Quantitative angiography and flow characterization with a photo-diode array based x-ray imaging system

A digital x-ray imaging system for quantitative arterial imaging and blood flow characterization has been developed in the authors' laboratory and evaluated with a phantom study. The system consists of a low noise photo-diode array detector optically coupled to an x-ray image intensifier. The diode array can be considered as an ''add-on'' to an existing conventional XRII system to produce high quality images of small regions of interest selected from a larger field of view in fluoroscopy mode. X-ray collimation is used to reduce scatter and veiling glare to increase contrast, reduce a non-linear effect in logarithmically subtracted image, and minimize noise. Collimation to a 25 x 200 mm region of interest removes 80% of the scatter and 30% of the glare. Stenosis size (reduction of lumen area) in 13 cm of water is determined with a maximum uncertainty of 5% for iodine concentrations <33 mg/cm/sup 3/ using an 80 kVp beam. Scatter plus glare and beam hardening contribute equally to the residual error. Peak flow velocities are determined at positions along the arterial phantom with an uncertainty of 5-10% by detecting the movement of a small bolus of iodine with a temporal resolution of 5 ms. Areas of flow separation and turbulence are determined within 10-20% of theoretical positions