ST:6 Flashcards
If someone is receiving 20 mRem/hr exposure at a distance of 3 m from a source, at what distance would they receive 500 mRem/hr exposure?
(a)0.36 cm
(b) 0.36 m
(c) 60 cm
(d) 0.60 cm
(e) 3.6 cm
(c) The inverse square law is represented by the equation I1(D1)^2, with I equaling intensity in mR/hr and D equaling distance. 20 mR/hr represents the I1 value, while 3m will be the D1 value. 500 mR/hr is the D2 value and the I2 value can be found by plugging in all the given information to the Inverse Square Law equation and solving for the missing variable.
20 mR/hr (3 m)^2 = 500 mR/hr (I2)^2
(I2)^2 = 20 mR/hr (9m) = 0.36 m
500mR/hr
Take the square root of both sides to get I2 = 0.60m
How many cm = 0.60 m x 100 cm/1 m = 60 cm?
If an area survey reveals an ambient radiation level of 7 mRem/hr, which of the following radioactive signs would be the best choice to display on the door leading to this area?
(a)”Caution: Radioactive Materials”
(b) “Caution: Radiation Area”
(c) “Caution: High Radiation Area”
(d) “Grave Danger: Very High Radiation Area”
(e) “Caution: Very High Radiation Area”
(b) The “Caution: Radioactive Materials” sign is used in any area where certain quantities of radioactive materials are used or stored. The “Caution: Radiation Area” sign is used in areas where an individual could receive more than 5 mRem (0.05 mSv) in 1 hr at 30 cm from a radioactive source. The “Caution: High Radiation Area” signs are used where an individual could receive more than 100 mRem/hr (1 mSv) in 1 hr at 30 cm from a radioactive source. Since the ambient radiation exposure is between 5 mRem/hr and 100 mRem/hr, the appropriate caution sign would be “Caution: Radiation Area.”
An ionization chamber is left in integral mode for 10 min and records a total dose of 3 mRem. Which of the following area posting signs should be used on the door leading into this area?
(a)”Caution: Radiation Area”
(b) “Caution: Radioactive Materials”
(c) “Caution: High Radiation Area”
(d) “Grave Danger: Very High Radiation Area”
(e) “Caution: Very High Radiation Area”
(a) The “Caution: Radioactive Materials” sign is used in any area where certain quantities of radioactive materials are used or stored. The “Caution: Radiation Area” sign is used in areas where an individual could receive more than 5 mRem (0.05 mSv) in 1 hr at 30 cm from a radioactive source. The “Caution: High Radiation Area” signs are used where an individual could receive more than 100 mRem/hr (1 mSv) in 1 hr at 30 cm from a radioactive source. Since the integral dose in 10 min is 3 mrem/hr, this implies that the total dose for 1 hr is 6 times this amount or 18 mRem/hr. Therefore, the radiation exposure is between 5 mRem/hr and 100 mRem/hr, and the appropriate caution sign would be “Caution: Radiation Area.”
Which of the following area posting signs would NOT normally be found in a hospital?
(a)”Grave Danger: Very High Radiation Area”
(b) “Caution: Radiation Area”
(c) “Caution: High Radiation Area”
(d) “Caution: Radioactive Materials”
(e) “Caution: Very High Radiation Area”
(a) In areas where personnel would receive life-threatening doses of radiation such as levels over 500 R/hr, the sign “Grave Danger: Very High Radiation Area” would be used. It is unlikely that materials with an activity of lethal dose levels would be stored on the premises of a hospital.
Which of the following type of survey instruments would be best to use to survey a spill for removable contamination in a hot lab area where radioisotopes are being stored?
(a)G-M detector
(b) personal pocket dosimeter
(c) well counter with a wipe test
(d) dose calibrator with a wipe test
(e) cutie pie
(c) G-M detectors are used to survey large areas for contamination that may not always be removable. Pocket dosimeters are used to measure personnel exposure. Dose calibrators are used to measure activity in patient doses. Scintillation probes can be used to detect removable and non-removable contamination at a higher efficiency than G-M detectors because of its use of a sodium iodide-thallium crystal. Most often, wipe tests with a well counter are used to check for removable contamination.
Four HVLs reduce the amount of incident radiation exposure to what?
(a)6.5%
(b) 12.25%
(c) 3.125%
(d) 25%
(e) 50%
(a) The half-value layer (HVL) is the amount of material needed to reduce radiation intensity by half. Following this logic, 4 HVLs reduce the amount of incident radiation to a transmission factor of 0.0625 or 6.25%.
Which of the following is NOT required to be included in the records of a radioactive package receipt check-in process?
(a)name of radioisotope
(b) name of patient
(c) amount of activity
(d) external wipe check
(e) internal wipe check
(b) When packages are received, they are inventoried by recording the name of the radioisotope, amount of activity, and results of wipe checks as mandated by NRC regulations. Patient name is not relevant at this point because you are simply taking inventory.
If a package is reading 2 mRem/hr at a distance of 2 m, what is the appropriate DOT label for this package?
(a)No labeling is required.
(b) DOT I
(c) DOT III
(d) DOT II
(e) DOT IV
(c) The DOT I transport index or exposure rate at 1 m from the package is mandated to be zero. The DOT II transport index is mandated to be more than 0 but less than 1 mR/hr at 1 m. DOT III is mandated to be more than 1 mR/hr but less than 10mR/hr at 1 m. This package would fall under the DOT III. DOT I (white) At contact, not more than 0.5 mR/hr At 3 feet (1 m), no detectable radiation (NDR) DOT II (yellow) At contact, not more than 50 mR/hr At 3 feet (1 m), not more than 1 mR/hr DOT III (yellow) At contact, not more than 200 mR/hr At 3 feet (1 m), not more than 10 mR/hr
The purpose of the transport index is to:
(a)indicate the highest activity of the contents at 1 m from the surface
(b) list the final destination of the package
(c) not to give emergency personnel information about the contents of the package in an accident
(d) not to list the radioisotopes in the package
(e) document wipe check information
(a) The transport index indicates to all handlers the degree of care that should be taken when handling the package. This index is quantified by an exposure reading taken 1 m from the package or source.
If a patient who is having a bone scan urinates on the floor next to a camera, what would be the best course of action to reduce radiation exposure?
(a)Remove the spill with some absorbent material and cover any residual activity with a lead plate or lead apron.
(b) Move the camera away from the spill.
(c) Let the radioactive urine decay to background.
(d) Notify the referring physician of a medical event.
(e) Notify the NRC of a medical event.
(a) When decontaminating a liquid spill that can include potentially radioactive biologic waste (urine, emesis, etc) expelled from a patient, the spill can be cleaned up with absorbent material. When contamination cannot be completely removed with thorough cleaning, lead plates or aprons can be used to cover the area of the spill.
Which DOT radioactive labeling is entirely white?
(a)DOT III
(b) DOT II
(c) DOT I
(d) DOT IV
(e) DOT V
(c) According to the Department of Transportation, the radioactive label designated as totally white is DOT I. DOT I denotes packages with less than 0.5 mR/hr exposure rate at the surface and with no detectable radiation (NDR) at 1 m.
Which absorber would be the best to use to shield strontium-89?
(a)cardboard
(b) No shielding is required.
(c) lead
(d) plexiglas
(e) paraffin
(d) Strontium-89 is a pure beta emitter. Lead shielding cannot be used to block beta particles because of the production of bremsstrahlung radiation caused by the interaction of beta particles with dense materials such as lead. Cardboard is not dense enough to stop the torturous path of beta particle. Plexiglass is ideal because of its density since bremsstrahlung reactions would be kept to a minimum.
Which of the following indicates the AMOUNT of radioactive substance in a sample or source?
(a)total effective dose
(b) exposure
(c) absorbed dose
(d) dose equivalent
(e) activity
(e) Exposure is specifically defined as the amount of charge in the air from interactions with X or gamma radiation, 0 to 3 MeV. The unit of exposure is the roentgen: 1 R = 2.58 x 10^-4 c/kg. However, activity indicates the amount of radioactive substance in a sample or source. The units are the curie or becquerel.
If the exposure rate is 25 mRem/hr and the person being exposed is present for 25 min, what is his/her total exposure?
(a)24 mRem
(b) 10.4 mRem
(c) 12.5 mRem
(d) 5.2 mRem
(e) 27 mRem
(b) 25 mRem/hr (1 hr/60 min) x 25 min = 10.4 mRem
What is 120 Sv in millirads (Quality Factor [QF] = 1)?
(a)8.3 x 10^-8 mrad
(b) 12 million mrad
(c) 1.2 million mrad
(d) 120,000 mrad
(e) 12,000 mrad
(b) 1 Sv = 1 Gray = 100 rad
1 Sv = 100 Rem
120 Sv = (100)120 rad
120 Sv = 12,000 rad = 12,000,000 mrad
An alpha particle is simliar to what?
(a)an electron
(b) a proton
(c) a hydrogen atom minus its neutron
(d) a helium atom minus its neutrons
(e) a helium atom minus its electrons
(e) When an alpha particle decays, it loses the two electrons it originally had. Helium nuclei consist of the same number of protons and neutrons.
A higher or lower sensitivity is affected by all of the following EXCEPT:
(a)properly set Pulse Height Analyzer (PHA) and window width
(b) collimator design
(c) thickness of camera crystal
(d) instrument deadtime
(e) improperly set Pulse Height Analyzer (PHA) and window width
(a) The thickness of the crystal, collimator design, and instrument deadtime all affect sensitivity and can cause it to be higher or lower from day to day. However, a properly set pulse height analyzer with a proper window around the main peak will not affect the sensitivity and make it higher or lower from day to day.
Geometric variation, on a dose calibrator, should be performed:
(a)hourly
(b) at installation and yearly
(c) quarterly
(d) daily
(e) at installation and after repair
(e) Geometric calibration is performed at installation, whenever a change is made in the type of vial or syringe used in radiopharmaceutical processing, and after the chamber is repaired.
Photomultiplier tube drift is associated with which of the following:
(a)auto-voltage stabilization
(b) inverse gain
(c) energy correction
(d) linearity correction
(e) auto-gain stabilization
(e) The amplifications of electrons in photomultiplier tubes (PMTs) and, therefore, PMT output, are affected by many factors: temperature, PMT age, and Earth’s magnetic field or unshielded MRIs. Automatic gain stabilization, if not correct, can cause tube drift to occur.
A paralyzable counting system will:
(a)exhibit a nonlinear threshold response
(b) never plateau and never obtain a peak count
(c) plateau with no decrease in countrate as activity increases, which is the peak count
(d) not exhibit any countrate difference
(e) decrease in count rate after some peak in countrate is obtained
(e) In a paralyzable system, as the activity increases, the count rate increases to a maximum valve and then actually starts decreasing at higher activity levels.
Sources of intrinsic non-uniformity include all of the following EXCEPT:
(a)”mistuned” PMTs
(b) regional variations in Z-pulse amplitude
(c) spatial distortion
(d) linearity
(e) mapping malfunction
(d) The three main sources of non-uniformity are “mistuned” PMTs, regional variations in Z-pulse amplitude (spatial distortion), and edge packing. Linearity is a separate issue and not a part of uniformity assessment itself.
What is added to NaI crystals to allow them to scintillate at room temperature?
(a)Tl
(b) Xe
(c) Ce
(d) Ag
(e) BGO
(a) NaI (Tl) scintillation camera systems will have a 8% and 12% energy resolution. Thallium functions as an actuator that allows the creation of additional “energy states” within the crystal. Crystals are very sensitive to thermal and mechanical shocks.
What maximum percentage difference is acceptable for most regulatory agencies for all four dose-calibrator QC checks?
(a)+-5%
(b) +-10%
(c) +-7%
(d) +-15%
(e) +-20%
(b) The limit for % difference is +- 10%, according to the NRC regulations. However, it may be +- 5% per manufacturer recommendations, which the NRC also says must be adhered to.
Extrinsic quality control on a camera means quality control is done:
(a)automatically overnight
(b) without the collimator on
(c) inside the camera
(d) outside the camera
(e) with the collimator on
(e) Extrinsic testing allows evaluation of the total system as it is used clinically, including the collimator. When a collimator is used during assessment, a source having a uniform radionuclide distribution is placed on the collimator.
Linearity correction involves:
(a)diagonal lines
(b) horizontal lines
(c) horizontal and vertical lines
(d) vertical lines
(e) diagonal and vertical lines
(c) Correction involving evaluating the straightness of both horizontal and vertical lines while using a phantom.
Dose-calibrator constancy should be performed:
(a)monthly
(b) daily
(c) weekly
(d) quarterly
(e) hourly
(b) Constancy of a dose calibrator is performed every day that it is used. This is usually done using a long-lived radioisotope and comparing daily values to previously measured values.
Which of the following quantitative renal techniques require(s) the calculation of kidney depth?
I. Schlegel technique
II. Gates’ method
III. Two-compartment effective renal plasma flow (ERPF) determination
IV. Russell’s glomerular filtration rate (GFR) method
(a)I
(b) II and III
(c) III and IV
(d) II and IV
(e) I and II
(e) Schlegel, et al., Brodkey, et al., and Gates described non-invasive isotopic methods for the estimation of GFR and ERPF without blood or urine sampling. These methods allow determination of these parameters separately for each kidney and derive values for global renal function.
Which of the following functional images represents the magnitude of ventricular contraction?
(a)non-phase image
(b) paradox image
(c) phase image
(d) stroke-volume image
(e) amplitude image
(e) The amplitude image is superior to the simple stroke volume image because it shows the actual volume of blood ejected from each region of the heart.
The background ROI used in determining percentage gastroesophageal (GE) reflux is placed over the:
(a)lower left lung
(b) small intestine
(c) right hepatic lobe
(d) upper esophagus
(e) lower esophagus
(a) Background subtraction is used to enhance image quality and increase statistical reliability for quantitative studies such as gastroesophageal reflux studies. The lower left lung servers as an appropriate background region of interest close to but not within the field of view of imaging the esophagus and stomach.
Geometric mean is sometimes used in quantization because it corrects for:
(a)the size and shape of the organ
(b) background activity
(c) radioactive half-life
(d) radioactive decay
(e) attenuation and organ depth
(e) The geometric mean calculation and use in quantitative studies allow for a sense of organ depth and where in an organ any possible attenuation is occurring. This could be due to contrast media, which could be in a part of the colon but not the entire colon.
Given a heart rate of 85 bpm, if a 24-frame gated heart study is acquired, the length of each frame in milliseconds is:
(a)0.06 msec
(b) 0.3 msec
(c) 705 msec
(d) 29 msec
(e) 0.03 msec
(d) With the patient heart rate at 85 bpm, each beat is 0.7058 sec (60 sec/85 beats = 0.7058 sec). Divide this by 25 frames to get 0.029 sec and then convert to msec by multiplying by 1000 to get 29 msec.
Concentric ring artifacts in a reconstructed SPECT image may be caused by:
(a)improper collimation
(b) inadequate uniformity
(c) correction of large statistical fluctuations in the projection data
(d) too few angles of reconstruction
(e) too many angles of reconstruction
(b) Extrinsic flood field uniformity correction is performed to prevent ring artifacts.
In processing a myocardial perfusion study, a slice from which body axis is used to identify the degree to which the heart points to the left and to construct slices in the three opposing cardiac planes?
(a)horizontal long axis
(b) transaxial
(c) vertical long axis
(d) short axis
(e) horizontal short axis
(b) For automatic reorientation of the heart, identify the left ventricle in the transaxial images using a threshold-based approach.
The MOST important purpose of center of rotation offset correction is to:
(a)eliminate the effects of detector tilt in the reconstructed images
(b) minimize count sensitivity variations from one area of the crystal to another
(c) ensure that all pixels are uniformly sized over the entire field of view
(d) align the center of the computer matrix with the mechanical axis of rotation
(e) maximize count sensitivity variations from one area of the crystal to another
(d) The center of rotation (COR) offset correction makes certain that the COR of the camera matrix corresponds to the COR of the camera heads.
The x- and y-axes of a circumferential profile curve are, respectively:
(a)x-axis-bull’s eye quadrant, y-axis: % maximum counts
(b) x-axis-time, y-axis: activity
(c) x-axis-segment of the myocardium, y-axis: maximum counts
(d) x-axis-rest, y-axis: stress
(e) x-axis-maximum counts, y-axis: segment of the myocardium
(c) In a circumferential profile curve, segments of the myocardium are listed on the x-axis and the maximum counts related to these segments are plotted on the y-axis.
Diaphragmatic attenuation may be reduced by:
(a)360 acquisition
(b) supine acquisition
(c) delayed imaging
(d) prone acquisition
(e) giving a bolus injection
(d) Imaging in the prone position minimizes attenuation artifacts in myocardial imaging where the inferior wall of the heart may be shadowed by breast tissue or the diaphragm.
Which of the following is a definition of sensitivity of a diagnostic test?
(a)how good the test is at detecting a true negative
(b) how good the test is at detecting a true positive
(c) how good the test is at detecting the difference between a true negative and a true positive
(d) how good the test is at detecting something
(e) how good the test is an detecting idiopathic conditions
(b) Sensitivity is the percentage or fraction of ill patients who have a positive test. Thus, sensitivity is how good a test is at detecting a true positive. Specificity is how good a test is at detecting a true negative.
In a patient with pulmonary embolism, the perfusion and xenon ventilation lung images will demonstrate the following findings:
Perfusion - Ventilation
(a)Normal - Normal
(b) Normal - Abnormal tracer retention
(c) Normal - Ventilation defects
(d) Perfusion defects - Abnormal tracer retention
(e) Perfusion defects - Normal
(e) Ventilation study usually presents as normal (uniform and symmetrical uptake and wash-out in all three phases) in cases of pulmonary embolism (PE). Mismatching areas of activity (usually two or more segmental defects) in the perfusion study are indicators for PE.
Of the following, the biggest disadvantage of 133Xe (xenon gas) for performing lung ventilation studies is its:
(a)rapid lung clearance
(b) surface contamination
(c) high cost
(d) unavailability
(e) trapping and shielding requirement
(e) Pricing and availability have forced 133Xe into prominence. The more straightforward wash-in/wash-out method is preferred and can be used even on comatose patients.
Which of the following statements about radiolabeled aerosols used for lung ventilation imaging is TRUE?
(a)The particles are deposited in ventilated areas of the lungs.
(b) It is necessary to trap any radiolabeled particles exhaled by the patient.
(c) Particle sizes range form 30 to 90 um in diameter.
(d) Deposition of particles in the central airway is never a problem with lung aerosol studies.
(e) Contamination concerns are not warranted.
(a) Aerosols are deposited in the bronchial tree in relation to particle size, air flow rates, and turbulence. The delivery tubing effectively filters out larger particles 10-15 um in diameter. Smaller particles are deposited in the larger airways during both inspiration and expiration. Particles less than 2 um can reach the alveoli and be deposited there, while even smaller particles, less than 0.1 um, probably escape in the expired air.
