A system for evaluating a vessel of a current patient by utilizing a patient database of vessel flow data from a plurality of patients, comprising: - a processor configured to: obtain angiographic images of a vessel from each of the plurality of patients; collect anatomic vessel measurements for the vessel from each of the plurality of patients; store the anatomic vessel measurements for the vessel from each of the plurality of patients; determine an anatomical fractional flow reserve for the vessel from each of the plurality of patients; correlate the anatomical vessel measurements and the anatomical fractional flow reserve for the vessel from each of the plurality of patients; store the anatomical vessel measurements and the anatomical fractional flow reserve for the vessel from each of the plurality of patients as correlated data; associate a degree of error for each of a plurality of ranges of the stored fractional flow reserves based on the correlated data; determine a current degree of error for a calculated fractional flow reserve for the current patient and offset the calculated fractional flow reserve by an offset factor as a correction factor, said correction factor being the degree of error associated with that particular range of fractional flow reserve values that the calculated fractional flow reserve lies within; and - a display configured to: display the thus corrected fractional flow reserve value to a user. - a processor configured to: obtain angiographic images of a vessel from each of the plurality of patients; collect anatomic vessel measurements for the vessel from each of the plurality of patients; store the anatomic vessel measurements for the vessel from each of the plurality of patients; determine an anatomical fractional flow reserve for the vessel from each of the plurality of patients; correlate the anatomical vessel measurements and the anatomical fractional flow reserve for the vessel from each of the plurality of patients; store the anatomical vessel measurements and the anatomical fractional flow reserve for the vessel from each of the plurality of patients as correlated data; associate a degree of error for each of a plurality of ranges of the stored fractional flow reserves based on the correlated data; determine a current degree of error for a calculated fractional flow reserve for the current patient and offset the calculated fractional flow reserve by an offset factor as a correction factor, said correction factor being the degree of error associated with that particular range of fractional flow reserve values that the calculated fractional flow reserve lies within; and obtain angiographic images of a vessel from each of the plurality of patients; collect anatomic vessel measurements for the vessel from each of the plurality of patients; store the anatomic vessel measurements for the vessel from each of the plurality of patients; determine an anatomical fractional flow reserve for the vessel from each of the plurality of patients; correlate the anatomical vessel measurements and the anatomical fractional flow reserve for the vessel from each of the plurality of patients; store the anatomical vessel measurements and the anatomical fractional flow reserve for the vessel from each of the plurality of patients as correlated data; associate a degree of error for each of a plurality of ranges of the stored fractional flow reserves based on the correlated data; determine a current degree of error for a calculated fractional flow reserve for the current patient and offset the calculated fractional flow reserve by an offset factor as a correction factor, said correction factor being the degree of error associated with that particular range of fractional flow reserve values that the calculated fractional flow reserve lies within; and - a display configured to: display the thus corrected fractional flow reserve value to a user.