Article Figures & Data
Figures
- Fig 1.
Representative CT image of a 6-year-old boy at the level of the vocal cords for assessment of the signal-to-noise ratio. Background noise was estimated as the average SD in Hounsfield units of 2 ROIs drawn over the air anterior to the patient (large circles). Signal was estimated as the average attenuation in Hounsfield units of 2 ROIs drawn over the paraspinal musculature (small circles).
- Fig 2.
Comparison of the median values of tube current (milliampere-seconds) (A), radiation output of scanner (CTDIvol) (B), and scan length between the 2 cohorts (C). Also shown are P values from an unpaired t test.
- Fig 3.
Comparison of the median values of the dose-length product (A) and estimated effective dose (B) between the 2 cohorts. Also shown are the P values from an unpaired t test.
- Fig 4.
Comparison of the median values of the signal-to-noise ratio (A) and image-quality score (B) between the 2 cohorts. Also shown are the P values from an unpaired t test.
Tables
- Table 1:
Total number of patients and distribution of patient age and sex in the 3 age groups of the study
Group 0–4 yr 5–9 yr 10–16 yr 0–16 yr Baseline cohort ♂ 10 11 20 41 ♀ 7 7 20 34 Total (No.) 17 18 40 75 Follow-up cohort ♂ 17 17 21 55 ♀ 8 9 32 49 Total (No.) 25 26 53 104 - Table 2:
Interpretation of the subjective image-quality scores for the individual, prelabeled CT image slices at the level of the vocal cords
Score Comment 1 Image quality very poor (significant noise and/or artifacts, study uninterpretable) 2 Image quality poor (noise and/or artifacts, can only answer broad clinical questions) 3 Image quality adequate (some noise and/or artifacts, but study interpretable) 4 Above-average image quality (minimal noise and/or artifacts) 5 Excellent image quality (imperceptible noise and free of artifacts) - Table 3:
Median values of the scan parameters, signal-to-noise ratio, image-quality scores, estimated effective dose, and the percentage difference for the 2 cohorts
Parameter 0–4 yr 5–9 yr 10–16 yr I II % Diff I II % Diff I II % Diff Tube current (mAs) 150 128 −15 182 162 −11 266 165 −38 CTDIvol (mGy) 7.4 4.4 −41 8.6 5.5 −36 20 7 −67 Scan length (cm) 17.6 17.8 1 20.3 21 5 26 27 1 DLP (mGy-cm) 125 77 −38 175 132 −24 522 240 −54 ED (mSv) 2.1 1.2 −40 2.2 1.7 −21 9.7 4.4 −55 SNR 16.4 13.4 −18 13.4 16.3 22 20.2 16.2 −20 IQ 3.67 4.00 9 4.00 4.00 0 4.33 4.00 −8 Note:—IQ indicates image quality; ED, effective dose; Diff, difference; I, baseline; II, follow-up.
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