CH 6 (Radiation Therapy Equipment and QA)

The common acceptable value for field flatness if about __% over the central 80% of the largest field at isocenter.

+/- 3%

Gantry and collimator indicators should be accurate within __ degree(s).

1 degree

Electrons are accelerated to high energy in the __

Accelerating guide

These components, through which electrons travel, are under very high vacuum

Accelerating guide

At the end of acceleration, high energy electrons are focused toward the collimator opening by the __

Bending magnet

During a split field test for longitudinal displacement of the collimator for jaw symmetry, the collimator is rotated to angles of: A. 360 degrees B. 270 degrees C. 180 degrees D. 90 degrees

C. 180 degrees

A mechanical distance indicator is used to verify: A. Gantry rotation B. Collimator rotation C. Field size congruence D. Accuracy of the optical distance indicator

D. Accuracy of the optical distance indicator

Electrons are produced in the __

Electron gun

X-ray beam intensity is made uniform over the field size at the isocenter by the __

Flattening filter

This monitors radiation output

Ion chamber

What 3 things monitor radiation beam uniformity by monitoring and controlling symmetry and flatness?

Ion chamber Scattering foil Flattening filter

Microwave power is produced to accelerate electrons in the __

Klystron

This produces high voltage and high power electrical pulses to generate microwave power

Modulator

Reference signal is provided for generation of microwave power in what 2 things?

Modulator and radiofrequency driver

The electron beam is spread out uniformly over the field area by the __

Scattering foil

X-rays are produced by bremsstrahlung and characteristic radiation process in the __

Target

Microwave power is directed toward the accelerator guide in the __

Waveguide

Microwaves travel through these 2 components and are prevented from reflecting backward

Waveguide and radiofrequency driver

The symmetry and flatness of the clinical photon beam can be checked using (more than 1 may apply): a. film b. a beam profiler c. a calorimeter d. none of the above

a and b

Which of the following checks must be carried daily on the cobalt machine (more than 1): a. function of radiation room monitor b. function of door interlocks c. beam output d. timer error

a and b

The important QA test(s) associated with the light field are (more than 1 answer): a. field size accuracy b. beam output c. light and radiation field coincidence d. none of the above

a and c

The protective housing around the cobalt source in the cobalt machine should only allow transmission of __ of the output. a. 0.1% b. 1% c. 2% d. 5%

a. 0.1%

The tolerance for the coincidence of light and radiation field, in the case of the medical linac is: a. 2mm or 1% of field length being measured, whichever is greater b. 3mm c. 5mm d. none of the above

a. 2mm or 1% of field length being measured, whichever is greater

The energy range for the early generation superficial therapy machines is: a. 50 to 150 kV b. 150 to 500 kV c. 600 to 1000 MV d. 20 to 25 MeV

a. 50 to 150 kV

In the case of brachytherapy sources: a. all sources must be leak tested b. short half-life sources need never be tested for leakage c. sources not in use need not be tested for leakage d. long half-life sources only need leak testing annually

a. all sources must be leak tested

Which of the following verifies the accuracy of radiation dose delivery? a. back up timer, radiation off switch, door interlock, and emergency off switch b. back up timer, door interlock, and override switch c. radiation off switch and override switch d. door interlock, radiation off switch and collision ring

a. back up timer, radiation off switch, door interlock, and emergency off switch

The machine that consists of a short metallic cylinder divided into two D-shaped cavities is known as the: a. cyclotron b. betatron c. microtron d. van de graaf

a. cyclotron

The constancy of linac output for photon and electron beams must be checked: a. daily b. weekly c. monthly d. only during commissioning

a. daily

As distance from the source increases, penumbra __ a. increases b. decreases

a. increases

A short exposure is taken on a radiographic film aligned with metallic marks on the borders of a collimated light field. This describes testing for: a. light field/radiation coincidence b. field flatness c. collimator symmetry d. field intensity

a. light field/radiation coincidence

The klystron or magnetron is the source of __ in the linear accelerator. a. microwaves b. alternating current c. accelerated fields d. magnetic fields

a. microwaves

OBI is an acronym for: a. onboard imaging b. off beam indicator c. optical beam indicator d. off baseline measurement indicator

a. onboard imaging

Trimmer bars are attached to the collimator of a cobalt machine to reduce the effect of: a. penumbra b. symmetry c. flatness d. dose

a. penumbra

The field light on the linear accelerator is intended to represent: a. the area of radiation exposure b. the size of the target c. the width, length, and depth of the treatment field d. the distance from the source of radiation to the patient's skin

a. the area of radiation exposure

What type of target is used in high energy linear accelerators? a. transmission type b. resection type c. refraction type d. none of the above

a. transmission type

The target in the linear accelerator is typically made of: a. tungsten b. aluminum

a. tungsten

A long cylinder loaded with radioisotopes and placed in the vaginal space could be used to treat the: a. vaginal vault b. endometrium c. pelvic side wall d. vulva

a. vaginal vault

Functional performance of radiation therapy equipment can (more than 1 answer): a. not vary with time b. change due to malfunction of system electronics or component fault c. change due to wear and tear of the equipment d. change due to environmental conditions

b and c

In 1 month, the output of a cobalt machine would reduce by about: a. 0.1% b. 1% c. 2% d. 5%

b. 1%

Output corrections must be made monthly when using cobalt sources. The correction is about: a. 0.1% per month b. 1% per month c. 5% per month d. 10% per month

b. 1% per month

The average gamma energy for cobalt-60 is: a. 1.33 MV b. 1.25 MV c. 1.17 MV d. 0.66 MV

b. 1.25 MV

The x-ray beam in the linac must exhibit flatness within about: a. 1% b. 2% c. 5% d. none of the above

b. 2%

Localizing lasers on simulators must be within __ of isocenter. a. 1mm b. 2mm c. 3mm d. 2cm

b. 2mm

The tolerance for the localizing laser and the ODI indicator is: a. 1mm b. 2mm c. 5mm d. none of the above

b. 2mm

The collimator, gantry, and couch of a conventional simulator rotate about their respective axes. The recommended tolerance for locating the isocenter in these rotations is a sphere of dimension: a. 2mm radius b. 2mm diameter c. 5mm radius d. none of the above

b. 2mm diameter

The constancy of linac output, when compared with the benchmark values established during commissioning, must be within: a. 1% b. 3% c. 5% d. none of the above

b. 3%

The target of the linac must have: a. a low melting point b. a high melting point c. the ability to bend d. low thermal conductivity

b. a high melting point

To check the accuracy of gantry digital readouts, one could use: a. closed collimators b. a spirit level at 45 degree angle increments c. a breast bridge at 90 degree angle increments d. a spirit level at 180 degree angle increments

b. a spirit level at 45 degree angle increments

Scan and couch vertical positional accuracy for CT planning must be: a. <1mm b. about 2mm c. about 5mm d. about 1cm

b. about 2mm

The linear accelerator generates a high-energy photon or electron beam by: a. accelerating charged particles in a circular pattern b. accelerating charged particles in a linear path c. producing electromagnetic pulses used to accelerate protons and neutrons d. keeping photons in synch with a magnetic field

b. accelerating charged particles in a linear path

The process for testing a new accelerator against manufacturer's specifications before putting it into service is termed: a. insurance calibration testing b. acceptance testing c. error correction testing d. quality assurance testing

b. acceptance testing

The purpose of a positioning device is to: a. make the patient comfortable b. accommodate the most appropriate position for accurate treatment delivery c. prevent or limit patient motion during treatment d. limit the setup time

b. accommodate the most appropriate position for accurate treatment delivery

As SDD increases, penumbra: a. increases b. decreases

b. decreases

As the source size decreases, penumbra: a. increases b. decreases

b. decreases

A high energy photon unit will require daily quality checks for the determination of: a. light and radiation field coincidence b. dose rate constancy c. field symmetry and flatness d. crosshair centering

b. dose rate constancy

The scattering foil is placed in the path of the stream of electrons in the linear accelerator when programmed to operate in the _____ beam mode. a. proton b. electron c. x-ray d. fluoroscopic

b. electron

Heyman capsules may be used to treat the : a. vaginal vault b. endometrium c. vulva d. prostate

b. endometrium

Which of the following has the shortest half-life? a. cesium-137 b. gold-198 c. iridium-192 d. radon-222

b. gold-198

To ensure the patient's safety during treatment on a mega voltage linear accelerator, the patient must be monitored by: a. directions given before treatment b. intercommunication systems c. watching the patient through a window d. instructing the patient to yell out for help as needed

b. intercommunication systems

The fletcher's suite application is an example of: a. interstitial low dose rate brachytherapy b. intracavitary low does rate brachytherapy c.permanent implant brachytherapy d. injected, unsealed source brachytherapy

b. intracavitary low does rate brachytherapy

If the mirror and bulb assembly has to be replaced, it is critical to perform the following quality check(s) before using the machine: a. dose rate b. light field and radiation coincidence c.. collimator angle readout d. gantry angle readout

b. light field and radiation coincidence

While treating a patient using a rotational arc technique, the gantry rotates beyond the endpoint. This is likely a malfunction of the: a. operator's console b. limit switch c. collision ring d. override switch

b. limit switch

Brachytherapy sources must be calibrated (more than 1 may apply): a. by the manufacturer only b. by the accredited dosimetry calibration laboratory only c. before being used for clinical dosimetry d. by a user using a chamber with calibration traceable to an accredited dosimetry calibration laboratory

c and d

The linear scales on the treatment tables are useful as an aid for: 1. daily treatment setup 2. translation of patient positions from simulation to treatment 3. providing information regarding filament voltage a. 1 b. 3 c. 1, 2 d. 1, 2, 3

c. 1, 2

The target to patient skin distance is measured using: a. a meter scale b. an SSD rod c. an ODI indicator d. none of the above

c. an ODI indicator

Which of the following machines does not accelerate electrons? a. microtron b. betatron c. cyclotron d. X-ray tube

c. cyclotron

The source of electrons in a linear accelerator is the: a. klystron b. magnetron c. electron gun d. waveguide

c. electron gun

All of the following might account for a beam's flatness deviating outside specifications, except: a. flattening filter shift b. target position shift c. incorrect mirror angulation d. fluctuation of current

c. incorrect mirror angulation

In early generation kV therapy machines, the quality of the photon beam could be increased by: a. increasing the mA b. decreasing the half value layer of material c. increasing the filtration d. decreasing the kVp

c. increasing the filtration

The effective energy of a photon beam can be increased by: a. increasing the beam on time b. increasing the tube current c. increasing the tube potential

c. increasing the tube potential

Cobalt beam output must be checked: a. daily b. weekly c. monthly d. annually

c. monthly

Which of the following radioisotopes is a pure beta emitter? a. cesium-137 b. cobalt-60 c. phosphorus-32 d. iodine-131

c. phosphorus-32

The cyclotron may produce __ beams. a. electron b. x-ray c. proton d. gamma ray

c. proton

The exact position of the source in the applicator can be checked by: a. visual inspection b. measuring the AKS strength of the source c. taking a radiograph d. none of the above

c. taking a radiograph

Geometric penumbra, characteristic of the cobalt beam, increases with: 1. increasing beam energy 2. increasing source size 3. increasing distance from the source 4. decreasing beam energy a. 2, 4 b. 1, 2 c. 3, 4 d. 2, 3

d. 2, 3

The teletherapy cobalt machine has a beam stopper. The purpose of the beam stopper is to: a. prohibit the primary beam from penetrating adjacent wall and ceiling b. prohibit scatter radiation in the treatment room c. act as a counter-balance to the heavy gantry head d. a and c are correct

d. a and c are correct

In a brachytherapy procedure room, the following items must be available all the time: a. a radiation survey meter b. a temporary storage container c. a cutter and long-handled tongs d. all of the above

d. all of the above

Full calibration and overhaul of treatment equipment must be carried out: a. daily b. weekly c. monthly d. annually

d. annually

Safety door interlocks should be checked: a. annually b. monthly c. weekly d. daily

d. daily

The purpose of the flattening filter in the linac is to: a. direct the stream of electrons out toward the collimator opening b. prevent deflection of microwaves c. evenly distribute and spread out the raw electron beam across a specified area d. evenly distribute the energy of the photon beam across a specified area

d. evenly distribute the energy of the photon beam across a specified area

The gantry head of the linear accelerator contains all of the following except: a. flattening filter b. ion chamber c. x-ray target d. klystron

d. klystron

Superficial therapy machines used short treatment distances because: a. more precise positioning of the beam is provided than at longer distances b. less shielding against leakage radiation is required than at longer distances c. shorter distances are more biologically effective than longer distances d. percent depth dose falls off rapidly e. secondary radiation augments the skin dose

d. percent depth dose falls off rapidly

Which of the following radioisotopes is used for diffuse bone metastasis? a. cesium-137 b. cobalt-60 c. strontium-90 d. strontium-89

d. strontium-89

The BAT system uses ___ energy to localize the treatment target. a. x-ray b. microwave c. radiofrequency d. ultrasound

d. ultrasound