Dongsuk Sung
BME PhD Defense Presentation

Date: 2024-03-22
Time: 1:00 pm
Location / Meeting Link: Emory HSRB-II, N100 / https://emory.zoom.us/j/98446597886?pwd=d2psMmFsVFlrVmU4ekwyVHEzOVFiZz09

Committee Members:
Dr. Candace C. Fleischer (Advisor); Dr. John N. Oshinski; Dr. Andrei G. Fedorov; Dr. Shella D. Keilholz; Dr. Jason W. Allen; Dr. Fadi B. Nahab


Title: Combined MR Thermometry and First-Principles Modeling of Brain Temperature for Applications in Injury and Ischemia

Abstract:
The cerebral thermal environment is maintained through a delicate equilibrium of heat production by oxygenated metabolism and heat removal by circulation of cooler blood from the heart. Importantly, this equilibrium is highly susceptible to disruption after brain injury or ischemia. Minor elevations in temperature may lead to thermal damage, yet such assessments are challenged by the infrequent utilization of brain thermometry in clinical settings. Typically, core body temperature serves as a surrogate for brain temperature; however, post-injury or ischemia, these temperatures are often no longer correlated. In clinics, despite the known disparity between body and brain temperatures post-trauma, the adoption of brain thermometry into routine practices remains limited. The invasive nature of direct brain temperature assessments can lead to localized tissue damage among other complications, highlighting the critical demand for enhanced non-invasive brain thermometry techniques. In various interventions, including MR-guided thermal ablation and therapeutic hyperthermia for abdominal and pelvic tumors, magnetic resonance (MR) thermometry has been employed. Among MR-based methods, proton resonance frequency (PRF) chemical shift thermometry (CST) is notable for its capacity to measure absolute temperatures while reducing the influence of external magnetic field drifts and inter-scan motion, which are critical factors for high quality data. Unfortunately, its application in acute clinical scenarios like cardiac arrest, traumatic brain injury, or ischemic stroke is hampered by extended acquisition times and challenges in data acquisition in some brain regions, such as the frontal lobe near the nasal cavity. To address these challenges, researchers have made progress in developing computational models that can implement thermal interactions in vascularized tissue, particularly useful in experimentally challenging scenarios (e.g., acute settings, nonstandardized medical treatments, etc.). Despite progress in bioheat transfer modeling, realistic thermal modeling of the human brain remains elusive, and none of the previous models are corroborated with empirical thermometry data, largely because the anatomical representations are not specific to individual subjects. This dissertation presents a new approach to understanding brain temperature dynamics through the use of combined MR thermometry and first principles modeling. By developing and validating a personalized computational model rigorously satisfying mass, momentum, and energy conservation, this work offers novel insights into the spatial and temporal variations of brain temperature under various physiological and pathological conditions. The research elucidates the complex interplay between cerebral blood flow, metabolism, and heat transfer, providing a framework for predicting brain temperature distribution not only in healthy individuals but also in scenarios of chronic, steno-occlusive cerebrovascular disease and acute ischemic stroke. Overall, the findings from this dissertation underscore the potential of MR thermometry, combined with predictive modeling, as a powerful tool for enhancing diagnostic accuracy, optimizing therapeutic interventions, and improving patient outcomes in neurological care.