Publications by authors named "Yihao Zheng"

12 Publications

  • Page 1 of 1

Failure modes and effects analysis of mechanical thrombectomy for stroke discovered in human brains.

J Neurosurg 2021 Jun 4:1-8. Epub 2021 Jun 4.

3Neurosurgery, University of Michigan, Ann Arbor, Michigan.

Objective: Despite advancement of thrombectomy technologies for large-vessel occlusion (LVO) stroke and increased user experience, complete recanalization rates linger around 50%, and one-third of patients who have undergone successful recanalization still experience poor neurological outcomes. To enhance the understanding of the biomechanics and failure modes, the authors conducted an experimental analysis of the interaction of emboli/artery/devices in the first human brain test platform for LVO stroke described to date.

Methods: In 12 fresh human brains, 105 LVOs were recreated by embolizing engineered emboli analogs and recanalization was attempted using aspiration catheters and/or stent retrievers. The complex mechanical interaction between diverse emboli (elastic, stiff, and fragment prone), arteries (anterior and posterior circulation), and thrombectomy devices were observed, analyzed, and categorized. The authors systematically evaluated the recanalization process through failure modes and effects analysis, and they identified where and how thrombectomy devices fail and the impact of device failure.

Results: The first-pass effect (34%), successful (71%), and complete (60%) recanalization rates in this model were consistent with those in the literature. Failure mode analysis of 184 passes with thrombectomy devices revealed the following. 1) Devices loaded the emboli with tensile forces leading to elongation and intravascular fragmentation. 2) In the presence of anterograde flow, small fragments embolize to the microcirculation and large fragments result in recurrent vessel occlusion. 3) Multiple passes are required due to recurrent (15%) and residual (73%) occlusions, or both (12%). 4) Residual emboli remained in small branching and perforating arteries in cases of alleged complete recanalization (28%). 5) Vacuum caused arterial collapse at physiological pressures (27%). 6) Device withdrawal caused arterial traction (41%), and severe traction provoked avulsion of perforating and small branching arteries.

Conclusions: Biomechanically superior thrombectomy technologies should prevent unrestrained tensional load on emboli, minimize intraluminal embolus fragmentation and release, improve device/embolus integration, recanalize small branching and perforating arteries, prevent arterial collapse, and minimize traction.
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http://dx.doi.org/10.3171/2020.11.JNS203684DOI Listing
June 2021

Detecting High-Resolution Intramural Vascular Wall Strain Signals Using DICOM Data.

ASAIO J 2021 May 28. Epub 2021 May 28.

From the Research Service, VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan Department of Statistics, University of Michigan, Ann Arbor, Michigan Michigan Tech Research Institute, Michigan Technological University, Ann Arbor, Michigan Department of Psychiatry, University of Michigan, Ann Arbor, Michigan Radiology, Weill Cornell Medicine, New York City, New York Radiology, Rocky Vista University, Ivins, Utah Emerge Now Inc., Los Angeles, California Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts Departments of Radiology and Surgery, University of Michigan, Ann Arbor, Michigan.

Maintaining dialysis vascular access is a source of considerable morbidity in patients with end-stage renal disease (ESRD). High-resolution radiofrequency (RF) ultrasound vascular strain imaging has been applied experimentally in the vascular access setting to assist in diagnosis and management. Unfortunately, high-resolution RF data are not routinely accessible to clinicians. In contrast, the standard DICOM formatted B-mode ultrasound data are widely accessible. However, B-mode, representing the envelope of the RF signal, is of much lower resolution. If strain imaging could use open-source B-mode data, these imaging techniques could be more broadly investigated. We conducted experiments to detect wall strain signals with submillimeter tracking resolutions ranging from 0.2 mm (3 pixels) to 0.65 mm (10 pixels) using DICOM B-mode data. We compared this submillimeter tracking to the overall vascular distensibility as the reference measurements to see if high-strain resolution strain could be detected using open-source B-Mode data. We measured the best-fit coefficient of determination between signals, expressed as the percentage of strain waveforms that exhibited a correlation with a p value of 0.05 or less. The lowest percentage was 86.7%, and most were 90% and higher. This indicates high-resolution strain signals can be detected within the vessel wall using B-mode DICOM data.
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http://dx.doi.org/10.1097/MAT.0000000000001490DOI Listing
May 2021

Sono-angiography for dialysis vascular access based on the freehand 2D ultrasound scanning.

J Vasc Access 2021 May 10:11297298211015066. Epub 2021 May 10.

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.

Introduction: Dialysis vascular access, preferably an autogenous arteriovenous fistula, remains an end stage renal disease (ESRD) patient's lifeline providing a means of connecting the patient to the dialysis machine. Once an access is created, the current gold standard of care for maintenance of vascular access is angiography and angioplasty to treat stenosis. While point of care 2D ultrasound has been used to detect access problems, we sought to reproduce angiographic results comparable to the gold standard angiogram (fistulogram) using ultrasound data acquired from a conventional 2D ultrasound scanner.

Methods: A 2D ultrasound probe was used to acquire a series of cross sectional images of the vascular access including arteriovenous anastomosis of a subject with a radio-cephalic fistula. These 2D B-mode images were used for 3D vessel reconstruction by binary thresholding to categorize vascular versus non-vascular structures followed by standard image segmentation to select the structure representative of dialysis vascular access and morphologic filtering. Image processing was done using open source Python Software.

Results: The open source software was able to: (1) view the gold standard fistulogram images, (2) reconstruct 2D planar images of the fistula from ultrasound data as viewed from the top, analogous to computerized tomography images, and (3) construct a 2D representation of vascular access similar to the angiogram.

Conclusion: We present a simple approach to obtain an angiogram-like representation of the vascular access from readily available, non-proprietary 2D ultrasound data in the point of care setting. While the sono-angiogram is not intended to replace angiography, it may be useful in providing 3D imaging at the point of care in the dialysis unit, outpatient clinic, or for pre-operative planning for interventional procedures. Future work will focus on improving the robustness and quality of the imaging data while preserving the straightforward freehand approach used for ultrasound data acquisition.
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http://dx.doi.org/10.1177/11297298211015066DOI Listing
May 2021

A human brain test bed for research in large vessel occlusion stroke.

J Neurosurg 2021 Jan 22:1-9. Epub 2021 Jan 22.

1Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.

Objective: Endovascular removal of emboli causing large vessel occlusion (LVO)-related stroke utilizing suction catheter and/or stent retriever technologies or thrombectomy is a new standard of care. Despite high recanalization rates, 40% of stroke patients still experience poor neurological outcomes as many cases cannot be fully reopened after the first attempt. The development of new endovascular technologies and techniques for mechanical thrombectomy requires more sophisticated testing platforms that overcome the limitations of phantom-based simulators. The authors investigated the use of a hybrid platform for LVO stroke constructed with cadaveric human brains.

Methods: A test bed for embolic occlusion of cerebrovascular arteries and mechanical thrombectomy was developed with cadaveric human brains, a customized hydraulic system to generate physiological flow rate and pressure, and three types of embolus analogs (elastic, stiff, and fragment-prone) engineered to match mechanically and phenotypically the emboli causing LVO strokes. LVO cases were replicated in the anterior and posterior circulation, and thrombectomy was attempted using suction catheters and/or stent retrievers.

Results: The test bed allowed radiation-free visualization of thrombectomy for LVO stroke in real cerebrovascular anatomy and flow conditions by transmural visualization of the intraluminal elements and procedures. The authors were able to successfully replicate 105 LVO cases with 184 passes in 12 brains (51 LVO cases and 82 passes in the anterior circulation, and 54 LVO cases and 102 passes in the posterior circulation). Observed recanalization rates in this model were graded using a Recanalization in LVO (RELVO) scale analogous to other measures of recanalization outcomes in clinical use.

Conclusions: The human brain platform introduced and validated here enables the analysis of artery-embolus-device interaction under physiological hemodynamic conditions within the unmodified complexity of the cerebral vasculature inside the human brain.
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http://dx.doi.org/10.3171/2020.7.JNS202278DOI Listing
January 2021

Standardized Fabrication Method of Human-Derived Emboli with Histologic and Mechanical Quantification for Stroke Research.

J Stroke Cerebrovasc Dis 2020 Nov 7;29(11):105205. Epub 2020 Aug 7.

Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan, USA; Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota, USA. Electronic address:

Background: As access to patient emboli is limited, embolus analogs (EAs) have become critical to the research of large vessel occlusion (LVO) stroke and the development of thrombectomy technology. To date, techniques for fabricating standardized human blood-derived EAs are limited in the variety of compositions, and the mechanical properties relevant to thrombectomy are not quantified.

Methods: EAs were made by mixing human banked red blood cells (RBCs), plasma, and platelet concentrate in 10 different volumetric percentage combinations to mimic the broad range of patient emboli causing LVO strokes. The samples underwent histologic analysis and tensile testing to mimic the pulling action of thrombectomy devices, and were compared to patient emboli.

Results: EAs had histologic compositions of 0-96% RBCs, 0.78%-92% fibrin, and 2.1%-22% platelets, which can be correlated with the ingredients using a regression model. At fracture, EAs elongated from 81% to 136%, and the ultimate tensile stress ranged from 16 to 949 kPa. These EAs' histologic compositions and tensile properties showed great similarity to those of emboli retrieved from LVO stroke patients, indicating the validity of such EA fabrication methods. EAs with lower RBC and higher fibrin contents are more extensible and can withstand higher tensile stress.

Conclusions: EAs fabricated and tested using the proposed new methods provide a platform for stroke research and pre-clinical development of thrombectomy devices.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2020.105205DOI Listing
November 2020

Ultrasound speckle tracking to detect vascular distensibility changes from angioplasty and branch ligation in a radio-cephalic fistula: Use of novel open source software.

J Vasc Access 2020 Sep 26:1129729820959910. Epub 2020 Sep 26.

VA Ann Arbor Healthcare System, Ann Arbor, MI, USA.

We used novel open source software, based on an ultrasound speckle tracking algorithm, to examine the distensibility of the vessel wall of the inflow artery, anastomosis, and outflow vein before and after two procedures. An 83-year-old white man with a poorly maturing radio-cephalic fistula received an angioplasty at the anastomosis followed by branch ligation 28 days later. Duplex Doppler measurements corroborated the blood flow related changes anticipated from the interventions. The experimental distensibility results showed that it is technically feasible to measure subtle vessel wall motion changes with high resolution (sub-millimeter) using standard Digital Imaging and Communications in Medicine (DICOM) ultrasound data, which are readily available on conventional ultrasound scanners. While this methodology was originally developed using high resolution radiofrequency from ultrasound data, the goal of this study was to use DICOM data, which makes this technology accessible to a wide range of users.
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http://dx.doi.org/10.1177/1129729820959910DOI Listing
September 2020

Construction of a comprehensive endovascular test bed for research and device development in mechanical thrombectomy in stroke.

J Neurosurg 2020 Apr 3;134(3):1190-1197. Epub 2020 Apr 3.

Departments of1Neurosurgery and.

Objective: The development of new endovascular technologies and techniques for mechanical thrombectomy in stroke has greatly relied on benchtop simulators. This paper presents an affordable, versatile, and realistic benchtop simulation model for stroke.

Methods: A test bed for embolic occlusion of cerebrovascular arteries and mechanical thrombectomy was developed with 3D-printed and commercially available cerebrovascular phantoms, a customized hydraulic system to generate physiological flow rate and pressure, and 2 types of embolus analogs (elastic and fragment-prone) capable of causing embolic occlusions under physiological flow.

Results: The test bed was highly versatile and allowed realistic, radiation-free mechanical thrombectomy for stroke due to large-vessel occlusion with rapid exchange of geometries and phantom types. Of the transparent cerebrovascular phantoms tested, the 3D-printed phantom was the easiest to manufacture, the glass model offered the best visibility of the interaction between embolus and thrombectomy device, and the flexible model most accurately mimicked the endovascular system during device navigation. None of the phantoms modeled branches smaller than 1 mm or perforating arteries, and none underwent realistic deformation or luminal collapse from device manipulation or vacuum. The hydraulic system created physiological flow rate and pressure leading to iatrogenic embolization during thrombectomy in all phantoms. Embolus analogs with known fabrication technique, structure, and tensile strength were introduced and consistently occluded the middle cerebral artery bifurcation under physiological flow, and their interaction with the device was accurately visualized.

Conclusions: The test bed presented in this study is a low-cost, comprehensive, realistic, and versatile platform that enabled high-quality analysis of embolus-device interaction in multiple cerebrovascular phantoms and embolus analogs.
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http://dx.doi.org/10.3171/2020.1.JNS192732DOI Listing
April 2020

Analysis of human emboli and thrombectomy forces in large-vessel occlusion stroke.

J Neurosurg 2020 Feb 28;134(3):893-901. Epub 2020 Feb 28.

Departments of3Neurosurgery and.

Objective: This study's purpose was to improve understanding of the forces driving the complex mechanical interaction between embolic material and current stroke thrombectomy devices by analyzing the histological composition and strength of emboli retrieved from patients and by evaluating the mechanical forces necessary for retrieval of such emboli in a middle cerebral artery (MCA) bifurcation model.

Methods: Embolus analogs (EAs) were generated and embolized under physiological pressure and flow conditions in a glass tube model of the MCA. The forces involved in EA removal using conventional endovascular techniques were described, analyzed, and categorized. Then, 16 embolic specimens were retrieved from 11 stroke patients with large-vessel occlusions, and the tensile strength and response to stress were measured with a quasi-static uniaxial tensile test using a custom-made platform. Embolus compositions were analyzed and quantified by histology.

Results: Uniaxial tension on the EAs led to deformation, elongation, thinning, fracture, and embolization. Uniaxial tensile testing of patients' emboli revealed similar soft-material behavior, including elongation under tension and differential fracture patterns. At the final fracture of the embolus (or dissociation), the amount of elongation, quantified as strain, ranged from 1.05 to 4.89 (2.41 ± 1.04 [mean ± SD]) and the embolus-generated force, quantified as stress, ranged from 63 to 2396 kPa (569 ± 695 kPa). The ultimate tensile strain of the emboli increased with a higher platelet percentage, and the ultimate tensile stress increased with a higher fibrin percentage and decreased with a higher red blood cell percentage.

Conclusions: Current thrombectomy devices remove emboli mostly by applying linear tensile forces, under which emboli elongate until dissociation. Embolus resistance to dissociation is determined by embolus strength, which significantly correlates with composition and varies within and among patients and within the same thrombus. The dynamic intravascular weakening of emboli during removal may lead to iatrogenic embolization.
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http://dx.doi.org/10.3171/2019.12.JNS192187DOI Listing
February 2020

Catheter thermal energy generation and temperature in rotational atherectomy.

Med Eng Phys 2019 08 4;70:29-38. Epub 2019 Jul 4.

Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA.

This research studies the catheter friction thermal energy generation and saline temperature in rotational atherectomy (RA). RA is a catheter-based procedure utilizing a high-speed (typically 130,000 to 210,000 rpm) miniature grinding wheel to remove hardened calcified plaque inside the artery to restore the blood flow. During RA, elevated temperature due to the friction within the catheter may lead to complications such as slow-flow/no-reflow and myocardial infarction. RA experiments were conducted to measure the catheter temperature. An advection-diffusion model with inverse heat transfer solution was developed to estimate the spatial and temporal distributions of saline temperature and study effects of the rotational speed, catheter insertion length, and flow rates of blood-mimicking water and saline. The saline temperature rise is higher with higher wheel rotational speed, shorter insertion length, and lower flow rates of blood-mimicking water and saline. The wheel rotational speed and blood flow rate are the two most significant parameters affecting the saline and blood-mimicking water mixture temperature, which exhibits the highest (9 °C) rise under the 175,000 rpm wheel rotational speed and no blood-mimicking water flow (totally occluded artery) condition. This research provides insights and guidelines on RA device and clinical procedure from the thermal perspective.
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http://dx.doi.org/10.1016/j.medengphy.2019.06.014DOI Listing
August 2019

3D Printed composite for simulating thermal and mechanical responses of the cortical bone in orthopaedic surgery.

Med Eng Phys 2018 11 1;61:61-68. Epub 2018 Sep 1.

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, United States.

Synthetic bones made of polyurethane (PU) foams or glass-fiber reinforced epoxy are often used in surgical training, planning, and tool analysis, but these materials cannot be 3D printed for a patient-specific design. This paper introduces a new type of bone-mimicking material made by the binder jetting technology and a post-strengthening process with epoxy, namely 3D polymer-infiltrated composite (3DPIC). 3DPIC has been previously evaluated by surgeons as a proper alternative to commercial synthetic bones, but no quantitative testing data is available. Therefore, a series of experiments are conducted in this study to verify the use of 3DPIC. The first part of experiments includes the measurement of mechanical properties using the four-point bending and the measurement of thermal properties. The second part of experiments is to test drilling haptic and thermal responses of 3DPIC as compared to the cortical bone. The results show that 3DPIC has a comparable elastic modulus but a lower strength than the cortical bone. 3DPIC can produce realistic drilling force and torque as well as representative temperature change in drilling operations, but the bone debris tends to be more ductile and continuous than that of the cortical bone. Applications and limitations of 3DPIC are discussed based on these results.
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http://dx.doi.org/10.1016/j.medengphy.2018.08.004DOI Listing
November 2018

Computational Fluid Dynamics Modeling of the Burr Orbital Motion in Rotational Atherectomy with Particle Image Velocimetry Validation.

Ann Biomed Eng 2018 Apr 24;46(4):567-578. Epub 2018 Jan 24.

Department of Mechanical Engineering, University of Michigan, 2350 Hayward, Ann Arbor, MI, 48109, USA.

Rotational atherectomy (RA) uses a high-speed rotating burr introduced via a catheter through the artery to remove hardened atherosclerotic plaque. Current clinical RA technique lacks consensus on burr size and rotational speed. The rotating burr orbits inside the artery due to the fluid force of the blood. Different from a common RA technique of upsizing burrs for larger luminal gain, a small burr can orbit to treat a large lumen. A 3D computational fluid dynamics (CFD) model was developed to simulate the burr motion and study the fluid flow and force in RA. A particle image velocimetry experiment was conducted to measure and validate the flow field including the radial and axial velocities and a pair of counter-rotating vortices near the burr equator in CFD. The hydraulic force on the burr and the contact force between the burr and the arterial wall were estimated by CFD. The contact force can be reduced by using smaller burr and lower rotational speed. Utilizing the small burr orbital motion has the potential to be an improved RA technique.
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http://dx.doi.org/10.1007/s10439-018-1984-zDOI Listing
April 2018

Experimental investigation of the abrasive crown dynamics in orbital atherectomy.

Med Eng Phys 2016 07 6;38(7):639-647. Epub 2016 May 6.

Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA. Electronic address:

Orbital atherectomy is a catheter-based minimally invasive procedure to modify the plaque within atherosclerotic arteries using a diamond abrasive crown. This study was designed to investigate the crown motion and its corresponding contact force with the vessel. To this end, a transparent arterial tissue-mimicking phantom made of polyvinyl chloride was developed, a high-speed camera and image processing technique were utilized to visualize and quantitatively analyze the crown motion in the vessel phantom, and a piezoelectric dynamometer measured the forces on the phantom during the procedure. Observed under typical orbital atherectomy rotational speeds of 60,000, 90,000, and 120,000rpm in a 4.8mm caliber vessel phantom, the crown motion was a combination of high-frequency rotation at 1000, 1500, and 1660.4-1866.1Hz and low-frequency orbiting at 18, 38, and 40Hz, respectively. The measured forces were also composed of these high and low frequencies, matching well with the rotation of the eccentric crown and the associated orbital motion. The average peak force ranged from 0.1 to 0.4N at different rotational speeds.
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http://dx.doi.org/10.1016/j.medengphy.2016.04.006DOI Listing
July 2016
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