In this book, topics related to interaction of radiation with cells are dealt with, in which beneficial damage to cancer cells due to radiation therapy and hazards leading to injuries to normal cells and organs, are described in detail with illustrations and workbook examples. Topics, such as biological effects and normal tissue reaction of radiation, biological basis of external beam radiotherapy and brachytherapy, time-dose-fractionation methods, and radiation safety and protection, are well explained in simple terms for all sectors of people to understand.

I am sure, this book will be highly beneficial to postgraduate students preparing for MD and DNB examination in radiotherapy and those for MSc Medical Physics. Further, it would be very useful for professionals in their routine clinical practice in radiotherapy for calculation of effective dose due to various treatment protocols followed today.

Dr Thayalan really deserves compliments for compiling such a worthy book on radiobiology in a simple language for all sectors of personnel, both students and staff, who get benefited.

The outcome of any diagnostic and therapeutic procedure depends on the radiation interaction with tissue or cells, or simply based on radiobiological principles. Understanding of the above principle is very much essential not only to predict outcome but also to use effectively the given radiation technique or procedure. Hence, an attempt is made to explain the basics of human body, radiation physics, its interactions with tissue and cells, survival curves and its modifying agents, biological effects, biological basis of radiotherapy, and including radiation safety and protection, in the form of a single book. Attempt is also made to incorporate worked examples wherever needed. Large numbers of figures and tables are incorporated, wherever necessary, for better understanding of the concept.

This book is intended for the postgraduate students of medical physics, radiation oncology, and the radiology and imaging. This is a first book of its kind. I am very proud and happy to come out with this book, incorporating my three decades of teaching experience in radiological physics. Constructive comments are invited from the readers for the betterment of the book in its next edition.

I thank Dr PG Gopalakrishna Kurup, Apollo Specialty Hospital, Chennai, Tamil Nadu, India, for having written the foreword to this book. I am also thankful to Shri Jitendar P Vij (Group Chairman), Mr Ankit Vij (Group President), Mr Tarun Duneja (Director-Publishing) and Bengaluru Production Unit of M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, for publishing this book as usual in a neat and elegant manner.10