一种在永磁MRI 系统上利用混合PRF /T1的改进测温方法

doi:10.3969/j.issn.0258-8021.2013.02.06

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摘要研究基于混合PRF/T₁的测温方法，以提高永磁MRI温度测量的准确度与可靠性。用琼脂凝胶仿真肝脏组织制作体模，将体模放在水浴中加热到65℃，然后置于03T永磁MRI系统用翻转角为40°与75°的梯度回波序列进行交替连续扫描，在降温中温度每下降1℃采集一次数据直到36℃。对所采集数据，分别用质子共振频率（PRF）方法、水质子纵向弛豫时间（T₁）方法、改进的混合PRF/T₁方法计算温度变化，并以酒精温度计测温结果作为参考。比较这3种方法的测温准确度，3 d内分别进行3次测温实验，用3次实验结果的变异系数(COV)评价测温方法可重复性。结果表明，仅用PRF或T₁方法的测温误差为±6℃，而改进的混合PRF/T₁方法的测温误差为±3℃。PRF方法的COV=3.12%，T₁方法的COV=7.53%，改进的混合PRF/T₁方法的COV=2.63%。在永磁MRI系统上采用改进的混合PRF/T₁方法比单一用PRF或T₁方法的测温准度高且可重复性好，可以更好的满足肿瘤热消融对温度监控的需求。

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	王雷¹李璟²朱剑锋²钟智辉¹陈武凡¹冯衍秋^1*

关键词 ： MRI测温, 质子共振频率, T₁测量, 混合PRF/T₁

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/T₁method is more accurate and reproducible than the PRF and T₁ only methods, and offers a promising tool for temperature monitoring in tumor thermometry.

Key words： magnetic resonance thermometry proton resonance frequency T₁ measurement hybrid PRF/T₁

基金资助:国家重点基础研究发展计划（973计划）（2010CB732502）

引用本文:

王雷¹李璟²朱剑锋²钟智辉¹陈武凡¹冯衍秋^1*
. 一种在永磁MRI 系统上利用混合PRF /T1的改进测温方法[J]. 中国生物医学工程学报, 2013, 32(2): 161-168.
WANG Lei¹LI Jing²ZHU JianFeng²ZHONG ZhiHui¹CHEN WuFan^1FENG YanQiu^{1*
. Improved Temperature Measurement for Permanent MRI System by Using Hybrid PRF/T₁ Method. journal1, 2013, 32(2): 161-168.}

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