Implant / Implant's Designing & Manufacturing
Ehsan Mohammadi Mahmoei; Reza Lashgari; Behrouz Salamat
Volume 16, Issue 3 , December 2022, , Pages 195-205
Abstract
The human body has five main senses of sight, hearing, taste, smell and touch. The defective performance of any of these senses causes us to solve this problem and use technology for this purpose. The sense of hearing is no exception and several attempts have been made to restore it, which has led to ...
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The human body has five main senses of sight, hearing, taste, smell and touch. The defective performance of any of these senses causes us to solve this problem and use technology for this purpose. The sense of hearing is no exception and several attempts have been made to restore it, which has led to the design of various implants. In this study, with the aim of investigating the function of the auditory midbrain implant (AMI) in restoring hearing ability, the cat’s auditory system has been stimulated in acoustic and electrical stimulation. Electrical stimuli are the result of AMI injecting current into the central nucleus of the inferior colliculus (ICC) and acoustic stimuli are the result of pure tone sound in the cat’s ear. After stimulation, responses were extracted from the primary auditory cortex of the cat's brain. Finally, a neural network (NN) with backpropagation-based modelling has been used. After data acquisition and processing, it was clear that AMI successfully stimulated the ICC. But it is associated with delays during stimulation. After model creation, it was found that the Levenberg-Marquardt algorithm with 10 neurons in the hidden layer had the best performance compared to the others with an error of 0.009. Also, both models show similar behaviour to frequency changes, but the electrical model at a constant frequency shows a bigger response at the output. Finally, the interval between the transmission of the neural message from the cochlear nucleus to the inferior colliculus was calculated at 9 milliseconds.
Implant / Implant's Designing & Manufacturing
Shima Bahramizadeh-Sajadi; Hamid Reza Katoozian; Alireza Baradaran-Rafii; Miguel-Angel Ariza-Gracia; Philippe Buchler
Volume 15, Issue 4 , March 2022, , Pages 329-339
Abstract
Keratoconus (KC) is a non-inflammatory and degenerative disease of the cornea. It is manifested by the formation of cone-shaped regions accompanying severe eyesight issues. Implantation of intrastromal corneal ring segments (ICRS) is a popular treatment to improve visual acuity. Controversies exist ...
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Keratoconus (KC) is a non-inflammatory and degenerative disease of the cornea. It is manifested by the formation of cone-shaped regions accompanying severe eyesight issues. Implantation of intrastromal corneal ring segments (ICRS) is a popular treatment to improve visual acuity. Controversies exist over restoring functionality of different ICRSs. In this study, numerical models were used to quantify the mechanical and optical effects of different ICRSs on a reference cornea with central cone. Finite element (FE) simulations were used to simulate the implantation of two classes of ICRS sets common in clinical settings: a) single segment arcs of 360º (1×360), 350º (1×350), 320º (1×320), and, b) symmetric double-segment arcs of 160º each (2×160), 150º each (2×150), 120º each (2×120), and 90º each (2×90). Results showed that implantation of symmetric double-segment arcs caused the symmetric displacement and stress distribution contours on both anterior and posterior corneal surfaces. This study shows the potential impact of a detailed mechanical analysis of ICRS placement and represents a first step toward the development of an evidence-based nomogram for the different implantation techniques and the optimization of the surgical intervention based on patient-specific modeling.
