This document provides an overview of an imaging course covering x-ray imaging, computed tomography, nuclear medicine techniques, and radiotherapy. It outlines the course content, evaluation methods, reference materials, and introduces key concepts in atomic structure, the nature of light, and interactions between photons and matter. Specifically, it describes how x-rays are produced in imaging tubes, how they interact with the body to create images, and considerations for both diagnostic and therapeutic uses of x-rays.

1. Medical Equipment II
X-ray Imaging
Inas A. Yassine
Associate Professor,
Systems and Biomedical Engineering Department,
Faculty of Engineering - Cairo University
iyassine@eng.cu.edu.eg

2. Course Content
§ Imaging
§ X-Ray Imaging
§ Computer Tomography (CT)
§ Nuclear Medicine
§ Positron Emission Tomography (PET)
§ Single Positron Emission Computer Tomography (SPECT)
§ Radiotherapy
§ X-ray
§ LINear ACcelerator (LINAC)
§ Cobalt
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3. Student Evaluation and grading
§ 30% Class work
§ Midterm
§ Study Report
§ Homeworks
§ 70% Term Exam
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4. Reference Books:
§ Russell K. Hobbie, Bradley J. Roth "Intermediate
Physics and Biology (Chapter 14, 15), Springer,
2007."
§ N. Smith et.Al., "Introduction to Medical Imaging
Physics, Engineering and Clinical Applications“.
2011.
§ P. Mayles et.al.,"Handbook of Radiotherapy
Physics:Theory and Practice", 2007.

5. Introduction to Atoms and Light
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6. Nature of light
§ Light travels in a vacuum with a velocity c = 3
×108 m/s
§ When light travels through matter, its speed is less
than this and is given by
n is index of refraction of substance
§ depends on both the composition of substance
and color of light
n
c
cn =

7. Nature of light
§ A traveling wave of light can be described by f(x −
cnt)
represents a disturbance traveling along the x axis in the
positive direction
§ If wave is sinusoidal, then the period ,T,
frequency,γ , and wavelength, λ, are related by
ln== C
T
c ,
1

8. Nature of light
§ As light moves from one medium into
another where it travels with a different
speed, frequency remains the same.
§ Wavelength changes as the speed changes.
§ Each particle of light or photon has energy
E given by:

9. Nature of light

10. Atomic Energy
§ Energy level: isolated atoms have specific
discrete internal energies
§ An atom can change from one energy level
to another by emitting or absorbing a
photon with an energy equal to the energy
difference between the levels

11. Atomic Energy Levels
§ Let the energy levels be labeled the energy of the
ith state being Ei.
§ The lowest possible internal energy for each atom
when the atom is in this state, no further energy
loss can take place.
§ If Ei is greater than the lowest energy, then the
atom can lose energy by emitting a photon of
energy Ei −Ef and exist in a lower
energy state Ef

12. Atomic energy Levels
§ Ionization energy is the smallest amount of energy
required to remove an electron from the atom when the
atom is in its ground state.
Radiation
Ionizing
Non-
Ionizing
Direct Indirect §Microwaves
§Radiofrequency
§Ultrasound
§Infrared

13. Atomic Energy Level
§ An atom
§ can receive energy from an external source, such as
a collision with another atom or some other
particle.
§ Can absorb a photon of the proper energy.
§ Allows one of its electrons to move to a higher
energy level, as long as that level is not already
occupied.
§ Can get rid of excess energy by emitting a photon

14. Atomic Energy levels
§ Energy levels given as

15. Scattering and Absorption of
Radiation
§ Photons in a vacuum travel in a straight line.
§ When they travel through matter
§ are apparently slowed down (n>1)
§ May be scattered or absorbed
§ Visible light does not pass through walls
§ The beam shape is fanning near by the source.
§ At a distant source of photons that travel in straight lines, to
form a nearly parallel beam of photons

16. Photon Interaction with matter
§ Passing through
§ Scattering
§ Absorption

17. Photon Interaction with matter
§ Assume N photons passing through a thin layer of
material dz
§ μ is the total linear attenuation coefficient.
§ μs and μa are linear scattering and absorption
coefficients

18. Imaging tool Full Definition
§ Effect produced
§ Interaction with the body
§ Effect to be Detected
§ Image Construction

19. X-Rays Imaging
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Yassine 19

20. X-ray Imaging
§ The tube – X-rays are produced
§ The body – X-rays interact with the body
§ The image – X-rays interact with film,
Detectors
§ Film processing, Signal analysis

21. Diagnostic and Therapeutic X-Ray
§ Diagnostic radiology
§ uses low energy X rays for imaging
§ No Tissue Damage Reversible
§ Effect Detection
§ Max Dose calculation
§ Radiotherapy
§ uses high energy X rays to treat tumor.
§ ionizes the water in the cell and induces formation of free
radicals which can damage of genetic material (DNA).
§ Normal cells are also affected adversely by radiation but have
the capacity of repair. reversible.

22. X-rays
§ Made of photons
§ Travel at speed of light
§ Travels in a straight line
§ Has no mass nor charge (cannot be focused by
magnets)
§ X-ray beam has a mix of energies
§ Diagnostic X-ray range 20-150 kVp

23. The X-ray tube

24. X-ray tube

25. X-ray production
§ Push the “rotor” or
“prep” button
§ Charges the filament –
causes thermionic
emission (e- cloud)
§ Begins rotating the
anode.
§ Push the “exposure” or
“x-ray” button
§ e-’s move toward anode
target to produce x-rays

26. Coverage Calculation
𝑓 = 𝐹𝑠𝑖𝑛 𝜃
where 𝜃 is the bevel angle and F the width of
the electron beam
𝐶𝑜𝑣𝑒𝑟𝑎𝑔𝑒
= 2 𝑠𝑜𝑢𝑟𝑐𝑒 − 𝑝𝑎𝑡𝑖𝑒𝑛𝑡 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ∗ 𝑡𝑎𝑛 𝜃

27. Coverage

28. Anode Heel Effect

29. Energy Spectrum of X-ray

30. Exposure Factors:
§ kVp – kilovoltage peak
§ mA – miliamps (current)
§ s – seconds (duration of exposure)
§ mAs – product of mA and s
Exposure factors are set by
radiographer