Further observations on the measurement of tissue T¹ to monitor temperature in vivo by MRI

Abstract

Previous results for the measurement of T1 as a means of monitoring temperature have demonstrated a linear calibration with a coefficient of the order of 1.5%/degrees C. We have studied the changes in T1 further, and observe that changes in tissue perfusion are substantial contributors to the effects observed, and that the model of what is happening is complex and may not permit a simple temperature calibration.

Validation of MR thermometry technology: a small animal model for hyperthermic treatment of tumours

“…In vivo MR temperature measurements are rare and include mainly muscle [11,[27][28][29] of volunteers, seldom tumour tissue [7,30]. However, the above-mentioned MR parameters are not only sensitive to temperature but also to tissue perfusion and tissue type [11,31]. Therefore, it was our aim to design an experimental set-up including the online monitoring of tumour blood flow to improve the understanding of the complex dependencies between temperature and tumour perfusion in terms of their contribution to MR-sensitive parameters.…”

“…Once the animal was fixed, its position was not altered until the end of the MRI examination. Due to the approximate linear relationship between temperature and T1 relaxation time, this approach has been recommended for MR thermometry [18]. For calculation of T1 maps, a turbo FLASH pulse sequence [19,20] was implemented (α=15°, TE=4 ms, TR=11 ms).…”

NMR Temperature Measurements Using a Paramagnetic Lanthanide Complex

“…Interest in this technology has been motivated by traditional high-resolution NMR applications, as well as by the growing importance of medical hyperthermia and tissue ablation. Thus, a serious need has arisen for fast, sensitive, accurate, and preferably biocompatible NMR thermal mapping techniques (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Most of the published methods involve chemical shift measurements using water or fluorocarbons as thermometric materials.…”

Interventional MRI: update

“…The stud- ies suggested a slight rise in T1 with heating, and a signal decrease in T1-weighted images over a limited range (28±43°). However in vivo temperature measurement based on T1 changes showed that these changes can be influenced by tissue perfusion and proton density variations [14,15]. There is a significant hysteresis existing between signal intensity and temperature [14].…”