4 Instrumentation and Quality Assurance

1) How often should the COR check be performed?

a. at least weekly b. before each patient c. every 6 months d. at least monthly

2) The abbreviation COR stands for:

a. circle of rotation b. center of region c. correction of rotation d. center of rotation

3) What is the minimum number of counts that should be obtained in a uniformity correction flood for a SPECT camera?

a. 10 K b. 10 million c. 30 million d. 60 million

4) Which of the following collimators will magnify an image?

a. flat field

b. diverging

c. converging

d. high resolution

5) Which of the following must be performed every 6 months at minimum?

a. COR

b. sealed source leak test

c. linearity of the dose calibrator d. area survey of hot lab

6) A dose calibrator must undergo repair or replacement if accuracy or constancy errors are:

a. present

b. greater than 5%

c. greater than 10%

d. greater than 20%

7) Accuracy of the dose calibrator must be tested:

a. on installation b. at least annually c. every six months d. both a and b

8) Linearity of a dose calibrator must be checked:

a. on installation b. quarterly c. every six months d. both a and c

9) Constancy of the dose calibrator must be tested:

a. daily b. quarterly c. weekly

d. every six months

10) A technologist wishes to evaluate the intrinsic uniformity of a camera used for planar imaging and is preparing a dose of

Tc. How much activity is sufficient for the image?

a. 2 mCi b. 200 µCi c. 20 mCi d. 10 µCi

11) Which has an effect on the CRT appearance?

a. energy of isotope b. dose calibration c. tag efficiency d. count rate

12) The advantages of using a

Co sheet source over a fluid filled flood source with

Tc added include:

a. it does not have to be prepared each day b. lower cost

c. shorter half life d. all of the above

13) Geometric dependence of a dose calibrator must be checked:

a. at installation b. daily

c. quarterly d. both a and c

14) What happens to image resolution as the distance between a patient and a parallel hole collimator decreases?

a. improves

b. worsens

c. does not change

15) What happens to image size as the distance between a patient and a parallel hole collimator decreases?

a. improves b. worsens c. does not change

16) What part of an imaging system emits light when it has absorbed a photon?

a. photomultiplier tube b. pulse height analyzer c. scintillation crystal d. collimator

17) Most of the photons emitted from the radiopharma- ceutical 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

18) To 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. pinhole

19) As septal length , septal penetration . a. increases, increases

b. increases, decreases

c. decreases, decreases

d. decreases, increases

e. both b and d

20) Which of the following degrade images?

a. septal penetration

b. photon scatter in the patient

c. increased patient to detector distance d. all of the above

e. b and c

21) A technologist covers the collimator (which is facing the ceiling) with absorbent paper and obtains a uniformity image using a liquid flood source with added

Tc.

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 photomultiplier tube c. subtle crystal crack

d. improper energy peaking

22) The first image described in question 21 showed resolution, and the second image obtained showed resolution.

a. extrinsic, intrinsic b. intrinsic, extrinsic

23) If 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

24) The time after a crystal has absorbed a photon before it able to respond to another event is called:

a. count rate b. distortion c. dead time d. sensitivity

25) The Z component of the signal in the photomultiplier tube will:

a. be processed by the pulse height analyzer b. be recorded on the CRT

c. be removed by the PMT d. all of the above

26) The purpose of the photomultiplier tube is to:

a. 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 angles

27) The purpose of the pulse height analyzer is to:

a. 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 angles

28) A camera with three pulse height analyzers will be most useful for imaging:

a.

Tc b.

Ga c.

In d.

Xe e. b and d

29) A 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 analyzer 30) A typical energy spectrum of

Tc from a patient con-

tains a broad peak around 90–140 keV that is not present on the energy spectrum from a point source of the same isotope. This represents:

a. the iodine escape peak b. the signal from

Tc c. lead X-ray peak d. Compton scatter

31) Image exposure time may be determined by:

a. a preset number of counts b. a preset time

c. information density d. all of the above

32) Which of the following is measured in millimeters?

a. energy resolution

b. spatial resolution

c. field uniformity

d. temporal resolution

33) The spatial resolution of an image is better with a energy isotope than with a energy isotope.

a. higher, lower b. lower, higher

34) If the energy range for

Cs at half maximum ranges from 620–695, what is the percent energy resolution, and is the system operating within acceptable limits?

a. 7.5, no b. 10.8, yes c. 11.3, yes d. 13.5, no

35) According to the curve for

Cs shown in Figure 4.1, what is the energy resolution of the system?

a. 6.9 b. 8.2 c. 10.5 d. 11.6

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000

560 580 600 620 640 660 680 700 720 740 760

Energy (keV)

Counts

Figure 4.1

36) Of 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 phantom

37) An orthogonal hole phantom cannot be used to test spatial linearity since it does not contain lead bars.

a. true b. false

38) When using a 150 µCi source of

Tc to check uniformity, a technologist measures the counts in one minute 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/µCi

39) A technologist performs an extrinsic uniformity correction on Monday and it shows a nonuniformity of 3%. On Tuesday, it is 8%. What would be the next step?

a. check the photopeak b. call for service on machine

c. remove the collimator and obtain intrinsic uniformity flood

d. a or c

40) For a system with inverse gain control, and a gain setting of 4, each division on the pulse height analyzer dials corresponds to:

a. 0.5 keV/division b. 1.0 keV/division c. 2.0 keV/division d. none of the above

41) For a system with true gain control , and a gain setting of 4, each division on the pulse height analyzer dial corresponds to:

a. 0.5 keV/division b. 1.0 keV/division c. 2.0 keV/division

42) An uptake probe operates with true gain and was calibrated with a gain setting of 8. If the gain setting is 16, and energies accepted by the pulse height analyzer are 294–342, what is the isotope under study?

a.

Tc b.

I c.

Tl d.

Xe

43) Why might a technologist use an asymmetric window around a photopeak?

a. to include other emissions b. to exclude the Compton edge c. to exclude Compton scatter d. none of the above

44) What energies are included if a 20% symmetric window is used for the 364 keV photopeak of

I?

a. 191–437

b. 328–400

c. 337–391

d. 344–384

45) The images acquired as a SPECT camera rotates around a patient are called:

a. reconstructions b. arcs

c. projections d. azimuth stops

46) With a matrix size of 64

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/pixel e. none of the above

47) What steps should be taken to reduce of remove 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 projections

48) The method of SPECT acquisition requires slightly more time, but has less blurring than the

method.

a. step and shoot, continuous rotation b. continuous rotation, step and shoot

49) As matrix size increases, what must also increase?

a. total imaging time

b. computer memory used

c. number of projections

d. all of the above

e. a and b

50) If the distance between 2 point sources placed on the camera surface is 35 mm, 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 0.5 mm of one another?

a. yes b. no

51) A technologist measures a standard of known activity in the dose calibrator three times. She subtracts back- ground 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 dependence

52) Records of dose calibrator checks must be kept for:

a. 3 years b. 5 years c. 10 years

d. as long as the license is valid 53) Survey meters must be calibrated:

a. before first use b. annually c. following repair d. all of the above

54) Survey meters must be checked for proper operation against a sealed source:

a. before each day of use b. weekly

c. monthly

d. every six months

55) Which of the following would be used to perform a survey of an area in which a small amount of radio- activity is expected to be present?

a. ionization chamber b. Geiger-Muller counter c. well counter

d. single probe counting system

56) An 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 dose

57) Most 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 crystals

58) Which of the following is a consideration when measuring samples in a well counter?

a. sample volume should be kept small and consistent among samples

b. samples should be contained in identical tubes c. amount of radioactivity should be low

d. all of the above

e. all except d

59) A dose calibrator is received in the Nuclear Medicine department following repair. A linearity test is performed on the dose calibrator, and the results are as follows.

33.9 mCi 17-Jan 08:00

30.3 mCi 17-Jan 09:00

9.2 mCi 17-Jan 19:00

2.3 mCi 18-Jan 07:00

0.5 mCi 18-Jan 20:00

0.2 mCi 19-Jan 03:00

What is the next step the technologist should take?

a. send the instrument for further repair b. accept the instrument for use

c. reject the instrument for use d. change the battery

60) What is the sensitivity of a camera that registers 28,137 cpm from a 120 µCi source if the background is 705 cpm?

a. 40 cpm/µCi b. 203 cpm/µCi c. 228 cpm/µCi d. 234 cpm/µCi e. 240 cpm/µCi

61) A check source is calibrated for June 13, 1995 at noon and contains 145 µCi of

Cs (Tp = 30 years). If a dose calibrator is used to measure that dose on June 13, 2001, what is the range of acceptable activities to prove that the accuracy is within 10%?

a. 115–130 µCi

b. 119–125 µCi

c. 120–133 µCi

d. 125–140 µCi

62) One 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. 18

63) Because of the relatively high energy of the photon detected in PET imaging, attenuation correction does not need to be performed.

a. True b. False

64) Which of the following can not be used for PET scanning?

a. a SPECT camera with high energy collimation b. a dedicated PET scanner

c. a SPECT camera with coincidence counting d. CT scanner

65) What part of a PET scanner quality control regimen is necessary for the computation of attenuation factors?

a. coincidence timing calibration b. normalization correction c. PMT gain adjustment d. blank scan

66) Which of the following describes random coincidence?

a. the simultaneous detection of annihilation photons originating from a single positron.

b. the simultaneous detection of annihilation photons originating from a single positron although one of the photons has been scattered before reaching the detector.

c. the simultaneous detection of photons originating from different positrons.

d. none of the above

67) Scintillation crystals for PET scanners are not made of:

a. sodium iodide

b. lutetium oxyorthosilicate

c. bismuth germinate

d. lead sulfate

e. b and d