Skip to main content
SpringerLink
Log in

The change of response of ionization chambers in the penumbra and transmission regions: impact for IMRT verification

  • Original Article
  • Published:
Medical & Biological Engineering & Computing Aims and scope Submit manuscript

Abstract

Significant deviations from the expected dose have been reported in the absolute dosimetry validation of an intensity modulated radiation therapy treatment when individual segments are analyzed. However, when full treatment is considered and all segment doses are added together, these discrepancies fade out, leading to overall dose deviations below a 5% action level. This contradictory behavior may be caused by a partial compensation between detector over-responding and under-responding for measurement conditions far from radiation equilibrium. We consider three treatment verification scenarios that may lead to ionization chamber miss-responding, namely: narrow beam irradiation, field penumbra location and multi-leaf collimator transmission contribution. In this work we have analyzed the response of three different ionization chambers with different active volume under these conditions by means of Monte Carlo (MC) simulation methods. Correction factors needed to convert the detector readout into actual dose to water were calculated by inserting the specific detector geometry (carefully modeled) into the simulations. This procedure required extensive use of parallel computing resources in order to achieve the desired level of uncertainty in the final results. The analysis of the simulations shows the relative contribution of each of the three previously mentioned miss-responding scenarios. Additionally, we provide some evidence on dose deviation compensation in multi-segment radiotherapy treatment verification.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8

Similar content being viewed by others

References

  1. Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, Rogers DWO (1999) AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 26:1847–1870

    Article  Google Scholar 

  2. Andreo P, Burns DT, Hohlfeld K, Huq MS, Kanai T, Laitano F, Smyth V and Vynckier S (2000) Absorbed dose determination in external beam radiotherapy: an International Code of Practice for dosimetry based on standards of absorbed dose to water. IAEA technical reports series no 398, International Atomic Energy Agency, Vienna

  3. Bouchard H, Seuntjens J (2004) Ionization chamber-based reference dosimetry of intensity modulated radiation beams. Med Phys 31:2454–2465

    Article  Google Scholar 

  4. Boyer A, Butler EB, DiPetrillo TA, Engler MJ, Fraass B, Grant III W, Clifton Ling C, Low DA, Mackie TR, Mohan R, Purdy JA (Chairman), Roach M, Rosenman JG, Verhey LJ, Wong JW (2001) Intensity-modulated radiotherapy: Current status and issues of interest. Int J Radiat Oncol, Biol, Phys 51:880–914

    Google Scholar 

  5. Cadman P, Bassalow R, Sidhu NPS, Ibbott G, Nelson A (2002) Dosimetric considerations for validation of a sequential IMRT process with a commercial treatment planning system. Phys Med Biol 47:3001–3010

    Article  Google Scholar 

  6. Capote R, Sánchez-Doblado F, Leal A, Lagares JI, Arráns R (2004) An EGSnrc Monte Carlo study of the microionization chamber for reference dosimetry of narrow irregular IMRT beamlets. Med Phys 31:2416–2422

    Article  Google Scholar 

  7. Cilla S, Grimaldi L, D’Onofrio G, Viola P, Craus M, Azario L, Fidanzio A, Stimato G, Di Gesù C, Macchia G, Deodato F, Morganti AG, Piermattei A (2007) Portal dose measurements by a 2D array. Phys Med 23:25–32

    Article  Google Scholar 

  8. Francescon P, Cora S, Cavedon C (1998) Use of a new type of radiochromic film, a new parallel-plate micro-chambers, MOSFETs and TLD 800 microtubes in the dosimetry of small beams. Med Phys 25:503–511

    Article  Google Scholar 

  9. Huang C, Chao C, Perez CA, Low DA (2000) Tumor response and salivary function sparing in patients with oropharyngeal squamous cell carcinoma treated with intensity modulated radiation therapy (IMRT) with/without chemotherapy: the Mallinckrodt Institute of Radiology initial results. Int J Radiat Oncol Biol Phys 48:175–176

    Google Scholar 

  10. Kawrakow I, Rogers DWO, Walters BRB (2004) Large efficiency improvements in BEAMnrc using directional bremsstrahlung splitting. Med Phys 31:2883–2898

    Article  Google Scholar 

  11. Laub WU, Wong T (2003) The volume effect of detectors in the dosimetry of small fields used in IMRT. Med Phys 30:341–347

    Article  Google Scholar 

  12. Leybovich LB, Sethi A, Dogan N (2003) Comparison of ionization chambers of various volumes for IMRT absolute dose verification. Med Phys 30:119–123

    Article  Google Scholar 

  13. Martens C, De Wagter C, De Neve W (2000) The value of the PinPoint ion chamber for characterization of small field segments used in intensity-modulated radiotherapy. Phys Med Biol 45:2519–2530

    Article  Google Scholar 

  14. Nahum AE (1988) Simulation of dosimeter response and interface effects. In: Jenkins TM, Nelson WR, Rindi A (eds)

  15. Pena J, Sánchez-Doblado F, Capote R, Terrón JA, Gómez F (2006) Monte Carlo correction factors for a Farmer 0.6 cm3 ion chamber dose measurement in the build-up region of the 6MV clinical beam. Phys Med Biol 51:1523–1532

    Article  Google Scholar 

  16. Pena J, González-Castaño D, Gómez F, Sánchez-Doblado F, Hartmann GH (2007) Automatic determination of primary electron beam parameters in Monte Carlo simulation. Med Phys 34:1076–1084

    Article  Google Scholar 

  17. Portelance L, Chao KSC, Grigsby PW, Bennet H, Low D (2001) Intensity-modulated radiation therapy (IMRT) reduces small bowel, rectum, and bladder doses in patients with cervical cancer receiving pelvic and para-aortic irradiation. Int J Radiat Oncol Biol Phys 51:261–266

    Google Scholar 

  18. Rogers DWO, Faddegon BA, Ding GX, Ma CA, We J (1995) BEAM: a Monte Carlo code to simulate radiotherapy treatment units. Med Phys 22:503–524

    Article  Google Scholar 

  19. Rogers DWO, Kawrakow I, Seuntjens JP et al (2003) NRC user codes for EGSnrc. NRCC technical report PIRS-702 revB. NRCC, Ottawa

    Google Scholar 

  20. Sánchez-Doblado F, Andreo P, Capote R, Leal A, Perucha M, Arráns R, Núñez L, Mainegra E, Lagares JI, Carrasco E (2003) Ionization chamber dosimetry of small photon fields: a Monte Carlo study on stopping-power ratios for radiosurgery and IMRT beams. Phys Med Biol 48:2081–2099

    Article  Google Scholar 

  21. Sánchez-Doblado F, Capote R, Leal A, Roselló JV, Lagares JI, Arráns R, Hartmann GH (2005a) Microionization chamber for reference dosimetry in IMRT verification: clinical implications on OAR dosimetric errors. Phys Med Biol 50:959–970

    Article  Google Scholar 

  22. Sánchez-Doblado F, Capote R, Roselló JV, Leal A, Lagares JI, Arráns R, Hartmann GH (2005b) Micro ionization chamber dosimetry in IMRT verification: clinical implications of dosimetric errors in the PTV. Radiat Oncol 75:342–348

    Article  Google Scholar 

  23. Sánchez-Doblado F, Hartmann GH, Pena J, Capote R, Paiusco M, Rhein B, Leal A, Lagares JI (2007) Uncertainty estimation in IMRT absolute dosimetry verification. Int J Radiat Oncol Biol Phys 68(1):301–310

    Google Scholar 

  24. Stasi M, Baiotto B, Barboni G, Scielzo G (2004) The behavior of several microionization chambers in small intensity modulated radiotherapy fields. Med Phys 31:2792–2795

    Article  Google Scholar 

  25. Van Dyck J, Barnett RB, Cygler JE, Shragge PC (1993) Comissioning and quality assurance of treatment planning computers. Int J Radiat Oncol Biol Phys 26:261–273

    Google Scholar 

  26. Verhaegen F (2002) Evaluation of the EGSnrc Monte Carlo code for interface dosimetry near high-Z media exposed to kilovolt and 60Co photons. Phys Med Biol 47:1691–1705

    Article  Google Scholar 

  27. Verhaegen F (2003) Interface perturbation effects in high-energy electron beams. Phys Med Biol 48:687–705

    Article  Google Scholar 

  28. Walters BRB, Rogers DWO (2002) NRCC technical report PIRS-794. NRCC, Ottawa

    Google Scholar 

Download references

Acknowledgments

The authors are indebted to the Spanish “Fondo de Investigaciones Sanitarias” (FIS) as well as to the University Law (LOU) contract between the University of Seville and the Andalusian Health Service (SAS) for financial support. Javier Pena wants to acknowledge the Ramón Areces foundation for its financial support. The authors also wish to thank PTW for providing any required geometrical input data of the ionization chambers for the MC simulation.

Author information

Authors and Affiliations

  1. Departamento de Física de Partículas, Universidad de Santiago de Compostela, Santiago de Compostela, Spain

    D. González-Castaño, J. Pena & F. Gómez

  2. Hospital Universitario Virgen Macarena, Radiofísica, Sevilla, Spain

    F. Sánchez-Doblado & A. Leal

  3. Departamento de Fisiología Médica y Biofísica, F.Medicina, Universidad de Sevilla, Sevilla, Spain

    F. Sánchez-Doblado & A. Leal

  4. Deutsches Krebsforschungszentrum, Abt. Medizinische Physik in der Strahlentherapie, Heidelberg, Germany

    G. H. Hartmann

Authors
  1. D. González-Castaño
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. J. Pena
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. F. Sánchez-Doblado
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. G. H. Hartmann
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. F. Gómez
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. A. Leal
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to D. González-Castaño.

Rights and permissions

Reprints and permissions

About this article

Cite this article

González-Castaño, D., Pena, J., Sánchez-Doblado, F. et al. The change of response of ionization chambers in the penumbra and transmission regions: impact for IMRT verification. Med Biol Eng Comput 46, 373–380 (2008). https://doi.org/10.1007/s11517-007-0249-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11517-007-0249-z

Keywords

Search

Navigation