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Published on: February 12, 2014
Global and peak local specific absorption rate control on parallel transmit systems using k-means SAR compression
Xianglun Mao1, Sumra Bari1, David J Love1
1School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA.
Purpose:
To improve the specific absorption rate (SAR) compression model capability in parallel transmission (pTx) MRI systems.
Methods:
A k-means clustering method is proposed to group voxels with similar SAR behaviors in the scanned object, providing a controlled upper-bounded estimation of peak local SARs. This k-means compression model and the conventional virtual observation point (VOP) model were tested in a pTx MRI framework. The pTx pulse design with different SAR controlling schemes was simulated using a numerical human head model and an eight-channel 7T coil array. Multiple criteria (including RF power, global and peak local SARs, and excitation accuracy) were compared for the performance testing.
Results:
The k-means compression model generated a narrower overestimation bound, leading to a more accurate local SAR estimation. Among different pTx pulse design approaches, the k-means compression model showed the best trade-off between the SAR and excitation accuracy.
Conclusions:
The developed SAR compression model is advantageous for pTx framework given the narrower overestimation bound and control over the compression ratio. Results also illustrate that a moderate increase of maximum RF power can be useful for reducing the maximum local SAR deposition.
