Dosi 1 Flashcards
Concerning the precision of treatment planning and delivery of treatment in radiation therapy, the greatest source of uncertainty is:
•The histology of the disease.
•Physical response data.
•Patient and organ motion during treatment.
•Linear accelerator calibration.
•Patient and organ motion during treatment.
An unsealed chamber used as a secondary dosimeter gives a reading of 101.0 for a 100 monitor unit exposure at a field size of 10 cm2. If the ambient temperature is 25 degrees C and the atmospheric pressure is 770 mm Hg, the corrected reading per monitor unit is:
A. 0.923.
B. 0.997.
C. 1.007.
D. 1.013
C. 1.007
HgP std =760mmHg
Pactual =770mmHg
Tstd=0°C =273.15 K
T actual=25°C=298.15
CorrectionFactor= (770/760)×( 273.15/298.15)
A patient is treated by using parällel opposed equally weighted fields at 80 cm source-to-surface distance (SSD) on a 4 MV linear accelerator to a total midplane dose of 60 Gy. The patient diameter is 20 cm. The field size is 15 x 15 cm2. The total dose at a depth of 1.2 cm is:
Depth (cm). 15 x 15 cm
1.2. 100.0
5. 83.7.
10. 63.6
15. 46.9
20. 34.1
25.0. 25
A. 62.6 Gy.
B. 64.7 Gy.
C. 66.5 Gy.
D. 68.1 Gy.
B. 64.7 Gy
AP=30 ( 100/63.6)
PA=30(37.1/63.6)
The correct source-to-tray distance on the therapy machine is 50 cm. If a block is constructed with the tray distance set at 40 cm, which of the following will result?
A. The blocked area will be too small.
B. The block could be in the wrong position on the tray.
C. The block divergence will not match the beam divergence.
D. The block will be too far from the patient.
A. The blocked area will be too small.
For a 4-field box technique, which of the following will deliver to femoral heads?
A.100 SSD, equal max dose to all fields
B.100 SSD, equal target dose to all fields
C.100 SAD, equal air dose to all fields
D.100 SAD, equal target dose to all fields
E.100 SAD, equal monitor unit setting for all fields
A.100 SSD, equal max dose to all fields
An individual receives a dose of 0.1 cGy from a gamma source and 0.05 cGy from neutrons.
The dose equivalent from both radiation sources IS:
A. 1.1 mSv
B. 1.5 mSv
C. 8.0 mSv
D. 11.0 mSv
11mSV
Gamma dose equivalent:
0.001Gy × 1= 0.001 Sv
Neutron dose equivalent: 0.0005Gy×20=0.01Sv
Step 3: Add the dose equivalents.
Total dose equivalent = 0.001 Sv+0.01Sv=
0.011Sv=11mSv
0.001Sv+0.01Sv=0.011Sv
The accelerator component that injects electrons into the linear accelerator is:
klystron
electron gun
high voltage power supply bending magnet
thyratron
electron gun
Which of the following will change the buildup in a high energy beam?
(1) use of large field sizes on a linear accelerator with resulting electron contamination
(2) placement of the diaphragm or treatment cone greater than 20 cm from the skin surface
(3) placement of bolus material on the skin surface.
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(A) (1), (2), and (3) only are correct.
Tissue-air ratio (TAR) is dependent on:
(1) beam energy
(2) depth
(3) field size
(4) source-surface distance
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(A) (1), (2), and (3) only are correct.
When the equivalent square of a rectangular field is calculated, the result is less accurate when the:
(A) sides of the rectangular field are not vastly different.
(B) areas of the two fields are similar.
(C) field has an elongation ratio of 2
(D) beam energy is greater than 6 MV.
(E) perimeter of the two fields is the same.
C field has an elongation ratio of 2
Parallel opposing fields are used to deliver 5000 cGy in 25 fractions to the isocenter, located at mid-depth of 10 cm. The TAR at zero field size at 10 cm depth is 0.534 and the average SAR after irregular field calculation is 0.195. The tray factor is 0.939, air dose rate is 219.2 cGy/min and the timer correction is +0.02 min. Calculate the timer setting for each field.
(A) 0.56 min
(B) 0.65 min
(C) 0.69 min
(D) 1.12 min
(E) 1.35 min
C) 0.69 min
A 4 MV linear accelerator is calibrated to deliver 1 cGy per monitor unit in a phantom at depth with 80 cm SSD and 10 x 10 cm field size. [SEE TABLES] The dose rate to a
(A) 0.990 cGy per monitor unit.
(B) 0.996 cGy per monitor unit.
(C) 1.000 cGy per monitor unit.
(D) 1.005 cGy per monitor unit.
(E) 1.020 cGy per monitor unit.
(D) 1.005 cGy per monitor unit.
An orthovoltage beam is used to deliver 350 cGy to a depth of 5 cm. Calculate the timer setting for an SSD of 52 cm given the following information:
Exposure rate = 128 R/min at 50 cm SSD “cGy/R” factor = 0.95 cGy/R
Backscatter factor = 1.17
% depth dose at 5 cm = 63%
Timer error = 0
A.3.61
B.3.71
C 4.06
D.4.22
E.4.34
D. 4.22
A patient is prescribed for 70.20 Gy in 39 fractions, using a bilateral arc technique. The output factor equals 1.00 cGy/MU. Using the data provided below, the monitor unit setting for the left arc is:
RIGHT ARC Gantry
Angle TMR
210. .748
230 .672
250 .587
270 .563
290 .591
310 .672
330 .728
LEFT ARC Gantry
Angle TMR
30 .752
50 .679
70 .591
90 .563
110 .587
130 .672
150 .748
(A) 107
(B) 137
(C) 141
(D) 274
(E) 282.
(B) 137
Which of the following represents the ratio of dose at a given point in a phantom to the dose at the same point at depth of maximum in the phantom?
(A) scatter-air ratio
(B) off-axis ratio
(C) tissue-phantom ratio
(D) tissue-air ratio
(E) tissue-maximum ratio
(E) tissue-maximum ratio
Which of the following represents the ratio of dose at a given point in a phantom to the dose at the same point at depth of maximum in the phantom?
(A) scatter-air ratio
(B) off-axis ratio
(C) tissue-phantom ratio
(D) tissue-air ratio
(E) tissue-maximum ratio
(E) tissue-maximum ratio
A patient is supine for treatment of the thoracic spine from a posterior field 7 cm wide, 25 cm long at 100 cm SAD, 94 cm SSD. This field must be matched at the isocenter to a previously treated posterior spine field 7 cm wide and 15 cm long also at 100 cm SAD, 94 cm SSD. The patient’s anterior posterior separation throughout the treatment region is 23 cm. The gap between the fields measured on the patient’s anterior skin is:
(A) 1.2 cm
(B) 2.4 cm
(C) 3.4 cm
(D) 4.0 cm
(E) 6.8 cm
A. 1.2
Gap formula
(L1/2 * d/SAD) + ( L2/2 * d/SAD)
(25/2 * 6/100)+( 15/2*6/100)
0.75+0.45= 1.2
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?
(A) scatter-air ratio
(B) off-axis ratio
(C) tissue-phantom ratio
(D) tissue-air ratio
(E) tissue-maximum ratio
(A) scatter-air ratio
The most radiosensitive phase for mental retardation in the fetus from RT accidental exposure is:
A. 0-7 weeks.
B. 8-15 weeks.
C. 16-24 weeks.
D. more than 25 weeks.
B. 8-15 weeks.
The most radiosensitive phase for mental retardation in the fetus from RT accidental exposure is:
A. 0-7 weeks.
B. 8-15 weeks.
C. 16-24 weeks.
D. more than 25 weeks.
B. 8-15 weeks.
A radioactive source is considered to be isotropic if it exhibits which of the following characteristics?
A. Summation of the total dose is proportional to the point source.
B. Dose at depth is variable in all directions based on the placement of the source.
C. Intensity around the source is equal in all directions.
D. The total dose is a function of the size of the source calculated based on kerma rate.
C. Intensity around the source is equal in all directions
For which of the following malignancies has hypofractionation radiation therapy been shown to significantly improve local control compared with standard fractionation?
A. low-grade sarcomas
B. adult high-grade gliomas
C. head and neck cancer
D. inflammatory breast cancer
C. head and neck cancer
As per the American Brachytherapy Society guidelines, the dose required to treat uveal melanomas with Iodine-125 plaque brachytherapy is:
A. 50Gy prescribed to 0.5cm depth.
B. 65Gy prescribed to apex.
C. 85Gy prescribed to apex.
D. 100 Gy prescribed to 0.5cm depth.
C. 85Gy prescribed to apex.
Which of the following statements is true for clinical electron beams?
A. The mean energy decreases as a quadratic function of depth.
B. The maximum energy is the same as the most probable energy.
C. The surface dose is inversely proportional to the electron beam energy.
D. The most probable energy is a function of the practical range (Rp).
D. The most probable energy is a function of the practical range (Rp).
Which of the following statements is true for clinical electron beams?
A. The mean energy decreases as a quadratic function of depth.
B. The maximum energy is the same as the most probable energy.
C. The surface dose is inversely proportional to the electron beam energy.
D. The most probable energy is a function of the practical range (Rp).
D. The most probable energy is a function of the practical range (Rp).
In order to avoid a 5% risk of necrosis at 5 years, what dose should the structures outlined not exceed?
Femoral heads
A. 42 Gy
B. 52 Gy
C. 62 Gy
D. 72 Gy
B. 52 Gy
According to QUANTEC guidelines, the dose limit to the spinal cord using conventional fractionation with a 0.2% rate of myelopathy is:
A. Dmax = 50 Gy Including full cord cross-section
B. Dmax = 45 Gy Including full cord cross-section
C. Dmax = 50 Gy Including partial cord cross-section
D. Dmax = 45 Gy Including partial cord cross-section
A. Dmax = 50 Gy Including full cord cross-section
A patient arrives to begin radiotherapy three weeks after the treatment plan was completed when it is determined that the patient has gained considerable weight and there is increased girth over the treatment area, the CMD should:
A. inform the radiation oncologist that there is an apparent change in the patient’s size and a new treatment plan
may be needed.
B. treat the patient as planned and then notify the radiation oncologist.
C. make arrangements for the patient to see the department’s medical dietician.
D. advise the radiation therapy technologists to monitor the patient for any adverse effects.
A. inform the radiation oncologist that there is an apparent change in the patient’s size and a new treatment plan
may be needed.
Presence of which of the following viruses indicates a favorable prognosis in patients with oropharyngeal cancer?
A. Human papilloma virus
B. Herpes simplex virus
C. Coxsackievirus
D. Epstein Barr virus
A. Human papilloma virus
According to AAPM TG Report #142, which of the following tests should be performed daily on a linear accelerator?
A. constancy factor of energy
B. beam profile constancy
C. optical distance indicator
D. respiratory gating
C. optical distance indicator
A craniospinal patient is setup with conventional photon CSI simulation. The spine field is setup with an SSD of 100 cm
and a field size of 5 x 26 cm. The whole cranium field has a field size of 22 x 18 cm at 100 cm SAD. relationships below correctly reflects the angle of rotation to be applied to the treatment couch?
A. Tan-1 13/100
B. Tan-1 11/100
C. Tan-1 9/100
D. Tan-1 5/100
C. Tan-1 9/100
Which of the
Rationale: the couch angle is calculated from the length of the adjacent jaw from the whole brain treatment field. The inferior (adjacent) jaw = 9 cm. Tan-1 adj. jaw/SAD = Tan-1 9/100 = couch angle.
Which of the following is a type of computer operating system sometimes used for radiotherapy planning?
A. DICOM-RT
B. ASCII Code
C. Unix
D. PACS
C. Unix
ICRU Report #38 and Report #58 both define total reference air kerma as a method of reporting dose in brachytherapy. Which of the following descriptors illustrates total reference air kerma (TRAK)?
A. the sum of the reference air kerma and the duration of the application for each source
B. the product of the reference air kerma and the duration of the application for each source
C. the sum of the products of the reference air kerma rate and the duration of the application for each source
D. the product of the sums of the reference air kerma rate and the duration of the application for each source
C. the sum of the products of the reference air kerma rate and the duration of the application for each source
What is the fundamental unit of data in a computer called?
A. bit
B. byte
C. pixel
D. voxel
B. byte
A new software release is installed on your treatment planning system and all required beam data has been updated for your treatment unit. Before using the system for routine clinical use, it is prudent to:
A. verify DICOM transfer connectivity is established.
B. calculate and plot isodose distributions in penumbra region for a range of field sizes.
C. print and compare scaled source parameters.
D. check the calculation of doses in and beyond heterogeneities.
D. check the calculation of doses in and beyond heterogeneities.
A patient is simulated head first supine for a left humerus irradiation with an isocentric technique. The AP BEV was used to create the field borders and blocking. The PA projection is a parallel opposed beam of the AP projection. The field size of the PA field, however, was enlarged to accommodate the same volume of the humerus. A reason for this is that the isocenter was placed in a coronal plane:
A. lateral to the humerus.
B. centered on the humerus.
C. posterior to the humerus.
D. anterior to the humerus
D. anterior to the humerus
Rationale: Isocenter is anterior to the target volume, and fs is defined at isoc, the field divergence will be larger than at the stated field size when encompassing the humerus. This same field, from the PA direction, will be smaller than the stated field size at isocenter when encompassing the target volume, thus requiring the stated F.S. at the depth of isocenter to be larger from the PA direction so that it is the same size of the AP at the depth of the humerus
In the production of characteristic X rays, which of the following is the type of energy an incident electron must have to strip an electron from an atom?
A. transient absorption
B. linear attenuation
C. critical absorption
D. secular activation
C. critical absorption
In the production of characteristic X-rays, the incident electron must have energy equal to or greater than the binding energy of the inner-shell electron in the atom. The correct term for this energy is known as critical absorption, which refers to the energy threshold needed to eject an electron from its orbit, leading to the emission of characteristic X-rays.
The tilt that an isodose curve makes with the central ray of a beam at a specified depth is called the:
A. wedge factor
B. hinge angle
C. edge effect
D. wedge angle
D. wedge angle
The wedge angle is the angle formed between the isodose curve and the horizontal plane at a specific depth, typically at the 50% isodose line. It is used to shape the dose distribution when treating irregularly shaped target areas or to compensate for tissue inhomogeneities.
The standard of care primary treatment for cancer of the parotid gland is:
A. photon beam radiotherapy
B. neutron beam radiotherapy
C. chemotherapy
D. surgery
D. surgery
- According to QUANTEC guidelines, in order to avoid a 5% risk of dysfunction, less than 55% of the volume of the structures ( both kidneys) outlined should receive what dose?
A. 6Gy
B. 12 Gy
C. 24 Gy
D. 32 Gy
B. 12 Gy
- According to QUANTEC guidelines, in order to avoid a 5% risk of dysfunction, less than 55% of the volume of the structures ( both kidneys) outlined should receive what dose?
A. 6Gy
B. 12 Gy
C. 24 Gy
D. 32 Gy
B. 12 Gy
A radiation oncologist is designing a phase I clinical trial for lung cancer. Which of the following scenarios is an example of such a trial?
A. Patients are treated in sequential groups with each subsequent group receiving a higher dose of Radiation
Therapy until toxicity is noted and maximum tolerance is determined.
B. Patients are assigned into two separate groups A and B. Group A is to receive Radiation Therapy once daily and
Group B is to receive Radiation Therapy two times a day (BID).
C. Testing of a drug in combination with Radiation Therapy (concurrent chemoradiation) is used to compare the
survival of this group with patients that previously received radiotherapy alone.
D. The radiation oncologist states that the study is being done to study the long-term side effects of a drug used in
combination with Radiation Therapy.
A. Patients are treated in sequential groups with each subsequent group receiving a higher dose of Radiation
Therapy until toxicity is noted and maximum tolerance is determined.
Prescriptions for dose and monitor unit calculations for intensity modulated radiation therapy (IMRT) treatment planning systems should be based on dose to:
A. a single voxel.
B. an off-axis point.
C. target volumes.
D. the isocenter.
Rationale: ICRU Report #83
C. target volumes.
Prescriptions for dose and monitor unit calculations for intensity modulated radiation therapy (IMRT) treatment planning systems should be based on dose to:
A. a single voxel.
B. an off-axis point.
C. target volumes.
D. the isocenter.
Rationale: ICRU Report #83
C. target volumes.
Which of the following describes a counting system used by computers that involve the digits 0 and 1?
A. decimal system
B. binary system
C. hexadecimal system
D. octal system
B. binary system
The 2010 ICRU Report # 83 recommends the use of the homogeneity index (HI) to assess the over and under dosages within the target volume. Which of the following descriptions best characterizes the homogeneity index?
HI = [(D2 – D98) / D50]
A. An HI value of zero is not desirable for IMRT planning.
B. The HI is used to determine the uniformity of dose distribution with the largest target volume.
C. A larger HI value indicates a more inhomogeneous dose distribution
D. A smaller HI value indicates a more inhomogeneous dose distribution.
C. A larger HI value indicates a more inhomogeneous dose distribution
Homogeneity Index (HI) is calculated as
HI = [(D2 – D98) / D50]
where:
D2 is the dose received by 2% of the target volume (indicating the maximum dose).
D98 is the dose received by 98% of the target volume (indicating the minimum dose).
D 50 is the median dose (dose received by 50% of the target volume).
A larger HI indicates a wider range between the high and low doses within the target volume, meaning a more inhomogeneous dose distribution.
Conversely, a smaller HI value would indicate a more uniform, or homogeneous, dose distribution.
Which of the following is the most accurate algorithm for electron beam calculations?
A. Collapsed cone convolution
B. Monte Carlo
C. Clarkson
D. Pencil beam
B. Monte Carlo
The cGy as a unit of absorbed dose:
A. is equal to 100 Gy.
B. only applies in water.
C. may also be used as a unit for KERMA.
D. is only defined for photon beams.
C. may also be used as a unit for KERMA.
Internal conversion is followed by emission of:
A. protons.
B. positrons.
C. auger electrons.
D. neutrinos.
C. auger electrons.
Explanation: When internal conversion occurs, an excited nucleus interacts with an orbital electron, ejecting it from the atom. This leaves a vacancy in the electron shell, which is then filled by another electron from a higher energy level, releasing the excess energy as an Auger electron.
Key points about internal conversion:
No gamma ray emission: Unlike typical gamma decay, internal conversion does not emit a gamma ray photon.
Electron emission: The emitted electron is called a conversion electron.
Auger cascade: The filling of the vacancy can lead to a cascade of Auger electrons as other electrons from higher energy levels fill the gap
The off-axis factor (OAF) is dependent on which of the following?
A. The degree of tilt the isodose curve endures at the central ray.
B.An isodose curve profile at a depth of 10cm.
C.The lateral distance between the 90% and 20% isodose lines at Dmax.
D. Distance of a point from the central axis.
D. Distance of a point from the central axis
A computer network that is limited to a single division or small group in one geographical location is called a:
A. Wide Area Network
B. Distributed Switch Network
C. Local Area Network
D. Discrete Network
C. Local Area Network
From the techniques listed below, select the LEAST desirable method for treating a 3.0cm non-secreting pituitary adenoma.
A. opposed lateral fields
B. opposed laterals plus a vertex field
C. non-coplanar fields
D. stereotactic radiosurgery
A. opposed lateral fields
DICOM allows:
A. Imaging modalities and PACS to communicate in the same language.
B.A networked group of computers to manage digital images.
C. X-ray absorber material and a charged coupled device to form an image.
D.Improved image quality in digital portal films.
A. Imaging modalities and PACS to communicate in the same language.
The Planning Target Volume provides margin around the Gross Tumor Volume and/or Clinical Tumor Volume to compensate for which of the following?
A. positive margins at tumor bed.
B. inconsistencies in physician drawing.
C. dose fall off.
D. variations in treatment setup.
D. variations in treatment setup.
The Planning Target Volume provides margin around the Gross Tumor Volume and/or Clinical Tumor Volume to compensate for which of the following?
A. positive margins at tumor bed.
B. inconsistencies in physician drawing.
C. dose fall off.
D. variations in treatment setup.
D. variations in treatment setup.
Which of the following concepts of 3-dimensional conformal radiotherapy is/are correctly defined?
A. Differential DVH: Plot of a volume of a structure receiving a certain dose as a function of dose
B. BEV: display of target and normal tissues parallel to the beam
C. GTV: gross demonstrable extent of tumor
D. PTV: true extent and location of disease
C. GTV: gross demonstrable extent of tumor
Which statement is true about the benefits of PET-CT for use in Radiation Oncology treatment planning?
A. PET images show chemical or metabolic activity within the body.
B. PET images provide superior anatomical definition over CT images.
C. PET images have an accuracy of 10-15 mm for anatomical location.
D. PET imaging is ideal for diabetic patients.
A. PET images show chemical or metabolic activity within the body.
In megavoltage therapy, all beam modifying devices should be placed at least 20.0 cm from the patient’s skin surface because:
A. the increase in half value layer (HVL) adversely affects skin dose.
B. alpha particles will not reach the skin’s surface
C. percentage depth dose (PDD) is increased
D. secondary electrons are scattered before reaching the patient
D. secondary electrons are scattered before reaching the patient
Technical considerations in the post-operative treatment of high-grade soft tissue sarcomas of the extremities with external beam radiation should include:
A. circumferential tissue sparing in the width of the field
B. eliminating any shielding in the treatment field
C. treating the tumor bed with minimal margins only
D. using daily fractional doses of 250 cGy or more
A. circumferential tissue sparing in the width of the field
Technical considerations in the post-operative treatment of high-grade soft tissue sarcomas of the extremities with external beam radiation should include:
A. circumferential tissue sparing in the width of the field
B. eliminating any shielding in the treatment field
C. treating the tumor bed with minimal margins only
D. using daily fractional doses of 250 cGy or more
A. circumferential tissue sparing in the width of the field
For electron therapy, increasing the gap between cerrobend cut-out, placed at the end of the cone, and the treatment surface of the patient results in:
A. a decrease in the physical penumbra at the patient surface
B. a decrease of electron energy to achieve the same PDD
C. an increase in the bremsstrahlung tail on the depth dose curve
D. an increase in the monitor units to achieve the same dose
D. an increase in the monitor units to achieve the same dose
For external beam radiation, the use of multiple photon beams (3 or more) versus a single photon beam will:
A. decrease the ratio of the tumor dose to the normal tissue dose
B. decrease the amount of scatter dose to the tissue outside the irradiated volume
C. increase the dose to treatment volume
D. increase the homogeneity within the target
D. increase the homogeneity within the target
When acquiring cone beam computerized tomography (CBCT) images, the dose to sensitive structures can be reduced by?
A. adjusting the collimator blades to reduce the volume of the patient being irradiated.
B. using the x-ray technique to best match the clinical task.
C. selecting the direction of the kV beam to avoid sensitive structures.
D. decreasing the dose rate.
A. adjusting the collimator blades to reduce the volume of the patient being irradiated.
electron beam therapy, if an air gap results in beam obliquity and is not accounted for in the plan, it:
A. shifts the dmax deeper
B. shifts dmax towards the surface
C. changes the degree of lower isodose bulge
D. decreases side scatter at dmax
B. shifts dmax towards the surface
When treating chest wall tumors with multiple electron fields, which of the following considerations should be taken?
A. angle the beams towards each other
B. use the same electron energies for field matching
C. feather the junctions periodically
D. overlap the fields purposely to account for motion
C. feather the junctions periodically
Which of the following criteria is information required to be included in the written directive for the medical use of radioactive materials?
A. verification methods for confirming the patient identity
B. the x, y and z coordinate locations of the radioactive source
C. the total patient exposure time to the source
D. authentication of the source license
C. the total patient exposure time to the source
Using non-coplanar beams and IMRT techniques to design a treatment plan of the pituitary gland is advantageous over traditional 3D techniques in reducing the dose to the:
A. optic chiasm and temporal lobes.
B. optic chiasm and cochlea.
C. temporal lobes and brainstem.
D. brainstem and cerebrum.
A. optic chiasm and temporal lobes
The use of stereotactic radiotherapy is frequently used to treat which of the following cancers of the thorax?
A. small cell lung cancer
B. non-small cell lung cancer
C. thymoma
D. mesothelioma
B. non-small cell lung cancer
When using radiotherapy for SBRT treatment of liver disease, the most dose-limiting surrounding normal tissue to be considered is:
A. the spinal cord
B. the kidneys
C. the bowel
D. normal liver
D. normal liver
Which of the following choices best reflects the role of radiation therapy in the treatment of cutaneous melanoma?
A. definitive treatment of primary site
B. palliative treatment to metastatic site
C. adjuvant treatment following surgical resection
D. definitive treatment for regional recurrence
C. adjuvant treatment following surgical resection
When viewing the grayscale image on the computer screen, if the window range extends from (+400) to (-500), then the level is equal to:
A. -500
B. -50
C. +400
D. +900
B. -50
Level= (+400)+(−500)/2= −100/2 =-50
Which of the following Window/Level settings represents a grayscale image appropriate for viewing the lung on a CT scan?
A. Level = -700, Window = 1000
B. Level = 250, Window = 500
C. Level = 40, Window = 500
D. Level = 40, Window = 120
A. Level = -700, Window = 1000
Based on the RTOG published guidelines for contouring the pelvis, the femoral structure should include the head of the femur and extend inferiorly to:
A. the inferior aspect of the lesser trochanter.
B. the lowest level of the ischial tuberosities.
C. 3 cm inferior to the head of the femur.
D. the lowest level on which you can visualize the penile bulb.
B. the lowest level of the ischial tuberosities.
Based on the RTOG published guidelines for contouring the pelvis, the bowel, including small bowel as well as the large bowel and colon, should be contoured as a single bowel bag when performing the treatment planning for which of the following type of cancer?
A. pancreatic
B. rectal
C. uterine
D. anal
C. uterine
A seminoma is being treated with radiation using conventional AP/PA treatment fields. structures must be localized and monitored if a standard dose for seminoma is employed?
A. liver
B. kidneys
C. spinal cord
D. small bowel
B. kidneys
Which of the following energies would have the highest skin dose?
A. 4MeV
B. 6MV
C. 10MV
D. 16 MeV
D. 16 MeV
The process of creating beam intensity profiles to meet the goals of a treatment plan is called:
A. fluence mapping
B. 3D conformal radiotherapy
C. 4D treatment planning
D. intensity modulation
D. intensity modulation
When a coefficient of equivalent thickness (CET) is used for an inhomogeneity, the CET factor equates the inhomogeneity to an equivalent thickness of:
A. air.
B. water.
C. lung.
D. compact bone.
B. water
According to AAPM Task Group 142, regarding the QA of medical accelerators, what is the monthly tolerance for scaling when considering SRS/SBRT Planar kV imaging?
A. ≤ 1mm
B. ≤ 2mm
C. baseline
D. functional
B. ≤ 2mm
Two adjacent posterior fields are used to treat the spine. The first field is 25.0 cm long at 100 cm SSD. The second field is 15.0 cm long at 100 cm SSD. The gap required on the skin in order to match the two fields at 6.0 cm depth is:
A. 1.2 cm.
B. 1.6 cm.
C. 2.0 cm.
D. 2.4 cm.
A. 1.2 cm.
Rationale: 1⁄2(Feld Length)(depth)/SSD for each field. (.5)(25)(6)/100 = .75 cm. .5)(15)(6)/100 = .45 cm 0.75 + 0.45 = 1.2 cm
What is the decay constant of Co-60 in years?
A. 0.01 yr-1
B. 0.13 yr-1
C. 0.69 yr-1
D. 7.59 yr-1
B. 0.13 yr-1
Rationale:
Decay Constant = ln2/HL = .693/5.2 years = 0.133 yr-1
Very accurate specification of dose at depth in a wedged field necessitates that the medical dosimetrist accounts for which of the following factors?
A. same central axis percent depth dose that occurs in a wedged field
B. wedge transmission factor is measured in air or in tissue
C. no variations of the wedge transmission factor with field size
D. reduction in collimator scatter that is reaching the patient
B. wedge transmission factor is measured in air or in tissue
The similarities for depth dose characteristics of megavoltage electron and photon beams is/are:
A. they have a finite range of penetration.
B. the percent surface dose is high.
C. the percent surface dose increases as the energy increases.
D. the percent depth dose increases as the beam energy increases.
D. the percent depth dose increases as the beam energy increases.
What factors affect depth dose?
A. energy, depth, field size, SSD, blocked area
B. energy, depth SSD, dose build up, collimation
C. depth, field size, beam quality, source size
D. depth, energy, absorbed energy, scatter
A. energy, depth, field size, SSD, blocked area
The depth of maximum dose (Dmax) increases as photon energy increases because the:
(1) electron density in the medium is greater below the surface.
(2) kerma increases.
(3) higher energy photon beams are not attenuated initially.
(4) range of photon-scattered electrons increases.
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(C) (2) and (4) only are correct.
Which of the following can be classified as indirectly ionizing radiation?
(A) photons
(B) electrons
(C) alpha particles
(D) protons
(E) beta particles
(A) photons
The binding energy of the nucleus:
(A) is inversely proportional to the atomic number.
(B) increases exponentially with atomic number.
(C) depends only on the number of protons.
(D) represents a mass defect in the nucleus.
(E) decreases with relative electron density.
D) represents a mass defect in the nucleus.
Explanation:
The binding energy of the nucleus is the energy required to break the nucleus into its individual protons and neutrons. This energy corresponds to the mass defect (the difference between the mass of the nucleus and the sum of the masses of its constituent nucleons) due to Einstein’s equation
E=mc^2
.
The linear attenuation coefficient for a given photon beam is 0.063 mm-1 lead, the corresponding half value layer (HVL) is:
A. 0.04 mm lead.
B.0.09 mm lead.
C. 9.50 mm lead.
D.11.00 mm lead.
E.13.00 mm lead.
D.11.00 mm lead.
HVL=ln(2)/ μ
HVL= 0.693 / 0.063 ≈11.00mmlead
The accelerator component that injects electrons into the linear accelerator is:
A. klystron
B. electron gun
C. high voltage power supply bending magnet
D. thyratron
B. electron gun
Key points about the other options:
Klystron:
is a device used to generate high-frequency microwaves that power the acceleration process within the linear accelerator, not the electron injection source.
High voltage power supply bending magnet
is used to steer the electron beam, not to inject it.
Thyratron:
This is a type of gas-filled tube used as a high-power electrical switch, not directly involved in electron injection into a linear accelerator.
The accelerator component that injects electrons into the linear accelerator is:
A. klystron
B. electron gun
C. high voltage power supply bending magnet
D. thyratron
B. electron gun
Key points about the other options:
Klystron:
is a device used to generate high-frequency microwaves that power the acceleration process within the linear accelerator, not the electron injection source.
High voltage power supply bending magnet
is used to steer the electron beam, not to inject it.
Thyratron:
This is a type of gas-filled tube used as a high-power electrical switch, not directly involved in electron injection into a linear accelerator.
Bremsstrahlung radiation may be produced by:
(1) electrons striking high atomic number targets.
(2) neutrons striking low atomic number targets.
(3) electrons striking low atomic number targets.
(4) alpha particles striking low atomic number targets.
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(B) (1) and (3) only are correct
The accelerator component that directs electron beam to the output window from the accelerator guide is:
(A) klystron
(B) electron gun
(C) high voltage power supply
(D) bending magnet
(E) thyratron
(D) bending magnet
Multileaf collimators (MLC) are advantageous over conventional field shaping devices because:
(1) there is no danger of injury to the patient or therapist from a falling block.
(2) they eliminate toxicity concerns resulting from fabrication and handling of lead and cadmium alloy blocks.
(3) they save block fabrication costs, storage space, and the effort of lifting and mounting heavy blocks.
(4) immediate modification of the field aperture can be made if the portal image reveals inaccuracy:
A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(E) All are correct.
Which of the following clinical machines produce photon beams?
(1) betatron
(2) linear accelerator
(3) microtron
(4) cyclotron
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(A) (1), (2), and (3) only are correct
Betatron: Produces high-energy photon beams.
Linear accelerator (linac): Commonly used in radiation therapy, generates photon beams.
Microtron: Also capable of producing photon beams.
Cyclotron typically produces charged particle beams rather than photon beams, which excludes it from the correct options.
Which component is NOT used in a scanning magnet electron beam system?
(A) scattering foil
(B) bending magnet
(C) ionization chamber
(D) collimator
(E) vacuum pump
(A) scattering foil
The clinical machine capable of the highest photon dose rate is the:
(A) betatron.
(B) cobalt-60 unit.
(C) linear accelerator.
(D) cyclotron.
(E) Van de Graaf generator.
(C) linear accelerator
Pulsed microwaves are produced in megavoltage linear accelerators by the:
(1) magnetron.
(2) thyratron.
(3) klystron.
(4) waveguide.
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(B) (1) and (3) only are correct.
Stereotactic radiosurgery can be performed using:
(1) photons.
(2) protons.
(3) Cobalt-60.
(4) electrons.
(A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(A) (1), (2), and (3) only are correct.
The value for the Ngas calibration factor for an ionization chamber will depend on the:
(1) composition of the chamber wall.
(2) temperature and pressure of the air in the chamber.
(3) volume of the chamber.
(4) source to chamber distance.
A) (1), (2), and (3) only are correct.
(B) (1) and (3) only are correct.
(C) (2) and (4) only are correct.
(D) (4) only is correct.
(E) All are correct.
(B) (1) and (3) only are correct.
Double check I think it’s A
Thin window parallel-plate chambers are useful for measuring radiation dose in certain circumstances where cylindrical chambers cannot be used. One of the specific circumstances is for measuring radiation dose at or near:
(A) the surface.
(B) 5 cm depth.
(C) 10 cm depth.
(D) equilibrium depth.
(E) a specific isodose level.
(A) the surface.
What is the approximate density of healthy lung tissue?
A. 0.30 g/cc
B. 0.95 g/cc
C. 1.00 g/cc
D. 1.03 g/cc
A. 0.3 g/cc
What is the approximate density of healthy lung tissue?
A. 0.30 g/cc
B. 0.95 g/cc
C. 1.00 g/cc
D. 1.03 g/cc
A. 0.3 g/cc
The accelerator component that injects electrons into the linear accelerator is:
A. a klystron.
B. an electron gun.
C.a bending magnet.
D. a thyratron.
B. an electron gun
Radiation damage to the fetus resulting in severe birth defects would most often occur when radiation was delivered at which time post-fertilization?
A. 0 - 2 weeks
B. 3 - 12 weeks
C. 13 - 24 weeks
D. 23 - 32 weeks
B. 3 - 12 weeks
The decay constant for a radioactive source that has a half-life of 60 days is:
A. 0.012.
B. 0.170.
C. 0.662.
D. 1.250.
A. 0.012
Two missed treatment days due to LINAC malfunction:
A. may be compensated by adding the same or even more fractions to the treatment course with weekend treatment if possible.
B. may allow some tumors with high growth fractions and long cell cycle times to recover through repopulation.
C. are of major clinical relevance in most cases.
D. may be made up by increasing the fraction size for the remainder of the treatment course.
A. may be compensated by adding the same or even more fractions to the treatment course with weekend treatment if possible.
For a 4-field box technique, which of the following will deliver the lowest dose to the femoral heads?
A. 100 source-to-surface distance (SSD), equal max dose to all fields
B. 100 source-to-surface distance (SSD), equal target dose to all fields
C. 100 source-to-axis distance (SAD), equal air dose to all fields
D. 100 source-to-axis distance (SAD), equal target dose to all fields
A. 100 source-to-surface distance (SSD), equal max dose to all fields
According to the American Association of Physicists in Medicine (AAPM) Task Group Report
#142, the constancy of dose per monitor unit for photon beams of a linear accelerator should be checked:
A. daily.
B. once a week.
C. once a month.
D. every three months.
A. daily
According to the American Association of Physicists in Medicine (AAPM) Task Group Report
#142, the constancy of dose per monitor unit for photon beams of a linear accelerator should be checked:
A. daily.
B. once a week.
C. once a month.
D. every three months.
A. daily
The surface dose rate of a Strontium-90 (St-90) eye applicator was 4.5 cGy/second on May 15.
If a patient is to be treated 2 years later on May 15, what is the treatment time if 1000 cGy is prescribed? (The half-life of Sr-90 is 28 years.)
A. 202 seconds
B. 214 seconds
C. 222 seconds
D. 233 seconds
D. 233 seconds
A=Aoe ^ -At
A=4.5(0.5)^ (2/28)=4.28
1000/4.28=233
The quality factor (QF) used for determining the dose equivalence for high-energy X rays compared to high-energy gamma rays is:
A. 0.869.
B. 0.956.
C. 1.000.
D. 1.035.
C. 1.000
A patient is treated by using parallel opposed equally weighted fields at 80 cm source-to-surface distance (SSD) on a 4 MV linear accelerator to a total midplane dose of 60 Gy. The patient diameter is 20 cm. The field size is 15 × 15 cm2. The total dose at a depth of 1.2 cm is:
PERCENT DEPTH DOSE for 4 MV PHOTONS, 80 SSD
Depth (cm). 15x15 cm^2
1.2. 100.0
5.0. 83.7
10.0. 63.6
15.0. 46.9
20.0. 34.1
2.5. 25.0
A. 62.6 Gy.
B. 64.7 Gy.
C. 66.5 Gy.
D. 68.1 Gy.
B. 64.7 Gy
AP= 30 x (100/63.6) =47.2Gy
PA= 30x(100/63.6)=17.5Gy
AP+PA= 47.2+17.5=64.7 Gy
After 6.5 years, the activity of a 25 mCi Cesium-137 source will be:
A. 19.5 mCi.
B. 20.5 mCi.
C. 21.5 mCi.
D. 22.6 mCi.
C. 21.5 mCi
A= 25e^ (- 0.693/ 30yr) x - (6.5yr)
The development of which of the following conditions is an example of a stochastic effect of radiation?
A. organ atrophy
B. second primary
C. pulmonary fibrosis
D. decreased sperm count
B. second primary
Explanation:
Stochastic effects:
These are random occurrences where the probability of the effect increases with radiation dose, but the severity of the effect is not dependent on the dose. Cancer development is the primary example of a stochastic effect.
Second primary cancer:
This refers to a new, unrelated cancer developing in a person who has already had cancer, which aligns with the stochastic nature of radiation-induced cancer.
Other options:
Organ atrophy: This is considered a deterministic effect, meaning it has a threshold dose and the severity increases with the dose.
Pulmonary fibrosis: Similar to organ atrophy, this is generally considered a deterministic effect due to the dependence of severity on the radiation dose.
Decreased sperm count: While radiation can affect sperm count, this is also typically categorized as a deterministic effect due to the dose-dependent severity.
The development of which of the following conditions is an example of a stochastic effect of radiation?
A. organ atrophy
B. second primary
C. pulmonary fibrosis
D. decreased sperm count
B. second primary
Explanation:
Stochastic effects:
These are random occurrences where the probability of the effect increases with radiation dose, but the severity of the effect is not dependent on the dose. Cancer development is the primary example of a stochastic effect.
Second primary cancer:
This refers to a new, unrelated cancer developing in a person who has already had cancer, which aligns with the stochastic nature of radiation-induced cancer.
Other options:
Organ atrophy: This is considered a deterministic effect, meaning it has a threshold dose and the severity increases with the dose.
Pulmonary fibrosis: Similar to organ atrophy, this is generally considered a deterministic effect due to the dependence of severity on the radiation dose.
Decreased sperm count: While radiation can affect sperm count, this is also typically categorized as a deterministic effect due to the dose-dependent severity.
When an enface electron beam is used for chest wall irradiation, which of the following describes the dose at the interface between the chest wall and lung?
A. decreased due to reduced scatter from the lung
B. decreased due to irregular surface contour effects
C. increased due to an increase in the electron fluence
D. increased due to a larger angle of electron scatter
A. decreased due to reduced scatter from the lung
- An averaged ionization chamber reading for a 10 cm x 10 cm electron applicator is 98.5 and an averaged ionization chamber reading for an electron cut-out in a 6 cm x 10 cm applicator is 92.4. What is the monitor unit setting if 200 cGy is prescribed to 90% and the 6 cm × 10 cm cut-out is utilized? (The output factor for 10 cm x 10 cm is 1 cGy/MU.)
A. 208 MU
B. 217 MU
C. 222 MU
D. 237 MU
D. 237 MU
200/(92.4/983) x (0.90)
To make inhomogeneity corrections in treatment plans based on CT derived anatomic information, the TPS:
A. converts CT numbers to Hounsfield units.
B. determines the absorption equivalents.
C. converts to equivalent path lengths.
D. determines electron densities.
D. determines electron densities.
Explanation:
CT numbers to Hounsfield units:
This is a basic conversion step, but the key function is to translate those Hounsfield units into electron densities to account for tissue variations.
Electron densities:
This is the crucial factor for calculating accurate dose distributions in tissues with different densities, which is the primary purpose of inhomogeneity correction in treatment planning.
When opposing lateral fields to the pharynx are abutted at midline to an anterior field to the supraclavicular fossae, overdose in the cord may be avoided by:
A. a 0.5 cm wide by 0.5 cm long midline block placed in the superior portion of the anterior field.
B. a small block over the cord in the inferior posterior corner of both lateral fields.
C. angling the laterals fields off the cord.
D. angling the supraclavicular field off the cord.
B. a small block over the cord in the inferior posterior corner of both lateral fields.
When opposing lateral fields to the pharynx are abutted at midline to an anterior field to the supraclavicular fossae, overdose in the cord may be avoided by:
A. a 0.5 cm wide by 0.5 cm long midline block placed in the superior portion of the anterior field.
B. a small block over the cord in the inferior posterior corner of both lateral fields.
C. angling the laterals fields off the cord.
D. angling the supraclavicular field off the cord.
B. a small block over the cord in the inferior posterior corner of both lateral fields.
According to the NCRP guidelines #116, the annual equivalent dose limit for the hands of an occupational worker in 1 year is:
A. 15 mSv ( 1.5 rem).
B. 50 mSv ( 5.0 rem).
C. 150 mSv (15.0 rem).
D. 500 mSv (50.0 rem).
D. 500 mSv (50.0 rem).
In photoelectric interactions:
A. chance of occurrence is independent of the atomic number
B. the probability depends on the interaction between a photon and a free radical
C. the entire energy of the incident photon is absorbed by the resulting electron
D. the effect increases as the photon energy increases relative to the binding energy of the electron
C. the entire energy of the incident photon is absorbed by the resulting electron
Explanation:
A is incorrect:
The probability of a photoelectric interaction is highly dependent on the atomic number of the material, which is directly related to the number of electrons available for interaction.
B is incorrect:
A photoelectric interaction occurs when a photon interacts with a bound electron within an atom, not a free radical.
C is correct:
In a photoelectric interaction, the entire energy of the incident photon is transferred to the ejected electron, provided the photon energy is greater than the binding energy of the electron.
D is the key point:
The likelihood of a photoelectric interaction increases when the photon energy is significantly higher than the binding energy of the electron in the atom
Film badges used for personnel monitoring contain filters that are used to:
A. reduce the dose from low-energy radiations.
B. provide information concerning beam quality.
C. store the absorbed energy for subsequent measurement.
D. filter out naturally occurring radiation.
B. provide information concerning beam quality.
The most important prognostic factor in breast cancer is the:
A. size of the tumor.
B. age of the patient.
C. status of the axillary nodes.
D. quadrant of origin within the breast.
C. status of the axillary nodes
A dose of 30 Gy in 10 fractions to a depth of 7 cm from a 6 MV single posterior field using an isocentric technique at 100 cm source-to-axis distance (SAD). The patient was incorrectly treated five times at 100 cm source-to-surface distance (SSD). The approximate dose at 7 cm after five fractions is:
A. 11.6 Gy.
B. 13.1 Gy.
C. 13.8 Gy.
D. 15.0 Gy.
B. 13.1 Gy
The inverse square law formula
is used to calculate the change in dose due to the difference in distance from the source. The formula is:
D(ssd)/D(sad)=( SAD/SSD+d)^2
(100/100+7)^2= 0.8734
15Gy x 0.8734=13.1 Gy
Electron beam output factors are corrected for by using which of the following?
A. energy coefficient
B. equivalent thickness
C. virtual source distance
D. electron range
C. virtual source distance
Electron arc therapy is most useful for treating tumors of the:
A. pituitary.
B. chest wall.
C. pancreas.
D. brain.
B. chest wall
Percentage Depth Dose is dependent on which of the following?
A. Field size
B. Tissue density
C. Treatment time
D. Dose rate
A. Field size
Percentage Depth Dose is dependent on which of the following?
A. Field size
B. Tissue density
C. Treatment time
D. Dose rate
A. Field size
Where is dose routinely normalized when using a fixed Source to Surface Distance (SSD) technique?
A. At isocenter
B. A tumor depth
C. At Dmax
D. On the surface
C. At Dmax
In a fixed Source to Surface Distance (SSD) technique, the dose is routinely normalized at the depth of maximum dose (Dmax). Dmax is the depth at which the dose deposited by the photon beam is the highest, and this is commonly used as the reference point for dose normalization in SSD-based treatments.
How can you minimize the gap between two adjacent treatment fields?
A.Use posterior fields alone
B. Use anterior fields alone
C. Use a half beam block
D. Treat both field at the same time
C. Use a half beam block
Where will the maximum dose occur when parallel-opposed 6-MV photon beams are used in a 20 cm thick patient?
A. The tumor
B. Midplane
C. The dose will be uniform through the patient
D. Entrance and exit of each field
D. Entrance and exit of each field
When using parallel-opposed 6-MV photon beams in a 20 cm thick patient, the maximum dose will typically occur at the entrance and exit of each field. This happens because of the buildup effect: photon beams deposit more energy as they travel deeper into tissue until reaching a point called Dmax, after which the dose falls off. For parallel-opposed fields, the entrance and exit of the beams experience higher doses compared to the midplane
Why is bolus material used in photon therapy?
A. Reduce the dose to the skin
B. Reduce the depth of the maximum dose (max)
C. Increase the depth of maximum dose (D max)
D. Increase surface irregularities on the surface of the patient
B. Reduce the depth of the maximum dose (max)
Which type of cancer is most commonly encountered in the head and neck region?
A. Lymphoma
B. Glioma
C. Squamous Cell Carcinoma
D. Adenocarcinoma
C. Squamous Cell Carcinoma
Squamous cell carcinoma makes up about 90 percent of all head and neck cancers
Giving too much radiation to which of the following can lead to xerostomia?
A. Tonsils
B. Base of tongue
C. Salivary glands
D. Floor of mouth
C. Salivary glands
Which of the following is a disadvantage of an anteriorly directed vertex field if a patient’s head is in a flexed position?
A. It exits through the chest
B. It exits through the pharynx and spinal cord
C. It exits through the eyes
D. It exits through the posterior scalp
B. exit through the pharynx and spinal cord
Explanation: When the head is flexed, an anteriorly directed beam can miss the intended target and exit through the neck region, potentially exposing sensitive structures like the pharynx and spinal cord to unnecessary radiation.
Key points about the other options:
Option A (chest):
An anteriorly directed beam would not exit through the chest unless the patient is positioned very abnormally.
Option C (eyes):
While the eyes could be at risk with an anteriorly directed beam, the flexed head position would likely not exacerbate this issue as much as the pharynx/spinal cord exposure.
Option D (posterior scalp):
This is not a concern for an anteriorly directed beam, as the radiation would be exiting at the front of the head.
Why should the medial field edge be placed lateral to the vertebral column in the treatment of children with Wilm’s tumor?
A. To avoid unequal bone growth of the vertebral column
B. To avoid hot spots in the spinal cord
C. To avoid excess radiation to the contralateral kidney
D. To spare bowel toxicity
A. To avoid unequal bone growth of the vertebral column
The inguinal lymph nodes are located at a depth of:
A. 4 cm from the anterior skin surface and are not dependent on patient size.
B. 5 - 7 cm from the anterior skin surface and are not dependent on patient size.
C. 2 - 18 cm from the anterior skin surface and are dependent on patient size.
D. 1/3 the distance of the patient’s anterior to posterior diameter.
C. 2 - 18 cm from the anterior skin surface and are dependent on patient size.
What is the most serious late consequence of high dose total body irradiation?
A. Hair loss
B. Vision loss
C. Chronic liver disease
D. Radiation Pneumonitis
D. Radiation Pneumonitis
While hair loss and vision loss can occur, radiation pneumonitis is a severe complication that can progress to pulmonary fibrosis, especially when treating large areas like in TBI. Chronic liver disease can also be a risk, but pneumonitis is a more immediate and severe threat in the context of high-dose TBI
What is the main goal of palliative radiotherapy for bone metastases?
A. Prevent tumor spread
B. Pain control
C. Eradicate the tumor in the bone
D. Reduce nausea associated with pain medication
B. Pain control
The mass attenuation coefficient (μ m) is related to the linear attenuation coefficient (μ) by which of the following relationships?
A. μ m = Z^-μx
B. μ m = μ ° p
C. μ m = μ / p
D. μ m = e^-μx
C. μ m = μ / ρ
Where:
*μm- is the mass attenuation coefficient,
*μ- is the linear attenuation coefficient,
*ρ -is the density of the material.
This relationship indicates that the mass attenuation coefficient is the linear attenuation coefficient divided by the material’s density.
The dose to a point located on the central axis of a broad field of a 6 MVX beam will change when the distance (d) of this point from the source of radiation is changed.
A.Inversely as function of d2
B.Inversely as function of d
C.Directly as a function of d
D. Directly as a function of d2
A.Inversely as function of d2
This is based on the Inverse Square Law, which states that radiation intensity (and therefore dose) decreases with the square of the distance from the source. So as the distance (d) increases, the dose decreases inversely with the square of the distance.
The collimator scatter factor for any MV x-rays beam:
A. Is measured in free space with an ionization chamber.
B. Decreases with the increase of field size.
C. Does not depend on the field size.
D. Does not change with the energy of the beam.
A. Is measured in free space with an ionization chamber.
Which of the following statements is true about the surface dose of MV x-rays beams relative to the dose at the Dmax?
A. It usually decreases with the addition of a blocking tray.
B. It increases as the SSD increases, for the same field size on the skin.
C. It decreases as the photon energy increases.
D. It is not affected by the change in field size.
C. It decreases as the photon energy increases.
Radiographs that are generated from CT data in a plane perpendicular to the central axis of a simulated beam of radiation and used as reference images for verification of a computer-designed treatment are known as:
A. portal images.
B. digitally reconstructed radiographs (DRRs).
C. virtual simulation.
D. image guided radiotherapy (IGRT).
B. digitally reconstructed radiographs (DRRs).
The tumor type that is most responsive to radiation treatment is:
A. melanoma.
B. adenocarcinoma.
C. sarcoma.
D. seminoma.
D. seminoma
Thin window parallel-plate chambers are useful for measuring radiation dose in certain circumstances where cylindrical chambers cannot be used. One of the specific circumstances is for measuring radiation dose at or near:
A. the surface.
B. a 5 cm depth.
C. an equilibrium depth.
D. a specific isodose level.
A. the surface
The energy loss rate of a 10 Me electron in water is approximately:
A. 0.51 MeV/cm.
B. 0.69 MeV/cm.
C. 1.25 MeV/cm.
D. 2.00 MeV/cm.
D. 2.00 MeV/cm.
Autoradiography of an encapsulated brachytherapy source is:
A. an automatic afterloading technique used to reduce exposure to the nursing staff.
B. a procedure using three radiographs to automatically identify radioactive seeds.
C. a manufacturing process used to ensure all sources have the same activity.
D. a test for gross nonuniformity of the radionuclide within a source capsule.
D. a test for gross nonuniformity of the radionuclide within a source capsule.
As the energy of the parallel-opposed x-rays beams of same energy increases, it will lead
A. decreased dose at midplane.
B. decreased skin dose.
C. increased dose in build-up region.
D. increased dose at Dmax.
B. decreased skin dose.
In the small volume treatment of bladder cancer with radiation therapy, the patient should be treated with:
A. a full bladder in order to spare as much small bowel as possible.
B. a full bladder in order to spread the dose evenly to the tumor.
C. an empty bladder in order to encompass tumor with reproducibility.
D. an empty bladder in order to minimize bleeding complications.
C. an empty bladder in order to encompass tumor with reproducibility.
Although they receive the same dose, some tissues exhibit acute radiation damage earlier than others because they have a:
A. smaller number of metabolizing cells.
B. reduced blood flow.
C. lower number of hypoxic cells.
D. higher mitotic index.
D. higher mitotic index.
A 20 cm diameter patient is treated to midplane by using a 100 cm source-to-axis distance (SAD) technique. If the same patient is then treated by using a 100 cm source-to-surface distance (SSD) technique, the monitor units would increase by approximately
A. 10%.
B. 15%.
C. 21%.
D. 25%.
C. 21%
Explanation
(110/100)^2=1.21
21%
According to the NCRP Report #116, the annual effective dose limit for continuous exposure to the whole body for the general public is:
A. 0.5 mSv (0.05 rem).
B. 1.0 mSv (0.10 rem).
C. 15.0 mSv (1.50 rem).
D. 75.0 mSv (7.50 rem).
B. 1.0 mSv (0.10 rem).
According to the NCRP Report #116, the annual effective dose limit for continuous exposure to the whole body for the general public is:
A. 0.5 mSv (0.05 rem).
B. 1.0 mSv (0.10 rem).
C. 15.0 mSv (1.50 rem).
D. 75.0 mSv (7.50 rem).
B. 1.0 mSv (0.10 rem).
Unless otherwise permitted by the NRC, brachytherapy needles and tubes must be leak tested by the user at intervals NOT to exceed:
A. 1 month.
B. 3 months.
C. 6 months.
D. 9 months.
C. 6 months.
