Magnetic resonance thermal imaging in combination with parallel MRI technique in the presence of motion

Magnetic resonance thermal imaging (MRTI) plays a very important role in MRI-guided thermal ablation procedure of tumors or cancers. MR temperature imaging has been used to generate real-time in vivo temperature maps for monitoring and guiding thermal therapies such as radiofrequency ablation (RFA), laser ablation, focused ultrasound ablation, and cryotherapy. In this way, the treatment can be tailored to meet very specific endpoints for individual patients with immediate feedback-ensuring the coagulation of cancer to its margin and protecting adjacent normal tissue around the cancer.;MR temperature maps, however, are easily corrupted by motion, meaning MR thermal imaging techniques are limited to static organs. Previous methods of reducing motion artifacts have drawbacks that prevent them from being optimal for the application of thermal MRI.;The main purpose of this dissertation is to develop and optimize an MR thermometry method combined with parallel MRI techniques in phantom experiments with respect to detecting and correcting motion artifacts of phantoms.;We used TX151 gel phantoms which were constructed with a tube running through. 60°C hot water was pumped through the tube to create a thermal gradient for imaging. The phantoms were moved in a controlled fashion during scanning. We simulated an in vivo liver motion as a simple, linear, and harmonic motion using a motor system. The phantoms were moved and returned to the original position without deformation and rotation (rigid-body motion) - amplitude of 1.5 cm and frequency of 0.25 Hz. Imaging was performed on a 3T MRI system with a FLASH sequence. Data was acquired with 8 channel head coils simultaneously and stored separately for later processing, and then MR images were reconstructed with MatLab.;Motion artifacts of the phantoms were detected and corrected using the SMASH navigator technique, and then MR temperature maps were obtained by complex subtraction proton resonance frequency (PRF) shift method. Temperature obtained by MR thermal imaging was compared to that measured via thermocouples. MR thermal imaging combined with the parallel MRI technique resulted in accurate temperature maps of the mobile phantoms heated by hot water. The combination of MR thermal imaging and the parallel MRI techniques will be a very important tool for cancer treatment in mobile organs.