Improved Temperature Measurement for Permanent MRI System by Using Hybrid PRF/T1 Method
1 Institute of Medical Information, School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China
2 Ningbo Xingaoyi Co.,LTD, Ningbo 315000, China
Abstract：To investigate the feasibility of improving temperature measurement on the permanent MRI system using hybrid PRF/T1 method. The phantom consisting mainly of AGAR to simulate liver tissue was heated to 65℃ in water bath and naturally cooled to 36℃ inside a 0.3T permanent MRI scanner. During cooling process, the phantom was scanned by gradient echo sequences with flip angles of 40° and 75° with cooling step of 1℃. The collected data were separately processed with PRF, T1 and hybrid PRF/T1 methods to acquire the temperature measurement. The temperature values measured by an alcohol thermometer were utilized as the reference to evaluate the accuracy of the three MRI thermometry methods. The coefficient of variation of temperature values measured by three separate experiments was calculated to assess method repeatability. The experimental results showed that the temperature measurement errors of PRF and T1 methods were approximately ±6℃， while that of the hybrid PRF/T1 method was below ±3℃， the coefficient of variation was 3.12% for the PRF method, 7.53% for the T1 method, and 2.63% for the hybrid PRF/T1 method. For permanent MRI system, the hybrid PRF/T1 method is more accurate and reproducible than the PRF and T1 only methods, and offers a promising tool for temperature monitoring in tumor thermometry.
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