REFERENCELESS PRF THERMOMETRY WITH MULTI-ECHO PROCESSING

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Referenceless proton resonance frequency (PRF) shift thermometry is inherently robust to tissue motion because the subtraction of a baseline phase image acquired prior to heating is not necessary. Instead, the background phase is estimated in every individual image from a frame region of interest (ROI) surrounding the heating region. For thermal monitoring during prostate ablation, we have proposed an extension to referenceless thermometry that allows temperature estimation in the presence of phase discontinuities between water and fat. Methods and Discussion: Here, we developed a pulse sequence where all three echoes are acquired in a single acquisition for increased temporal resolution of the temperature monitoring during thermal ablation. It has been shown that due to the relatively low spatial resolution of the heating distribution it is sufficient to acquire a low resolution image for temperature monitoring (1.7-1.9 mm in plane). To visualize the anatomical structures, however, higher resolution is desired. In the proposed pulse sequence, each echo¿s k-space coverage varies in order to allow reconstruction of both a low resolution temperature image and a high resolution anatomical image, without a decrease in temporal resolution. The method is demonstrated in phantoms and during in vivo canine prostate ablation.