Practice and Review Exam: 139   ::

Description: Medical Physics
Faculty: James G. Smirniotopoulos, M.D.

1) Physicians should consider which of the following actions to keep diagnostic radiation doses to their patients as low as reasonable achieveable?

1. Ensure that their patients are not irradiated unjustifiably. 
2. Carefully weigh the medical benefits when ordering a particular radiographic modality against the potential biological risks from radiation exposure. 
3. Consult clinical guidelines advising which radiographic examinations are appropriate for their patients. 
4. Consider if the required medical information can be obtained from modalities that do not emit ionizing radiation (MRI and ultrasound). 
5. All of the above answers 

2) Mammalian cells are not equally radiosensitive. Which of the following are examples of least radiosensitive cells?

1. Hematopoietic stem cells 
2. Muscle 
3. Lymphocytes 
4. Endothelial 
5. Answers b and d above 

3) Mammalian cells are not equally radiosensitive. Which of the following are examples of more radiosensitive cells?

1. Lymphocytes 
2. Spermatogonia 
3. Nerve 
4. Muscle 
5. Answers a and b above 

4) In 1906, J. Bergonie and L. Tribondeau noted that the most radiosensitive cells are those cells with _________.

1. a high division rate. 
2. a long dividing future. 
3. unspecialized types (stem cells). 
4. answers a and b above 
5. all of the above answers 

5) Ionizing radiation can cause damage to cells by ____.

1. Ionization of cellular molecules 
2. Creation of free radicals 
3. Ionization of atoms 
4. All of the above 

6) A Radiation Safety Officer completes an x-ray survey on a diagnostic x-ray machine. He measures the Half Value Layer (HVL) at 80 kVp to be 2.7 mm Al powered by a high frequency generator using narrow beam geometry. The HVL would be _______ if measured on the same x-ray machine at 70 kVp.

1. less than 2.7 mm Al 
2. more than 2.7 mm Al 
3. be the same HVL (2.7 mm Al) 

7) The line focus principle allows the focal spot to effectively appear small while distributing the heat of the electron flux across the target.

1. True 
2. False 
3. Cannot be determined from the provided information 

8) Which of the following does NOT increase when filtration is added to an x-ray beam?

1. Half value layer 
2. Average x-ray beam energy 
3. Exposure measurements 
4. None of the above 

9) Which of the following would NOT change as the kVp of an x-ray tube is increased, with all other factors held constant?

1. Half value layer 
2. Filtration 
3. Penetration 
4. Skin dose 
5. None of the above 

10) An electron accelerated through a potential difference (voltage) of 120,000 volts attains a kinetic energy of 120keV.

1. True 
2. False 
3. Cannot be determined from the provided information 

11) Which of the following types of photon interactions with matter is dominant in the photon energy range of diagnostic imaging?

1. Photoelectric effect 
2. Compton Scatter 
3. Pair Production  
4. Photodisintegration 
5. None of the above 

12) Increasing an x-ray tube's voltage (kVp) will NOT increase __________.

1. the x-ray beam intensity. 
2. the beam's half value layer. 
3. the beam's filtration. 
4. heat produced in the anode. 

13) A collimator measuring tool is used when surveying radiographic units to _______________.

1. test the light field compared to the x-ray field. 
2. measure the source-to-detector distance. 
3. determine the radiation intensity in the center of the x-ray beam. 
4. measure the focal spot size. 

14) Why are x-ray beams filtered?

1. To remove dangerous, high-energy photons. 
2. To decrease the half value layer. 
3. To reduce a patient's skin dose. 
4. Both a and b above 
5. None of the above 

15) Absorbed dose is the amount of ________ deposited by ionizing radiation per unit mass of ______.

1. charge / air 
2. energy / air 
3. charge / any material 
4. energy / any material 

16) Radiation exposure is the amount of ________ liberated by ionizing radiation per unit mass of ______.

1. charge / air 
2. charge / any material 
3. energy / air 
4. energy / any material 

17) A photon is emitted when an orbital electron falls from the L shell to fill a vacancy in the K shell. This emitted photon is called a ____.

1. Bremsstrahlung x-ray 
2. Photoelectron 
3. Characteristic x-ray 
4. Photoelectric photon 
5. None of the above 

18) Which of the following is the most descriptive difference between x-rays and gamma rays?

1. Energy 
2. Velocity 
3. Wavelength 
4. Origin 
5. Both c and d above 

19) If an exposure of 40 mR was measured at 40 inches, according to the Inverse Square Law, what would that exposure be at 10 inches?

1. 80 mR 
2. 160 mR 
3. 200 mR 
4. 440 mR 
5. 640 mR 

20) The line focus principle refers to the _______.

1. Fact that the electron beam is focused by a bias voltage applied to the focusing cup. 
2. Reduction in the effective focal spot length resulting from the anode angle. 
3. Effect that the line voltage has on the focal spot. 
4. Increase in the effective focal spot length resulting from the anode angle. 
5. None of the above 

21) Why is molybdenum used as a target material in mammography x-ray tube anodes instead of tungsten?

1. Molybdenum's high atomic number allows excellent Bremsstrahlung production. 
2. Molybdenum has a high melting point with good heat loading properties. 
3. Molybdenum produces lower energy x-rays which are better for imaging soft tissue. 
4. Both a and b above 
5. None of the above 

22) Why is tungsten used as a target material in the x-ray tube anode?

1. Tungsten's high atomic number allows production of Bremsstrahlung radiation. 
2. Tungsten has a high melting point which affords good heat loading properties. 
3. Both a and b above 
4. Neither a or b above 
5. Only a above 

23) Which of the following affect x-ray emission?

1. Target material and beam filtration. 
2. Tube voltage and current. 
3. Exposure time and generator waveform. 
4. All of the above 
5. Only a and b above 

24) When an orbital electron falls to a lower energy level, a photon may be emitted from the atom. This emitted photon is called _______.

1. A characteristic x-ray 
2. An Auger electron 
3. Bremsstrahlung 
4. A photoelectric photon 
5. None of the above 

25) A Radiation Safety Officer measures the Half Value Layer (HVL) of an x-ray machine. (Assume monoenergetic photons under narrow-beam geometry conditions.) He then adds more aluminum to reduce the exposure to 1/4 of the initial value. If the first HVL was 3 mm Al, the second HVL must be 2.5 mm Al.

1. True 
2. False 

26) Half value layer is __________.

1. The thickness of a material that amplifies half of the radiation beam. 
2. The thickness of a material that attenuates an incident radiation beam to half of the incident beam's intensity. 
3. Half of the thickness necessary to attenuate an incident radiation beam to its desired intensity. 
4. Half of the thickness necessary to amplify an incident radiation beam to its desired intensity. 
5. None of the above. 

27) A photon interaction in which the photon transforms into a positive and negative electron is called ________.

1. Photointegration  
2. Compton Effect 
3. Photoelectric Production 
4. Pair Production 

28) For Pair Production to occur, the incident photon must have initial energy of at least 1.022 Mev because that is the _______?

1. Required energy to overcome electrostatic forces produced by the heavy nucleus. 
2. Rest mass energy of the nucleus. 
3. Sum of the rest mass energy of two electrons. 
4. None of the above 

29) Secondary emmissions of Auger electrons or x-rays, or both, occur as a result of __________?

1. Outer orbital electrons filling vacancies created in lower energy orbitals by any interaction. 
2. Inner orbital electrons filling vacancies created in higher energy orbitals by the Photoelectric Effect. 
3. Inner orbital electrons filling vacancies created in higher energy orbitals by the Compton Effect. 
4. None of the above 

30) The Photoelectric Effect results in ________?

1. Scattered photons 
2. Scattered electrons 
3. Both a and b 
4. Neither a or b 

31) A photon interaction in which all of the photon's energy is transferred to an electron that is ejected from an atom is called _________?

1. Photodisintegration 
2. Coherent Scattering 
3. Compton Effect 
4. Photoelectric Effect 
5. Pair Production 

32) A photon interaction in which an orbital electron is ejected along with a photon of reduced energy is known as __________?

1. Photodisintegration 
2. Coherent Scattering 
3. Compton Effect 
4. Photoelectric Effect 
5. Pair Production 

33) Which of the following phenomena are photon interactions?

1. Photoelectric absorption 
2. Pair annihilation 
3. Photographic integration 
4. All of the above 

34) What is a photon?

1. A charged particle that causes an x-ray to be emitted from an atom. 
2. A unit of x-ray or gamma-ray energy according to the quantum model. 
3. A unit of measurement that is used to describe radiation. 
4. Another term for the electromagnetic spectrum. 

35) Regarding Plain Radiographs - which densities can be differentiated?

1. Metal > Bone > Muscle > Fat > Air 
2. Metal > Bone > Blood > Muscle > Fat > Air 
3. Bone > Blood > Muscle > Pus > Air 
4. Metal > Bone > Blood > Muscle > Air 
5. Metal > Bone > Calcium > Pizza > Donut > Air