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Objective: Image-guided diagnosis and treatment of lung lesions is an active area of research. With the growing number of solutions proposed, there is also a growing need to establish a standard for the evaluation of these solutions. Thus, realistic phantom and preclinical environments must be established. Realistic study environments must include implanted lung nodules that are morphologically similar to real lung lesions under X-ray imaging. Methods: Various materials were injected into a phantom swine lung to evaluate the similarity to real lung lesions in size, location, density, and grayscale intensities in X-ray imaging. A combination of n -butyl cyanoacrylate (n-BCA) and ethiodized oil displayed radiopacity that was most similar to real lung lesions, and various injection techniques were evaluated to ensure easy implantation and to generate features mimicking malignant lesions. Results: The techniques used generated implanted nodules with properties mimicking solid nodules with features including pleural extensions and spiculations, which are typically present in malignant lesions. Using only n-BCA, implanted nodules mimicking ground glass opacity were also generated. These results are condensed into a set of recommendations that prescribe the materials and techniques that should be used to reproduce these nodules. Conclusions: Generated recommendations on the use of n-BCA and ethiodized oil can help establish a standard for the evaluation of new image-guided solutions and refinement of algorithms in phantom and animal studies with realistic nodules. [ABSTRACT FROM AUTHOR]

Background Intrasaccular flow-disrupting devices are a safe and effective treatment strategy for intracranial aneurysms. We utilized high-frequency optical coherence tomography (HF-OCT) and digital subtraction angiography (DSA) to evaluate SEAL Arc, a new intrasaccular device, and compare the findings with the well-established Woven EndoBridge (WEB) device in an animal model of saccular aneurysms. Methods In a rabbit model, elastase-induced aneurysms were treated with SEAL Arc (n=11) devices. HF-OCT and DSA were performed after implant and repeated after 12 weeks. Device protrusion and malapposition were assessed at implant time and scored on a binary system. Aneurysm occlusion was assessed at 12 weeks with the WEB Occlusion Scale and dichotomized to complete (A and B) or incomplete (C and D) occlusion. The percentage of neointimal coverage after 12 weeks was quantified using HF-OCT. We compared these data to previously published historical controls treated with the gold-standard WEB device (n=24) in the same model. Results Aneurysm size and device placement were not significantly different between the two groups. Complete occlusion was demonstrated in 80% of the SEAL Arc devices, which compared favorably to the 21% of the aneurysms treated with WEB devices (P=0.002). Neointimal coverage across SEAL Arc devices was 86±15% compared with 49±27% for WEB (P=0.001). Protruding devices had significantly less neointimal coverage (P<0.001) as did incompletely occluded aneurysms (P<0.001). Histologically, all aneurysms treated with SEAL Arc devices were completely healed. Conclusion Complete early aneurysm occlusion was frequently observed in the SEAL Arc treated aneurysms, with significant neointimal coverage after 12 weeks. [ABSTRACT FROM AUTHOR]

Background Flow diverters carry the risk of thromboembolic complications (TEC). We tested a coating with covalently bound heparin that activates antithrombin to address TEC by locally downregulating the coagulation cascade. We hypothesized that the neuroimaging evidence of TEC would be reduced by the coating. Methods 16 dogs were implanted with overlapping flow diverters in the basilar artery, separated into two groups: heparin-coated (n=9) and uncoated (n=7). Following implantation, high-frequency optical coherence tomography (HF-OCT) was acquired to quantify acute thrombus (AT) formation on the flow diverters. MRI was performed postoperatively and repeated at 1, 2, 3, 4, and 8 weeks, consisting of T1-weighted imaging, time-0f-flight (ToF), diffusion weighted imaging (DWI), susceptibility weighted imaging (SWI), and fluid attenuated inversion recovery (FLAIR) sequences. Neurological examinations were performed throughout the 8-week duration of the study. Results The mean AT volume on coated devices was lower than uncoated (0.014 vs 0.018 mm³); however, this was not significant (P=0.3). The mean number of foci of magnetic susceptibility artifacts (MSAs) on SWI was significantly different between the uncoated and coated groups at the 1-week follow-up (P<0.02), and remained statistically different throughout the duration of the study. The AT volume showed a direct linear correlation with the MSA count and 80% of the variance in the MSA could be explained by the AT volume (P<0.001). Pathological analysis showed evidence of ischemic injury at locations of MSA. Conclusions Heparin-coated flow diverters significantly reduced the number of new MSAs after 1 week follow-up, showing the potential to reduce TEC. [ABSTRACT FROM AUTHOR]

Background Flow diversion has become a standard treatment for cerebral aneurysms. However, major drawbacks include the need for dual antiplatelet therapy after implant and delayed complete occlusion of the aneurysm, which occurs when new tissue growth excludes the aneurysm from the parent artery. Biomimetic surface modifications such as the phosphorylcholine polymer (Shield surface modification) represent major advances in reducing thrombogenicity of these devices. However, in vitro studies have raised concerns that this modification may also delay endothelialization of flow diverters. Methods Bare metal Pipeline, Pipeline Shield, and Vantage with Shield devices were implanted in the common carotid arteries (CCAs) of 10 rabbits (two in the left CCA, one in the right CCA). Following implant and at 5, 10, 15, and 30 days, the devices were imaged with high-frequency optical coherence tomography and conventional angiography to evaluate tissue growth. At 30 days the devices were explanted and their endothelial growth was assessed with scanning electron microscopy (SEM) at five locations along their length using a semiquantitative score. Results The average tissue growth thickness (ATGT) was not different between the three devices. Neointima was apparent at 5 days and all devices demonstrated similar ATGT at each time point. On SEM, no difference was found in the endothelium scores between the device types. Conclusion In vivo, neither the Shield surface modification nor the device design (Vantage) altered the longitudinal healing of the flow diverter. [ABSTRACT FROM AUTHOR]

Background Preclinical testing of intracranial stents is currently performed in the peripheral circulation, and rarely in the basilar artery of the dog. Objective To test the feasibility of intracranial stenting in the middle cerebral artery (MCA) of the dog and explore the use of MRI to detect thromboembolic complications. Methods Six purpose-bred cross-hound dogs were used for proof-of-concept stenting of both MCAs in each animal. Immediately following the procedure, the animals were imaged with MRI. MRI was repeated weekly for 1 month. After the final angiography at 30 days, the animals were euthanized for pathological assessment of the stents and the brain. Results We successfully deployed 12 stents in the MCAs of all animals. We deployed three techniques for microcatheterization of the MCA--namely, directly through the internal carotid artery (ICA), using anastomotic arteries from the external carotid artery, or via the contralateral ICA through the anterior communicating artery. Two iatrogenic perforations of the ICA with formation of an arteriovenous fistula occurred, without clinical sequelae, which spontaneously resolved on follow-up. All animals tolerated the procedure and completed the follow-up surveillance. MRI revealed procedural thromboembolic induced areas of restricted diffusion, and only one instance of a delayed thromboembolic lesion during surveillance. At follow-up angiography, the devices were all patent. Conclusion We describe a new preclinical model of intracranial stenting in the MCA. Such a model may prove useful for evaluating new surface modifications. [ABSTRACT FROM AUTHOR]

Background High-frequency optical coherence tomography (HF-OCT) is an intravascular imaging method that allows for volumetric imaging of flow diverters in vivo. Objective To examine the hypothesis that a threshold for both volume and area of communicating malapposition can be predictive of early aneurysm occlusion. Methods Fifty-two rabbits underwent elastase aneurysm formation, followed by treatment with a flow diverter. At the time of implant, HF-OCT was acquired to study the rate and degree of communicating malapposition. Treated aneurysms were allowed to heal for either 90 or 180 days and euthanized following catheter angiography. Healing was dichotomized into aneurysm remnant or neck remnant/complete occlusion. Communicating malapposition was measured by HF-OCT using a semi-automatic algorithm able to detect any points where the flow diverter was more than 50 µm from the vessel wall. This was then summed across image slices to either a volume or area. Finally, a subsampled population was used to train a statistical classifier for the larger dataset. Results No difference in occlusion rate was found between device type or follow-up time (p=0.28 and p=0.67, respectively). Both volume and area of malapposition were significantly lower in aneurysms with a good outcome (p<0.001, both). From the statistical model, a volume of less than 0.56 mm3 or a normalized area less than 0.69 as quantified by HF-OCT was predictive of occlusion (p<0.001, each). Conclusions HF-OCT allows for measurements of both volume and area of malapposition and, from these measurements, an accurate prediction for early aneurysm occlusion can be made. [ABSTRACT FROM AUTHOR]