Unregistered subtracted CT angiography for the visualization of intracranial arteries at or near the skull base: preliminary experience

PURPOSE: Restrictions with computed tomography angiography (CTA) regarding the visualization of arteries near the skull base are well known. Today, the gold standard for overcoming this is the matched mask bone elimination method. Worldwide use of this method is limited since it requires advanced imaging physics and software. A more simple method was introduced recently that avoided motion artifacts significantly by restraining the patient's head with a vacuum-type head holder. The purpose of this study was to investigate the feasibility of using unregistered subtracted CTA without such head-holding methods. MATERIALS AND METHODS: Of the 42 patients that underwent subtracted CTA, 39 were recruited for this study. Two patients were excluded due to agitation during examination and one due to artifacts of an embolized aneurysm. All the examinations were performed in an 8-channel multidetector CT suite. After performing a non-contrast low-dose CT examination, CTA was carried out using the same scan planes as on the scout images. Images were transferred to a workstation and subtraction was performed. Hard-copy images through identical locations were reviewed by 2 observers, a radiologist and a clinician (neurologist), and visualization of the internal carotid artery and posterior artery systems were scored. Data were analyzed using the Wilcoxon signed-rank test. RESULTS: Significant statistical differences, in favor of subtracted images, were noted in both observers' scores, both for the internal carotid artery and posterior system arteries. The differences in the clinician's scores were more prominent than that of radiologist's. CONCLUSION: These results are promising for the expanded use of the subtraction method, especially in radiology departments that lack the staff and equipment for registered methods.