This book provides a comprehensive overview of computational methods used in radiation oncology and imaging physics, addressing clinical and research applications. It reflects the way in which technology has revolutionized these fields, for example showing how highly accurate model-based dose calculation engines are derived from transport theory, and how optimization tools enable delivery of highly conformal dose distributions, and how image processing, registration, and reconstruction tools are driving towards adaptive treatment planning. Readers will gain the skillset needed to adapt general mathematical techniques to real problems encountered in today's practice.