Data analysis and instrumentation applications require an excellent knowledge of the interactions between radiation and matter, radiation and particle detectors, the principles and conditions of detector operation, as well as the limitations and advantages. This book provides abundant information about the energy deposition in detecting systems, the performance and optimization of detectors. It also addresses the situation where detectors (scanners of various types, etc.) have to be modified and improved to full optimization by the users. Furthermore, the book offers a description of detectors and techniques used in medical physics and covers physics principles and instrumentation knowledge needed in radioprotection and nuclear engineering. This book will benefit graduate (MSc and PhD) and final year BSc students as a reference and a supplement for courses in particle/astroparticle/space physics and instrumentation. A large part of it is directed toward courses in medical physics. The book can also be used by researchers in experimental particle physics at low, medium and high energy who are dealing with instrumentation.