Radiation Therapy Equipment and QA (Mosby Ch 6 Questions)
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*The protective housing around the cobalt source in the cobalt machine should allow transmission of ____% of the output.
*The source of electrons in the linac is the:
*Trimmer bars are attached to the collimator of the cobalt machine to reduce the effect of the:
*Calculate the width of the penumbra with an 80 cm SAD cobalt unit. Source diameter is 3.0 cm and the SDD is 40 cm. Treatment SSD is 75 cm.
*Calculate the width of the penumbra with an 80 cm SAD cobalt unit.
Source diameter is 2.0 cm and the SDD is 40 cm. Treatment SSD is 77 cm.
*The purpose of the flattening filter in the linac is to:
Evenly distribute the energy of the photon beam across a specified area
*What is the purpose of the magnetron and klystron in the linac?
They produce microwaves to accelerate electrons
*Trimmer bars attached to the cobalt collimator system should not be allowed closer than 15 cm from the patients skin. Why?
The trimmer bars and radiation produces secondary scatter. 15 cm is required to reduce the scatter to the patient.
As the distance from the source increases, the penumbra_____.
*As SSD increases, the penumbra_____.
*The target in the linac is typically made of ___.
*Why do we use tissue compensators and wedges instead of bolus to compensate for irregular contours?
Because they preserve skin-sparing
*Which radioisotope is used for bone mets?
*The field light on the linac is intended to represent the:
area of radiation exposure
*The scattering foil is used in the ___beam mode.
*The cyclotron may produce____beams.
*Energy range of early generation superficial therapy machines:
*The linc generates a high-energy photon or electron beam by:
accelerating charged particles in a linear path
*Geometric penumbra , characterictic of the cobalt beam increases with:
Increasing source size and increasing distance from the source
Half-life of Radium-226
*Half-life of Iodine-125
Half-life of Cesium-137
*Half-life of Gold-198
*the Fletcher's Suite application is an example of:
intracavitary LDR brachytherapy
*The important QA test(s) associated with the light field are(circle all that apply)
1)field size accuracy
3)light and radiation field coincidence
- 1)field size accuracy
- 2)beam output
- 3)light and radiation field coincidence
*The target to patient skin distance is measured using:
An ODI indicator
*The tolerance for the localizing laser and ODI is:
*The constancy of the linac, when compared with benchmark values established during commissioning must be within:
Output constancy for electron and photons must be checked____.
*The x-ray beam in a linac must exhibit flatness within about:
*Which out daily on the of the following checks must be carried out on the cobalt machine:
1)function of the radiation room monitor
- 1)function of the radiation room monitor
- 2)door inerlocks
- 3)beam output
- 4)timer error
*Full calibration and overhaul of treatment equipment must be carried out_____.
*Localizing lasers on simulators must be within ____of isocenter.
*Microwave power is directed towards the accelerator guide:
*Electrons are produced by the
*At the end of acceleration, high energy electrons are focused toward the collimator by the _____.
*The electron beam is spread out uniformly by the______.
*Monitors radiation output:
*Produces high voltage and high power electrical pulses to generate microwave power:
*Microwaves travel through these components and are prevented from reflecting backward:
waveguide, radiofrequency driver
*To check for accuracy of gantry digital readouts, one could use:
a spirit level at 45-degree angle increments
*The linear scales on the treatment table are useful for:
- daily treatment setup
- translation of patient positions from simulation to treatment
*which of the following verifies the accuracy of the treatment dose delivery:
backup timer, radiation off switch, door interlock, and emergency off switch
*The process for testing a new linac against manufacturer's specifications is called:
*Gantry and collimator indicators should be within ____degree(s).
*All of the following might account for a beam's flatness deviating outside of specifications, except for:
1)flattening filter shift
2)target position shift
3)Incorrect mirror angulation
4)Fluctuation of current
- 1)flattening filter shift
- 2)target position shift
- 3)Incorrect mirror angulation
- 4)Fluctuation of current
*A mechanical distance indicator is used to verify:
Accuracy of the optical distance indicator
*Which of the following has the shortest half-life?
*Superficial treatment machines used short treatment distances because:
Percent dose depth falls of rapidly
Increasing the beam on time can increase the effective energy of the photon beam.
Increasing the tube potential can increase the effective energy of the photon beam.
*The machine that consists of short metallic cylinders divided into two D-Shaped cavities is known as the:
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