Computed tomographic (CT) angiography is an important imaging modality for the detection of cerebral aneurysms, arterial stenosis, and other vascular anomalies in the intracranial arteries. This technique is less invasive that digital subtraction angiography (DSA) because it requires only intravenous instead of intraarterial injection of contrast material. It can be performed with a substantially shorter examination time with less risk to the patient. CT angiography provides important three-dimensional (3D) information, which can be used as a navigational tool by neurosurgeons and interventional neuroradiologists.
Source images from CT angiography are often displayed as maximum intensity projection (MIP) reconstructions to obtain angiographic images (1, 2). A drawback of the MIP technique is that, especially in the region of the skull base, extensive preprocessing is needed to remove the bone from the source images. Although some software tools are available to aid the operator in this task, preprocessing is time-consuming (2), and bone removal is often incomplete. This is especially the case in regions where arteries are contiguous with the bone, as in the petrous carotid region with its intricate mingling of bone and arteries (1). As a consequence, aneurysms at the skull base that arise from the intracavernous or supraclinoid carotid artery may be obscured by bone (3, 4), and the assessment of stenosis in the petrous portion of the carotid artery is poor (5).
We developed a method, matched bone mask elimination (MMBE), to eliminate the bone pixels from CT angiographic source images, to create artifact-free MIP images of the intracranial arteries. Although MMBE has some resemblance to subtraction, it is fundamentally different and has substantial advantages. Our purpose was to evaluate the results of a feasibility study in which the effectiveness of this approach was evaluated.