Investigation of Percentage Depth Dose (PDD) and Dose Rate Dependence of PAGAT Polymer Gel Dosimeter for Photon Beams Using MRI Technique

Azadbakht, B; Hadad, K; Zahmatkesh, M.H

Investigation of Percentage Depth Dose (PDD) and Dose Rate Dependence of PAGAT Polymer Gel Dosimeter for Photon Beams Using MRI Technique

Document Type : Research Paper

Authors

B Azadbakht

K Hadad

M.H Zahmatkesh

Abstract

In this work, the investigation of the normoxic PAGAT polymer-gel dosimeter percentage depth dose (PDD) and it’s dose rate dependence has been made. Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2 was determined to be 4.5% N,N'-methylen-bis-acrylamide©(bis), 4.5% acrylamid (AA), 5% gelatine, 5mM tetrakis (hydroxymethyl) phosphonium chloride (THPC), 0.01 mM hydroquinone (HQ) and 86% HPLC(Water). Irradiation of vials was performed using photon beams of Co-60 therapy unit and an Electa linear accelerator. Gel dosimeters were imaged in a Siemens Symphony 1.5 Tesla clinical MRI scanner using a head coil. Post-manufacture irradiation and post imaging times were both selected to be 1 day. For determing the percentage depth dose of the PAGAT gel it was found that at the depth of 21cm, the percentage depth dose for 1.25 MeV γ-ray photons of ⁶⁰Co and for 4,6 and 18 MV x-ray photons of Electa linear accelerator, are 48%, 52%, 57.3% and 59.73%, respectively. Thus, in the case of the higher energy photon beams, a higher dose can be delivered to deep-seated tumors. The dose rate dependence of PDD was studied for 6 MV x-ray photons with the use of dose rates of 80, 160, 240, 320, 400 and 480cGy/min. No trend in polymer-gel dosimeter 1/T2 dependence was found on the mean dose rate and energy for the photon beams.

Highlights

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5. M.H. Zahmatkesh, R. Kousari, Sh. Akhlaghpour, S.A. Bagheri, “MRI gel dosimetry with methacrylic acid. Ascorbic acid. Hydroquinone and Copper in Aharose (MAGICA) gel,” Preliminary Proceedinges of DOSGEL. Sep. 13-16, Ghent. Belgium (2004).

6. Y. De Deen, N. Reynaert, C. De Wagter, “On the accuracy of monomer/polymer gel dosimetry in the proximity of high-dose-rate Ir192source,” Phys. Med Biol. 46, 2801-2825 (2001).

7. A.J. Venning, B. Hill, S. Brindha, B.J. Healy, C. Baldock, “Investigation of the PAGAT polymer gel dosimeter using magnetic resonance imaging,” Phys. Med. Biol. 50, 3875-3888 (2005).

8. B. Hill, A. Venning, C. Baldock, “The dose response of normoxic polymer gel dosimeters measured using X-ray CT,” The British Journal of Radiology, 78, 623-630 (2005).

9. J. Novontny, V. Spevacek, P. Dvorak, T. Cechak, “Energy and dose rate dependence of BANG-2 polymer-gel dosimeter,” Med. Phys. 28, 0094-2405 (2001).

10. E. Pappas, A. Angelopoulos, P. Kipouros, L. Vlachos, S. Xenofos, I. Seimenis, “Evaluation of the performance of VIPAR polymer gels,” Med. Phys. Biol. 48, N65-N73 (2003).

11. M.J. Maryanski, G.S. Ibbott, P. Estman, R.J. Schulz, J.C. Gore, “Radiation therapy dosimetry using magnetic resonance imaging of polymer gels,” Med. Phys. 23, 699-705 (1996).

1. M. Oldham, S. Kumar, J. Wong, D.A. Jaeffray, “Optical-CT gel-dosimetry I:Basic investigation,” Med. phys. 30(4), 623-634 (April 2003).

2. E.B. Podgorsak, [Editor of] “Radiation oncology physics: a handbook for teachers and students,” ISBN. 92-0-107304-6, International Atomic Energy Agency (IAEA), Austria (2005).

3. K. Vergote, “Development of polymer gel dosimetry for applications in intensity-modulated radiotherapy,” PhD. Thesis. Department of Radiotherapy and Nuclear Medicine, Faculty of Medicine and Health Sciences, University of Gent, Belgum (2005).

4. A.J. Venning, S. Brindha, B. Hill, C. Baldock, “Preliminary study of a normoxic PAG gel dosimeter with tetrakis (hydroxymethyl) phosphonium chloride as an antioxidant,” Third International Conference on Radiotherapy Gel Dosimetry. Journal of Physics: Conference Series, 155-158, 3(2004).

5. M.H. Zahmatkesh, R. Kousari, Sh. Akhlaghpour, S.A. Bagheri, “MRI gel dosimetry with methacrylic acid. Ascorbic acid. Hydroquinone and Copper in Aharose (MAGICA) gel,” Preliminary Proceedinges of DOSGEL. Sep. 13-16, Ghent. Belgium (2004).

6. Y. De Deen, N. Reynaert, C. De Wagter, “On the accuracy of monomer/polymer gel dosimetry in the proximity of high-dose-rate Ir192source,” Phys. Med Biol. 46, 2801-2825 (2001).

7. A.J. Venning, B. Hill, S. Brindha, B.J. Healy, C. Baldock, “Investigation of the PAGAT polymer gel dosimeter using magnetic resonance imaging,” Phys. Med. Biol. 50, 3875-3888 (2005).

8. B. Hill, A. Venning, C. Baldock, “The dose response of normoxic polymer gel dosimeters measured using X-ray CT,” The British Journal of Radiology, 78, 623-630 (2005).

9. J. Novontny, V. Spevacek, P. Dvorak, T. Cechak, “Energy and dose rate dependence of BANG-2 polymer-gel dosimeter,” Med. Phys. 28, 0094-2405 (2001).

10. E. Pappas, A. Angelopoulos, P. Kipouros, L. Vlachos, S. Xenofos, I. Seimenis, “Evaluation of the performance of VIPAR polymer gels,” Med. Phys. Biol. 48, N65-N73 (2003).

11. M.J. Maryanski, G.S. Ibbott, P. Estman, R.J. Schulz, J.C. Gore, “Radiation therapy dosimetry using magnetic resonance imaging of polymer gels,” Med. Phys. 23, 699-705 (1996).