Evaluation of MR thermometry with proton resonance frequency method at 7T

Abstract

Quantitative and non-invasive temperature mapping using magnetic resonance imaging (MRI) provides a unique way to measure temperature evolution inside biological tissues. The method is widely used in thermal ablation procedures with magnetic fields at or below 3T. In this paper, the sensitivity of the MRI thermometry at 7T was studied using a proton resonance frequency (PRF)-based technique. We first used an agarose gel phantom with MR-compatible thermometry to calibrate the temperature coefficient, and then this temperature coefficient was employed to measure the internal temperature in both ex vivo (beef muscle) and in vivo (rat) experiments using focused ultrasound heating. The temperature coefficient calibrated by the phantom was 0.0095 ppm/℃, and both the ex vivo and in vivo experiments exhibited clear temperature evolution. This quantitative study confirmed the sensitivity (<1 ℃) of MR temperature mapping at 7T.

Development of Ferrite-Based Temperature Sensors for Magnetic Resonance Imaging: A Study of Cu1−xZnxFe2Alghamdi1, Hankiewicz2, Anderson3 et al. 2018Phys. Rev. Applied251100View full textAdd to dashboardCite

“…However, this method has certain limitations. PRF does not work with adipose tissue and is very sensitive to body movement (cardiac and/or respiratory) [15]. These issues can be partially mitigated with the referenceless PRF method [16].…”

Assessment of radio-frequency heating of a parallel transmit coil in a phantom using multi-echo proton resonance frequency shift thermometry

“…**The positioning error of the fibre optic probe was chosen as the half of the PRF image resolution used in the experiment. ***The standard deviation of the alpha coefficient was derived from three literature studies involving 1–2% agar phantoms [ [37] , [38] , [39] ]. Parameter Default Value Adjusted Value Thermal Elevation using Default Value [°C] Thermal Elevation using Adjusted Value [°C] Sensitivity Factor Measurement Std.…”

“…7 ). [ [37] , [38] , [39] ]. The changes were marginal within the given RF heating condition, but the alpha coefficient must be carefully considered for the studies related to high-thermal rise, such as hyperthermia or implant safety testing.…”

“…Where γ = 42.576 MHz/T, α = −0.00988 ± 0.0065 ppm/°C [ [37] , [38] , [39] ], B 0 = 7 T, TE = echo time and Δϕ drift is derived from the two-channel fibre optic probe at the centre and edge of the phantom [ 24 , 37 ]. The remaining system frequency drift was corrected using the field drift information recorded during a non-RF heating experiment, and the correction results were rechecked against the measured temperature from the two-channel fibre optic probes.…”

Updating the Risk Stratification for Sudden Cardiac Death in Cardiomyopathies: The Evolving Role of Cardiac Magnetic Resonance Imaging. An Approach for the Electrophysiologist

“…Regarding real-time lesion formation assessment, acute LGE grossly overestimates the effect (ECV expansion), while thenoncontrast method, using fast T1-and T2-weighted imaging [127][128][129][130] has only been able to acutely detect a minority (~30%) of lesions. CMR thermography is a newly introduced parameter with promising results [42,131,132].…”