LVIS-within-enterprise double-stent procedure without coiling beneficial as treatment of unruptured vertebral artery dissecting aneurysms.

Stenting of vertebral artery dissecting aneurysms (VADAs) may promote mural apposition of intimal flaps, preserving the patency of injured vessels. Moreover, stent deployment may serve to alter intra-aneurysm flow, inducing saccular thrombus formation, neointimal development, and remodeling of injured vessels. Although an overlapping multistent strategy with coiling has proven successful in this setting, yielding good anatomic and clinical outcomes, coiling may be technically infeasible in some VADAs with unfavorably configured circumferential elevations. Herein, we describe three patients with VADAs for whom coiling was deemed technically problematic. Each underwent double stenting (LVIS within Enterprise), without coil insertion, using local anesthesia. Conventional angiographic follow-up regularly disclosed excellent saccular occlusion and subsequent remodeling of stented arteries. LVIS-within-Enterprise double stenting may be of particular benefit in patients with VADAs, the Enterprise providing outer support to minimize stent bulging (as a fusiform aneurysm) as the inner LVIS reinforces flow diversion.

Endovascular Treatment of Fenestration-related Aneurysms : Morphological Features, Operative Techniques and Therapeutic Outcomes.

PURPOSE: Endovascular treatment of fenestration-related aneurysms (FAs) is prone to technical challenges, given the inherent complexities. Herein, we have analyzed FAs in terms of angioarchitectural characteristics and outcomes achieved through endovascular intervention. METHODS: Data accrued prospectively between January 2002 and July 2020 were productive of 105 FAs in 103 patients, each classifiable by the nature of incorporated vasculature as proximal portion, fenestrated limb, or distal end. Our investigation focused on clinical and morphological outcomes, with emphasis on technical aspects of treatment. RESULTS: The FAs selected for study originated primarily in anterior communicating artery (AcomA: 88/105, 83.8%), followed by basilar (7/105, 6.7%), anterior cerebral (4/105, 3.8%), and internal carotid (3/105, 2.8%) arteries. In nearly all locations, proximally situated aneurysms (43/105, 41%) were more frequent than aneurysms arising at distal ends (3/105, 2.8%), but the majority of AcomA lesions involved fenestrated segments (58/88, 65.9%); and most fenestrated channels (90/105, 85.7%) were asymmetric in size. Orifices of smaller fenestrated limbs were intentionally compromised during coil embolization in 23 aneurysms (21.9%), achieving complete (n = 19) or incomplete (n = 4) compromise, without resultant symptomatic ischemia. Saccular occlusion proved satisfactory in 77 lesions (73.3%). In follow-up monitoring of 100 patients for a mean period of 35.3 ± 26.5 months, 17 instances of recanalization (17.0%) occurred (minor, 9; major, 8). There was no recanalization of aneurysms with compromised limbs. CONCLUSION: Coil embolization of FAs is safe and effective, enabling tailored procedures that accommodate aberrant angioanatomic configurations. Compromise of a single limb during coiling also appears safe, conferring long-term protection from recanalization.

Endovascular Treatment of Intracranial Kissing Aneurysms: Technical Feasibility and Clinical Outcomes.

BACKGROUND: Kissing aneurysms are situated on the same artery but have separate points of origin. Open surgical strategies for access from opposing directions may be technically problematic. Recent advances in protective devices and coiling techniques have compelled the present study, aimed at technical aspects and procedural outcomes of coil embolization in this setting. METHODS: Data prospectively accruing between May 2001 and May 2020 were systematically reviewed, assessing clinical and morphologic outcomes of coil embolization in 36 patients with 72 kissing aneurysms. RESULTS: Lesions most often involved paraclinoid internal carotid artery (n = 22), followed by anterior communicating artery (n = 7). Single-stage coil embolization of both aneurysms took place in nearly all patients (n = 35). Microcatheter tips for selecting paired aneurysms were usually directed opposite to one another (32 of 36, 88.9%), applying protective devices (i.e., balloons or stents) to 1 or both aneurysms in 21 patients (58.3%). Balloons were placed in 9 patients, often when treating first aneurysms and largely for second aneurysms as well (7 of 9, 77.8%). Stents deployed in 14 patients involved first and second aneurysms equally. Two patients required balloon of stent combinations. No procedure-related morbidity or mortality resulted. In follow-up of 68 aneurysms (mean: 40.2 ± 28.1 months) after coiling, 86.8% (59 of 68) showed sustained complete saccular occlusion. CONCLUSIONS: Strategies for endovascular treatment of kissing aneurysms rely heavily on characteristics that the paired aneurysms display. Properly conducted single-stage coil embolization is a safe and effective method of treating such lesions.

Treatment strategy to maximize the treatment outcome of spinal dural arteriovenous fistula after initial endovascular embolization attempt at diagnostic angiography.

Initial attempt of endovascular treatment (EVT) for spinal dural arteriovenous fistula (SDAVF) is preferred because of concurrent diagnosis and treatment. However, outcomes following further treatment with initial EVT are not well studied. We retrospectively reviewed 71 patients with SDAVF to evaluate treatment outcomes of SDAVF after an initial EVT attempt. Pretreatment and posttreatment functional states were assessed by the Aminoff-Logue scale (ALS). In the case of incomplete occlusion or recurrence, overall outcomes after further treatments were compared. Of the 71 patients, 56 underwent initial EVT. Complete occlusion was achieved by initial EVT in 37 of 56 patients (66.1%). Multiple feeders were more frequently observed in patients with incomplete occlusion than complete occlusion after initial EVT (73.7% vs. 27%, P < 0.001). Among 19 patients with incomplete occlusion upon initial EVT, 14 underwent additional surgery, 13 of whom (92.9%) obtained improved or stationary functional outcomes. Functional improvement was not observed in patients who had repeated EVT or follow-up without further treatment. Recurrence was observed in 8 of 37 patients with complete occlusion upon initial EVT. Additional surgery achieved improved functional outcomes in cases of incomplete occlusion of SDAVF after the initial EVT attempt or recurrence rather than repeated EVT or follow-up.

Delayed Progression to Major Recanalization in Coiled Aneurysms with Minor Recanalization at 36-Month Follow-up : Incidence and Related Risk Factors.

PURPOSE: The aim was to monitor aneurysms that show imaging evidence of minor recanalization 36 months after coil embolization and to determine the rate and related risk factors of major recanalization during more prolonged observation. METHODS: A total of 54 patients with 55 aneurysms showing minor recanalization at 36-month follow-up imaging between 2011 and 2013 were retrospectively reviewed. Medical records and radiological data accumulating in the course of extended monitoring (mean 83.9 ± 21.5 months) were assessed. Incidence and average annual risk of progression to major recanalization were then calculated. Univariate and multivariate regression analyses were applied to determine possible risk factors for progression to major recanalization. RESULTS: In the 55 aneurysms studied 26 showed sustained minor recanalization since month 6 of follow-up, whereas minor recanalization of 29 completely occluded coiled lesions appeared in follow-up images after 6-24 months. Only 8 coiled aneurysms (14.5%) with minor recanalization at 36 months progressed to major recanalization during 219.3 aneurysm-years of observation (3.6% per aneurysm-year), 2 surfacing within 72 months and 6 developing thereafter. Additional embolization was performed in six of these patients. By multivariate analysis, no clinical or anatomic factors were statistically linked to such progression, but younger age showed marginal significance (hazard ratio, HR = 1.076; p = 0.099). CONCLUSION: Most coiled aneurysms (85.5%) showing minor recanalization at 36 months postembolization proved to be stable in extended observation. Given the low probability but seriousness of delayed major recanalization, careful monitoring is still warranted in this setting but at less frequent intervals (every 2-3 years) beyond 36 months.

Does Systemic Hypertension Impact Recanalization of Coiled Aneurysms?

PURPOSE: It is well known that hypertension is a significant factor in the formation, growth, and rupture of aneurysms and recanalization of coiled aneurysms is affected by hemodynamic stress. At present, however, the impact of hypertension on recanalization of coiled aneurysms has not been adequately investigated. This study examined the relation between hypertension and subsequent outcomes of coiled aneurysms, using a matched patient analysis. METHODS: A total of 715 subjects undergoing coil embolization of intracranial aneurysms between 2011 and 2013 were selected for study. Time-of-flight magnetic resonance or conventional angiography was used (singly or together) to gauge degrees of occlusion after coiling, applying the Raymond classification in grading recanalization. Patients with hypertension were grouped as controlled or uncontrolled, based on blood pressure readings at outpatient clinics. Hypertensive and non-hypertensive subjects were matched (1:1) for several relevant variables. RESULTS: Overall, 484 patients (67.7%) were hypertensive (controlled 338; uncontrolled 146). During the follow-up period (28.6 ± 9.7 months), 129 aneurysms (18.0%) displayed recanalization (minor 58; major 71). Patient age, concomitant diabetes, hyperlipidemia, aneurysm size, neck size, depth-to-neck ratio, and aneurysm type differed significantly in hypertensive and non-hypertensive groups; however, group incidences of cumulative recanalization were similar (p = 0.297). After 1:1 matching the cumulative recanalization rate (13.5%) in hypertensive and non-hypertensive counterparts (14.3%) again proved similar (p = 0.578). In the hypertensive group, in addition, recanalization showed no relation to controlled and uncontrolled subgroup (odds ratio, OR = 1.000, p > 0.999). CONCLUSION: Unlike other aspects of evolving aneurysms (e.g. formation, growth, or rupture), recanalization of coiled aneurysms seems to be unaffected by systemic hypertension.

Retrograde stenting through anterior communicating artery in coil embolization of the posterior communicating artery aneurysm: contralateral approach.

During coil embolization of wide-necked posterior communicating artery (PcomA) aneurysms, stent assistance is sometimes limited if PcomA is acutely angled at its origins from saccular neck. Herein, we present two instances where retrograde stenting was used for coil embolization of PcomA aneurysms. Both procedures involved a contralateral approach via anterior communicating artery (AcomA). To achieve this, the stent-delivery microcatheter was inserted retrograde from contralateral to ipsilateral internal carotid artery (ICA) across AcomA, arriving at ipsilateral PcomA. A separate microcatheter, passed through ipsilateral ICA, was then used to select the aneurysm sac for coil delivery. Coil embolization ultimately took place under protection of a horizontally placed stent extending from PcomA to terminal ICA. Each aneurysm was properly coiled and occluded, without procedural complications. This stenting technique is a reasonable option, offering a means of strategic coil embolization in wide-necked PcomA aneurysms and providing complete neck coverage through contralateral access.

[Endovascular Treatment of Cerebral Aneurysms: Technical Options in Coil Embolization]. / 뇌동맥류의 혈관 내 치료: ì½”ì¼ìƒ‰ì „ìˆ ì˜ ê¸°ìˆ ì  ì„ íƒ.

Since the endosaccular coil embolization technique was introduced as an alternative for treating selected patients with aneurysms, it has become a mainstay of treatment for cerebral aneurysms. In lesions with a neck larger than the aneurysmal body, an irregular shape, or arterial branches incorporated within the sac, endovascular treatment using detachable coils are traditionally contraindicated because of technical difficulties. Coil embolization has evolved as a result of both the development of related devices and the introduction of technical improvements using various devices. Use of various technical and device options can make endovascular treatment of cerebral aneurysms safer and can widen the treatment indications. Various technical options, including the technical modification of device-assisted techniques, will be presented, and the related practical points will be discussed in this issue.

Healing of Aneurysm after Treatment Using Flow Diverter Stent : Histopathological Study in Experimental Canine Carotid Side Wall Aneurysm.

OBJECTIVE: Despite widespread use of flow diverters (FDs) to treat aneurysms, the exact healing mechanism associated with FDs remains poorly understood. We aim to describe the healing process of aneurysms treated using FDs by demonstrating the histopathologic progression in a canine aneurysm model. METHODS: Twenty-one side wall aneurysms were created in common carotid artery of eight dogs and treated with two different FDs. Angiographic follow-ups were done immediately after placement of the device, 4 weeks and 12 weeks. At last follow-up, the aneurysm and the device-implanted parent artery were harvested. RESULTS: Histopathologic findings of aneurysms at 4 weeks follow-up showed intra-aneurysm thrombus formation in laminating fashion, and neointimal thickening at the mid-segment of aneurysm. However, there are inhomogenous findings in aneurysms treated with the same type of FD showing same angiographic outcomes. At 12 weeks, aneurysms of complete and near-complete occlusion revealed markedly shrunken aneurysm filled with organized connective tissues with thin neointima. Aneurysms of incomplete occlusion at 12 weeks showed small amount of organized thrombus around fringe neck and large empty space with thick neointmal formation. Neointimal thickness and diameter stenosis was not significantly different between the groups of FD specification and follow-up period. CONCLUSION: Intra-aneurysmal thrombus formation and organization seem to be an important factor for the complete occlusion of aneurysms treated using the FD. Neointimal formation could occur along the struts of the FD independently of intra-aneurysmal thrombus formation. However, neointimal formation could not solely lead to complete aneurysm healing.

Symptomatic Retinal Artery Occlusion after Angioplasty and Stenting of the Carotid Artery: Incidence and Related Risk Factors.

OBJECTIVE: Retinal artery occlusion (RAO) is rarely seen as a complication in patients undergoing carotid artery stenting (CAS); hence, its characteristics have not been documented in detail. This study aimed to investigate the incidence of this complication and the related risk factors, focusing on differences in ophthalmic artery (OA) supply (whether by the external or internal carotid artery [ECA or ICA]) prior to CAS procedures. MATERIALS AND METHODS: We retrospectively examined 342 patients who underwent CAS for severe and/or symptomatic carotid artery stenosis between January 2009 and December 2017. Cumulative medical records and radiologic data were assessed. RAO was confirmed by photography and fluorescent angiography of the fundus, which were performed by an ophthalmologist. In all patients, distal filter systems of various types were applied as cerebral protection devices (CPDs) during procedures. Univariate and multivariate analyses were conducted to identify the risk factors for RAO after CAS. RESULTS: Symptomatic RAO was observed in six patients (1.8%), of which five (6.8%) were ECA-dominant group members (n = 74). In a binary logistic regression analysis, OA supply by the ECA (odds ratio [OR], 9.705; 95% confidence interval [CI], 1.519-62.017; p = 0.016) and older age (OR, 1.159; 95% CI, 1.005-1.336; p = 0.041) were identified as significant risk factors in patients with RAO after CAS. ECA-supplied OA was also associated with the severity of ipsilateral ICA stenosis (p = 0.001) and ulcerative plaque (p = 0.021). CONCLUSION: In procedures performed using ICA distal filtering CPD systems, RAO as a complication of CAS (performed for severe stenosis) showed a relationship to ECA-supplied OA. For older patients, simultaneous use of ICA-ECA CPDs might help prevent such complications.

Is 3 years adequate for tracking completely occluded coiled aneurysms?

OBJECTIVE: The authors conducted a study to ascertain the long-term durability of coiled aneurysms completely occluded at 36 months' follow-up given the potential for delayed recanalization. METHODS: In this retrospective review, the authors examined 299 patients with 339 aneurysms, all shown to be completely occluded at 36 months on follow-up images obtained between 2011 and 2013. Medical records and radiological data acquired during the extended monitoring period (mean 74.3 ± 22.5 months) were retrieved, and the authors analyzed the incidence of (including mean annual risk) and risk factors for delayed recanalization. RESULTS: A total of 5 coiled aneurysms (1.5%) occluded completely at 36 months showed recanalization (0.46% per aneurysm-year) during the long-term surveillance period (1081.9 aneurysm-years), 2 surfacing within 60 months and 3 developing thereafter. Four showed minor recanalization, with only one instance of major recanalization. The latter involved the posterior communicating artery as an apparent de novo lesion, arising at the neck of a firmly coiled sac, and was unrelated to coil compaction or growth. Additional embolization was undertaken. In a multivariate analysis, a second embolization for a recurrent aneurysm (HR = 22.088, p = 0.003) independently correlated with delayed recanalization. CONCLUSIONS: Almost all coiled aneurysms (98.5%) showing complete occlusion at 36 months postembolization proved to be stable during extended observation. However, recurrent aneurysms were predisposed to delayed recanalization. Given the low probability yet seriousness of delayed recanalization and the possibility of de novo aneurysm formation, careful monitoring may be still considered in this setting but at less frequent intervals beyond 36 months.

Determination of Aneurysm Volume Critical for Stability After Coil Embolization: A Retrospective Study of 3530 Aneurysms.

BACKGROUND: Recurrence is one of the concerns even after successful endovascular treatment of intracranial aneurysms. We sought to determine the critical aneurysm volume and risk factors related to aneurysmal stability in patients undergoing coil embolization of intracranial aneurysms. METHODS: Aneurysm volume and follow-up imaging data were retrieved in 3042 patients with 3530 aneurysms who were treated with endovascular coil embolization from January 2006 to October 2016. We analyzed the anatomic outcome in relation to aneurysm volume and determined the critical aneurysm volume favoring coil embolization. RESULTS: Recanalization rates were 2.8%, 6.3%, 19.4%, and 67.4% in each group with aneurysm volume of <10, 10-100, 100-1000, and >1000 mm3, respectively. When we investigated the 100-1000 mm3 group, the recanalization rate remarkably increased at 500 mm3 (16.4% vs. 57.5%, P < 0.0001; odds ratio [OR], 6.968; 95% confidence interval [CI], 3.562-13.631). In the entire cohort, recanalization rates were significantly different between aneurysm volume of <500 and >500 mm3 (7.2% vs. 62.9%, respectively; P < 0.0001; OR, 21.848; 95% CI, 13.944-34.235). In aneurysm volumes of >500 mm3, the location was a significant prognostic factor for long-term stability (posterior circulation vs. anterior circulation; OR, 4.737; 95% CI, 1.275-17.602; P = 0.020). CONCLUSIONS: In our series of cerebral aneurysms treated with coil embolization, 500 mm3 was found to be the critical volume determining stability after coil embolization. Large volume aneurysms in the posterior circulation were especially prone to recanalization after coiling.

De Novo Intracranial Aneurysms Detected on Imaging Follow-Up of Coiled Aneurysms in a Korean Population.

OBJECTIVE: Coiled aneurysms are known to recanalize over time, making follow-up evaluations mandatory. Although de novo intracranial aneurysms (DNIAs) are occasionally detected during routine patient monitoring, such events have not been thoroughly investigated to date. Herein, we generated estimates of DNIA development during long-term observation of coiled cerebral aneurysms, focusing on incidence and the risk factors involved. MATERIALS AND METHODS: In total, 773 patients undergoing coil embolization of intracranial aneurysms between 2008 and 2010 were reviewed retrospectively. Their medical records and radiologic data accrued over the extended period (mean, 52.7 ± 29.7 months) were analyzed. For the detection of DNIA, follow-up magnetic resonance angiography and/or conventional angiography were used. The incidence of DNIAs and related risk factors were analyzed using Cox proportional hazards regression and Kaplan-Meier product-limit estimator. RESULTS: In 19 (2.5%) of the 773 patients with coiled aneurysms, DNIAs (0.56% per patient-year) developed during continued long-term monitoring (3395.3 patient-years). Of these, 9 DNIAs (47.4%) were detected within 60 months, with 10 (52.6%) emerging thereafter. The most common site involved was the posterior communicating artery (n = 6), followed by the middle cerebral artery (n = 5) and the basilar top (n = 4). Multivariate analysis indicated that younger age (< 50 years) (hazard ratio [HR] = 1.045; p = 0.010) and recanalization of coiled aneurysms (HR = 2.560; p = 0.047) were significant factors in DNIA formation, whereas female sex, smoking, and hypertension fell short of statistical significance. Cumulative survival rates without DNIA were significantly higher in older subjects (> 60 years; p < 0.001) and in the absence of post-coiling aneurysm recurrence (p = 0.006). CONCLUSION: In most patients with coiled aneurysms, development of DNIAs during long-term monitoring is rare. However, younger patients (< 50 years) or patients with recurring aneurysms appear to be predisposed to DNIAs.

Newly occurring cranial nerve palsy after endovascular treatment of cavernous sinus dural arteriovenous fistulas.

OBJECTIVE: Cranial nerve palsy (CNP) is rarely reported after endovascular intervention for cavernous sinus dural arteriovenous fistulas (CS DAVFs). Our aim was to evaluate the treatment outcomes of CS DAVFs, and the clinical course and risk factors of newly occurring CNPs, with a review of the literature. METHODS: 121 patients with 134 lesions treated in our institution were selected. They were retrospectively analyzed in terms of baseline characteristics, radiologic results, clinical outcome, and newly occurring CNPs after treatment. Angiographic and clinical follow-up data were available for 104 lesions (77.6%) and 130 lesions (97.0%), respectively. RESULTS: The angiographic results showed partial:complete obliterations in 13:91 (87.5%) at the final follow-up. Clinical outcomes were deteriorated or no change:improved or completely recovered (3:126 (96.9%)) at the final follow-up. New CNPs occurred in 24 patients (19.8%), including the sixth CNP alone or mixed in 23 patients (95.8%). 23 cases were completely recovered or improved (21 and 2 cases, respectively), and 19 (90.4%) of 21 were completely recovered within 6 months after treatment. In the multivariate analysis, pretreatment cranial nerve symptoms (OR=0.33; 95% CI 0.14 to 0.76; P=0.010) and complete obliteration immediately after treatment (OR=0.32; 95% CI 0.12 to 0.85; P=0.021) were significant preventive factors for new CNPs. Embolization in the posterior compartments of the CS (OR=5.15; 95% CI 1.71 to 15.47; P=0.004) was a significant risk factor. CONCLUSIONS: Endovascular intervention was satisfactory in patients with CS DAVFs. The prognosis of newly occurring CNPs was favorable.

Safety and efficacy of anterior communicating artery compromise during endovascular coil embolization of adjoining aneurysms.

OBJECTIVE: In the presence of symmetric A1 flow, the safety and efficacy of compromising the anterior communicating artery (ACoA) during coil embolization of ACoA aneurysms has yet to be evaluated. Herein, the authors describe their experience, focusing on procedural safety. METHODS: Between October 2012 and July 2017, 285 ACoA aneurysms with symmetric A1 flows were treated at the authors' institution by endovascular coil embolization. Clinical and angiographic outcome data were subjected to binary logistic regression analysis. RESULTS: ACoA compromise was chosen in the treatment of 71 aneurysms (24.9%), which were completely (n = 15) or incompletely (n = 56) compromised. In the remaining 214 lesions, the ACoA was preserved. Although 9 patients (3.2%) experienced procedure-related thromboembolisms (compromised, 4; preserved, 5), all but 1 patient (with ACoA compromise) were asymptomatic. In multivariate analysis, subarachnoid hemorrhage at presentation was the sole independent risk factor for thromboembolism (OR 15.98, p < 0.01), with ACoA compromise being statistically unrelated. In 276 aneurysms (96.8%) with follow-up of > 6 months (mean 20.9 ± 13.1 months, range 6-54 months), recanalization was confirmed in 21 (minor, 15; major, 6). A narrow (≤ 4 mm) saccular neck (p < 0.01) and ACoA compromise (p = 0.04) were independently linked to prevention of recanalization. CONCLUSIONS: During coil embolization of ACoA aneurysms, the ACoA may be compromised without serious complications if A1 flows are symmetric. This approach may also confer some long-term protection from recanalization, serving as a valid treatment option for such lesions.

Hemodynamic Differences Between Recurrent and Nonrecurrent Intracranial Aneurysms: Fluid Dynamics Simulations Based on MR Angiography.

BACKGROUND AND PURPOSE: Although the role of wall shear stress (WSS) in the initiation, growth, and rupture of intracranial aneurysms has been well studied, its influence on aneurysm recurrence after endovascular treatment requires further investigation. We aimed to compare WSS at necks of recurrent and nonrecurrent aneurysms. METHODS: Nine recurrent coil-embolized aneurysms were identified and matched with nine nonrecurrent aneurysms. Patient-specific vessel geometries reconstructed from follow-up 3-D time-of-flight magnetic resonance angiography were analyzed using computational fluid dynamics (CFD) simulations. Absolute WSS and the percentage of abnormally low and high WSS at the aneurysm neck compared to the near artery were measured. RESULTS: The median percentage of abnormal WSS at the aneurysm neck was 49.3% for recurrent and 34.7% for nonrecurrent aneurysms (P = .011). The area under the receiver-operating-characteristic curve for distinguishing these aneurysms according to the percentage of abnormal WSS was .86 (95% CI .62 to .98). The optimal cut-off value of 45.1% resulted in a sensitivity and a specificity of 88.89% (95% CI 51.8% to 99.7%). CONCLUSION: Our findings indicate that necks of recurrent aneurysms are exposed to abnormal WSS to a larger extent. Abnormal WSS may serve as a metric to distinguish them from nonrecurrent aneurysms with CFD simulations a priori.

Validation of source detective system of the radionuclides measured in the atmosphere using a field tracer experiment.

A source detective system has been developed to estimate unknown source regions and release rates of radionuclides released into the air from covert nuclear activities and accidents. This system is composed of trajectory, atmospheric dispersion, and source term estimation models. Simulated results were compared with the measurements of a field tracer experiment performed at the Yeonggwang nuclear power plant in Korea in May 1996. Two trajectories among five computed backward trajectories moved toward the original release point, and the comparative results contained some error due to single operation of the backward trajectory model. An atmospheric dispersion model was used to minimize the error of the trajectory model and to improve the accuracy of the source detective system. The results generated by the trajectory and atmospheric dispersion models together agreed better with the measurements than those obtained using the trajectory model alone.

Comparative analysis of coil embolization in posterior and anterior communicating artery aneurysms.

BACKGROUND: Recanalization rates after coil embolization are known to be higher in cerebral aneurysms of the posterior (vs anterior) circulation. Although often grouped with anterior lesions, aneurysms of the posterior communicating artery (PcoA) may nevertheless behave differently. OBJECTIVE: We performed a comparative analysis to explore differences in recanalization rates of PcoA and anterior communicating artery (AcoA) aneurysms, both integral to the circle of Willis. METHODS: Between October 2012 and July 2017, 699 AcoA (n=427) and PcoA (n=272) aneurysms were treated by endovascular coil embolization, monitoring 667 (95.4%) via radiologic imaging for ≥ 6 months. Cumulative recordings of medical and imaging data were retrospectively reviewed, conducting propensity score matching and binary logistic regression analysis. RESULTS: In the 667 aneurysms followed longer term, recanalization occurred in 111 (16.6%; minor 72; major 39) and was significantly more frequent in PcoA (25.5%) than in AcoA (11.0%; P<0.01) aneurysms during similar follow-up periods. After 1:1 propensity score matching, an even greater proclivity for recanalization was evident at PcoA sites (PcoA 23.0%; AcoA 12.2%; P<0.01). Although A1 segment dominance was linked to recanalization in AcoA aneurysms (18.2% vs 7.6%; P=0.01), the PcoA counterpart had no bearing on recanalization (27.7% vs 24.1%; P=0.51). CONCLUSIONS: Despite a clear preponderance of AcoA aneurysms, recanalization of PcoA aneurysms proved significantly greater, attesting to posterior circulation behavior.

Stent-assisted coil embolization of anterior communicating artery aneurysms: safety, effectiveness, and risk factors for procedural complications or recanalization.

INTRODUCTION: Stent-assisted coil (SAC) embolization is an alternative treatment option for anterior communicating artery (AcoA) aneurysms. This study was undertaken to assess the safety and effectiveness of SAC embolization in treating AcoA aneurysms and to determine risk factors for related procedural complications or recanalization. METHODS: Between August 2008 and December 2016, 184 patients with AcoA aneurysms were treated with SAC embolization. Cumulative medical record and radiologic data were analyzed using binary logistic regression to identify factors predisposing to procedural complications or recanalization. RESULTS: Contralateral A1 segment hypoplasia was observed in 59 patients (32.1%). Three types of stents (LVIS, Enterprise, and Neuroform) were variably placed by one of two routes: (1) ipsilateral A1 to ipsilateral A2 (75.5%) or (2) ipsilateral A1 to contralateral A2 (24.5%). Procedural complications occurred in 17 patients (thromboembolism 12; procedural leakage 3; both 2), showing a significant relation to subarachnoid hemorrhage at presentation (OR 57.750; P<0.01). Occlusion was documented immediately after embolization in 130 aneurysms (70.6%) and, in 23 (13.1%) of 175 AcoA aneurysms followed by angiography (median 25.9±18.5 months), recanalization developed (minor, 15; major, 8). Stent configuration (ipsilateral A1 to contralateral A2, P=0.024), maximum aneurysm size (>7 mm, P<0.01), and A1 segment hypoplasia (P=0.039) were identified as risk factors for recanalization. CONCLUSION: SAC embolization is a safe and effective method of treating unruptured AcoA aneurysms, regardless of anatomic or clinical features. However, in the event of rupture, procedural complications are likely. Stent configuration, aneurysm size, and A1 segment hypoplasia were identified as significant risk factors for recanalization.

Growth of Asymptomatic Intracranial Fusiform Aneurysms : Incidence and Risk Factors.

PURPOSE: Growth of intracranial fusiform aneurysms (IFA) may become clinically problematic through a mass effect or rupture. We investigated the growth rate and factors contributing to growth in asymptomatic untreated IFA. METHOD: As a retrospective review, we assessed patients diagnosed with asymptomatic IFA between August 2000 and September 2014, all untreated. No acute or symptomatic dissecting lesions were considered. Clinical and serial angiographic follow-up data were analyzed, defining growth as expansion > 2 mm in one or more dimensions. A binary logistic regression model and Kaplan-Meier method were applied for statistical analysis. RESULTS: The mean follow-up in the 82 eligible patients was 47.7 months (range 12-190 months). Among them, 7 aneurysms (8.5%, 2.1% per aneurysm year) demonstrated growth (in any dimension). In univariate analysis, height and multiplicity of aneurysms emerged as significant factors in terms of growth. Height remained an independent risk factor in the binary logistic regression model, with receiver operating curves indicating a threshold of 6.9 mm initial height in determining IFA growth (area under the curve 0.804). Of the patients six (except one who underwent endovascular treatment) were observed during continued follow-up monitoring. All six lesions were stable in serial imaging tests, without further detectable growth or rupture (mean 33 months). CONCLUSION: Most (91.5%) of the asymptomatic and untreated IFAs studied proved to be stable, with no continued growth; however, because aneurysm height proved to be independently predictive of growth (lesions > 6.9 mm being at risk), periodic imaging is required in those left untreated. Growing but still asymptomatic aneurysms call for the utmost caution and care in decision-making.