“…In this report, the rate of positive abnormal finding on plain head CT was 4.6% and the rate of CT needed to change treatment plans was 0.9% among 2,943 plain head CT scans performed. The incidence of overlooking head CT scan findings in particular was low maybe because the incidence of abnormal findings on head CT is originally low 10–16 . Further studies, for instance, on how many orders of CT or MRI can be reduced or what kind of clinical improvements is achieved by changing examinations, are expected.…”