More information can be mined from the routine PCA data

摘要

Phase contrast angiography (PCA) delineates the vasculature morphology based on the fact that the blood is flowing inside the vessels. And the source images of PCA have significantly less background signals than that of the tune of flight (TOF) MRA. Although the PCA scan requires a slightly longer acquisition time than that of the TOF, it contains a lot more information regarding to the flow direction and velocity of the blood. Unfortunately, all these are discarded except the signal enhancement due to flow when the resulting angiogram is reconstructed and displayed on a clinical MR machine. To reveal more information contained in the PCA a presentation scheme was developed, in which each pixel after the angiographic projection has assigned a color in addition to the intensity. Employing the concept similar to the three elemental color mixing, the directional information of flow can be conveyed in an easy to comprehend format. Using the maximum intensity projection (MIP) algorithm along the viewing trace, the pixel intensity value was obtained and signed to the corresponding pixel on the PP. The final pixel color is determined by the flow direction. To demonstrate the effectiveness of the method, we obtained a PC angiography data set (TR/TE/Flip = 20ms/3.9ms/20 degree) of the circle of Willis in transverse orientation from both normal volunteers and patient heads at 1.5T using Venc of 60 cm/sec. Results showed additional information can be gained from the PCA data, which may be useful for selected patients and sometimes crucial in the routine clinical diagnosis.