Contrast-Enhanced Cranial Computed Tomography in Magnetic Resonance Imaging Era

Abstract

Objective: To evaluate the usefulness of intravenous contrast administration in cranial computed tomography (CT) in a general hospital with a magnetic resonance imaging (MRI) facility, and to establish a protocol to determine which patients would benefit most from using contrast-enhanced cranial CT. Subjects and Methods: Five hundred and forty-seven patients who underwent routine nonenhanced CT (NECT) and contrast-enhanced CT (CECT) of the brain between June 1997 and June 2001 were divided into three groups. Group A: 496 patients in whom CECT was done in spite of normal NECT; group B: 16 patients in whom CECT was considered necessary irrespective of NECT findings, and group C: 35 patients in whom NECT was abnormal and CECT was performed. Results: Contrast-enhanced cranial CT changed and/or confirmed the diagnosis in 1 of 496 in group A, 2 of 16 in group B, and 12 of 35 in group C, thereby indicating that CECT was useful in the diagnosis of groups B and C. Conclusion: CECT is unlikely to be useful in patients with normal NECT in the appropriate clinical setting. A protocol is presented for the use of contrast media in cranial CT in a general hospital with an MRI facility. Using this protocol only 9.7% of patients for cranial CT would have needed CECT, resulting in considerable cost savings without affecting the quality of the service to the patient in a general hospital.

The prevalence of undiagnosed abnormalities on non-contrast-enhanced computed tomography compared to contrast-enhanced computed tomography of the brain

“…3,6 Barrington et al regarded CECT as unhelpful if the NECT was normal. 7 Later studies by Chishti et al 1 and Huckman 2 demonstrated that pathology undiagnosed on NECT could subsequently be seen on CECT. Other authors suggested the use of contrast media in patients with normal NECT scans if there were focal clinical signs, 1,3,6 whilst some like Butler et al were of the opinion that a CECT on its own was as accurate as an NECT and a CECT combined.…”

“…7 Later studies by Chishti et al 1 and Huckman 2 demonstrated that pathology undiagnosed on NECT could subsequently be seen on CECT. Other authors suggested the use of contrast media in patients with normal NECT scans if there were focal clinical signs, 1,3,6 whilst some like Butler et al were of the opinion that a CECT on its own was as accurate as an NECT and a CECT combined. 8 We have to consider that improved CT scanners with better resolution may mean that increased pathology would be detected on the NECT and could eliminate the need for performing a CECT of the brain.…”

“…Magnetic resonance imaging (MRI) is the gold standard investigation for intracranial pathology, but is not widely available in developing countries. 1 Within the public health sector of South Africa, MRI is limited to a few tertiary institutions. Radiologists and clinicians in many centres must therefore rely on computed tomography (CT) of the brain as a first-line investigation for patients with suspected intracranial pathology.…”

“…1,2,3,4 Imaging characteristics, including enhancement patterns, have been described for various pathological conditions. 1,2,3,4,5 It is well recognised that vascular abnormalities and isodense lesions could be undiagnosed on NECT and that CECT may subsequently demonstrate these lesions. 2 A CECT can also confirm, change or shorten the differential diagnosis.…”

“…2 A CECT can also confirm, change or shorten the differential diagnosis. 1,3 Important factors to consider before subjecting patients to CECT are:…”