Table 2.

Attenuation coefficients used in brain and whole-body applications in the indicated references (units in 1/cm)

Brain	Whole body
Air/cavities/background
0.0 [13, 24, 25, 30–33, 38]   0.003 [40]   0.0536 (nasal sinuses) [25]   0.054 (mastoid process) [30–33]   0.000105 (air, paranasal sinuses), 0.066 (ethmoidal air cells, nasal cavity) [16]	0.0 [21, 36, 44, 45, 49]
Skull/bone
0.116 [40]   0.12 [38]   0.143, 0.151 [24, 25]   0.146 [13, 30–33]   0.143, 0.152, 0.172 [16]	0.11 (spongious bone) [6] 0.13 [6, 45] 0.12–0.14 [47] 0.15 [49]
Soft tissue
0.086 (soft), 0.064 (fat) [40]   0.095 [13, 30–33]   0.1 (muscle, skin, connective tissue), 0.092 (fat) [16]	0.093, 0.086 (fat) [21] 0.093 (fat–non-fat), 0.101 (non-fat) [21] 0.094, 0.086 (fat) [36] 0.095 [47] 0.0968 (soft), 0.0927 (fat) [6] 0.097 [45] 0.1, 0.086 (fat) [44, 49]
Brain tissue
0.095 [38]   0.096 [24, 30, 33]   0.099 [13, 31, 32]   0.0993 [25]   0.097 (CSF), 0.1 (GM,WM) [16]
Lung tissue
	0.018 [44] 0.024 [21, 36] 0.0267 [6] 0.03 [45, 49]
Liver tissue
	0.0977 [6]