"Is affirmed"
At methodical session of the chair of medical
and biological physics
2007. The report №
chief of chair
Shaplavskij M.V.
Methodical instructions (indication)
for plan students self- preparation
“X-rays in medicine”
Module 3: Basic regularities of electromagnetism, atimic and nuclear physics.
Pithy module 9. Biophysics of ionizing radiation
Chernivtsi-2007
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Objective:.
Introduction:
Background:
1..
Basic question:
1.
Practical exercise:
1.
Final knolege and skills:
Students should know:
Students should be able:
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Contents of theme
1. Characteristic X-rays
2. X-ray interaction with matter
• Absorption
• Scattering
3. Cross-section
4. Physical Interaction Processes
• Photoelectric absorption (τ)
• Compton scattering (σ)
• Pair production (κ)
5. The photoelectric effect
6. The compton effect (Compton wavelength)
7. Раir production and annihilation
8. X-rays in a homogeneous target
9. Protection of the Patient in X-Ray Diagnosis
10.Diffraction of x-rays by crystals
Literature
1. Raymond A.Serway, Jerry S. Faughn Colloge physics, Fifth Edition.-Saunders
College Publishing.- 1999.-1029 p.
2. Marzeniuk V.P., Diduch V.D., Vakulenko D.V. et al. Biophysics and medical
informatics.- Ternopil: Ukrmedkniha, 2004.-480p.
3. Hugh D. Young, Roger A. Freedman University physics with modern physics,
11th edition.-Pearson education.-2004.-1714p.
4.Frank J. Blatt Modern Physics .-McGRAW-HILL, INC.-1992.- 517 p.
5. Methodical instructions (indication) for student’s preparation, lecture.
Questions for self-preparation of students:
1. Characteristic X-rays
2. X-ray interaction with matter
• Absorption
• Scattering
3. Cross-section
4. Physical Interaction Processes
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• Photoelectric absorption (τ)
• Compton scattering (σ)
• Pair production (κ)
5. The photoelectric effect
6. The compton effect (Compton wavelength)
7. Раir production and annihilation
8. X-rays in a homogeneous target
9. Protection of the Patient in X-Ray Diagnosis
10.Diffraction of x-rays by crystals
Tests.
1. Make up the expression for the shortest wavelength X-ray of braking radiation:
min
a.he 
 f .U 
d .times  



 b.hc  
  g.cU 
e
.
divide
  j.eU 
c.hce 


h – Planck constant, c – velocity of light, e – electron charge, U – potential
difference of of an x-ray tube.
2. The emitted x-ray photons have wavelengths in the range of:
a.0. 10 nm to 1 nm
b.0.11 nm to 1 nm
c.0.01 nm to 1 nm
d.0.01 nm to 10 nm
3.The Compton wavelength has a value of :
a. h/mec = 0.00234 nm.
b. h/mec = 0.00423 nm
c. h/mec = 0.00243 nm
d. h/mec = 0.00324 nm
Class independent work
As noted previously, x-rays are extremely penetrating. Between 1930 and
1950 an x-ray device called a fluoroscope was widely used in shoe stores to
examine the bones of the foot. Such devices are no longer in use because they are
now known to be health hazards, although physicians use similar devices to study
the skeletal structures of their patients. An x-ray photograph of a human hand is
shown in Figure 1.
Figure 1. X-ray
photograph of a
human hand.
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Protection of the Patient in X-Ray Diagnosis
The principles of protection of the patient in x-ray diagnosis as presented in
reports of national and international radiation-protection organizations have
undergone very little change over the years (NCRP, 1981b, 1982; Kramer and
Schnuer, 1992; ICRP, 1993c, 1996b). The first element in a program to protect the
patient is to maintain the x-ray machine in proper operating condition through a
continuing quality control program involving measurements of output, beam
quality, collimator performance, timer operation, and so on (BRH, 1974; Hendee
and Ritenour, 1992). The remaining elements are concerned with minimizing
patient dose without adversely affecting the objectives of the examination and
avoiding the taking of unnecessary x rays. The following recommendations are
basic to good practice in radiology from the viewpoint of radiation protection.
1. Minimize field size with accurate collimators. Do not expose parts of the
body that are not being examined. (An additional safety measure, but not a
substitute for adequate beam collimation, is to use leaded cloth or other shielding
material to protect the gonads and possibly other regions not being examined.) Use
film larger than the required x-ray field to verify that collimation is being done
properly.
2. Use maximum target-patient distance. This decreases the difference
between dose at the entrance side relative to the exit dose because of differences in
distances to the target. (As an example, it can be easily verified from the inverse
square law that when the x-ray film is 1 ft from the point where the beam enters the
body, the entrance dose for a 3 ft separation between the target and film is over 6
times the entrance dose for a 6 ft separation.)
3. Make sure that proper filtration is used.
4. Use a setting for the high voltage that will give minimum absorbed dose
consistent with a satisfactory picture.
5. Use the fastest film-screen combinations and shortest exposures that give
satisfactory results.
6. Pay careful attention to processing procedures to allow minimum exposures
(that is, by using full-strength developer, proper temperatures, and so on).
7. Use fluoroscopy only when radiography cannot give the required
information. Use image intensification in fluoroscopy.
8. Use all the planning necessary to prevent faulty pictures and the need for
retakes. Retakes are a major source of excessive x-ray exposure. Of all films that
need to be repeated, 50 percent are due to under- or overexposures (NCRP, 1989).
9. Do not prescribe the x ray unless it is necessary.
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