Table 3.
Radiation dose metrics and technical parameters for CTs sorted by decile in patient size based on effective patient diameter. Each decile includes between 74,883 and 74,888 patients and reflects the mean for all constituent patients. The mean percent increase per decile increase in effective patient diameter, and the percent increase between the 1st and 10th deciles of diameter, is shown for all variables with the 95% confidence interval. Because these reflect mean values, the results may reflect a number that is implausible for an individual scan (e.g., kV = 116). For the percent change, the numbers are rounded to the nearest 1% unless estimate < 10%, where numbers show with 2 significant digits
| Decile abdomen diameter | Patient diameter (mm) | CTDIvol (mGy) | Size-adjusted CTDIvol (mGy) | DLP (mGy-cm) | Size-adjusted DLP (mGy-cm) | Effective Dose (mSv) | Pitch* | Effective mAs | Kilovoltage (kV) | Scan length (cm) | Number of phases | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | ||
|
1st | 238 (238,238) | 7 (7,7) | 12 (12,12) | 403 (401,405) | 709 (705,712) | 9 (9,9) | 1.04 (1.03,1.04) | 109 (109,110) | 116 (116,116) | 45 (45,45) | 1.4 (1.3,1.4) |
| 2nd | 262 (262,262) | 8 (8,8) | 11 (11, 11) | 475 (473, 477) | 675 (672, 678) | 9 (9,10) | 1.03 (1.03, 1.03) | 124 (124, 124) | 117 (117, 117) | 46 (46,46) | 1.3 (1.3, 1.3) | |
| 3rd | 277 (277,277) | 9 (9,9) | 11 (11,11) | 539 (537, 541) | 675 (672, 678) | 10 (9,10) | 1.03 (1.03, 1.03) | 137 (136, 137) | 117 (117, 117) | 47 (47,47) | 1.3 (1.3, 1.3) | |
| 4th | 289 (289,289) | 10 (10,10) | 12 (12, 12) | 608 (606, 611) | 687 (684, 690) | 11 (11,11) | 1.02 (1.02, 1.03) | 149 (149, 150) | 118 (118, 118) | 47 (47,47) | 1.3 (1.3, 1.3) | |
| 5th | 300 (300,300) | 11 (11,12) | 12 (12, 12) | 682 (679, 685) | 699 (696, 702) | 12 (12,12) | 1.02 (1.02, 1.02) | 163 (163, 164) | 118 (118, 118) | 48 (48,48) | 1.3 (1.3, 1.3) | |
| 6th | 311 (311,311) | 13 (13,13) | 12 (12, 12) | 764 (762, 767) | 712 (709, 715) | 12 (12,13) | 1.02 (1.02, 1.02) | 178 (177, 178) | 119 (119, 119) | 49 (49,49) | 1.3 (1.3, 1.3) | |
| 7th | 323 (323,323) | 14 (14,14) | 12 (12, 12) | 865 (862, 868) | 727 (725, 730) | 13 (13,13) | 1.02 (1.02, 1.02) | 195 (195, 196) | 119 (119, 119) | 49 (49,49) | 1.3 (1.3, 1.3) | |
| 8th | 337 (337,337) | 16 (16,16) | 12 (12, 12) | 989 (986, 993) | 737 (734, 740) | 14 (14,15) | 1.01 (1.01, 1.01) | 217 (217, 218) | 120 (120, 120) | 50 (50,50) | 1.3 (1.3, 1.3) | |
| 9th | 356 (356,356) | 19 (19,19) | 12 (12, 12) | 1152 (1148, 1156) | 728 (726, 731) | 16 (16,16) | 1.01 (1.00, 1.01) | 248 (247, 249) | 120 (120, 120) | 51 (51,51) | 1.3 (1.3, 1.3) | |
| 10th | 395 (395,395) | 24 (24,24) | 12 (12, 12) | 1500 (1495, 1505) | 672 (669, 674) | 19 (19,19) | 0.99 (0.99, 0.99) | 312 (311, 313) | 122 (122, 122) | 52 (52,52) | 1.3 (1.3, 1.3) | |
| Percent change 1st to 10th deciles (95% CI)** | 66% (66%, 66%) | 241% (239%, 242%) | 1.5%(1.1%, 1.9%) | 272% (270%, 274%) | -5.3% (-5.8% -4.7%) | 126% (124%, 127%) | -4.3% (-4.5%, -4.0%) | 186% (185%, 187%) | 4.9% (4.9%, 5.0%) | 17%(17%, 17%) | -4.7% (-5.2%, -4.3%) | |
| Mean percent increase per decile (95% CI)** | 5.8% (5.8%, 5.8%) | 15% (15%,1 5%) | 0.20% (0.15%, 0.24%) | 16% (16%, 16%) | -0.54% (-0.60%, -0.48%) | 9.6% (9.5%, 9.7%) | -0.48% (-0.51%, -0.45%) | 12% (12%, 13%) | 0.54% (0.53%, 0.54%) | 1.7% (1.7%, 1.8%) | -0.53% (-0.59%, -0.48 | |
Abbreviations: CI confidence interval, CTDIvol volumetric computed tomography dose index, DLP dose length product, mAs milliampere-seconds, mGy milliGray, mSv millisieverts
*Table distance traveled in one 360° gantry rotation divided by beam collimation
**95% bootstrap confidence intervals using 1,000 bootstrap samples of size 748,846