Intra‐scan RF power amplifier drift correction

Aghaeifar, A., Bosch, D., Heule, R., Williams, S. , Ehses, P., Mauconduit, F. and Scheffler, K. (2024) Intra‐scan RF power amplifier drift correction. Magnetic Resonance in Medicine, (doi: 10.1002/mrm.30078) (Early Online Publication)

Abstract

Purpose The drift in radiofrequency (RF) power amplifiers (RFPAs) is assessed and several contributing factors are investigated. Two approaches for prospective correction of drift are proposed and their effectiveness is evaluated. Methods RFPA drift assessment encompasses both intra-pulse and inter-pulse drift analyses. Scan protocols with varying flip angle (FA), RF length, and pulse repetition time (TR) are used to gauge the influence of these parameters on drift. Directional couplers (DICOs) monitor the forward waveforms of the RFPA outputs. DICOs data is stored for evaluation, allowing calculation of correction factors to adjust RFPAs' transmit voltage. Two correction methods, predictive and run-time, are employed: predictive correction necessitates a calibration scan, while run-time correction calculates factors during the ongoing scan. Results RFPA drift is indeed influenced by the RF duty-cycle, and in the cases examined with a maximum duty-cycle of 66%, the potential drift is approximately 41% or 15%, depending on the specific RFPA revision. Notably, in low transmit voltage scenarios, FA has minimal impact on RFPA drift. The application of predictive and run-time drift correction techniques effectively reduces the average drift from 10.0% to less than 1%, resulting in enhanced MR signal stability. Conclusion Utilizing DICO recordings and implementing a feedback mechanism enable the prospective correction of RFPA drift. Having a calibration scan, predictive correction can be utilized with fewer complexity; for enhanced performance, a run-time approach can be employed.

• Item Type: Articles
• Additional Information: Funding information: ERC Advanced Grant, Grant/Award Number: 834940; Deutsche Forschungsgemeinschaft (DFG), Grant/Award Number: SCHE 658/12.
• Status: Early Online Publication
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Williams, Dr Sydney
• Authors: Aghaeifar, A., Bosch, D., Heule, R., Williams, S., Ehses, P., Mauconduit, F., and Scheffler, K.
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: Magnetic Resonance in Medicine
• Publisher: Wiley
• ISSN: 0740-3194
• ISSN (Online): 1522-2594
• Published Online: 12 March 2024
• Copyright Holders: Copyright: © 2024 The Authors
• First Published: First published in Magnetic Resonance in Medicine 2024
• Publisher Policy: Reproduced under a Creative Commons licence