There are many reasons for overutilization: A clinician may order scans because he or she lacks knowledge or support regarding the appropriate application of diagnostic imaging, because of patient demand, or due to intolerance of diagnostic uncertainty. Technical advances have also expanded the clinical applications of imaging, even when there is no evidence base for such uses. Some physicians order imaging tests because they are practicing defensive medicine, which is believed to account for up to 1 in 5 CT examinations 1).
Also, up to 1 in 5 examinations are duplicates of previous examinations 2) , which are repeated either because the earlier scan is inaccessible or because the physician is unaware it had been performed. Imaging may be used as a surrogate for physical examination, particularly in the emergency department, or imaging may be motivated by self-referral or by radiologists’ recommendations for repeat studies. Finally, sometimes scans are ordered because of mindless repetition of established routine—because “that’s the way we do it here” 3) 4).