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Computed tomography (CT)

Current standard for rapidly diagnosing some of the more common structural pathologies that affect the neurosurgical patient perioperatively. With this convenience comes the potential for its overuse.

All head CT studies ordered by the UCLA Neurosurgery Department from August 15, 2011 through December 15, 2011, were prospectively studied. Variables collected included demographic information, diagnosis, surgical procedures, indication for CT, CT findings, and whether the study led to a documentable change in management.

There were 801 head CT studies ordered for the 462 patients who were admitted to the neurosurgical service. The authors identified 14 indications for ordering a head CT with the following probabilities of a positive finding: examination change (17/56, 30.3%), follow-up (4-6 hours after intracerebral hemorrhage; 16/126, 12.7%), CT angiography (11/30, 36.7%), routine postoperative imaging (6/126, 4.7%), postventriculostomy placement (4/62, 6.5%), immediately before (4/31, 12.9%) or after removal of (2/42, 4.8%) a ventriculostomy, surveillance (>24 hours after intracerebral hemorrhage or external ventricular drain placement) (3/66, 4.5%), headaches (2/8, 25%), ground level fall (1/8, 12.5%), intracranial pressure spikes (2/6, 33.3%), and delayed (6-24 hours after intracerebral hemorrhage; 1/25, 4%).

The probability of discovering a clinically significant finding varies widely for each of the listed study indications. This prospective analysis of all CT scans ordered at a single institution suggests that imaging studies obtained without a change in neurological status were unlikely to produce a positive finding, and even when there was a positive finding, it was extremely unlikely to result in any intervention 1).

Types

Overuse

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 2).

Also, up to 1 in 5 examinations are duplicates of previous examinations 3) , 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 a mindless repetition of established routine—because “that’s the way we do it here” 4) 5).


Increased use of computed tomography (CT) in children is concerning owing to the cancer risk from ionizing radiation, particularly in children younger than 2 years. A guardian report that a child is acting abnormally is a risk factor for clinically important traumatic brain injury (ciTBI) and may be a driving factor for CT use in the emergency department.

1)
Garrett MC, Bilgin-Freiert A, Bartels C, Everson R, Afsarmanesh N, Pouratian N. An evidence-based approach to the efficient use of computed tomography imaging in the neurosurgical patient. Neurosurgery. 2013 Aug;73(2):209-15; discussion 215-6. doi: 10.1227/01.neu.0000430328.25516.dd. PubMed PMID: 23632759.
2)
Miller RA, Sampson NR, Flynn JM. The prevalence of defensive orthopaedic imaging: a prospective practice audit in Pennsylvania. J Bone Joint Surg Am. 2012;94(3):e18.
3)
Yasaitis L, Fisher ES, Skinner JS, Chandra A. Hospital quality and intensity of spending: is there an association? Health Aff (Millwood). 2009;28(4):w566-w572.
4)
Aaron HJ. Waste, we know you are out there. N Engl J Med. 2008;359:1865-1867.
5)
Armao D, Elias J Jr, Semelka RC. Are we doing the right study? In: Semelka RC, Elias J Jr, eds. Health Care Reform in Radiology. Hoboken, NJ: John Wiley and Sons, Inc.; 2013:86-114.
computed_tomography.txt · Last modified: 2017/01/21 19:53 (external edit)