4. Neutron therapy is not pursued widely because: a) Neutrons have too low OER b
ID: 253212 • Letter: 4
Question
4. Neutron therapy is not pursued widely because:
a) Neutrons have too low OER
b) Neutrons do not kill tumor cells efficiently enough
c) Neutrons do not have high enough LET
d) Neutrons cause too much normal tissue damage
5. Nuclei of which element are used for neutron capture therapy:
a) Bismuth
b) Boron
c) Beryllium
d) Bromine
6. How can the narrow Bragg Peak can be turned into the Spread-Out Bragg Peak (SOBP)?
a) By applying filters of varying thickness to modify proton beam energy
b) By moving the patient (i.e. varying the source to surface distance)
c) By mixing proton and neutron beams
d) By mixing proton and electron beams
7. Why is proton beam therapy is currently gaining popularity?
a) Because of the very high RBE
b) Because the very high OER
c) Because of the better sparing of normal tissues
d) Because of the low cost of the new generation proton accelerators
8. Advantages of carbon ion therapy over proton therapy include:
a) Sharper radiation field edges laterally
b) Fragmentation which leads to a better dose coverage
c) Lower OER – better for treating hypoxic tumors
d) Both a and c
9. Which of the following statements is NOT true about carbon ion therapy?
a)
b)
c) Hypo-fractionation cannot be used with carbon ions
d) There is a possibility of imaging with PET
10. Overall, carbon ions offer superior dose distribution characteristics as compared to protons
a) true
b) false
Radiation Protection
11. The unit of equivalent dose is called
a) Sv
b) Roentgen
c) Gy
d) rad
12. Of the following types of ionizing radiation which has the highest quality factor?
a) electrons
b) protons
c) thermal (low energy) neutrons
d) alpha particles
13. Which of the following statements is true with respect to stochastic effects of ionizing radiation?
a) There is no threshold dose but the severity of these effects increases with dose
b) There is no threshold dose and the probability of their occurrence increases with dose
c) There is a threshold dose and the severity increases with dose
d) There is a threshold dose and the probability of their occurrence decreases with dose
14. Our current best estimate for the probability of radiation induced fatal cancer in adult population per unit effective dose is approximately
a) 4%/Sv
b) 50 %/Sv
c) 1%/Sv
d) 4%/mSv
15. The annual effective dose due to natural background in North America is approximately:
a) 1 Sv
b) 30 mSv
c) 0.1 mSv
d) 2 mSv
16. Which of the following diagnostic X-ray examinations involves the highest effective dose?
a) Chest X-ray
b) CT scan
c) Mammography X-ray
d) Dental bitewing X-ray
17. (3 marks) During his last mission (Dec. 2012 – May 2013) Chris Hadfield spent 145 days in space. Assuming that the effective dose rate in space in ~1.5mSv/day, what is the best estimate for the resulting risk of the commander acquiring a fatal cancer from this radiation exposure?
a) 10%
b) 1%
c) 50%
d) 0.05%
18. Which of the following statements is true in regard to the risk of severe mental challenge resulting from radiation exposure during prenatal human fetus development:
a) The risk is uniform (constant) throughout pregnancy
b) The risk is highest during the first 5 weeks post conception
c) The risk is highest at weeks 8-15 post conception
d) The risk is the lowest at weeks 8-15 post conception
19. What is the recommended effective dose limit for general public according to the ICRP and 103 reports?
a) 0.1 mSv per year
b) 20 mSv per year
c) 1 mSv per year
d) 50 mSv per year
20. The ALARA principle calls for radiation exposure resulting from industrial, medical and other human activities to be:
a) As low as we can make it
b) Low but never below the natural background
c) Not more than twice the natural background
d) as low as reasonable achievable
21. CNSC regulations apply to:
a) All radiation sources and devices in a radiotherapy department
b) All radioactive sources and high energy radiation emitting devices
c) only to linear accelerators and with particle energies above 10 MeV and nothing else
d) Only to sources and devices used for treatment and not for imaging purposes
22. According to CNSC regulations the annual dose limit for Nuclear Energy Workers is:
a) 50 mSv
b) 1 mSv
c) 4 mSv
d) 5 mSv
23. According to Ontario’s HARP Act Regulation 543 the weekly effective dose limit for general public is:
a) 1 mSv/week
b) 0.02 mSv/week
c) 2 mSv/week
d) 0.1 mSv/week
24. A medical physicist is designing shielding required for a new medical linear accelerator with the maximum photon beam energy of 15 MV. The design should take into consideration:
a) Only the primary photon beam
b) Primary, scatter, leakage and neutron contaminations
c) Primary, scatter, and leakage radiation
d) Primary and scatter only
25. The thickness of concrete in the primary barrier is 2.4 m. The TVL in concrete for a 10 MV photon beam is approximately 40 cm. What will be the transmission coefficient through the barrier?
a) 0.001
b) 1/6
c) 0.000001
d) 0.0006
26. Last Person Out button is part of which safety system in a radiation treatment room?
a) Warning lights – it turns on a warning light
b) Emergency off button – it turns off the radiation treatment machine
c) Machine locks – it unlocks the machine so the it can be operated
d) Door interlocks – it resets the door interlock system so that irradiation is enabled if all door interlocks are cleared within a predefined time.
28. Radiation dose rate varies with the distance (d) from the source as:
a) 1/d
b) d2
c) 1/d2
d) e-d
30. Which of the following situations on an HDR unit is NOT an emergency?
a) Stuck iridium-192 source that did not return to safe after treatment
b) HDR source lost in transport
c) Planned source replacement
d) Radioactive source damaged and leaking radioactive material
Clinical Radiobiology – Dose Fractionation
31. For mammalian cells in culture, the approximate time required for the repair of radiation induced sub-lethal damage (SLD) is in the order of:
a) 2 hours
b) 8 hours
c) 24 hours
d) 48 hours
32.
33. The D0 of cell line A is 100 cGy and cell line B is 150 cGy, the percentage of cells killed in cell line A after exposure to radiation will be:
a) Higher than in cell line B
b) Lower than in cell line B
c) the same as in cell line B
d) Not conclusive
34. The most resistant phase of the cell cycle to radiation damage is:
a) G1
b) S-phase
c) G2
d) Mitosis
35. A basic assumption in modeling of radiation responses is the lethal ionizing events are:
a) random event occurring in cell nuclei
b) Random events in space as defined by the Poisson distribution
c) A Gaussian distribution
d) Logarithmic dose response curves
36. Late responding normal tissues are more sensitive to change in fractionation that early responding tissues, because:
a) The cell survival curve of late responding tissues has a broader shoulder than early responding tissues
b) Late responding tissues are more sensitive to radiation damage than early responding tissues
c) Late responding tissues are more responsive to radiation damage than early responding tissues
d) Early responding tissues have a special tissue architecture that enables the tissues to repair radiation damage
37. Which parameter in the IQ model contributes most to cell killing in standard clinical fractionated regimens in Radiation Therapy?
a) Alpha/Beta ratio
b) D0
c) Alpha
d) Beta
38. For mammalian cells in culture, the approximate time required for the repair of radiation induced potentially lethal damage (PLD) is in the order of:
a) 4 hours
b) 6 hours
c) 12 hours
d) 24 hours
39. Which of the following human tumours has recently been thought to have an alpha/beta ratio of 1-2 Gy?
a) Oropharyngeal
b) Prostate
c) Glioblastoma
d) Colorectal
40. If tissue tolerance is 60 Gy at 2 Gy/fraction and 40 Gy at 4 Gy/fraction, what is its alpha/beta ratio?
a) 1 Gy
b) 2 Gy
c) 4 Gy
d) 10 Gy
41. It is decided to treat a patient with hypo-fractionation at 3 Gy/fraction instead of the conventional schedule of 60 Gy in 2 Gy fractions. What total dose should be delivered in order for the risk of late normal-damage to remain unchanged, assuming an alpha/beta ratio for late damage of 3 Gy?
a) 40 Gy
b) 48 Gy
c) 50 Gy
d) 55.4 Gy
42. Hyper-fractionation using a fraction size of 1.2 Gy is replacing a standard 70 Gy in 2 Gy fractions for HNSCC. Assume full repair of sub-lethal damage between fractions and an alpha/beta ratio of 3 Gy. What total dose should be used to maintain the same level of late complications?
a) 42 Gy
b) 58 Gy
c) 70 Gy
d) 83 Gy
43. Which of the following sites is the least suitable for b.i.d treatment?
a) Head and Neck
b) Brain
c) Lung
d) Prostate
44. The rationale behind accelerated fractionation is:
a) To spare late responding normal tissue
b) To combat encourage tumor re-oxygenation
c) to exploit redistribution in tumors
d) To combat accelerated repopulation in tumors
In Q45 and Q46: Assume full repair of sub-lethal damage between fractions and no significant repopulation of tumor cells throughout the whole course of treatment.
45. (3 marks) A patient was to receive radiation treatment of 2000 cGy in 10 daily fractions. Due to documentation error, 600 cGy was delivered in the first 6 daily treatments. What will be the total dose to be delivered in the next 7 treatment days (in equal fractions) that will give the same overall biological dose to the tumor?
46. (3 marks) A breast patient was originally planned to receive a total dose of 4256 cGy in 16 daily fractions. However, after 6 fractions into the treatment, the Oncologist wants to deliver the rest of the treatment in 2 Gy fractions. What will be the new schedule (i.e. the total dose, the total number of fraction and the size of dose fraction for the new schedule) that will maintain the same overall biological dose to the tumor?
Explanation / Answer
Ans 4 :d) Neutrons cause too much normal tissue damage
In 1938 , The neutron therapy was first introduced by Stone et al. The therapy is very effective , as it can control very large tumors, which are radioresistant.
But the major disadvantage of the therapy being one is that it causes a lot a normal tissue damage , due to which it cannot be used widely.
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