Determinants of intracranial aneurysm retreatment following embolization with a single flow-diverting stent.

PURPOSE: Flow diverting stents have revolutionized the treatment of intracranial aneurysms through endoluminal reconstruction of the parent vessel. Despite this, certain aneurysms require retreatment. The purpose of this study was to identify clinical and radiologic determinants of aneurysm retreatment following flow diversion. METHODS: A multicenter flow diversion database was evaluated to identify patients presenting with an unruptured, previously untreated aneurysm with a minimum of 12 months' clinical and angiographic follow-up. Univariate and multivariate logistic regression modeling was performed to identify determinants of retreatment. RESULTS: We identified 189 aneurysms treated in 189 patients with a single flow-diverting stent. Mean age was 54 years, and 89% were female. Complete occlusion was achieved in 70.3% and 83.6% of patients at six and 12 months, respectively. Aneurysm retreatment with additional flow-diverting stents occurred in 5.8% of cases. Univariate analysis revealed that dome diameter ≥10 mm (p = 0.012), pre-clinoid internal carotid artery location (p = 0.012), distal > proximal parent vessel diameter (p = 0.042), and later dual antiplatelet therapy (DAPT) discontinuation (p < 0.001) were predictive of retreatment. Multivariate analysis identified discontinuation of DAPT >12 months (p = 0.003) as a strong determinant of retreatment with dome diameter ≥10 mm trending toward statistical significance (p = 0.064). Large aneurysm neck diameter, presence of aneurysm branch vessels, patient age, smoking history, and hypertension were not determinant of retreatment on multivariate analysis. CONCLUSIONS: Prolonged DAPT is the most important determinant of aneurysm retreatment following single-device flow diversion. Abbreviating DAPT duration to only six months should be a consideration in this population, especially for patients with a large aneurysm dome diameter.

Cause determination of missed lung nodules and impact of reader training and education: Simulation study with nodule insertion software.

BACKGROUND: There are "blind spots" on chest computed tomography (CT) where pulmonary nodules can easily be overlooked. The number of missed pulmonary nodules can be minimized by instituting a training program with particular focus on the depiction of nodules at blind spots. PURPOSE: The purpose of this study was to assess the variation in lung nodule detection in chest CT based on location, attenuation characteristics, and reader experience. MATERIALS AND METHODS: We selected 18 noncalcified lung nodules (6-8 mm) suspicious of primary and metastatic lung cancer with solid (n = 7), pure ground-glass (6), and part-solid ground-glass (5) attenuation from 12 chest CT scans. These nodules were randomly inserted in chest CT of 34 patients in lung hila, 1st costochondral junction, branching vessels, paramediastinal lungs, lung apices, juxta-diaphragm, and middle and outer thirds of the lungs. Two residents and two chest imaging clinical fellows evaluated the CT images twice, over a 4-month interval. Before the second reading session, the readers were trained and made aware of the potential blind spots. Chi-square test was used to assess statistical significance. RESULTS: Pretraining session: Fellows detected significantly more part-solid ground-glass nodules compared to residents (P = 0.008). A substantial number of nodules adjacent to branching vessels and posterior mediastinum were missed. Posttraining session: There was a significant increase in detectability independent of attenuation and location of nodules for all readers (P < 0.0008). CONCLUSION: Dedicated chest CT training improves detection of lung nodules, especially the part-solid ground-glass nodules. Detection of nodules adjacent to branching vessels and the posterior mediastinal lungs is difficult even for fellowship-trained radiologists.

Spatial Distribution of Intracranial Vessel Wall Enhancement in Hypertension and Primary Angiitis of the CNS.

We hypothesized a difference in the spatial distribution of intracranial vessel wall enhancement between CNS vasculitis and risk factors for intracranial atherosclerotic disease (ICAD). Fifty-five vessel wall MR imaging (VWI) exams were included in this retrospective observational study. Intracranial arteries were evaluated for vessel wall enhancement by branching pattern (e.g., primary, secondary, and tertiary segments). Demographic and laboratory data as well as ICAD risk factors, including a diagnosis of hypertension, were collected. A diagnosis of primary angiitis of the CNS (PACNS) was confirmed by biopsy or clinical assessment by a stroke neurologist. Univariate and multivariate Poisson regression models were fit for the outcomes. In multivariate analyses, hypertension showed significant associations with primary (ß = 1.31, 95% CI 0.78-1.88, p < 0.0001) and secondary (ß = 1.15, 95% CI 0.29-2.18, p = 0.05) segments, contrasting with PACNS which showed a distal spatial distribution with significant associations with secondary (ß = 0.77, 95% CI 0.14-1.39, p = 0.05) and tertiary (ß = 1.34, 95% CI 0.68-2.01, p < 0.0001) segments. Our results suggest the spatial distribution of vessel wall enhancement is an important consideration when interpreting VWI exams, particularly in patients with a comorbid diagnosis of hypertension. Given the global prevalence of hypertension, these results are impactful and may improve image interpretation of VWI in stroke patients.

Left Thalamus Arteriovenous Malformation Secondary to Radiation Therapy of Original Vermian Arteriovenous Malformation: Case Report.

A 70-year-old gentleman with history of hypothyroidism, hyperlipidemia, hypertension, and right superior cerebellar aneurysm presented to the neurosurgery service in 2008 with vertigo. Diagnostic cerebral angiography performed that year demonstrated a vermian arteriovenous malformations (AVM). The patient underwent stereotactic proton beam radiosurgery, which resulted in a decrease in flow and size of the lesion, and the patient was lost to follow-up. Now at the age of 80, the patient presented with acute gait instability. Cerebral angiogram demonstrated his stable vermian AVM and a new 1.1 cm AVM nidus in the region of the left posterior thalamus. Although AVMs are often described as congenital lesions, there is a growing body of literature suggesting that AVMs can grow, spontaneously regress, and even arise de novo in response to some insult. Understanding what leads to the growth, remodeling, regression, and hemorrhage of AVMs is crucial in order to better direct therapeutic endeavors. We would argue that this patient's AVM is secondary to endothelial cell damage from radiation therapy. Radiation can cause endothelial cell injury and upregulation of factors, such as vascular endothelial growth factor and transforming growth factor beta expression, which are implicated in AVM development pathways. We believe that this patient's new AVM is secondary to entrance radiation dosing affecting the thalamus during radiation therapy for the original vermian AVM.

LVIS Blue as a low porosity stent and coil adjuvant.

INTRODUCTION: The LVIS Blue is an FDA-approved stent with 28% metallic coverage that is indicated for use in conjunction with coil embolization for the treatment of intracranial aneurysms. Given a porosity similar to approved flow diverters and higher than currently available intracranial stents, we sought to evaluate the effectiveness of this device for the treatment of intracranial aneurysms. METHODS: We performed an observational single-center study to evaluate initial occlusion and occlusion at 6-month follow-up for patients treated with the LVIS Blue in conjunction with coil embolization at our institution using the modified Raymond-Roy classification (mRRC), where mRRC 1 indicates complete embolization, mRRC 2 persistent opacification of the aneurysm neck, mRRC 3a filling of the aneurysm dome within coil interstices, and mRRC 3b filling of the aneurysm dome. RESULTS: Sixteen aneurysms were treated with the LVIS Blue device in conjunction with coil embolization with 6-month angiographic follow-up. Aneurysms were treated throughout the intracranial circulation: five proximal internal carotid artery (ICA) (ophthalmic or communicating segments), two superior cerebellar artery, two ICA terminus, two anterior communicating artery, two distal middle cerebral artery, one posterior inferior cerebellar artery, and two basilar tip aneurysms. Post-procedurally, there was one mRRC 1 closure, five mRRC 2 closures, and 10 mRRC 3a or 3b occlusion. At follow-up, all the mRRC 1 and mRRC 3a closures, 85% of the mRRC 3b closures and 75% of the mRRC 2 closures were stable or improved to an mRRC 1 or 2 at follow-up. CONCLUSIONS: The LVIS Blue represents a safe option as a coil adjunct for endovascular embolization within both the proximal and distal anterior and posterior circulation.

Feasibility of in vivo imaging of fluorescent proteins using lifetime contrast.

We show that fluorescence lifetime is a powerful contrast mechanism that can enhance the whole-body imaging of fluorescent proteins (FPs), in the presence of background tissue autofluorescence (AF). The nonexponential AF decay is characterized from time-domain (TD) measurements on multiple nude mice and separated from the FP fluorescence using a linear fit to a priori basis functions. We illustrate this approach using an orthotopic mouse tumor model of breast adenocarcinoma. We also report that four commonly used FPs show distinct lifetimes, indicating their suitability for in vivo lifetime multiplexing. These results suggest the potential for exploiting fluorescence lifetime for imaging FPs for a variety of whole-body small-animal imaging applications.