Radiation Safety Flashcards
A Computed Tomography Dose Index (CTDI) for a CT abdomen on a 5 year old patient should not exceed:
A. 10 mGy
B. 85 mGy
C. 40 mGy
D. 20 mGy
D. 20 mGy
A Computed Tomography Dose Index (CTDI) value exceeding the normal range may have been caused by which three of the following?
A. Incorrect patient identification
B. Incorrect technical settings
C. Inadequate contrast volume
D. Equipment malfunction
E. Large patient
B. Incorrect technical settings
D. Equipment malfunction
E. Large patient
After completing a CT scan, what patient dose information must be recorded and stored?
A. Highest recorded Computed Tomography dose index (CTDI)
B. Cumulative Computed Tomography dose Index (CTDI) for all scan series
C. Computed Tomography dose index (CTDI) and dose-linear product (DLP) for each scan series
D. Total dose-linear product (DLP)
C. Computed Tomography dose index (CTDI) and dose-linear product (DLP) for each scan series
Air kerma is measured in units of:
Gray (Gy), Milligray (mGy)
An increased patient size has what of the following effects on x-ray attenuation?
A. Increased attenuation
B. Decreased attenuation
C. No change in attenuation
A. Increased attenuation
Automatic Tube Current Modulation (ATCM) modifies what technical variable during the CT exposure?
A. mA
B. kVp
C. pitch
D. beam width
A. mA
Based on the information provided in this dose report, what scan may have been performed?
A. CT head without contrast
B. CT head with and without contrast
C. CT abdomen with and without contrast
D. CT abdomen and pelvis without contrast.
C. CT abdomen with and without contrast
Concerning radiation-induced cancer, increasing the radiation dose to a patient results in:
A. Increased severity of cancer
B. Decreased severity of cancer
C. Increase probability of cancer
D. Decreased probability of cancer
C. Increase probability of cancer
Consider the following dose data from three different CT scans. Which procedure has the highest risk of acquiring radiation-induced cancer?
Procedure 1: Absorbed dose= 21 mGy, Effective dose= 11 mSv
Procedure 2: Absorbed dose= 80 mGy, Effective dose= 3 mSv
Procedure 3: Absorbed dose= 34 mGy, Effective dose= 10 mSv
Procedure 1: Absorbed dose= 21 mGy, Effective dose= 11 mSv
Consider this scenario: A medical physicist is scanning a CT phantom with several materials, each having a different atomic number. Which material will cause the least amount of attenuation?
A. Atomic number= 6
B. Atomic number= 19
C. Atomic number= 53
D. Atomic number= 56
A. Atomic number= 6
Consider this scenario: During a CT scan of the chest, the technologist administers a radiation dose of approximately 3,000 milligray (mGy) Which two of the following effects may occur?
A. Cataracts
B. Epilation
C. Cancer
D. Decreased fertility
B. Epilation
C. Cancer
Deterministic effects of radiation exposure include which three of the following? Select three:
A. Skin erythema
B. Epilation
C. Cancer
D. Miscarriage
E. Heritable (genetic effects)
A. Skin erythema
B. Epilation
D. Miscarriage
Dose-linear Product (DLP) is equal to:
A. Computed Tomography Dose Index (CTDI) x scan field of view
B. Computed Tomography Dose Index (CTDI) x scan length
C. Computed Tomography Dose Index (CTDI) x beam width
D. Computed Tomography Dose Index (CTDI) x display field-of-view
B. Computed Tomography Dose Index (CTDI) x scan length
During a CT procedure, attenuation of the x-ray beam may be caused by which three of the following?
A. Coherent scattering
B. Bremssrahlung Radiation
C. Compton scattering
D. Photoelectric absorption
E. Characteristic radiation
A. Coherent scattering
C. Compton scattering
D. Photoelectric absorption
During CT scanning, what part of the patient receives the highest dose of radiation?
A. Center of the patient
B. Surface if the patient
C. Anterior side of the patient
D. Posterior side of the patient
B. Surface if the patient
Effective dose is measured with units of:
Sievert (mSv) or Millisievert (mSv)
Equivalent dose is described with units of:
Sievert or millisievert (mSv)
For deterministic effects of radiation, increasing dose results in:
A. Increased severity of the effect
B. Decreased severity of the effect
C. Increased probability of the effect
D. Decreases probability of the effect
A. Increased severity of the effect
How does decreasing kVp affect patient dose?
A. Increases patient dose
B. Decreases patient dose
C. No change in patient dose
B. Decreases patient dose
How does increasing kVp affect patient dose?
A. Increases patient dose
B. Decreased patient dose
C. No-change in patient dose
A. Increases patient dose
How does increasing mA affect patient dose?
A. Increases patient dose
B. Decreases patient dose
C. No change in patient dose
A. Increases patient dose
How does increasing pitch affect patient dose?
A. Increases patient dose
B. Decreases patient dose
C. No change in patient dose.
B. Decreases patient dose
How will changing the total beam collimation from 8 mm to 16 mm affect patient dose?
A. Increased patient dose
B. Decreased patient dose
C. No change in patient dose
B. Decreased patient dose
If a technologist receives a “dose alert” during a CT scan, he or she should:
A. Notify the patient
B. Notify the ordering physician
C. Review the exposure parameters
D. Review the examination identification
C. Review the exposure parameters
If a technologist receives a “dose alert” during a CT scan, he or she should:
A. Consider reducing the patient dose
B. Consider cancelling the examination
C. Complete a pregnancy test on the patient
D. Complete a creatinine test on the patient
A. Consider reducing the patient dose
If a technologist receives a “dose notification” during a CT scan, he or she should:
A. Consider reducing the patient dose
B. Consider cancelling the examination
C. Complete a pregnancy test on the patient
D. Complete a creatinine test on a patient
A. Consider reducing the patient dose
If the pitch for a CT study is changed from 1.1 to 1.0, which of the following three changes will occur, assuming all other variables remain unchanged?
A. Increased computed tomography dose (CTDI)
B. Increased dose-linear product (DLP)
C. Decreased patient dose
D. Increased patient dose
E. Decreased image quality
A. Increased computed tomography dose (CTDI)
B. Increased dose-linear product (DLP)
D. Increased patient dose
Increasing the kilovoltage peak (kVp) for a CT procedure results in:
A. Increased attenuation
B. Decreased attenuation
C. No change in attenuation
B. Decreased attenuation
Region of interest (ROI) measurements throughout a single CT image produced the following CT number readings. Which area demonstrates the highest level of attenuation?
ROI 1= -67 HU
ROI 2= -323 HU
ROI 3= +4 HU
ROI 4= +37 HU
ROI 4= +37 HU
Scanning an area of increased tissue density will result in _______ x-ray attenuation.
Increased
The Computed Tomography Dose Index (CTDI) for an adult abdominal scan should not exceed:
A. 25 mGy
B. 85 mGy
C. 40 mGy
D. 75 mGy
A. 25 mGy
The Computed Tomography Dose Index (CTDI) is calculated using:
A. Dose data collected from the patient after the scan.
B. Dose data collected from the cylinder phantoms
C. Dose data collected from the patient during the scan
D. Dose data stored by the American College of Radiology (ACR)
B. Dose data collected from the cylinder phantoms
The computed tomography dose index (CTDI) represents the:
A. Average recorded radiation dose to the phantom
B. Highest recorded radiation dose to the phantom
C. Lowest recorded radiation dose to the phantom
D. Average radiation dose at the center of the phantom
A. Average recorded radiation dose to the phantom
The diameter of the computed tomography dose index (CTDI) body phantom is:
A. 25 cm (10 in)
B. 16 cm (6 in)
C. 32 cm (12 in)
D. 50 cm (20in)
C. 32 cm (12 in)
The energy of ions created in air from x-rays.
Air Kerma
The main purpose of traditional lead shielding is to reduce:
A. Superficial dose in the exposure field
B. Superficial dose outside of the exposure field
C. Scatter radiation absorption in the exposure field
D. Scatter radiation absorption outside of the exposure field
D. Scatter radiation absorption outside of the exposure field
The number of ionization events in air is described as:
Exposure
The patient below is being scanned using the computed tomography angiography (CTA) pulmonary embolism protocol. This shielding technique is unacceptable because the:
A. Patient’s arms are outside of the shield
B. Shield is in the exposure field
C. Patient is not shielded in 360 degrees
D. Patient should not be shielded.
B. Shield is in the exposure field
The patient in the following image is being scanned using the CT head protocol. This shielding technique is unacceptable because the:
A. patient’s arms are on top of the shield
B. Shield is in the exposure field
C. Patient is not shielded in 360 degrees
D. Shield is designed for occupational use only
C. Patient is not shielded in 360 degrees
The patient in the following image is being scanned using the CT renal stone protocol. This shielding technique is unacceptable because the:
A. Patient’s arms are under the shield
B. Shield is the exposure field
C. Patient is shielded in 360 degrees
D. Shield is designed for occupational use only
B. Shield is the exposure field
The purpose of a “dose notification” is to:
A. Make the technologist aware that a high computed tomography dose index (CTDI) has been used.
B. Make the technologist aware that a high computed tomography dose index (CTDI) will be used.
C. Make the technologist aware that the scan length is too long
D. Make technologist aware that a low computed tomography dose index (CTDI) will be used.
B. Make the technologist aware that a high computed tomography dose index (CTDI) will be used.
When performing a CT of the neck, where should bismuth shielding be placed?
A. Over the anterior neck
B. Over the posterior neck
C. Over the gonads
D. Around the entire pelvis.
A. Over the anterior neck
When performing a CT of the neck, where should lead shielding be placed?
A. Over the anterior neck
B. Over the posterior neck
C. Over the anterior pelvis
D. Around the entire pelvis
D. Around the entire pelvis
When performing a CT of the patient’s chest, abdomen, and pelvis, where should lead shielding be placed?
A. Around the chest, abdomen, and pelvis
B. Around the pelvis only
C. Around the gonads only
D. Lead shielding should not be used.
D. Lead shielding should not be used.
When using automatic dose modulation (variable milliamperage [mA]), the scanner sets the mA throughout the scan based on:
A. Patient attenuation readings acquired during the scout images
B. Patient attenuation readings acquired during the helical scan
C. Patient height/weight/body mass index (BMI) entered by the technologist
D. Patient weight as measured by the scanner table
A. Patient attenuation readings acquired during the scout images
When using automatic dose modulation (variable milliamperage [mA]), changing tube output between projections is called:
A. Z-axis modulation
B. X-axis modulation
C. Y-axis modulation
D. X-Y axis modulation
D. X-Y axis modulation
When will a technologist receive a dose notification?
A. When the computed tomography dose index (CTDI) for the scan is set to exceed predetermined dose notification value
B. When the cumulative computed tomography dose index (CTDI) for the scan is set to exceed 1,000 mGy
C. When a female patient dose not have a recent pregnancy test on file
D. When the scanner is operated a maximum tube current.
A. When the computed tomography dose index (CTDI) for the scan is set to exceed predetermined dose notification value
Which of the following dose quantities is most useful for projecting the risk of radiation-induced cancer?
A. Exposure
B. Air kerma
C. Absorbed dose
D. Equivalent dose
E. Effective dose
E. Effective dose
Which of the following effects may occur n patient’s receiving a very small dose of radiation?
A. Cataracts
B. Epilation
C. Skin burns
D. Cancer
D. Cancer
Which of the following is a likely reason for a CT examination exceeding the dose notification value?
A. Incorrect protocol selection
B. Positive pregnancy test
C. Increased milliamperage (mA)
D. Increased scan length
C. Increased milliamperage (mA)
Which of the following materials results in the highest number of photon interactions?
A. Air
B. Fat
C. Muscle
D. Metal
D. Metal
Which of the following materials will result in the highest x-ray transmission reading?
A. Air
B. Cortical bone
C. Muscle
D. Iodine
A. Air
Which of the following values represents a normal Computed Tomography Dose Index (CTDI) of a pediatric CT head?
A. 74 mGy
B. 85 mGy
C. 40 mGy
D. 20 mGy
C. 40 mGy
Which of these materials will result in the highest x-ray attenuation reading?
A. Bone
B. Fat
C. Muscle
D. Metal
D. Metal
Which of these radiation interactions DO NOT result in ionization of an atom?
A. Coherent scattering
B. Photoelectric absorption
C. Compton scattering
A. Coherent scattering
Which of these radiation measurements describe the joules of energy deposited in the patient from ionizing radiation?
A. Exposure
B. Air Kerma
C. Absorbed dose
D. Equivalent dose
E. Effective dose
C. Absorbed dose
Which two of the following radiation effects have a threshold dose below which they do not occur? (Select two)
A. Cataracts
B. Bronchogenic carcinoma
C. Leukemia
D. Skin Erythema
A. Cataracts
D. Skin Erythema
While positioning a patient for a CT of the chest, the technologist does not center the patient in the center of the gantry. The scanner is using a variable milliamperage (mA). This error is most likely to result in:
A. Increased patient dose
B. Decreased contrast resolution
C. Beam-hardening artifact
D. Increased image magnification
A. Increased patient dose
The number of ionizations created in air. It’s measured with units of colombs per kilogram (C/kg).
Exposure
KERMA is an acronym that stands for:
Kinetic energy released per unit mass.
Helps to quantify radiation by measuring the energy of ionizations (liberated electrons).
Air kerma
Air kerma is measured in:
Gray (Gy) or milligray (mGy).
Increasing mA ______ exposure and air kerma.
Increases.
Increasing kVp ______ exposure and air kerma.
Increases
One gray is equal to _____ joule per kilogram (J/kg).
One
An extension of the absorbed dose. It’s represented in units of sievert (Sv) or millisievert (mSv).
Equivalent dose
Takes into account the specific radiosensitivities of different tissue types, and they’re not all the same.
Effective dose.
Which of these radiation measurements describes the joules of energy deposited in the patient from ionizing radiation?
A. Exposure
B. Air kerma
C. Absorbed dose
D. Equivalent dose
E. Effective dose
C. Absorbed dose.
A physicist is measuring the scatter radiation produced during a CT procedure. The measured scatter radiation will INCREASE in which of these situations?
A. Decreasing mA used during the procedure
B. Decreasing rotation time used during the procedure
C. Decreasing kVp used during the procedure
D. Decreasing the distance from the scanner
D. Decreasing the distance from the scanner
Absorbed dose is a radiation measurement represented with units of:
Milligray (mGy)
Which of these dose quantities is most useful for describing the risk of radiation-induced cancer?
A. Exposure
B. Air Kerma
C. Absorbed Dose
D. Equivalent Dose
E. Effective Dose
E. Effective Dose
Consider the following average dose data from three different procedures and answer the question that follows:
Procedure 1: Absorbed dose= 21 mGy, Effective Dose=11mSv
Procedure 2: Absorbed dose= 80 mGy, Effective Dose=3 mSv
Procedure 3: Absorbed dose= 34 mGy, Effective Dose=10 mSv
Which procedure has the highest risk of causing a radiation induced cancer?
Procedure 1
During a CT exposure, many x-rays will pass through the body without interacting in any way at all. We call this _____. The x-rays aren’t absorbed or scattered. They just pass through the patient and get measured by the detector array.
Transmission
Has no biological effect. The x-ray photon is temporarily absorbed by an electron ad then immediately emitted out of the electron with all of it’s original energy. It’s called “scattering because the x-ray is emitted in a different direction than its original path. These interactions do not result in ionization, so there’s no biological harm to the patient.
Coherent scattering.
The removal of a bound electron from an atom. Results in broken molecules and damaged cells.
Ionization
In ____________, the incoming x-ray photon is fully absorbed by an electron. This electron is ejected out of its orbit, which results in ionization (the creation of charged particles).
Photoelectric absorption.
During a CT exposure, a portion of the x-ray beam is _________ by the patient and the remainder is ______ through the patient.
attenuated; transmitted
_______ patient size increases attenuation.
Increases
________ tissue density increases attenuation.
Increasing
______ atomic number increases attenuation.
Increasing
_______ kVp decreases attenuation. Results in increased x-ray energy and decreased probability of attenuation.
Increasing
Occur only at specific doses of radiation and not before. The dose-response threshold s determined (or known) and the severity of the effect increases with increasing dose.
Deterministic effects
______ effects are the larger concern in CT and diagnostic imaging. Whether or not the effect occurs is based on chance, not a minimum dose. This means that (theoretically) any radiation dose increases the chance of this effect.
Stochastic
Consider this scenario: A medical physicist is scanning a CT phantom with several materials, each having a different atomic number. Which material will cause the MOST amount of attenuation?
A. Atomic number= 6
B. Atomic number= 19
C. Atomic number= 53
D. Atomic number= 56
D. Atomic number= 56
ROI measurements throughout a single CT image produced these CT number readings:
ROI 1 = -77 HU
ROI 2 = -211 HU
ROI 3 = +1 HU
ROI 4 = +41 HU
Which area demonstrates the HIGHEST level of attenuation?
ROI 4 = +41 HU
What radiation interaction yields an ionized electron without a scattered photon?
Photoelectric Effect
Which of the following are by-products of a coherent scattering event?
- Ionized electron
- Scattered Photon
- Characteristic photon
A. 1 only
B. 2 only
C. 1 and 2 only
D. 1 and 3 only
B. 2 only
Stochastic effects of radiation exposure include:
A. Cataracts
B. Epilation
C. Cancer
D. Genetic Diseases
C. Cancer
D. Genetic Diseases
Which of these effects may occur in patients receiving a very small dose of radiation? (choose multiple)
A. Cataracts
B. Epilation
C. Cancer
D. Genetic Diseases
C. Cancer
D. Genetic Diseases
During a CT scan of the neck, the technologist uses a technique resulting in a patient dose of approximately 30 mGy. What is the most likely effect of this procedure?
A. Cataracts
B. Epilation
C. Skin Erythema
D. Cancer
D. Cancer
For deterministic effects, increasing radiation dose results in:
A. Increased severity of the effect
B. Decreased severity of the effect
C. Increase probability of the effect
D. Decreases probability of the effect
A. Increased severity of the effect
The Computed Tomography Dose Index (CTDI) is calculated using:
A. Dose data collected from the patient after the scan
B. Dose data collected from cylinder phantoms
C. Dose data collected from the patient during the scan.
B. Dose data collected from cylinder phantoms
CTDI is measured in units of:
milligray (mGy)
The diameter of the CTDI body phantom is:
32 cm
The following CTDI values were collected on three different patients, each undergoing the same CT procedure.
Scan 1: CTDI = 13 mGy
Scan 2: CTDI = 15 mGy
Scan 3: CTDI = 23 mGy
Which of the following statements best explains the difference in CTDI measurements?
A. A different mA was used for each patient
B. A different scan length was used for each patient
C. A different shielding device was used for each patient
D. A different volume of IV contrast was used for each patient
A. A different mA was used for each patient
Dose-length Product (DLP) is equal to:
A. CTDI x scan field-of-view
B. CTDI x scan length
C. CTDI x beam width
D. CTDI x display field-of-view
B. CTDI x scan length
Which of the following values represents a normal CTDI of a pediatric CT head?
A. 75 mGy
B. 85 mGy
C. 40 mGy
D. 20 mGy
C. 40 mGy
A CT exam was performed with a fixed technique of 250 mA and the resulting CTDI was 30 mGy. If the same examination is repeated with 500 mA, what is the new CTDI?
A. 120 mGy
B. 15 mGy
C. 60 mGy
D. 7.5 mGy
C. 60 mGy
If the mA for a CT scan is decreased by a factor of 1.5, how will the patient dose change?
A. Decrease by a factor of 1.5
B. Increase by a factor of 1.5
C. Increase by a factor of 1.52
D. Decrease by a factor of 1.53
A. Decrease by a factor of 1.5
A CT examination of the head used a fixed technique of 200 mA, 1.0 second rotation time, and 120 kVp. The resulting CTDI was 34 mGy. If the technique is changed to 100 kVp, how will the patient dose change?
A. Decrease patient dose
B. Increase patient dose
C. No change in patient dose
A. Decrease patient dose
Which of these technical changes will INCREASE the patient dose?
A. Increase kVp
B. Increase pitch
C. Increase beam width
D. Change to bone algorithm
A. Increase kVp
How will changing the total beam collimation from 8 mm to 16 mm affect patient dose?
A. Increase patient dose
B. Decrease patient dose
C. No change in patient dose
B. Decrease patient dose
While positioning a patient for a CT of the chest, the technologist does not center the patient in the center of the gantry. The scanner is using a variable mA. This error is most likely to result in:
A. Increased image magnification
B. Decreased contrast resolution
C. Beam- hardening artifact
D. Increased patient dose
D. Increased patient dose
Displayed on the technologist’s control panel when the CTDI for the scan is set to exceed predetermined dose notification values. This gives the technologist an opportunity to review the scanner settings before exposing the patient.
Dose notification.
Warning that is displayed on the technologist’s control panel when the cumulative CTDI for a series of scans is set to exceed 1,000 mGy for any specific location of the patient.
Dose alert.
When using a variable mA technique on a CT cervical spine, which of these situations is most likely to result in an increased dose to the patient?
A. Decreasing kVp for scan
B. Placing a lead shield around the patient’s waist
C. Patient breathing during the exposure
D. Leaving the patients arms in the exposure field.
D. Leaving the patients arms in the exposure field.
When using automatic dose modulation (variable mA), the scanner sets the mA throughout the scan based on:
A. Patient height/weight/BMI entered by the technologist
B. Attenuation readings acquired during the helical scan
C. Attenuation readings acquired during the scout images
D. Patient weight as measured by the scanner table.
C. Attenuation readings acquired during the scout images
If the technologist receives a “dose notification” during a CT scan, he or she should:
A. Notify the patient.
B. Notify the ordering physician
C. Review the exposure parameters
D. Review the examination ID.
C. Review he exposure parameters
When will a technologist receive a dose alert?
A. When the DLP for the exam is set to exceed a predetermined value.
B. When the cumulative CTDI for the scan is set to exceed 1,000 mGy
C. When the scanner is operated at a maximum tube current.
B. When the cumulative CTDI for the scan is set to exceed 1,000 mGy
If a technologist receives a “dose alert” during a CT scan, he or she should:
A. Consider reducing the patient dose
B. Consider cancelling the examination
C. Complete a pregnancy test on the patient
D. Complete a creatinine test on the patient.
A. Consider reducing the patient dose
When performing a CT of the neck, were should lead shielding be placed?
A. Over the anterior neck and chest
B. Over the posterior neck and chest
C. Over the anterior abdomen and pelvis
D. Over the entire abdomen and pelvis
D. Over the entire abdomen and pelvis
