由於現代醫學的進步，造成國民所受的放射診斷輻射劑量十分可觀，因此如何評估病患劑量便顯得相當重要。對於照野固定的X光照像而言，病患的器官劑量無法直接度量，必須用入射表面劑量(entrance surface dose, ESD)作為指標，因此發展出一個轉換因子，其定義是器官劑量除以ESD。我們只要度量獲得X光照像時的ESD，藉由這個轉換因子，就可以很容易地知道器官劑量以評估健康風險。
本研究乃利用一個理想的蒙地卡羅程式，BEAMnrc，來模擬X光機，然後將產生的X光入射到VIP-Man上，以模擬胸部X光照像時的器官劑量轉換因子。VIP-Man是高解析度的斷層假體(tomographic phantom)，因此在計算器官劑量的結果上，具有良好的準確性。本文把模擬結果與NRPB-R186報告相互比較，以探討斷層假體和數學假體在模擬器官劑量轉換因子上的變因。此外，本文也模擬臺大醫院的X光機，並且將VIP-Man調整成符合台灣成年男性之平均身高體重，以求得我國國人胸部X光照像時之器官劑量轉換因子。
由於個體之間的解剖幾何差異性，使的斷層假體僅適用於某一特定體型的人體，因此利用VIP-Man模擬出來的器官劑量轉換因子，在使用上也要特別小心。本文除了研究VIP-Man和數學假體在器官劑量轉換因子的差異外，也提供了符合我國國人的器官劑量轉換因子，以期作為最優化或國民劑量之研究開端。

[1] Dosimetry Working Party of the Institute of
Physical Sciences in Medicine.National protocol for
patient dose measurements in diagnostic radiology.
Chilton,NRPB, 1992.
[2] ICRP. Diagnostic reference levels in medical imaging,
DRAFT ICRP Committee3,2001.
[3] Hart D, Wall BF. Radiation exposure of the UK
population from medical and dental x-ray examinations.
NRPB Publication W4, 2002.
[4] ICRP. 1990 recommendations of the International
Commission on Radiological Protection. Oxford: Pergamon
Press, ICRP Publication 60, 1991.
[5] Rosenstein, M. Organs doses in diagnostic radiology. US
Department of Health, Education and Welfare, Food and
Drug Administration. Rockville, MD, 1976.
[6] Drexler G, Panzer W, Widenmann L, Williams G and Zankl
M. The calculation of dose from external photon
exposures using reference human phantoms and Monte
Carlo methods, Part III: Organ doses in x-ray
diagnosis. GSF-Bericht S-1026, ISSN 0721-1694, 1984.
[7] Jones D G and Wall B F. Organ doses from medical x-ray
examinations calculated using Monte Carlo techniques.
NRPB Report R-186, 1985.
[8] ICRU. Phantoms and computational models in therapy,
diagnosis and protection ICRU Report 48. Bethesda, MD,
1992.
[9] Snyder W S, Ford M R, Warner G G and Fisher H L.
Estimates of absorbed fractions for monoenergetic
photon sources uniformly distributed in various
organs of a heterogeneous phantom. MIRD Pamphlet No.5.
J. Nucl. Med. 10, 1969.
[10] ICRP. Report of the task group on Reference Man.
Oxford: Pergamon Press,ICRP Publication 23, 1975.
[11] Hwang J M L, Poston J W, Shoup R L and Warner G G.
Maternal, fetal and pediatric phantoms. Oak Ridge, TN:
Oak Ridge National Laboratory, Report No. ORNL-5046,
259-261, 1975.
[12] Jones R M, Poston J W, Hwang J L, Jones T D and Warner
G G. The development and use of a fifteen year old
equivalent mathematical phantom for internal dose
calculations. Oak Ridge, TN: Oak Ridge National
Laboratory, Report No. ORNL/TM-5278, 1976.
[13] Deus S F and Poston J W. The development of a
mathematical phantom representing a ten-year-old for
use in internal dosimetry calculations. Oak Ridge, TN:
Oak Ridge National Laboratory Health Physics Division
Annual Progress, Report No. ORNL-5171, 76-79, 1976.
[14] Cristy M. Mathematical phantoms representing children
of various ages for use in estimates of internal dose.
Oak Ridge, TN: Oak Ridge National Laboratory, Report
No. ORNL/NUREG/TM-367, 1980.
[15] Kramer R, Zankl M, Williams G and Drexler G. The
calculation of dose from external photon exposures
using reference human phantoms and Monte Carlo
methods: part I. the male (Adam) and female (Eva)
adult mathematical phantoms GSF-Report S-885, 1982.
[16] Cristy M and Eckerman K F. Specific Absorbed Fractions
of Energy at Various Ages from Internal Photon
Sources. Oak Ridge, TN: Oak Ridge National Laboratory,
Report No. ORNL/TM-8381 vol 1–7, 1987.
[17] Stabin M G, Tagesson M, Thomas S R, Ljungberg M and
Strand S E. Radiation dosimetry in nuclear medicine.
Appl. Radiat. Isot. 50, 73–87, 1999.
[18] Gibbs S J, Pujol A, Chen T-S, Malcolm A W and James A
E. Patient risk from interproximal radiography. Oral
Surgery, Oral Medicine, Oral Pathology 58, 347–54,
1984.
[19] Williams G, Zankl M, AbmayrW, Veit R and Drexler G.
The calculation of dose from external photon exposures
using reference and realistic human phantoms and Monte
Carlo methods. Phys. Med. Biol. 31, 449–52, 1986.
[20] Zankl M, Veit R, Williams G, Schneider K, Fendel H,
Petoussi N and Drexler G. The construction of computer
tomographic phantoms and their application in
radiology and radiation protection. Radiat. Environ.
Biophys. 27, 153–64, 1988.
[21] Veit R, Zankl M, Petoussi N, Mannweiler E,Williams G
and Drexler G. Tomographic anthropomorphic models,
part I: construction technique and description of
models of an 8 week old baby and a 7 year old child.
GSF-Bericht 3/89, 1989.
[22] Dimbylow P J. Proc. Voxel Phantom Development.
Chilton, NRPB, 1996a.
[23] Zubal I G, Harrell C R, Smith E O, Rattner Z, Gindi G
and Hoffer P B. Computerized three-dimensional
segmented human anatomy. Med. Phys. 21, 299–302, 1994.
[24] Caon M, Bibbo G and Pattison J. An EGS4-ready
tomographic computational model of a fourteen year-old
female torso for calculating organ doses from CT
examinations. Phys. Med. Biol. 44, 2213–25, 1999.
[25] Saito K, Wittmann A, Koga S, Ida Y, Kamei K and Zankl
M. The construction of a computed tomographic phantom
for a Japanese male adult and the dose calculation
system. Radiat. Environ. Biophys. 40, 69–76, 2001.
[26] Xu X G, Chao T C and Bozkurt A. VIP-MAN: An image-
based whole-body adult male model constructed from
color photographs of the Visible Human project for
multi-particle Monte Carlo calculations. Health Phys.
78, 476–86, 2000.
[27] Petoussi-Henss N, Zankl M, Fill U and Regulla D. The
GSF family of voxel phantoms. Phys. Med. Biol. 47, 89–
106, 2002.
[28] Zankl M, Fill U, Petoussi-Henss N and Regulla D. Organ
dose conversion coefficients for external photon
irradiation of male and female voxel models. Phys.
Med. Biol. 47, 2367-85, 2002.
[29] Kramer R, Vieira JW, Khoury HJ, de Andrade Lima F. MAX
meets ADAM: a dosimetric comparison between a voxel-
based and a mathematical model for external exposure
to photons. Phys Med Biol. 49(6), 887-910, 2004.
[30] D.W.O. Rogers, C.-M. Ma, B. Walters, G.X. Ding, D.
Sheikh-Bagheri and G. Zhang. BEAMnrc User’s Manual.
National Research Council of Canada, 2002.
[31] Spitzer, V.M., Whitlock, D.G. Atlas of the Visible
Human Male. Jones and Bartlett Publishers
International, 1998.
[32] ICRP. Report of the task group on Reference Man.
Oxford: Pergamon Press, ICRP Publication 23, 1975.
[33] ICRU. Tissue substitutes in radiation dosimetry and
measurement. ICRU Report 44. Bethesda, MD, 1989.
[34] ICRP. Human respiratory tract model for radiological
protection. Oxford: Pergamon Press, ICRP Publication
66, 1994.
[35] Chao T C, Xu X G. Specific absorbed fractions from the
image-based VIP-man body model and EGS4-VLSI Monte
Carlo code: Internal electron emitters. Phys. Med.
Biol. 46, 901—927, 2001.
[36] Chao T C, Bozkurt A, Xu X G. Conversion coefficients
based on VIP-man anatomical model and EGS4-VLSI code
for monoenergetic photon beams from 10keV to 10 MeV.
Health Phys. 81(2), 163—183, 2001.
[37] Chao T C, Bozkurt A, Xu X G. Dose conversion
coefficients for 0.1—10 MeV electrons calculated for
the VIP-Man tomographic model. Health Phys. 81(2),
203—214, 2001.
[38] Petoussi-Henss N, Zankl M, Drexler G, Panzer W and
Regulla D. Calculation of backscatter factors for
diagnostic radiology using Monte Carlo methods. Phys.
Med. Biol. 43, 2237-50, 1998.
[39] Bhat M, Pattison J, Bibbo G and Caon M. Diagnostic x-
ray spectra: a comparison of spectra generated by
different computational methods with a measured
spectrum. Med. Phys. 25, 114-20, 1998.
[40] T. R. Fewell and R. E. Shuping. Photon energy
distribution of some typical diagnostic x-ray beams.
Med. Phys. 4, 187–196, 1977.
[41] Eckerman K F, Cristy M and Ryman J C. The ORNL
Mathematical Phantom Series. Oak Ridge, TN, 1996.
[42] http://media.justsports.net.tw/spo_demo/publish_local.
asp, 行政院體育委員會網站, 九十一年體育統計.