The Essential Physics of Medical Imaging

Citation

Bushberg, J. T., Seibert, J. A., Leidholdt, E. M., Jr., & Boone, J. M. (2020). The Essential Physics of Medical Imaging (4th ed.). Wolters Kluwer.

Chapter Summary

The fourth edition is a large book of about 1,030 pages in four sections and nine appendices, written by scientists and educators from the University of California, Davis. The publisher describes it as a coherent and thorough compendium of the physics, radiation protection and radiation biology that underlie medical imaging, covering the production, characteristics and interactions of non-ionizing and ionizing radiation, magnetic fields and ultrasound, and the modalities that use them: radiography, mammography, fluoroscopy, computed tomography, magnetic resonance, ultrasound and nuclear medicine. It is full-colour with more than 1,000 images, charts and graphs.

Section I, Basic Concepts: Chapters 1–5

Chapter 1, "Introduction to Medical Imaging", surveys the modalities, digital imaging basics and image properties. Chapter 2, "Radiation and the Atom", and Chapter 3, "Interaction of Radiation with Matter", supply the physics: electromagnetic radiation, atomic and nuclear structure, particle and photon interactions, attenuation, and dose quantities such as equivalent and effective dose. Chapter 4, "Image Quality", covers spatial resolution, contrast resolution, noise and noise texture, ratio measures and measures based on visual performance. Chapter 5, "Medical Imaging Informatics", covers standards, networking, PACS, the lifecycle of a radiology exam, security and privacy, big data and algorithms for analytics, and the business of informatics.

Section II, Diagnostic Radiology: Chapters 6–9

Chapter 6, "X-ray Production, Tubes, and Generators", treats the x-ray source. Chapter 7, "Radiography", covers projection geometry, scatter, technique, and detectors from screens and computed radiography to flat panels, with exposure index, artifacts, pediatric considerations and dual-energy subtraction. Chapter 8, "Breast Imaging: Mammography", and Chapter 9, "Fluoroscopy", complete the projection modalities. Chapter 8 includes dosimetry and regulatory requirements, and Chapter 9 image quality and radiation management for patients and staff.

Chapters 10–11: Computed Tomography; X-ray Dosimetry in Projection Imaging and Computed Tomography

Chapter 10 covers basic concepts, system designs, acquisition modes, reconstruction, image quality and artifacts in CT. Chapter 11 turns to x-ray dosimetry: dose deposition, Monte Carlo simulation, dose metrics, dose in radiography, fluoroscopy and CT, dose reporting software and registries, and diagnostic reference levels.

Chapters 12–13: Magnetic Resonance

Chapter 12, "Magnetic Resonance Basics", covers magnetic fields and properties, the MR system, the signal, tissue magnetization, basic pulse sequences, signal localization and k-space. Chapter 13 covers advanced acquisition methods, fast imaging, flow, perfusion and diffusion contrast, artifacts, spectroscopy, quality control, siting, bioeffects and safety.

Chapter 14: Ultrasound

Sound and its interactions with tissue, transducers and beam properties, data acquisition and processing, image quality, Doppler, artifacts, performance and quality assurance, and acoustic power and bioeffects.

Section III, Nuclear Medicine: Chapters 15–19

Chapter 15 covers radioactivity and nuclear transformation. Chapter 16 covers radionuclide production, radiopharmaceuticals and internal dosimetry. Chapter 17 covers radiation detection and measurement, including counting statistics. Chapter 18 deals with the gamma camera, and Chapter 19 with SPECT, PET and dual-modality PET/CT and PET/MRI, including advances in PET imaging.

Section IV, Radiation Biology and Protection: Chapters 20–21

Chapter 20, "Radiation Biology", moves from interactions with cells and tissue through the acute radiation syndrome to carcinogenesis, hereditary effects, effects in utero and risk communication. Chapter 21, "Radiation Protection", covers sources of exposure, personnel dosimetry, shielding, protection in x-ray and nuclear medicine, regulatory limits, prevention of errors, program management, pregnant patients and radiation emergencies.

Section V, Appendices A–I

Appendix A reviews fundamental principles of physics; B gives units, constants and conversion factors; C and D give radiologic data and mass attenuation coefficients; E effective, organ and fetal doses from imaging procedures; F radiopharmaceutical characteristics and dosimetry; G convolution and Fourier transforms; H radiation dose comparisons; and I radionuclide therapy home care guidelines.

Key Concepts

Chapters 1–5: Basic concepts

• Ionizing and non-ionizing radiation: the radiation types that imaging uses.
• Attenuation and dose: how radiation is absorbed, and how dose is quantified.
• Image quality measures: spatial resolution, contrast, noise and visual performance.
• Imaging informatics: PACS, standards and security.

Chapters 6–14: Diagnostic radiology

• X-ray production: tubes and generators.
• Radiographic, mammographic and fluoroscopic imaging: detectors, technique and dose.
• CT reconstruction and dosimetry: image formation and radiation dose in CT.
• MR signal, pulse sequences and k-space: how magnetic resonance images are made.
• Ultrasound and Doppler: sound-based imaging and flow measurement.

Chapters 15–21: Nuclear medicine, biology and protection

• Radioactivity and radiopharmaceuticals: sources of nuclear imaging signals.
• Gamma camera, SPECT and PET: nuclear imaging systems.
• Radiation biology and protection: biological effects, dose limits and shielding.

Critical Analysis

Strengths

• Broad coverage of the clinical modalities. Radiography, mammography, fluoroscopy, CT, MR, ultrasound and nuclear medicine each get their own chapters, together with the common topics of image quality and informatics.
• Radiation safety is integral. Dosimetry, biology and protection run to three chapters (11, 20, 21), and the modality chapters also treat dose, so the book serves readers who must manage exposure.
• Reference apparatus. Nine appendices provide data tables (attenuation coefficients, dose estimates, radiopharmaceutical dosimetry) and a mathematical appendix on convolution and Fourier transforms.
• Updated for the fourth edition. The publisher lists new material on informatics-oriented concepts, multisource x-ray tubes, digital breast tomosynthesis, dedicated breast CT, 3T and 7T MRI, ultrasound elastography, nuclear cardiology and total-body PET, and completely updated radiopharmaceutical, internal dosimetry and radiation biology chapters.
• Written for professional training. The publisher describes it as a resource for imaging professionals, radiology residents preparing for core exams, and teachers and students of medical physics and biomedical engineering.

Limitations

• Very large. At over 1,000 pages the book is a reference as much as a text, and a one-semester course must select.
• Clinical rather than design-oriented. The coverage is organised by modality and radiation topic; it is not a signals-and-systems treatment of image formation, and the mathematics of convolution and Fourier transforms is confined to an appendix.
• Edition-dependent. Fast-moving topics such as informatics, CT technology and PET are described as of 2020.

Where It Fits in the Course

Among the course's books, this is the comprehensive reference on the physics of the clinical modalities and radiation safety. Nadine Smith and Andrew Webb's Introduction to Medical Imaging is a compact introduction to the physics, instrumentation and clinical uses of the main modalities, and Wolbarst, Capasso and Wyant's Medical Imaging: Essentials for Physicians explains the physics conceptually for readers who will use images. Paul Suetens's Fundamentals of Medical Imaging is a compact, heavily illustrated text on image formation and image computing, and Prince and Links's Medical Imaging Signals and Systems builds the modalities on a common signals-and-systems framework. Barrett and Myers's Foundations of Image Science is a graduate treatment of the mathematics and statistics of imaging systems and image quality.

Use Bushberg as the main reference alongside or after one of the compact introductions. Pair it with Prince and Links for the mathematics of image formation, and with Barrett and Myers for rigorous image-quality theory.

How to Use This Book

The book is aimed at imaging professionals, radiology residents and students of medical physics and biomedical engineering, and a background in university-level physics and mathematics is a sensible preparation.

A practical plan:

• Core for a first pass: Chapters 1 to 4 (modalities, radiation, interactions, image quality), then the chapters on the modalities of interest.
• By modality: x-ray (6–9), CT (10–11), MR (12–13), ultrasound (14) or nuclear medicine (15–19). Each modality can be read as a self-contained block once Chapters 1 to 4 are done.
• Safety: Chapters 20 and 21 should be read by anyone who will operate or supervise ionizing-radiation equipment.
• Reference: use the appendices and Chapter 5 as needed.

Treat the book as a reference to dip into by modality, and use the data tables for calculations rather than reading the appendices straight through.