Analysis of Cervical Tumor Metabolism and Design of Magnetic Resonance Imaging Sequences for Abdominal and Pelvic Tissue/Tumor Hypoxia Studies
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Tumor oxygenation is increasingly recognized as an important factor to enhance the efficacy of chemo- and radiotherapy. MRI is becoming a widely accepted diagnostic imaging modality for investigation of tumor oxygenation. Research to improve the effectiveness of MR techniques for detection of oxygenation biomarkers (T1 and T2*) in the tissue/tumor hypoxia studies mainly includes efforts to improve sensitivity, efficiency and accuracy of measurements and to minimize scan duration. This dissertation mainly focuses on the development of novel combined multi-parametric techniques to obtain both BOLD and TOLD images simultaneously. A novel approach (ms-mGEPI-T1,2*) is developed to simultaneously measure both T1- and T2*-weighted signal changes, as well as and T1- and T2*-maps serially during a single dynamic MRI scan. This method has also been validated in both phantom and human abdominal tissue experiments and both in vitro and in vivo results are in good agreement with those obtained using conventional methods and the literature. The ms-mGEPI-T1,2* has been found to provide sensitive BOLD and TOLD responses under an oxygen challenge. Two enhanced versions of the ms-mGEPI-T1,2* technique with higher temporal resolution (SR-based sequence) or more accurate relaxation time estimation (IR-based sequence) are developed and validated in phantom and 3 volunteer studies. Relaxation times measured by these novel methods were in good agreement with those obtained using conventional pulse sequences. A pulse sequence which combines all three methods was developed for use on Philips MR user interface and has great potential in clinical MR examinations.