Dose-to-medium vs. dose-to-water: Dosimetric evaluation of head and neck VMAT cases using Monaco treatment planning system
Purpose: In this paper, we evaluate the dosimetric differences between absorbed dose to water and absorbed dose to medium in Monte Carlo (MC)-based calculations used for radiation therapy treatment plans.
Methods: Thirty-four treated Head and Neck simultaneously integrated boost cases were analyzed retrospectively. All of them were planned by Monaco treatment planning system (TPS), calculated and reviewed on absorbed dose to medium (Dm) calculations and treated in Elekta Versa HD LINAC. Absorbed dose to medium Dm was converted to absorbed dose to water Dw in Monaco treatment planning system using the procedure based on stopping power ratios and the Bragg-Gray cavity theory. Dosimetric parameters were then compared and analyzed with respect to absorbed dose to medium (Dm) calculations for multiple planning target volumes (PTVs) and critical organs such as brainstem, spinal cord, left and right lens, left and right parotids, larynx, left and right middle ear and lips.
Results: It was found that mean and minimum Dw (i.e. Dw mean and Dw min) of organs at risk did not differ much (hardly differing by 0.8-2%) with respect to those of the absorbed dose to medium. However maximum Dw (i.e. Dw max) in case of lips, left and right middle ear were found to differ more than 4% with respect to Dm max. For serial organs brainstem and spinal cord, maximum dose Dw max were found to vary around 1% and 2%, respectively, with respect to absorbed dose to medium dose calculation. In case of PTVs, the mean percentages variation of Dw min and Dw mean were found to be less than 1 %, although the variation of maximum Dw was found to be high around 5-7% with respect to that of Dm.
Conclusion: The comparative analysis of dosimetric parameters in the present study shows that the selection of either Dm or Dw in Monaco planning system is less likely to produce any significant clinical effect in tumor control and to the damage of organs at risk.
Indrin JC, Curran B, Cygler JE, et al. Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning. Med Phys. 2007;34(12):4818–53.
Rogers DWO, Bielajew AF, Kase DK, et al. Monte Carlo techniques of electrons and photons for radiation dosimetry. Dosimetry of Ionizing Radiation. 3rd ed. New York: Academic;1990:427–539.
Mackie TR, Kase DK, Bjarngard BE, et al. Applications of the Monte Carlo method in radiotherapy. Dosimetry of Ionizing Radiation. 3rded. New York: Academic;1990:541–620
Andreo P. Monte Carlo techniques in medical radiation physics. Phys MedBiol. 1991;36:861–920.
Ma CM, Jiang SB. Monte Carlo modelling of electron beams from medical accelerators. Phys Med Biol. 1999;44R:157–89.
Verhaegen F, Devic S. Sensitivity study for CT image use in Monte Carlo treatment planning. Phys Med Biol. 2005;50:937–46.
Reynaert N. Monte Carlo treatment planning for photon and electron beams. Radiat Phys Chem. 2007;76:643–86.
Siebers JV, Keall PJ, Nahum AE, et al. Converting absorbed dose to medium to absorbed dose to water for Monte Carlo based photon beam dose calculations. Phys Med Biol. 2000;45:983-95.
Huq MS, Andreo P, Song H. Comparison of the IAEA TRS-398 and AAPM TG-51 absorbed dose to water protocols in the dosimetry of high-energy photon and electron beams. Phys MedBiol. 2001;46(11):2985-3006.
Solberg TD, DeMarco JJ, Holly FE, et al. Monte Carlo treatment planning for stereotactic radiosurgery. Radiother Oncol. 1998;49(1) :73-84.
Li JS, Freedman GM, Price R, et al. Clinical implementation of intensity-modulated tangential beam irradiation for breast cancer. MedPhys. 2004:31(5):1023-31.
Jin L, Wang L, Li J, et al. Investigation of optimal beam margins for stereotactic radiotherapy of lung-cancer using monte carlo dose calculations. Phys Med Biol. 2007;52(12): 3549-61.
Sterpin E, Salvat F, Cravens R, et al. Monte Carlo simulation of helical tomotherapywith PENELOPE. Phys Med Biol. 2008;53(12): 2161-80.
Bush K, Townson R, Zavgorodni S. Monte Carlo simulation of RapidArc radiotherapy delivery. Phys Med Biol. 2008;53(19):N359-N70.
Siebers JV, Keall PJ, Kim JO, et al. A method for photon beam monte carlomultileaf collimator particle transport. Phys Med Biol. 2002;47(17):3225-49.
Du Plessis FC, Willemse CA, Lötter MG, et al. The indirect use of ct numbers to establish material properties needed for monte carlo calculation of dose distributions in patients. Med Phys. 1998;25(7):1195-201.
Fippel M, Nüsslin F. Comments on ‘Converting absorbed dose to medium to absorbed dose to water for monte carlo based photon beam dose calculations’. Phys Med Biol. 2007;45(8):L17-9.
Liu HH, Keall P. Dm Rather than Dwshould be used in Monte Carlo treatment planning. For the Proposition. Med Phys. 2002;29(5):922-3.
Usmani MN, Masai N, Oh RJ, et al. Comparison of absorbed dose to medium and absorbed dose to water for spine IMRT plans using a commercial Monte Carlo treatment planning system. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology. 2014;3:60-66.
Rana S, Pokharel S. Dose-to-medium vs. dose-to-water: Dosimetric evaluation of dose reporting modes in Acuros XB for prostate, lung and breast cancer. Int J Cancer Ther Oncol. 2014;2(4):020421.
Dogan N, Siebers JV, Keall PJ. Clinical comparison of head and neck and prostate IMRT plans using absorbed dose to medium and absorbed dose to water. Phys Med Biol. 2006;51(19):4967-80.
Monaco Training Guide, IMPAC Medical Systems, Inc. Document ID: LTGMON0500
Almond PR, Biggs PJ, Coursey BM, et al. AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys. 1999;26(9):1847-70.
Ma CM, Li JS. Dose specification for radiation therapy: dose to water or dose to medium. Phys Med Biol. 2011;56(10)3073-90.
Walters BR, Kramer R, Kawrakow I. Dose to Medium versus Dose to Water as an estimator of dose to sensitive skeletal tissue. Phys Med Biol. 2010:55(16):4535-46.
This work is licensed under a Creative Commons Attribution 3.0 License.
International Journal of Cancer Therapy and Oncology (ISSN 2330-4049)
© International Journal of Cancer Therapy and Oncology (IJCTO)
To make sure that you can receive messages from us, please add the 'ijcto.org' domain to your e-mail 'safe list'. If you do not receive e-mail in your 'inbox', check your 'bulk mail' or 'junk mail' folders.