Descriptive statistics of Hounsfield units (HU) values according to the measurements of readers 1 and 2, inter-reader reliability and agreement for each vertebral level
| Vertebra | Reader 1—HU values | Reader 2—HU values | ICC† | SDD‡ | ||
| Mean (SD) | Range | Mean (SD) | Range | |||
| C3 | 354 (106) | 162–643 | 355 (108) | 158–647 | 0.98 | 6 |
| C4 | 350 (113) | 119–661 | 350 (113) | 122–668 | 1.00 | 5 |
| C5 | 333 (109) | 83–601 | 333 (109) | 88–605 | 0.90 | 6 |
| C6 | 290 (88) | 82–481 | 289 (88) | 83–479 | 1.00 | 5 |
| C7 | 271 (83) | 79–447 | 270 (82) | 81–440 | 1.00 | 7 |
| T1 | 229 (86) | 69–431 | 224 (87) | 67–426 | 1.00 | 6 |
| T2 | 246 (59) | 55–382 | 240 (58) | 57–384 | 0.99 | 6 |
| T3 | 230 (71) | 88–402 | 223 (69) | 90–407 | 0.99 | 6 |
| T4 | 222 (69) | 41–333 | 210 (66) | 43–335 | 0.99 | 5 |
| T5 | 208 (56) | 59–369 | 204 (57) | 53–362 | 0.98 | 4 |
| T6 | 205 (63) | 31–319 | 194 (63) | 32–312 | 0.98 | 5 |
| T7 | 198 (78) | −9 to 353 | 187 (74) | −10 to 359 | 0.99 | 5 |
| T8 | 185 (68) | 7–299 | 177 (65) | 3–306 | 0.99 | 7 |
| T9 | 194 (72) | −15 to 307 | 181 (69) | −17 to 304 | 0.99 | 6 |
| T10 | 194 (73) | 18–375 | 181 (71) | 23–372 | 0.99 | 5 |
| T11 | 176 (60) | 29–305 | 168 (60) | 30–302 | 0.97 | 5 |
| T12 | 177 (62) | 28–367 | 166 (58) | 23–372 | 0.97 | 6 |
| L1 | 165 (55) | 11–325 | 162 (54) | 6–317 | 0.89 | 8 |
| L2 | 158 (51) | −13 to 258 | 153 (51) | −9 to 253 | 0.94 | 4 |
| L3 | 154 (65) | −37 to 345 | 150 (65) | −34 to 346 | 0.89 | 8 |
| L4 | 163 (84) | −35 to 459 | 156 (82) | −37 to 461 | 0.91 | 7 |
| L5 | 159 (65) | −12 to 292 | 158 (63) | −8 to 286 | 0.90 | 8 |
*Cervical spine values are based on a total of 44 vertebrae scored at each level (C3–C7) by both readers. The values for thoracic and lumbar spine are based on a total of 50 and 49 vertebrae scored at each level (T1 to L5) by readers 1 and 2, respectively.
†Two-way mixed effects method, single measurements, absolute agreement.
‡SDD=1.96 × SDdifference /(√k); SDdifference is the SD of the differences in status scores between two readers; k is the number of readers (n=2).
HU, Hounsfield Units; ICC, intraclass correlation coefficients; SDD, smallest detectable difference.