Demonstration of postural effects and layering by cranial computed tomography.

The superb contrast resolution of computed tomography permits visualization of layering of fluid components of varying densities in tumors and hematomas which cannot be observed with conventional radiographic techniques. Layering confirms the fluid nature of a cystic tumor and suggests the possibility of draining the fluid contents in an effort to reduce mass effect. Verification of layering is achieved by noting shifting of the dependent material with axial rotation of the patient. While unusual, this finding is significant because solid tumors occasionally show low densities simulating fluid. The presence of layering of intraventricular of subdural blood implies that the blood is fluid rather than clotted and therefore removal by aspiration will be possible.