Scan Theory; Dose Deterministic Effects - GE Revolution CT User Manual

2 Scan Theory

2.1 Dose Deterministic Effects

There is the possibility that in normal use, the patient could be exposed to radiation dose levels
of 1Gy CTDI
100 (peripheral)
Management of the high radiation dose is critical to maintain radiation safety. The available
scan settings concerning radiation dose, air kerma, air kerma rate, radiation quality, and image
quality include: mA, kV, scan time, detector coverage, and SFOV.
The table below provides the scan duration in seconds required to meet 1Gy CTDI
200 mA exposure at same scan location. This table assumes 200 mA and provides scan time
as a practical example for an average patient. The product of the scan time shown and 200 mA
yields the mAs required to result in 1Gy CTDI
SFOV combination in the table, any mA and scan time combination that meets or exceeds the
equivalent mAs of this table can also result in deterministic effects of radiation. For obese
patients, the mA may be larger than the practical example shown in the table, and the resulting
mAs should be used to determine the exposure to the patient.
Table 1: Dose Deterministic Effects
Ped Head
SFOV Ped Body
Small Head
CTDI Phantom
Focal Spot XL
160 NA
140 NA
120 NA
70
80 NA
40 NA
5 NA
160 NA
140 NA
120 NA
80
80 NA
40 NA
5 NA
160 NA
140 NA
120 NA
100
80 NA
40 NA
5 NA
218
or above, at which deterministic effects may become apparent.
Duration of Cine scan(s) at 200 mA required to meet 1Gy CTDI
Head
16cm 16cm
L S XL L
142 142 NA 123
147 147 NA 126
153 153 NA 130
156 156 NA 133
145 145 NA 124
88 98 NA 75
99 99 NA 83
102 102 NA 85
106 106 NA 88
108 109 NA 90
101 101 NA 84
61 68 NA 51
55 55 NA 46
56 56 NA 48
59 59 NA 49
60 61 NA 50
56 56 NA 47
34 38 NA 28
. Note that for each kV / Aperture /
100 (peripheral)
Small Body
Cardiac Small
32cm
S XL L S
122 NA 253 253
126 NA 263 263
130 NA 279 279
135 NA 303 303
124 NA 281 281
84 NA 169 189
82 NA 174 174
85 NA 180 180
88 NA 191 191
91 NA 207 207
84 NA 193 193
57 NA 116 129
46 NA 95 95
48 NA 99 99
49 NA 104 104
51 NA 113 113
47 NA 106 106
32 NA 64 71
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
100 (peripheral)
100 Peripheral
Medium Body
Cardiac Medium
32cm
XL L S XL
NA 213 213 NA
NA 221 221 NA
NA 234 234 NA
NA 255 255 NA
NA 237 237 NA
NA 143 160 NA
NA 142 142 NA
NA 148 148 NA
NA 156 156 NA
NA 170 170 NA
NA 158 158 NA
NA 95 107 NA
NA 79 79 NA
NA 82 82 NA
NA 87 87 NA
NA 94 94 NA
NA 87 87 NA
NA 53 59 NA
2 Scan Theory
at
Large Body
Cardiac Large
32cm
L S
261 261
273 273
289 289
314 318
292 292
176 197
166 166
174 174
184 184
200 202
186 186
112 126
87 87
91 91
96 96
105 106
97 97
59 66