Over the last few years, the use of FDG PET/CT in oncology has increased exponentially, and it showed appreciated impact in cancer patient's management. However; through these years some difficulties in application of FDG PET/CT in oncology rose up including non-specificity of FDG for cancer tissue, combined radiation exposure from FDG and CT and other technical pitfalls. This book, therefore, provides collection of some research handled application of FDG PET/CT in head and neck and rectal cancer patients. Also showed some limitation of FDG PET/CT in these cancers and provide modified protocols to overcome these limitations. This book should be especially useful to professionals in Oncology, Radiology, Nuclear medicine and Medical physics fields, or anyone else who may be interesting in cancer research and management.