氚(3H)在生物圈內是普遍存在的一種核種，因為氚可以藉由水循環來快速地傳遞到各個地方，加上氚可以經由許多的途徑進入人體內，例如：呼吸、喝水、飲食及皮膚吸收等等，所以必須要了解氚在人體內新陳代謝的途徑與分佈的情形，並進一步探討氚可能造成的生物效應，但因為跟其他核種相較下，氚由貝他衰變所釋放出來的能量(平均5.7 keV)是比較小的，因此很多輻射防護組織把氚歸類成最弱的核種內，可是隨著對氚的特性越來越了解，造成現在許多研究證據證明氚對人體造成的傷害是不可被輕視的。其中由於氚釋放的能量比較小，導致氚在人體內分佈與輻射敏感區之間的相互位置變得很重要，而氚值得注意的地方是它在人體內不論是以氚水(tritiated water)或者是以有機鍵結(organically bound tritium)的方式存在，都會進入到細胞核內並圍繞在 DNA的周圍，進而可能對人體造成嚴重的生物效應。本研究利用PENetration and Energy Loss of Positrons and Electrons(以下簡稱PENELOPE)，進行粒子遷移模擬。本研究主要為低能量電子模擬，模擬低能量電子均勻分布於細胞核(源區，Source region)內向外運動射出，爾後遷移至細胞核(靶區，Target region)內造成之能量沈積(或細胞質至細胞核或細胞膜至細胞核)，再據以求得、線性能量分布、頻率平均線性能量等，及細胞S值等微劑量學參數。本研究，主要模擬兩種不同大小的細胞，將源區與靶區分別各自定義為細胞核、細胞質、細胞膜、或整個細胞。在頻率平均線性能量的評估上，若初始能量的電子射程越接近靶區的大小時，數值越大。上述之研究結果，針對單能量電子與氚放射性核種，藉由這些計算，可做為核醫藥物與環境放射性核種用於生物效應評估依據，也可依不同細胞內源區與靶區之組合，評估最有效之核醫診斷與治療。

參考文獻
1. F. Salvat, J. M. Fernandez-Varea, E. Acosta and J. Sempau
“PENELOPE – A Code System for Minte Carlo Simulation of Electron and Photon Transport (version 2001)” . ISBN: 92-64-18475-9

2. Committee Examining Radiation Risks of Internal Emitters. Tritium: Properties, Metabolism and Dosimetry. 8th Meeting of CERRIE, February 27, London, 2003

3. International Commission on Radiation Units and Measurements. Microdosimetry. ICRU Report 36, 1983

4. National Council on Radiation Protection & Measurements. Tritium and Other Radionuclide Labeled Organic Compounds Incorporated in Genetic Material. NCRP Report No. 63, 1979

5. International Commission on Radiation Units and Measurements. Radiation quantities and Units. ICRU Report 33, 1980

6. ICRP Publication 30: Limits for the Intake of Radionuclides by Workers, Part 1, 30 Edited By . International Commission on Radiological Protection ISBN: 0-08-022638-8, 1979

7. H. Rossi, M. Zaider, ”Microdosimerty and its application”,
Springer, NY, U.S.A., 1996

8. L. Robin Hill and R. John Johnson, “Metabolism and Dosimetry of Tritium”, Health Phys. 65(6), 628-647, 1993

9. D. M. Hamby and T. S. Palmer, “Analysis of an Internal Kinetic Model for Free and Bound Tritium”. Health Phys. 81(4):426-37, 2001

10. K. Morstin, M. Kopec, P. Olko, T. Schmitz, LE. Feinendegen, Microdosimetry of Tritium, Institute of Physics and Nuclear Techniques AGH, Krakow, Porland.

11. DJ. Crawford-Brown, “An age-dependent model of tritium metabolism following mixed (organic/inorganic) intakes”, Health Phys. Apr;46(4):924-8, 1984.

12. S. Diabate and S. Strack , “Organically Bound Tritium”, Health Phys. 65(6), 698-712, 1993

13. J.D. Harrison , A. Khursheed and B.E. Lambert, “Uncertainties in dose coefficients for intakes of tritiated water and organically bound forms of tritium by members of the public”, Radiat Prot Dosimetry, 299-311, 2002

14. P. Pihet, H. G. Menzel, R. Schmidt, M. Beauduin and A. Wambersie, “Biological Weighting Function For RBE Specification of Neutron Therapy Beams”. Radiation Protection Dosimetry. Vol. 31, No. 1/4, pp.437-442, 1990

15. Yin-Hsun Hu, “Study of Cellular Microdosimetry by Monte Carlo Simulation”, Department of Atomic Science, Taiwan, 2005

16. C.J. Tung, C.S. Liu, J.P. Wang, S.L. Chang, “Calculations of cellular microdosimetry parameters for alpha particles and electrons. ”, Applied Radiation and Isotopes 61 739–743, 2004

17. W. Howell Roger, G. Bouchet Lionel, E. Bolch Wesley, V. Rao Dandamudi, S. Goddu Murty, ”Mird Cellular S. Values: Self-Absorbed Dose per unit Cumulated Activity for Selected Radionuclides and Monoenergetic Electron and Alpha Particle Emitters Incorporated into”, 1999

18. J. Sempau and P. Andreo, ” Configuration of the electron transport algorithm of PENELOPE to simulate ion chambers”, Phys. Med. Biol. 51 3533-3548, 2006

19. D. Frankenberg, K. Kelnhofer, K. Bär, and M. Frankenberg-Schwager “Enhanced Neoplastic Transformation by Mammography X Rays Relative to 200 kVp X Rays: Indication for a Strong Dependence on Photon Energy of the RBEM for Various End Points”, Radiation Research 157(1):99-105, 2002