Medical Imaging: Essentials for Physicians

Citation

Wolbarst, A. B., Capasso, P., & Wyant, A. R. (2013). Medical Imaging: Essentials for Physicians. Wiley-Blackwell.

Chapter Summary

The book, about 430 pages, was written by a medical physicist, an interventional radiologist and an emergency physician without special training in radiology. The publisher describes it as intentionally brief and not overly detailed, aimed at clinicians who need enough command of imaging to discuss it with colleagues, explain it to students, nurses and technologists, and describe it to patients. After an introductory case study, thirteen chapters move from an overview of all modalities to image quality and dose, X-ray imaging old and new, radiation risk, digital imaging, CT, nuclear medicine, ultrasound, MRI and emerging methods, ending with suggested further reading.

Introduction: Dr. Doe's Headaches: An Imaging Case Study

A single patient's work-up shows the modalities in clinical use: CT, the picture archiving and communication system (PACS), T1, T2 and FLAIR MRI, MR spectroscopy as a "virtual biopsy", functional MRI, diffusion tensor imaging, MR-guided biopsy, pathology, the question of PET, and treatment and follow-up.

Chapter 1: Sketches of the Standard Imaging Modalities: Different Ways of Creating Visible Contrast Among Tissues

A survey of every major modality, organised around how each creates contrast: X-ray attenuation in radiography, fluoroscopy and CT, differential uptake of radiopharmaceuticals in nuclear medicine, SPECT and PET, tissue elasticity and density in ultrasound, and proton spin relaxation in MRI. An appendix on selecting imaging modalities covers chest pain, abdominal and pelvic, head and neck, musculoskeletal and vascular imaging.

Chapter 2: Image Quality and Dose: What Constitutes a "Good" Medical Image?

Introduces the "image quality quartet" of contrast, resolution, random noise and artifacts, always weighed against patient dose, along with quality assurance and the balance of medical benefits against radiation risks.

Chapters 3–4: Creating Subject Contrast in the Primary X-ray Image; Twentieth-century (Analog) Radiography and Fluoroscopy

Chapter 3 explains how an X-ray beam is produced, how photons interact with tissue and receptors, how subject contrast arises and what the beam does to the body in dose and risk. Chapter 4 covers screen-film radiography, the determinants of image quality, the special requirements of mammography and image-intensifier fluoroscopy.

Chapter 5: Radiation Dose and Radiogenic Risk

Explains why exposure to ionising radiation has risen, how DNA damage causes stochastic effects such as cancer, deterministic effects at high doses and effects on the unborn child, and the principles of radiation safety.

Chapters 6–7: Twenty-first Century (Digital) Imaging; Digital Planar Imaging

Chapter 6 covers digital computers, acquisition and representation of images, image processing, PACS and RIS networks, computer-assisted detection, network security and displays. Chapter 7 describes computed radiography, flat-panel digital radiography, digital mammography, digital fluoroscopy and subtraction angiography, and tomosynthesis.

Chapter 8: Computed Tomography: Superior Contrast in Three-Dimensional X-Ray Attenuation Maps

CT image reconstruction, seven generations of scanners, technology and image quality, artifacts, and dose and quality assurance, with an appendix on the mathematics of filtered back-projection.

Chapter 9: Nuclear Medicine: Contrast from Differential Uptake of a Radiopharmaceutical by Tissues

Radioactivity, radiopharmaceuticals, the gamma camera, static and dynamic studies, SPECT and PET, and quality assurance and radiation safety.

Chapter 10: Diagnostic Ultrasound: Contrast from Differences in Tissue Elasticity or Density Across Boundaries

The physics of the ultrasound beam, piezoelectric transducers, attenuation and reflection at interfaces, A-, M- and B-mode imaging in up to four dimensions, Doppler imaging of blood flow, elastography, and safety.

Chapters 11–12: MRI in One Dimension and with No Relaxation; Mapping T1 and T2 Relaxation in Three Dimensions

A two-step introduction to MRI. Chapter 11, described as a gentle introduction to a challenging subject, builds nuclear magnetic resonance from quantum and classical viewpoints, then one-dimensional imaging, free induction decay and spin echo, and MRI instrumentation. Chapter 12 adds T1 and T2 relaxation, T2* and gradient-echo sequences, imaging in two and three dimensions, and imaging of flow and motion.

Chapter 13: Evolving and Experimental Modalities

A short look at optical and near-infrared imaging, molecular imaging and nanotechnology, thermography, terahertz, microwave and electron spin resonance imaging, electrophysiological and impedance imaging, photoacoustic imaging, and the role of computing.

Key Concepts

Introduction and Chapters 1–2: Foundations

• Contrast mechanisms: each modality distinguishes tissues through a different physical property, the organising idea of the book.
• Image quality quartet: contrast, resolution, noise and artifacts, always balanced against dose.
• Choosing a modality: matching the imaging test to the clinical question.

Chapters 3–8: X-ray imaging and radiation

• Differential attenuation: tissues absorb X-rays to different degrees, producing subject contrast.
• Stochastic and deterministic effects: random effects such as cancer, which can arise from a mutation in a single cell, contrasted with the killing of many tissue cells at high doses.
• Digital imaging and PACS: solid-state receptors, image processing and networked storage and display.
• CT reconstruction: building cross-sectional maps of attenuation from many projections.

Chapters 9–12: Other modalities

• Radiopharmaceuticals: radioactive labels attached to organ-specific agents to image function.
• Acoustic impedance and Doppler: reflection at tissue boundaries forms ultrasound images, frequency shifts measure blood flow.
• T1 and T2 relaxation: the proton relaxation times that give MRI its soft-tissue contrast.

Critical Analysis

Strengths

• Written for users of images. The physician co-authors and the clinical framing, from the opening case study to the modality-selection appendix, keep the physics tied to clinical decisions. Melvin E. Clouse of Harvard Medical School, quoted by the publisher, calls it an excellent primer for all members of the medical profession, including non-radiologists.
• Little mathematics. Clouse notes that the book uses little mathematics beyond simple algebra while presenting complex ideas clearly; the one mathematical appendix, on filtered back-projection, is set apart at the end of the CT chapter.
• Dose and safety throughout. Image quality is always set against dose, a whole chapter is given to radiation risk, and the CT, nuclear medicine and ultrasound chapters each end with dose or safety and quality assurance.
• Gentle route into MRI. Two chapters introduce MRI in stages, first without relaxation and in one dimension, then adding T1, T2 and three-dimensional imaging.

Limitations

• Conceptual rather than quantitative. Engineering and physics students will not find derivations, signals-and-systems analysis or problem sets for practising calculation.
• Uneven weight. Analog film and image-intensifier technology still occupy a full chapter, while newer topics such as molecular imaging are treated briefly in the final survey chapter.
• Dating. Published in 2013, the book predates later developments in digital detectors, reconstruction and hybrid imaging, so the "evolving" modalities chapter in particular should be read as a snapshot.

Where It Fits in the Course

Wolbarst, Capasso and Wyant is the conceptual, clinically framed entry point to this course. Smith and Webb's Introduction to Medical Imaging covers the same modalities more compactly but at an engineering level, with solved problems and exercises for senior undergraduates and beginning graduate students; it is the natural next step for students who want to calculate rather than describe. Suetens's Fundamentals of Medical Imaging and Prince and Links's Medical Imaging Signals and Systems treat image formation mathematically, the latter through a common signals-and-systems framework.

Bushberg and colleagues' The Essential Physics of Medical Imaging is a comprehensive reference on imaging physics and radiation protection for radiology residents and medical physicists; Wolbarst and colleagues can serve as a readable preview of it. Barrett and Myers's Foundations of Image Science is a graduate text on the mathematics and statistics of image quality, far beyond this book.

How to Use This Book

The book is written for physicians, and suits medical students, residents and practising clinicians outside radiology, physician-assistant students and biomedical students who want to understand how imaging works without the mathematics. School-level physics and algebra are enough.

A practical plan:

• Read the Introduction and Chapters 1–2 first. They give the map of all modalities and the vocabulary of image quality and dose used throughout.
• X-ray sequence: Chapters 3, 5, 6 and 8 are the core for anyone ordering radiographs and CT; Chapters 4 and 7 can be skimmed for the technology of film and digital receptors, except for mammography if relevant.
• Other modalities: Chapters 9 and 10 according to specialty; read Chapters 11 and 12 together, in order, since the second builds directly on the first.
• Chapter 13 is optional background on emerging techniques.

Use the Chapter 1 appendix on selecting modalities alongside clinical rotations, and revisit the dose and safety sections when discussing risks with patients. Students who later need quantitative understanding should continue with Smith and Webb or Bushberg and colleagues.