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Halaney DL, Katta N, Fallah H, Aguilar G, Milner TE. Group Refractive Index of Nanocrystalline Yttria-Stabilized Zirconia Transparent Cranial Implants. Front Bioeng Biotechnol 2021; 9:619686. [PMID: 33869149 PMCID: PMC8044953 DOI: 10.3389/fbioe.2021.619686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 03/02/2021] [Indexed: 11/18/2022] Open
Abstract
Transparent “Window to the Brain” (WttB) cranial implants made from a biocompatible ceramic, nanocrystalline Yttria-Stabilized Zirconia (nc-YSZ), were recently reported. These reports demonstrated chronic brain imaging across the implants in mice using optical coherence tomography (OCT) and laser speckle imaging. However, optical properties of these transparent cranial implants are neither completely characterized nor completely understood. In this study, we measure optical properties of the implant using a swept source OCT system with a spectral range of 136 nm centered at 1,300 nm to characterize the group refractive index of the nc-YSZ window, over a narrow range of temperatures at which the implant may be used during imaging or therapy (20–43°C). Group refractive index was found to be 2.1–2.2 for OCT imaging over this temperature range. Chromatic dispersion for this spectral range was observed to vary over the sample, sometimes flipping signs between normal and anomalous dispersion. These properties of nc-YSZ should be considered when designing optical systems and procedures that propagate light through the window, and when interpreting OCT brain images acquired across the window.
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Affiliation(s)
- David L Halaney
- Laboratory of Guillermo Aguilar, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States
| | - Nitesh Katta
- Laboratory of Thomas Milner, Department of Biomedical Engineering, University of Texas, Austin, TX, United States
| | | | - Guillermo Aguilar
- Laboratory of Guillermo Aguilar, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States
| | - Thomas E Milner
- Laboratory of Thomas Milner, Department of Biomedical Engineering, University of Texas, Austin, TX, United States
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Halaney DL, Jonak CR, Liu J, Davoodzadeh N, Cano-Velázquez MS, Ehtiyatkar P, Park H, Binder DK, Aguilar G. Chronic Brain Imaging Across a Transparent Nanocrystalline Yttria-Stabilized-Zirconia Cranial Implant. Front Bioeng Biotechnol 2020; 8:659. [PMID: 32695757 PMCID: PMC7339873 DOI: 10.3389/fbioe.2020.00659] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/28/2020] [Indexed: 12/28/2022] Open
Abstract
Repeated non-diffuse optical imaging of the brain is difficult. This is due to the fact that the cranial bone is highly scattering and thus a strong optical barrier. Repeated craniotomies increase the risk of complications and may disrupt the biological systems being imaged. We previously introduced a potential solution in the form of a transparent ceramic cranial implant called the Window to the Brain (WttB) implant. This implant is made of nanocrystalline Yttria-Stabilized Zirconia (nc-YSZ), which possesses the requisite mechanical strength to serve as a permanent optical access window in human patients. In this present study, we demonstrate repeated brain imaging of n = 5 mice using both OCT and LSI across the WttB implant over 4 weeks. The main objectives are to determine if the WttB implant allows for chronic OCT imaging, and to shed further light on the question of whether optical access provided by the WttB implant remains stable over this duration in the body. The Window to the Brain implant allowed for stable repeated imaging of the mouse brain with Optical Coherence Tomography over 28 days, without loss of signal intensity. Repeated Laser Speckle Imaging was also possible over this timeframe, but signal to noise ratio and the sharpness of vessels in the images decreased with time. This can be partially explained by elevated blood flow during the first imaging session in response to trauma from the surgery, which was also detected by OCT flow imaging. These results are promising for long-term optical access through the WttB implant, making feasible chronic in vivo studies in multiple neurological models of brain disease.
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Affiliation(s)
- David L Halaney
- Laboratory of Guillermo Aguilar, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States
| | - Carrie R Jonak
- Laboratory of Devin Binder, Division of Biomedical Sciences, University of California, Riverside, Riverside, CA, United States
| | - Junze Liu
- Laboratory of Hyle Park, Department of Bioengineering, University of California, Riverside, Riverside, CA, United States
| | - Nami Davoodzadeh
- Laboratory of Guillermo Aguilar, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States
| | - Mildred S Cano-Velázquez
- Laboratory of Juan Hernandez-Cordero, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Pasha Ehtiyatkar
- Laboratory of Guillermo Aguilar, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States.,Department of Neuroscience, University of California, Riverside, Riverside, CA, United States
| | - Hyle Park
- Laboratory of Hyle Park, Department of Bioengineering, University of California, Riverside, Riverside, CA, United States
| | - Devin K Binder
- Laboratory of Devin Binder, Division of Biomedical Sciences, University of California, Riverside, Riverside, CA, United States
| | - Guillermo Aguilar
- Laboratory of Guillermo Aguilar, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States
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