Q 71-105

Question 1

Practically, a linac’s mechanical isocenter encompasses a small volume of space rather than an
infinitesimally small point due to _____.
A. gantry sag
B. imprecision in collimator rotation
C. imprecision in couch rotation
D. All of the above are true.
E. None of the above is true.

Answer 1

D. All of the above are true.

Question 2

How is a patient’s name associated with a series of CT slices in the DICOM standard?
A. Patient demographic information is contained within a text file in the same folder as the
CT image file.
B. Patient demographic information is contained within a header inside the CT image file.
C. The name of the CT image file must contain the patient’s name.
D. The name of the CT image file must contain a unique code that can get traced back to the
patient demographic information on the CT scanner.
E. None of the above is true.

Answer 2

B. Patient demographic information is contained within a header inside the CT image file.

Question 3

The verification that a system is behaving to specifications mutually agreed upon by the vendor
and the customer as specified in the purchase contract is defined as _____.
A. quality control
B. quality assurance
C. acceptance testing
D. commissioning
E. periodic review

Answer 3

C. acceptance testing

Question 4

The thickness of lead required to reduce the exposure rate from 3.0 mR/hr to 1.0 mR/hr behind a
secondary barrier, given a TVL = 1.9 inches, is _____.
A. ¼”
B. ½”
C. ¾”
D. 1”
E. 2”

Answer 4

D. 1”

Question 5

According to NCRP Report 160 (Ionizing Radiation Exposure of the Population of the United
States), the average exposure of the general U.S. population to ionizing radiation doubled from the
1980s to 2006, most attributed to increased _____.
A. use of medical imaging
B. nuclear accidents
C. space background
D. radon exposure
E. None of the above is true.

Answer 5

A. use of medical imaging

Question 6

The concrete shielding of an existing linear accelerator vault is calculated to be insufficient for a
new high-energy machine and will require placement of 2” of lead. Where should the lead be
positioned relative to the concrete, given in order from the first material the beam interacts with to
the last?
A. 2” lead then concrete
B. concrete then 2” lead
C. 1” lead, then concrete, then 1” lead
D. All of the above are equivalent.
E. We are unable to determine this from the information given.

Answer 6

A. 2” lead then concrete

Question 7

Which of the following patient exposures would typically result in the highest radiation dose to a
registered nurse caring for a patient?
A. simulation CT-scan
B. external beam radiotherapy treatment fraction using photons
C. external beam radiotherapy treatment fraction using electrons
D. brachytherapy treatment using a remote afterloader
E. iodine-131 treatment

Answer 7

E. iodine-131 treatment

Question 8

The survey meter typically used for radiation surveys of new linear accelerators utilizes \_\_\_\_\_.
A. thermoluminescent dosimeters
B. an ion chamber
C. a Geiger-Mueller counter
D. a diode array
E. radiochromic film

Answer 8

B. an ion chamber

Question 9

Given a 512 × 512 image file and a field of view of 500 mm, the pixel size will be approximately
\_\_\_\_\_.
A. 0.1 mm
B. 0.2 mm
C. 1 mm
D. 2 mm
E. 5 mm

Answer 9

C. 1 mm

Question 10

Which imaging modality has the best soft tissue contrast?
A. MV portal imaging
B. kV radiography
C. kV fluoroscopy
D. kV cone-beam CT
E. All have similar soft tissue contrast.

Answer 10

D. kV cone-beam CT

Question 11

Which of the following would result in the LEAST dose to the lens of the eye when acquiring a
setup image for a patient receiving radiotherapy to the nasal cavity?
A. AP kV planar x-ray
B. PA kV planar x-ray
C. AP MV planar x-ray
D. PA MV planar x-ray
E. All would deliver similar doses.

Answer 11

B. PA kV planar x-ray

Question 12

The spatial resolution of an ultrasound image can be improved by \_\_\_\_\_ the frequency and \_\_\_\_\_
the beam width.
A. increasing; decreasing
B. increasing; increasing
C. decreasing; decreasing
D. decreasing; increasing

Answer 12

A. increasing; decreasing

Question 13

Positron Emission Tomography (PET) images are formed by detecting two \_\_\_\_\_ emitted in
colinear directions.
A. positrons
B. electrons
C. protons
D. photons
E. None of the above is true.

Answer 13

D. photons

Question 14

On a T1-weighted MR image, \_\_\_\_\_ appears brightest.
A. air
B. blood
C. cerebrospinal fluid (CSF)
D. cortical bone
E. fat

Answer 14

E. fat

Question 15

Regarding CT dose index (CTDI), which of the following statements is FALSE?
A. CTDI100 is the measured dose in one scan rotation over a longitudinal length of
100 mm.
B. CTDI100 is the measured dose at 100 cm from the source in one scan rotation.
C. AAPM TG-75 recommends the reporting of CT dose in the units of CTDI.
D. There are challenges with CTDI100 in a cone-beam geometry that is wider than 100 mm.
E. CTDIw is the weighted average of CTDI100 measurements at two different locations in a
phantom, one central and one peripheral.

Answer 15

B. CTDI100 is the measured dose at 100 cm from the source in one scan rotation.

Question 16

The main difference between cone-beam CT and helical CT is _____.
A. x-ray energy
B. radiation dose
C. availability of a variety of reconstruction algorithms
D. reconstruction time
E. volume of interest acquired per projection

Answer 16

E. volume of interest acquired per projection

Question 17

According to the report of AAPM Task Group 142, the test of cone-beam CT constancy of
Hounsfield Units should be performed _____.
A. daily
B. weekly
C. monthly
D. semi-annually
E. annually

Answer 17

C. monthly

Question 18

For CT imaging, as the \_\_\_\_\_ decreases, the signal-to-noise ratio (SNR) increases.
A. dose
B. slice thickness
C. patient thickness
D. All of the above are true.
E. None of the above is true.

Answer 18

C. patient thickness

Question 19

The Dose Volume Histogram (DVH) will be inaccurate if the underlying structure’s contours
_____.
A. are missing slices
B. contain stray pixels
C. only segment the portion of the structure in the treated area
D. All of the above are true.
E. None of the above is true.

Answer 19

D. All of the above are true.

Question 20

Which of the following is NOT considered in the determination of the various target volume
expansions that expand GTV to PTV in radiation therapy?
A. intra-fractional patient motion
B. inter-fractional patient motion
C. microscopic disease
D. internal target movement
E. dose calculation uncertainties

Answer 20

E. dose calculation uncertainties

Question 21

Following the formalism of AAPM TG-263 for standardization of dosimetric nomenclature, how
would the dose be requested for 95% of the target volume relative to the prescription dose?
A. D5Gy[Gy]
B. V5Gy[%]
C. D5%[Gy]
D. V5%[Gy]
E. V5%[%]

Answer 21

E. V5%[%]

Question 22

4D cone-beam CT for treatment setup is most advantageous over a free breathing cone-beam CT
in which scenario?
A. cranial SRS
B. lower lung SBRT
C. conventionally treated mediastinal mass
D. partial breast irradiation
E. prostate

Answer 22

B. lower lung SBRT

Question 23

\_\_\_\_\_ cGy is the typical MV-CBCT dose to isocenter for a pelvic case.
A. 0.01
B. 0.1
C. 1
D. 10
E. 100

Answer 23

D. 10

Question 24

Advantages of surface-based optical image guidance include _____.
A. no ionizing radiation
B. continuous monitoring during treatment
C. the ability to monitor respiratory gating
D. All of the above are true.
E. None of the above is true.

Answer 24

D. All of the above are true.

Question 25

Which of the following is a DISADVANTAGE of the use of optical surface imaging (OSI) for
frameless intracranial stereotactic radiosurgery alignment?
A. It can be used by RTTs while inside the treatment room.
B. It has sub-millimeter accuracy for patient motion detection.
C. It uses the face as a surrogate for the lesion position.
D. All of the above are true.
E. None of the above is true.

Answer 25

C. It uses the face as a surrogate for the lesion position.

Question 26

_____ techniques can be used for monitoring deep inspiration breath-hold (DIBH) breast
treatment.
A. Infrared monitoring of external fiducial
B. Optical surface imaging
C. Spirometry
D. All of the above are true.
E. None of the above is true.

Answer 26

D. All of the above are true.

Question 27

The leaf-sequencing algorithm in a treatment planning system is responsible for _____.
A. creating an optimal fluence pattern
B. converting an optimal fluence to a deliverable fluence
C. calculating the dose distribution based on a deliverable fluence
D. exporting the MLC control points to the delivery software
E. None of the above is true.

Answer 27

B. converting an optimal fluence to a deliverable fluence

Question 28

The photon IMRT delivery technique that is characterized by having the beam turn off between
control points is \_\_\_\_\_.
A. VMAT
B. step and shoot
C. sliding window
D. spot scanning
E. 3D conformal arcs

Answer 28

B. step and shoot

Question 29

Which of the following IMRT QA gamma criteria is the most restrictive?
A. 2%; 2 mm
B. 2%; 5 mm
C. 5%; 2 mm
D. 5%; 5 mm
E. One cannot tell with the information given

Answer 29

A. 2%; 2 mm

Question 30

\_\_\_\_\_ are most indicative of a highly modulated field.
A. Numerous small apertures and high MUs
B. Numerous small apertures and low MUs
C. Numerous large apertures and high MUs
D. Numerous large apertures and low MUs
E. A large number of control points

Answer 30

A. Numerous small apertures and high MUs

Question 31

Which of the following techniques will deliver 21 Gy to a round brain lesion away from organs at
risk in the shortest amount of time while providing similar coverage at the same beam energy and
available maximum dose rate?
A. VMAT
B. step and shoot
C. sliding window
D. conformal arcs
E. All of the above would take the same amount of time.

Answer 31

D. conformal arcs

Question 32

_____ is NOT typically modulated within a linac-based VMAT arc delivery.
A. Gantry speed
B. Dose rate
C. MLC speed
D. Beam energy
E. All of the above are typically modulated.

Answer 32

D. Beam energy