PURPOSE
Nowadays 4D-CTA is available as a non-invasive alternative to conventional angiography, with reported high diagnostic accuracy in the evaluation of different neurovascular disorders, including arteriovenous shunts and collateral flow pathways. Optimized processing of 4D-CTA is crucial, considering the large amount of data generated. Enhanced visualization of 4D-CTA can be achieved by applying color-mapping of temporal information in the cerebral vasculature.
METHOD AND MATERIALS
Color-mapping processing of 4D-CTA is achieved in two steps. First, the full cerebral vasculature is segmented by features extraction and random forest classification. Second, the color-scale is adjusted using the histogram using the histogram of the arrival times of the segmented vessels. Early contrast bolus arrival(e.g. healthy internal carotid artery) is labeled red, intermediate arrival yellow, and delayed contrast arrival is labeled blue.
Color-mapping of 4D-CTA was applied in patients suspected of cranial arteriovenous shunts, and in patients with unilateral carotid artery occlusion for the evaluation of circle of Willis collateral flow. The patients were scanned on a wide-row 320 slice detector CT (Toshiba Aquilion ONE), enabling whole-head coverage at high temporal resolution.
RESULTS
Arterialization of venous vascular structures is the hallmark of arterio-venous shunts, which is easily and accurately identified on color-mapping of 4D-CTA. Temporal dynamics of collateral flow in the circle of Willis is adequately depicted with 4D-CTA in patients with unilateral carotid artery occlusion.
CONCLUSION
Color-mapping of 4D-CTA accurately displays temporal information of the cerebral vasculature, which can facilitate the detection of arterio-venous shunts and the evaluation of collateral flow in intracranial steno-occlusive disease.