Investigation of the Impact of Body Temperature and Post-Mortem Interval on Magnetic Resonance Imaging (MRI) of Unfixed Tissue

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). However, in the post-mortem imaging setting, the sensitivity of MR to subtle changes in tissue properties presents both problems and new opportunities. Normal temperature-dependent and post-mortem interval (PMI)-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 in the post-mortem setting. Our over-arching hypothesis is that post-mortem Magnetic Resonance (PMMR) will eventually find broader application, to forensic imaging and other disciplines, if the dependence of image contrast on temperature and normal post-mortem changes is better-understood. In this basic research study, we propose to study temperature-dependent and post-mortem changes in a thorough and systematic way. We will measure the tissue-specific MR parameters T1, T2, and the apparent diffusion coefficient (ADC) as a function of temperature for a variety of mammalian tissues. We will utilize this knowledge to identify tissue parameters for use as non-invasive thermometers, essential for optimizing imaging with respect to sample temperature. A generic procedure for improving PMMR imaging protocols, based on this knowledge, will then be developed and validated in studies of animals and human decedents. Finally we propose to study the impact of post-mortem interval (PMI) and decomposition temperature on tissue-specific MR parameters using intact animals. Preliminary studies by our group demonstrate the potential for developing PMMR as a non-invasive tool for rapidly estimating PMI (over the 2 day to 2 week range) in a future applied study. The successful completion of the proposed basic studies will provide a framework for improving PMMR imaging of unfixed tissues, applicable to a variety of fields, including biology, veterinary medicine, and human medical research. Further, these basic studies of the effect of temperature and PMI on PMMR of unfixed tissue, and the development of systematic procedures to adjust for these factors, are pre-requisites to successfully validating and applying PMMR to forensic investigation in the future. The success of these studies will motivate future applied research studies aimed at developing optimized MR imaging methods for specific applications in the forensic setting, such as evaluating cause, manner, and/or time of death or evaluating specific injuries or pathologies. ca/ncf