Author(s)

Fumio Nogata^1*, Yasunari Yokota², Yoko Kawamura³, Hiroyuki Morita⁴, Yoshiyuki Uno⁵, Tetsuya Mouri⁶, William R. Walsh⁷, Takakahiko Kawamura⁸, Nigishi Hotta⁹, Kenji Kagechika¹⁰

¹Gifu University, Gifu, Japan.
²Department of Electrical, Electronic and Computer Engineering, Faculty of Engineering, Gifu University, Gifu, Japan.
³Faculty of Engineering, Gifu University, Gifu, Japan.
⁴Department of General Medicine and General Internal Medicine, Gifu University Graduate School of Medicine, Gifu, Japan.
⁵Department of General Medicine, Gifu Prefectural General Medical Center, Gifu, Japan.
⁶Department of Mechanical Engineering, Faculty of Engineering, Gifu University, Gifu, Japan.
⁷Prince of Wales Hospital, University of New South Wales, Kensington, Australia.
⁸Chubu Rosai Hospital, Aichi, Japan Diabetes and Endocrine Internal Medicine, Nagoya, Japan.
⁹Nagoya University and Chubu Rosai Hospital, Internal Medicine, Nagoya, Japan.
¹⁰Toyama Prefectural Rehabilitation Hospital and Support Center for Children with Disabilities, Toyama, Japan.

When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effectiveness of diagnostic and therapeutic devices and the risk-benefit ratio of patients, caregivers, and healthcare professionals. The guidelines evidence-based of large clinical data for this purpose are presented by national medical societies. As one of the rupture risk indicators, there is the hazard risk ratio derived by the UCAS Japan research group based on the statistical method of 6697 aneurysms in 5720 patients with cerebral aneurysms of 3 mm or more. Therefore, we investigated the biomechanical significance of this hazard risk ratio using a spherical aneurysm model. It was revealed that 1) the reason why the frequency of aneurysm rupture is relatively high up to about 10 mm, 2) the UCAS hazard risk ratio corresponds to stress of the aneurysm wall, and the true stress can be calculated by multiplying the patient’s blood pressure, and 3) the factors that cause the daughter’s sac (irregular protrusion of the aneurysm wall). In addition, our two methods for measuring the strength of the blood vessel wall of an individual patient were described.

Cerebral Aneurysm, Rupture Risk, UCAS, Hazard Ratio, Biomechanics

Nogata, F. , Yokota, Y. , Kawamura, Y. , Morita, H. , Uno, Y. , Mouri, T. , Walsh, W. , Kawamura, T. , Hotta, N. and Kagechika, K. (2021) Biomechanical Considerations in the Unruptured Cerebral Aneurysm Study (UCAS Japan): Rupture Risk and True Stress of Wall. Journal of Biosciences and Medicines, 9, 172-189. doi: 10.4236/jbm.2021.910015.