Fig. 1. Time-window criteria.

The time window criteria in our study were defined as follows: 1) the time interval between the first and last contrast medium administrations was within 48 hours; 2) no other contrast medium study was performed within 72 hours before the first contrast medium administration; and 3) no other contrast medium study was performed 72 hours after the last contrast medium injection. The first and the last contrast medium administrations represent the same examination if the patient did not undergo repeat contrast injections (i.e., single dose). Minimum repeat interval applies only when the patient underwent multiple contrast injections in the time window of interest. It is defined as the shortest interval of any adjacent contrast medium injections. CE = contrast-enhanced