The objective of this book is to present a comprehensive review which includes a definitive documentation on mathematical as well as theoretical aspects of different methodologies used in each design step of intensity based medical image registration system. This book also focuses on the limitations of each methodology and discussed about recently proposed approaches of the respective methodologies. Further, this book presents the summary and outcomes of various intensity based medical image registration systems applied on medical images of human body parts such as brain, heart, abdomen, retina, breast etc. arising from various medical imaging modalities which include Computerized Tomography-Computerized Tomography (CT-CT), Computerized Tomography-Positron Emission Tomography (CT-PET), Positron Emission Tomography-Magnetic Resonance Imaging (PET- MRI), and Ultrasound Computerized Tomography (US-CT).