Verification of dosimetric materials to be used as tissue-substitutes in radiological diagnosis Kulwinder Singh Mann a,n , Murat Kurudirek b , G.S. Sidhu c a Department of Physics, Dravidian University, Kuppam-517425, A.P., India b Department of Physics, Ataturk University, 25240 Erzurum, Turkey c Department of Physics, G.S.S.S., Jodhpur-Romana, Bathinda-151001, India article info Article history: Received 19 September 2011 Received in revised form 24 November 2011 Accepted 3 December 2011 Available online 13 December 2011 Keywords: Mass energy absorption coefficient Equivalent atomic number Tissue equivalence KERMA Phantoms abstract Dosimetric materials have been investigated in terms of calculated mass energy absorption coefficient, equivalent atomic number and KERMA (kinetic energy released per unit mass) in the energy range 0.015–15 MeV. Using analytical methodology it has verified that nylon is the best substitute dosimetric material for skin, muscle, bone and soft-tissues. Relative energy absorption buildup factors calculated by G-P fitting method confirm the findings. Nylon has been found to be good tissue substitute material for making tissue-phantoms of the biological tissues investigated. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction In the biological and medical context, study of interaction of gamma ray photon is of importance in the calculation of radiation dose received by the biological molecules in addition to the importance of knowledge on other photon interaction parameters such as mass attenuation coefficients, KERMA, equivalent atomic numbers and effective atomic numbers in biological tissues such as skin, muscle, bone and soft-tissues. The photons in the keV range are important in radiation biology as well as in medical diagnostics and therapy, the photons in the MeV range are vital for radiography and medical imaging. Various materials have been used to simulate human-tissues to study effective radiation dose received by patients exposed to the ionizing radiations. These materials are commonly named as tissue-equivalent mate- rials (Kienb ¨ och, 1906; Jones et al., 2003). The International Commission on Radiation Units and Measurements compiled and published in report 44, the results of various studies on the utilization of tissue-equivalent materials to be used in dosimetry for diagnostic radiology and radiotherapy applications (ICRU, 1989). The report presents the total mass attenuation coefficients and the mass energy absorption coefficient (m en /r) in the energy range from 1 keV to 50 MeV, as well as elemental compositions of tissue-equivalent materials and of human-tissues. In the photon energy interval from 0.015 to 15 MeV, the main interaction processes of photons with matter are the photoelectric effect, Compton scattering and pair production. Thus, total mass attenuation coefficient and mass energy absorption coefficient depend only on the mentioned processes. These quantities can be calculated using the photon energy, the mixture rule and the elemental composition of the material by WinXCom a computer program initially developed as XCOM (Berger et al., 1999). The behaviour of the dosimetric material to incident photons can be studied in terms of mass energy absorption coefficient (m en /r), equivalent atomic number (Z eq ) and KERMA (kinetic energy released per unit mass). In order to get the detailed study of scattering effect of the incident photon the equivalent atomic number of the sample is a useful parameter. Equivalent atomic numbers of dosimetric material cannot be found in any standard database, but they are necessary for many applications in radi- ological diagnostics. In the present work, we have applied the interpolation formula of Sidhu et al. (1999) for the calculations of equivalent atomic numbers for Dosimetric materials and human- tissues. The generated data on equivalent atomic numbers have been compared with that of tissues in the selected energy range 0.015–15 MeV. The analytical methodology used is a reasonable and effective way for evaluating the applications of the selected materials as substitute of human tissue phantoms. Mostly acrylic (PMMA; polymethyl methacrylate) has been used as the tissue-equivalent material in dosimetry for diagnostic Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes 0969-8043/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2011.12.008 Abbreviations: Z eq , Equivalent atomic number; Z eff , Effective atomic number; KERMA, Kinetic energy released per unit mass; EABF, Energy absorption buildup factor. n Corresponding author. Tel.: þ919417325696; fax: þ911642214666. E-mail address: ksmann6268@gmail.com (K.S. Mann). Applied Radiation and Isotopes 70 (2012) 681–691