Mock Exam 2 Flashcards
A patient receiving treatment to the head and neck region has experienced a skin reaction and mucositis at a total dose much lower than anticipated. The radiation oncologist requests an evaluation of the treatment. Which of the following steps should be taken?
- recalculate the treatment plan
- ensure that the depth dose, build-up region, wedge parameters, and other pertinent information for the treatment unit are correct
- review the treatment setup with the therapist
- recalculate the monitor unit settings
- all are correct
- all are correct
For megavoltage dosimetry, TLD can provide accuracy of:
- plus/minus 20%
- plus/minus 10%
- plus/minus 3%
- plus/minus 1%
- plus/minus 3%
With megavoltage film dosimetry, isodose curves can be measured to within:
- plus/minus 10%
- plus/minus 7%
- plus/minus 3%
- plus/minus 1%
- plus/minus 3%
In megavoltage therapy, typical use(s) of diodes is for:
- patient dosimetry
- beam scanning
- quality assurance
- all of the answers are correct
- all of the answers are correct
Which of the following is best suited for calibration of a megavoltage beam:
- diode detector
- thermoluminescence dosimetry
- film
- ionization chamber
- ionization chamber
The f-factor:
- is the roentgen to cGy conversion factor
- is greatest for high Z materials and low energy photons
- is 0.873 in air
- all of the answers are correct
- none of the answers are correct
- all of the answers are correct
Clinical application of MLC include which of the following?
- shaping of electron fields as a replacement for cerrobend blocks
- dynamic field shaping as a function of patient respiration
- field shaping without penumbra
- modulating beam intensity
- modulating beam intensity
The 104% isodose lines at the four corners of the target shown are due to the:
- inhomogeneity of the femur
- scatter from the femur
- horns of the beams
- weights of the lateral beams
- use of a wrong algorithm
-horns of the beams
Exposure is:
- the amount of energy in Joules/kg transferred from a photon beam to a material
- only defined for photons and charged particles below 3 MeV
- the charge liberated by photons in a given mass of air
- the absorbed dose multiplied by the quality factor
- None of the answers
-the charge liberated by photons in a given mass of air
The quantity that an ionization chamber actually measures is:
- roentgen
- gray
- charge
- kerma
- voltage
-charge
Geiger counters:
- are sensitive enough to detect individual photons or particles
- are less sensitive than ionization chambers
- are used to calibrate linac output
- operate on the principle of scintillation
-are sensitive enough to detect individual photons or particles
Which of the following is an advantage of using an MRI for treatment planning?
- there is no patient anatomy distortion on the images
- it is reliable for locating tumors within tissue
- it always displays an accurate external patient contour
- the brightness of the image is directly related to tissue density
-it is reliable for locating tumors within tissue
Based on clinical experiences with TBI before bone marrow transplantation and hemibody irradiation, the most important dose-limiting tissue is the:
- lens of the eye
- spinal cord
- lung
- skin
- liver
-lung
Dose volume histograms are useful to:
- identify the location of the global dose maximum in the volume treated
- optimize the radiation treatment in a reasonable time
- display location of uniform dose, low dose or high dose within a structure
- provide a graphic display of dose to the target
- all are correct
-provide a graphic display of dose to the target
OER for photon or electron therapy is:
- 1
- 2.5 to 3
- 10
- none of the answers are correct
- 2.5 to 3
Disregarding the effects of tissue inhomogeneity can result in errors in delivered dose that are:
- inversely dependent on photon energy
- directly dependent on the dimensions of the inhomogeneity
- dependent on the depth of the inhomogeneity
- all are correct
-all are correct
In the image below, the label “a” is referencing what structure?
- left atrium
- right atrium
- left ventricle
- right ventricle
- left ventricle
For an Ir-192 implant, it is found that the sources were 0.5 mg-Ra equivalent instead of 0.5 mCi. The exposure rate constant for Ir-192 is 4.69 R-cm/mCi-hr. What impact does this change have on the dose rate in the patient?
- increase
- decrease
- remain the same
- increase
Treatment planning for pediatric cancer patients assumes increased importance because:
- many pediatric patients are treated with curative intent
- children often receive chemotherapy which can interact with the complications of the radiation treatment
- growth disturbances due to radiation treatment are expected so exposed tissues must be kept to a minimum volume
- growth disturbances occur as a long term complication at relatively low doses (far below those required for control of many tumors)
- all are correct
-all are correct
A patient is treated to the left chest wall with electron arc therapy. In order to sharpen the distribution at the medial and lateral field borders, the medical dosimetrist should:
- place the isocenter at the skin surface
- shape the field with a cerrobend electron insert in the cone
- choose the highest electron beam energy available
- use a field size larger than the target defined by the physician
- shape the field on the skin surface with lead strips
-shape the field on the skin surface with lead strips
When an enface electron beam is used for chest wall irradiation, which of the following described the dose at the interface between the chest wall and lung?
- decreased due to reduced scatter from the lung
- decreased due to irregular surface contour effects
- increased due to an increase in the electron fluence
- increased due to a larger angle of electron scatter
- unchanged from that in a homogeneous phantom
-decreased due to reduced scatter from the lung
A beam degrader/spoiler is used in a photon beam for TBI in order to:
- decrease beam energy
- effectively hold lung transmission blocks close to the patient
- increase the surface dose to the patient
- decrease background radiation
- all are correct
-increase the surface dose to the patient
A diode dosimeter is:
- an ionization chamber coated with silicon
- a vacuum tube
- a solid state detector
- Baldwin Farmer chamber
-a solid state detector
Five beam arrangments are shown. Which one would yield the desired plan?
- arrangement 1
- arrangement 2
- arrangement 3
- arrangement 4
- arrangement 5
-arrangement 3
The closest dose limiting critical structure to the pituitary gland is:
- optic chiasm
- occipital lobe
- orbit
- lens
-optic chiasm
Which of the following modalities is most often used to treat small cell carcinoma?
- surgery + radiation
- radiation + chemotherapy
- chemotherapy + surgery
- surgery alone
- radiation alone
-radiation + chemotherapy
In High Dose Rate (HDR) brachytherapy, the dose rate at the treatment location is typically:
- 40 cGy/hr
- 100 cGy/hr
- 200 cGy/hr
- 1000 cGy/hr
- 100,000 cGy/hr
- 1000 cGy/hr
NRC regulations require that LDR brachytherapy calculations are checked for accuracy before:
- any sources are applied to the patient
- 10% of the prescribed dose is delivered
- 50% of the prescribed dose is delivered
- the sources are removed
- the sources are removed
A patient diagnosed with a T1N1M0 breast cancer would be classified as what stage?
- Stage IIIA
- Stage IIB
- Stage IIA
- Stage I
- Stage IIA
For 3D treatment planning of the pancreas, which of the following are dose-limiting structures that should be carefully observed?
- heart & stomach
- heart & large intestine
- stomach & small intestine
- small intestine & large intestine
-stomach & small intestine
According to the Law of Bergonie and Tribondeau, ionizing radiation is more effective against cells that are:
- actively mitotic, differentiated, and have a long mitotic future
- actively mitotic, differentiated, and have a short mitotic future
- not actively mitotic, undifferentiated, and have a long mitotic future
- actively mitotic, undifferentiated, and have a long mitotic future
-actively mitotic, undifferentiated, and have a long mitotic future
Gross structural changes in chromosomes resulting from radiation damage are referred to as:
- chromosome stickiness or clumping
- aberrations, lesions, or anomalies
- deletions and inversions
- interphase death or replication failure
-aberrations, lesions, or anomalies
The radiosensitive phase of cell cycle is:
- M
- G1
- M/G2
- G2
- S/G2
-M/G2
Hypoxic tumors, compared to well oxygenated normal tissues, for photon or electron irradiation:
- are more radioresistant
- are more radiosensitive
- exhibit no change in radiosensitivity
-are more radioresistant
The shoulder portion of the cell survival curve:
- indicates no damage to cells due to small radiation doses
- is the same for all types of radiation
- is absent for high LET radiation (i.e. alpha particles)
- references the dose required to reduce the cell population by 63%
- is defined as the number of critical targets the cell has to cause lethal damage
- is absent for high LET radiation (i.e. alpha particles)
According to the AAPM standards (TG40), when performing periodic linear accelerator quality assurance procedures, which of the following is the acceptable tolerance for light/radiation field coincidence?
- plus/minus 0.5mm
- plus/minus 1.0mm
- plus/minus 2.0mm
- plus/minus 3.0mm
- plus/minus 4.0mm
- plus/minus 2.0mm
The air-kerma strength of a point source of radium having an activity of 1 mg at a distance of 1 cm is:
- 8.25 cGy cm-squared/hr
- 8.25 R. cm-squared/hr
- 7.23 cGy cm-squared/hr
- 6.5 cGy cm-squared/hr
- 6.5 R. cm-squared/hr
- 7.23 cGy cm-squared/hr
Match the half-lives and the corresponding radioisotopes:
Isotopes = Ra-226, Pd-103, I-125, Au-198, Ir-192
1622 years 2.7 days 60 days 74 days 17 days
1622 years = Ra-226 2.7 days = Au-198 60 days = I-125 74 days = Ir-192 17 days = Pd-103
A remote after-loading device is useful in brachytherapy treatments because of the:
- long half-life of the radioisotope used
- advantages in reducing the radiation exposure to personnel involved in treatment
- high energy of the gamma rays from the after-loading unit
- improved cure rate
- reduction in patient discomfort
- advantages in reducing the radiation exposure to personnel involved in treatment
The half-life of I-125 is 60 days. In 6 months the activity of a source will be ______ of original.
- 70%
- 50%
- 1/8
- 5%
- 1/64
- 1/8
A Pd-103 seed with an activity of 1.4 mCi and exposure rate constant of 1.48 Rcm2/mCi.hr will have the following exposure rate at 1 meter?
- 20.7 R/hr
- 0.207 R/hr
- 0.207 mR/hr
- 2.07 mR/hr
- 20.7 mR/hr
- 0.207 mR/hr
0. 148 / 1.4 mCi
When treating the cervix using brachytherapy, which of the following is true regarding point A?
- 3 cm superior to the external cervical os in the plane of the tandem
- 5 cm lateral to the cervical canal, measured perpendicular to the tandem
- the point in which recieves 50% of the prescription dose
- the point of intersection of the uterine artery and the ureter in the paracervical triangle
- the point of intersection of the uterine artery and the ureter in the paracervical triangle
MRI/CT fusion is optimal in 3D treatment planning for brain tumors.
- True
- False
-True
All of the following QA tests are required to be performed on the day of an HDR implant EXCEPT:
- verify source activity used in planning
- complete source calibration
- verify correct date and time on the computer
- ensure door interlocks are functioning
-complete source calibration
The three planes in a patient are across the body, along the body in a lateral view, and along the body in an anterior view. (Think of the three views on a planning computer) Respectively, they are referred to as:
- axial, coronal, and sagittal
- coronal, axial, and sagittal
- axial, sagittal, and coronal
- sagittal, axial, and coronal
-axial, sagittal, and coronal
According to recent AAPM recommendations, a brachytherapy source must be specified in terms of:
- mg-Ra-equivalent
- effective activity
- Air Kerma Strength (AKS)
- Reference Air Kerma Rate (RAKR)
-Air Kerma Strength (AKS)
Radiation protectors:
- increase the radioresistance of cells to radiation
- protect (increase the radioresistance of) only the normal tissues
- move the NTCP (normal tissue complication probability) vs. dose curve to the left
- are very simple elements such as Ag or Na
-increase the radioresistance of cells to radiation
The approximate length of the rectum is ____cm.
- 7
- 11
- 15
- 22
- 15
The Quimby system specifies dose as:
- the maximum dose in the plane of treatment
- the minimum dose 2cm from the implant
- the average dose at the surface of the implant
- the uniform prescribed dose throughout the volume
- the maximum dose in the plane of treatment
How long does a temporary Ir-192 implant need to be left in place to deliver 3000cGy? The initial dose rate is 0.5 Gy/hr.
- 25 hours
- 1 day
- 4 days
- 2.5 days
- 2.5 days
What is the dose for a permanent implant using Pd-103? The initial dose rate is 4Gy/day.
- 125 Gy
- 98 Gy
- 68 Gy
- 200 Gy
- 98 Gy
4 x 1.44 x 17
With modern afterloading equipment:
- the point A dose must be obtained from standard Manchester tables
- the treatment time can be reduced by increasing source activity
- time, distance, and shielding safety measures no longer apply
- the dose distribution can be customized
- the dose distribution can be customized
Why is MRI NOT considered “radiographic imaging?”
- it uses digital technology
- it does not produce films
- electromagnetic radiation is not produced in the imaging process
- it does not use radiation capable of ionization
- it does not use radiation capable of ionization
