Ch 4 Flashcards
(27 cards)
The half value layer of a superficial beam is between:
A. 0-1 mm Al
B. 1-10 mm Al
C. 10-30 mm Al
D. 30-50 mm Al
B. 1-10 mm Al
In orthovoltage therapy, 90% of the dose occurs at an approximate depth of:
A. 0.5 cm
B. 1.0 cm
C. 2.0 cm
D. 5.0 cm
C. 2.0 cm
The output of a cobalt-60 therapy source decreases each month by about:
A. 0.1%
B. 1.0%
C. 2.0%
D. 5.0%
B. 1.0%
Which of the following is not an accelerator component:
A. waveguide
B. transducer
C. circulator
D. modulator
E. thyratron
B. transducer
In a linear accelerator, the flattening filter is used to:
A. flatten the front end of the accelerator head
B. make the beam intensity uniform
C. produce electron beams
D. filter the neutrons from the beam
B. make the beam intensity uniform
Superficial machines operate between:
A. 10-20 kV
B. 20-50 kV
C. 50-150 kV
D. 150-400 kV
C. 50-150 kV
Superficial machines are useful for treating tumors confined to:
A. 0-5 mm
B. 0-10 mm
C. 0-20 mm
D. 0-30 mm
A. 0-5 mm
Typical SSD for superficial units is :
A. 5-15 cm
B. 15-20 cm
C. 20-30 cm
D. 30-50 cm
B. 15-20 cm
Orthovoltage therapy is delivered with x-rays produced by potentials ranging from:
A. 50-100 kV
B. 100-150 kV
C. 150-500 kV
D. 500-660 kV
C. 150-500 kV
Orthovoltage beams have a half value layer in the range of:
A. 1-3 mm Al
B. 3-5 mm Al
C. 1-4 mm Cu
D. 1-2 mm W
C. 1-4 mm Cu
The greatest limitation of the orthovoltage beams for treating deeper tumors is:
A. Low dose rate
B. High skin dose
C. Poor penumbra
D. Unstable dose rate
B. High skin dose
The f-factor for soft tissue for an orthovoltage beam is typically:
A. About unity
B. About 3
C. About 10
D. None of the above
A. About unity
Cobalt-60 therapy machines produce photon beam energies of:
A. 1-1.33 MeV
B. 1.17 and 1.33 MeV
C. 1.25 MeV
D. 1.17 MeV
B. 1.17 and 1.33 MeV
A cobalt-60 therapy source usually has a diameter of:
A. 1-3 mm
B. 3-5 mm
C. 5-10 mm
D. 10-20 mm
D. 10-20 mm
The penumbra at 80 cm SSD from a 2 cm diameter Cobalt-60 source collimated at 40
cm from the source is:
A. 0.5 cm
B. 1.0 cm
C. 2.0 cm
D. 4.0 cm
C. 2.0 cm
The half value thickness (HVT) for a cobalt-60 beam is:
A. 10 mm Al
B. 10 mm Cu
C. 12 mm Pb
D. 12 mm W
C. 12 mm Pb
The transmission of a cobalt-60 beam through a 6 cm thick lead block is about:
A. 25%
B. 10%
C. 7.5%
D. 3.1%
D. 3.1%
Special collimation used to reduce the penumbra from a cobalt-60 unit is called:
A. Cheater block
B. Multileaf system
C. Trimmers
D. None of the above
C. Trimmers
In order to accelerate electrons, linear accelerators use:
A. Ultrasound waves
B. Electromagnetic waves
C. Ultraviolet rays
D. Low energy rays
B. Electromagnetic waves
The frequency of electromagnetic waves typically used in linear accelerators to
accelerate electrons is:
A. 3 kHz
B. 30 MHz
C. 300 MHz
D. 3000 MHz
E. 3000 GHz
D. 3000 MHz
In a standing wave accelerator, the energy gained by an electron is approximately:
A. 10 keV/cm
B. 20 keV/cm
C. 75 keV/cm
D. 150 keV/cm
D. 150 keV/cm
The sources of accelerating power in a linear accelerator are:
A. Thyratron and electron gun
B. Klystron and magnetron
C. Magnetron and electron gun
D. Buncher and pre-buncher
B. Klystron and magnetron
A magnetron in a 4-6 MV linear accelerator typically operates at a peak power of:
A. 0.5 MW
B. 1.0 MW
C. 2.0 MW
D. 2.5 MW
E. 3.0 MW
C. 2.0 MW
Typical Klystron used in high energy linear accelerators (10-25 MeV) operates at a peak power of:
A. 1.0 MW
B. 2.0 MW
C. 3.0 MW
D. 5.0 MW
E. 10.0 MW
D. 5.0 MW
