Aims and objectives
During an MR procedure,
most of the transmitted RF power is transformed into heat within the patients’ tissue resulting from resistive losses,
referred to as the specific energy absorption rate(SAR) (2).
The EU standardisation has mandated that all scanners must measure SAR in patients and develop system safeguards to ensure that the limits(IEC60602-3-33) are not exceeded.
Accurate estimation of SAR is critical in safeguarding patients who may be unconscious/sedated,
have implants or are...
Methods and materials
As there is a negligible contribution from thermal conduction in our SAR assessment and our phantom is a nonperfused material,
physiological changes can be ignored.
The SAR at discreet points in the observation plane the can be determined Where C agar is 4200J/kg,
Δ T is the change in temprature and Δ t is the change in time.
Proton Resonance Frequency Shift (PRF) thermometry was utilised to find the change in temperature. Where α is the temprature coefficanet 0.01ppm/C,
γ is the gyromatnetic...
Phase maps were created pre and post heating.
These were then used to create a phase difference map and a heat map could then be created using PRF.
A FLAIR sequence was used over the whole volume to heat the phantom.
The calculated SAR was compared to the scanner readout.
Discussion. Our results agreed with the manufacturer's outputed .
Conclusion. We have developed an open source phantom that can independently verify the temperature rise associated with SAR.
Crook N et al.,
J Magn Reson Imaging.