Determining the temperature-dependence of tissue relaxation times (T1 and T2) for prospective optimization of post-mortem magnetic resonance (PMMR) image contrast

Abstract

Abstract Due to the excellent sensitivity of Magnetic Resonance (MR) imaging to subtle differences in soft tissues, MR enables non-invasive anatomical imaging with superior soft tissue contrast relative to X-ray computed tomography (CT). Soft tissue contrast in MR is not determined primarily by density (as in X-ray imaging) but instead by T1 and T2, tissue-specific parameters that characterize the temporal behavior of the MR signal. However, in the post-mortem setting, the sensitivity of MR to subtle changes in tissue properties presents both opportunities and challenges. Recent reports in the literature demonstrate changes in MR image contrast as a function of subject temperature for a given MRI protocol (e.g., T1-w, T2-2, FLAIR). These normal temperature-dependent changes in MR image contrast, not encountered in clinical MR of live subjects, have the potential to confound the identification of pathology or injury. Tofts et al. have demonstrated that FLAIR image contrast can be corrected by adjusting the protocol, specifically the inversion time (TI), based on knowledge of the temperature-dependence of the apparent diffusion coefficient (ADC) and T1 in brain tissues. Here we present a generalized method for (A) non-invasively determining subject temperature and (B) computing the values of the image acquisition parameters, TR and TE, required to obtain the desired image contrast for a given subject temperature, based on the temperature-dependence of tissue T1 and T2 values. Measurements of the temperature-dependence of T1 and T2 values from various unfixed, ex vivo mammalian tissues and organs will be presented. Author disclosures National Institute of Justice Award 2012-DN-BX-K019 is gratefully acknowledged.