RF system calibration for global Q matrix determination

TY - JOUR

T1 - RF system calibration for global Q matrix determination

AU - Padormo, Francesco

AU - Beqiri, Arian

AU - Malik, Shaihan J.

AU - Hajnal, Joseph V.

PY - 2016/6/1

Y1 - 2016/6/1

N2 - 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.

AB - 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.

KW - MRI Calibration

KW - Parallel transmission

KW - Q Matrix

KW - SAR

U2 - 10.1016/j.mri.2015.12.039

DO - 10.1016/j.mri.2015.12.039

M3 - Article

SN - 0730-725X

VL - 34

SP - 690

EP - 693

JO - Magnetic Resonance Imaging

JF - Magnetic Resonance Imaging

IS - 5

ER -