scholarly journals Studies of RF shimming techniques with minimization of RF power deposition and their associated temperature changes

2011 ◽  
Vol 39B (1) ◽  
pp. 11-25 ◽  
Author(s):  
Lin Tang ◽  
Yik-Kiong Hue ◽  
Tamer S. Ibrahim
Keyword(s):  
Rf Power ◽  
Temperature Changes ◽  
Power Deposition ◽  
Rf Shimming ◽  
Rf Power Deposition

scholarly journals Safety and data quality of simultaneous EEG-fMRI using multi-band fMRI imaging

2020 ◽  
Author(s):  
Maximillian K. Egan ◽  
Ryan Larsen ◽  
Jonathan Wirsich ◽  
Brad P. Sutton ◽  
Sepideh Sadaghiani
Keyword(s):  
Data Quality ◽  
Resting State ◽  
Human Subjects ◽  
Rf Power ◽  
Power Deposition ◽  
Eyes Closed ◽  
Eeg Data ◽  
Magnetic Field Magnitude ◽  
Rf Power Deposition ◽  
Multi Band

AbstractPurposeSimultaneously recorded electroencephalography and functional magnetic resonance imaging (EEG-fMRI) is highly informative yet technically challenging. Until recently, there has been little information about the data quality and safety when used with newer multi-band (MB) fMRI sequences. Here, we assessed heating-related safety of a MB protocol on a phantom, then evaluated EEG quality recorded concurrently with the MB protocol on humans.Materials and MethodsWe compared radiofrequency (RF)-related heating and magnetic field magnitude () of a fast MB fMRI sequence with whole-brain coverage (TR=440ms, MB factor=4) against a previously recommended, safe single-band (SB) sequence using a phantom outfitted with a 64-channel EEG cap. Temperatures were recorded at the ECG and TP7 electrodes using a fluoroptic thermometer. Next, 6 human subjects underwent eyes-closed resting state EEG-fMRI with the MB sequence. EEG data quality was assessed by the ability to remove gradient and cardioballistic artifacts and a clean spectrogram.ResultsRF induced heating was lower at both electrodes in the MB sequence compared to the SB sequence at ratios of 0.7 and 0.8, respectively. These ratios are slightly greater than the ratio of RF power deposition of the sequences, which is 0.64. However, our results are consistent with the use of RF power deposition, characterized by , in predicting less heating in the MB sequence than the SB sequence. In the resting state EEG data, gradient and cardioballistic artifacts were successfully removed using traditional template subtraction. All subjects showed an individual alpha peak in the spectrogram with a posterior topography characteristic of eyes-closed EEG.ConclusionsOur study shows that is a useful indication of the relative heating of fMRI protocols. This observation indicates that simultaneous EEG-fMRI recordings using this MB sequence can be safe in terms of RF-related heating, and that EEG data recorded using this sequence is of acceptable quality.

Sign in / Sign up

Export Citation Format

Share Document