Table 1.

Radioactivity in the main volume of the phantom, spheres and the sphere–main volume ratio

Part of the phantom	Scans
	1st	2nd	3rd	4th
Discovery 690
Activity concentration (kBq/ml):
total volume	0.36	0.43	0.76	1.2
spheres	3.7	3.0	2.5	2.1
Sphere–total volume activities
ratio	10.3	7.0	3.3	1.7
Biograph mCT 128
Activity concentration (kBq/ml):
total volume	0.40	0.46	0.79	1.3
spheres	4.0	3.2	2.6	2.2
Sphere–main volume activities ratio	10.0	7.0	3.3	1.7
Biograph mCT 40
Activity concentration (kBq/ml):
total volume	0.34	0.40	0.72	1.1
spheres	3.3	2.8	2.4	1.9
Sphere–main volume activities ratio	9.7	7.0	3.3	1.7