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BACKGROUND AND PURPOSE:Flat panel detector CT images are degraded by streak artifacts caused by radiodense implanted materials such as coils or clips. A new metal artifacts reduction prototype algorithm has been used to minimize these artifacts. The application of this new metal artifacts reduction algorithm was evaluated for flat panel detector CT imaging performed in a routine clinical setting.

Paralleling the rapid development of neuroimaging technology, the introduction of neuronavigation in the 1980s has revolutionized the surgery of intracranial diseases.2,11 Neuronavigation based on CT or MRI studies has tailored surgical interventions to individual anatomy and pathology, with minimal disruption to the physical and functional architecture of the brain. Vascular anatomy is best appreciated with digital subtraction angiography (DSA), which remains the gold standard for imaging of cerebrovascular pathology. Both CT angiography (CTA) and MR angiography (MRA) have lower detection sensitivity and inferior spatial resolution relative to DSA for aneurysms smaller than 3 mm. 1,19,20 The use of DS angiograms as source images for neuronavigation, however, has been limited because DSA studies typically lack the soft-tissue information necessary to register the radiographic image space to the head in the physical space. Images from DSA typically require fusion with CT or MR images for coregistration.Frameless neuronavigation based only on 3D digital subtraction angiography using surface-based facial registration Object. Cerebrovascular lesions can have complicated abnormal anatomy that is not completely characterized by CT or MR angiography. Although 3D rotational angiography provides superior spatial and temporal resolution, catheter angiograms are not easily registered to the patient, limiting the use of these images as a source for neuronavigation. However, 3D digital subtraction angiography (DSA) contains not only vascular anatomy but also facial surface anatomy data. The authors report a novel technique to register 3D DSA images by using only the surface anatomy contained within the data set without having to fuse the DSA image set to other imaging modalities or use fiducial markers.Methods. A cadaver model was first created to assess the accuracy of neuronavigation based on 3D DSA images registered by facial surface anatomy. A 3D DSA scan was obtained of a formalin-fixed cadaver head, with acquisitions of mask and contrast runs. The right common carotid artery was injected prior to the contrast run with a 45% contrast solution diluted with water-soluble red liquid latex. One week later, the head was registered to a neuronavigation system loaded with the 3D DSA images acquired earlier using facial surface anatomy. A right pterional craniotomy was performed and 10 different vascular landmarks were identified and measured for accuracy using the neuronavigation system. Neuronavigation based only on 3D DSA was then used to guide an open clipping procedure for a patient who presented with a ruptured distal lenticulostriate aneurysm.Results. The accuracy of the measurements for the cadaver model was 0.71 ± 0.25 mm (mean ± SE), which is superior to the 1.8-5 mm reported for neuronavigation. The 3D DSA-based navigation-assisted surgery for the distal lenticulostriate aneurysm aided in localization, resulting in a small craniotomy and minimal brain dissection.Conclusions. This is the first example of frameless neu...

Parenchymal blood volume (PBV) mapping with flat panel detectors may provide real-time estimates of tissue perfusion during endovascular ischemic stroke procedures. We present two cases of acute middle cerebral artery (MCA) occlusion to demonstrate how PBV may: (1) be used in acute stroke; (2) influence intraprocedural decision-making; and (3) potentially serve as a predicator of clinical outcome. Both cases were successfully recanalized with endovascular embolectomy. Intraprocedural PBV maps were obtained immediately before and after recanalization. Pre-intervention reductions in PBV were seen throughout the MCA territory in both cases, with significant improvement in PBV in one case with good radiographic and clinical outcome and a lack of improvement in PBV in the second case with a large infarct volume. PBV deficit normalization may occur with recanalization of the parent artery and probably represents successful reperfusion. Baseline PBV maps should therefore be interpreted with caution and not interpreted to represent irreversible core infarct.

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