Ionising Radiation
The contrast of a CT image displayed on a monitor may be increased by:
Increasing the window width
Increasing the window level
Decreasing the window width
Decreasing the window level
Decreasing the window width
Decreasing the width of the “window” means restricting the range of grey scale displayed on the monitor screen (0โ255), to a more limited range of the available Hounsfield numbers (โ1000 for air to 3000 for dense bone). A lung window may be โ1250 to +250; a soft tissue window may be โ160 to +240; a bone window may be โ650 to +1350.
Decreasing the window width Decreasing the width of the “window” means restricting the range of grey scale displayed on the monitor screen (0โ255), to a more limited range of the available Hounsfield numbers (โ1000 for air to 3000 for dense bone). A lung window may be โ1250 to +250; a soft tissue window may be โ160 to +240; a bone window may be โ650 to +1350.
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Which anatomical plane is usually displayed in a CT scan?A. Transverse
B. Sagittal
C. Coronal
D. Longitudinal section
What are isotopes? Atoms of the one element whose nuclei:
A. Contain the same number of protons and neutrons
B. Have different numbers of protons
C. Have different numbers of neutrons
D. Do not have the optimum neutron to proton ratio
What does the “maximum permissible dose” of radiation (100 mSv/5 year period) refer to?
A. The average dose for the general population as a whole
B. The dose for an individual not exposed to radiation through their work
C. The dose allowed to people exposed to radiation through their work
D. The dose above which radiation is likely to cause harm to humans
Why are radionuclides that emit low-energy gamma radiation preferred than other radionuclides for in vivo diagnosis using a nuclear medicine technique? Because:
A. Other forms of radiation are emitted with too much energy.
B. High-energy gamma radiation is not penetrating enough.
C. Most of the radiation will emerge from the patient’s body.
D. Sources of x-rays require more extensive technical support than gamma sources.
The advantage of computed tomography (CT) over conventional radiography is:
A. CT delivers lower doses than conventional radiography.
B. CT images are faster to acquire than conventional radiographs.
C. CT produces a cross-sectional image that is not obscured by overlying anatomical structures.
D. CT projects a 3D structure onto a 2D image.
Which of the following absorbed radiation dose equivalents would cause the most harm to your body?
A. 0.05 sievert per year to the whole body for the human lifespan (75 years) = 3.75 Sv
B. 1 sievert (acutely) to the gonads only
C. 40 sievert (acutely) to the heart only
D. 7 sievert (acutely) to the whole body
Which one of the statements about the penetrating ability of radiation is true?
A. 750 keV gamma rays are more penetrating than 750 keV x-rays.
B. 140 keV gamma rays are more penetrating than 60 keV x-rays.
C. 2 MeV beta rays (electrons) are more penetrating than 1 MeV gamma rays.
D. 1 MeV gamma rays are more penetrating than 2 MeV x-rays.
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