Article Figures & Data
Figures
- FIGURE 1.
Schematic illustration of exit dose measurement geometry.
- FIGURE 2.
Semilogarithmic graph of exit dose rates for various voltages and currents vs. increasing depth of water in phantom simulating attenuation in patient.
Tables
Exit dose rate (10−2 μGy/s)* Voltage (kV) Current (mA) 0 mm 50 mm 100 mm 150 mm 200 mm 250 mm 300 mm 140 2.5 2,138 1,100 522 235 110 48 24 140 2.0 1,705 887 426 193 87 39 18 140 1.5 1,295 675 323 148 67 29 15 140 1.0 883 460 218 105 44 20 9 120 2.5 1,396 713 332 147 65 29 13 120 2.0 1,126 574 264 117 53 23 10 120 1.5 853 417 201 87 40 17 7 120 1.0 580 280 140 61 28 12 5 ↵* Data are for the stated different depths of water in a cylindric phantom simulating attenuation in a patient. Rates are calculated by dividing cumulative exit doses by time of measurement.
Phantom diameter (mm) Voltage (kV) Current (mA) Reference phantom* 270 200 160 100 140 2.5 42 (35–52) 27 (23–34) 18 (15–21) 11 (9–14) 140 2.0 30 (27–35) 21 (22–25) 12 (10–15) 140 1.5 35 (26–45) 25 (23–32) 14 (12–16) 140 1.0 43 (36–54) 29 (28–33) 16 (14–19) 120 2.5 33 (27–43) 22 (21–26) 13 (11–16) 120 2.0 37 (25–49) 25 (24–31) 15 (13–16) 120 1.5 43 (37–52) 29 (27–34) 17 (15–19) 120 1.0 53 (44–69) 36 (33–42) 20 (17–23) 11 (10–12) ↵* Torso phantom (260 × 380 mm).
Data are SDs in Hounsfield units, followed by ranges in parentheses.
CT parameters CTDIw for abdomen phantom (mGy) CTDIw for head phantom (mGy) 120 kV; 1 mA; axial scanning; collimation, 20 mm; slice thickness, 5 mm — 2.01 140 kV; 2.5 mA; axial scanning; collimation, 20 mm; slice thickness, 5 mm 5.42 7.23
