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Pubmed for Handhelds

PUBMED FOR HANDHELDS

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  • Title: Toward whole-cortex enhancement with an ultrahigh dielectric constant helmet at 3T.
    Author: Sica CT, Rupprecht S, Hou RJ, Lanagan MT, Gandji NP, Lanagan MT, Yang QX.
    Journal: Magn Reson Med; 2020 Mar; 83(3):1123-1134. PubMed ID: 31502708.
    Abstract:
    PURPOSE: To present a 3T brain imaging study using a conformal prototype helmet constructed with an ultra-high dielectric constant (uHDC; εr ~ 1000) materials that can be inserted into standard receive head-coils. METHODS: A helmet conformal to a standard human head constructed with uHDC materials was characterized through electromagnetic simulations and experimental work. The signal-to-noise ratio (SNR), transmit efficiency, and power deposition with the uHDC helmet inserted within a 20-channel head coil were measured in vivo and compared with a 64-channel head coil and the 20-channel coil without the helmet. Seven healthy volunteers were analyzed. RESULTS: Simulation and in vivo experimental results showed that transmit efficiency was improved by nearly 3 times within localized regions for a quadrature excitation, with a measured global increase of 58.21 ± 6.54% over 7 volunteers. The use of a parallel transmit spokes pulse compensated for severe degradation of B1+ homogeneity, at the expense of higher global and local specific absorption rate levels. A SNR histogram analysis with statistical testing demonstrated that the uHDC helmet enhanced a 20-channel head coil to the level of the 64-channel head coil, with the improvements mainly within the cortical brain regions. CONCLUSION: A prototype uHDC helmet enhanced the SNR of a standard head coil to the level of a high density 64-channel coil, although transmit homogeneity was compromised. Further improvements in SNR may be achievable with optimization of this technology, and could be a low-cost approach for future radiofrequency engineering work in the brain at 3T.
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