A method which does not require an online computer has been developed to measure left ventircular ejection fraction from a bolus of 99mTc-pertechnetate. The passage of the bolus through the cardiac chambers was imaged using a gamma camera and recorded on video tape. On replay a region of interest corresponding to the left ventricle was selected directly at the gamma camera console. Counts detected in this region were analysed in 30ms intervals. The data were corrected for the contribution from extra-cardiac activity and were then digitally filtered to remove statistical noise. Ejection fractions measured in 13 patients by this technique agreed well with those determined by contrast ventriculography (r=0.97, P less than 0.001).

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Two fundamental problems face any hospital or radiology department that is thinking about installing a Picture Archiving and Communications System (PACS).First, though the need for PACS already exists, much of the relevant technology is just beginning to be developed.Second, the requirements of each hospital are different, so that any attempts to market a single PACS design for use in large numbers of hospitals are likely to meet with the same problems as were experienced with general -purpose Hospital Information Systems.This paper outlines some of the decision processes involved in arriving at specifications for each module of a PACS and indicates design principles which should be followed in order to meet individual hospital requirements, while avoiding the danger of short -term systems obsolescence.