Common nuclear medicine artifacts.

1. Fellow’s review series
(Artifacts in nuclear medicine
)
Miad Alsulami.MD.FRCPC
Wednesday, December 16, 2020

2. Objectives
To address :
1. Types of artifacts .
2. Causes of artifacts.
3. Most common artifacts in nuclear medicine.
4. The impact of the artifacts on images.
5. How to correct them.

3. • Quality control in nuclear medicine is important.
• it is important to remain aware of artifacts that are directly related to
the patient and need special consideration.
• The diagnostic accuracy of nuclear medicine reporting can be
improved by awareness of these patient-related artifacts.
• Both awareness and experience are also important when it comes to
detecting and identifying normal (and abnormal) variants.

4. Causes of artifacts
1. Camera dependent artifacts.
2. Radiopharmaceutical dependent artifact
3. Patients related artifacts .

5. • Gamma cameras are fairly complex devices and a malfunction in any
component can result in image artifacts.
• Although some artifacts are visible on patient scans, because we
expect to see variations in radioactivity distribution in patients,
clinical scans of patients cannot be relied upon to show identifiable
artifacts.
• Daily quality control acquisitions of uniform sources are critical
because they lay bare problems that may go unnoticed in clinical
scans despite the fact that they degrade the scans, sometimes in
important ways.

6. Camera dependent
artifacts

7. identify the defect.
the source of the defect.
the solution.

8. CASE 1
• A technologist is preparing to perform an intrinsic flood, so he has
removed the collimator. He leans over the detector to attach the
point source holder and his mobile phone slides out of his shirt
pocket and lands on the detector.

10. • Cracked crystal.
• Call the vendor to replace the crystal .

11. CASE 2
• One of the gamma cameras in the department is functioning well and
passes all daily quality control extrinsic flood images with flying
colors. Every month, however, a much higher count intrinsic flood is
acquired .

13. • Hygroscopic Crystal.
• sodium iodide crystals are hygroscopic. This means that they absorb
water. Unfortunately, when they absorb water they discolor
(specifically, they turn yellow).
• Call the vendor to replace the crystal .

14. CASE 3
• Bone scan to rule out metastasis.

16. • Malfunction PMT.
• Call the vendor.

17. CASE 4

18. • Upon completing a daily flood, the technologist notes a failing result
and visually sees a well-defined grid pattern
• Looking back on the last several weeks of daily floods, this does
appear to have become progressively worse and the resulting
uniformity measurements have been creeping up to the point of
exceeding the passing threshold this morning.

19. • Non uniformity.
• Call the vendor to obtain high flood count to calibrate the camera.

20. • service is called in and requests a radioactive source with which to
perform gain calibrations. After this procedure, a daily flood is
repeated and passes easily.

21. CASE 5
123 MIBG SCAN in pediatric paitent

22. • The technologist showed you the images? What is your next step?

23. • Repeat acquisition with correct photo-peak .
• The energy window might be on wrong setting for Tc99m rather than
I123.
• by setting the photo peak too low, the image collects more scattered
photons.
• image with scattered photons looks fuzzy and indistinct.

25. CASE 6

26. • Motion artifact.
• Repeat acquisition .

27. CASE 7
• A potential living related kidney donor is being worked-up and
presents for measurement of glomerular filtration rate (GFR).
• The procedure involves injection of a radiopharmaceutical with
measurements of blood concentration of radioactivity at 1 and 3
hours after injection.
• The procedure is completed and the GFR is measured to be 60
mL/min, which is significantly lower than normal and discordant with
the patient’s 24-hour urine collection, which calculated GFR to be 120
mL/min.

28. • What is your next step?

30. • partial infiltration of the injected dose.
• Repeat the study .

31. • Because most radiopharmaceuticals are given intravenously and
because it is fairly common for an intravenous injection to be
infiltrated (at least partially), it is important to always consider
whether an infiltration may have occurred. When the injection site is
in the field of view, it is quite obvious because an infiltration is easily
recognizable. In cases where accurate quantification is important, it is
usually a good idea to specifically image the injection site to assess for
infiltration.

32. CASE 8

33. • Reconstrected SPECT tranxial slice for a point source showed small
circle in the field of view.

34. • Center of rotation error.
• The camera needs to be calibrated.

35. CASE 9
131 post therapy scan

37. • Streak artifacts with FBP.
• Repeat reconstruction with iterative mode.

39. CASE 10
• A patient with a carcinoid tumor is referred for an In-111
pentetreotide scan. In evaluating the pelvis looking for the colonic
primary, the resident notes a photopenic area surrounding the
bladder.

41. • Halo artifact , common artifact with iterative reconstruction.
• Reconstruct the images with FBP.

43. CASE 11

44. • As part of the daily quality control process, an image is acquired with
a test source in place. Commonly Ge-68 rods are used because Ge-68
decays (with about 271-day half-life) to Ga-68, which decays by β +
emission. The image is displayed as a and a diagonal band with no
events is noted.

45. • PMT malfunction.
• Call the vendor.

46. CASE 12

47. • Attenuation correction artifacts.
• With metallic implants always exam the NAC images.

48. Radiopharmaceutical dependent
artifact

49. CASE 1

50. • Chemical impurity with AL
• QC spot test of RF should be performed
• Normal limit?

51. CASE 2

52. • Perfution scan with hot clots
• Cause?
• Soultion?

53. CASE 3

54. • Bone scan with radiochemical impurity (free Tc)
• QC.

55. CASE 4

56. • VQ perfusion scan.
• Redistribution of the tracer due to paiten’s postion

57. CASE 5

58. • DMSA scan with Radiochemical impurity( insoluble colloid)
• Do QC.

59. Patient's related artifacts

61. • Bowel activity secondary to previous nuclear scan(MIBI)
• Other differentials?

63. • Intense MDP uptake in the lower calf
• Calciphylaxis.

65. • Sickell cell anemia with autoinfarction

67. • Colorectal cancer with colovesicular fisula

68. TEST YOUR SELF!

70. Ga67 Scan

73. REFRANCES :
1. Altered biodistribution of radiopharmaceuticals used in bone
scintigraphy.
2. Patient-related pitfalls and artifacts in nuclear medicine imaging.
3. Nuclear medicine ,practical physics ,artifacts and pitfalls.

74. EXTRA READINGS:
• Artifacts and Pitfalls in Myocardial Perfusion Imaging.
• Patient-related pitfalls and artifacts in nuclear medicine imaging.
P.S: All my presentations are available on slideshare (MiadAlsulami)

75. THANK YOU !