WorksheetsTherapy Medical Physics
Total questions: 22
Worksheet time: 33mins
Name
Class
Date
1.
A radionuclide has an initial dose rate of 4.1 cGy/hr will deliver a cumulative dose of 8,500 cGy over its life. What is the radionuclide?
a)
Pd-103
b)
Ir-192
c)
Co-60
d)
Iodine-125
2.
I-125 has a half-life of 59.4 days. By how much does activity decline in 1 day?
a)
2.4%
b)
1.8%
c)
0.8%
d)
1.2%
3.
Accurate proton dose calculation requires knowledge of what?
a)
Tissue electron density
b)
Tissue stopping power
c)
Tissue linear attenuation coefficient
d)
Tissue physical density
4.
What device provides the oscillating electromagnetic wave used to propel electrons down the linac accelerating waveguide?
a)
Thyratron
b)
Magnetron
c)
Betatron
d)
Half-wave rectifier
5.
Which of the following is not an advantage of HDR afterloading?
a)
Out patient procedures
b)
Ability to optimize dose distributions
c)
Reduced dose to staff
d)
Less QA required
6.
True or false: BSF is independent of SSD.
a)
True
b)
False
7.
What is the radius of an circular field equivalent to a 5cm by 6cm field?
a)
3.1cm
b)
2.8cm
c)
5.5cm
d)
1.7cm
8.
Physical penumbra is typically defined as the lateral distance between what two isodose lines?
a)
66.7% and 33.3%
b)
80% and 20%
c)
80% and 50% (FWHM)
d)
90% and 10%
9.
A sample of Au-198 has an initial activity of 8Ci. What is its activity after 14 days?
a)
5.7 x 10^8 Bq
b)
3.4 x 10^8 Bq
c)
8.1 x 10^9 Bq
d)
7.4 x 10^10 Bq
10.
What energy electron beam would you select to treat to the 80% isodose line at a depth of 3cm?
a)
9 MeV
b)
6 MeV
c)
15 MeV
d)
12 MeV
11.
What is the primary advantage of proton treatments compared with photon treatments?
a)
Plans are less impacted by changes in patient anatomy
b)
Higher RBE
c)
Plans are less impacted by changes in patient positioning
d)
Reduced integral dose
12.
What is the function of SF6 gas used in a linear accelerator?
a)
To cool the anode/target via evaporation.wrong
b)
To maintain sufficient magnetron pressure for normal operation.
c)
To prevent premature accelerating waveguide wear.
d)
To prevent electrical arcing in the waveguide
13.
An I-125 seed (half life = 59.4 days) delivers an initial dose rate of 2.4cGy/hr to its reference point. What is the cumulative dose delivered after 30 days?
a)
1460 cGy
b)
12.9 Gy
c)
1724 cGy
d)
15.4 Gy
14.
An eye plaque procedure calls for I-125 seeds which arrive and are surveyed 4 days prior to the procedure. During the survey, the physicist's ion chamber measures 38.6pA for a 25 seed magazine. The chamber's calibration factor is 2.5 x 1011 U/A and a correction factor of 1.5. What will the activity of the seeds be on the day of the procedure?
a)
0.68 U/seed
b)
16.21 U/seed
c)
0.55 U/seed
d)
1.62 U/seed
15.
Compute the MU required to deliver 200cGy/fraction to the 90% isodose line of a 12MeV electron field at SSD = 100cm and using a 95cm2 cutout in a 10x10cm2 cone. Assume an output factor for this cone/insert combination of 0.947.
a)
207MU
b)
217MU
c)
197MU
d)
220MU
e)
235MU
16.
What is the dmax (depth of maximum dose) for kV photons?
a)
Surface
b)
5mm
c)
3mm
d)
9mm
17.
Which factors increase surface dose? (Select all that apply)
a)
Removal of flattening filter (FFF beam)
b)
Use of bolus
c)
Increasing field size
d)
Decreased angle of incidence
18.
What is the primary benefit of IGRT?
a)
Reduced treatment time
b)
Reduced treatment volumes
c)
Increased margin size
d)
Improved plan homogeneity
e)
Reduced plan hotspots
19.
Which factors influence the depth of maximum dose for a photon field? (Select all that apply)
a)
Source size
b)
SSD
c)
Field Size
d)
Use of Jaw vs MLC collimation
20.
How many monitor units are required to deliver 99cGy to the isocenter of a wedged field (transmission factor = 0.84) for a TMR of 0.75 and an output factor of 1.02cGy/MU?
a)
133MU
b)
99MU
c)
154MU
d)
160MU
e)
148MU
21.
Most MeV proton interactions with the nucleus are:
a)
Elastic
b)
Inelastic
22.
Calculate the geometric penumbra of a 2mm source at a distant of 100cm from the source assuming a source-to-collimator distance of 30cm.
a)
1.2mm
b)
4.5mm
c)
8.1mm
d)
6.7mm
100 %
