Differentiation of hemorrhage from iodinated contrast in different intracranial compartments using dual-energy head CT

Abstract

Background and purpose: Identification of ICH, particularly after ischemic stroke therapy, is important for guiding subsequent antithrombotic management and is often confounded by contrast staining or extravasations within intracerebral or extra-axial compartments. This study evaluates the accuracy of DECT in distinguishing ICH from iodinated contrast in patients who received contrast via IA or IV delivery.

Materials and methods: Forty patients who had received IA or IV contrast were evaluated using a DECT scanner at 80kV and 140kV to distinguish hyperdensities secondary to contrast staining or extravasation from those representing ICH. A 3-material decomposition algorithm was used to obtain virtual noncontrast images and iodine overlay images. Sensitivity, specificity, and accuracy of DECT in prospectively distinguishing intracranial contrast from hemorrhage within parenchymal, subarachnoid, extra-axial, intraventricular, and intra-arterial compartments were computed using routine clinical follow-up imaging as the standard of reference.

Results: A total of 148 foci of intracranial hyperattenuation were identified. Of these, 142 were correctly classified for the presence of hemorrhage by DECT. The sensitivity, specificity, and accuracy for identifying hemorrhage, depending on the compartment being considered, were 100%, 84.4%-100%, and 87.2%-100%, respectively. The only instances where DECT failed to correctly identify the source of hyperattenuation was in the presence of diffuse parenchymal calcification (n = 5) and a metallic streak artifact (n = 1).

Conclusion: After IA and/or IV contrast administration, DECT can accurately differentiate all types of ICH from iodinated contrast without employing any additional radiation.

Fig 1.

Intraparenchymal and subarachnoid foci of hyperattenuation due to iodinated contrast staining of infarcted brain parenchyma in a 78-year-old woman with recanalization of the right terminal internal carotid artery. A, Intraparenchymal hyperattenuation is seen in the right basal ganglia (arrow) and in the subarachnoid space (*) on the SE image. B, These foci correspond to areas of diffuse contrast staining on the iodine overlay image. C, VNC image shows an area of hypoattenuation related to the infarct (arrow). D, Follow-up NCCT demonstrates complete washout of the contrast in both locations.

Fig 2.

Left thalamic intraparenchymal hyperattenuation due to hemorrhage of uncertain etiology in a 51-year-old man referred for altered mental status. The patient underwent a dual energy CTA and MR imaging for further evaluation. A, SE image shows left thalamic intraparenchymal hyperattenuation without corresponding hyperattenuation on the iodine overlay image (B). C, The focus of hyperattenuation is well demonstrated on the VNC image. A 24-hour follow-up NCCT scan (D) demonstrates largely stable hyperattenuation in the left thalamus, with an increase in the surrounding edema, confirming the original diagnosis of intraparenchymal hemorrhage.

Fig 3.

Subarachnoid hyperattenuation due to contrast staining in a 79-year-old man treated endovascularly for an acute stroke in the right MCA territory. A, Diffuse hyperattenuation in the right Sylvian fissure (arrow) on the SE image corresponds to the hyperattenuation seen on the iodine overlay image (B). The lack of hyperattenuation on the VNC image (C) suggests contrast extravasation in the Sylvian fissure. This is confirmed by the near-complete washout of the hyperattenuation on the 24-hour follow-up NCCT (D).

Fig 4.

Subarachnoid hyperattenuation due to hemorrhage in a 64-year-old man. A, There are foci of sulcal hyperattenuation (arrows) on the SE image. B, No corresponding hyperattenuation is seen on the iodine overlay image. C, VNC image shows identical foci of sulcal hyperattenuation, suggesting subarachnoid hemorrhage that was confirmed by the 24-hour follow-up NCCT (D).

Fig 5.

Subarachnoid hyperattenuation due to mixed contrast and hemorrhage in a 65-year-old woman treated for an acute stroke in the left MCA territory. Diffuse sulcal hyperattenuation in bilateral cerebral hemispheres is seen on SE image (A) and iodine overlay image (B). There are scattered areas of subarachnoid hyperattenuation on the VNC image (C), likely representing superimposed hemorrhage. D, These areas of hemorrhage are confirmed on follow-up gradient-echo T2*-weighted MR imaging as areas of decreased signal intensity (arrows). Subsequent NCCT E, also demonstrated decrease in diffuse sulcal hyperattenuation, with patchy areas of persistent subarchnoid hyperattenuation (arrows).