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RF system calibration for global Q matrix determination

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)690-693
Number of pages4
JournalMagnetic Resonance Imaging
Issue number5
Early online date30 Dec 2015
Publication statusPublished - 1 Jun 2016


King's Authors


The use of multiple transmission channels (known as Parallel Transmission, or PTx) provides increased control of the MRI signal formation process. This extra flexibility comes at a cost of uncertainty of the power deposited in the patient under examination: the electric fields produced by each transmitter can interfere in such a way to lead to excessively high heating. Although it is not possible to determine local heating, the global Q matrix (which allows the whole-body Specific Absorption Rate (SAR) to be known for any PTx pulse) can be measured in-situ by monitoring the power incident upon and reflected by each transmit element during transmission. Recent observations have shown that measured global Q matrices can be corrupted by losses between the coil array and location of power measurement. In this work we demonstrate that these losses can be accounted for, allowing accurate global Q matrix measurement independent of the location of the power measurement devices.

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