Document Type: Original Research


1 PhD, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran

2 PhD, Department of Medical Physics, Royal Adelaide Hospital, Adelaide, SA 5000, Australia

3 PhD, School of Physical Sciences, University of Adelaide, Adelaide, SA 5005, Australia

4 MSc, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran

5 MD, Cancer Research Center, Mashhad University of medical Science, Mashhad, Iran

6 MSc, Department of Radiology, School of Paramedical Sciences, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran

7 PhD, Nuclear Medicine Research Center, Mashhad University of medical Science, Mashhad, Iran



Background: The present study aimed to introduce a rapid transmission dosimetry through an electronic portal-imaging device (EPID) to achieve two-dimensional (2D) dose distribution for homogenous environments.
Material and Methods: In this Phantom study, first, the EPID calibration curve and correction coefficients for field size were obtained from EPID and ionization chamber. Second, the EPID off-axis pixel response was measured, and the grey-scale image of the EPID was converted into portal dose image using the calibration curve. Next, the scattering contribution was calculated to obtain the primary dose. Then, by means of a verified back-projection algorithm and the Scatter-to-Primary dose ratio, a 2D dose distribution at the mid-plane was obtained.
Results: The results obtained from comparing the transmitted EPID dosimetry to the calculated dose, using commercial treatment planning system with gamma function while there is 3% dose difference and 3mm distance to agreement criteria, were in a good agreement. In addition, the pass rates of γ < 1 was 94.89% for the homogeneous volumes.
Conclusion: Based on the results, the method proposed can be used in EPID dosimetry.


  1. Van Elmpt W, McDermott L, Nijsten S, Wendling M, Lambin P, Mijnheer B. A literature review of electronic portal imaging for radiotherapy dosimetry. Radiother Oncol. 2008;88:289-309. doi: 10.1016/j.radonc.2008.07.008. PubMed PMID: 18706727.
  2. Mohammadi M, Bezak E. Two-dimensional transmitted dose measurements using a scanning liquid ionization chamber EPID. Phys Med Biol. 2006;51:2971-85. doi: 10.1088/0031-9155/51/11/019. PubMed PMID: 16723778.
  3. Mohammadi M, Bezak E. Evaluation of MLC leaf positioning using a scanning liquid ionization chamber EPID. Phys Med Biol. 2007;52:N21-33. doi: 10.1088/0031-9155/52/1/N03. PubMed PMID: 17183123.
  4. Chen J, Chuang CF, Morin O, Aubin M, Pouliot J. Calibration of an amorphous-silicon flat panel portal imager for exit-beam dosimetry. Med Phys. 2006;33:584-94. doi: 10.1118/1.2168294. PubMed PMID: 16878562.
  5. Nicolini G, Fogliata A, Vanetti E, Clivio A, Cozzi L. GLAaS: an absolute dose calibration algorithm for an amorphous silicon portal imager. Applications to IMRT verifications. Med Phys. 2006;33:2839-51. doi: 10.1118/1.2218314. PubMed PMID: 16964860.
  6. Nijsten SM, Van Elmpt WJ, Jacobs M, Mijnheer BJ, Dekker AL, Lambin P, et al. A global calibration model for a-Si EPIDs used for transit dosimetry. Med Phys. 2007;34:3872-84. doi: 10.1118/1.2776244. PubMed PMID: 17985633.
  7. Louwe RJ, McDermott LN, Sonke JJ, Tielenburg R, Wendling M, Van Herk M, et al. The long-term stability of amorphous silicon flat panel imaging devices for dosimetry purposes: Stability of EPID response. Med Phys. 2004;31:2989-95. doi: 10.1118/1.1803751.
  8. McDermott LN, Wendling M, Van Asselen B, Stroom J, Sonke JJ, Van Herk M, et al. Clinical experience with EPID dosimetry for prostate IMRT pre-treatment dose verification. Med Phys. 2006;33:3921-30. doi: 10.1118/1.2230810. PubMed PMID: 17089854.
  9. McDermott LN, Louwe RJ, Sonke JJ, Van Herk MB, Mijnheer BJ. Dose-response and ghosting effects of an amorphous silicon electronic portal imaging device. Med Phys. 2004;31:285-95. doi: 10.1118/1.1637969. PubMed PMID: 15000614.
  10. Winkler P, Hefner A, Georg D. Dose-response characteristics of an amorphous silicon EPID. Med Phys. 2005;32:3095-105. doi: 10.1118/1.2040711. PubMed PMID: 16279061.
  11. Mijnheer B, Beddar S, Izewska J, Reft C. In vivo dosimetry in external beam radiotherapy. Med Phys. 2013;40:070903. doi: 10.1118/1.4811216. PubMed PMID: 23822404.
  12. Essers M, Mijnheer BJ. In vivo dosimetry during external photon beam radiotherapy. Int J Radiat Oncol Biol Phys. 1999;43:245-59. doi: 10.1016/s0360- 3016(98)00341-1.PubMed PMID: 10030247.
  13. Tan YI, Metwaly M, Glegg M, Baggarley SP, Elliott A. A dual two dimensional electronic portal imaging device transit dosimetry model based on an empirical quadratic formalism. Br J Radiol. 2015;88:20140645. doi: 10.1259/bjr.20140645. PubMed PMID: 25969867; PubMed Central PMCID: PMC4628518.
  14. Pecharroman-Gallego R, Mans A, Sonke JJ, Stroom JC, Olaciregui-Ruiz I, Van Herk M, et al. Simplifying EPID dosimetry for IMRT treatment verification. Med Physs. 2011;38:983-92. doi: 10.1118/1.3547714. PubMed PMID: 21452735.
  15. Heijmen BJ, Pasma KL, Kroonwijk M, Althof VG, de Boer JC, Visser AG, et al. Portal dose measurement in radiotherapy using an electronic portal imaging device (EPID). Phys Med Biol. 1995;40:1943-55. doi: 10.1088/0031-9155. PubMed PMID: 8587942.
  16. McCurdy BM, Pistorius S. A two-step algorithm for predicting portal dose images in arbitrary detectors. Med Phys. 2000;27:2109-16. doi: 10.1118/1.1289375. PubMed PMID: 11011740.
  17. Pasma KL, Kroonwijk M, De Boer JC, Visser AG, Heijmen BJ. 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;43:2047-60. doi: 10.1088/0031-9155/43/8/004. PubMed PMID: 9725588.
  18. Pasma KL, Kroonwijk M, De Boer JC, Visser AG, Heijmen BJ. 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;43:2047-60. PubMed PMID: 9725588.
  19. Boellaard R, Essers M, Van Herk M, Mijnheer BJ. New method to obtain the midplane dose using portal in vivo dosimetry. Int J Radiat Oncol Biol Phys. 1998;41:465-74. doi: 10.1016/s0360-3016(98)00048-0 .PubMed PMID: 9607366.
  20. Wendling M, McDermott LN, Mans A, Sonke JJ, Van Herk M, Mijnheer BJ. A simple backprojection algorithm for 3D in vivo EPID dosimetry of IMRT treatments. Med Phys. 2009;36:3310-21. doi: 10.1118/1.3148482. PubMed PMID: 19673227.
  21. Baek TS, Chung EJ, Son J, Yoon M. Feasibility study on the verification of actual beam delivery in a treatment room using EPID transit dosimetry. Radiat Oncol. 2014;9:273. doi: 10.1186/s13014-014-0273-8. PubMed PMID: 25472838; PubMed Central PMCID: PMC4262986.
  22. IviewGT E. Corrective maintenance manual. Elekta Limited. 2006.
  23. Cilla S, Azario L, Greco F, Fidanzio A, Porcelli A, Grusio M, et al. An in-vivo dosimetry procedure for Elekta step and shoot IMRT. Phys Med. 2014;30:419-26. doi: 10.1016/j.ejmp.2013.11.005. PubMed PMID: 24361278.
  24. Deshpande S, Xing A, Holloway L, Metcalfe P, Vial P. Dose calibration of EPIDs for segmented IMRT dosimetry. J Appl Clin Med Phys. 2014;15:4895. doi: 10.1120/jacmp.v15i6.4895. PubMed PMID: 25493513; PubMed Central PMCID: PMC5711103.
  25. Bjarngard BE, Shackford H. Attenuation in high-energy x-ray beams. Med Phys. 1994;21:1069-73. doi: 10.1118/1.597349. PubMed PMID: 7968838.
  26. Wang KK, Zhu TC. Modeling scatter-to-primary dose ratio for megavoltage photon beams. Med Phys. 2010;37:5270-8. doi: 10.1118/1.3480480. PubMed PMID: 21089761.
  27. Tan YI, Metwaly M, Glegg M, Baggarley S, Elliott A. Evaluation of six TPS algorithms in computing entrance and exit doses. J Appl Clin Med Phys. 2014;15:229-40. doi: 10.1120/jacmp.v15i3.4739. PubMed PMID: 24892349; PubMed Central PMCID: PMC5711058.
  28. Golestani A, Houshyari M, Mostaar A, Arfaie AJ. Evaluation of dose calculation algorithms of Isogray treatment planning system using measurement in heterogeneous phantom. Reports of Radiotherapy and Oncology. 2015;2(3): e5320. doi: 10.17795/rro-5320.
  29. Mhatre V, Pilakkal S, Chadha P, Talpatra K. Dosimetric Comparison of a-Si 1200 and a-Si 1000 Electronic Portal Imager for Intensity Modulated Radiation Therapy (IMRT). J Nucl Med Radiat Ther. 2018;9:2. doi: 10.4172/2155-9619.1000354.
  30. Camilleri J, Mazurier J, Franck D, Dudouet P, Latorzeff I, Franceries X. 2D EPID dose calibration for pretreatment quality control of conformal and IMRT fields: A simple and fast convolution approach. Phys Med. 2016;32:133-40. doi: 10.1016/j.ejmp.2015.10.094. PubMed PMID: 26573130.
  31. Grządziel A, Smolińska B, Rutkowski R, Ślosarek K. EPID dosimetry–configuration and pre-treatment IMRT verification. Reports of Practical Oncology & Radiotherapy. 2007;12:307-12. doi: 10.1016/s1507-1367(10)60069-7.
  32. Renner WD, Norton K, Holmes T. A method for deconvolution of integrated electronic portal images to obtain incident fluence for dose reconstruction. J Appl Clin Med Phys. 2005;6:22-39. doi: 10.1120/jacmp.2026.25359. PubMed PMID: 16421498; PubMed Central PMCID: PMC5723452.
  33. Greer PB. Off-axis dose response characteristics of an amorphous silicon electronic portal imaging device. Med Phys. 2007;34:3815-24. doi: 10.1118/1.2779944. PubMed PMID: 17985627.
  34. Olaciregui-Ruiz I, Rozendaal R, Mijnheer B, Van Herk M, Mans A. Automatic in vivo portal dosimetry of all treatments. Phys Med Biol. 2013;58:8253-64. doi: 10.1088/0031-9155/58/22/8253. PubMed PMID: 24201085.
  35. Parent L, Fielding AL, Dance DR, Seco J, Evans PM. Amorphous silicon EPID calibration for dosimetric applications: comparison of a method based on Monte Carlo prediction of response with existing techniques. Phys Med Biol. 2007;52:3351-68. doi: 10.1088/0031-9155/52/12/003. PubMed PMID: 17664548.
  36. Kydonieos M, Folgueras A, Florescu L, Cybulski T, Marinos N, Thompson G, et al. TH-AB-201-10: Portal Dosimetry with Elekta IViewDose: Performance of the Simplified Commissioning Approach Versus Full Commissioning. Med Phys. 2016;43:3851. doi: 10.1118/1.4958039.
  37. Mohammadi M, Bezak E. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device. J Med Phys. 2012;37:14-26. doi: 10.4103/0971-6203.92716. PubMed PMID: 22363108; PubMed Central PMCID: PMC3283912.
  38. Mohammadi M, Bezak E, Reich P. Verification of dose delivery for a prostate sIMRT treatment using a SLIC-EPID. Appl Radiat Isot. 2008;66:1930-8. doi: 10.1016/j.apradiso.2008.04.024. PubMed PMID: 18583141.
  39. Kavuma A, Glegg M, Metwaly M, Currie G, Elliott A. A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device. Phys Med Biol. 2010;55:435-52. doi: 10.1088/0031-9155/55/2/007. PubMed PMID: 20019398.