3-DIMENSIONAL HELICAL CT OF INTRAHEPATIC VENOUS STRUCTURES - COMPARISON OF 3 RENDERING TECHNIQUES

Objective: To define the advantages and disadvantages of various rende ring techniques to obtain three-dimensional (3D) displays of intrahepa tic venous structures with helical CT data. Materials and Methods: Aft er rapid preprocessing segmentation of the liver, helical CT data (8 m m slice thickness overlapped every 4 mm) from 10 patients were reconst ructed using maximum intensity projection (MIP), volume rendering, and surface rendering algorithms. Three-dimensional imaging was evaluated blindly and independently by three observers for presence of artifact s and overall quality. Results: Three-dimensional displays showed the hepatic veins and fifth order portal branches with the volume and MIP rendering techniques. Best overall quality in the 3D representation of the liver was achieved with the MIP technique (p < 0.05). Small detai ls in venous anatomy and portal involvement by tumor were better image d with the MIP technique. ''Stair-step'' artifacts markedly degraded t he 3D displays obtained with the surface rendering technique, making i t inappropriate for imaging the intrahepatic venous structures. Conclu sion: Maximum intensity projection appears to be an adequate technique to perform 3D imaging of intrahepatic venous structures with helical CT data when 8 mm slice thicknesses overlapping every 4 mm are used. H owever, optimization of imaging protocols needs to be done and compare d in a larger series.