Publications by authors named "Stephen R Chen"

30 Publications

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Correction to: ISSLS prize in basic science 2021: a novel inducible system to regulate transgene expression of TIMP1.

Eur Spine J 2021 Mar 7. Epub 2021 Mar 7.

Ferguson Laboratory for Orthopaedic and Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.

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http://dx.doi.org/10.1007/s00586-021-06783-7DOI Listing
March 2021

ISSLS prize in basic science 2021: a novel inducible system to regulate transgene expression of TIMP1.

Eur Spine J 2021 Feb 1. Epub 2021 Feb 1.

Ferguson Laboratory for Orthopaedic and Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.

Purpose: Inflammatory and oxidative stress upregulates matrix metalloproteinase (MMP) activity, leading to intervertebral disc degeneration (IDD). Gene therapy using human tissue inhibitor of metalloproteinase 1 (hTIMP1) has effectively treated IDD in animal models. However, persistent unregulated transgene expression may have negative side effects. We developed a recombinant adeno-associated viral (AAV) gene vector, AAV-NFκB-hTIMP1, that only expresses the hTIMP1 transgene under conditions of stress.

Methods: Rabbit disc cells were transfected or transduced with AAV-CMV-hTIMP1, which constitutively expresses hTIMP1, or AAV-NFκB-hTIMP1. Disc cells were selectively treated with IL-1β. NFκB activation was verified by nuclear translocation. hTIMP1 mRNA and protein expression were measured by RT-PCR and ELISA, respectively. MMP activity was measured by following cleavage of a fluorogenic substrate.

Results: IL-1β stimulation activated NFκB demonstrating that IL-1β was a surrogate for inflammatory stress. Stimulating AAV-NFκB-hTIMP1 cells with IL-1β increased hTIMP1 expression compared to unstimulated cells. AAV-CMV-hTIMP1 cells demonstrated high levels of hTIMP1 expression regardless of IL-1β stimulation. hTIMP1 expression was comparable between IL-1β stimulated AAV-NFκB-hTIMP1 cells and AAV-CMV-hTIMP1 cells. MMP activity was decreased in AAV-NFκB-hTIMP1 cells compared to baseline levels or cells exposed to IL-1β.

Conclusion: AAV-NFκB-hTIMP1 is a novel inducible transgene delivery system. NFκB regulatory elements ensure that hTIMP1 expression occurs only with inflammation, which is central to IDD development. Unlike previous inducible systems, the AAV-NFκB-hTIMP1 construct is dependent on endogenous factors, which minimizes potential side effects caused by constitutive transgene overexpression. It also prevents the unnecessary production of transgene products in cells that do not require therapy.
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http://dx.doi.org/10.1007/s00586-021-06728-0DOI Listing
February 2021

Endovascular Selective Intra-Arterial Infusion of Mesenchymal Stem Cells Loaded With Delta-24 in a Canine Model.

Neurosurgery 2020 12;88(1):E102-E113

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas.

Background: Delta-24-RGD, an oncolytic adenovirus, shows promise against glioblastoma. To enhance virus delivery, we recently demonstrated that human bone marrow-derived mesenchymal stem cells loaded with Delta-24-RGD (hMSC-D24) can eradicate glioblastomas in mouse models. There are no studies examining the safety of endovascular selective intra-arterial (ESIA) infusions of MSC-D24 in large animals simulating human clinical situations.

Objective: To perform canine preclinical studies testing the feasibility and safety of delivering increasing doses of hMSCs-D24 via ESIA infusions.

Methods: ESIA infusions of hMSC-D24 were performed in the cerebral circulation of 10 normal canines in the target vessels (internal carotid artery [ICA]/P1) via transfemoral approach using commercially available microcatheters. Increasing concentrations of hMSC-D24 or particles (as a positive control) were injected into 1 hemisphere; saline (negative control) was infused contralaterally. Toxicity (particularly embolic stroke) was assessed on postinfusion angiography, diffusion-weighted magnetic resonance imaging, clinical exam, and necropsy.

Results: ESIA injections were performed in the ICA (n = 7) or P1 (n = 3). In 2 animals injected with particles (positive control), strokes were detected by all assays. Of 6 canines injected with hMSC-D24 through the anterior circulation, escalating dose from 2 × 106 cells/20 mL to 1 × 108 cells/10 mL resulted in no strokes. Two animals had ischemic and hemorrhagic strokes after posterior cerebral artery catheterization. A survival experiment of 2 subjects resulted in no complications detected for 24-h before euthanization.

Conclusion: This novel study simulating ESIA infusion demonstrates that MSCs-D24 can be infused safely at least up to doses of 1 × 108 cells/10 mL (107 cells/ml) in the canine anterior circulation using commercially available microcatheters. These findings support a clinical trial of ESIA infusion of hMSCs-D24.
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http://dx.doi.org/10.1093/neuros/nyaa470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7735865PMC
December 2020

Cognitive outcomes after unruptured intracranial aneurysm treatment with endovascular coiling.

J Neurointerv Surg 2020 Jul 22. Epub 2020 Jul 22.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA

Background: We aimed to determine the effects of endovascular coiling of unruptured intracranial aneurysms (UIAs) on cognition to inform treatment decisions. We present the first study using the Montreal Cognitive Assessment (MoCA) to determine neurocognitive changes after endovascular coiling.

Methods: We prospectively collected data on all patients with UIAs undergoing endovascular coiling, primary or assisted. Patients completed the MoCA prior to intervention and 1 month and 6 months' post-procedure. A repeated measures linear mixed effects model was used to compare pre-procedure and post-procedure cognition.

Results: Thirty-three patients with 33 aneurysms who underwent coiling from April 2017 to May 2020 were included (mean age 55.5, 81.8% female). All procedures used general anesthesia. There was no difference between baseline and post-procedure MoCA scores at any time interval (P>0.05). Mean MoCA scores at baseline, 1 month post-procedure, and 6 months' post-procedure were 25.4, 26.8, and 26.3 respectively. There was also no difference between pre- and post-procedure scores on any individual MoCA domain (visuospatial, naming, memory, attention, language, abstraction, delayed recall, and orientation) at any time interval (P>0.05). Seventeen patients had follow-up MRI or CT imaging, of which 11.8% showed radiographic changes or ischemia. 77.8% of patients with 6-month angiographic follow-up achieved class I, and 22.2% achieved class II Raymond-Roy Occlusion. Thirty-two out of 33 patients had follow-up mRS ≤2.

Conclusion: Our study suggests that endovascular coiling does not diminish neurocognitive function. Patients with UIAs in our cohort also had baseline MoCA scores below the cut-off for mild cognitive impairment despite pre-procedure mRS and NIHSS of 0.
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http://dx.doi.org/10.1136/neurintsurg-2020-016362DOI Listing
July 2020

Utility of Immediate Postprocedural Cone Beam Computed Tomography Scan in the Detection of Ischemic and Hemorrhagic Complications in Pediatric Neurointerventional Surgery.

World Neurosurg 2020 Mar 9;135:e405-e409. Epub 2019 Dec 9.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA; Division of Neurosurgery, Texas Children's Hospital, Houston, Texas, USA. Electronic address:

Background: Cone beam computed tomography (CBCT) imaging is used commonly in neurointerventional surgery for rapid intraprocedural assessment and planning of intracranial interventions. Our goal was to evaluate the ability of immediate postprocedural CBCT scan in assessing potential complications in pediatric patients.

Methods: A retrospective review was completed to include all pediatric patients at our hospital with an immediate postprocedural CBCT scan with the Artis Q system. Demographic, clinical, and imaging data were examined. CBCT images were reviewed by 3 independent neurointerventionalists to assess ventricular system/subarachnoid spaces, gray-white differentiation, and ischemia or hemorrhage if present. Each assessment was rated qualitatively on a 4-point scale and was compared with conventional computed tomography (cCT) scan when available. Interrater reliability was assessed and radiation dose data were reviewed.

Results: Thirty-five patients were included with an average age of 11.0 ± 5.1 years (median, 10.9; range, 1.1-18 years). Of the patients, 54.3% were boys; 34.3% were Hispanic and 34.3% were non-Hispanic white. Diagnoses included a variety of vascular pathologies. CBCT scan had a mean score of 2.69 ± 0.54 out of 3 for ventricular and subarachnoid space assessment with a combined interrater reliability of 0.82, 1.71 ± 1.38 for hemorrhage with a combined interrater reliability of 1.00, and 0.52 ± 0.60 for gray-white differentiation with a combined interrater reliability of 0.79.

Conclusions: Immediate postprocedural CBCT images were adequate to detect ventricular size/subarachnoid spaces changes and large volume hemorrhage compared with cCT scan in pediatric patients. However, there are limitations using immediate CBCT images to detect small volume hemorrhage and ischemic changes.
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http://dx.doi.org/10.1016/j.wneu.2019.12.003DOI Listing
March 2020

Early postmarket results with PulseRider for treatment of wide-necked intracranial aneurysms: a multicenter experience.

J Neurosurg 2019 Nov 8:1-10. Epub 2019 Nov 8.

Departments of1Neurosurgery and.

Objective: Traditionally, stent-assisted coiling and balloon remodeling have been the primary endovascular treatments for wide-necked intracranial aneurysms with complex morphologies. PulseRider is an aneurysm neck reconstruction device that provides parent vessel protection for aneurysm coiling. The objective of this study was to report early postmarket results with the PulseRider device.

Methods: This study was a prospective registry of patients treated with PulseRider at 13 American neurointerventional centers following FDA approval of this device. Data collected included clinical presentation, aneurysm characteristics, treatment details, and perioperative events. Follow-up data included degree of aneurysm occlusion and delayed (> 30 days after the procedure) complications.

Results: A total of 54 aneurysms were treated, with the same number of PulseRider devices, across 13 centers. Fourteen cases were in off-label locations (7 anterior communicating artery, 6 middle cerebral artery, and 1 A1 segment anterior cerebral artery aneurysms). The average dome/neck ratio was 1.2. Technical success was achieved in 52 cases (96.2%). Major complications included the following: 3 procedure-related posterior cerebral artery strokes, a device-related intraoperative aneurysm rupture, and a delayed device thrombosis. Immediately postoperative Raymond-Roy occlusion classification (RROC) class 1 was achieved in 21 cases (40.3%), class 2 in 15 (28.8%), and class 3 in 16 cases (30.7%). Additional devices were used in 3 aneurysms. For those patients with 3- or 6-month angiographic follow-up (28 patients), 18 aneurysms (64.2%) were RROC class 1 and 8 (28.5%) were RROC class 2.

Conclusions: PulseRider is being used in both on- and off-label cases following FDA approval. The clinical and radiographic outcomes are comparable in real-world experience to the outcomes observed in earlier studies. Further experience is needed with the device to determine its role in the neurointerventionalist's armamentarium, especially with regard to its off-label use.
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http://dx.doi.org/10.3171/2019.5.JNS19313DOI Listing
November 2019

Advances in endovascular neuro-oncology: endovascular selective intra-arterial (ESIA) infusion of targeted biologic therapy for brain tumors.

J Neurointerv Surg 2020 Feb 1;12(2):197-203. Epub 2019 Nov 1.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA

Background: Malignant gliomas continue to have a poor clinical outcome with available therapies. In the past few years, new targeted biologic therapies have been studied, with promising results. However, owing to problems with ineffective IV delivery of these newer agents, an alternative, more direct delivery mechanism is needed. Simultaneously, advancements in neuroendovascular technology have allowed endovascular selective intra-arterial approaches to delivery. This method has the potential to increase drug delivery and selectively target tumor vasculature.

Objective: To review the history of IA therapy for brain tumors, prior failures and successes, the emergence of new technologies and therapies, and the future direction of this young field.

Methods: A comprehensive literature search of two databases (PubMed, Ovid Medline) was performed for several terms including 'brain tumor', 'glioma', and 'endovascular intra-arterial'. Forty-five relevant articles were identified via a systematic review following PRISMA guidelines. Additional relevant articles were selected for further in-depth review. Emphasis was given to articles discussing selective intra-arterial intracranial delivery using microcatheters.

Results: Endovascular intra-arterial therapy with chemotherapy has had mixed results, with currently active trials using temozolomide, cetuximab, and bevacizumab. Prior attempts at IA chemotherapy with older-generation medications did not surpass the efficacy of IV administration. Advances in neuro-oncology have brought to the forefront new targeted biologic therapies.

Conclusions: In this review, we discuss the emerging field of endovascular neuro-oncology, a field that applies modern neuroendovascular techniques to the delivery of new therapeutic agents to brain tumors. The development of targeted therapies for brain tumors has been concurrent with the development of microcatheter technology, which has made superselective distal intracranial arterial access feasible and safe.
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http://dx.doi.org/10.1136/neurintsurg-2019-015137DOI Listing
February 2020

Preinjury Narcotic Use Does Not Affect Treatment for Compartment Syndrome.

J Orthop Trauma 2020 Mar;34(3):e86-e89

Department of Orthopaedic Trauma, Vanderbilt University Medical Center, Nashville, TN.

Objectives: To determine the association of preinjury opioid use on incidence of fasciotomy after lower extremity trauma.

Design: Retrospective case-control study.

Setting: Level 1 trauma center.

Patients/participants: We identified 245 consecutive patients treated with fasciotomy for compartment syndrome of the lower extremity from 2011 to 2016. Of these, 115 were excluded for isolated vascular injury without fracture, age younger than 18 years, out-of-state residence, nontraumatic etiology, and/or incomplete opioid records. Three hundred ninety age- and sex-matched patients with tibial fractures not requiring fasciotomy were selected for comparison.

Intervention: Review of demographics, injury characteristics, and opioid prescriptions.

Main Outcome Measurements: Rate of preinjury narcotic use.

Results: There was no significant difference in chronic opioid use between patients requiring fasciotomy and those who did not (odds ratio = 0.80, 95% confidence interval: 0.43-1.50, P = 0.49). There was no significant difference in average morphine milligram equivalents (MME)/day (66.6 vs. 77.4, P = 0.68). There was no significant difference in active opioid use (odds ratio = 0.76, 95% confidence interval: 0.45-1.29, P = 0.30). There was no significant difference in average MME/day (69.3 vs. 75.6, P = 0.80) for active narcotic users.

Conclusion: There were no differences in the rate or average MME/day of preinjury opioid use between patients with a tibia fracture treated with or without fasciotomy for compartment syndrome. These results indicate that pre-existing opioid use does not interfere with the accurate diagnosis of compartment syndrome in trauma patients. The diagnosis and treatment of compartment syndrome is not affected by preinjury narcotic use and potential associations with opiate-induced hyperalgesia.

Level Of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.1097/BOT.0000000000001650DOI Listing
March 2020

Flow Diversion for Treatment of Intracranial Aneurysms in Pediatric Patients: Multicenter Case Series.

Neurosurgery 2020 07;87(1):53-62

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas.

Background: Though the Pipeline Embolization Device (Medtronic) is approved for use in adults 22 yr and older, the high efficacy and long-term durability of the device is attractive for treatment of intracranial aneurysms in younger patients who often have aneurysms less amenable to traditional endovascular treatments.

Objective: To report technical, angiographic, and clinical outcomes in patients aged 21 or below undergoing flow-diversion treatment for intracranial aneurysms.

Methods: Retrospective review across 16 institutions identified 39 patients aged 21 or below undergoing 46 treatment sessions with Pipeline Embolization Device placement between 2012 and 2018. A total of 50 intracranial aneurysms were treated. Details regarding patient demographics, aneurysm characteristics, treatment considerations, clinical outcomes, and aneurysm occlusion were obtained and analyzed in a multicenter database.

Results: A total of 70% of patients were male. Nonsaccular morphology was seen in half of identified aneurysms. Six aneurysms were giant, and five patients were treated acutely after ruptured presentation. Eight patients were younger than 10 yr of age. Complete aneurysm occlusion was seen in 74% of treated aneurysms. Three aneurysms (6%) were retreated. A total of 83% of patients had a modified Rankin Scale scores of ≤2 at last clinical follow-up. There were 2 early mortalities (4.3%) in the immediate postprocedure period because of rerupture of a treated ruptured aneurysm. No recanalization of a previously occluded aneurysm was observed.

Conclusion: Flow-diversion treatment is a safe and effective treatment for intracranial aneurysms in patients younger than 22 yr. Rates of complete aneurysm occlusion and adverse events are comparable for rates seen in older patients.
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http://dx.doi.org/10.1093/neuros/nyz380DOI Listing
July 2020

Microcatheter delivery of neurotherapeutics: compatibility with mesenchymal stem cells.

J Neurosurg 2019 Sep 6:1-9. Epub 2019 Sep 6.

Departments of1Neurosurgery and.

Objective: Bone marrow-derived human mesenchymal stem cells (BM-hMSCs) have been used in clinical trials for the treatment of several neurological disorders. MSCs have been explored as a delivery modality for targeted viral therapeutic agents in the treatment of intracranial pathologies. Delta-24-RGD, a tumor-selective oncolytic adenovirus designed to target malignant glioma cells, has been shown to be effective in animal models and in a recent clinical trial. However, the most efficient strategy for delivering oncolytic therapies remains unclear. BM-hMSCs have been shown to home toward glioma xenografts after intracarotid delivery. The feasibility of selective intraarterial infusion of BM-hMSCs loaded with Delta-24-RGD (BM-hMSC-Delta-24) to deliver the virus to the tumor is being investigated. To evaluate the feasibility of endovascular intraarterial delivery, the authors tested in vitro the compatibility of BM-hMSC-Delta-24 with a variety of commercially available, clinically common microcatheters.

Methods: BM-hMSCs were cultured, transfected with Delta-24-RGD, and resuspended in 1% human serum albumin. The solution was then injected via 4 common neuroendovascular microcatheters of different inner diameters (Marathon, Echelon-14, Marksman, and SL-10). Cell count and viability after injection through the microcatheters were assessed, including tests of injection velocity and catheter configuration. Transwell assays were performed with the injected cells to test the efficacy of BM-hMSC-Delta-24 activity against U87 glioma cells. BM-hMSC-Delta-24 compatibility was also tested with common neuroendovascular medications: Omnipaque, verapamil, and heparin.

Results: The preinfusion BM-hMSC-Delta-24 cell count was 1.2 × 105 cells/ml, with 98.7% viability. There was no significant difference in postinfusion cell count or viability for any of the catheters. Increasing the injection velocity from 1.0 ml/min to 73.2 ml/min, or modifying the catheter shape from straight to tortuous, did not significantly reduce cell count or viability. Cell count and viability remained stable for up to 5 hours when the cell solution was stored on ice. Mixing BM-hMSC-Delta-24 with clinical concentrations of Omnipaque, verapamil, and heparin prior to infusion did not alter cell count or viability. Transwell experiments demonstrated that the antiglioma activity of BM-hMSC-Delta-24 was maintained after infusion.

Conclusions: BM-hMSC-Delta-24 is compatible with a wide variety of microcatheters and medications commonly used in neuroendovascular therapy. Stem cell viability and viral agent activity do not appear to be affected by catheter configuration or injection velocity. Commercially available microcatheters can be used to deliver stem cell neurotherapeutics via intraarterial routes.
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http://dx.doi.org/10.3171/2019.6.JNS19327DOI Listing
September 2019

Technical and anatomical factors affecting intra-arterial chemotherapy fluoroscopy time and radiation dose for intraocular retinoblastoma.

J Neurointerv Surg 2019 Dec 13;11(12):1273-1276. Epub 2019 Jun 13.

Diagnostic and Interventional Radiology, Baylor College of Medicine, Houston, Texas, USA.

Background: Intra-arterial chemotherapy has an increasingly prominent role in the management of retinoblastoma. One concern regarding this technique is procedural radiation exposure.

Objectives: To examine the effects of our institution's procedural technique on fluoroscopy parameters for patients undergoing intra-arterial chemotherapy infusions for intraocular retinoblastoma. Secondary goals included describing the effect of anatomical variations of the carotid siphon and ophthalmic artery on radiation dose.

Methods: A retrospective review of pediatric patients with retinoblastoma referred to interventional neuroradiology for chemosurgery was performed. Techniques were classified as: A (1.2 Fr or 1.5 Fr microcatheter with continuous verapamil flush, advanced without guide through a 2 Fr sheath) or B (1.5 Fr or 1.7 Fr microcatheter advanced within a 4 Fr base catheter, through a 4 Fr sheath). Statistical analysis was performed to determine if there was a significant difference in fluoroscopy parameters based on technique or due to anatomical variation.

Results: 26 patients were treated with 94 intra-arterial chemotherapy infusions. 34 procedures were performed using technique A and 60 using technique B. Mean fluoroscopy time (4.75 min), fluoroscopy dose (23.3 mGy), and dose-area product (DAP; 85.2 μGy.m) for technique A were significantly lower (p value <0.05) than for technique B, 14.0 min., 191 mGy, and 586 μGy.cm, respectively.

Conclusions: Microcatheter-only technique with continuous verapamil infusion resulted in decreased fluoroscopy times, DAP, and radiation doses at our institution for the treatment of intraocular retinoblastoma. Furthermore, our fluoroscopy times using this technique are the lowest reported in the current literature. Additionally, our anatomical analysis has demonstrated a positive correlation between increasing vessel tortuosity and fluoroscopy times.
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http://dx.doi.org/10.1136/neurintsurg-2019-014910DOI Listing
December 2019

An Evolving Therapy - Dural Venous Sinus Stenting for Idiopathic Intracranial Hypertension.

Can J Neurol Sci 2019 07 10;46(4):469-471. Epub 2019 Jun 10.

Department of Neurology,Baylor College of Medicine,Houston, Texas,USA.

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http://dx.doi.org/10.1017/cjn.2019.49DOI Listing
July 2019

A new set of eyes: development of a novel microangioscope for neurointerventional surgery.

J Neurointerv Surg 2019 Oct 16;11(10):1036-1039. Epub 2019 Mar 16.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA.

Background: Endovascular technological advances have revolutionized the field of neurovascular surgery and have become the mainstay of treatment for many cerebrovascular pathologies. Digital subtraction angiography (DSA) is the 'gold standard' for visualization of the vasculature and deployment of endovascular devices. Nonetheless, with recent technological advances in optics, angioscopy has emerged as a potentially important adjunct to DSA. Angioscopy can offer direct visualization of the intracranial vasculature, and direct observation and inspection of device deployment. However, previous iterations of this technology have not been sufficiently miniaturized or practical for modern neurointerventional practice.

Objective: To describe the evolution, development, and design of a microangioscope that offers both high-quality direct visualization and the miniaturization necessary to navigate in the small intracranial vessels and provide examples of its potential applications in the diagnosis and treatment of cerebrovascular pathologies using an in vivo porcine model.

Methods: In this proof-of-concept study we introduce a novel microangioscope, designed from coherent fiber bundle technology. The microangioscope is smaller than any previously described angioscope, at 1.7 F, while maintaining high-resolution images. A porcine model is used to demonstrate the resolution of the images in vivo.

Results: Video recordings of the microangioscope show the versatility of the camera mounted on different microcatheters and its ability to navigate external carotid artery branches. The microangioscope is also shown to be able to resolve the subtle differences between red and white thrombi in a porcine model.

Conclusion: A new microangioscope, based on miniaturized fiber optic technology, offers a potentially revolutionary way to visualize the intracranial vascular space.
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http://dx.doi.org/10.1136/neurintsurg-2018-014610DOI Listing
October 2019

Intraorbital Arteriovenous Fistula From the Superficial Temporal Artery.

Ophthalmic Plast Reconstr Surg 2019 May/Jun;35(3):e57-e59

Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

Intraorbital arteriovenous fistula is a rare vascular disease characterized by an acquired arteriovenous communication without direct cavernous sinus involvement. Intraorbital arteriovenous fistula may develop slowly and present similarly to other insidious orbitopathies, such as carotid-cavernous fistula. The authors present a case of a superficial temporal artery to superior ophthalmic vein fistula arising in the absence of trauma or prior surgery. This is the first report of a spontaneous intraorbital arteriovenous fistula arising between these vessels and further describes the rare occurrence of intraorbital arteriovenous fistula.
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http://dx.doi.org/10.1097/IOP.0000000000001342DOI Listing
January 2020

Republished: Rotational carotid insufficiency: an unusual cause of bow hunter's syndrome.

J Neurointerv Surg 2019 Nov 23;11(11):e9. Epub 2019 Jan 23.

Department of Radiology, Baylor College of Medicine, Houston, Texas, USA.

We report an unusual case in which physiologic neck rotation impeded perfusion through the internal carotid artery. The patient had a history of prior radical neck surgery and radiation for malignancy. He presented withbow hunter's-like symptoms with transient loss of consciousness and right-sided weakness with left lateral neck rotation. A self-expanding peripheral stent was successfully used to treat the patient by preventing rotatory carotid compression. In select patients with prior neck surgery and radiation, carotid injections should be part of a dynamic cerebral angiogram if the vertebral arteries are unremarkable.
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http://dx.doi.org/10.1136/neurintsurg-2018-014210.repDOI Listing
November 2019

Middle Meningeal Artery Embolization for Chronic Subdural Hematoma: Meta-Analysis and Systematic Review.

World Neurosurg 2019 Feb 24;122:613-619. Epub 2018 Nov 24.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA. Electronic address:

Background: Chronic subdural hematoma is a very common neurosurgical condition. Although conventional surgical methods, such as burr hole irrigation, have been the mainstay of treatment, middle meningeal artery (MMA) embolization has emerged as a promising adjunctive or alternative treatment. The aim of this article was to present a meta-analysis and systematic review of this topic.

Methods: A literature search using keywords "chronic subdural hematoma," "chronic subdural hemorrhage," "refractory subdural hematoma," "refractory subdural hemorrhage," and "middle meningeal artery embolization" was conducted through October 2018. Outcome variables of hematoma recurrence, surgical complications, and modified Rankin Scale score were analyzed and compared between MMA embolization and conventional surgery cohorts.

Results: Three double-arm studies comparing embolization and conventional surgery groups and 6 single-arm case series were identified and analyzed. Hematoma recurrence rate was significantly lower in the embolization group compared with conventional treatment group (2.1% vs. 27.7%; odds ratio = 0.087; 95% confidence interval, 0.026-0.292; P < 0.001; I = 0%); surgical complication rates were similar between groups (2.1% vs. 4.4%; odds ratio = 0.563; 95% confidence interval, 0.107-2.96; P = 0.497; I = 27.5%). Number of patients with modified Rankin Scale score >2 in the embolization (12.5%) versus conventional treatment (9.1%) group showed no statistical difference (P = 0.689). A composite hematoma recurrence rate of 3.6% was found after summing the 6 case series. Composite recurrence and complication rates in the embolization cohorts of the double-arm studies and the case series were lower than literature values for conventional surgical treatments.

Conclusions: MMA embolization is a promising treatment for chronic subdural hematoma. Future randomized clinical trials are needed.
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http://dx.doi.org/10.1016/j.wneu.2018.11.167DOI Listing
February 2019

Rotational carotid insufficiency: an unusual cause of bow hunter's syndrome.

BMJ Case Rep 2018 Oct 14;2018. Epub 2018 Oct 14.

Department of Radiology, Baylor College of Medicine, Houston, Texas, USA.

We report an unusual case in which physiologic neck rotation impeded perfusion through the internal carotid artery. The patient had a history of prior radical neck surgery and radiation for malignancy. He presented withbow hunter's-like symptoms with transient loss of consciousness and right-sided weakness with left lateral neck rotation. A self-expanding peripheral stent was successfully used to treat the patient by preventing rotatory carotid compression. In select patients with prior neck surgery and radiation, carotid injections should be part of a dynamic cerebral angiogram if the vertebral arteries are unremarkable.
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http://dx.doi.org/10.1136/bcr-2018-014210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6194368PMC
October 2018

Cognitive Sequelae of Unruptured and Ruptured Intracranial Aneurysms and their Treatment: Modalities for Neuropsychological Assessment.

World Neurosurg 2018 Dec 30;120:537-549. Epub 2018 Jun 30.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA. Electronic address:

Background: Cognitive sequelae frequently follow subarachnoid hemorrhage (SAH) and include deficits across multiple domains of executive function. This factor affects overall functional outcomes negatively, especially in younger patients. Several clinical correlates predict development and severity of cognitive dysfunction after SAH. Hypothetical mechanisms of cognitive dysfunction in the absence of radiographic lesion include cerebral hypoperfusion and blood breakdown products, resulting in perturbed interneuronal communication and network synchrony, excitotoxicity, and altered microRNA expression.

Methods: The PubMed database was searched for articles discussing cognitive outcomes in patients with unruptured and ruptured intracranial aneurysmal disease, sequelae of treatment, and modalities for neuropsychologic testing.

Results: Treatment of unruptured intracranial aneurysms, although capable of preventing SAH, comes with its own set of complications and may also affect cognitive function. Neuropsychological tests such as the Montreal Cognitive Assessment, Mini-Mental Status Examination, and others have proved useful in evaluating cognitive decline. Studies using functional neurologic imaging modalities have identified regions with altered activation patterns during various cognitive tasks. The sum of research efforts in this field has provided useful insights and an initial understanding of cognitive dysfunction after aneurysm treatment and SAH that should prove useful in guiding and rendering future investigations more fruitful.

Conclusions: Development of finer and more sensitive neuropsychological tests in evaluating the different domains of cognitive function after aneurysm treatment and SAH in general will be useful in accurately determining outcomes after ictus and comparing efficacy of different therapeutic strategies.
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http://dx.doi.org/10.1016/j.wneu.2018.06.178DOI Listing
December 2018

Fast acquisition cone-beam computed tomography: initial experience with a 10 s protocol.

J Neurointerv Surg 2018 Sep 3;10(9):916-920. Epub 2018 Jan 3.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA.

Background: Cone-beam computed tomography (CBCT) facilitates the acquisition of cross-sectional imaging in angiography suites using a rotational C-arm and digital flat panel detectors. The applications are numerous, including evaluation of implanted devices and localization of cerebrovascular lesions. We present and validate the clinical utility of an alternative fast CBCT acquisition protocol in the context of neurovascular device imaging.

Methods: Contrast-enhanced (CE)-CBCT images were acquired using a new 10 s protocol in a phantom head model, swine model, and in patients. The acquisition parameters of both the 10 s and 20 s protocols were exactly the same, except for fewer projections (250 projections in 10 s vs 500 projections in 20 s), resulting in reduced scan time. Image quality was measured quantitatively in a controlled phantom study and qualitatively by blinded reviewers. The latter was performed to assess the image quality of the 10 s protocol pertinent to the device visibility and its apposition to the parent artery.

Results: 10 s CBCT images were comparable to 20 s CBCT in both phantom and animal studies. Of the 25 patient images, the reviewers agreed that they were able to discern the flow diverter struts and assess the apposition in all images. The overall rating for all 10 s images was 4.28 on a 5-point scale. No images were rated as less than 3, which was the average diagnostic quality. The ratings were concordant across three blinded reviewers (κ=0.411). Additionally, contrast and spatial resolution between 10 s and 20 s images were similar in non-human models.

Conclusions: CBCT images of neurovascular devices can be obtained successfully using a 10 s acquisition protocol. In addition, the 10 s protocol offers faster acquisition, thus allowing its use in awake patients and with an added advantage of lower radiation and contrast dose.
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http://dx.doi.org/10.1136/neurintsurg-2017-013475DOI Listing
September 2018

Multimodal Treatment of Intracranial Aneurysms in Children: Clinical Case Series and Review of the Literature.

World Neurosurg 2018 Mar 18;111:e294-e307. Epub 2017 Dec 18.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA. Electronic address:

Background: The management of intracranial aneurysms in the pediatric population presents unique challenges. Cases are rare and tend to be of higher complexity compared with aneurysms in adults. Outcomes in long-term follow-up are not well-characterized. Here we present illustrative case examples to demonstrate key concepts in managing these lesions in the context of the modern neurovascular era.

Methods: Four institutional databases of neurovascular procedures from 2012 to 2017 were reviewed. Patients <18 years old who underwent treatment for intracranial aneurysms were included. Patient characteristics, aneurysm details, treatment information, and angiographic and clinical outcomes were recorded.

Results: Ten cases of intracranial aneurysms in 9 children were identified. Management included direct clipping, trapping and bypass, endovascular coil embolization, endovascular vessel sacrifice, and flow diversion.

Conclusions: The management of intracranial aneurysms in pediatric patients requires special considerations, from the diagnostic phase to treatment methods and follow-up regimen. These are ideally considered by a multidisciplinary team, with expertise from pediatric neurosurgeons, cerebrovascular neurosurgeons, and neurointerventionalists.
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http://dx.doi.org/10.1016/j.wneu.2017.12.057DOI Listing
March 2018

Neurological Imaging for Hemifacial Spasm.

Authors:
Stephen R Chen

Int Ophthalmol Clin 2018 ;58(1):97-109

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http://dx.doi.org/10.1097/IIO.0000000000000212DOI Listing
January 2019

Anterior Inferior Cerebellar Artery Strokes Based on Variant Vascular Anatomy of the Posterior Circulation: Clinical Deficits and Imaging Territories.

J Stroke Cerebrovasc Dis 2018 Apr 14;27(4):e59-e64. Epub 2017 Nov 14.

Diagnostic Radiology, MD Anderson Cancer Center, Houston, Texas.

We report imaging findings of 3 patients with anterior inferior cerebellar artery (AICA) infarcts who presented with atypical clinical findings of cerebellar strokes. AICA strokes are rare, and diagnosis can be difficult because of the high variability of the posterior circulation vascular anatomy. We describe the embryology and variant anatomy of AICA so that clinicians can understand and recognize the patterns of these infarcts.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2017.10.007DOI Listing
April 2018

Flow diversion for anterior choroidal artery (AChA) aneurysms: a multi-institutional experience.

J Neurointerv Surg 2018 Jul 31;10(7):634-637. Epub 2017 Oct 31.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA.

Background: Anterior choroidal artery (AChA) aneurysms represent a small subset of cerebral aneurysms. The Pipeline Embolization Device (PED) has been successfully applied to various aneurysms of the supraclinoid internal carotid artery (ICA). The treatment of these aneurysms requires special attention due to the eloquent territory supplied by the AChA. We report the largest and first dedicated series of flow diversion treatment of AChA aneurysms.

Methods: Four institutional neurointerventional databases were reviewed for cases of intracranial aneurysms treated with PED. Patient and aneurysm data as well as angiographic imaging were reviewed for all cases of AChA aneurysms treated with PED. AChA aneurysms were defined as aneurysms distal to the AChA and proximal to the ICA terminus, with or without the incorporation of the AChA.

Results: Eighteen AChA aneurysms were treated during the study period. All aneurysms were successfully treated with a mean follow-up of 19.1 months. The large majority of aneurysms (15/18, 83.3%) were completely obliterated. No patients suffered from intra- or post-procedural complications. A1 stenosis was a common occurrence, seen in 10 of 16 (62.5%) covered anterior cerebral arteries (ACAs), although all were asymptomatic. All AChAs remained patent at last follow-up.

Conclusions: The PED can be used successfully in AChA aneurysms with a good safety and efficacy profile. All AChAs remained patent. Collateral flow networks, especially for the ACA, affect long-term branch vessel patency. Treatment with PED for AChA aneurysms appears to be a reasonable option to consider and should be evaluated in a larger cohort.
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http://dx.doi.org/10.1136/neurintsurg-2017-013466DOI Listing
July 2018

Flow diversion for the treatment of posterior inferior cerebellar artery aneurysms: a novel classification and strategies.

J Neurointerv Surg 2018 Jul 20;10(7):663-668. Epub 2017 Oct 20.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA.

Background: The pipeline embolization device (PED) is frequently used in the treatment of anterior circulation aneurysms, especially around the carotid siphon, with generally excellent results. However, treatment of posterior inferior cerebellar artery (PICA) aneurysms with flow diversion (FD) has not been specifically described or discussed. While there are reports of treating PICA aneurysms using placement of FD stents in the vertebral artery, there are no reports of treating these lesions by placement of flow diverting stents in the PICA vessel itself. Due to the unique anatomy and morphology of these aneurysms, it requires special attention. We assessed our multi-institutional experience treating these lesions, including the first reported cases of the PED placed within the PICA.

Methods: Institutional databases of neuroendovascular procedures were reviewed for cases of intracranial aneurysms treated with the PED. Patient and aneurysm data as well as angiographic imaging were reviewed for all cases of PICA aneurysms treated with the PED. PICA aneurysms were defined as aneurysms that involved the PICA. Vertebral aneurysms without disease in the PICA were excluded from the study.

Results: 10 PICA aneurysms were treated during the study period. These were classified based on their morphology and location into two main types and five total subtypes for consideration of treatment with flow diversion. All aneurysms were successfully treated, with 8/10 completely obliterated and 2 with a partial reduction in size. Three patients had the PED placed entirely in the PICA and no patient suffered from a medullary or cerebellar stroke. All PEDs were patent and all patients were independent at the last follow-up.

Conclusions: The PED may be used successfully to treat select aneurysms of the PICA. We present the first described cases of successful PED treatment of PICA aneurysms with direct placement of the PED in the PICA vessel itself. The proposed classification system aids in that selection.
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http://dx.doi.org/10.1136/neurintsurg-2017-013427DOI Listing
July 2018

Pediatric Intracranial Aneurysms: Considerations and Recommendations for Follow-Up Imaging.

World Neurosurg 2018 Jan 3;109:418-431. Epub 2017 Oct 3.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA. Electronic address:

Background: Pediatric intracranial aneurysms (IAs) are rare. Compared with adult IAs, they are more commonly giant, fusiform, or dissecting. Treatment often proves more complex, and recurrence rate and de novo aneurysmogenesis incidence are higher. A consensus regarding the most appropriate algorithm for following pediatric IAs is lacking.

Methods: We sought to generate recommendations based on the reported experience in the literature with pediatric IAs through a thorough review of the PubMed database, discussion with experienced neurointerventionalists, and our own experience.

Results: Digital subtraction angiography (DSA) was utilized immediately post-operatively for microsurgically-clipped and endovascularly-treated IAs, at 6-12 months postoperatively for endovascularly-treated IAs, and in cases of aneurysmal recurrence or de novo aneurysmogenesis discovered by non-invasive imaging modalities. Computed tomographic angiography was the preferred imaging modality for long-term follow-up of microsurgically clipped IAs. Magnetic resonance angiography (MRA) was the preferred modality for following IAs that were untreated, endovascularly-treated, or microsurgically-treated in a manner other than clipping.

Conclusions: We propose incidental untreated IAs to be followed by magnetic resonance angiography without contrast enhancement. Follow-up modality and interval for treated pediatric IAs is determined by initial aneurysmal complexity, treatment modality, and degree of posttreatment obliteration. Recurrence or de novo aneurysmogenesis requiring treatment should be followed by digital subtraction angiography and appropriate retreatment. Computed tomography angiography is preferred for clipped IAs, whereas contrast-enhanced magnetic resonance angiography is preferred for lesions treated endovascularly with coil embolization and lesions treated microsurgically in a manner other than clipping.
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http://dx.doi.org/10.1016/j.wneu.2017.09.150DOI Listing
January 2018

Prolapse of the Pipeline embolization device in aneurysms: incidence, management, and outcomes.

Neurosurg Focus 2017 Jun;42(6):E16

Departments of 1 Neurosurgery and.

OBJECTIVE The Pipeline embolization device (PED) is frequently used in the treatment of anterior circulation aneurysms, especially around the carotid siphon, with generally excellent results. However, the PED has its own unique technical challenges, including the occurrence of device foreshortening or migration leading to prolapse into the aneurysm. The authors sought to determine the incidence of this phenomenon, the rescue strategies, and outcomes. METHODS Four institutional databases of neuroendovascular procedures were reviewed for cases of intracranial aneurysms treated with PEDs. Patient and aneurysm data as well as angiographic imaging were reviewed for all cases involving device prolapse into the aneurysm. RESULTS A total of 413 intracranial aneurysms were treated with PEDs during the study period, by 5 neurointerventionalists. Large and giant aneurysms (≥ 2 cm) accounted for 32 of these aneurysms. Among these 32 PEDs, prolapse into the aneurysm occurred in 3 patients, with 1 of these PEDs successfully rescued and the other 2 left in situ. No patients suffered any severe complications. The 2 patients in whom the PEDs were left in situ remained on antiplatelet therapy. CONCLUSIONS The PED may foreshorten or migrate during or after deployment, leading to prolapse into the aneurysm. This phenomenon appears to be associated with large and giant aneurysms, vessel tortuosity, short landing zones, and use of balloon angioplasty. Future study and follow-up is needed to further evaluate this phenomenon, but some of the observations and techniques described in this paper may help to prevent or salvage prolapsed devices.
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http://dx.doi.org/10.3171/2017.3.FOCUS1738DOI Listing
June 2017

Development of a recalcitrant, large clot burden, bifurcation occlusion model for mechanical thrombectomy.

Neurosurg Focus 2017 Apr;42(4):E6

Departments of 1 Neurosurgery and.

OBJECTIVE Stroke is a major cause of disability and death in adults. Several large randomized clinical trials have shown the significant benefit of mechanical thrombectomy with modern stent retrievers in the treatment of large-vessel occlusions. However, large clots located at bifurcations remain challenging to treat. An in vivo model of these recalcitrant clots needs to be developed to test future generations of devices. METHODS Autologous blood was drawn from anesthetized swine via a femoral sheath. Blood was then mixed with thrombin, calcium chloride, and saline, and injected into silicone tubing to form cylindrical clots in the standard fashion. Matured clots were then delivered in an unfragmented fashion directly into the distal extracranial vasculature, at branch points where vessel sizes mimic the human middle cerebral artery, by using Penumbra aspiration tubing and the Penumbra ACE68 reperfusion catheter. RESULTS A total of 5 adult swine were used to develop the model. The techniques evolved during experiments in the first 3 animals, and the last 2 were used to establish the final model. In these 2 swine, a total of 8 autologous clots, 15-20 mm, were injected directly into 8 distal extracranial vessels at branch points to mimic a bifurcation occlusion in a human. All clots were delivered directly at a distal bifurcation or trifurcation in an unfragmented fashion to cause an occlusion. Ten revascularization attempts were made, and none of the branch-point occlusions were fully revascularized on the first attempt. CONCLUSIONS Using novel large-bore distal access catheters, large unfragmented clots can be delivered into distal extracranial vessels in a swine occlusion model. The model mimics the clinical situation of a recalcitrant bifurcation occlusion and will be valuable in the study of next-generation stroke devices and in training settings.
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http://dx.doi.org/10.3171/2017.1.FOCUS16501DOI Listing
April 2017

Occipital Artery Pseudoaneurysm After Posterior Fossa Craniotomy.

World Neurosurg 2017 Feb 23;98:868.e1-868.e4. Epub 2016 Dec 23.

Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA. Electronic address:

Background: Pseudoaneurysms of scalp arteries have been reported in rare cases after iatrogenic injury; however, they are far more commonly seen after traumatic injuries. They are usually associated with the superficial temporal artery; however, there have been a few reports of psuedoaneurysms of the occipital artery (OA).

Case Description: We present a unique case of an OA pseudoaneurysm presenting with delayed postoperative hemorrhage after a retrosigmoid craniotomy. The pseudoaneurysm was treated by coil embolization.

Conclusions: The patient recovered fully after endovascular embolization. Other treatment options for pseudoaneurysms of facial, temporal, and scalp arteries include surgical clipping/trapping with excision, Hunterian ligation, or direct compression. Pseudoaneurysms of extracranial scalp arteries are rare and most often caused by traumatic compression of the artery against a bony ridge. Despite their rarity, pseudoaneurysms secondary to iatrogenic injury to extracranial arteries should be considered in the differential diagnosis in patients presenting with delayed incisional pain, redness, and swelling.
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http://dx.doi.org/10.1016/j.wneu.2016.12.050DOI Listing
February 2017

Evaluation of C-arm CT metal artifact reduction algorithm during intra-aneurysmal coil embolization: Assessment of brain parenchyma, stents and flow-diverters.

Eur J Radiol 2016 Jul 27;85(7):1312-21. Epub 2016 Apr 27.

Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA.

Purpose: Flat panel C-arm CT images acquired in the interventional suite provide valuable information regarding brain parenchyma, vasculature, and device status during the procedure. However, these images often suffer from severe streak artifacts due to the presence of metallic objects such as coils. These artifacts limit the capability to make diagnostic inferences and thus need to be reduced for better image interpretation. The main purpose of this paper is to systematically evaluate the accuracy of one such C-arm CT based metal artifact reduction (MAR) algorithm and to demonstrate its usage in both stent and flow diverter assisted coil embolization procedures.

Methods: C-arm CT images routinely acquired in 24 patients during coil embolization procedure (stent-assisted (12) and flow-diverter assisted (12)) were included in this study in a retrospective fashion. These images were reconstructed without and with MAR algorithm on an offline workstation and compared using quantitative image analysis metrics. This analysis was carried out to assess the improvements in both brain parenchyma and device visibility with MAR algorithm. Further, ground truth reference images from phantom experiments and clinical data were used for accurate assessment.

Results: Quantitative image analysis of brain parenchyma showed uniform distribution of grayscale values and reduced image noise after MAR correction. The line profile plot analysis of device profile in both phantom and clinical data demonstrated improved device visibility with MAR correction.

Conclusions: MAR algorithm successfully reduced streak artifacts from coil embolization in all cases, thus allowing more accurate assessment of devices and adjacent brain parenchyma.
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http://dx.doi.org/10.1016/j.ejrad.2016.04.013DOI Listing
July 2016

Radiology corner. Traumatic carotid pseudoaneurysm post gun shot wound to the head / neck.

Mil Med 2008 May;173(5):xv-xvi

Misawa Air Force Medical Center, Japan.

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May 2008