Non-invasive measurement of absolute temperature is important for proper characterization of various pathologies and for evaluation of thermal dose during interventional procedures. The proton (hydrogen nucleus) magnetic resonance (MR) frequency shift method can be used to map relative temperature changes. However, spatiotemporal variations in the main magnetic field and the lack of local internal frequency reference challenge the determination of absolute temperature. Here, we introduce a multinuclear method for absolute MR thermometry, based on the fact that the hydrogen and sodium nuclei exhibit a unique and distinct characteristic frequency dependence with temperature and with electrolyte concentration. A one-to-one mapping between the precession frequency difference of the two nuclei and absolute temperature is demonstrated. Proof-of-concept experiments were conducted in aqueous solutions with different NaCl concentrations, in agarose gel samples, and in freshly excised ex vivo mouse tissues. One-dimensional chemical shift imaging experiments also demonstrated excellent agreement with infrared measurements.

绝对温度的非侵入式测量对于各种病理的正确表征以及在介入治疗过程中评估热剂量非常重要。质子（氢核）磁共振（MR）频移方法可用于绘制相对温度变化。然而，主磁场的时空变化和局部内部频率参考的缺乏对绝对温度的确定提出了挑战。在此，我们基于氢和钠原子核对温度和电解质浓度表现出独特而独特的特征频率依赖性这一事实，介绍了一种用于绝对MR测温的多核方法。证明了两个核的进动频率差与绝对温度之间的一对一映射。在不同NaCl浓度的水溶液，琼脂糖凝胶样品以及新鲜切除的离体小鼠组织中进行概念验证实验。一维化学位移成像实验还证明了其与红外测量的出色一致性。