Table 1. PET/CT quantification of known volumes with different activity of 18F-FDG inside an anthropomorphic phantom.

PET grid → CT grid					CT grid → Dose calculation grid
Interpolation method	V1 (% deviation from the real 0.30 ml)	V2 (% deviation from the real 0.30 ml)	V3 (% deviation from the real 2.00 ml)	V2 + V3 (% deviation from the real 2.30 ml)	Interpolation method	V1 (% deviation from the real 0.30 ml)	V2 (% deviation from the real 0.30 ml)	V3 (% deviation from the real 2.00 ml)	V2 + V3 (% deviation from the real 2.30 ml)
Linear	0.38 (+26.7)	0.40 (+33.3)	1.96 (-2.0)	2.36 (+2.6)	Linear	0.35 (+16.7)	0.42 (+40.0)	2.21 (+10.5)	2.63 (+14.3)
					Nearest-neighbor	0.38 (+26.7)	0.40 (+33.3)	1.94 (-3.0)	2.34 (+1.7)
					Spline	0.64 (+113.3)	0.50 (+66.7)	2.43 (+21.5)	2.93 (+27.4)
Nearest-neighbor	0.34 (+13.3)	0.41 (+36.7)	1.86 (-7.0)	2.27 (-1.3)	Linear	0.31 (+3.3)	0.45 (+50.0)	1.95 (-2.5)	2.40 (+4.3)
					Nearest-neighbor	0.32 (+6.7)	0.36 (+20.0)	1.85 (-7.5)	2.21 (-3.9)
					Spline	0.60 (+100.0)	0.53 (+76.7)	2.34 (+17.0)	2.87 (+24.8)
Spline	0.36 (+20.0)	0.35 (+16.7)	1.91 (-4.5)	2.26 (-1.7)	Linear	0.31 (+3.3)	0.38 (+26.7)	2.09 (+4.5)	2.47 (+7.4)
					Nearest-neighbor	0.35 (+16.7)	0.33 (+10.0)	1.91 (-4.5)	2.24 (-2.6)
					Spline	0.60 (+100.0)	0.43 (+43.3)	2.41 (+20.5)	2.84 (+23.5)

Evaluation of different combination of interpolation methods for co-registration of image dataset from PET (1.6 x 1.6 x 1.5 mm voxel size)/CT (1.52 x 1.52 x 1.5 mm³ voxel size) with 512x512 pixels per slice and the dose calculation grid with 256x256 pixels per slice.