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Objective: To illustrate the added value of flat-detector computed tomography angiography with intravenous contrast media injection (intravenous FDCTA) in the evaluation of complex A1/A2/AcomA aneurysms., Patients and Methods: We retrospectively reviewed 15 patients with ruptured aneurysms. In each patient, an intravenous FDCTA was performed and its diagnostic value investigated., Results: In all patients, FDCTA contributed relevant additional information concerning the anatomy of the A1/A2/AcomA complex and the relationship of the aneurysm neck to these vascular structures, which could not be gained by 2D- and 3D-DSA, and changed the management in 33% of the patients (5 out of 15). In an additional 5 cases, knowledge of the detailed anatomy was helpful to plan the exact stent position., Conclusion: In case of complex A1/A2/AcomA aneurysms, intravenous FDCTA is an effective option to visualize the exact location of the aneurysm neck and the relationship between the aneurysm and the adjacent vessels. Thus, it is of significant added value in the precise planning of a therapeutic strategy.

We compared flat-detector computed tomography angiography (FD-CTA) to multislice computed tomography (MS-CTA) and digital subtracted angiography (DSA) for the visualization of experimental aneurysms treated with stents, coils or a combination of both.In 20 rabbits, aneurysms were created using the rabbit elastase aneurysm model. Seven aneurysms were treated with coils, seven with coils and stents, and six with self-expandable stents alone. Imaging was performed by DSA, MS-CTA and FD-CTA immediately after treatment. Multiplanar reconstruction (MPR) was performed and two experienced reviewers compared aneurysm/coil package size, aneurysm occlusion, stent diameters and artifacts for each modality.In aneurysms treated with stents alone, the visualization of the aneurysms was identical in all three imaging modalities. Residual aneurysm perfusion was present in two cases and visible in DSA and FD-CTA but not in MS-CTA. The diameter of coil-packages was overestimated in MS-CT by 56% and only by 16% in FD-CTA compared to DSA (p < 0.05). The diameter of stents was identical for DSA and FD-CTA and was significantly overestimated in MS-CTA (p < 0.05). Beam/metal hardening artifacts impaired image quality more severely in MS-CTA compared to FD-CTA.MS-CTA is impaired by blooming and beam/metal hardening artifacts in the visualization of implanted devices. There was no significant difference between measurements made with noninvasive FD-CTA compared to gold standard of DSA after stenting and after coiling/stent-assisted coiling of aneurysms. FD-CTA may be considered as a non-invasive alternative to the gold standard 2D DSA in selected patients that require follow up imaging after stenting., (© The Author(s) 2015.)

Objectives: After deployment of flow-diverting stents (FDS), complete aneurysm occlusion is not predictable. This study investigated whether parametric colour coding (PCC) could allow in vivo visualization of flow alterations induced by FDS and identify favourable or adverse flow modulations., Methods: Thirty-six patients treated by FDS were analyzed. Preinterventional and postinterventional DSA-series were postprocessed by PCC and time-density curves (TDCs) were calculated. The parameters aneurysmal inflow, outflow, and relative time-to-peak (rTTP) were calculated. Preinterventional and postinterventional values were compared and related to occlusion rate., Results: Postinterventional inflow showed a mean reduction of 37%, outflow of 51%, and rTTP a prolongation of 82%. Saccular aneurysm occlusion occurred if a reduction of at least 15% was achieved for inflow and 35% for outflow (sensitivity: 89%, specificity: 82%). Unchanged outflow and a slightly prolonged rTTP were associated with growth in one fusiform aneurysm., Conclusions: PCC allows visualization of flow alterations after FDS treatment, illustrating "flow diverting effects" by the TDC shape and indicating mainly aneurysmal outflow and lesser inflow changes. Quantifiable parameters (inflow, outflow, rTTP) can be obtained, thresholds for predicting aneurysm occlusion determined, and adverse flow modulations assumed. As a rapid intraprocedural tool, PCC might support the decision to implant more than one FDS., Key Points: • After deployment of a flow-diverting stent, complete aneurysm occlusion is unpredictable. • Parametric colour coding offers new options for visualizing in vivo flow alterations non-invasively. • Quantifiable parameters, i.e., aneurysmal inflow/outflow can be obtained allowing prognostic stratification. • Rapid, intraprocedural application allows treatment monitoring, potentially contributing to patient safety.

Background: For preclusion of remnants after aneurysm clipping, a reliable, noninvasive imaging technique is desirable., Objective: To evaluate the reliability of optimized angiographic computed tomography with intravenous contrast agent injection (ivACT) in detecting remnants after aneurysmal clipping compared with digital subtraction angiography (DSA), the gold standard., Methods: We included 84 patients with 112 clipped cerebral aneurysms of the anterior circulation. For treatment, 116 clips of cobalt and 57 clips of titanium alloy were used. In each patient, we performed an ivACT with dual rotational acquisition and a DSA. Data from ivACT were postprocessed with a dual-volume technique with newly implemented reconstructions modes. Aneurysm remnants were measured, classified, and correlated with DSA by 2 raters., Results: In total, 12 remnants were revealed by DSA, meaning a prevalence of 11%. IvACT demonstrated a sensitivity of 75% to 92% and a specificity of 99% in detecting remnants up to a minimal size of 0.7 × 0.3 mm. Classification of remnants by ivACT was identical to that by DSA, and assessment of size showed a significant correlation with DSA (P < .001). No significant differences between cobalt and titanium alloy were revealed concerning artifacts., Conclusion: Optimized ivACT with enhanced postprocessing demonstrated high sensitivity and specificity in detecting remnants after aneurysm clipping in the anterior circulation. Classification and assessment of remnant size and detection of relevant parent artery stenosis showed high accuracy of ivACT compared with DSA. Our results indicate that ivACT might become a noninvasive alternative to DSA for postsurgical control.

Background: Quantifiable parameters to evaluate the effectiveness of flow diverters (FDs) are desirable. We measured time-density curves (TDCs) and calculated quantifiable parameters in the rabbit elastase-induced aneurysm model after stent (Neuroform [NF]) and FD (Pipeline embolisation device [PED]) treatment., Methods: Sixteen rabbit elastase-induced aneurysms were treated with FD (n = 9) or NF (n = 5). Angiography was performed before and after treatment and TDCs were created. The time to peak (TTP), the full width at half maximum (FWHM) and the average slope of the curve which represent the inflow (IF) and outflow (OF) were calculated., Results: Mean values before treatment were TTP = 0.8 s, FWHM = 1.2 s, IF = 153.5 and OF = -54.9. After PED treatment, the TTP of 1.8 s and FWHM of 47.8 s were extended. The IF was 31.2 and the OF was -11.5 and therefore delayed. The values after NF treatment (TTP = 1.1 s, FWHM = 1.8 s, IF = 152.9, OF = -33.2) changed only slightly., Conclusion: It was feasible to create TDCs in the rabbit aneurysm model. Parameters describing the haemodynamic effect of PED and NF were calculated and were different according to the type of device used. These parameters could possibly serve as predictive markers for aneurysm occlusion.

Object: The purpose of this study was to evaluate the diagnostic accuracy of an optimized angiographic CT (ACT) program with intravenous contrast agent injection (ivACT) in the assessment of potential aneurysm remnants after neurosurgical clipping compared with conventional digital subtraction angiography (DSA)., Methods: The authors report on 14 patients with 19 surgically clipped cerebral aneurysms who were scheduled to undergo angiographic follow-up. For each patient, the authors performed ivACT with dual rotational acquisition and conventional angiography including a 3D rotational run. The ivACT and 3D DSA data were reconstructed with different imaging modes, including a newly implemented subtraction mode with motion correction. Thereafter, the data sets were merged by the dual-volume technique, and freely rotatable 3D images were obtained for further analysis. Observed aneurysm remnants were electronically measured and classified for each modality by 2 experienced neuroradiologists., Results: Digital subtraction angiography and ivACT both provided high-quality images without motion artifacts. Artifact disturbances from the aneurysm clips led to a compromised, but still sufficient, image quality in 1 case. The ivACT assessed all aneurysm remnants as true-positive up to a minimal size of 2.6×2.4 mm in accordance with the DSA findings. There was a tendency for ivACT to overestimate the size of the aneurysm remnants. All cases without aneurysm remnants on DSA were scored correctly as true-negative by ivACT., Conclusions: By using an optimized image acquisition protocol as well as enhanced postprocessing algorithms, the noninvasive ivACT seems to achieve results comparable to those of conventional angiography in the follow-up of clipped cerebral aneurysms. The authors have shown that ivACT can provide reliable diagnostic information about potential aneurysm remnants after neurosurgical clipping with high sensitivity and specificity, sufficient for clinical decision making, at least for aneurysms in the anterior circulation located distal to the internal carotid artery. These preliminary results may be a promising step to replace conventional angiography by a noninvasive imaging technique in selected cases after aneurysm clipping.

Introduction: Intracranial flow diverting devices are increasingly used to treat cerebral aneurysms. A reliable, non-invasive follow-up modality would be desirable. Our aim was to compare intra-arterial digital subtraction angiography (ia DSA) to angiographic computed tomography with intravenous contrast agent application (iv ACT) in the visualisation of flow diverting devices and aneurysm lumina., Methods: Follow-up monitoring by iv ACT (n = 36) and ia DSA (n = 25) in 14 patients treated with flow diverting devices for intracranial aneurysms was evaluated retrospectively. Images were evaluated by two neuroradiologists in anonymous consensus reading regarding the device deployment, wall apposition, neck coverage of the aneurysm, opacification of the vessel and device lumen, as well as the degree of aneurysm occlusion., Results: Corresponding ia DSA and iv ACT images were scored identically in all patients regarding the stent deployment, wall apposition and neck coverage, as well as the degree of aneurysm occlusion and patency status of the device and parent artery. Opacification of the parent vessel lumen and perfused parts of the aneurysm was considered slightly inferior for iv ACT in comparison with ia DSA (seven of 36 cases), without impact on diagnosis., Conclusions: We demonstrated the feasibility and diagnostic value of iv ACT in follow-up imaging of intracranial flow diverting devices. Due to its high spatial resolution and non-invasive character, this novel technique might become a valuable imaging modality in these patients.

Objective: To demonstrate the feasibility of intravenous Flat Detector CT Angiography (FD-CTA) for visualisation of intracranial Flow Diverting Devices. Flow Diverting Devices are used increasingly for treatment of intracranial aneurysms. A close follow up is necessary because it becomes obvious that a significant proportion of aneurysms treated with these devices remain patent. A minimally invasive method is highly desirable., Methods: In two patients treated with flow diverters a Flat Detector CT (FD-CT) with intravenous contrast medium application was performed. Post-processing was performed using commercially available software., Results: In both patients the lumen of the device and the lumen of the aneurysm could be clearly evaluated. Some beam hardening artefacts due to the marker wires of the device were obvious., Conclusion: Flat Detector CT with intravenous contrast material application to evaluate flow-diverting devices seems to be feasible. Further studies are necessary to perform comparative evaluation of FD-CTA with angiography and other techniques like MRA or conventional CT angiography.

Background: Despite limited soft tissue resolution flat-detector computed tomography (FD-CT) provides substantial superior spatial resolution in comparison with multislice computed tomography (MS-CT). This may add value in the visualization of small vascular structures if intravenous contrast application leads to substantial opacification and visibility of intracranial vessels or aneurysms., Purpose: To evaluate the feasibility of visualization of vascular structures by FD-CT angiography (FD-CTA) after intravenous contrast injection compared with MS-CTA and intra-arterial digital subtracted angiography (IADSA) in an animal model., Material and Methods: Aneurysms were created in the right common carotid artery in six New Zealand White Rabbits using the elastase technique. Imaging was performed using FD-CTA, MS-CTA (injection of 1 ml/kg body weight) and IADSA. Anonymized volume rendering reconstruction (VRT), maximum intensity projection (MIP), and multiplanar reconstruction (MPR) images were reconstructed and evaluated by two experienced reviewers for aneurysm geometry and vascular structure anatomy using standard tools of a dedicated workstation., Results: Aneurysms could be successfully created in all animals. Measurements of aneurysm geometry (aneurysm height, width, neck width) and vascular structures (brachiocephalic trunk, carotid artery diameter and plane) were nearly identical in all three modalities. Intra- and inter-observer correlations of the different parameters showed high r values between 0.83 and 0.99., Conclusion: Our results show the feasibility of FD-CTA in comparison with MS-CTA and IADSA in an animal model. Despite limited soft tissue resolution, opacification of vascular structures with sufficient contrast to the surrounding structures was possible in all animals. Vascular structures appeared better delineated in FD-CTA than in MS-CTA, probably due to the superior spatial resolution.

Object: The use of liquid embolic agents for endovascular treatment of cerebral aneurysms is evolving. The authors' aim was to evaluate the use of Onyx HD-500 in an experimental aneurysm model and to obtain histological and angiographic long-term results., Methods: Ten aneurysms were created using an elastase model in rabbits. The aneurysms were embolized using Onyx in combination with an inflated balloon. One animal died 1 day after embolization. The animals were divided into 2 different groups. The animals in the first group (4 rabbits) were killed at 3 months and those in the second group (5 rabbits) were killed at 6 months after embolization. A venous control angiogram was obtained, and the aneurysms were examined histologically., Results: In both groups control angiograms demonstrated that all aneurysms were completely occluded. There were no signs of recanalization. Migration of Onyx was seen in 4 animals, leading to the death of 1. Histological examination not only proved the aneurysms to be occluded but also demonstrated a thin layer of endothelium at the neck of the aneurysm. The histological result was identical in both groups., Conclusions: This is the first study reporting the formation of a neointima over the neck of aneurysms embolized with Onyx in a rabbit model. Although the technique is challenging and migration of the liquid embolic agent cannot always be prevented, Onyx has a great potential to achieve a durable occlusion of aneurysms.

Introduction: The aim of this study was to evaluate the risks of endovascular therapy, aneurysm regrowth, recanalization and the need for reembolization., Method: A prospective analysis was performed on 211 aneurysms treated endovascularly from February 2000 to December 2003. Of these 211 aneurysms, 81 were asymptomatic and 130 were ruptured. The risks of endovascular therapy, aneurysm regrowth, recanalization and the need for reembolization were evaluated., Results: The mean observation time was 10 months (ranging from 178 to 830 days). Complete occlusion (100%) in the initial intervention was achieved in 171 of 201 aneurysms (85%), 80-95% occlusion in 24 aneurysms (12%), and <80% occlusion in 6 aneurysms (3%). Recanalization had occurred at the first follow-up in 34 of all 153 aneurysms reassessed (22.2%). Of 133 aneurysms with initial 100% occlusion, 107 (80.4%) remained completely occluded, 17 (12.7%) showed recanalization, and 9 (6.7%) showed neck regrowth. Among those with 80-95% occlusion, 20 were reassessed, and of these 2 showed spontaneous occlusion, 10 (50%) still showed the initial neck, and 8 (40%) showed increased recanalization. One aneurysm which initially showed <80% occlusion remained unchanged, and another showed showed recanalization. Of the 153 aneurysms, 12 (7.8%) were recoiled, 2 initially <80% occluded, 7 initially 80-95% occluded and 3 initially totally occluded., Conclusion: In spite of low morbidity and mortality, one in four aneurysms will show recurrence. The initial degree of occlusion seems to have an influence on the likelihood of recanalization.

Objective: The purpose of this study was to evaluate the frequency and causes of thromboembolic events associated with endovascular embolization of asymptomatic aneurysms. Correlations between radiological findings (aneurysm size, localization, embolization time, number of coils used, as well as patient age) were evaluated with the occurrence of thromboembolic events and clinical findings., Methods: Sixty-eight patients treated for unruptured intracranial aneurysms (mean age, 49 yr) were evaluated. Hyperintense lesions on diffusion weighted imaging were analyzed in 50 patients. Aneurysm size was 3 to 15 mm., Results: Complete occlusion of the aneurysms was achieved in 55 of 68 (82%). One patient had a transient paresis. There was one infarction and one aneurysm rupture during the procedure with no consecutive neurological symptoms. We found new hyperintense lesions in 21 of 50 (42%) diffusion weighted imaging studies. In 43% of these, there was only one lesion smaller than 2 mm. In 33%, there was more than one lesion less than 2 mm; in 19%, we found a lesion of 2 to 10 mm in size. In one case, a lesion greater than 10 mm occurred. There was no correlation between aneurysm location and the occurrence of lesions or among the number of coils used, the size of the aneurysm, patient age, or embolization time. Mortality rate was 0%, morbidity 4.0%. If the 18 aneurysms where no diffusion weighted imaging was obtained are included, morbidity is 2.9%., Conclusion: The high rate of thromboembolic events suggests that heparin is not sufficient to prevent ischemic lesions. An antiplatelet therapy, started before or during intervention, might diminish thrombus formation.

Objective: Our purpose was to determine whether anticoagulation has an influence on the occlusion rate and thromboembolic occurrence in saccular aneurysms treated with Guglielmi detachable coils., Methods: Aneurysms in the right CCA were created in rabbits. Group 1 served as a control group (n = 6) without embolization or anticoagulation. In Groups 2 to 5, aneurysms were embolized. In Group 2, no anticoagulation was given (n = 5). Group 3 received heparin before the placement of the first coil, then low molecular weight heparin (LMWH) for the next 2 days (n = 7). In Group 4, additional aspirin was administered after 2 days until sacrifice (n = 10). Group 5 received heparin before the placement of the first coil, then a LMHW was administered daily until sacrifice (n = 5). Angiography was performed 3 months after coiling, followed by a histological examination., Results: Histopathological evaluation showed thrombus formation with neovascularization, regardless of the anticoagulation regime used. Only in the group with LMWH over 3 months was the thrombus not focally, properly organized, especially in the dome. The coils in the neck showed, however, the same fibrous scar tissue as in the other groups., Conclusion: Anticoagulation with heparin during the first days, followed by aspirin, appears unlikely to affect the occlusion rate in aneurysms. LMWH over a long period, however, could impair thrombus organization. Therefore, in regard to thrombus organization, an anticoagulation regime with aspirin seems to be superior to LMWH. This could play an important role in the prevention of thromboembolic events in humans treated with Guglielmi detachable coils.