Abnormalities of the diaphragm and adjacent structures: findings on multiplanar spiral CT scans.

Abnormalities of the diaphragm and surrounding tissues have been notoriously difficult to image with conventional axial CT. During the past 10 years, the multiplanar imaging capabilities of MR have been used to clarify the organ of origin of masses near the diaphragm. Spiral CT now offers a similar capability. With spiral CT, the peri-diaphragmatic region can be scanned in a single breath-hold, minimizing motion artifacts and virtually eliminating respiratory mis-registration. Axial images of closely spaced, overlapping sections are reconstructed retrospectively from the volumetric spiral CT projection data set. From these images, one can generate high-detail multiplanar reformations through the diaphragm and adjacent abnormalities. As the CT attenuation values inherent to the chest and abdomen cover a wide range, three-dimensional reformations are not expected to depict this anatomy better than two-dimensional reformations can. This is because three-dimensional images generally render structures at the extremes of CT attenuation, or within a narrow window of CT attenuation values. This pictorial essay illustrates the importance of two-dimensional sagittal and coronal reformations of spiral CT scans in evaluating the peri-diaphragmatic area. With these reformations, peri-diaphragmatic abnormalities seen on axial images are localized to the lung, pleura, pericardium, cardiophrenic space, or intraabdominal viscera.