Comprehensive RF safety concept for parallel transmission MR.

Purpose: The goal of this study is to increase patient safety in parallel transmission (pTx) MRI systems. A major concern in these systems is radiofrequency-induced tissue heating, which can be avoided by specific absorption rate (SAR) prediction and SAR monitoring before and during the scan.

Methods: In this novel comprehensive safety concept, the SAR is predicted prior to the scan based on precalculated fields obtained from electromagnetic simulations on different body models.

Detection of RF unsafe devices using a parallel transmission MR system.

Purpose: The permanent presence of devices (pacemakers) inside a patient, or the need to use other devices (catheters), for diagnosis and treatment, usually represents a contraindication for a magnetic resonance examination. To help overcome this problem, a novel and noninvasive magnetic resonance system-based concept is proposed to detect potentially unsafe radio frequency (RF) conditions of such devices to ensure patient safety.

Methods: This concept makes use of parallel transmit technology by monitoring currents in individual RF transmit coil elements during RF transmission using suitable current sensors.

A specific absorption rate prediction concept for parallel transmission MR.

The specific absorption rate (SAR) is a limiting factor in high-field MR. SAR estimation is typically performed by numerical simulations using generic human body models. However, SAR concepts for single-channel radiofrequency transmission cannot be directly applied to multichannel systems.

Local SAR management by RF shimming: a simulation study with multiple human body models.

Object: Parallel transmission facilitates a relatively direct control of the RF transmit field. This is usually applied to improve the RF field homogeneity but might also allow a reduction of the specific absorption rate (SAR) to increase freedom in sequence design for high-field MRI. However, predicting the local SAR is challenging as it depends not only on the multi-channel drive but also on the individual patient.

Toward individualized SAR models and in vivo validation.

The specific absorption rate (SAR) is a limiting constraint in sequence design for high-field MRI. SAR estimation is typically performed by numerical simulations using generic human body models. This entails an intrinsic uncertainty in present SAR prediction.