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: 896 channels, 0.5 mm × 80 rows; 512 matrix), super-high-resolution mode (U-HRCT: 1792 channels, 0.25 mm × 160 rows; 1024 matrix), and volume mode (U-HRCT: non-helical acquisition with U-HRCT). AD-CT images were obtained with the same conditions as U-HRCT. 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. Noise values were calculated quantitatively.

Results: U-HRCT could depict a 0.15-mm slit. Both U-HRCT and U-HRCT 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 has less noise than U-HRCT and AD-CT (p < 0.00001). Quantitative noise values were significantly higher in the following order: U-HRCT (mean, 30.41), U-HRCT (26.84), AD-CT (16.03), and U-HRCT (15.14) (p < 0.0001). U-HRCT and U-HRCT resulted in significantly higher overall image quality than AD-CT and were almost equal to U-HRCT (p < 0.0001).

Conclusions: Both U-HRCT and U-HRCT can provide higher image quality than AD-CT, while U-HRCT was less noisy than U-HRCT.

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.