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Solis-Najera S, Ruiz R, Martin R, Vazquez F, Marrufo O, Rodriguez AO. A theoretical and experimental investigation on a volume coil with slotted end-rings for rat MRI at 7 T. MAGMA (NEW YORK, N.Y.) 2023; 36:911-919. [PMID: 37184611 PMCID: PMC10667404 DOI: 10.1007/s10334-023-01096-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 04/18/2023] [Accepted: 04/20/2023] [Indexed: 05/16/2023]
Abstract
OBJECTIVE A volume coil with squared slots-end ring was developed to attain improved sensitivity for imaging of rat's brain at 7 T. MATERIAL AND METHODS The principles of the high cavity resonator for the low-pass case and the law of Biot-Savart were used to derive a theoretical expression of [Formula: see text]. The slotted-end ring resonator showed a theoretical 2.22-fold sensitivity improvement over the standard birdcage coil with similar dimensions. Numerical studies were carried out for the electromagnetic fields and specific absorption rates for our coil and a birdcage coil loaded with a saline-filled spherical phantom and a digital brain of a rat. RESULTS An improvement of the signal-to-noise ratio (SNR) can be observed for the slotted volume coil over the birdcage regardless of the load used in the electromagnetic simulations. The specific absorption rate simulations show a decrement for the digital brain and quite similar values with the saline solution phantom. Phantom and rat's brain images were acquired at 7 T to prove the viability of the coil design. The experimental noise figure of our coil design was four times less than the standard birdcage with similar dimensions, which showed a 44.5% increase in experimental SNR. DISCUSSION There is remarkable agreement among the theoretical, numerical and experimental sensitivity values, which all demonstrate that the coil performance for MR imaging of small rodents can be improved using slotted end-rings.
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Affiliation(s)
- Sergio Solis-Najera
- Departamento de Fisica, Facultad de Ciencias, UNAM, 04510, Mexico City, Mexico
| | - Rodrigo Ruiz
- Departamento de Fisica, Facultad de Ciencias, UNAM, 04510, Mexico City, Mexico
| | - Rodrigo Martin
- Departamento de Fisica, Facultad de Ciencias, UNAM, 04510, Mexico City, Mexico
| | - Fabian Vazquez
- Departamento de Fisica, Facultad de Ciencias, UNAM, 04510, Mexico City, Mexico
| | - Oscar Marrufo
- Departamento de Fisica, Facultad de Ciencias, UNAM, 04510, Mexico City, Mexico
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Wang H, Zhao H, Li C, Dong J, Zhao J, Yue H, Lai Y, Zhao L, Wang H, Zhang J, Xu X, Yao B, Zhou H, Nie B, Du X, Peng R. Disrupted Topological Organization of Brain Network in Rats with Spatial Memory Impairments Induced by Acute Microwave Radiation. Brain Sci 2023; 13:1006. [PMID: 37508937 PMCID: PMC10377161 DOI: 10.3390/brainsci13071006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 06/18/2023] [Accepted: 06/26/2023] [Indexed: 07/30/2023] Open
Abstract
Previous studies have suggested that microwave (MW) radiation with certain parameters can induce spatial memory deficits. However, the effect of MW on the topological organization of the brain network is still unknown. This work aimed to investigate the topological organization of the brain network in rats with spatial memory impairments induced by acute microwave (MW) radiation. The Morris water maze (MWM) test and resting-state functional magnetic resonance imaging were performed to estimate the spatial memory ability and brain network topological organization of the rats after MW exposure. Compared with the sham group, the rats exposed to 30 mW/cm2 1.5 GHz MW radiation exhibited a significantly decreased normalized clustering coefficient (γ) (p = 0.002) 1 d after the exposure and a prolonged average escape latency (AEL) (p = 0.014) 3 d after the exposure. Moreover, after 10 mW/cm2 1.5 GHz MW radiation, a significantly decreased γ (p = 0.003) was also observed in the rats, without any changes in AEL. In contrast, no adverse effects on AEL or topological parameters were observed after 9.375 GHz MW radiation. In conclusion, the rats with spatial memory deficits induced by MW radiation exhibited disruptions in the topological organization of the brain network. Moreover, these topological organization disruptions emerged earlier than behavioral symptom onset and could even be found in the rats without a decline in the performance of the spatial memory task. Therefore, it is possible to use the topological parameters of the brain network as early and sensitive indicators of the spatial memory impairments induced by acute MW radiation.
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Affiliation(s)
- Haoyu Wang
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Haixia Zhao
- Beijing Institute of Radiation Medicine, Beijing 100850, China
- College of Education, Hebei University, Baoding 071002, China
| | - Chunfang Li
- Beijing Institute of Radiation Medicine, Beijing 100850, China
- Department of Radiology, The First Medical Center, Chinese PLA General Hospital, Beijing 100853, China
| | - Ji Dong
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Jianghao Zhao
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Hanlin Yue
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Yunfei Lai
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Li Zhao
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Hui Wang
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Jing Zhang
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Xinping Xu
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Binwei Yao
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Hongmei Zhou
- Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Binbin Nie
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Xiumin Du
- College of Education, Hebei University, Baoding 071002, China
| | - Ruiyun Peng
- Beijing Institute of Radiation Medicine, Beijing 100850, China
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Design and SAR assessment of three compact 5G antenna arrays. Sci Rep 2021; 11:21265. [PMID: 34711873 PMCID: PMC8553834 DOI: 10.1038/s41598-021-00679-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 10/15/2021] [Indexed: 12/04/2022] Open
Abstract
In this paper three different multi stub antenna arrays at 27–29.5 GHz are designed. The proposed antenna arrays consist of eight single elements. The structure of feeding parts is the same but the radiation elements are different. The feeding network for array is an eight way Wilkinson power divider (WPD). To guarantee the simulation results, one of the proposed structures is fabricated and measured (namely the characteristics of S11, E-, and H-plane patterns) which shows acceptable consistency with measurement results. The simulation results by CST and HFSS show reasonable agreement for reflection coefficient and radiation patterns in the E- and H- planes. The overall size of the proposed antenna in maximum case is 29.5 mm × 52 mm × 0.38 mm (2.8 \documentclass[12pt]{minimal}
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\begin{document}$${{\varvec{\lambda}}}_{0}$$\end{document}λ0). Moreover, for Specific Absorption Rate (SAR) estimation, a three-layer spherical human head model (skin, skull, and the brain) is placed next to the arrays as the exposure source. The simulation results show that the performance of proposed antennas as low-SAR sources makes them ideal candidates for the safe usage and lack of impact of millimeter waves (mmW) on the human health. In all three cases of SAR simulations the value of SAR1g and SAR10g are below the standard limitations.
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