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Dosi Mock Exam Q's > Mock Exam 1 > Flashcards

Mock Exam 1 Flashcards

1
Q

Which of the following does NOT represent an advantage of CT images for treatment planning?

  • functional abnormalities caused by tumor extension are visualized
  • density contouring can be done
  • 3 dimensional information can be generated
  • images can be modified to give different contrast as desired
A

-functional abnormalities caused by tumor extension are visualized

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2
Q

The pituitary gland is:

  • a midline structure located in the sella turcica
  • an endocrine gland
  • consists of two lobes
  • all of the answers are correct
A
  • all of the answers are correct
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3
Q

IMRT is a treatment planning and delivery process that seeks to achieve treatment plan optimization by varying the ________ of treatment beams in addition to their position.

  • field size
  • area
  • energy
  • intensity
A
  • intensity
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4
Q

The protocol currently recommended by the AAPM for calibrating megavoltage therapy units is:

  • SCRAD
  • The Nordic Protocol
  • TG-51
  • ICRU Report 21
A

-TG-51

This is the report No.67 of AAPM Task Group 51, published in 1999 (Protocol for clinical reference dosimetry of high energy photon and electron beams)

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5
Q

Thimble chambers are used to calibrate radiation beams because:

  • they are sturdy
  • they have good spatial resolution
  • they do not significantly perturb the beams
  • all of the answers are correct
A

-all of the answers are correct

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6
Q

Thermoluminescence refers to the emission of:

  • heat production during electron beam delivery
  • photons when an electron beam strikes the target
  • light from phosphorus materials when heated
  • radioactivity from a thermonuclear reaction
A

-light from phosphorus materials when heated

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7
Q

The most commonly used TLD material used in radiation dosimetry is:

  • CaSo4
  • CaF2
  • LiF
  • Li2B
A

-LiF

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8
Q

An unsealed chamber as a secondary dosimeter gives a reading of 101.0 for a 100 monitor unit exposure at a field size of 10 x 10 cm. If the ambient temperature is 25 degrees C and the atmospheric pressure is 770 mm Hg, the corrected reading per monitor unit is:

  • 0.923
  • 0.997
  • 1.007
  • 1.013
  • 1.034
A

-1.007

(760/770) x (298/295) = 0.997

0.997 x (101/100MU)= 1.007

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9
Q

What of the following connects two or more networks within a city?

  • Connection Area Network (CAN)
  • Local Area Network (LAN)
  • Metropolitan Area Network (MAN)
  • Wide Area Network (WAN)
A

-Metropolitan Area Network (MAN)

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10
Q

Thin window parallel-plate chambers are useful for measuring radiation dose at or near:

  • the surface
  • a 5cm depth
  • a 10 cm depth
  • an equilibrium depth
A

-the surface

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11
Q

For stereotactic radiosurgery, accuracy and reproducibility should generally be on the order of ____ mm.

  • 0.5
  • 1.0
  • 2.0
  • 5.0
A

-1.0

An overall accuracy of +/- 1mm in the coverage of the intended target volume is a commonly accepted standard for the SRS and SRT procedures.

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12
Q

Which of the following problems may be encountered in the use of diagnostic CT data in radiation therapy treatment planning?

  • vertical and horizontal scales may differ, resulting in image distortion
  • small scan ring may result in side cut-off of patient contour
  • the position of the patient in the scanner may not duplicate the therapy setup
  • cross-sectional CT images can provide inaccurate tissue heterogeneity corrections if the data do not correlate with the CT tables in the treatment planning computer
  • All are correct
A

-All are correct

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13
Q

Which of the following tissues is the least radiosensitive?

  • ovaries
  • ocular lens
  • small intestine
  • bone and cartilage
A

-bone and cartilage

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14
Q

A single field megavoltage treatment plan displays the effects of which of the following?

  • penumbra
  • flattening filter
  • patient contour
  • field normalization
  • all are correct
A

-all are correct

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15
Q

Which of the following statements is true concerning a 3D pencil beam algorithm?

  • It does not consider the effects of scatter to and from heterogeneities, irregular surfaces, or irregularly blocked fields
  • It divides the broad beam into many small thin beams that can have their own intensity and lateral scatter spread
  • It uses an equivalent pathlength calculation that converts any heterogeneity into homogenous water medium through an attenuation equivalent thickness coefficient
  • The pencil beam is not a three dimensional calculation
  • All are correct
A

-It divides the broad beam into many small thin beams that can have their own intensity and lateral scatter spread

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16
Q

Bolus is often used in electron beam therapy to do all of the following EXCEPT:

  • reduce the amount of scatter due to inhomogeneities
  • reduce the penetration of the electrons in parts of the field
  • increase the surface dose
  • flatten out an irregular surface
A

-reduce the amount of scatter due to inhomogeneities

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17
Q

The decay constant describes:

  • the half-life of a particular radionuclide
  • the number of ionizations produced in tissue per unit time
  • the fraction of the number of atoms that decay per unit time
  • none of the answers are true
A

-the fraction of the number of atoms that decay per unit time

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18
Q

Treatment of an anterior supraclavicular nodal field would be indicated in all of the following EXCEPT:

  • T2N2 tonsil
  • T4N2 oral tongue
  • T2N3 nasopharynx
  • T1N0 larynx
A

-T1N0 larynx

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19
Q

The tumor type that is most responsive to radiation treatment is:

  • melanoma
  • squamous cell carcinoma
  • adenocarcinoma
  • sarcoma
  • seminoma
A

-seminoma

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20
Q

The professional body that promotes medical dosimetry as a specialized field is:

  • the American Association of Physicists in Medicine (AAPM)
  • the American Board of Radiology (ABR)
  • the American Roentgen Society (ARS)
  • the American Association of Medical Dosimetrists (AAMD)
  • the American College of Medical Physicists (ACMP)
A

-the American Association of Medical Dosimetrists (AAMD)

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21
Q

What is the term describing certain chemicals or drugs that enhance the response of cells to radiation?

  • Free radicals
  • radiosensitizers
  • radioprotectors
  • biologic rescue factors
A

-radiosensitizers

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22
Q

According to the AAPM TG-40 report, linear accelerator output should be:

  • spot checked daily before each patient
  • spot checked daily before treatment
  • calibrated monthly by the dosimetrist
  • calibrated bi-annually using a water tank
  • calibrated annually using a solid water phantom
A

-spot checked daily before treatment

Output checked daily by therapist; calibration is part of monthly physics QA; calibration in water is part of annual QA

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23
Q

What of the following defines TD5/5?

  • 5% reduction of tumor cells in 5 days
  • cell population reduction to 5% after 5 Gy
  • 5% complication rate in 5 years
  • 5% survival rate in 5 years
A

-5% complication rate in 5 years

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24
Q

Which of the following is NOT one of the four R’s of radiation biology?

  • redistribution
  • reoxygenation
  • reconfirmation
  • repopulation
A

-reconfirmation

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25
Q

The quality factor (QF) used for determining the dose equivalent for high-energy X-rays compared to high-energy gamma rays is:

  • 1
  • 2
  • 5
  • 20
A

-1

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26
Q

The presence of a shoulder on the survival curve of most mammalian cells indicates which of the following?

  • a reduced efficiency of cell killing at low doses
  • that cell killing is an exponential function of dose
  • the random nature of radiochemical injury
  • that tissue tolerance is related to the volume irradiated
  • a link between cell-death and cell-division rate
A

-a reduced efficiency of cell killing at low doses

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27
Q

The distance between the ends of radioactive material in a radioisotope tube is known as:

  • permanent activity
  • active length
  • physical length
  • filtration distance
A

-active length

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28
Q

The approximate density of fat is:

  • 0.30 g/cc
  • 0.95 g/cc
  • 1.00 g/cc
  • 1.03 g/cc
  • 1.65 g/cc
A

-0.95 g/cc

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29
Q

CT numbers are expressed in terms of:

  • cm squared/gram
  • cm -1
  • Roentgen units (RU)
  • Hounsfield Units (HU)
A

-Hounsfield Units (HU)

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30
Q

Which of the following precautions would most effectively reduce radiation exposure to family members visiting a patient with an Iridium implant?

  • Double the distance between the patient and the family
  • Place a lead shield of one HVL thickness between the patient and the family
  • Reduce the visiting time by one-half
  • Place a personal radiation detection monitor on each visiting family member
  • All options are equally effective
A

-Double the distance between the patient and the family

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31
Q

Prior to the administration of a brachytherapy remote afterloading treatment, the following are required EXCEPT:

  • preparation of a signed written directive
  • independent confirmation of treatment time
  • calibration of the treatment unit
  • verification of the patient’s identity
A

-calibration of the treatment unit

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32
Q

Autoradiography of an encapsulated brachytherapy source is:

  • an automatic afterloading technique used to reduce exposure to the nursing staff
  • a procedure using three radiographs to automatically identify radioactive seeds
  • a manufacturing process used to ensure all sources have the same activity
  • a method of using the sources in the patient to produce radiographs
  • a test for gross nonuniformity of the radionuclide within a source capsule
A

-a test for gross nonuniformity of the radionuclide within a source capsule

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33
Q

A tumor, treated at 100 cm SAD, measures 4 cm in diameter on a film with an FFD of 145 cm. What is the actual size of the tumor?

  • 1.24 cm
  • 2.75 cm
  • 4 cm
  • 12.8 cm
A

-2.75 cm

100 cm / 145 cm = 0.6896
0.6896 x 4 cm = 2.75 cm

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34
Q

Parallel-plate ionization chambers are primarily used to measure:

  • ionization at deeper locations in a phantom
  • surface dose
  • scattered radiation dose
  • interstitial dose
A

-surface dose

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35
Q

According to AAPM’s TG40 report on QA, daily linac checks should include all of the following except:

  • output for each photon energy
  • patient viewing system
  • accuracy of laser alignment
  • accuracy of distance indicator
  • symmetry of each photon energy
A

-symmetry of each photon energy

Beam flatness and symmetry are checked by the physicist during monthly QA

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36
Q

Which of the following are true statements regarding linac commissioning?

  • linac commissioning should be done prior to clinical use
  • linac commissioning should be done by a qualified medical physicist
  • linac commissioning requires measurement of all beam parameters
  • all of the answers are correct
A

-all of the answers are correct

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37
Q

A good standard of practice requires that a treatment machine should undergo a complete calibration at least:

  • before any treatment
  • daily
  • weekly
  • monthly
  • annually
A

-annually

Most federal and professional standards require an annual complete calibration

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38
Q

A constancy check of radiation beams should be performed at least:

  • daily
  • weekly
  • monthly
  • annually
A

-daily

Most federal and professional standards require at least a weekly check of output constancy. Some institutions perform it daily.

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39
Q

The medical dosimetrist is a member of the radiation oncology team who:

  • has knowledge of characteristics and clinical relevance of treatment machines and equipment
  • is cognizant of procedures used in brachytherapy
  • has education and expertise necessary to generate radiation dose distributions and calculations in collaboration with medical physicist and radiation oncologist
  • all of the answers are correct
A

-all of the answers are correct

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40
Q

What is the approximate density of healthy lung tissue?

  • 0.30 g/cc
  • 0.95 g/cc
  • 1.00 g/cc
  • 1.03 g/cc
  • 1.65 g/cc
A

-0.30 g/cc

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41
Q

The approximate density of compact bone is:

  • 0.30 g/cc
  • 0.95 g/cc
  • 1.00 g/cc
  • 1.03 g/cc
  • 1.65 g/cc
A

-1.65 g/cc

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42
Q

Why is it preferred to use a small focal spot size, if possible when filming in the simulator for planning purposes?

-there will be less penumbra and better detail
-there will be less penumbra, but also less detail
-there will be better detail, but more penumbra
there will be less stress on the x-ray tube

A

-there will be less penumbra and better detail

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43
Q

In order to calculate a magnification factor, one would:

  • Divide SID by OID (or FFD/OFD)
  • subtract OID from SID
  • divide the object size by the image size
  • divide SID by SOD (FFD/FOD)
A
  • divide SID by SOD (FFD/FOD)
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44
Q

The process of leveling and windowing of CT images determines the:

  • spatial resolution
  • contrast
  • pixel size
  • matrix size
A

-contrast

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45
Q

FOV refers to:

  • focal object vector: the angle of the projection
  • fixed or variable-the choice of window
  • fine optic voxel-the best detail available
  • field of view-the diameter of the image
A

-field of view-the diameter of the image

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46
Q

Which of these tissues would have the highest CT number?

  • fat
  • muscle
  • brain tissue
  • cerebrospinal fluid
A

-muscle

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47
Q

Voxel size depends on:

  • field of view
  • matrix size
  • slice thickness
  • all are correct
A

-all are correct

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48
Q

A simulation is performed on a linear accelerator at 100 cm SAD and a field size of 12 x 15 cm. The treatment is delivered on a Co-60 treatment unit at 80 cm SAD. What is the field size at the isocenter?

  • 9.6 x 12.0 cm
  • 10.0 x 12.5 cm
  • 12.0 x 15.0 cm
  • 15.0 x 18.8 cm
  • 18.8 x 23.4 cm
A

-12.0 x 15.0 cm

field size at iso = field size at 100 cm SAD

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49
Q

A simulator film is taken at 130 cm SFD for making blocks to be used on a 100 cm SAD linear accelerator and an STD (source-tray-distance) of 65 cm. The treatment is rescheduled on an 80 cm SAD linear accelerator with an STD of 52cm. The SFD on the cutting apparatus must be set to:

  • 100.0 cm
  • 104.0 cm
  • 110.0 cm
  • 125.0 cm
  • 162.5 cm
A

-104.0 cm

52 cm STD/ 65 cm STD = 0.8
0.8 x 130 cm SFD = 104 cm SFD

80 cm SAD/ 100 cm SAD = 0.8
0.8 x 130 cm SFD = 104 cm SFD

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50
Q

An object on a radiograph measures 12 cm. The SOD distance is 90 cm and the SFD is 110 cm. The actual size of the object is:

  • 9.8 cm
  • 10.8 cm
  • 12.0 cm
  • 12.8 cm
  • 13.2 cm
A

-9.8 cm

90 / 110 = 0.81818 x 12 = 9.8

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51
Q

Vaginal brachytherapy (VBT) can be used to treat the vaginal cuff following surgery for endometrial cancer.

  • True
  • False
A

-True

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52
Q

Which of the following is an example of an orthogonal pair?

  • 0 and 180 degrees
  • 20 and 70 degrees
  • 40 and 115 degrees
  • 85 and 355 degrees
  • 90 and 270 degrees
A

-85 and 355 degrees

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53
Q

What is the approximate density of muscle?

  • 0.65 g/cc
  • 0.95 g/cc
  • 1.00 g/cc
  • 1.03 g/cc
  • 1.65 g/cc
A

-1.03 g/cc

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54
Q

The reference or “zero” CT number on the Hounsfield scale is for:

  • air
  • soft tissue
  • water
  • solid bone
A

-water

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55
Q

In situ cancers are cancers that have not penetrated the lining or basement membrane of the surface where they began.

  • True
  • False
A

-True

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56
Q

Which of the following CT parameters is NOT ideal for radiation therapy treatment planning?

  • large gantry aperture
  • small scan field of view
  • alignment lasers
  • flat couch top with provision for attaching immobilization devices
A

-small scan field of view

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57
Q

Digitally reconstructed radiographs (DRRs) are generated from:

  • The simulator’s fluoroscopy images
  • Ultrasound images
  • x-ray images
  • CT images
A

-CT images

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58
Q

CT slices are acquired in:

  • the coronal plane
  • the transverse plane
  • The sagittal plane
  • all planes
A

-the transverse plane

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59
Q

Radiation damage to the fetus resulting in severe birth defects would most often occur when radiation was delivered at which time post-fertilization?

  • 0 - 2 weeks
  • 3 - 12 weeks
  • 13 - 24 weeks
  • 23 - 32 weeks
  • 33 - 40 weeks
A

-3 - 12 weeks

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60
Q

Exposure is defined for ionization produced in:

  • water
  • tissue
  • air
  • fat
A

-air

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61
Q

An accidental whole body dose of 70 Gy would cause which of the following radiation syndromes?

  • hematopoietic
  • gastrointestinal
  • organogenic
  • cerebrovascular
A

-cerebrovascular

62
Q

Which of the following would be termed an “early effect” of radiation exposure?

  • genetic damage passed on to progeny
  • carcinogenesis
  • skin reaction to radiation
  • teratogenic effect on a fetus
A

-skin reaction to radiation

63
Q

The LD 50/60 for humans is approximately:

  • 1 Gy whole body dose
  • 3.5 Gy whole body dose
  • 8 Gy whole body dose
  • 12 Gy whole body dose
A

-3.5 Gy whole body dose

64
Q

Regarding linac output, AAPM’s TG40 report on QA recommends all of the following EXCEPT:

  • the daily output constancy check should be within 10% of the standard
  • the output is checked monthly by the physicist, and should be within 2% of the correct value
  • action should be taken if output parameters exceed tolerance
  • output must be within 2% of the required value during annual calibration
A

-the daily output constancy check should be within 10% of the standard

tolerance stated in TG40 is 3%. test is usually performed by therapists. if value exceeds tolerance, it must be checked by physicist, who will decide what action to be taken

65
Q

The equivalent square of a rectangular field with dimensions X x Y is:

  √ [4(X × Y)]
  2(X + Y) 
  2(X × Y) 
  (4 × X × Y)/(X + Y)
  2(X × Y)/(X + Y)
A

2(X × Y)/(X + Y)

66
Q

A patient is to be given a 4600 cGy midplane dose in 23 fractions by parallel opposed fields to the mediastinum. The dose to the spinal cord each fraction is 209 cGy. If a spinal cord block is added to the posterior field only, the dose to the spinal cord each fraction is 94 cGy. The spinal cord dose through the treatment course is limited to 4000 cGy. How many fractions must the posterior cord block be inserted?

  3 fractions 
  4 fractions 
  5 fractions 
  6 fractions 
  7 fractions
A

7 fractions

209 x 16 = 3344
94 x 7 = 658
3344+658 = 4002

209x23=4807
4807-4000=807
807/(209-94)=7

67
Q

Which of the following represents the ratio of dose at a given depth in a phantom to the dose at the same point at a depth of Dmax in a phantom?

  • SAR
  • OAR
  • TPR
  • TAR
  • TMR
68
Q

The industry standard format for transferring images between components of a network is called:

  • Digital Imaging Connections for Media (DICOM)
  • Digital Imaging and Communications in Medicine (DICOM)
  • Digital Integration of Computers and Media (DICOM)
  • Digital Imaging Computers in Medicine (DICOM)
A

-Digital Imaging and Communications in Medicine (DICOM)

69
Q

Percent depth dose (PDD) decreases with an increase in which of the following factors?

  • energy
  • depth
  • field size
  • SSD
70
Q

If not sealed, ionization chamber readings must be corrected for temperature and pressure because:

  • the walls of the chamber expand and shrink with temperature
  • the collecting electrodes electrical conductivity changes
  • the volume of air in the chamber changes
  • the mass of the air in the chamber changes
A

-the mass of the air in the chamber changes

71
Q

The spinal cord is approaching tolerance from opposing lateral 6 MV fields to the neck and a cord block will be placed. In evaluating the resulting calculations from the computer, it is noticed that 20% more monitor units are required for the same midplane dose. The medical dosimetrist should do which of the following?

  • advise the therapists of the change
  • check whether the block is too close to the calculation point
  • plan oblique fields off the cord
  • cease treatment due to risk of cord toxicity
A

-check whether the block is too close to the calculation point

72
Q

Record and verify systems have the ability to confirm which of the following?

  • patient position
  • treatment area
  • isocenter location
  • collimator angle and field size
  • All are correct
A

-collimator angle and field size

73
Q

Thimble chamber walls:

  • are made from high Z atomic number material
  • need be very thick
  • are air-equivalent
  • are made of ferromagnetic material
A

-are air-equivalent

74
Q

What anatomical region lies between vertebral body level C-4 through C-6?

  • Larynx
  • oropharnyx
  • hypopharnx
  • thyroid
A

-hypopharnx

75
Q

The anatomic location of the seminal vesicles is:

  • inferior to the prostate and angled anteriorly near the bladder
  • inferior to the prostate and angled posteriorly near the rectum
  • superior to the prostate and angles anteriorly near the bladder
  • superior to the prostate and angled posteriorly near the rectum
  • surrounding the proximal urethra
A

-superior to the prostate and angles anteriorly near the bladder

76
Q

The most important prognostic factor in breast cancer is the:

  • size of the tumor
  • age of the patient
  • status of the axillary nodes
  • quadrant of origin within the breast
  • menopausal status
A

-status of the axillary nodes

77
Q

Although they receive the same dose, some tissues exhibit acute radiation damage earlier than others because they have a:

  • smaller number of metabolizing cells
  • reduced blood flow
  • lower number of hypoxic cells
  • higher mitotic index
  • larger clonogenic cell population
A

-higher mitotic index

78
Q

Isotopes used in permanent implants are most frequently:

  • Iodine-125 and Gold-198
  • Gold-198 and Cesium-137
  • Cesium-137 and Radium-226
  • Radium-226 and Iodine-125
A

-Iodine-125 and Gold-198

79
Q

Geiger-Muller counters are useful as monitoring instruments because they:

  • are the detector of choice in high counting rate situations
  • are able to detect very small amounts of ionizing radiation
  • can detect neutron particles when thin windows are used
  • are able to determine the energy of incident radiation
  • all are correct
A

-are able to detect very small amounts of ionizing radiation

80
Q

The average life of a radioactive source with a decay constant ( λ) and a half-life (T1/2) is determined by:

  • 0.693/λ
  • 0.693/T½
  • 1/λ
  • λ x T½
  • 1/ T½
81
Q

The surface dose rate of a Sr-90 eye applicator was 4.5 cGy/sec on May 15. If a patient is to be treated 2 years later on May 15, what is the treatment time if 1000cGy is prescribed? (The half-life of Sr-90 is 28 years)

  • 202 seconds
  • 214 seconds
  • 222 seconds
  • 233 seconds
  • 242 seconds
A

-233 seconds

4.5(0.5)^(2/28)=4.28
1000/4.28=233

A=Aoe ^ -λt

82
Q

Parent and daughter radioactive isotopes are said to be in secular equilibrium when they:

  • are equal in atomic weight
  • have the same half-life
  • have a constant ratio of activity
  • emit equivalent gamma energies
  • have the same average life
A

-have a constant ratio of activity

83
Q

Which of the following is/are true about I-125?

  • half-life is 86.4 days
  • has high radiation protection requirements
  • has an energy of 0.412 MeV
  • decays exclusively by electron capture
  • all are correct
A

-decays exclusively by electron capture

84
Q

The radiation output and kVp of a simulator should be checked:

  • daily
  • monthly
  • annually
  • annually or after a major repair that may affect output
A

-annually or after a major repair that may affect output

85
Q

According to AAPMs TG-40, flatness and symmetry specifications for monthly QA of an x-ray beam are:

  • 2% flatness and 3% symmetry at a depth of 10cm
  • 3% flatness at dmax and 2% symmetry at a depth of 10cm
  • 2% flatness and symmetry at all depths
  • 2% flatness and symmetry at a depth of 10cm
A

-2% flatness and 3% symmetry at a depth of 10cm

86
Q

HDR brachytherapy can be used to treat which of the following sites?

  • nasopharynx
  • lung
  • esophagus
  • cervix
  • all are correct
A

-all are correct

87
Q

A physicist measures the output of a linac and finds it to be 4% low. The usual action taken by the physicist is:

  • to change the tables of output factors (cGy/MU for all collimator settings) to the new measured values
  • if the calibration is within 4%, nothing is changed
  • all patients treated within the last month must be notified
  • a potentiometer is adjusted so that one monitor chamber unit is equal to one cGy measured at the reference point
  • none are correct
A

-a potentiometer is adjusted so that one monitor chamber unit is equal to one cGy measured at the reference point

88
Q

Reconstruction refers to:

-the need to adjust pixel size for image quality

-the process of converting attenuation readings
from detectors to a digital image

  • the process of producing a reference film of the area scanned
  • the ability of detectors to clear a charge to be ready to recieve the next image
A

-the process of converting attenuation readings

from detectors to a digital image

89
Q

The CT number assigned to a given pixel:

  • is that of the lowest attenuating tissue in the voxel
  • is that of the highest attenuating tissue in the voxel
  • is the average attenuation of tissue in the voxel
  • is unrelated to tissue attenuation
A

-is the average attenuation of tissue in the voxel

90
Q

The decay constant for a radioactive source that has a half-life of 60 days is:

  • 0.012
  • 0.170
  • 0.662
  • 1.250
  • 6.580
A

-0.012

.693/60

T1/2=(ln2)/(λ)
λ =(ln2)/(30)=0.012

91
Q

Assuming the surgeon left clips in the tumor bed following an excision of a left breast tumor, a patient’s electron boost volume may be accurately localized by:

-clinically palpating the clips and scar

-outlining the scar with wire and measuring the
chest wall distance on tangential images

-taking orthogonal films and plotting the
location of the clips on the patient contour

-measuring the clip-to-skin depths using
tangential images

-all are correct

A

-taking orthogonal films and plotting the

location of the clips on the patient contour

92
Q

On the tenth treatment, the wedge shown for field #2 was left out. What is the total tumor dose given that day? (see picture)
4000cGy/20Fx…anterior beam weight=100, lateral beams weight=80, wedge factor=0.682 (each beam)

  • 171 cGy
  • 200 cGy
  • 229 cGy
  • 258 cGy
  • 264 cGy
A

-229 cGy

Total field weight = 260 Total cGy per day = 200cGy
Field 1 is 100(wt.)/260(total wt) = x/200 cGy = 77 cGy
Fields 2 and 3 (each field are the same weight):
80(wt each field)/260 (total wt) = x/200 cGy = 61.5 cGy per day per field.
Removing the wedge would increase the dose to 61.5 cGy/0.682 (WF)= 90 cGy - 61.5 = 29 cGy greater than the intended dose.
229 cGy was given that day.

(200/2.6=76.92)

93
Q

Typical beam flatness specifications for a linac photon beam are:

  • plus/minus 10% over the whole width for the beam measured in air at the isocenter
  • plus/minus 6% over 50% of the field width measured in water at dmax
  • plus/minus 3% over 80% of the field width measured in water at 10 cm depth
  • plus/minus 1% over 90% of the field width measured in air at the isocenter
  • plus/minus 20% over 50% of the field width measured in air at the isocenter
A

-plus/minus 3% over 80% of the field width measured in water at 10 cm depth

94
Q

Treatment according to a 100 cm SSD total CNS (craniospinal) technique requires non-divergent beam junctions. The dimensions of the brain portals are 30 cm (W) x 27 cm (L). The dimensions of the spine portals are 6 cm (W) x 40 cm (L). During treatment of the brain fields, the table and collimator should be rotated:

  • 5 degrees and 10 degrees, respectively
  • 7.6 degrees and 11.3 degrees, respectively
  • 8.5 degrees and 13.4 degrees, respectively
  • 10.2 degrees and 15.3 degrees, respectively
  • 12.5 degrees and 17.8 degrees, respectively
A
  • 7.6 degrees and 11.3 degrees, respectively

collimator=tan^1[0.5x27x(1/100)]=7.6
table=tan^-1[0.5x40x(1/100)]=11.3

95
Q

A patient is treated at a distance of 70 cm SSD with a source-to-diaphragm distance of 49.8 cm. The source size is 1.5 cm. What is the geometric penumbra at a depth of 7.5 cm? (see diagram)

  • 0.65 cm
  • 0.83 cm
  • 1.20 cm
  • 3.26 cm
  • 3.83 cm
A
  • 0.83 cm

1. 5(70+7.5-49.8)/49.8=0.83

96
Q

According to the National Council on Radiation Protection and Measurements (NCRP) guidelines (#116), the annual equivalent dose limit for the hands of an occupational worker in 1 year is:

  • 5 mSv (0.5 rem)
  • 15 mSv (1.5 rem)
  • 50 mSv (5.0 rem)
  • 150 mSv (15.0 rem)
  • 500 mSv (50.0 rem)
A
  • 500 mSv (50.0 rem)
97
Q

A radiation oncologist prescribes 4500 cGy in 25 fx to the 95% isodose line. The plan is normalized at the isocenter and is weighted 1.0 : 0.5 : 0.5. What is the dose in cGy to each field?

  • 90 : 45: 45
  • 90 : 60 : 60
  • 95 : 47 : 47
  • 102 : 51 : 51
  • 120 : 30 : 30
A
  • 95 : 47 : 47

4500/25=180
180/.95=190/2=95

4500cGY/.95=4736.8
4736.8/25=189.5
189.5/2=95
95*0.5=4795:47:47

98
Q

A 48 year old women reports to her gynecologist with the complaint of postcoital bleeding. She has eight children and first became pregnant at age 17. She admits that over the years she has been sexually active with many partners. With this history the gynecologist should be most concerned that the patient has what disease?

  • endometrial cancer
  • cervical cancer
  • ovarian cancer
  • vaginal cancer
A
  • cervical cancer
99
Q

Which of the following represents the ratio of the scatter dose at a given point in the phantom to a dose in free space at the same point?

  • SAR
  • OAR
  • TPR
  • TAR
  • TMR
100
Q

The depth dose characteristics of electron and photon beams are similar in which of the following ways?

  • they have a finite range of penetration
  • the percent surface dose is high
  • the percent surface dose increases as the
    energy increases
  • the percent depth dose increases as the beam
    energy increases
  • all are correct
A
  • the percent depth dose increases as the beam

energy increases

101
Q

The CT number for water is:

  • 0
  • 1
  • 1000
  • none of the above
102
Q

All of the following factors affect the percentage depth dose of an electron beam EXCEPT:

  • nominal energy
  • portal shape
  • type of flattening filter
  • effective SSD
A
  • type of flattening filter
103
Q

Adding a wedge filter to the primary beam:

  • results in beam softening and a decrease of local hot spots
  • will decrease skin dose if placed < 15 cm from the patient surface
  • can alter the depth dose distribution at large depths for high-energy photon beams
  • significantly decreases the TMR of photon beams at small depths (≤ 10 cm)
  • all are correct
A

-can alter the depth dose distribution at large depths for high-energy photon beams

104
Q

Dose to a point under a block in an irregular field can be calculated by using which of the following methods?

  • Ellis
  • Clarkson
  • Paterson-Parker
  • Quimby
  • all are correct
105
Q

Which of the following represents the off-axis factor?

  • dose at a point off-axis / dose at a depth of 10
    cm along central axis
  • dose at a point off-axis / dose at the same depth along central axis
  • dose at point of Dmax along the central axis / dose at point off-axis
  • (dose at point off-axis) x PDD
  • (dose at point off-axis) x TAR
A
  • dose at a point off-axis / dose at the same depth along central axis
106
Q

Backscatter factor (BSF) is identical to tissue-air ratio (TAR) at:

  • all depths
  • the isocenter
  • the surface
  • the depth of maximum dose
  • the exit surface
A
  • the depth of maximum dose
107
Q

An averaged ionization chamber reading for a 10 x 10 cm electron applicator is 98.5 and an averaged ionization chamber reading for an electron cutout in a 6 x 10 cm applicator is 92.4. What is the monitor unit setting if 200 cGy is prescribed to 90% and the 6 x 10 cm cut-out is utilized? (The output factor for 10 x 10 cm is 1 cGy/mu)

  • 208 MU
  • 217 MU
  • 222 MU
  • 237 MU
  • 244 MU
A
  • 237 MU

200(98.5/92.4)/0.90=237

108
Q

The most common site of metastatic disease for prostate cancer is:

  • liver
  • lung
  • bone
  • brain
109
Q

A 4-field isocentric isodose plan normalized to 100% at the isocenter shows the entire target volume encompassed by the 97% isodose line. The target volume is to receive 65 Gy; however, it is required that the dose be prescribed at the isocenter. The dose prescription should be written for:

  • 65 Gy to the target volume
  • 65 Gy to the isocenter
  • 65 Gy to the 97% isodose volume
  • 67 Gy to the isocenter
  • 67 Gy to the 97% isodose line
A
  • 67 Gy to the isocenter

65/.97

110
Q

The female cancer that most commonly spreads to the inguinal nodes is:

  • cervix
  • endometrium
  • vulva
  • ovary
111
Q

A dose of 30 Gy in 10 fractions to a depth of 7cm from a 6 MV single posterior field using an isocentric technique at 100cm SAD. The patient was incorrectly treated five times at 100 cm SSD. The approximate dose at 7 cm after five fractions is:

  • 11.6 Gy
  • 13.1 Gy
  • 13.8 Gy
  • 15.0 Gy
  • 16.3 Gy
A
  • 13.1 Gy
I1/I2 = d2^2/d1^2
15/x = 100^2/93^2
x = 13
112
Q

What is the purpose of a midline block when treating carcinoma of the cervix?

  • to block additional dose to the area that
    receives dose from brachytherapy
  • to block the internal and external iliac chain
  • to block the dose to the pelvic bones and
    femur
  • to prevent dose to the uterus to allow for future childbearing
A
  • to block additional dose to the area that

receives dose from brachytherapy

113
Q

The TAR is dependent on all the following EXCEPT:

  • beam energy
  • SSD
  • field size
  • depth
114
Q

Which of the following represents the ratio of the dose at a given point in a phantom to the dose in free space at the same point?

  • scatter-air ratio (SAR)
  • off-axis ratio
  • TPR
  • TAR
  • TMR
115
Q

For treatment of the prostate by two lateral arcs, an isodose distribution is approved to deliver 180 cGy to the 100% isodose line. The necessary monitor units for each arc field are calculated to be 121. Before the first treatment is delivered, the prescription is changed to deliver 200 cGy to the 95% line. The new monitor units per lateral arc field are:

  • 103
  • 115
  • 127
  • 134
  • 142
A
  • 142

90/1x= 121
100/.744 x .95= 142

116
Q

MRI can delineate the prostate more accurately than CT which over estimates the size of the gland.

  • True
  • False
117
Q

The accelerator component that injects electrons into the linear accelerator is:

  • a klystron
  • an electron gun
  • a high-voltage power supply
  • a bending magnet
  • a thyratron
A
  • an electron gun
118
Q

The function of a maze to a megavoltage treatment room is to:

-prevent neutron contamination at high
energies

  • keep operators as remote from the machine as
    possible
  • attenuate photons originating from the head
    of the linear accelerator
  • separate the primary and scattered
    components of the beam
  • minimize radiation levels at the door
A
  • minimize radiation levels at the door
119
Q

A gray is equal to:

  • 10 roentgen
  • 100 rad
  • 1000 rad
  • 1 Ci
120
Q

A periaortic field generally encompasses the vertebral processes laterally and extends from:

  • bottom of T-6 to the bottom of L-2
  • bottom of T-11 to the bottom of L-5
  • bottom of L-1 to the bottom of L-5
  • bottom of L-2 to the bottom of S-2
A
  • bottom of T-11 to the bottom of L-5
121
Q

According to the NCRP (#116) guidelines, the annual effective dose limit for continuous exposure to the whole body for the general public is:

  • 0.5 mSv (0.05 rem)
  • 1.0 mSv (0.10 rem)
  • 15.0 mSv (1.50 rem)
  • 50.0 mSv (5.00 rem)
  • 75.0 mSv (7.50 rem)
A
  • 1.0 mSv (0.10 rem)
122
Q

Isodose distributions for a 10 x 10cm 6 MV x-ray field in which only half of the beam intersects the phantom differ markedly from isodose distributions in which the entire beam intersects the phantom due to differences in:

  • off-axis beam hardening
  • lateral scatter
  • output factor
  • primary intensity
  • profile coefficients
A
  • lateral scatter
123
Q

Which of the following is the accelerator component that supplies pulses of high-power radiofrequency microwave energy to accelerate injected electrons?

  • klystron
  • electron gun
  • high-voltage power supply
  • bending magnet
  • thyratron
124
Q

The suggested dose for post-operative radiation to the prostate bed and surrounding nodes is higher than the suggested dose for radical (curative intent) treatment to the prostate and seminal vesicles.

  • True
  • False
125
Q

A website is a:

  • graphics software
  • collection of internet
  • software for creating web page
  • collection of web pages
A
  • collection of web pages
126
Q

The relative skin dose for a given energy photon beam:

  • decreases with increasing field size
  • increases with increasing field size
  • increases with decreasing field size
  • stays the same with any field size
  • must be calculated for each individual situation
A
  • increases with increasing field size
127
Q

Which of the following can be classified as indirectly ionizing radiation?

  • photons
  • electrons
  • alpha particles
  • protons
  • beta particles
128
Q

The linear attenuation coefficient for a 6MV beam is 0.51 cm-1. The thickness of a two half value layer block is:

  • 0.74 cm
  • 1.36 cm
  • 1.47 cm
  • 2.72 cm
  • 2.83 cm
A
  • 2.72 cm

1 half value layer = 0.693/0.51 = 1.3588
2 half value layers = 1.3588x2=2.72

129
Q

Bremsstrahlung radiation may be produced by:

  • neutrons striking low atomic number targets
  • electrons striking high atomic number targets
  • alpha particles striking low atomic number targets
  • protons striking low atomic number targets
  • all are correct
A
  • electrons striking high atomic number targets
130
Q

In a linear accelerator with a horizontally mounted waveguide, the component that directs the electron beam to the output window from the accelerator guide is:

  • a klystron
  • an electron gun
  • a high-voltage power supply
  • a bending magnet
  • a thyratron
A
  • a bending magnet
131
Q

Which of the following is closest to a dose regimen for early stage seminoma?

  • 10 Gy given in 20 fractions
  • 20 Gy given in 10 fractions
  • 30 Gy given in 20 fractions
  • 30 Gy given in 10 fractions
A
  • 20 Gy given in 10 fractions
132
Q

For x-rays generated at less than 250 kVp, there is a substantial increase of dose inside bone because of an increase in which of the following?

  • electron density relative to soft tissue
  • number of secondary photons from compton interactions
  • electron fluence arising from photoelectric absorption
  • backscatter effect at the bone/soft tissue interface
  • percentage of low-energy photons in the beam
A
  • electron fluence arising from photoelectric absorption
133
Q

In general, which of the following structures is more radioresistant?

  • small bowel
  • rectum
  • bladder
  • femoral heads
134
Q

Electron beam output factors are corrected for air gaps by using which of the following?

  • elongation depth
  • energy coefficient
  • equivalent thickness
  • virtual source distance
  • electron range
A

-virtual source distance

135
Q

The energy loss rate of a 10 MeV electron in water is approximately:

  • 0.51 MeV/cm
  • 0.69 MeV/cm
  • 1.25 MeV/cm
  • 2.00 MeV/cm
  • 3.33 MeV/cm
A
  • 2.00 MeV/cm
136
Q

The most significant effect of an air cavity on beam dosimetry in a megavoltage beam treatment is:

  • a change in the spectral energy distribution within the cavity
  • a reduction of primary photon transmission through the cavity
  • an enhanced absorption of dose in front of and beyond the cavity
  • a partial loss of electronic equilibrium at the cavity interface
A

-a partial loss of electronic equilibrium at the cavity interface

137
Q

If the linear attenuation coefficient for a given photon beam is 0.063 mm-1 lead, the corresponding half value layer is:

  • 0.04 mm lead
  • 0.09 mm lead
  • 9.50 mm lead
  • 11.0 mm lead
  • 13.00 mm lead
A
  • 11.0 mm lead

0. 693/0.063=11

138
Q

Pulsed microwaves are provided in a megavoltage linear accelerator by which of the following?

  • waveguide
  • klystron
  • thyratron
  • modulator
139
Q

Calculate the geometric penumbra based on the parameters listed below.
A patient is treated at a distance of 100 cm SSD with a source-to-diaphragm distance of 45 cm. The source size is 2 cm. What is the geometric penumbra at a depth of 5 cm?

  • 1.2 cm
  • 2.2 cm
  • 2.7 cm
  • 3.3 cm
A
  • 2.7 cm

S (SSD + d -SDD) / SDD

2(100+5-45)/45=2.7

140
Q

1 curie is equal to:

  • 106 becquerel
  • 103 becquerel
  • 3.7x10^10 becquerel
  • 37 becquerel
A
  • 3.7x10^10 becquerel
141
Q

Match the quantity with the corresponding unit:

Quantity - Rad, Ci, Roentgens, MeV

Unit - Radioactivity, Absorbed dose, electron beam, exposure

A 
Rad = absorbed dose
Ci = radioactivity
Roentgens = exposure
MeV = electron beam
142
Q

According to QUANTEC data, when sparing one parotid gland, the mean dose to the spared gland should not exceed _____ Gy.

  • 20
  • 30
  • 45
  • 50
143
Q

One roentgen corresponds to a charge of:

  • 3.7 x 10^10 disintegrations/sec
  • 2.58 x 10-4 coulomb/kg
  • 0.03 esu of electrostatic charge
  • 1 electron volt
A
  • 2.58 x 10-4 coulomb/kg
144
Q

The most common malignancy in children is:

  • medulloblastoma
  • retinomblastoma
  • acute lymphoblastic leukemia (ALL)
  • Wilm’s tumor
A
  • acute lymphoblastic leukemia (ALL)
145
Q

A monitor unit in a linac usually represents an absorbed dose of:

  • 1 Gy
  • 0.01 Gy
  • 100 Gy
  • 0.1 Gy
146
Q

The base of the prostate gland is superior and the apex is located at the inferior portion of the gland.

  • True
  • False
147
Q

Isobars are nuclides that have the same:

  • # of protons
  • atomic #
  • mass #
  • # of neutrons
148
Q

Match the charge with the particle: +1, -1, neutral

Electron
Positron
Photon
Neutron
Proton
A 
Electron = -1
Positron = +1
Photon = neutral
Neutron = neutral
Proton = +1
149
Q

If the muscle tissue is exposed to 50 roentgens of x-rays, this would produce an approximate dose of:

  • 50 rad
  • 50 Gy
  • 50 sievert
  • 50 becquerel
150
Q

A single fiber-optic cable has the bandwidth of thousands of copper telephone cables.

  • True
  • False
151
Q

Per the AAPM reports, there are certain QA tests that are required to be performed daily on IGRT systems.

  • True
  • False

Dosi Mock Exam Q's (2 decks)

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