Table 7.
Median and range, in parentheses, of measurement precision of CTDI100,air, HVL, QVL, and CTDIw (for a 16 and 32 cm CTDI phantom) calculated values. Within-run precision was only evaluated for CTDI100,air data (collected using the techniques that appear in Table 2), thus “-” is shown for all other dosimetry metrics. Between-run and between-scanner individual %CVs were calculated from data collected at a given technique (shown in Tables 3, 4, 5 for CTDI100,air, HVL and QVL, and CTDIw, respectively) on the same make and model of scanner.
| Dosimetry metric | Scanner make and model | Intrascanner precision, CV (%) | Interscanner (between-scanner) precision, CV (%) | ||
|---|---|---|---|---|---|
| Within-run | Between-run (weekly) | Between-run (quarterly∕triannual)a | |||
| CTDI100,air | GE VCT | 0.05 | 0.52 | 0.58 | 1.83 |
| (0.04–0.11) | (0.10–0.76) | (0.47–1.04) | (0.92–4.33) | ||
| GE LightSpeed 16 | 0.08 | 0.12 | 2.31 | 0.79 | |
| (0.06–0.10) | (0.01–1.13) | (2.12–3.13) | (0.50–1.95) | ||
| Siemens Sensation 64 | 0.19 | 0.47 | 1.76 | 1.46 | |
| (0.00–0.86) | (0.25–0.63) | (1.26–2.39) | (0.31–3.06) | ||
| HVL | GE VCT | - | 0.19 | 0.42 | 0.73 |
| (0.02–1.86) | (0.20–2.19) | (0.13–2.74) | |||
| GE LightSpeed 16 | - | 0.22 | 0.77 | 0.83 | |
| (0.08–1.46) | (0.36–1.04) | (0.51–2.03) | |||
| Siemens Sensation 64 | - | 0.24 | 0.92 | 1.04 | |
| (0.06–0.75) | (0.67–1.17) | (0.30–1.71) | |||
| QVL | GE VCT | - | 0.37 | 0.43 | 0.66 |
| (0.05–0.76) | (0.11–0.50) | (0.25–1.41) | |||
| GE LightSpeed 16 | - | 0.30 | 0.47 | 0.59 | |
| (0.08–0.72) | (0.29–1.08) | (0.35–0.94) | |||
| Siemens Sensation 64 | - | 0.19 | 0.54 | 0.79 | |
| (0.02–0.83) | (0.31–0.67) | (0.28–1.14) | |||
| CTDIw(16 cm CTDI phantom) | GE VCT | - | 0.70 | 1.32 | 1.71 |
| (0.11–1.70) | (0.83–1.45) | (0.65–3.01) | |||
| GE LightSpeed 16 | - | 0.38 | 2.79 | 0.94 | |
| (0.08–1.06) | (2.44–2.88) | (0.35–1.52) | |||
| Siemens Sensation 64 | - | 1.14 | 2.54 | 1.49 | |
| (0.88–3.77) | (1.92–3.64) | (0.29–3.41) | |||
| CTDIw(32 cm CTDI phantom) | GE VCT | - | 1.19 | 0.84 | 1.73 |
| (0.39–2.53) | (0.61–1.84) | (0.51–3.44) | |||
| GE LightSpeed 16 | - | 1.23 | 2.47 | 1.09 | |
| (0.34–2.29) | (1.25–2.79) | (0.62–2.22) | |||
| Siemens Sensation 64 | - | 0.62 | 2.08 | 1.95 | |
| (0.24–1.43) | (1.30–3.07) | (0.59–4.11) | |||
a
Between-run (quarterly) precision was assessed for the Siemens scanners, which were tested at site B; between-run (triannual) precision was assessed for both models of GE scanners tested at site A.