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

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13 were calculated with respect to exposure geometry, patient size and internal geometry and beam quality. Individual situations are likely to differ from that simulated in the calculation with respect to some of these conditions. In the following, some possibilities are shown to adjust the tabulated values to the individual examination under consideration. 5.2.1. Exposure geometry In the tables, the height ranges of the scanned body sections are given in integer centimetre values. In cases where z l and z u are not integer, appropriate proportions of the conversion factors for the respective slices have to be taken for summation. This is, for example, of consequence in those rare situations when the necessity arises to estimate organ doses from single CT scans with slices thickness less than 1 cm. In these cases, the values of f(organ,z) are to be multiplied with the ratio of the actual slice width and 1 cm. In the case of very thin slices of 1 or 2 mm, however, it should be considered that the real slice width is often considerably larger than the nominal one /7,14/. Conversion factors for both full 360° rotation of the fan beam and 180° rotation around the front side of the body are listed in the tables. These geometries were found to be the most common /6,7/. There might be some cases where a 180° rotation around the rear body side is performed. For these exceptional situations, organ dose conversion factors can be reconstructed from those given: as the conversion factors for 360° rotation present the arithmetic mean of 180° rotations around the frontal and the rear body side, values D(organ,z,180° p.a. ) for the latter 180° rotation can be calculated from those given, D(organ,z,360°) and D(organ,z,180° a.p. ), as follows: D ( organ , z , 180° ) = 2• D ( organ , z , 360° ) − D ( organ , z , 180° ) pa . . ap . . With respect to focus-to-axis distance, the organ dose conversion factors which were calculated for a distance of 75 cm are equally suitable for all distances between 70 cm and 85 cm. The dose conversion factors presented in the tables of Appendices B and D were calculated for irradiation with symmetrical beams. Scans are, how-
14 ever, often performed using an asymmetrical beam, that means the beam extends to the full width only on one side of the central axis and to a restricted width on the other side. Consequently, only a smaller circle around the axis of rotation is symmetrically irradiated, the area outside is not. As already mentioned above, babies are, due to their small body size, lying entirely within the fully irradiated part of the beam; therefore, asymmetrical beams need not be considered for patients at this age. Older children are broad enough that more lateral body regions are not symmetrically irradiated. Conversion factors for relevant tissues in this region are given in Appendix E for irradiation with asymmetrical beams; the doses to other tissues are not affected. 5.2.2. Patient size and internal geometry Although the phantoms used for the dose calculations represent a realistic patient geometry since they were constructed from whole body CT data of real persons, they are unlikely to resemble in detail any individual patient under consideration as human anatomy differs from patient to patient. Since the depth dose curves resulting from rotational scans are very flat in the vicinity of the rotational centre, errors due to discrepancies in the radial position of a centrally located organ between patient and phantom remain small. For a patient for whom the location of an organ relative to the given anatomical landmarks deviates from that in the phantoms with respect to height, this can be accounted for by considering the respective organ dose conversion factors for sections shifted accordingly. Doses for patients with body sizes different than those of the phantoms can be estimated from the conversion factors given for the child and the baby phantoms by interpolation. The best method for this would be to evaluate the organ doses for the child and the baby phantom separately, summing up the conversion factors for those sections representing the scanned body region with respect to the anatomical landmarks, irrespective of the actual height of the scanned body region. Suitable interpolation between these summed up organ doses should then be made.
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 and 10: 4 2.2. Radiation qualities Two radi
Page 11 and 12: 6 all doses presented in this catal
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: 12 For reliable determination of or
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 68 and 69:
63 Table B.22: Red bone marrow in t
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
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
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
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Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
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
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
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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