1. Bremsstrahlung x-ray production increases as the atomic number of the target
increases as well. It is proportional to the square of the atomic number of the
target.
2. A sievert is the SI unit of the dose equivalent. Sievert (Sv) = absorbed dose (Gy) x
quality factor (QF).
3. CT simulation uses kV ranges and in kV ranges of photons, photoelectric effect is
the most common photon interactions.
4. Therapeutic ratio = normal tissue tolerance/tumor lethal dose = 10/8 = 1.25
5. Sealed radioactive sources should be checked for leaks at least every 6 months
according to the NRC.
6. Examples of microorganisms that can cause infections are: fungi, viruses,
protozoans, and bacteria.
7. Absorbed dose can be affected by beam quality (energy), field size (because of
scatter) and SSD (distance from source). Other factors may include depth and
tissue type. Air temperature does not affect absorbed dose specifically.
Temperature and pressure may affect beam output which would require a
correction factor.
8. Concrete and lead are most commonly used materials for shielding. Concrete is
more economical (aka: cheaper) when building a vault for shielding.
9. Exposure (Roentgen): measures the total number of ionizations produced by
photons and occur in a unit mass of air (C/kg).
10. Respiratory gating techniques can reduce tumor motion by delivering treatments
during one breath phase. A common technique seen is DIBH (deep inspiration
breath hold).
11. The doses limit for the hand of an occupational worker is 500 mSv or 50 rem.
12. Geiger-Muller Detector: a portable, handheld, survey meter of radiation. It is not
a dose measuring device and cannot distinguish between beam energies, but
rather measures a rate of radiation (mR/h or counts per minute cpm). GM
counter is used to survey rooms for radiation but doesn’t actually measure the
, amount of radiation. It is most commonly used to locate sources that have been
misplaced.
13. The skin of the testes/scrotum drains lymphatically to the inguinal and iliac
nodes.
14. When machines malfunction and you are unable to stop motion, immediately hit
the closest emergency off button to stop power to the machine and stop all
motion.
15. Feathering: is a technique used to “blur” this skin gap and further reduce hot or
cold spots. This is commonly seen in CSI treatments.
16. Anaphylaxis is a severe, life-threatening reaction to a drug allergy (including
contrast media). Signs and symptoms include tightening of airways, difficulty
breathing, nausea, abdominal cramps, vomiting, diarrhea, dizziness,
lightheadedness, weak, rapid pulse, decrease in blood pressure, seizure, and/or
loss of consciousness.
17. The useful range is found by dividing the energy by 2. In this case the beam
energy is 10 Mev/2 = 5 cm useful range.
18. Transmission factors describe how much of the beam is transmitted through the
device. If the factor is 0.91 this equates to 91%. 91% is transmitted and 9% is
attenuated.
19. The annual dose limit to the public for continuous or frequent exposure is 1 mSv
or 0.1 rem.
20. The inverse square law shows the relationship between distance and radiation
intensity. As distance increases, intensity is reduced by the inverse square of this
factor. As we increase distance by 2, intensity is reduced to a fourth.
21. Shielding requirements change depending on the rooms adjacent to the linac. If
the room is a controlled/restricted area, the dose limit is 0.1 rem/week or 1
mSv/week and 5 mSv/year.
22. Proper body mechanics include standing with feet shoulder width apart, weight
evenly distributed, with center of gravity at the pelvis when standing.
23. Activity is the rate of decay of the radioactive material. Activity also defines
source strength.
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