off axis points using customised written codes in Matlab. In order to do this, nine 26×26 pixel matrices were selected as regions of interest, the regions represented by these arrays were 1×1 and 0·65×0·65 cm2 at the EPID and isocentre level, respectively.

Necessary warm up time for stable operation of EPID is 30 minutes, and there is no need for extra build-up layer to increase the dose response. Linearity tests indicate charged coupled device camera of EPID saturates at 50 cGy level, and does not have linear relationship with dose. Reproducibility and stability of the measurements were excellent and the detector showed same signal with a maximum deviation of <0·3% both in short and long terms. Results of dosimetric evaluation have shown the TheraView fluoroscopic EPID can be used for transit dosimetry purposes.

Keywords

dose responsedosimetryepidportal imaging
Type
Original Articles
Information
Journal of Radiotherapy in Practice , Volume 14 , Issue 1 , March 2015 , pp. 27 - 34
Check for updates
Copyright
© Cambridge University Press 2014 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1.Van Esch, A, Depuydt, T, Huyskens, D P. The use of an aSi-based EPID for routine absolute dosimetric pre-treatment verification of dynamic IMRT fields. Radiother Oncol 2004; 71 (2): 223–234.Google Scholar
2.Essers, M, Hoogervorst, B R, van Herk, Met al. Dosimetric characteristics of a liquid-filled electronic portal imaging device. Int J Radiat Oncol Biol Phys 1995; 33 (5): 1265–1272.Google Scholar
3.Greer, P B, Popescu, C C. Dosimetric properties of an amorphous silicon electronic portal imaging device for verification of dynamic intensity modulated radiation therapy. Med Phys 2003; 30 (7): 1618–1627.Google Scholar
4.De Boer, J, Heijmen, B, Pasma, Ket al. Characterization of a high-elbow, fluoroscopic electronic portal imaging device for portal dosimetry. Phys Med Biol 2000; 45 (1): 197.Google Scholar
5.van Elmpt, W, McDermott, L, Nijsten, Set al. A literature review of electronic portal imaging for radiotherapy dosimetry. Radiother Oncol 2008; 88 (3): 289–309.Google Scholar
6.Chatelain, C, Vetterli, D, Henzen, Det al. Dosimetric properties of an amorphous silicon EPID for verification of modulated electron radiotherapy. Med Phys 2013; 40 (6): 061710.Google Scholar
7.Francois, P, Boissard, P, Berger, Let al. In vivo dose verification from back projection of a transit dose measurement on the central axis of photon beams. Physica Medica 2011; 27 (1): 1–10.CrossRefGoogle ScholarPubMed
8.Sabet, M, Menk, F W, Greer, P B. Evaluation of an a-Si EPID in direct detection configuration as a water-equivalent dosimeter for transit dosimetry. Med Phys 2010; 37 (4): 1459–1467.Google Scholar
9.Mohammadi, M, Bezak, E. Two-dimensional transmitted dose measurements using a scanning liquid ionization chamber EPID. Phys Med Biol 2006; 51 (11): 2971.Google Scholar
10.Franken, E, De Boer, J, Heijmen, B. A novel approach to accurate portal dosimetry using CCD-camera based EPIDs. Med Phys 2006; 33 (4): 888–903.Google Scholar
11.Franken, E, De Boer, J, Barnhoorn, Jet al. Characteristics relevant to portal dosimetry of a cooled CCD camera-based EPID. Med Phys 2004; 31 (9): 2549–2551.Google Scholar
12.de Boer, J, Barnhoorn, J, Heijmen, B. The CCD-camera based electronic portal imaging device (EPID) revisited; Can a-Si flat panel EPIDs do better? Radiother Oncol 2002; 64: S12.Google Scholar
13.Pasma, K, Kroonwijk, M, De Boer, Jet al. Accurate portal dose measurement with a fluoroscopic electronic portal imaging device (EPID) for open and wedged beams and dynamic multileaf collimation. Phys Med Biol 1998; 43 (8): 2047.Google Scholar
14.Pasma, K L, Dirkx, M L, Kroonwijk, Met al. Dosimetric verification of intensity modulated beams produced with dynamic multileaf collimation using an electronic portal imaging device. Med Phys 1999; 26 (11): 2373–2378.Google Scholar
15.Odero, D, Shimm, D. Third party EPID with IGRT capability retrofitted onto an existing medical linear accelerator. Biomed Imaging Interv J 2009; 5 (3): e25.Google Scholar
16.Mohammadi, M, Bezak, E. The physical characteristics of a SLIC-EPID for transmitted dosimetry. Iran J Radiat Res 2005; 2 (4): 175–183.Google Scholar
17.Andreo, P, Burns, D T, Hohlfeld, Ket al. Absorbed dose determination in external beam radiotherapy: an international code of practice for dosimetry based on standards of absorbed dose to water, Technical Report Series No. 398, IAEA, Vienna, Austria, 2000.Google Scholar
18.Ali, A S, Dirkx, M L, Cools, R Met al. Accurate IMRT fluence verification for prostate cancer patients using ‘in-vivo’ measured EPID images and in-room acquired kilovoltage cone-beam CT scans. Radiat Oncol 2013; 8 (1): 211.Google Scholar
19.McDermott, L, Nijsten, S, Sonke, J-Jet al.Comparison of ghosting effects for three commercial a-Si EPIDs. Med Phys 2006; 33 (7): 2448–2451.Google Scholar
20.Winkler, P, Hefner, A, Georg, D. Dose-response characteristics of an amorphous silicon EPID. Med Phys 2005; 32 (10): 3095–3105.Google Scholar
21.Nijsten, S, Van Elmpt, W, Jacobs, Met al. A global calibration model for a‐Si EPIDs used for transit dosimetry. Med Phys 2007; 34 (10): 3872–3884.Google Scholar