Table 4.

HU consistency for Siemens simulation-CT scans. The top table is for 120 kV, and the bottom table is for 140 kV

120 kV		Catphan position
Material	Catphan HU	Center	10 cm up	9 cm down	10 cm left	10 cm right	Max diff.
Air	−1046:−986	−979	−976	−978	−966	−968	13
PMP	−220: −172	−176	−172	−177	−173	−174	5
LDPE	−121:−87	−88	−84	−82	−82	−87	6
Polystyrene	−65:−29	−33	−35	−27	−28	−32	8
Acrylic	92:137	122	120	125	123	123	5
Delrin	344:387	345	344	346	347	346	3
Bone 50%	667:783	614	590	608	588	614	26
Bone 20%	211:263	208	207	206	208	201	7
Teflon	941:1060	918	902	919	911	905	17

140 kV		Catphan position
Material	Catphan HU	Center	10 cm up	9 cm down	10 cm left	10 cm right	Max diff.
Air	−1046:−986	−980	−977	−978	−966	−968	14
PMP	−220: −172	−171	−167	−171	−163	−168	8
LDPE	−121:−87	−81	−77	−75	−72	−81	9
Polystyrene	−65:−29	−25	−28	−20	−20	−23	8
Acrylic	92:137	128	127	132	129	131	5
Delrin	344:387	348	350	353	348	353	5
Bone 50%	667:783	566	542	556	535	563	31
Bone 20%	211:263	192	190	191	194	187	7
Teflon	941:1060	912	898	909	903	902	14

Abbreviations: CT = computed tomography; CBCT = cone-beam computed tomography; HU = Hounsfield unit; LDPE = low-density polythene; PMP = Polymethylpentene.