The potential of magnetic resonance imaging/spectroscopy (MRI/S) for whole-body applications at high (e 3 tesla) fields and of head applications at ultrahigh (e7 tesla) fields appears to be limitless. It is;however, hindered by significant challenges including safety concerns regarding exceeding radiofrequency (RF) power deposition in tissue and large image inhomogeneity/voids due to "undesired" RF field inhomogeneity across the anatomy. It is widely accepted that parallel (multi) transmission approaches where the MRI RF coil/array is excited at multiple of its elements using, what-appear-to-be, arbitrarily RF pulses are the solutions for alleviating these challenges. The widespread implementation of these approaches into a full scale scientific and clinical research using these MRI/S systems has been hampered by significant obstacles such as significant subject-to-to-subject sensitivity, SNR losses, and unclear safety concerns regarding the assurance of the multi-transmit experiment. The objective of this work is to design and implement a new and novel class of multi-transmit RF arrays and methodologies that will make parallel-transmission approaches practical in current and future MRI scanners;enhancing their capabilities into new levels of SNR and sensitivity. We will design and implement a new multi-transmit 7 tesla head arrays that are coupled (with significant SNR enhancement and RF field overlapping,) and subject-insensitive. The performance of the proposed RF arrays are minimally affected by differences in the subjects and therefore provides safe operation and eliminates the need for RF field mapping, pre-scanning, and preparation time. To evaluate the usefulness of these arrays on practical MRI applications, we will use our multi-transmit capable 7 tesla human scanner to evaluate the visual cortex and the hippocampus and frontal lobes in the context of Alzheimer's disease. At the end of this project we will provide our findings and the designs of the subject-insensitive RF arrays and the associated RF field maps to the scientific community. As the proposed RF arrays are subject-insensitive, the designs and the RF field maps can be directly implemented on any 7 tesla human MRI system without the need for a stand alone multi-transmission capability.

Public Health Relevance

This project will result in significant improvements in high field magnetic resonance imaging (MRI.) The project will advance the safety and performance of the MRI technology impacting research in medicine in general and in Alzheimer's disease in particular.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Research Project (R01)
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Biomedical Imaging Technology Study Section (BMIT)
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Liu, Guoying
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University of Pittsburgh
Biomedical Engineering
Schools of Engineering
United States
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Krishnamurthy, Narayanan; Zhao, Tiejun; Ibrahim, Tamer S (2014) Effects of receive-only inserts on specific absorption rate, B1 (+) field, and Tx coil performance. J Magn Reson Imaging 39:475-84
Zheng, Hai; Zhao, Tiejun; Qian, Yongxian et al. (2011) Improved large tip angle parallel transmission pulse design through a perturbation analysis of the Bloch equation. Magn Reson Med 66:687-96
Tang, Lin; Hue, Yik-Kiong; Ibrahim, Tamer S (2011) Studies of RF Shimming Techniques with Minimization of RF Power Deposition and Their Associated Temperature Changes. Concepts Magn Reson Part B Magn Reson Eng 39B:11-25