OBJECTIVE: The purposes of this study were to evaluate the quality of coronal reformatted images obtained from volumetric expiratory high-resolution CT imaging and to compare coronal and axial images with regard to their usefulness in detecting and characterizing air trapping.
SUBJECTS AND METHODS: We studied 40 consecutive patients with known or suspected diffuse lung diseases with airway abnormalities who underwent volumetric expiratory high-resolution CT between May and July 2003. Respiratory motion artifacts were evaluated at upper, middle, and lower lung areas. Cardiac motion, beam-hardening, and other artifacts were evaluated throughout the lung fields. Detectability, clarity of borders, size, distribution, and extent of air trapping were compared on axial versus coronal end-expiratory high-resolution CT images.
RESULTS: Respiratory motion artifacts were either imperceptible or not diagnostically limiting in all patients except three (7%) with diagnostically limiting image degradation at lower lung areas. Other diagnostically limiting image degradation was caused by beam-hardening artifacts in two patients (5%) and by quantum noise in two other patients (5%). The borders of air trapping were more clearly identified on coronal images than on axial images (grade 1 [vague], nine vs three; grade 2 [partially clear], 23 vs 21; grade 3 [completely clear], eight vs 16; median, two vs two;p = 0.001). The coronal reformatted images were as informative as axial images for detecting and assessing the classification and extent of air trapping.
CONCLUSION: Coronal reformations of volumetric expiratory high-resolution CT scans were acceptable in image quality and provided additional value by affording clearer visualization of the borders of air trapping than was found in contiguous axial images.