Comparison of film, hard copy computed radiography (CR) and soft copy picture archiving and communication (PACS) systems using a contrast detail testobject

This paper describes two experiments where a widely available test object ( FAXIL TO20) was used to compare film, hard copy computed radiography (CR) a nd soft copy picture archiving and communication systems (PACS) images. Bas eline images were produced with. a fixed mAs. All images were scored by fou r experienced medical physicists. Contrast detail curves for the three type s of images were almost identical. A second series of images was produced w ith the mAs varying from 1 mAs to 250 mAs. The contrast detail curves were plotted for each mAs value and the wider exposure latitude of CR compared w ith film was demonstrated. Use of PACS provided no further increase in expo sure latitude. The density of the film images increased with mAs but the de nsity of the CR hard copy images remained constant. It is of concern that t he wider latitude of the CR images extends to exposures that are much highe r than those used for film with no noticeable change in CR image density bu t with better images at higher exposures, because the potential exists for patient doses to increase. Hard copy CR images provide information about th e exposure index which relates to the input dose to the plate and hence app roximately to the dose to the patient. However, since such information is c urrently not available on default soft copy images, the authors suggest tha t all manufacturers of PACS should provide an indication of dose as a manda tory default setting.