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Boards Review > W/L Ch 24 Photon Dose Distribution Quiz > Flashcards

W/L Ch 24 Photon Dose Distribution Quiz Flashcards

1
Q

What is (are) spatial representation(s) of the magnitude of the dose produced by a source of radiation?

a. Treatment planning
b. Dose distributions
c. Dose calculation matrix
d. Dose-volume histogram (DVH)

A

b. Dose distributions

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2
Q

Which of the following statements is false concerning beam profiles?

a. A beam profile describes radiation intensity as a function of position across the beam at a given depth.
b. A beam profile depicts the beam’s intensity in a direction perpendicular to the beam’s direction.
c. A beam profile is another one-dimensional spatial representation of the variation of beam intensity.
d. A beam profile is characterized by a continuous and gradual decrease in beam intensity.

A

d. A beam profile is characterized by a continuous and gradual decrease in beam intensity.

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3
Q

What determines the wedge angle?

a. The angle of the 100% isodose line with a line perpendicular to the central axis
b. The actual measurements of the wedge
c. The angle of the 80% isodose line with a line perpendicular to the central axis
d. Two times the hinge angle

A

c. The angle of the 80% isodose line with a line perpendicular to the central axis

The angle between the slanted isodose line and a line perpendicular to the central axis of the beam is called the wedge angle. Because, for any given wedge, the tilt of isodose lines varies slightly with depth, either the depth of the 80% depth dose or a depth of 10 cm is often chosen for wedge-angle measurement and subsequent wedge attenuator design.

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4
Q

What is the most common field arrangement used in radiation therapy?

a. Single field
b. Parallel-opposed
c. Four-field box
d. Wedged-pair

A

b. Parallel-opposed

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5
Q

What determines the hinge angle?

a. The angle between two beams’ central axes that share an isocenter
b. The angle of the 80% isodose line with a line perpendicular to the central axis of a wedges field
c. The angle of the 100% isodose line with a line perpendicular to the central axis of a wedges field
d. The wedge angle divided by 2

A

a. The angle between two beams’ central axes that share an isocenter

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6
Q

What are the appropriate wedges needed for beams with a hinge angle of 120 degrees?

a. 15 degree
b. 30 degree
c. 45 degree
d. 60 degree

A

b. 30 degree

ø = 90° - ( hinge angle / 2)
ø =  90° - (120°/2)
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7
Q

Which of the following factors can be corrected to adjust the isodose lines of beams with oblique incidences?
I. PDD
II. TAR
III. TMR

a. I and II
b. I and III
c. II and III
d. I, II, and III

A

d. I, II, and III

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8
Q

In the effective source-skin distance method and TAR method of correcting isodose curves for oblique incidence, what does the factor h represent?

a. Inverse square correction
b. Depth
c. Tissue deficit or excess
d. Source-skin distance, tissue-air ratio, or tissue-maximum ratio

A

c. Tissue deficit or excess

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9
Q

Beam attenuation in energy ranges typically used in radiation therapy is primarily the result of which type of interaction?

a. Compton scatter
b. Photoelectric effect
c. Pair production
d. All are equal

A

a. Compton scatter

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10
Q

In which tissue heterogeneity correction method are both the field size and the depth “scaled” to account for the presence of heterogeneities?

a. Power law TAR method
b. Generalized Batho correction
c. Equivalent TAR method
d. Delta volume method

A

c. Equivalent TAR method

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11
Q

In which tissue heterogeneity correction method are primary and scatter separated?

a. Power law TAR method
b. Generalized Batho correction
c. Equivalent TAR method
d. Delta volume method

A

d. Delta volume method

In delta volume method, primary and scatter are separated. The irradiated volume is broken into volume elements, and scatter is computed from a weighted summation of the scatter from each of the volume elements. This scatter is then added to the primary.

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12
Q

Which of the following is the most favorable situation for the overall goal of radiation therapy?

a. Radiosensitive tumor and radiosensitive normal tissue
b. Radiosensitive tumor and radioresistant normal tissue
c. Radioresistant tumor and radioresistant normal tissue
d. Radioresistant tumor and radiosensitive normal tissue

A

b. Radiosensitive tumor and radioresistant normal tissue

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13
Q

Which type of intensity-modulated radiation therapy treatment delivery has the gantry in a fixed position with an initial multileaf collimators (MLC) pattern?

a. “Step-and-shoot”
b. Dynamic MLC
c. “Tomotherapy”
d. Robotic IMRT

A

a. “Step-and-shoot”

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14
Q

Which type of IMRT treatment involves the “sliding window” technique?

a. “Step-and-shoot”
b. Dynamic MLC
c. “Tomotherapy”
d. Robotic IMRT

A

b. Dynamic MLC

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15
Q

During IMRT treatments, how is the intensity of the beam altered?

a. Insertions of a wedge
b. Movement of the collimators
c. Movement of the MLCs
d. Fluctuations in beam energy

A

c. Movement of the MLCs

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16
Q

In the convolution algorithm, primary fluence is represented by what symbol?

a. D(r)
b. φ(r)
c. K
d. dV

A

b. φ(r)

The primary fluence,φ(r), describes the primary dose that exists at the point r.

17
Q

Which of the following is the palpable, visible, or demonstrable extent and location of malignant growth and is the volume of known disease?

a. GTV
b. CTV
c. PTV
d. Treated volume

A

a. GTV

18
Q

Which of the following accounts for target motion and uncertainty in positioning?

a. GTV
b. CTV
c. PTV
d. Treated volume

A

c. PTV

19
Q

Which of the following imitates a radiograph by reconstructing the diverge-corrected patient anatomy from the CT data set?

a. BEV
b. DVH
c. DRR
d. REV

A

c. DRR

20
Q

Which of the following is a plot of target or normal structure volume as a function of dose?

a. BEV
b. DVH
c. DRR
d. REV

A

b. DVH

21
Q

At what point does the treatment planning process begin?

a. Dose determination
b. Beam delineation
c. Organ segmentation
d. CT imaging

A

d. CT imaging

22
Q

The percent depth dose curve (PDD) is a representation of dose variation in __________ dimensions.

a. one
b. two
c. three
d. four

A

a. one

23
Q

The process of identifying structures, target volumes, or normal tissues, by creating contours around them, is often called _____________________.

a. organ segmentation
b. virtual simulation
c. intensity modulation
d. heterogeneity correction

A

a. organ segmentation

24
Q

The internal target volume (ITV) is the __________.

a. GTV + CTV
b. CTV + IM
c. PTV – GTV
d. ITV + SM

A

b. CTV + IM

The internal target volume is the internal margin (IM) added to the clinical target volume (CTV) to account for the CTV’s internal motion within the patient.

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