Automatic measurements of arterial input and venous output functions on cerebral computed tomography perfusion images: a preliminary study.

BACKGROUND: The current automatic techniques for measuring arterial input function (AIF) and venous output (VOF) on cerebral computed tomography perfusion images are prone to motion artifact and random noise, and their failure rates vary between 10% and 65%. We developed a new automatic technique to overcome these problems. METHODS: A principle axis transformation was applied to perfusion images to correct for translational and rotational motion artifacts. Bone voxels and neighboring voxels were removed from the perfusion images. Only brain voxels were included in the AIF and VOF measurement procedures. The selection criteria, such as large area under the concentration-time curve, early arrival of contrast agents, and narrow effective width, were used to select appropriate arterial and venous voxels for the AIF and VOF measurements. The proposed automatic technique was tested in 20 patients with unilateral cerebral arterial stenosis. The results of the proposed technique were compared to the results obtained by manual measurements and commercially available automatic selection software. RESULTS: The AIFs and VOFs were successfully measured using the proposed automatic technique in all 20 patients. The curve shapes, including the area under the concentration-time curve, peak concentration, time to peak, and effective width of the automatically measured AIFs or VOFs were comparable to that were measured manually. CONCLUSION: The proposed automatic measurement technique successfully overcomes the motion artifact and random noise problems encountered in measuring AIF and VOF. It can be easily integrated into software for the automatic calculation of cerebral blood volume and flow.

Transarterial Onyx embolization of intracranial dural arteriovenous fistulas: a single center experience.

BACKGROUND: Transarterial embolization of intracranial dural arteriovenous fistulas (DAVFs) is usually associated with inadequate embolization. The purpose of this study was to report our experience of transarterial Onyx embolization of intracranial DAVFs with an emphasis on treatment outcome with this new embolic agent in different types of DAVFs. METHODS: In the past 3 years, a total of 14 intracranial DAVFs have been treated by transarterial Onyx embolization. Among these, there were nine males and five females, aged from 30 years to 82 years (mean = 62 years). We retrospectively analyzed the injection volume and time of Onyx embolization as well as outcomes in different types of DAVFs. RESULTS: The locations of the DAVFs were sigmoid sinus (n = 6), tentorium (n = 3), sinus confluence (n = 2), transverse-sigmoid sinus (n = 1), sigmoid sinus-jugular bulb (n = 1) and the superior petrous sinus (n = 1). The mean volume and time of Onyx injection were 3.4 mL and 28 minutes, respectively (Cognard type I: 4.9 mL, 40 minutes; type II: 4.5 mL, 34 minutes; type III: 2.2 mL, 21 minutes; type IV: 2 mL, 22 minutes). Total fistula occlusion was achieved in six out of seven patients of type III and type IV DAVFs, and in four out of seven patients of type I and type II DAVFs. Nine patients had total resolution of their symptoms, whereas partial regression occurred in five patients. No significant periprocedural complication was found. Mean clinical follow-up period was 16 months. CONCLUSION: Transarterial Onyx embolization of intracranial DAVFs is safe and effective. This technique is particularly useful in type III and type IV DAVFs with a high cure rate, and lower volume of Onyx as well as a short injection time.

Intraprocedure aneurysm rupture in embolization: clinical outcome with imaging correlation.

BACKGROUND: Intraprocedural aneurysm rupture (IPAR) is the most feared complication of embolization for intracranial aneurysms. Here we report the immediate and long-term imaging outcomes of IPAR during embolization and the correlation with clinical outcomes. METHODS: Of the 376 consecutive patients harboring 412 intracranial aneurysms who had underwent endovascular coil embolizations in the past 9 years, 10 patients (2.7% per patient, 2.4% per aneurysm) had IPAR. There were two men and eight women, with an age range of 40-71 years (mean: 52 years). Imaging findings, including immediate cerebral angiography, brain computed tomography (CT), and follow-up CT, were analyzed. Final clinical patient outcome was evaluated by modified Rankin scale (mRS). RESULTS: The causes of the IPARs were coil protrusion (n=7), microcatheter perforation (n=2), or they were spontaneous (n=1). Nine cases involved previously ruptured aneurysms, while one was unruptured; aneurysmal location of the IPARs was the anterior (n=5) or posterior (n=4) communicating artery or the anterior cerebral artery (n=1). Angiographic cerebral hemodynamic compromise was observed in four patients and associated with poor clinical outcomes. Immediate CT showed contrast media and/or intracranial hemorrhage expansion in all the patients. Cerebral tissue loss due to ischemia and/or hemorrhagic occurred in six patients with more than 3 months of follow-up. On more than a 3-month clinical outcome, six patients presented with good recoveries (mRS: ≤ 2). One patient exhibited a moderate disability (mRS: 4), and three patients died (mRS: 6). CONCLUSION: IPAR is an uncommon complication and usually occurs during the advancement of the coil into the aneurysm sac. Angiographic hemodynamics is an important indicator to determine the outcome of the IPAR. Brain CT demonstrates the progression of the IPAR and the cerebral tissue loss resulting from ischemic or hemorrhagic events.

Dural sinus malformation with arteriovenous fistulae in a newborn: positive outcome following endovascular management.

Dural sinus malformation (DSM) is an extremely rare and congenital cerebrovascular malformation that is associated with dural arteriovenous fistula and a large dural lake, which may mimic the clinical malformations of an infantile dural arteriovenous shunt or the vein of Galen. Early diagnosis and treatment of DSM is crucial in order to avoid irreversible brain injuries or heart failure. Here, we report an unusual case of extensive DSM that showed good clinical and angiographic results after endovascular embolization.

Torticollis due to atlantoaxial rotatory fixation.

Torticollis due to atlantoaxial rotatory fixation (AARF) is rare. Most cases are idiopathic or occur after infection or minor trauma. AARF can cause neurologic deficits, and patients often present with torticollis that fails to resolve. AARF should be excluded before idiopathic spasmodic torticollis is diagnosed. Computed tomography helps in confirming AARF, and early diagnosis can improve outcomes, although treatment is debatable. We present three children and one adult with AARF and review the literature.

The Relationship between Carotid Artery Diameter and Percentage of Stenosis.

In order to understand percentage of stenosis from the residual lumen of the carotid artery, we explored the relationship between the residual diameter at the carotid stenosis, its stenosis percentage and the size of the internal carotid artery. Diameters of 103 carotid arteries of Taiwan residents were retrospectively measured from digital subtraction angiograms. Severe cases of near occlusion with the angiographic string sign, and cases with tandem lesions or intracranial occlusion were excluded. Of the total 103 carotid arteries, 22 (21%) had one or both of the following signs of reduced distal arterial caliber: (1) obvious narrowing of the distal carotid artery; (2) the caliber of the cervical internal carotid artery was smaller than the caliber of the corresponding external carotid artery. That the diameter of the distal carotid artery was smaller when the stenosis was greater at the site of minimal lumen was true in the group of patients with signs of reduced distal caliber and in the group of patients without such signs. Therefore, reduced distal caliber may be present in patients without such signs. After excluding cases with at least one of the above signs of reduced distal arterial caliber, the relation between percentage of stenosis (y) and the absolute value of the diameter at the stenosis (x) can be represented by the formula: y = 96.83-18.27 x. From our data, a diameter of 2 mm is about 60% stenosis and 1.5 mm is 70% stenosis. According to this formula, we can estimate percentage of carotid stenosis using residual diameter at the site of minimal lumen obtained from other imaging modalities, such as carotid Doppler, CT angiogram or MR angiogram.

Hemodynamic segmentation of MR brain perfusion images using independent component analysis, thresholding, and Bayesian estimation.

Dynamic-susceptibility-contrast MR perfusion imaging is a widely used imaging tool for in vivo study of cerebral blood perfusion. However, visualization of different hemodynamic compartments is less investigated. In this work, independent component analysis, thresholding, and Bayesian estimation were used to concurrently segment different tissues, i.e., artery, gray matter, white matter, vein and sinus, choroid plexus, and cerebral spinal fluid, with corresponding signal-time curves on perfusion images of five normal volunteers. Based on the spatiotemporal hemodynamics, sequential passages and microcirculation of contrast-agent particles in these tissues were decomposed and analyzed. Late and multiphasic perfusion, indicating the presence of contrast agents, was observed in the choroid plexus and the cerebral spinal fluid. An arterial input function was modeled using the concentration-time curve of the arterial area on the same slice, rather than remote slices, for the deconvolution calculation of relative cerebral blood flow.