Subjective and objective comparisons of image quality between ultra-high-resolution CT and conventional area detector CT in phantoms and cadaveric human lungs

OBJECTIVES: To compare the image quality of the lungs between ultra-high-resolution CT (U-HRCT) and conventional area detector CT (AD-CT) images. METHODS: Image data of slit phantoms (0.35, 0.30, and 0.15 mm) and 11 cadaveric human lungs were acquired by both U-HRCT and AD-CT devices. U-HRCT images were obtained with three acquisition modes: normal mode (U-HRCT(N): 896 channels, 0.5 mm × 80 rows; 512 matrix), super-high-resolution mode (U-HRCT(SHR): 1792 channels, 0.25 mm × 160 rows; 1024 matrix), and volume mode (U-HRCT(SHR-VOL): non-helical acquisition with U-HRCT(SHR)). AD-CT images were obtained with the same conditions as U-HRCT(N). Three independent observers scored normal anatomical structures (vessels and bronchi), abnormal CT findings (faint nodules, solid nodules, ground-glass opacity, consolidation, emphysema, interlobular septal thickening, intralobular reticular opacities, bronchovascular bundle thickening, bronchiectasis, and honeycombing), noise, artifacts, and overall image quality on a 3-point scale (1 = worst, 2 = equal, 3 = best) compared with U-HRCT(N). Noise values were calculated quantitatively. RESULTS: U-HRCT could depict a 0.15-mm slit. Both U-HRCT(SHR) and U-HRCT(SHR-VOL) significantly improved visualization of normal anatomical structures and abnormal CT findings, except for intralobular reticular opacities and reduced artifacts, compared with AD-CT (p < 0.014). Visually, U-HRCT(SHR-VOL) has less noise than U-HRCT(SHR) and AD-CT (p < 0.00001). Quantitative noise values were significantly higher in the following order: U-HRCT(SHR) (mean, 30.41), U-HRCT(SHR-VOL) (26.84), AD-CT (16.03), and U-HRCT(N) (15.14) (p < 0.0001). U-HRCT(SHR) and U-HRCT(SHR-VOL) resulted in significantly higher overall image quality than AD-CT and were almost equal to U-HRCT(N) (p < 0.0001). CONCLUSIONS: Both U-HRCT(SHR) and U-HRCT(SHR-VOL) can provide higher image quality than AD-CT, while U-HRCT(SHR-VOL) was less noisy than U-HRCT(SHR). KEY POINTS: • Ultra-high-resolution CT (U-HRCT) can improve spatial resolution. • U-HRCT can reduce streak and dark band artifacts. • U-HRCT can provide higher image quality than conventional area detector CT. • In U-HRCT, the volume mode is less noisy than the super-high-resolution mode. • U-HRCT may provide more detailed information about the lung anatomy and pathology. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00330-018-5491-2) contains supplementary material, which is available to authorized users.