Experimental examination of videodensitometry of large opacifications in digital subtraction angiography

With the recent introduction of digital radiography the possibility of extracting clinically useful quantitative indices of function has emerged. In digital subtraction angiography (DSA), videodensitometric analysis has been widely applied. An experimental investigation of the usefulness of logarithmically transformed pixel values in DSA images for quantitative densitometry is performed. Dependence on image uniformity, transmittance, scattered radiation and video offset voltages is examined. Results indicate independence of both uniformity and transmittance and dependence on both scattered radiation and offset voltages. The possible use of lead absorbers to derive corrections for contributions from scattered radiation and similar aberrations in each image used for subtraction is also examined. Observations indicate that such corrections can allow accurate videodensitometry.