Multi-slice CT for visualization of pulmonary embolism using perfusion weighted color maps

Purpose: The purpose of our preliminary study was to evaluate the feasibili ty of a new technique for the perfusion weighted color display of the densi ty of lung parenchyma derived from multi-slice CT (MSCT) data sets of clini cal routine examinations for visualization of pulmonary embolism (PE). Mate rials and Methods: Imaging of patients with suspected PE was performed on a commercially available MSCT (Somatom Volume Zoom; Siemens, Forchheim, Germ any) after intravenous application of 120 cc of contrast-medium using a pow er injector. Scan parameters were 140 kV and 100 mAs, using a thin collimat ion of 4 x 1 mm and a table speed of 7 mm (pitch: 1.75). Derived from thin collimation axial slices (slice thickness(eff) 1.25 mm, reconstruction incr ement 0.8 mm), a new image processing technique was deployed. Based on thes e source images, an automated 3D-segmentation of the lungs was performed fo llowed by threshold based extraction of major airways and vascular structur es. The filtered volume data were color encoded and finally overlayed onto the original CT images. This color encoded display of parenchymal density d istribution of the lungs was shown in axial, coronal and sagittal plane ori entation. In four patients with excluded PE as well as in two patients with proven PE this new technique was performed. Results: In the four patients that were considered negative regarding PE on MSCT, lung densitometry showe d a homogeneous distribution of color encoded densities without circumscrib ed decreased or increased areas, beside the usually present gravity-depende nt gradient in ventro-dorsal direction. In the two patients with proven PE, low density values on perfusion weighted color maps were found distally to the occluded pulmonary arteries. Conclusions: Our initial experience indic ates that lung densitometry with an optimized display of the density distri bution within the lung parenchyma may provide additional information in pat ients with suspected or proven PE. However, a comparison with ventilation/p erfusion scintigraphy and a larger number of patients are necessary for the full clinical evaluation of this new functional imaging methodology.