Employing magnetic resonance histology for precision chronic limb-threatening ischemia treatment planning.

OBJECTIVE: Recent randomized controlled trials have demonstrated a notable prevalence of immediate technical failures in percutaneous vascular interventions (PVIs) for complex arterial lesions associated with chronic limb-threatening ischemia. Current imaging modalities present inherent limitations in identifying these lesions, making it challenging to determine the most suitable candidates for PVI. We present a novel preprocedural magnetic resonance imaging (MRI) histology protocol for identifying lesions that might present a higher rate of immediate and midterm PVI failure. METHODS: We enrolled 22 patients (13 females, average age 65.8 ± 9.72 years) scheduled for PVI were prospectively and underwent 3T MRI using ultrashort echo time and steady-state free precession contrasts to characterize target lesions before PVI. Lesions were scored as hard if >50% of the lumen was occluded by hard components (calcium/dense collagen) on MRI in the hardest cross-section. Two readers evaluated MRI datasets. Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease (TASC)/Global Limb Anatomic Staging System (GLASS)/Wound, Ischemia and Foot infection scoring was performed based on intraprocedural angiograms and chart review. The relationship between MRI scoring, TASC/GLASS scoring, and procedural outcomes was investigated using univariate analysis. Midterm follow-up (revascularization and amputation rates) was recorded at 3 and 6 months after the intervention. RESULTS: Our cohort of 22 patients yielded 40 target lesions. Five lesions were excluded (two for nondiagnostic image quality; three PVIs were ultimately diagnostic only). Six lesions (17%) were scored as hard. MRI-scored hard lesions had a higher proportion of immediate technical failure (hard vs soft 83% [5/6] vs 3% [1/29]; P < .001). Hard vs soft MRI scoring was the only factor significantly associated with immediate PVI technical success (P < .001), as opposed to TASC/GLASS scoring. Both at 3 months and 6 months after PVI, the reintervention rate was significantly higher among those lesions which were scored hard on MRI (3 months hard, 80% vs soft, 16% [P =.011]; 6 months hard, 80% vs soft, 27%; P = .047). CONCLUSIONS: MRI histology could be a valuable tool for optimizing PVI patient selection and treatment strategies.

Image Guidance Techniques and Treatment Approach Optimization in the Management of Type-II Endoleak After Endovascular Aortic Aneurysm Repair.

BACKGROUND: Over the past 3 decades endovascular aortic aneurysm repair emerged as the primary approach for abdominal aortic aneurysm management, however the occurrence of endoleak following endograft implantation imposes a high toll on patients and hospitals alike. The early diagnosis and appropriate treatment of endoleaks is associated with better outcomes, which calls for more advanced imaging and a standardized approach for endoleak diagnosis and management following endovascular aortic aneurysm repair. Although conventional strategy with non-targeted deployment of coils and embolic material in the aneurysm sac is considered to be the standard approach in many hospitals, it may not prove to be a viable option, given that it affects any further follow-up imaging in the event of sub-optimal therapy and consequent recurrence. METHODS: Based on our tertiary aortic referral center experience we summarize and describe strategies for optimal selection of various treatment approaches for Type-II Endoleak management including endovascular, percutaneous and laparoscopic approaches with particular focus on intraoperative image guidance techniques. RESULTS: After failed conventional endovascular embolization attempt we recommend specific complex type II endoleak management approaches based on the location of the endoleak within the aneurysm sac along the x, y and z axis. A transabdominal or laparoscopic approach enable treatment in endoleaks located in the anterior portion of the sac. Endoleaks in the posterior portion of the sac could be treated using the transcaval or the translumbar approach, depending on whether the endoleak is situated on the left or the right side. Alternative strategies should be considered if patient anatomy does not allow for either transcaval or translumbar approach. The transgraft technique is reserved for endoleaks located in the cranial portion of the sac, while the perigraft approach could present a means of treatment for endoleaks situated in the caudal portion of the aneurysm sac. CONCLUSION: We encourage establishing a patient specific treatment plan in accordance with individual anatomy based on cross sectional imaging modality (time resolved dynamic imaging in selected cases) and intraoperative image guidance to provide a safe and accurate endoleak localization and embolization for patients undergoing type II endoleak treatment.

Dynamic, Time-Resolved CT Angiography After EVAR: A Quantitative Approach to Accurately Characterize Aortic Endoleak Type and Identify Inflow Vessels.

PURPOSE: Our purpose was to study the accuracy of dynamic computed tomography angiography (d-CTA) in characterizing endoleak type, inflow vessels as compared with digital subtraction angiography (DSA) using qualitative and quantitative analysis. METHODS: Between March 2019 and January 2021, all patients who underwent d-CTA imaging after EVAR were retrospectively reviewed. Two blinded independent reviewers qualitatively reviewed d-CTA and DSA images. Quantitative region of interest (ROI) analysis was performed by measuring time-resolved contrast enhancement within the aorta and endoleak lesion(s) in the aneurysm sac. Differences between time-to-peak enhancement (Δ TTP) across different ROIs were quantified. RESULTS: A total of 48 patients underwent d-CTA during the study period, of whom 24 patients had abdominal EVAR and DSA imaging for comparison. Qualitative review of DSA imaging showed type I (n=4), type II (n=16), and type III (n=2) and no endoleak (n=2). In 23 of 24 patients (95.8%), d-CTA findings correlated with DSA findings for endoleak type. One patient had a type III endoleak that was demonstrated only in d-CTA (arising from defect in polymer sealing ring of Ovation stent graft) imaging. In type II endoleak cases, d-CTA identified more inflow vessels than DSA imaging (33 vs 21 vessels, p=0.010). Quantitative analysis showed mean (±SD) Δ TTP values for type I endoleak as 1.8 (±1.8) seconds, type II as 9.6 (±3.5) seconds, and for type III endoleak as 5.6 (±1.3) seconds. CONCLUSION: Dynamic CTA can accurately characterize aortic endoleak type, inflow vessels as compared with DSA imaging. Quantitative parameters such as Δ TTP enhancement can help better differentiate endoleak types and provide an objective approach to endoleak diagnosis.

Dynamic Computed Tomography Angiography is More Accurate in Diagnosing Endoleaks than Standard Triphasic Computed Tomography Angiography and Enables Targeted Embolization.

BACKGROUND: The primary objective was to compare the accuracy of dynamic computed tomography (CT) angiography (d-CTA) with standardized triphasic contrast enhanced CT angiography (t-CTA) in diagnosing endoleak type after endovascular aortic repair (EVAR) using digital subtraction angiography (DSA) as reference standard. The secondary objective was to study the impact of d-CTA on image fusion-guided endoleak embolization. METHODS: A retrospective review of patients who underwent d-CTA imaging after EVAR between March 2019 and July 2021 was performed. Deidentified images were independently reviewed by two-two blinded readers to document endoleak type and target vessels. An impact of d-CTA-guided embolization was evaluated by a number of planning angiograms, radiation exposure, and accuracy of target vessel overlay. RESULTS: During the study period, 52 patients underwent d-CTA and 19 had all 3 modalities available for analysis. DSA imaging confirmed 4 (21.0%) type-I, 14 (73.7%) type-II, and 1 (5.3%) type-III endoleak. Findings from d-CTA matched with DSA in 19/19 cases (100%), whereas t-CTA matched in 14/19 cases (73.7%). In type-II endoleaks, the number of target vessels identified by d-CTA, t-CTA, and DSA were 23, 17, and 16, respectively. Mean dose-length product from d-CTA and t-CTA was 1,445 ± 551 and 1,612 ± 530 mGy × cm (P = 0.26). Nine patients underwent d-CTA-guided type-II endoleak embolization, using a median of 1 (range: 1-4) planning angiogram before embolization using 21.6 (± 8.7)% of total procedural radiation dose. Target vessel overlay was accurate in 9/9 (100%) cases. CONCLUSIONS: Dynamic, time-resolved CTA is more accurate compared to standardized triphasic contrast enhanced CTA in diagnosing endoleak type after EVAR. In type-II endoleak, d-CTA better identified target vessels and enabled safe, targeted embolization.

Dynamic, Time-Resolved Computed Tomography Angiography Technique to Characterize Aortic Endoleak Type, Inflow and Provide Guidance for Targeted Treatment.

PURPOSE: To illustrate dynamic, time-resolved CTA (d-CTA) imaging technique in characterizing aortic endoleak type/inflow using quantitative parameters and its value in providing image guidance for targeted treatment approach. TECHNIQUE: Dedicated endoleak protocol involved acquiring multiple time-resolved contrast enhanced scans using third-generation CT scanner (Somatom Force®, Siemens Healthineers). Parameters such as scan field of view (FOV), kV, number/timing of scans were customized based on patient's body-mass-index, timing bolus, and prior imaging findings. D-CTA image datasets were evaluated qualitatively and quantitatively using time-attenuation curves (TAC) analysis after motion correction using a dedicated software (syngo.via®, Siemens). D-CTA findings from 4 illustrative cases demonstrating type I, type II (inferior mesenteric and lumbar artery inflow), and type III endoleak were illustrated. TAC analysis with time to peak parameter enabled better characterization of endoleak type and inflow. During endoleak intervention, target vessels from d-CTA images were electronically annotated and overlaid on fluoroscopy using 2D-3D image fusion to provide image guidance for targeted treatment. CONCLUSION: D-CTA imaging with TAC analysis characterizes aortic endoleak type and inflow, in addition to providing image guidance for targeted endoleak treatment. Such dynamic, time-resolved imaging techniques may provide further insights into understanding aortic endoleak that remains an Achilles heel for endovascular aortic aneurysm repair.

Added Value of Selective Intra-arterial Cone-Beam CT Angiography in the Management of Visceral Artery Aneurysms.

PURPOSE: The aim of this study is to evaluate the value of selective intra-arterial cone-beam computed tomography angiography (CBCTA) relative to conventional computed tomography angiography (CTA) in understanding visceral artery aneurysm (VAA) morphology, and its impact on treatment planning. MATERIALS AND METHODS: Between January 2017 and August 2021, all patients who had a diagnosis of VAA and underwent intraoperative CBCTA imaging were retrospectively reviewed. Impact on treatment decisions, optimal C-arm angulations derived from CBCTA, and additional radiation exposure were reported. Two blinded independent reviewers qualitatively reviewed CBCTA and conventional CTA images. A 5-point Likert scale (1=poor image quality, 5=excellent image quality) was used to assess the overall image quality of each modality. Number of vessels arising from the aneurysm sac was counted. RESULTS: A total of 16 patients had a diagnosis of VAA during the study period, of whom 10 patients had intraoperative CBCTA and conventional CTA available for review. Out of 10 patients, 7 underwent successful endovascular treatment, 2 were deemed not amenable for endovascular embolization based on intraoperative CBCTA findings, and 1 had resolved pseudoaneurysm. Total fluoroscopy time and radiation dose (dose area product [DAP] and skin dose) for all procedures were 27.7 ± 19.9 minutes, 28 362 (±18 651) µGy*m2, and 1879 (±1734) mGy, respectively. Radiation exposure from CBCTA (DAP and skin dose) was 5703 (±3967) µGy*m2 and 223.6 (±141.3) mGy, respectively. In patients who underwent endovascular treatment, the proportional DAP from CBCTA was 18.3% (±15.3%) of the total procedural radiation dose. Qualitative rating of overall image quality of CBCTA images was superior to CTA images (mean score: 4.55 vs 3, p<0.001). More branch vessels arising from the VAA were identified by all reviewers in CBCTA as compared with conventional CTA (median, min-max: 3, 0-4 vs 2,1-3 vessels). CONCLUSION: Intraoperative CBCTA after selective intra-arterial contrast injection, with better spatial resolution, provided better delineation of visceral aneurysm morphology as compared with conventional, intravenous CTA and enabled optimal treatment planning at a reasonable additional radiation exposure. CLINICAL IMPACT: Visceral artery aneurysms (VAA) are often diagnosed incidentally by conventional computed tomographic angiography (CTA). Endovascular treatment typically requires selective angiographies at multiple projections to better understand aneurysm morphology, location, and efferent branch vessels. Intra-arterial cone-beam CT angiography (CBCTA) for VAA has the advantage of selective contrast opacification, better spatial resolution, and three-dimensional/multi-planar visualization of aneurysm morphology. In addition, CBCTA enables identification of optimal C-arm working projection for subsequent endovascular treatment. The aim of this study is to evaluate the value of intraoperative CBCTA relative to conventional CTA in understanding visceral artery aneurysm morphology and its impact on treatment planning.

Evaluation of Robotic-Assisted Carotid Artery Stenting in a Virtual Model Using Motion-Based Performance Metrics.

PURPOSE: Robotic-assisted carotid artery stenting (CAS) cases have been demonstrated with promising results. However, no quantitative measurements have been made to compare manual with robotic-assisted CAS. This study aims to quantify surgical performance using tool tip kinematic data and metrics of precision during CAS with manual and robotic control in an ex vivo model. MATERIALS AND METHODS: Transfemoral CAS cases were performed in a high-fidelity endovascular simulator. Participants completed cases with manual and robotic techniques in 2 different carotid anatomies in random order. C-arm angulations, table position, and endovascular devices were standardized. Endovascular tool tip kinematic data were extracted. We calculated the spectral arc length (SPARC), average velocity, and idle time during navigation in the common carotid artery and lesion crossing. Procedural time, fluoroscopy time, movements of the deployed filter wire, precision of stent, and balloon positioning were recorded. Data were analyzed and compared between the 2 modalities. RESULTS: Ten participants performed 40 CAS cases with a procedural success of 100% and 0% residual stenosis. The median procedural time was significantly higher during the robotic-assisted cases (seconds, median [interquartile range, IQR]: 128 [49.5] and 161.5 [62.5], p=0.02). Fluoroscopy time differed significantly between manual and robotic-assisted procedures (seconds, median [IQR]: 81.5 [32] and 98.5 [39.5], p=0.1). Movement of the deployed filter wire did not show significant difference between manual and robotic interventions (mm, median [IQR]: 13 [10.5] and 12.5 [11], p=0.5). The postdilation balloon exceeded the margin of the stent with a median of 2 [1] mm in both groups. Navigation with robotic assistance showed significantly lower SPARC values (-5.78±3.14 and -8.63±3.98, p=0.04) and higher idle time values (8.92±8.71 and 3.47±3.9, p=0.02) than those performed manually. CONCLUSIONS: Robotic-assisted and manual CAS cases are comparable in the precision of stent and balloon positioning. Navigation in the carotid artery is associated with smoother motion and higher idle time values. These findings highlight the accuracy and the motion stabilizing capability of the endovascular robotic system. CLINICAL IMPACT: Robotic assistance in the treatment of peripheral vascular disease is an emerging field and may be a tool for radiation protection and the geographic distribution of endovascular interventions in the future. This preclinical study compares the characteristics of manual and robotic-assisted carotid stenting (CAS). Our results highlight, that robotic-assisted CAS is associated with precise navigation and device positioning, and smoother navigation compared to manual CAS.

Transcarotid access for remote robotic endovascular neurointerventions: a cadaveric proof-of-concept study.

OBJECTIVE: The purpose of this proof-of-concept study was to demonstrate the setup and feasibility of transcarotid access for remote robotic neurointerventions in a cadaveric model. METHODS: The interventional procedures were performed in a fresh-frozen cadaveric model using an endovascular robotic system and a robotic angiography imaging system. A prototype remote, robotic-drive system with an ethernet-based network connectivity and audio-video communication system was used to drive the robotic system remotely. After surgical exposure of the common carotid artery in a cadaveric model, an 8-Fr arterial was inserted and anchored. A telescopic guiding sheath and catheter/microcatheter combination was modified to account for the "workable" length with the CorPath GRX robotic system using transcarotid access. RESULTS: To simulate a carotid stenting procedure, a 0.014-inch wire was advanced robotically to the extracranial internal carotid artery. After confirming the wire position and anatomy by angiography, a self-expandable rapid exchange nitinol stent was loaded into the robotic cassette, advanced, and then deployed robotically across the carotid bifurcation. To simulate an endovascular stroke recanalization procedure, a 0.014-inch wire was advanced into the proximal middle cerebral artery with robotic assistance. A modified 2.95-Fr delivery microcatheter (Velocity, Penumbra Inc.) was loaded into the robotic cassette and positioned. After robotic retraction of the wire, it was switched manually to a mechanical thrombectomy device (Solitaire X, Medtronic). The stentriever was then advanced robotically into the end of the microcatheter. After robotic unfolding and short microcatheter retraction, the microcatheter was manually removed and the stent retriever was extracted using robotic assistance. During intravascular navigation, the device position was guided by 2D angiography and confirmed by 3D cone-beam CT angiography. CONCLUSIONS: In this proof-of-concept cadaver study, the authors demonstrated the setup and technical feasibility of transcarotid access for remote robot-assisted neurointerventions such as carotid artery stenting and mechanical thrombectomy. Using transcarotid access, catheter length modifications were necessary to achieve "working length" compatibility with the current-generation CorPath GRX robotic system. While further improvements in dedicated robotic solutions for neurointerventions and next-generation thrombectomy devices are necessary, the transcarotid approach provides a direct, relatively rapid access route to the brain for delivering remote stroke treatment.

Clinical Experience with the Gore Hybrid Vascular Graft in Complex Revascularizations Demonstrates Safety and Efficacy.

BACKGROUND: Arterial revascularizations can present significant challenges when vessels are disadvantaged and advances in technology present the surgeon with innovative opportunities. A number of studies have used the GORE® Hybrid Vascular Graft (GHVG), and we have been using this device in arterial revascularizations since it came to market. The aim of this study is therefore to present a large single-center experience using the GHVG. This series presents patients with complex revascularizations in multiple vascular beds. METHODS: We retrospectively analyzed a single-center series of 43 patients who received a total of 56 GHVGs in complex revascularization procedures at Houston Methodist Hospital from March 2012 to April 2017. We excluded 5 patients (7 grafts in total) because of loss of follow-up. An additional 8 patients were excluded from the analysis (11 grafts in total) secondary to mortalities unrelated to their grafts (7 patients died during index hospitalization and 1 patient died shortly after discharge). RESULTS: Our results demonstrated an 18-month primary patency, assisted primary patency, and secondary patency of 82, 86, and 96%, respectively. These complex revascularizations included a total of 56 devices placed. GHVGs were placed in the external iliac artery (27/56), renal artery (12/56), common femoral artery (6/56), superficial femoral artery (4/56), common iliac artery (3/56), grafts (3/56), profunda femoris artery (1/56), and the superior mesenteric artery (1/56). Early mortality in patients (7/8) was because of the nature of their disease and not related to the surgical intervention. CONCLUSIONS: The GHVG has the ability to create a sutureless anastomosis in a disadvantaged vessel or to promote a potentially better outcome by either avoiding prolonged ischemia to visceral branches or avoiding extensive abdominal or retroperitoneal exposure in an iliofemoral bypass. These results demonstrate the value of the GHVG in complex revascularizations not amenable to traditional open surgical bypass. LEVEL OF EVIDENCE: IV.

Functionalization of endovascular devices with superparamagnetic iron oxide nanoparticles for interventional cardiovascular magnetic resonance imaging.

Presently, cardiovascular interventions such as stent deployment and balloon angioplasty are performed under x-ray guidance. However, x-ray fluoroscopy has poor soft tissue contrast and is limited by imaging in a single plane, resulting in imprecise navigation of endovascular instruments. Moreover, x-ray fluoroscopy exposes patients to ionizing radiation and iodinated contrast agents. Magnetic resonance imaging (MRI) is a safe and enabling modality for cardiovascular interventions. Interventional cardiovascular MR (iCMR) is a promising approach that is in stark contrast with x-ray fluoroscopy, offering high-resolution anatomic and physiologic information and imaging in multiple planes for enhanced navigational accuracy of catheter-based devices, all in an environment free of radiation and its deleterious effects. While iCMR has immense potential, its translation into the clinical arena is hindered by the limited availability of MRI-visible catheters, wire guides, angioplasty balloons, and stents. Herein, we aimed to create application-specific, devices suitable for iCMR, and demonstrate the potential of iCMR by performing cardiovascular catheterization procedures using these devices. Tools, including catheters, wire guides, stents, and angioplasty balloons, for endovascular interventions were functionalized with a polymer coating consisting of poly(lactide-co-glycolide) (PLGA) and superparamagnetic iron oxide (SPIO) nanoparticles, followed by endovascular deployment in the pig. Findings from this study highlight the ability to image and properly navigate SPIO-functionalized devices, enabling interventions such as successful stent deployment under MRI guidance. This study demonstrates proof-of-concept for rapid prototyping of iCMR-specific endovascular interventional devices that can take advantage of the capabilities of iCMR.

Proposed Magnetic Resonance Imaging Criteria to Diagnose Intramural Haematoma and to Predict Aortic Healing after Acute Type B Aortic Syndrome.

OBJECTIVE: Type B acute aortic syndrome (AAS) encompasses aortic dissection (AD) and intramural haematoma (IMH), the diagnosis, evolution, and treatment of which are subject to controversies. The aim of this pilot investigation was to assess the ability of specific magnetic resonance imaging (MRI) criteria to differentiate AD from IMH and predict optimal aortic remodeling following AAS. METHODS: In this retrospective study, all patients presenting between 2008 and 2015 with type B AAS, who had diagnostic MRI following admission, were included. Three MRI criteria were proposed to identify IMH: (i) no visualised entry tear; (ii) no contrast uptake in the aortic lesion on the first pass angiographic run; (iii) no contrast uptake in the aortic lesion on the equilibrium phase T1 sequence. On each patient's diagnostic and follow up imaging studies, the volume of (i) false lumen/IMH, (ii) total aorta, and (iii) true lumen were calculated. Using the Wilcoxon signed rank test, the evolution of these volumes according to the presence or absence of the aforementioned criteria were compared. RESULTS: Of 39 patients, in seven all MRI criteria were positive (group IMH) and 32 had one or more negative criteria (group AD). Patients with IMH and AD were similar with respect to sex, age, and delay between onset of symptoms and diagnostic and follow up imaging studies. Eighteen patients had a follow up imaging study after a mean period of 11.2 months: six in the IMH group and 12 in the AD group. Lesion volume decrease and relative true lumen volume increase were statistically significant in group IMH (p = .046 and p = .046, respectively), whereas there was a statistically significant increase of lesion volume (p = .008) in the AD group. CONCLUSION: This pilot study proposed three simple MRI criteria to differentiate between AD and IMH. Once prospectively and clinically validated, this could have substantial therapeutic benefits as IMH are likely to heal spontaneously.

Computed tomography angiography-fluoroscopy image fusion allows visceral vessel cannulation without angiography during fenestrated endovascular aneurysm repair.

BACKGROUND: Fenestrated endovascular aneurysm repair (FEVAR) is an evolving technique to treat juxtarenal abdominal aortic aneurysms (AAAs). Catheterization of visceral and renal vessels after the deployment of the fenestrated main body device is often challenging, usually requiring additional fluoroscopy and multiple digital subtraction angiograms. The aim of this study was to assess the clinical utility and accuracy of a computed tomography angiography (CTA)-fluoroscopy image fusion technique in guiding visceral vessel cannulation during FEVAR. METHODS: Between August 2014 and September 2016, all consecutive patients who underwent FEVAR at our institution using image fusion guidance were included. Preoperative CTA images were fused with intraoperative fluoroscopy after coregistering with non-contrast-enhanced cone beam computed tomography (syngo 3D3D image fusion; Siemens Healthcare, Forchheim, Germany). The ostia of the visceral vessels were electronically marked on CTA images (syngo iGuide Toolbox) and overlaid on live fluoroscopy to guide vessel cannulation after fenestrated device deployment. Clinical utility of image fusion was evaluated by assessing the number of dedicated angiograms required for each visceral or renal vessel cannulation and the use of optimized C-arm angulation. Accuracy of image fusion was evaluated from video recordings by three raters using a binary qualitative assessment scale. RESULTS: A total of 26 patients (17 men; mean age, 73.8 years) underwent FEVAR during the study period for juxtarenal AAA (17), pararenal AAA (6), and thoracoabdominal aortic aneurysm (3). Video recordings of fluoroscopy from 19 cases were available for review and assessment. A total of 46 vessels were cannulated; 38 of 46 (83%) of these vessels were cannulated without angiography but based only on image fusion guidance: 9 of 11 superior mesenteric artery cannulations and 29 of 35 renal artery cannulations. Binary qualitative assessment showed that 90% (36/40) of the virtual ostia overlaid on live fluoroscopy were accurate. Optimized C-arm angulations were achieved in 35% of vessel cannulations (0/9 for superior mesenteric artery cannulation, 12/25 for renal arteries). CONCLUSIONS: Preoperative CTA-fluoroscopy image fusion guidance during FEVAR is a valuable and accurate tool that allows visceral and renal vessel cannulation without the need of dedicated angiograms, thus avoiding additional injection of contrast material and radiation exposure. Further refinements, such as accounting for device-induced aortic deformation and automating the image fusion workflow, will bolster this technology toward optimal routine clinical use.

Electromagnetic tracking of flexible robotic catheters enables "assisted navigation" and brings automation to endovascular navigation in an in vitro study.

OBJECTIVE: Combining three-dimensional (3D) catheter control with electromagnetic (EM) tracking-based navigation significantly reduced fluoroscopy time and improved robotic catheter movement quality in a previous in vitro pilot study. The aim of this study was to expound on previous results and to expand the value of EM tracking with a novel feature, assistednavigation, allowing automatic catheter orientation and semiautomatic vessel cannulation. METHODS: Eighteen users navigated a robotic catheter in an aortic aneurysm phantom using an EM guidewire and a modified 9F robotic catheter with EM sensors at the tip of both leader and sheath. All users cannulated two targets, the left renal artery and posterior gate, using four visualization modes: (1) Standard fluoroscopy (control). (2) 2D biplane fluoroscopy showing real-time virtual catheter localization and orientation from EM tracking. (3) 2D biplane fluoroscopy with novel EM assisted navigation allowing the user to define the target vessel. The robotic catheter orients itself automatically toward the target; the user then only needs to advance the guidewire following this predefined optimized path to catheterize the vessel. Then, while advancing the catheter over the wire, the assisted navigation automatically modifies catheter bending and rotation in order to ensure smooth progression, avoiding loss of wire access. (4) Virtual 3D representation of the phantom showing real-time virtual catheter localization and orientation. Standard fluoroscopy was always available; cannulation and fluoroscopy times were noted for every mode and target cannulation. Quality of catheter movement was assessed by measuring the number of submovements of the catheter using the 3D coordinates of the EM sensors. A t-test was used to compare the standard fluoroscopy mode against EM tracking modes. RESULTS: EM tracking significantly reduced the mean fluoroscopy time (P < .001) and the number of submovements (P < .02) for both cannulation tasks. For the posterior gate, mean cannulation time was also significantly reduced when using EM tracking (P < .001). The use of novel EM assisted navigation feature (mode 3) showed further reduced cannulation time for the posterior gate (P = .002) and improved quality of catheter movement for the left renal artery cannulation (P = .021). CONCLUSIONS: These results confirmed the findings of a prior study that highlighted the value of combining 3D robotic catheter control and 3D navigation to improve safety and efficiency of endovascular procedures. The novel EM assisted navigation feature augments the robotic master/slave concept with automated catheter orientation toward the target and shows promising results in reducing procedure time and improving catheter motion quality.

Intraoperative cone beam computed tomography-guided endovascular recanalization of an interrupted aorta.

A 42-year-old man sustained a stroke secondary to malignant hypertension and was found to have complete aortic interruption. We report a case of real-time image-guided endovascular repair to highlight the value of preprocedural planning and intraprocedural cone beam computed tomography. Two-dimensional fluoroscopy enhanced with three-dimensional landmarks from cone beam computed tomography was used to direct a Nykanen radiofrequency wire (Baylis Medical, Montreal, Quebec, Canada) through the interruption, avoiding critical adjacent structures. A covered Cheatham-Platinum stent (NuMED, Inc, Hopkinton, NY) was deployed successfully, recanalizing the thoracic aorta. The pressure gradient normalized, and the patient was discharged on postoperative day 1. At 10-month follow-up, the patient was on an antihypertensive regimen of two minimum-dose drugs.

Feasibility of three-dimensional magnetic resonance angiography-fluoroscopy image fusion technique in guiding complex endovascular aortic procedures in patients with renal insufficiency.

OBJECTIVE: Three-dimensional image fusion of preoperative computed tomography (CT) angiography with fluoroscopy using intraoperative noncontrast cone-beam CT (CBCT) has been shown to improve endovascular procedures by reducing procedure length, radiation dose, and contrast media volume. However, patients with a contraindication to CT angiography (renal insufficiency, iodinated contrast allergy) may not benefit from this image fusion technique. The primary objective of this study was to evaluate the feasibility of magnetic resonance angiography (MRA) and fluoroscopy image fusion using noncontrast CBCT as a guidance tool during complex endovascular aortic procedures, especially in patients with renal insufficiency. METHODS: All endovascular aortic procedures done under MRA image fusion guidance at a single-center were retrospectively reviewed. The patients had moderate to severe renal insufficiency and underwent diagnostic contrast-enhanced magnetic resonance imaging after gadolinium or ferumoxytol injection. Relevant vascular landmarks electronically marked in MRA images were overlaid on real-time two-dimensional fluoroscopy for image guidance, after image fusion with noncontrast intraoperative CBCT. Technical success, time for image registration, procedure time, fluoroscopy time, number of digital subtraction angiography (DSA) acquisitions before stent deployment or vessel catheterization, and renal function before and after the procedure were recorded. The image fusion accuracy was qualitatively evaluated on a binary scale by three physicians after review of image data showing virtual landmarks from MRA on fluoroscopy. RESULTS: Between November 2012 and March 2016, 10 patients underwent endovascular procedures for aortoiliac aneurysmal disease or aortic dissection using MRA image fusion guidance. All procedures were technically successful. A paired t-test analysis showed no difference between preimaging and postoperative renal function (P = .6). The mean time required for MRA-CBCT image fusion was 4:09 ± 01:31 min:sec. Total fluoroscopy time was 20.1 ± 6.9 minutes. Five of 10 patients (50%) underwent stent graft deployment without any predeployment DSA acquisition. Three of six vessels (50%) were cannulated under image fusion guidance without any precannulation DSA runs, and the remaining vessels were cannulated after one planning DSA acquisition. Qualitative evaluation showed 14 of 22 virtual landmarks (63.6%) from MRA overlaid on fluoroscopy were completely accurate, without the need for adjustment. Five of eight incorrect virtual landmarks (iliac and visceral arteries) resulted from vessel deformation caused by endovascular devices. CONCLUSIONS: Ferumoxytol or gadolinium-enhanced MRA imaging and image fusion with fluoroscopy using noncontrast CBCT is feasible and allows patients with renal insufficiency to benefit from optimal guidance during complex endovascular aortic procedures, while preserving their residual renal function.

New predictors of complications in carotid body tumor resection.

OBJECTIVE: This study examined the relationship between two new variables, tumor distance to base of skull (DTBOS) and tumor volume, with complications of carotid body tumor (CBT) resection, including bleeding and cranial nerve injury. METHODS: Patients who underwent CBT resection between 2004 and 2014 were studied using a standardized, multi-institutional database. Demographic, perioperative, and outcomes data were collected. CBT measurements were determined from computed tomography, magnetic resonance imaging, and ultrasound examination. RESULTS: There were 356 CBTs resected in 332 patients (mean age, 51 years; 72% female); 32% were classified as Shamblin I, 43% as Shamblin II, and 23% as Shamblin III. The mean DTBOS was 3.3 cm (standard deviation [SD], 2.1; range, 0-10), and the mean tumor volume was 209.7 cm3 (SD, 266.7; range, 1.1-1642.0 cm3). The mean estimated blood loss (EBL) was 257 mL (SD, 426; range, 0-3500 mL). Twenty-four percent of patients had cranial nerve injuries. The most common cranial nerves injured were the hypoglossal (10%), vagus (11%), and superior laryngeal (5%) nerves. Both Shamblin grade and DTBOS were statistically significantly correlated with EBL of surgery and cranial nerve injuries, whereas tumor volume was statistically significantly correlated with EBL. The logistic model for predicting blood loss and cranial nerve injury with all three variables-Shamblin, DTBOS, and volume (R2 = 0.171, 0.221, respectively)-was superior to a model with Shamblin alone (R2 = 0.043, 0.091, respectively). After adjusting for Shamblin grade and volume, every 1-cm decrease in DTBOS was associated with 1.8 times increase in risk of >250 mL of blood loss (95% confidence interval, 1.25-2.55) and 1.5 times increased risk of cranial nerve injury (95% confidence interval, 1.19-1.92). CONCLUSIONS: This large study of CBTs demonstrates the value of preoperatively determining tumor dimensions and how far the tumor is located from the base of the skull. DTBOS and tumor volume, when used in combination with the Shamblin grade, better predict bleeding and cranial nerve injury risk. Furthermore, surgical resection before expansion toward the base of the skull reduces complications as every 1-cm decrease in the distance to the skull base results in 1.8 times increase in >250 mL of blood loss and 1.5 times increased risk of cranial nerve injury.

Randomized controlled trial comparing the safety and efficacy between the FUSION BIOLINE heparin-coated vascular graft and the standard expanded polytetrafluoroethylene graft for femoropopliteal bypass.

OBJECTIVE: Despite improvements in endovascular therapy for lower extremity arterial disease, open surgical revascularization is still required when the disease is extensive. Although autogenous vein is the conduit of choice for open femoropopliteal bypass, prosthetic grafts can be an acceptable alternative when adequate vein is not available. The FUSION BIOLINE heparin-coated vascular graft (Maquet Endovascular, Wayne, NJ) was developed to improve the patency rate associated with standard prosthetic grafts. The current study, the FINEST Trial (Comparison of Safety and Primary Patency Between the FUSION BIOLINE Heparin-Coated Vascular Graft and EXXCEL Soft ePTFE), was designed to assess the clinical outcome of heparin-coated and standard vascular grafts in a prospective, randomized, controlled, multicenter trial. METHODS: During a 25-month period ending in June 2012, 209 eligible patients scheduled to undergo elective prosthetic femoral to above-knee or below-knee popliteal bypass were randomized to receive a standard expanded polytetrafluoroethylene (ePTFE) graft or the heparin-coated FUSION BIOLINE vascular graft. Among 203 patients in the efficacy analysis, claudication was the presenting symptom in 147 (72.4%), and the site of the distal anastomosis was at the above-knee level in 174 (85.7%). Grafts were assessed by duplex ultrasound imaging and ankle-brachial indices performed postoperatively at discharge and at 30 days, 6 months, and 12 months. The primary efficacy end point was primary patency of the study graft. The primary safety end point was the composite of major adverse events and periprocedural death. Secondary end points included the time to hemostasis of bleeding at the anastomotic suture hole and primary assisted and secondary patency. RESULTS: The primary patency rates at 6 months were 86.4% for the FUSION BIOLINE heparin-coated vascular graft group compared with 70.0% for the standard ePTFE group, a difference of 16.4% (95% confidence interval, 2.7%-29.9%; P = .006), and the respective rates at 12 months were 76.5% and 67.0% (95% confidence interval, -4.8% to 23.0%; P = .05). The mean time to hemostasis of bleeding at the suture hole was 3.5 minutes in the FUSION BIOLINE group and 11.0 minutes in the standard ePTFE group (P < .0001). Major adverse events were significantly lower in the FUSION BIOLINE group, occurring in 17.1%, compared with 30.7% in the standard ePTFE group (P = .033), principally a result of a lower rate of major graft reinterventions through 12 months in the FUSION BIOLINE group (16.2% vs 30.7%). CONCLUSIONS: Data from this randomized multicenter study demonstrated improved midterm patency, less bleeding at the suture hole, and lower major adverse events with the FUSION BIOLINE heparin-coated vascular graft compared with standard ePTFE grafts. Although the ultimate long-term benefit of the graft cannot be ascertained with the data currently available, the utility of the FUSION BIOLINE vascular graft appears promising.

Kinematics effectively delineate accomplished users of endovascular robotics with a physical training model.

OBJECTIVE: Endovascular robotics systems, now approved for clinical use in the United States and Europe, are seeing rapid growth in interest. Determining who has sufficient expertise for safe and effective clinical use remains elusive. Our aim was to analyze performance on a robotic platform to determine what defines an expert user. METHODS: During three sessions, 21 subjects with a range of endovascular expertise and endovascular robotic experience (novices <2 hours to moderate-extensive experience with >20 hours) performed four tasks on a training model. All participants completed a 2-hour training session on the robot by a certified instructor. Completion times, global rating scores, and motion metrics were collected to assess performance. Electromagnetic tracking was used to capture and to analyze catheter tip motion. Motion analysis was based on derivations of speed and position including spectral arc length and total number of submovements (inversely proportional to proficiency of motion) and duration of submovements (directly proportional to proficiency). RESULTS: Ninety-eight percent of competent subjects successfully completed the tasks within the given time, whereas 91% of noncompetent subjects were successful. There was no significant difference in completion times between competent and noncompetent users except for the posterior branch (151 s:105 s; P = .01). The competent users had more efficient motion as evidenced by statistically significant differences in the metrics of motion analysis. Users with >20 hours of experience performed significantly better than those newer to the system, independent of prior endovascular experience. CONCLUSIONS: This study demonstrates that motion-based metrics can differentiate novice from trained users of flexible robotics systems for basic endovascular tasks. Efficiency of catheter movement, consistency of performance, and learning curves may help identify users who are sufficiently trained for safe clinical use of the system. This work will help identify the learning curve and specific movements that translate to expert robotic navigation.