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How often should the COR check be performed?
a) at least weekly
b) before each patient
c) every 6 months
d) at least monthly
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Terms in this set (51)
The advantages of using a Co57 sheet source over a fluid-filled flood source with Tc99m added include: a) it dose not have to be prepared each day b) lower cost c) shorter half-life d) higher energyit does not have to be prepared each dayGeometric dependence of a dose calibrator must be checked: a) at installation b) daily c) quarterly d) annuallyat installationWhat happens to the image size as the distance between a patient and a parallel-hole collimator decreases? a) improves b) worsens c) does not changeimprovesWhat happens to the image size as the distance between a patient and parallel-hole collimator decreases? a) increases b) decreases c) does not changedoes not changeWhat part of an imaging system emits light when it has absorbed a photon? a) PMT b) pulse height analyzer c) scintillation crystal d) collimatorscintillation crystalMost of the photons emitted from the radiopharmaceutical which has been administered to a patient: (a) Do not contribute to the final image (b) Are received by the sodium iodide crystal (c) Are converted to a voltage signal (d) (a) and (b) (e) (b) and (c)do not contribute to the final imageTo obtain high-resolution images of a small organ, gland, or joint, which collimator will be most useful? a) low energy parallel hole b) flat field c) diverging d) pinholepinholeWhich instrument should be used to determine the location of a Tc99m spill? a) GM survey meter b) portable ionization chamber c) nal well counter d) pocket dosimeterGM survey meterA technologist covers the collimator (which is facing the ceiling) with absorbent paper and obtains a uniformity image using a liquid flood source with added Tc99m. A round cold spot is seen on the image. Subsequently the technologist removes the collimator, turns the camera face down, and obtains another image using a point source placed on the floor. This image appears uniform. What is the most likely cause of the cold spot on the first image? a) collimator defect b) decoupled PMT c) subtle crystal crack d) improper energy peakingdecoupled PMTIf two photons strike a sodium iodide crystal at the same time, what will occur? (a) Neither event will trigger production of light. (b) The system will perceive only one event which will contain the summed energy of both photons. (c) Both will be correctly perceived. (d) None of the above.The system will perceive only one event which will contain the summed energy of both photons.The time after a crystal has absorbed a photon before it is able to respond to another event is called: (a) Count rate (b) Distortion (c) Dead time (d) Sensitivitydead timeThe purpose of the photomultiplier tube is: a) to keep any of the electrical signal which resulted from scatter or background from contributing to the final image b) to convert light into an electrical signal and to magnify that signal c) to convert radioactivity into light d) to filter out photons which strike the crystal from oblique anglesto convert light into an electrical signal and to magnify that signalThe purpose of the pulse height analyzer is: a) to minimize the amount of scatter radiation in the final image b) to convert light into an electrical signal and to magnify that signal c) to convert radioactivity into light d) to filter out photons which strike the crystal from oblique anglesto minimize the amount of scatter radiation in the final imagea camera with 3 pulse height analyzers will be most useful for imaging: a) Tc99m b) Ga67 c) In111 d) Xe133Ga67A technologist has set a 15% symmetric window for a 140 keV photopeak. What will happen to a 158 keV signal? a) it will be accepted by the pulse height analyzer b) it will be rejected by the pulse height analyzerit will be rejected by the pulse height analyzerA typical energy spectrum of Tc99m from a patient contains a broad peak around 90-140 keV that is not present on the energy spectrum from a point source of the same isotope in air. This represents: a) the iodine escape peak b) the signal from Tc99m c) lead xray peak d) Compton scatterCompton scatterWhich of the following can be measured in mm? a) energy resolution b) spatial resolution c) field uniformity d) temporal resolutionspatial resolutionThe energy resolution of an image is better with a _____ energy isotope than with a _____energy isotope. (a) Higher, lower (b) Lower, higherhigher, lowerOf the following types of transmission phantoms, which one requires the fewest images to test the spatial resolution over the entire detector face? a) hine-duley phantom b) four- quadrant bar phantom c) parallel-line equal-space phantom d) orthogonal-hole phantomfour quadrant bar phantomAn orthogonal-hole phantom cannot be used to test spatial linearity since it does not contain lead bars. (a) True (b) FalseFalseWhen using a 150 μCi source of 99m Tc to check uniformity, a technologist measures the counts in 1 min as 53,125. If the background in the room is 352 cpm, what is the sensitivity of the system? (a) 351 cpm/μCi (b) 354 cpm/μCi (c) 356 cpm/μCi (d) 360 cpm/μCi351 cpm/uCiOn Monday the extrinsic uniformity flood for a gamma camera has a uniformity of 3%. On Tuesday the uniformity is 8%. The technologist then verifies that the photopeak is still centered in the energy window. What should be the next step? a) scan a bar phantom instead b) call for service c) remove the collimator and obtain an intrinsic uniformity flood.remove the collimator and obtain an intrinsic uniformity floodWhy might a technologist use an asymmetric energy window around a photopeak? a) to include other emissions b) to exclude edge packing c) to exclude Compton scatter d) to increase the count rateto exclude Compton scatterWhat energies are included if a 20% symmetric window is used for a 364 keV photopeak of I 131? a) 191-437 b) 328-400 c) 337-391 d) 344-384328-400The images acquired as a SPECT camera rotates around a patient are called: a) reconstructions b) arcs c) projections d) aziumth stopsprojectionsThe matrix size of 64x64 and two sources placed 30 cm apart, there are 44 pixels between the activity peaks on the activity profile that is generated. What is the pixel size a) 6.8 cm/pixel b) 6.8 mm/pixel c) 1.4 mm/pixel d) 0.14 cm/pixel6.8 mm/pixelWhat steps should be taken to reduce a star artifact from reconstructed SPECT images? a) decrease the matrix size b) increase the time per projection c) increase the radius of projection d) increase the number of projectionsincrease the number of projectionsThe _________ method of SPECT acquisition required slightly more time but has less blurring than the _______ method. a) step and shoot, continuous rotation b) continuous rotation, step and shootstep and shoot, continuous rotationIn SPECT imaging, if the image matrix size is increased from 64x64 to 128x128, which of the following is true? a) total imaging time may need to be increased b) spatial resolution will decrease c) image reconstruction will be faster d) image file size will decrease e) count rate will decreasetotal imaging time may need to be increasedIf the distance between two point sources placed on the camera surface is 35 cm in both the x and y directions and the number of pixels between their activity profile peaks is 52 in the x axis and 55 in the y axis, are the pixel dimensions in the x and y direction within 0.5mm of one another? yes or noyesA technologist measures a standard of known activity in the dose calibrator three times. She subtracts background from each measurement and compares these measurements to the decay corrected activity of the standard. This was a test of: (a) Constancy (b) Linearity (c) Accuracy (d) Geometric dependenceaccuracyRecords of dose calibrator checks must be kept for: (a) 3 years (b) 5 years (c) 10 years (d) As long as the license is valid3 yearsin PET imaging, what is the outcome of imaging positrons with a long range of travel before undergoing annihilation. a) increased rate of random detection b) increase in streaking artifacts c) mispositioning where the radioactivity is located d) improved image resolutionincrease in streaking artifactsSurvey meters must be checked for proper operation against a sealed source: a) before each day of use b) weekly c) monthly d) every 6 monthsbefore each day of usewhich of the following would be used to perform a survey of an area in which a small amount of radioactivity is expected to be present? a) ionization chamber b) gm counter c) well counter d) single probe counting systemgm counteran ionization chamber with a relatively low applied voltage from the anode to the cathode has a low efficiency and is therefore best for measuring: a) low exposure rates b) high exposure rates c) background radiation d) absorbed dosehigh exposure ratesMost well counters measure radioactivity by use of: (a) An applied voltage from anode to cathode (b) A sodium iodide crystal (c) A silver halide layer (d) Thermoluminescent crystalsA sodium iodide crystalWhen measuring samples in a well counter, which one of the following is true? a) sample volumes should be large b) samples should have high radioactivity c) sample geometry should be consistent d) sample containers don't affect the measurementsample geometry should be consistentA check source is calibrated for June 13, 2000, at noon and contains 145 μCi of 137 Cs (T 1/2 = 30 years). If a dose calibrator is used to measure that dose on June 13, 2006, what is the range of acceptable activities to prove that the accuracy is within 10 % (6-year decay factor is 0.871.)? (a) 113-139 μCi (b) 119-125 μCi (c) 120-133 μCi (d) 125-140 μCi119-125 μCi1 ml of a solution is assayed and contains 206 mCi. If the solution is diluted to 9 ml and the activity is now 170, what is the geometric correction factor? (a) 0.65 (b) 1.2 (c) 10.9 (d) 181.2If the energy range for 137 Cs at half maximum ranges from 623 to 700, what is the percent energy resolution, and is the system operating within acceptable limits? (a) 7.5, no (b) 10.8, yes (c) 11.6, yes (d) 13.5, no11.6, yes