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Principles And Practice Of Radiation Therapy 4th Edition By Charles M. -Test Bank

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Principles And Practice Of Radiation Therapy 4th Edition By Charles M. -Test Bank

Chapter 06: Medical Imaging

Washington & Leaver: Principles and Practice of Radiation Therapy, 4th Edition

 

MULTIPLE CHOICE

 

  1. Therapeutically, x-rays in the 40 to 300 kVp range are used for which of the following?
a. Treatment of skin cancers and other superficial tumors
b. The planning of a patients treatment on the simulator
c. Both of the above
d. None of the above

 

 

ANS:  C

Therapeutically, x-rays in the 40 to 300 kVp range are used for two principal purposes: (1) treatment of skin cancers and other superficial tumors and (2) the planning of a patients treatment on the simulator.

 

REF:   p. 108

 

  1. Components of a modern x-ray tube include which of the following?
a. Cathode filament
b. Rotating anode
c. Glass envelope
d. All of the above

 

 

ANS:  D

A typical x-ray tube includes all of those components listed. Other components include the protective housing and focusing cup.

 

REF:   pp. 106-108

 

  1. Interactions at the anode that produce x-rays may be described as which of the following?
a. Bremsstrahlung radiation
b. Characteristic radiation
c. Compton scattering
d. All of the above
e. Both a and b

 

 

ANS:  E

X-ray production in the anode occurs by only two methodsBremsstrahlung and characteristic radiation. Compton scatter, however, is a typical x-ray interaction within the tissues of the human body.

 

REF:   pp. 112-113

 

  1. Beam quality is affected by changes in which of the following?
a. kVp
b. Potential difference in the x-ray tube
c. Voltage
d. All of the above

 

 

ANS:  D

Beam quality is a descriptive term referring to the energy level of the photons in a beam. The energy level is modulated by changing kVp, also known as potential difference or voltage.

 

REF:   p. 113

 

  1. The quantity of photons in an x-ray beam is directly proportional to _____________.
a. kVp
b. anode temperature rating
c. tube current
d. filtration

 

 

ANS:  C

Although there is a relationship between kVp and photon quantity, the relationship is more exponential, not proportional. The anode temperature rating is irrelevant and filtration is indirectly related. As tube current increases, the number of photons in the beam increases in direct proportion.

 

REF:   p. 113

 

  1. Attenuation is the process by which an x-ray beam ___________________.
a. is focused
b. is reduced in intensity
c. diverges
d. exposes a film

 

 

ANS:  B

Attenuation is the process by which an x-ray beam is reduced in intensitythat is, has a reduction in the total number of photons. This may occur through a number of processes, including scatter and absorption.

 

REF:   p. 114

 

  1. Which of the following describes the predominant x-ray interaction in the diagnostic range?
a. Compton scatter
b. Photoelectric absorption
c. Coherent scatter
d. None of the above

 

 

ANS:  A

Compton scatter, or the Compton effect, is the predominant x-ray interaction in the diagnostic energy range.

 

REF:   p. 114

 

  1. Additive pathologies affect tissue density such that the affected anatomy may appear _________ on the radiograph.
a. lighter than normal
b. darker than normal
c. unchanged
d. hypoechoic

 

 

ANS:  A

Additive pathology adds to the tissues normal density, therefore increasing its ability to attenuate the x-ray beam. These areas of underexposure appear lighter on the resultant image.

 

REF:   p. 116

 

  1. Destructive pathologies include which of the following?
a. Pleural effusion
b. Atelectasis
c. Edema
d. Necrosis

 

 

ANS:  D

Destructive pathologies decrease the normal density of tissue and result in darker areas on the exposed film. Necrotic areas break down normal tissue, whereas pleural effusion, atelectasis, and edema all add to tissue density.

 

REF:   p. 116

 

  1. Which technical factor has the most effect on radiographic density?
a. mAs
b. kVp
c. Distance
d. All of the above

 

 

ANS:  D

Although mAs is typically modulated to change radiographic density, several factors have an equal or greater effect on density. kVp, distance, and other factors can have a tremendous effect on the image density.

 

REF:   pp. 116-117

 

  1. A quality radiograph taken at 100 cm using 20 mAs could be replicated at 50 cm using which of the following?
a. 15 mAs
b. 10 mAs
c. 7 mAs
d. 5 mAs

 

 

ANS:  D

According to the inverse squares law, if the distance is reduced by a factor of 2, the exposure necessary to produce the same image may be reduced by a factor of 4. Likewise, if distance is doubled, the output of the tube must be quadrupled.

 

REF:   p. 117

 

  1. Unlike digital radiography, conventional imaging media includes which of the following?
a. Film
b. Screens
c. Cassettes
d. All of the above

 

 

ANS:  D

Digital radiography uses no film, screens, or cassettes. Instead, the x-ray image is captured through a unique process that produces a completely digital image.

 

REF:   pp. 118-119

 

  1. Which of the following is responsible for transforming invisible x-rays into energy and then into visible light?
a. Grids
b. Glass envelop
c. Densitometer
d. Intensifying screens

 

 

ANS:  D

Through the process of phosphorescence, incoming x-rays transmitted through the patient interact with the intensifying screen to form visible light. This process is used to lower the total exposure necessary to produce an image of appropriate density.

 

REF:   p. 120

 

  1. Which of the following is an advantage of the photostimulatable phosphor plate over conventional x-ray image production?
a. Less radiating per exposure
b. Postprocessing manipulation of density and contrast
c. No need for radiographic grids
d. Higher spatial resolution

 

 

ANS:  B

Unlike conventional x-ray imaging, photostimulatable phosphor plates may be modified in terms of contrast and density even after processing. This is advantageous in that images produced with poor technical factors can be remedied with some modification after processing.

 

REF:   pp. 119-120

 

  1. Which of the following imaging receptors do not use light in capturing the latent image?
a. Flat panel detectors (FPDs)
b. TFTs
c. Film and screen

 

 

ANS:  A

FPDs require no visible light for image production. With the direct approach of FPDs, the x-rays passing through the patient are converted directly to an electrical signal that generates the digital image.

 

REF:   p. 119

 

  1. Which of the following may be used to reduce the amount of scatter radiation that reaches the image receptor?
a. Collimation
b. Grids
c. Filtration
d. All of the above
e. Both a and b

 

 

ANS:  E

Two significant means of reducing the amount of scatter radiation that reaches the film are: (1) collimation and (2) grid use. Collimation limits scatter production by minimizing the exposed tissue. Radiographic grids prevent scatter from reaching the film by absorbing the scatter in lead strips.

 

REF:   p. 122

 

  1. Image fusion as used in the production of positron emission tomography (PET) images may fuse together the PET images with the images of what other imaging modality?
a. Ultrasound
b. X-ray
c. Computed tomography (CT)
d. All of the above

 

 

ANS:  C

PET images are fused together with CT or magnetic resonance imaging (MRI) to produce the final images. By combining CT, MRI, or PET images in a way that overlays or electronically registers the information gathered from the same anatomical area, a better understanding of the structure and function of the pathology volume is possible.

 

REF:   p. 127

 

  1. Three-dimensional imaging using voxels is present in ____________.
a. MRI
b. CT
c. both of the above
d. neither of the above

 

 

ANS:  C

A voxel, used in MRI and CT scanning, is a volume element, meaning the voxel represents an entire volume of tissue, not just the surface of a two-dimensional slice.

 

REF:   p. 123

 

  1. In which of the following imaging procedures does an x-ray tube rotate rapidly around the patient?
a. CT
b. MRI
c. Fluoroscopy
d. Mammography

 

 

ANS:  A

During a CT scan, an x-ray tube rapidly rotating around the patient produces several views of the anatomy of concern. These views, or projections, are collected and combined to produce the final composite images.

 

REF:   p. 125

 

  1. Which of the following modalities does not use radiation in image production and acquisition?
a. CT
b. Nuclear medicine
c. MRI
d. Mammography

 

 

ANS:  C

Unlike x-rays, CT scans, and nuclear medicine, all of which use radiation, MRI uses a large magnet and radiofrequency waves to produce an image.

 

REF:   p. 126

 

  1. Because of the mobility of the prostate, which imaging modality is often used at the time of treatment to identify the position of the prostate?
a. Fluoroscopy
b. Ultrasound
c. MRI
d. Nuclear medicine

 

 

ANS:  B

Because the prostate gland moves relative to bony anatomy between the time of initial image acquisition for treatment planning and treatment delivery, real-time imaging, such as ultrasound, is commonly used to accurately localize the target at the time treatment is delivered. Localizing CT and x-ray images work in a similar fashion.

 

REF:   p. 128

 

  1. Who is the discovery of x-rays in 1895 credited to?
a. Wilhelm Conrad Roentgen
b. Theodor Boveri
c. Marie Curie
d. Sir Godfrey Hounsfield

 

 

ANS:  A

Roentgen discovered x-rays in 1895.

 

REF:   p. 107

 

  1. The emission of liberated electrons is the primary purpose of which of the following?
a. Anode
b. Cathode
c. Target
d. Generator

 

 

ANS:  B

It is the purpose of the tungsten cathode to generate the free electrons used in x-ray production.

 

REF:   pp. 109-110

 

Chapter 07: Treatment Delivery Equipment

Washington & Leaver: Principles and Practice of Radiation Therapy, 4th Edition

 

MULTIPLE CHOICE

 

  1. When did installation of the first fully isocentric linear accelerator in the United States occur?
a. 1942
b. 1952
c. 1961
d. 1979

 

 

ANS:  C

The first fully isocentric linear accelerator was manufactured and installed in the United States in 1961 by Varian Associates.

 

REF:   p. 135

 

  1. Which of the following is not found inside the head of a linear accelerator?
a. Ion chambers
b. Target
c. Accelerator structure
d. Bending magnet
e. Scattering foil

 

 

ANS:  C

The ion chambers, target, bending magnet, and scattering foil are found in the treatment head.

 

REF:   p. 141, figure 7-11, | pp. 142-143

 

  1. Which of the following best describes the major components of a linear accelerator?
a. Power supply, modulator, electron gun, accelerating waveguide, head, beryllium target
b. Power supply, modulator, klystron, electron gun, Ds, beryllium target
c. Power supply, electron gun, accelerating waveguide, head, doughnut accelerator structure
d. Modulator, klystron, electron gun, accelerator structure, waveguide, bending magnet

 

 

ANS:  D

The modulator is a component on higher energy beams. The klystron, which is the source of microwave power, delivers the microwaves via the waveguide. The electron gun in the gantry provides the source of electrons to be accelerated. The bending magnet helps focus the electrons to the target.

 

REF:   p. 137|p. 139

 

  1. Which of the following best describes the order in which electron bunches and the resulting x-rays travel through the head of a linear accelerator?
a. Bending magnet, dose chambers, target, flattening filter, wedge
b. Bending magnet, target, dose chambers, primary collimator, wedge, flattening filter
c. Bending magnet, target, primary collimator, flattening filter, wedge, dose chamber
d. Bending magnet, target, primary collimator, flattening filter, dose chamber, multileaf collimator
e. Bending magnet, dose chambers, target, flattening filter, primary collimator, multileaf collimator

 

 

ANS:  D

The bending magnet directs the electrons toward the target. The photons created are collimated by the primary target, then the flattening filter. Once past the flattening filter, the dose is measured and MLC can conform the beam.

 

REF:   pp. 140-141

 

  1. Which of the following is (are) true of electron beams?
a. Require a flattening filter to make the electron beam profile symmetric and flat
b. Require a scattering foil to make the electron beam profile symmetric and flat
c. Interact with the transmission target before leaving the exit window
d. a, b, and c
e. b and c

 

 

ANS:  B

When using electron beams, the target is removed and a scattering foil must be used to broaden the pencil-like beam.

 

REF:   p. 142

 

  1. The electron gun is similar to what part of an x-ray tube?
a. Anode
b. Rotating tungsten target
c. Cathode
d. Power supply

 

 

ANS:  C

An electron gun is similar to the filament on the cathode side of an x-ray tube.

 

REF:   p. 138

 

  1. A bending magnet in an accelerator may be used to do which of the following?
a. Help deflect microwave power
b. Deflect (bend) the electron beam
c. Gather stray electrons together in a bunch
d. Gather random paper clips

 

 

ANS:  B

A bending magnet deflects electrons 90 to 270 degrees toward the target.

 

REF:   p. 135

 

  1. In treatments using kilovoltage equipment, filters are used to ___________________.
a. filter low-energy x-rays
b. shield the patient from all radiation exposure
c. collimate the beam
d. increase quantity

 

 

ANS:  A

Aluminum or copper filters are used to filter out the low-energy x-rays, making the average energy of the beam higher.

 

REF:   p. 133

 

  1. Which of the following is the half-life of a cobalt 60 source?
a. 30 years
b. 1,600 years
c. 5.26 years
d. 74.2 days

 

 

ANS:  C

The half-life of a cobalt 60 source is 5.26 years. It is recommended that the source is replaced every 5.3 years.

 

REF:   p. 152

 

  1. The photon energy emitted by cobalt 60 is _______ MeV.
a. 1.36 and 1.01
b. .662 and 1.5
c. 1.00 and 1.5
d. 1.17 and 1.33

 

 

ANS:  D

The two gamma rays emitted are 1.17 and 1.33 MeV with an average energy of 1.25 MeV.

 

REF:   p. 152

 

  1. At what rate does the cobalt 60 source decay?
a. 1% per month
b. 2% per month
c. 3% per month
d. 5% per month

 

 

ANS:  A

The cobalt source decays at a rate of 1% per month. The physicist must adjust the dose monthly to accommodate the decay.

 

REF:   p. 152

 

  1. Which of the following limited the use of orthovoltage x-ray machines for radiation therapy?
a. Skin dose tolerance
b. Proton contamination
c. Excessive dose rate
d. Neutron contamination
e. The Nuclear Regulatory Commission requirement

 

 

ANS:  A

Orthovoltage units are limited to treat lesions of 2 to 3 cm.

 

REF:   p. 135

 

  1. The circulator in a linear accelerator does which of the following?
a. Mixes the hot and cold water to get the right temperature
b. Spins the electrons in the right direction
c. Conducts microwaves from the radiofrequency (RF) driver into the klystron
d. Isolates the klystron from reflected microwave power

 

 

ANS:  D

A circulator directs RF energy into the waveguides and prevents any reflected microwaves from returning to the klystron.

 

REF:   p. 138

 

  1. Of the following treatment units, which has the least amount of skin sparing?
a. Orthovoltage
b. Cobalt
c. 4 MV beam
d. 10 MV beam

 

 

ANS:  A

Orthovoltage has the least amount of skin sparing. Depth of maximum dose is deposited on the skin surface.

 

REF:   pp. 133-135

 

  1. When treating with electrons, the carousel rotates to place a _________________ in the beam to spread it out.
a. collimator
b. cone
c. scattering foil
d. flattening filter

 

 

ANS:  C

A scattering foil must be placed in the beams path. Otherwise, a patient would be treated with a pencil electron beam.

 

REF:   pp. 141-142

 

  1. Image-guided radiation therapy (IGRT) can be accomplished with ____________.
  2. ultrasound units
  3. computed tomography (CT) scanner

III. kV imager

  1. cone beam
  2. simulator
a. I, III, and IV
b. II, III, and V
c. I, II, III, and IV
d. III, IV, and V

 

 

ANS:  C

The rationale for IGRT is to image the patient prior to treatment, which can be accomplished with ultrasound, CT scanner, kV imager, and cone beam technology.

 

REF:   p. 148

 

  1. Orthovoltage x-ray machines have energies in the range of which of the following?
a. 1 kV to 100 kV
b. 150 kV to 500 kV
c. 200 MeV to 400 MeV
d. None of the above

 

 

ANS:  B

Orthovoltage therapy operates at 150 to 500 kV. Most equipment operates at 200 to 300 kV and is used for treating superficial lesions.

 

REF:   pp. 133-135

 

  1. A Van de Graaff machine __________________.
  2. is an electrostatic generator
  3. operates at 2 MV

III. operates a 200 kV

  1. uses a doughnut-shaped accelerator structure
a. I and II
b. II and IV
c. III and IV
d. I and IV

 

 

ANS:  A

  1. J. Van de Graaff developed the first electrostatic linear accelerator that operated with an energy of 2 MV.

 

REF:   pp. 133-135

 

  1. Lipowitz metal is composed of which of the following?
a. Tin, bismuth, lead, and cadmium
b. Lead, tungsten, and tin
c. Tin, bismuth, tungsten, and lead
d. Bismuth, cadmium, and lead

 

 

ANS:  A

Lipowitz metal, commonly called Cerrobend, is composed of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium.

 

REF:   p. 153

 

  1. When using multileaf collimation, which concerns need to be evaluated?
a. Penumbra between the leaves and the transmission of the leaves
b. Movement of MLCs during the treatment give variations in dose that need to be evaluated along with penumbra between the leaves
c. Movement of MLCs during treatment and interleaf transmission leakage
d. Penumbra at the end of the leaves and interleaf transmission leakage

 

 

ANS:  A

Penumbra at the end of the leaves and the interleaf transmission leakage must be measured by the physicist. Leakage may be on average of 2.5% and as high as 4%.

 

REF:   pp. 145-147

 

  1. Some of the more common medical accelerator hazards include which of the following?
  2. Incorrect dose delivered
  3. Dose delivered to wrong area

III. Machine collision

  1. Emergency off malfunction
a. I, II, and IV
b. II, III, and IV
c. I, III, and IV
d. I, II, and III

 

 

ANS:  D

The common medical accelerator hazards are incorrect dose delivered, dose to wrong area, and machine collisions. Double-checking patient information such as dose and area treated is a method to avoid these errors.

 

REF:   p. 152, table 7-4

 

  1. Depth of maximum dose for a 10-MV machine is how far below the skin surface?
a. 0.5 cm
b. 1.5 cm
c. 2.5 cm
d. 5 cm

 

 

ANS:  C

Depth of maximum dose for a 10-MV machine is 2.5 cm. Review all Dmax doses.

 

REF:   p. 153, table 7-5

 

  1. Depth of maximum dose for a 6-MV machine is how far below the skin surface?
a. 0.5 cm
b. 1.5 cm
c. 2.5 cm
d. 5 cm

 

 

ANS:  B

Depth of maximum dose for a 6-MV is 1.5 cm. Review all Dmax doses.

 

REF:   p. 153, table 7-5

 

  1. Depth of maximum dose for a 15-MV machine is how far below the skin surface?
a. 0.5 cm
b. 1.5 cm
c. 2.5 cm
d. 3 cm

 

 

ANS:  D

Depth of maximum dose for a 15-MV is 3 cm. Review all Dmax doses.

 

REF:   p. 153, table 7-5

 

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