Table B.25: Red bone marrow in the whole body - Helmholtz ...

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5 3. Calculational method ___________________________________________________________ The organ dose conversion factors were calculated using a computer code simulating photon transport in various media. For this procedure, three main components are necessary: a model of the radiation source, a technique to simulate the radiation interactions and energy depositions and a model of the human body. According to the irradiation conditions mentioned above, the radiation source was modelled as a point source rotating around the longitudinal axis of the body; the beam size at the axis of rotation was 1 cm in height and 50 cm in width for the symmetrical beam (for asymmetrical beams, the width was reduced on one side). To simulate the x ray spectra as they emerge from the x ray tube, a semi-empirical method was used considering the target material, inherent as well as added filtration, air path, target angle and tube voltage /8/. 3.1. Monte Carlo method The radiation transport in the phantoms was calculated using a Monte Carlo code following individual photon histories. For each single particle history, the parameters influencing its actual course are selected randomly from their probability distributions. The radiation interaction processes considered were photoelectric absorption and Compton scattering. The cross section data for the radiation interactions were taken from the Oak Ridge National Laboratory /9/. The energy was regarded as being deposited at the point of photon interaction; secondary particles were not followed ("Kerma approximation"). A more detailed description of the photon transport code used is given elsewhere /10/. The absorbed doses were obtained by dividing the total amount of energy deposited in an organ by the mass of this organ. It is to be emphasised that
6 all doses presented in this catalogue are mean doses averaged over the whole organ or tissue, not doses only to that part of the organ included in the CT slice and irradiated directly. The number of individual photon histories followed per single CT slice was 1.000.000; the Monte Carlo calculations were performed on an Intel Hypercube IPSC. 3.2. Human phantoms The models of the human body used for the calculations were the GSF tomographic paediatric models "BABY" and "CHILD" which were constructed from whole body CT data of real patients /10,11/. Each organ and tissue of these "voxel" models consists of volume elements (= voxels), derived from the CT data. Therefore, the location and shape of the organs and tissues is accurately modelled. Special care is given to the modelling of the red bone marrow as it is very sensitive to radiation and is related to leukaemia risk. The relative amount of bone marrow in each voxel within the skeleton can be estimated from the CT numbers of the respective bone pixels (= picture elements). Thus, the spatial resolution of the red bone marrow can be assessed with a resolution as fine as the voxel size, i.e. 2.9 mm 3 for the baby and 19 mm 3 for the child. The baby was eight week old when it was scanned and represents, thus, babies from new-born up to several months. The child was seven years old; it was, however, slightly small for its age and can be regarded as representative for the age between five and seven years. Being reconstructed from CT data, the phantoms are primarily made up as a matrix of rows, columns and slices containing the respective volume elements. Using the appropriate voxel dimensions with respect to width, depth and height, this matrix can be related to a Cartesian co-ordinate system. The x-axis is directed across the columns from the phantoms' right towards their left side, the y-axis is directed across the rows from the front towards the back and the z-axis across the slices from the top of the head down to the feet. The origin is at the upper right frontal corner of this ma-
Page 1 and 2: Tomographic Anthropomorphic Models
Page 3 and 4: Contents (continued) Appendix B: Or
Page 5 and 6: Contents (continued) Appendix D: Or
Page 7 and 8: 2 1. Introduction _________________
Page 9: 4 2.2. Radiation qualities Two radi
Page 13 and 14: 8 4. Description of the data presen
Page 15 and 16: 10 The last column in each table pr
Page 17 and 18: 12 For reliable determination of or
Page 19 and 20: 14 ever, often performed using an a
Page 21 and 22: 16 during an individual examination
Page 23 and 24: 18 6. Conclusions _________________
Page 25 and 26: 20 References _____________________
Page 28 and 29: 23 Appendix A Anatomical Data of th
Page 30 and 31: 25 Appendix B Organ Dose Conversion
Page 32 and 33: 27 Table B. 1: Adrenals (continued)
Page 34 and 35: 29 Table B. 2: Bladder (continued)
Page 36 and 37: 31 Table B. 4: Breast Mean organ do
Page 38 and 39: 33 Table B. 5: Colon Mean organ dos
Page 40 and 41: 35 Table B. 6: Eye lenses Mean orga
Page 42 and 43: 37 Table B. 7: Kidneys Mean organ d
Page 44 and 45: 39 Table B. 8: Liver Mean organ dos
Page 46 and 47: 41 Table B. 9: Lungs Mean organ dos
Page 48 and 49: 43 Table B.10: Oesophagus Mean orga
Page 50 and 51: 45 Table B.11: Ovaries Mean organ d
Page 52 and 53: 47 Table B.12: Pancreas (continued)
Page 54 and 55: Table B.13: Red bone marrow in the
Page 56 and 57: 51 Table B.14: Red bone marrow in t
Page 58 and 59: 53 Table B.16: Red bone marrow in t
Page 60 and 61:
55 Table B.17: Red bone marrow in t
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Table B.26: Skeleton (whole body) 7
Page 78 and 79:
73 Table B.27: Skin (whole body) Me
Page 80 and 81:
75 Table B.28: Small intestine Mean
Page 82 and 83:
77 Table B.29: Spleen Mean organ do
Page 84 and 85:
79 Table B.30: Stomach Mean organ d
Page 86 and 87:
81 Table B.31: Testes Mean organ do
Page 88 and 89:
83 Table B.32: Thymus (continued) S
Page 90 and 91:
85 Table B.33: Thyroid (continued)
Page 92 and 93:
87 Table B.34: Tissue (whole body)
Page 94 and 95:
89 Appendix C Anatomical Data of th
Page 96 and 97:
91 Appendix D Organ Dose Conversion
Page 98 and 99:
93 Table D. 1: Adrenals (continued)
Page 100 and 101:
95 Table D. 2: Bladder (continued)
Page 102 and 103:
97 Table D. 3: Brain (continued) Sl
Page 104 and 105:
99 Table D. 4: Breast (continued) S
Page 106 and 107:
101 Table D. 5: Colon (ascending an
Page 108 and 109:
103 Table D. 6: Colon (descending a
Page 110 and 111:
Table D. 7: Eye lenses (continued)
Page 112 and 113:
107 Table D. 8: Kidneys (continued)
Page 114 and 115:
109 Table D. 9: Liver (continued) S
Page 116 and 117:
111 Table D.10: Lungs (continued) S
Page 118 and 119:
113 Table D.11: Oesophagus (continu
Page 120 and 121:
115 Table D.12: Ovaries (continued)
Page 122 and 123:
Table D.13: Pancreas (continued) 11
Page 124 and 125:
119 Table D.14: Red bone marrow in
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Table D.28: Skeleton (whole body) 1
Page 152 and 153:
147 Table D.29: Skin (whole body) M
Page 154 and 155:
149 Table D.30: Small intestine Mea
Page 156 and 157:
151 Table D.31: Spleen Mean organ d
Page 158 and 159:
153 Table D.32: Stomach Mean organ
Page 160 and 161:
155 Table D.33: Testes Mean organ d
Page 162 and 163:
157 Table D.34: Thymus Mean organ d
Page 164 and 165:
159 Table D.35: Thyroid Mean organ
Page 166 and 167:
161 Table D.36: Tissue (whole body)
Page 168 and 169:
163 Table D.37: Uterus Mean organ d
Page 170 and 171:
165 Appendix E Selected Organ Dose
Page 172 and 173:
167 Table E. 1: Red bone marrow in
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175 Table E. 5: Skeleton (whole bod
Page 182 and 183:
177 Table E. 6: Skin (whole body) (
Page 184:
179 Table E. 7: Tissue (whole body)
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Table B.25: Red bone marrow in the whole body - Helmholtz ...

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