Article Figures & Data
Figures
- Fig 1.
Assessment of objective image quality at the level of the mandible (A) and superior mediastinum (B). Region of interest drawn to measure the SD of air bilaterally (background noise), attenuation of the sternocleidomastoid and pectoralis major muscles, internal jugular vein and superior vena cava, and surrounding fat for the estimation of signal-to-noise ratio and contrast-to-noise ratio.
- Fig 2.
Axial images of contrast-enhanced neck CT at the level of oropharynx reconstructed by using 30% adaptive statistical iterative reconstruction (A) and model-based iterative reconstruction (B). Note better conspicuity and definition of tumor margins on MBIR (arrows) compared with ASiR30 (arrows).
- Fig 3.
Axial images of contrast-enhanced neck CT at the level of oropharynx reconstructed by using 30% adaptive statistical iterative reconstruction (A) and model-based iterative reconstruction (B). Note a decrease in the streak artifacts related to dental amalgam particularly in the region of the base of the tongue, parotids, and foramen magnum and a poorer definition of fat planes in the parapharyngeal space on MBIR images.
- Fig 4.
Axial images of contrast-enhanced neck CT at the level of sternoclavicular junction reconstructed by using 30% adaptive statistical iterative reconstruction (A) and model-based iterative reconstruction (B). Artifacts are due to a thyroid shield in the display FOV specific for MBIR (arrows). Note the absence of these thyroid shield artifacts on images reconstructed by using ASiR30 (arrows).
- Fig 5.
Bar graph showing the percentage of agreement and disagreement between the 2 independent readers (1 and 2) for the assessment of subjective image quality at various levels and overall image quality in both categories (category I: ASiR>MBIR and category II: MBIR≥ASiR).
Tables
CT Protocol Scanned region 1 cm above the level of frontal sinus to aortopulmonary window Type Helical 0.5-second duration. Pitch 0.984:1 Gantry tilt 0° Section thickness and section interval 0.625-mm-thick/0.625 interval and 40-mm detector coverage Reconstruction Standard soft-tissue algorithm with 2.5-mm thickness Matrix 512 × 512 Kilovolt(peak) 140 Noise index at 0.625-mm section thickness 40 HU MBIR ASiR Difference (MBIR-ASiR) Mean (95% CI) Mean (95% CI) Mean (95% CI) P Valuea Level 1 (angle of mandible) Mean of IJV (HU) 130.3 ± 19.6 (125.4–135.1) 131.0 ± 19.2 (126.2–135.8) −0.7 ± 2.7 (−1.4 to −0.1) .030 Mean of SCM (HU) 62.9 ± 5.0 (61.7–64.2) 64.4 ± 4.9 (63.2–65.6) −1.5 ± 2.2 (−2.0 to −0.9) <.001 Mean of fat (HU) −81.4 ± 23.2 (−87.2 to −75.6) −77.1 ± 23.3 (−82.9 to −71.3) −4.2 ± 8.1 (−6.3 to −2.2) <.001 SD of IJV (HU) 6.3 ± 2.6 (5.7–7.0) 7.3 ± 2.0 (6.8–7.8) −1.0 ± 1.9 (−1.5 to −0.6) <.001 SD of SCM (HU) 6.6 ± 1.4 (6.3–7.0) 7.1 ± 1.6 (6.7–7.5) −0.5 ± 1.5 (−0.8 to −0.1) .020 SD of air (BN) (HU) 6.3 ± 9.2 (4.0–8.6) 7.8 ± 9.2 (5.5–10.1) −1.5 ± 4.8 (−2.7 to −0.3) .016 SNR of SCM 16.2 ± 7.2 (14.4–18.0) 12.1 ± 4.3 (11.0–13.2) 4.1 ± 5.7 (2.7–5.5) <.001 CNR of IJV and SCM 7.6 ± 2.6 (7.0–8.3) 6.8 ± 2.4 (6.2–7.4) 0.9 ± 1.4 (0.5–1.2) <.001 Lower level 2 (superior mediastinum) Mean of SVC (HU) 119.8 ± 24.5 (113.7–125.9) 117.8 ± 23.7 (111.8–123.7) 2.0 ± 7.3 (0.2–3.9) .030 Mean of PM (HU) 55.6 ± 11.0 (52.9–58.4) 53.3 ± 13.0 (50.1–56.5) 2.3 ± 7.9 (0.4–4.3) .021 Mean of fat (HU) −101.3 ± 19.4 (−106.2 to −96.5) −98.9 ± 18.1 (−103.4 to −94.3) −2.5 ± 7.7 (−4.4 to −0.6) .012 SD of SVC (HU) 10.2 ± 4.5 (9.1–11.3) 13.7 ± 4.9 (12.5–14.9) −3.5 ± 2.8 (−4.2 to −2.8) <.001 SD of PM (HU) 8.5 ± 2.4 (7.9–9.1) 10.9 ± 2.9 (10.2–11.6) −2.4 ± 3.0 (−3.2 to −1.7) <.001 SD of air (BN) (HU) 32.1 ± 32.5 (23.9–40.2) 33.5 ± 30.5 (25.9–41.1) −1.4 ± 23 (−7.1–4.2) .61 SNR of PM 6.9 ± 8.1 (4.9–9.0) 3.9 ± 3.4 (3.0–4.7) 3.1 ± 6.4 (1.5–4.7) <.001 CNR of SVC and PM 4.9 ± 2.0 (4.4–5.4) 3.7 ± 1.6 (3.3–4.1) 1.2 ± 1.3 (0.9–1.5) <.001 Note:—IJV indicates internal jugular vein.
↵a Paired t test.
- Table 3:
Qualitative assessment of image quality, based on average ratings of 2 readers (N = 64 subjects)
MBIR ASiR Difference (MBIR-ASiR) Mean (95% CI) Mean (95% CI) Mean (95% CI) P Valuea Nasopharynx 4.80 ± 0.26 (4.74–4.87) 4.16 ± 0.31 (4.08–4.23) 0.65 ± 0.30 (0.57–0.72) <.001 Oropharynx 3.74 ± 0.60 (3.59–3.89) 3.08 ± 0.64 (2.92–3.24) 0.66 ± 0.37 (0.56–0.75) <.001 Vocal cord 3.73 ± 0.53 (3.59–3.86) 4.02 ± 0.37 (3.92–4.11) −0.29 ± 0.53 (−0.42 to −0.16) <.001 SC junction 3.41 ± 0.48 (3.29–3.53) 3.75 ± 0.25 (3.69–3.82) −0.34 ± 0.52 (−0.47 to −0.21) <.001 Overall IQ 3.85 ± 0.32 (3.77–3.93) 3.69 ± 0.28 (3.62–3.76) 0.17 ± 0.31 (0.09–0.24) <.001 Note:—SC indicates sternoclavicular; IQ, image quality.
↵a Wilcoxon signed ranked test.
