Hendee's Physics of Medical Imaging

Ehsan Samei, Donald J. Peck

• Publisher: Wiley-Blackwell
• Year: 2019
• ISBN:
  9781118670965
• Edition: 5
• Topic: Medicina
• Subtopic: Radiologia, radioterapia e medicina nucleare

An up-to-date edition of the authoritative text on the physics of medical imaging, written in an accessible format

The extensively revised fifth edition of Hendee's Medical Imaging Physics, offers a guide to the principles, technologies, and procedures of medical imaging. Comprehensive in scope, the text contains coverage of all aspects of image formation in modern medical imaging modalities including radiography, fluoroscopy, computed tomography, nuclear imaging, magnetic resonance imaging, and ultrasound.

Since the publication of the fourth edition, there have been major advances in the techniques and instrumentation used in the ever-changing field of medical imaging. The fifth edition offers a comprehensive reflection of these advances including digital projection imaging techniques, nuclear imaging technologies, new CT and MR imaging methods, and ultrasound applications. The new edition also takes a radical strategy in organization of the content, offering the fundamentals common to most imaging methods in Part I of the book, and application of those fundamentals in specific imaging modalities in Part II. These fundamentals also include notable updates and new content including radiobiology, anatomy and physiology relevant to medical imaging, imaging science, image processing, image display, and information technologies.

The book makes an attempt to make complex content in accessible format with limited mathematical formulation. The book is aimed to be accessible by most professionals with lay readers interested in the subject. The book is also designed to be of utility for imaging physicians and residents, medical physics students, and medical physicists and radiologic technologists perpetrating for certification examinations. The revised fifth edition of Hendee's Medical Imaging Physics continues to offer the essential information and insights needed to understand the principles, the technologies, and procedures used in medical imaging.

1
Physics of Radiation and Matter

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CHAPTER MENU

1. 1.1 Introduction
2. 1.2 Electromagnetic Radiation
3. 1.3 Radioactivity
4. 1.4 Radiation Interactions with Matter
5. 1.5 Production of X-rays
6. 1.6 Radiation Detectors
7. References

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1.1 Introduction

Medical imaging at its core relies on foundational physics of electromagnetic radiation, atomic structure of stable and radioactive matter, and the interaction of radiation with matter. Associated with these topics are the process of X-ray formation and detection. Most medical imaging technologies exploit the principles associated with these foundational physics to form the medical image. These principles also impose fundamental limitations of what is possible; nature never meets our expectations for the ideal. This necessitates innovation to find technological solutions to mitigate fundamental challenges. Most advances in imaging technology have in fact been founded on innovations that best address these fundamental limitations. Therefore, insights into medical imaging and its progress necessitate an understanding of the physics of radiation and matter. Thus, it is most appropriate that we first address the foundational physics of radiation and matter in this chapter followed in Chapter 2 by a foundation of human anatomy and physiology.

1.2 Electromagnetic Radiation

Electromagnetic radiation consists of oscillating electric and magnetic fields. An electromagnetic wave requires no medium for propagation; that is, it can travel in a vacuum as well as through matter. In the simplified diagram in Figure 1.1, the wavelength of an electromagnetic wave is depicted as the distance between the adjacent crests of the oscillating fields. The wave is moving from left to right in the diagram.

Figure 1.1 Simplified diagram of an electromagnetic wave.

The constant speed c of electromagnetic radiation in a vacuum is the product of the frequency ν and the wavelength λ of the electromagnetic wave,

(1.1)

Often it is convenient to assign wavelike properties to electromagnetic energy. At other times, it is useful to regard these radiations as discrete bundles of energy-termed photons or quanta. The two interpretations of electromagnetic radiation are united by the equation

(1.2)

where E represents the energy of a photon and ν represents the frequency of the electromagnetic wave. The symbol h represents Planck's constant, 6.62 × 10⁻³⁴ J s.

From Eq. (1.1),

(1.3)

and the photon energy may therefore be written as

(1.4)

Using this equation, the energy in units of kiloelectron volts (keV) of a photon of wavelength λ in nanometers (nm) may be computed by

(1.5)

Electromagnetic waves ranging in energy from a few nanoelectron volts up to the order of a gigaelectron volt make up the electromagnetic spectrum in Table 1.1 (definition of electron volt can be found in Section 1.2.2.3).

Table 1.1 Generally accepted ranges for the electromagnetic spectrum

Designation	Frequency (Hz)	Wavelength (m)	Energy (eV)
γ-rays	10^18 to 10^21	3 × 10^−10 to 3 × 10^−13	4 × 10^3 to 4 × 10^6
X-rays	10^15 to 10^25	3 × 10^−7 to 3 × 10^−17	10 to 4 × 10^10
Ultraviolet	10^15 to 10^17	3 × 10^−7 to 3 × 10^−9	4–400
Visible	4 × 10^14 to 7 × 10^14	7.5 × 10^−7 to 4.3 × 10^−7	1.7–2.9
Infrared	10^11 to 4 × 10^14	0.003 to 7.5 × 10^−7	4 × 10^−4 to 1.7
Radar and microwave	10^8 to 10^11	3 to 0.003	4 × 10^−7 to 4 × 10^−4
Television	3 × 10^7 to 3 × 10^9	30 to 0.3	4 × 10^−8 to 4 × 10^−6
FM radio	8.8 × 10^6 to 1.08 × 10^8	34 to 2.8	3.6 × 10^−8 to 4.4 × 10^−7
AM radio	5.35 × 10^5 to 1.605 × 10^6	5.61 × 10^2 to 2.8 × 10^2	2.2 × 10^−9 to 4.4 × 10^−9
Electric power	0 to 10^3	0 to 3 × 10^5	0 to 4 × 10^−12

Note that the range of values for many designations overlap and are not universally defined.

1.2.1 The At...