Compliant vascular models 3D printed with the Stratasys J750: a direct characterization of model distensibility using intravascular ultrasound.

PURPOSE: The purpose of this study is to evaluate biomechanical accuracy of 3D printed anatomical vessels using a material jetting printer (J750, Stratasys, Rehovot, Israel) by measuring distensibility via intravascular ultrasound. MATERIALS AND METHODS: The test samples are 3D printed tubes to simulate arterial vessels (aorta, carotid artery, and coronary artery). Each vessel type is defined by design geometry of the vessel inner diameter and wall thickness. Vessel inner diameters are aorta = 30mm, carotid = 7mm, and coronary = 3mm. Vessel wall thickness are aorta = 3mm, carotid = 1.5mm, and coronary = 1mm. Each vessel type was printed in 3 different material options. Material options are user-selected from the J750 printer software graphical user interface as blood vessel wall anatomy elements in 'compliant', 'slightly compliant', and 'rigid' options. Three replicates of each vessel type were printed in each of the three selected material options, for a total of 27 models. The vessels were connected to a flow loop system where pressure was monitored via a pressure wire and cross-sectional area was measured with intravascular ultrasound (IVUS). Distensibility was calculated by comparing the % difference in cross-sectional area vs. pulse pressure to clinical literature values. Target clinical ranges for normal and diseased population distensibility are 10.3-44 % for the aorta, 5.1-10.1 % for carotid artery, and 0.5-6 % for coronary artery. RESULTS: Aorta test vessels had the most clinically representative distensibility when printed in user-selected 'compliant' and 'slightly compliant' material. All aorta test vessels of 'compliant' material (n = 3) and 2 of 3 'slightly compliant' vessels evaluated were within target range. Carotid vessels were most clinically represented in distensibility when printed in 'compliant' and 'slightly compliant' material. For carotid test vessels, 2 of 3 'compliant' material samples and 1 of 3 'slightly compliant' material samples were within target range. Coronary arteries were most clinically represented in distensibility when printed in 'slightly compliant' and 'rigid' material. For coronary test vessels, 1 of 3 'slightly compliant' materials and 3 of 3 'rigid' material samples fell within target range. CONCLUSIONS: This study suggests that advancements in materials and 3D printing technology introduced with the J750 Digital Anatomy 3D Printer can enable anatomical models with clinically relevant distensibility.

Semi-automated measurement of vascular tortuosity and its implications for mechanical thrombectomy performance.

PURPOSE: Few studies have examined the geometry of endovascular mechanical thrombectomy pathways. Here we examine the tortuosity and angulations of catheter pathways from the aortic arch to the termination of the internal carotid artery (ICA) and its association with thrombectomy performance. METHODS: We included 100 consecutive anterior circulation large vessel occlusion thrombectomy patients over 12 months. Computed tomography angiograms (CTA) were used for 3D segmentation of catheter pathway from the aortic arch to ICA termination. Tortuosity index (TI) and angulations of the catheter pathway were measured in a semi-automated fashion. TI and angulation degree were compared between sides and correlated with age and procedural measures. RESULTS: We analyzed 188 catheter pathways in 100 patients. Severe angulation (≤ 30°) was present in 5.8% and 39.4% of common carotid artery (CCA) and extracranial ICA segments, respectively. Five pathways (2.6%) had 360° loop. CCA and extracranial ICA tortuosity had a weak but significant correlation with age (r = 0.17, 0.21, p value = 0.05, 0.02 respectively), time from groin puncture to the site of occlusion (r = 0.29, 0.25, p values = 0.008, 0.026 respectively), and fluoroscopy time (r = 0.022, 0.31, p values = 0.016, 0.001 respectively). There was a significant difference in the pattern of angulation (p value = 0.04) and tortuosity between right and left side in CCA segment (TI = 0.20 ± 0.086 vs. 0.15 ± 0.82, p value < 0.001). CONCLUSIONS: There was a significant difference in CCA angulation between right and left sides. TI of extracranial CCA and ICA correlated with age and influenced time from groin puncture to the occlusion site and total fluoroscopy time.

Design and Physical Properties of 3-Dimensional Printed Models Used for Neurointervention: A Systematic Review of the Literature.

BACKGROUND: Three-dimensional (3D) printing has revolutionized training, education, and device testing. Understanding the design and physical properties of 3D-printed models is important. OBJECTIVE: To systematically review the design, physical properties, accuracy, and experimental outcomes of 3D-printed vascular models used in neurointervention. METHODS: We conducted a systematic review of the literature between January 1, 2000 and September 30, 2018. Public/Publisher MEDLINE (PubMed), Web of Science, Compendex, Cochrane, and Inspec databases were searched using Medical Subject Heading terms for design and physical attributes of 3D-printed models for neurointervention. Information on design and physical properties like compliance, lubricity, flow system, accuracy, and outcome measures were collected. RESULTS: A total of 23 articles were included. Nine studies described 3D-printed models for stroke intervention. Tango Plus (Stratasys) was the most common material used to develop these models. Four studies described a population-representative geometry model. All other studies reported patient-specific vascular geometry. Eight studies reported complete reconstruction of the circle of Willis, anterior, and posterior circulation. Four studies reported a model with extracranial vasculature. One prototype study reported compliance and lubricity. Reported circulation systems included manual flushing, programmable pistons, peristaltic, and pulsatile pumps. Outcomes included thrombolysis in cerebral infarction, post-thrombectomy flow restoration, surgical performance, and qualitative feedback. CONCLUSION: Variations exist in the material, design, and extent of reconstruction of vasculature of 3D-printed models. There is a need for objective characterization of 3D-printed vascular models. We propose the development of population representative 3D-printed models for skill improvement or device testing.

Safety analysis of a hemostatic powder in a porcine model of acute severe gastric bleeding.

BACKGROUND: Non-variceal upper gastrointestinal (UGI) bleeding is a common condition that requires prompt lifesaving therapy and traditional endoscopic treatments require high technical proficiency to perform. AIMS: This study was conducted to identify any local or systemic histopathologic effects of a hemostatic powder in a porcine model of active, severe, non-variceal UGI hemorrhage. METHODS: This prospective, non-blinded animal study was performed in accordance with Good Laboratory Practice and Animal Care and Use Guidelines. Six animals underwent gastrotomy and creation of a looped vascular bundle, which was placed into the stomach lumen. The transplanted vascular bundle was punctured with an endoscopic needle-knife to create Forrest grade Ia or Ib bleeding. The hemostatic powder was then applied until hemostasis was achieved. RESULTS: Initial hemostasis was achieved in all animals. Results of pre- and post-treatment coagulation studies were similar. All animals survived at least 9 days post-procedure. The hemostatic powder was not found in any local, regional, or systemic tissues. Gross and histologic analysis of systemic organs showed no infarct, particulate, or embolic effects. No gross or microscopic necropsy findings were treatment-related. CONCLUSIONS: The hemostatic powder achieved initial hemostasis (even in animals with spurting arterial bleeding) with no bowel obstruction or unintended luminal effects, no local or regional particulate effects, no systemic embolic effects, and no systemic coagulopathic effects.

Stent placement provides safe esophageal closure in thoracic NOTES(TM) procedures.

BACKGROUND: Safe esophageal closure remains a challenge in transesophageal Natural Orifice Transluminal Endoscopic Surgery (NOTES). Previously described methods, such as suturing devices, clips, or submucosal tunneling, all have weaknesses. In this survival animal series, we demonstrate safe esophageal closure with a prototype retrievable, antimigration stent. METHODS: Nine Yorkshire swine underwent thoracic NOTES procedures. A double-channel gastroscope equipped with a mucosectomy device was used to create an esophageal mucosal defect. A 5-cm submucosal tunnel was created and the muscular esophageal wall was incised with a needle-knife. Mediastinoscopy and thoracoscopy were performed in all swine; lymphadenectomy was performed in seven swine. A prototype small intestinal submucosal (SurgiSIS(®)) covered stent was deployed over the mucosectomy site and tunnel. Three versions of the prototype stent were developed. Prenecropsy endoscopy confirmed stent location and permitted stent retrieval. Explanted esophagi were sent to pathology. RESULTS: Esophageal stenting was successful in all animals. Stent placement took 15.8 ± 4.8 minuted and no stent migration occurred. Prenecropsy endoscopy revealed proximal ingrowth of esophageal mucosa and erosion with Stent A. Mucosal inflammation and erosion was observed proximally with Stent B. No esophageal erosion or pressure damage from proximal radial forces was seen with Stent C. On necropsy, swine 5 had a 0.5-cm periesophageal abscess. Histology revealed a localized inflammatory lesion at the esophageal exit site in swine 1, 3, and 9. The mucosectomy site was partially healed in three swine and poorly healed in six. All swine thrived clinically, except for a brief period of mild lethargy in swine 9 who improved with short-term antibiotic therapy. The submucosal tunnels were completely healed and no esophageal bleeding or stricture formation was observed. All swine survived 13.8 ± 0.4 days and gained weight in the postoperative period. CONCLUSIONS: Esophageal stenting provides safe closure for NOTES thoracic procedures but may impede healing of the mucosectomy site.

A new alternative for a transjugular intrahepatic portosystemic shunt: EUS-guided creation of an intrahepatic portosystemic shunt (with video).

BACKGROUND: Transjugular intrahepatic portosystemic shunt (TIPSS) is an effective treatment for portal hypertension and its associated complications. EUS-guided creation of an intrahepatic portosystemic shunt (IPSS) may become a useful alternative to conventional TIPSS. OBJECTIVE: To assess the feasibility of EUS-guided IPSS creation in a live porcine model. SETTING: Acute and survival experiments in 50-kg pigs. DESIGN AND INTERVENTIONS: Under linear-array EUS guidance, the hepatic vein (HV) and then the portal vein (PV) were punctured with a 19-gauge FNA needle. A 0.035-inch guidewire was advanced through the needle into the PV lumen. The needle was exchanged over the wire, a metal stent was deployed under EUS and fluoroscopic guidance, and the distal end of the stent was positioned inside the PV and the proximal end within the HV. Eight animals were euthanized after the procedure, and 2 animals were kept alive for 2 weeks. MAIN OUTCOME MEASUREMENTS: Successful EUS-guided IPSS creation. RESULTS: Portosystemic shunt placement was successful in all animals. Intrahepatic vascular puncture and stent deployment were technically easy. Portosystemic flow through the shunt was documented by portal venogram and EUS Doppler. Necropsy performed after acute and survival experiments revealed no evidence of bleeding or damage to any intraperitoneal organs. There were no complications during the follow-up period in the 2 animals that were kept alive. LIMITATION: Experiments were performed in healthy animals with normal PV pressure. CONCLUSION: EUS-guided IPSS creation is technically feasible and may become an alternative to the currently used method of TIPSS placement.