The Practice of Internal Dosimetry in Nuclear Medicine

Michael G. Stabin

• Publisher: CRC Press
• Year: 2016
• Print ISBN:
  9780367849504
• eBook ISBN:
  9781315355481
• Topic: Medicine
• Subtopic: Oncology

Written by one of the world's leading experts in the field of nuclear medicine dosimetry, this text describes in detail the use of internal dose calculations in the practice of nuclear medicine. While radiation therapy with external sources of radiation always employs calculations of dose to optimize therapy for each patient, this is not routinely conducted in nuclear medicine therapy. As the trend towards an increasing role of dosimetry in therapy planning increases, this book reviews the available methods and technologies available to make this a more common practice.

The book begins by covering the mathematical fundamentals of internal dose calculations, and uses sample calculations to demonstrate key principles. The book then moves forward to describe anthropomorphic models, dosimetric models, and types and uses of diagnostic and therapeutic radiopharmaceuticals. The depth of coverage makes it useful reference and guide for researchers performing dose calculations and for physicians considering incorporating dose calculations into the treatment of their cancer patients.

Chapter 1

Basic Principles of Internal Dosimetry Calculations

Paracelsus, born Philippus Aureolus Theophrastus Bombastus von Hohenheim in 1493, is regarded as the “father of toxicology.” He is associated with the quote “Everything is poison, there is poison in everything. Only the dose makes a thing not a poison.” In the science of radiation protection, the quantity of central focus is dose, which has a very specific definition, to be given shortly. Many radiation effects, be they positive or negative, are generally related to the dose of radiation that a person, animal, or other biological entity has received. Indeed, dose to physical structures can produce radiation damage at high enough levels as well. Thus, radiation protection professionals (health physicists)^* focus much of their daily efforts in evaluating radiation doses and their possible consequences. However, as we will see, this quantity dose in radiation protection is often modified by certain factors to account for specific biological responses, and so is an imperfect, although necessary, quantity to calculate or measure.

Radiation doses may be received from external or internal sources. This text is devoted to the evaluation of internal doses (most appropriately called internal dose assessment rather than dosimetry, as measurements are typically not involved; nonetheless, internal dosimetry is the term generally used), and specifically internal doses received due to the practice of nuclear medicine. Internal exposures to radioactive materials also occur in some industrial practices; while all of the principles involved in the calculations are the same, the applications are different and will not be treated in much detail in this text.

Quantities and Units

The basic quantity of radiation dosimetry is absorbed dose, which is just the energy absorbed by any object per unit mass of the object. Absorbed dose is relevant for any kind of radiation being absorbed by any kind of matter. Of course, we are mostly interested in the absorbed dose to human tissue, but one may calculate the absorbed dose to any material (e.g., air, water, wood). The textbook definition of absorbed dose is:

$$\begin{array}{cc}\frac{d\text{ε}}{dm}& (1.1)\end{array}$$

where dε is the differential energy deposited in mass dm. So, for any application, we just need to calculate how much energy is absorbed by an object and divide by its mass. The quantity of absorbed dose is the gray (Gy), which is 1 J/kg. In internal dose calculations, our objects are either normal tissues or tumors, although we may also be interested in dose to different regions of organs (e.g., kidney medulla vs. kidney cortex), and we can even go to the voxel level to calculate doses to very small portions of organs, depending on the resolution of our images. Many ...

Table of contents

• Cover
• Halftitle Page
• Series Title
• Title Page
• Copyright
• Contents
• Series Preface
• Preface
• Author
• Chapter 1 Basic Principles of Internal Dosimetry Calculations
• Chapter 2 Current Anthropomorphic Models for Dosimetry (Phantoms)
• Chapter 3 Use of Animal Models in Internal Dose Calculations
• Chapter 4 Special Dosimetry Models
• Chapter 5 Dose Calculations for Diagnostic Pharmaceuticals
• Chapter 6 Approved Radiopharmaceuticals
• Chapter 7 Current Pharmaceuticals Used in Nuclear Medicine Therapy
• Chapter 8 The Need for Patient-Individualized Dosimetry in Therapy
• Chapter 9 Radiation Biology
• Chapter 10 Future Needs and Prospects
• Index