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Takada J, Hamada K, Zhu X, Tsuboko Y, Iwasaki K. Biaxial tensile testing system for measuring mechanical properties of both sides of biological tissues. J Mech Behav Biomed Mater 2023; 146:106028. [PMID: 37531771 DOI: 10.1016/j.jmbbm.2023.106028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 07/11/2023] [Accepted: 07/14/2023] [Indexed: 08/04/2023]
Abstract
The aortic wall exhibits a unique elastic behavior, periodically expanding in aortic diameter by approximately 10% during heartbeats. This elastic behavior of the aortic wall relies on the distinct yet interacting mechanical properties of its three layers: intima, media, and adventitia. Aortic aneurysms develop as a result of multifactorial remodeling influenced by mechanical vulnerability of the aortic wall. Therefore, investigating the mechanical response of the aneurysmal wall, in conjunction with changes in microstructural parameters on both the intimal and adventitial sides, may offer valuable insights into the mechanisms of aortic aneurysm development or rupture. This study aimed to develop a biaxial tensile testing system to measure the mechanical properties of both sides of the tissue to gain insights concerning the interactions in anisotropic layered tissue. The biaxial tensile test set-up consisted of four motors, four cameras, four load cells, and a toggle switch. Porcine ascending aortas were chosen as the test subject. Graphite particles with diameters of approximately 5-11 [μm] were randomly applied to both sides of the aorta. Strain measurements were obtained using the stereo digital-image correlation method. Because stretching a rectangular specimen with a thread inevitably concentrates and localizes stress, to reduce this effect the specimen's shape was investigated using finite element analysis. The finite element analysis showed that a cross-shaped specimen with diagonally cut edges would be suitable. Therefore, we prepared specimens with this novel shape. This test system showed that mechanical response of the aortic tissue was significantly different between the intimal and adventitial side in the high-strain range, due to the disruption of collagen fibers. The adventitia side exhibited a smaller elastic modulus than the intimal side, accompanied by disruption of collagen fibers in the adventitia, which were more pronounced in the longitudinal direction. In contrast, in the mid-strain range, the elastic modulus did not differ between the intimal and adventitial sides, irrespective of longitudinal or circumferential direction, and collagen fibers were not disrupted but elongated. A biaxial tensile test system, which measures the mechanical properties of both sides of biological tissues and the shape of the specimen for reducing the concentration of stress at the chuck region, was developed in this study. The biaxial tensile testing system developed here is useful for better understanding the influences of mechanical loads and tissue degeneration on anisotropic, layered biological tissues.
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Affiliation(s)
- Jumpei Takada
- Department of Modern Mechanical Engineering, School of Creative Science and Engineering, Waseda University, Tokyo, Japan; Department of Integrative Bioscience and Biomedical Engineering, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Kohei Hamada
- Department of Integrative Bioscience and Biomedical Engineering, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Xiaodong Zhu
- Waseda Research Institute for Science and Engineering, Waseda University, Tokyo, Japan
| | - Yusuke Tsuboko
- Waseda Research Institute for Science and Engineering, Waseda University, Tokyo, Japan
| | - Kiyotaka Iwasaki
- Department of Modern Mechanical Engineering, School of Creative Science and Engineering, Waseda University, Tokyo, Japan; Department of Integrative Bioscience and Biomedical Engineering, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan; Waseda Research Institute for Science and Engineering, Waseda University, Tokyo, Japan; Cooperative Major in Advanced Biomedical Sciences, Joint Graduate School of Tokyo Women's Medical University and Waseda University, Waseda University, Tokyo, Japan.
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Sabotin RP, Varon A, Roa JA, Raghuram A, Ishii D, Nino M, Galloy AE, Patel D, Raghavan ML, Hasan D, Samaniego EA. Insights into the pathogenesis of cerebral fusiform aneurysms: high-resolution MRI and computational analysis. J Neurointerv Surg 2021; 13:1180-1186. [PMID: 33632878 DOI: 10.1136/neurintsurg-2020-017243] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/26/2021] [Accepted: 01/29/2021] [Indexed: 11/04/2022]
Abstract
BACKGROUND Intracranial fusiform aneurysms are complex and poorly characterized vascular lesions. High-resolution magnetic resonance imaging (HR-MRI) and computational morphological analysis may be used to characterize cerebral fusiform aneurysms. OBJECTIVE To use advanced imaging and computational analysis to understand the unique pathophysiology, and determine possible underlying mechanisms of instability of cerebral fusiform aneurysms. METHODS Patients with unruptured intracranial aneurysms prospectively underwent imaging with 3T HR-MRI at diagnosis. Aneurysmal wall enhancement was objectively quantified using signal intensity after normalization of the contrast ratio (CR) with the pituitary stalk. Enhancement between saccular and fusiform aneurysms was compared, as well as enhancement characteristics of fusiform aneurysms. The presence of microhemorrhages in fusiform aneurysms was determined with quantitative susceptibility mapping (QSM). Three distinct types of fusiform aneurysms were analyzed with computational fluid dynamics (CFD) and finite element analysis (FEA). RESULTS A total of 130 patients with 160 aneurysms underwent HR-MRI. 136 aneurysms were saccular and 24 were fusiform. Fusiform aneurysms had a significantly higher CR and diameter than saccular aneurysms. Enhancing fusiform aneurysms exhibited more enhancement of reference vessels than non-enhancing fusiform aneurysms. Ten fusiform aneurysms underwent QSM analysis, and five aneurysms showed microhemorrhages. Microhemorrhage-positive aneurysms had a larger volume, diameter, and greater enhancement than aneurysms without microhemorrhage. Three types of fusiform aneurysms exhibited different CFD and FEA patterns. CONCLUSION Fusiform aneurysms exhibited more contrast enhancement than saccular aneurysms. Enhancing fusiform aneurysms had larger volume and diameter, more enhancement of reference vessels, and more often exhibited microhemorrhage than non-enhancing aneurysms. CFD and FEA suggest that various pathophysiological processes determine the formation and growth of fusiform aneurysms.
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Affiliation(s)
- Ryan Phillip Sabotin
- Department of Neurology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Alberto Varon
- Department of Neurology, The University of Iowa, Iowa City, Iowa, USA
| | - Jorge A Roa
- Department of Neurology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Ashrita Raghuram
- Department of Neurology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Daizo Ishii
- Department of Neurosurgery, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Marco Nino
- Roy J Carver Department of Biomedical Engineering, The University of Iowa, Iowa City, Iowa, USA
| | - Adam E Galloy
- Roy J Carver Department of Biomedical Engineering, The University of Iowa, Iowa City, Iowa, USA
| | - Devanshee Patel
- Department of Neurology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Madhavan L Raghavan
- Roy J Carver Department of Biomedical Engineering, The University of Iowa, Iowa City, Iowa, USA
| | - David Hasan
- Department of Neurosurgery, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Edgar A Samaniego
- Department of Neurology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA .,Department of Neurosurgery, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.,Department of Radiology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
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