The limited resolution of any imaging system causes edge blurring of objects acquired with X-ray. In digital angiography, this effect combined with noise gives rise to systematic and random errors in the determination of vessel dimensions. The influence of bandwidth limitation on the estimation of tube diameter is established by a theoretical approach: it leads to over and underestimations of catheter and vessel diameter dimensions. Therefore a correction is proposed that counterbalances the point spread function (PSF) offset. The residual inaccuracy and the variability of measurement of phantom tubes are analyzed and evaluated in controlled conditions. Some of the parameters which govern their extent are identified: field-of-view, catheter size, concentration of contrast agent.