MEDICAL PHYSICS ABR ACTUAL QUESTIONS AND CORRECT ANSWERS COMPLETE RADIOLOGICAL SCIENCE STUDY GUIDE

MEDICAL PHYSICS ABR ACTUAL
QUESTIONS AND CORRECT ANSWERS
COMPLETE RADIOLOGICAL SCIENCE
STUDY GUIDE

●● Scatter at 1m from a phantom is what fraction of the primary beam?
Answer: 1/1000


●● As SSD increases, PDD (increases or decreases) due to what?
Answer: increases due to inverse square


●● what is the maximum energy of lateral scatter from a photon beam?
Answer: 0.511 MeV


●● What is the maximum energy backscattered from a photon beam?
Answer: 0.255 MeV


●● What is the relationship between the photoelectric effect and Z?
Answer: Proportional to Z^3


●● How is the Compton effect dependent on Z?

,Answer: Independent of Z, only dependent on electron density


●● What is the relationship between pair production and Z?
Answer: proportional to Zln(E)


●● What isodose line is SRS therapy prescribed to for LINAC based
treatments?
Answer: 70% isodose line


●● What isodose line is SRS therapy using gamma knife prescribed to?
Answer: 50%


●● How much of the central axis dose do physical and dynamic wedges
scatter?
Answer: physical- 2.5%<br>Dynamic- 1.0%


●● Are electron beams a spectrum or mono energetic?
Answer: monoenergetic


●● What is the therapeutic depth for electrons?
Answer: R80


●● What is the occupational limit for 1 year?

,Answer: 50 mSv


●● What is the occupational limit for a pregnant radiation worker over
the duration of their pregnancy?
Answer: 5 mSv


●● What is the dose limit to the public in 1 year?
Answer: 1 mSv


●● At what energy do neutrons need to be accounted for in shielding
calculations?
Answer: 10 MV


●● What is the approximate energy of neutrons produced in photo
nuclear interactions?
Answer: 2 MeV


●● What is the limit for leakage?
Answer: 1/1000 of central beam axis value


●● What energy are neutrons at the entrance of the vault?
Answer: 100 keV this is the most dangerous because Wr=20

, ●● What is the average radiation exposure to someone in the US?
Answer: 4-5 mSv / Year&nbsp;<br>


●● What are the sources of background radiation exposure in the US?
(5)
Answer: Medical, Radon, ingested isotopes, isotopes occurring naturally,
and cosmic rays


●● What is the k-edge of lead?
Answer: 88 keV


●● What is the k-edge of iodine?
Answer: 33 keV


●● What is the increase in mortality risk due to an acute radiation
exposure?
Answer: 8% per Sv


●● What is the increase in mortality risk due to an chronic radiation
exposure?
Answer: 4% per Sv


●● At what dose does hematopoietic syndrome start to occur?