PURPOSE To develop a protocol to non-invasively measure and map fat fraction, fat/(fat+water), as a function of age in the adult thymus for future studies monitoring the effects of interventions aimed at promoting thymic rejuvenation and preservation of immunity in older adults. MATERIALS AND METHODS Three-dimensional spoiled gradient echo 3T MRI with 3-point Dixon fat-water separation was performed at full inspiration for thymus conspicuity in 36 volunteers 19 to 56 years old. Reproducible breath-holding was facilitated by real-time pressure recording external to the console. The MRI method was validated against localized spectroscopy in vivo, with ECG triggering to compensate for stretching during the cardiac cycle. Fat fractions were corrected for T1 and T2 bias using relaxation times measured using inversion recovery-prepared PRESS with incremented echo time. RESULTS In thymus at 3 T, T1water = 978 ± 75 ms, T1fat = 323 ± 37 ms, T2water = 43.4 ± 9.7 ms and T2fat = 52.1 ± 7.6 ms were measured. Mean T1-corrected MRI fat fractions varied from 0.2 to 0.8 and were positively correlated with age, weight and body mass index (BMI). In subjects with matching MRI and MRS fat fraction measurements, the difference between these measurements exhibited a mean of -0.008 with a 95% confidence interval of (0.123, -0.138). CONCLUSIONS 3-point Dixon MRI of the thymus with T1 bias correction produces quantitative fat fraction maps that correlate with T2-corrected MRS measurements and show age trends consistent with thymic involution.

中文翻译：

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通过局部NMR和三点Dixon MRI技术测量人胸腺中的脂肪含量。

目的开发一种以无创方式测量和绘制成年胸腺中脂肪比例（脂肪/（脂肪+水）的函数）的方案，以供将来研究，以监测旨在促进胸腺年轻化和保持免疫力的干预措施的效果老年人。材料与方法在36例19至56岁的志愿者中，充分激发了胸腺的显着性，进行了3​​点Dixon脂肪-水分离的三维变质梯度回波3T MRI。可通过控制台外部的实时压力记录来促进可重现的屏气。MRI方法已针对体内局部光谱进行了验证，其中ECG触发可补偿心动周期中的拉伸。使用松弛时间校正脂肪级分的T1和T2偏差，松弛时间使用反演恢复准备的PRESS和增加的回波时间测量。结果在3 T的胸腺中，测得T1water = 978±75 ms，T1fat = 323±37 ms，T2water = 43.4±9.7 ms，T2fat = 52.1±7.6 ms。经T1校正的MRI脂肪平均分数在0.2到0.8之间变化，并且与年龄，体重和体重指数（BMI）正相关。在具有匹配的MRI和MRS脂肪分数测量值的受试者中，这些测量值之间的差异表现出平均值-0.008，95％置信区间为（0.123，-0.138）。结论胸腺的3点Dixon MRI结合T1偏差校正可产生定量的脂肪分数图，该图与经T2校正的MRS测量值相关，并显示与胸腺退化相符的年龄趋势。测量了T1water = 978±75 ms，T1fat = 323±37 ms，T2water = 43.4±9.7 ms和T2fat = 52.1±7.6 ms。经T1校正的MRI脂肪平均分数在0.2到0.8之间变化，并且与年龄，体重和体重指数（BMI）正相关。在具有匹配的MRI和MRS脂肪分数测量值的受试者中，这些测量值之间的差异表现出平均值-0.008，95％置信区间为（0.123，-0.138）。结论胸腺的3点Dixon MRI结合T1偏差校正可产生定量的脂肪分数图，该图与经T2校正的MRS测量值相关，并显示与胸腺退化相符的年龄趋势。测量了T1water = 978±75 ms，T1fat = 323±37 ms，T2water = 43.4±9.7 ms和T2fat = 52.1±7.6 ms。经T1校正的MRI脂肪平均含量在0.2到0.8之间变化，并且与年龄，体重和体重指数（BMI）正相关。在具有匹配的MRI和MRS脂肪分数测量值的受试者中，这些测量值之间的差异表现出平均值-0.008，95％置信区间为（0.123，-0.138）。结论胸腺的3点Dixon MRI结合T1偏差校正可产生定量的脂肪分数图，该图与经T2校正的MRS测量值相关，并显示与胸腺退化相符的年龄趋势。体重和体重指数（BMI）。在具有匹配的MRI和MRS脂肪分数测量值的受试者中，这些测量值之间的差异表现出平均值-0.008，95％置信区间为（0.123，-0.138）。结论胸腺的3点Dixon MRI结合T1偏差校正可产生定量的脂肪分数图，该图与经T2校正的MRS测量值相关，并显示与胸腺退化相符的年龄趋势。体重和体重指数（BMI）。在具有匹配的MRI和MRS脂肪分数测量值的受试者中，这些测量值之间的差异表现出平均值-0.008，95％置信区间为（0.123，-0.138）。结论胸腺的3点Dixon MRI结合T1偏差校正可产生定量的脂肪分数图，该图与经T2校正的MRS测量值相关，并显示与胸腺退化相符的年龄趋势。