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High-resolution MRI images are essential for the accurate diagnosis of diseases. Increasing the magnetic field strength achieves this but also raises the Specific Absorption Rate (SAR) of electromagnetic waves in the body, leading to safety concerns. Currently, SAR is managed by assuming an even distribution of electromagnetic waves; however, high-field MRI can cause localized concentrations. No direct method for SAR visualization exists that relies on numerical analysis, resulting in conservative management and inefficiency. This paper presents a method for converting temperature images from magnetic resonance imaging (MRI) into SAR images using Pennes' bioheat equation and Fourier transformation with gentle low-pass filtering. The method was tested using an agar-gel phantom heated with a heating RF coil, and the temperature changes were measured using the proton resonance frequency shift (PRFS) technique in a 3T MRI system. The results are validated by electromagnetic numerical simulations using xFDTD. Experimental results showed SAR images could be reconstructed from temperature images with a maximum error of 3.6 % compared with numerical simulations. The reconstruction took 5.2 s on a PC. This method can aid in managing electromagnetic safety in MRI and verifying the RF coil performance during development. Future studies will validate this method using different phantom configurations and in vivo experiments. [ABSTRACT FROM AUTHOR]

The increased magnetic field strength in MRI improves the spatial resolution and image quality of the metabolic activity of the human body by increasing the SNR. As the magnetic field increases, the level of RF exposure increases; therefore, extra care should be taken with high-field MRI scans. MRI regulated by IEC 60601-2-33 has been reported in several studies to be inefficient in MRI operation owing to overly conservative SAR-based regulations. The latest revisions to the IEC and ICNIRP show a dramatic increase in the use of temperature-based analytical descriptions. This is mainly because SAR does not consider the thermoregulatory mechanisms of the human body, which makes the SAR exposure levels conservative, whereas temperature-based analyses assume that the thermoregulatory mechanisms of the human body are inherently present. In this study, we synthesized the results of a primate numerical model and thermal simulation in a 1.5 T MRI to analyze the exposure to electromagnetic waves in the MRI and the resulting temperature increase. In addition, we analyzed the results of numerical observations of the impact on body temperature rise when blood flow, a major factor in thermoregulation, was decreased by 90 %, showing a temperature rise of 39.3°C and a CEM43 value of 0.07 min. [ABSTRACT FROM AUTHOR]