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1. Optimizing Radial Force Of Braided Thrombectomy-assist Devices Compared To Laser-cut Stent Retrievers In The MCA.

   Katz, Jeffrey M; Chebl, Alex A; Janardhan, Vikram; Janardhan, Vallabh. (November 2018, Society of Vascular & Interventional Neurology (SVIN))

   Introduction: Recent reports have raised concern about the risk of vessel wall injury (VWI) when pulling out current laser-cut stent retrievers during active strut apposition to the vessel walls.1-4 Development of braided thrombectomy-assist devices for use in conjunction with aspiration systems may be gentler (lower radial force) and more optimized for vessel diameters seen in proximal LVOs and distal LVOs. Methods: Bench testing of radial force (RF) was performed using a radial compression station. The total radial force (RF) in Newtons (N) generated in vessel diameters (d) (Range 2.25 to 3mm) seen in proximal LVOs (~M1), and vessel diameters (d) (Range 1.5 to 2.24mm) seen in distal LVOs (~M2) was measured. Radial Force of less than or equal to 1N was grouped as “low” and radial force greater than 1N was grouped as “high” for this analysis. Results: The total radial force (RF) of all laser-cut stent retrievers (with distal outer diameter OD in mm) studied namely Solitaire Platinum (6.0), Solitaire 2 (4.0), Trevo ProVue (4.0), Baby Trevo (3.0), Capture L (3.0) were all higher in the M2 vessels (>1N) compared to M1 vessels (<1N), whereas the total radial force (RF) of the braided thrombectomy-assist devices namely SHELTER® Retriever (6.0) were uniformly low in both the M1 (<1N) and M2 (<1N) vessels. Conclusion: Choosing a stent retriever with lower OD does not translate to lower radial force. As a result, sizing of stent retrievers and thrombectomy-assist devices to target vessels should not only factor the OD of the devices but also the total radial force in the target vessel diameter. Novel braided thrombectomy-assist devices for use in conjunction with aspiration systems have lower radial force compared to existing laser-cut stent retrievers in the M1 and M2 vessel diameters. Further studies in-vivo need to assess the impact of lower radial force on minimizing VWI. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 2018 Annual Meeting of the Society of Vascular & Interventional Neurology (SVIN), November 14-17, 2018 in San Diego, CA 

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2. Radial Force of Braided Thrombectomy-Assist Devices Vis-à-Vis Laser-cut Stent Retrievers in the ICA and Basilar.

   Chebl, Alex A; Katz, Jeffrey M; Janardhan, Vikram; Janardhan, Vallabh. (November 2018, Society of Vascular & Interventional Neurology (SVIN))

   Background: Recent reports have raised concern about the risk of vessel wall injury (VWI) when pulling out current laser-cut stent retrievers with active strut apposition to the vessel walls. Development of braided stroke thrombectomy-assist devices for use in conjunction with aspiration systems may be gentler in the internal carotid (ICA) and basilar vessels (with regards to radial force) compared to existing laser-cut stent retrievers. Methods: Radial force (RF) bench testing was performed using a radial compression station (Blockwise Engineering, Phoenix, AZ). The average total radial force (RF) in Newtons (N) generated (average of 3 readings) in vessel diameters (d) (Range 3.25 to 4.00mm) seen in proximal LVOs of the anterior circulation (such as in the internal carotid artery - ICA), and vessel diameters (d) (Range 2.50 to 3.25mm) seen in the posterior circulation (such as in the basilar artery - BA) was measured. The Solitaire Platinum Revascularization Device (Medtronic, Irvine, CA) was used as the predicate device. All thrombectomy and thrombectomy-assist devices were compared in terms of the RF being higher or lower (%) to the predicate device. Results: The results of the radial force testing are shown in the table below. The total radial force (RF) of the SHELTER® Retriever (part of Insera System, Insera Therapeutics, Inc., Dallas, TX), a braided thrombectomy-assist device is significantly lower (@ d=2.5mm: 58%) than the predicate device (@ d=2.5mm: 100%) and other laser-cut stent retrievers (@ d=2.5mm: 103% to 152%). Thrombectomy devices with lower OD had higher radial forces than larger devices. Conclusion: Novel braided stroke thrombectomy-assist devices for use in conjunction with aspiration systems have lower radial force compared to existing laser-cut stent retrievers in the ICA and BA vessel diameters. Further studies in-vivo need to assess the impact of lower radial force on minimizing VWI. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 2018 Annual Meeting of the Society of Vascular & Interventional Neurology (SVIN), November 14-17, 2018 in San Diego, CA 

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3. P-023 Optimizing radial force of stent retrievers to minimize vessel wall injury: mechanical bench testing of radial force generated by a novel braided stent retriever compared to laser-cut stent retrievers in the M1 and m2 vessels

   Katz, Jeffrey M; Chebl, Alex A; Janardhan, Vikram; Janardhan, Vallabh (July 2018, Journal of neurointerventional surgery)

   Purpose: Recent reports have raised various concerns about the risk of vessel wall injury while withdrawing current laser-cut stent retrievers during active strut apposition to the vessel walls. The development of braided thrombectomy assist devices in conjunction with aspiration systems may be gentler on the fragile brain vessels and more optimized with regard to the radial force (RF) for vessel diameters of proximal (M1) and distal (M2) large vessel occlusions (LVOs). Methods: Mechanical bench testing of the RF was performed using a radial compression station mounted on a tensile testing machine. The total RF in newtons (N) generated in vessels with diameters ranging from 2.25 to 3 mm as seen in proximal LVOs (∼M1), and in vessel diameters ranging from 1.5 to 2.24 mm as seen in distal LVOs (∼M2), was measured. The outer diameter of each stent was recorded, and an RF ≤1 N was grouped as “low,” while an RF > 1 N was grouped as “high” for this analysis. Results: The total RFs of all laser-cut stent retrievers were all higher in the simulated M2 vessels (> 1 N) than in the M1 vessels (< 1 N), whereas the total RFs of the braided thrombectomy assist devices were uniformly low in both the simulated M1 and the simulated M2 vessels. Conclusions: Novel braided thrombectomy assist devices in conjunction with aspiration systems have lower RFs than existing laser-cut stent retrievers in M1 and M2 vessel diameters. Further in vivo studies are needed to delineate the impact of lowering the RF on vessel wall integrity. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 15th Annual Meeting of the Society of Neuro-Interventional Surgery (SNIS), July 23-26, 2018 in San Francisco, CA. 

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4. High Spatiotemporal Resolution Radial Encoding Single‐Vessel fMRI

   https://doi.org/10.1002/advs.202309218  

   Jiang, Yuanyuan; Pais‐Roldán, Patricia; Pohmann, Rolf; Yu, Xin (April 2024, Advanced Science)

   Abstract High‐field preclinical functional MRI (fMRI) is enabled the high spatial resolution mapping of vessel‐specific hemodynamic responses, that is single‐vessel fMRI. In contrast to investigating the neuronal sources of the fMRI signal, single‐vessel fMRI focuses on elucidating its vascular origin, which can be readily implemented to identify vascular changes relevant to vascular dementia or cognitive impairment. However, the limited spatial and temporal resolution of fMRI is hindered hemodynamic mapping of intracortical microvessels. Here, the radial encoding MRI scheme is implemented to measure BOLD signals of individual vessels penetrating the rat somatosensory cortex. Radial encoding MRI is employed to map cortical activation with a focal field of view (FOV), allowing vessel‐specific functional mapping with 50 × 50 µm²in‐plane resolution at a 1 to 2 Hz sampling rate. Besides detecting refined hemodynamic responses of intracortical micro‐venules, the radial encoding‐based single‐vessel fMRI enables the distinction of fMRI signals from vessel and peri‐vessel voxels due to the different contribution of intravascular and extravascular effects. 

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5. Radial symmetry of minimizers to the weighted Dirichlet energy

   https://doi.org/10.1017/prm.2020.8  

   Koski, Aleksis; Onninen, Jani (February 2020, Proceedings of the Royal Society of Edinburgh: Section A Mathematics)

   null (Ed.)

   Abstract We consider the problem of minimizing the weighted Dirichlet energy between homeomorphisms of planar annuli. A known challenge lies in the case when the weight λ depends on the independent variable z . We prove that for an increasing radial weight λ ( z ) the infimal energy within the class of all Sobolev homeomorphisms is the same as in the class of radially symmetric maps. For a general radial weight λ ( z ) we establish the same result in the case when the target is conformally thin compared to the domain. Fixing the admissible homeomorphisms on the outer boundary we establish the radial symmetry for every such weight. 

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