1. Problems and Pitfalls in the Interpretation of PET/CT
George Segall, M.D.
Stanford University

2. False Negative FDG PET
Low-grade glioma
Low-grade lymphoma
Bronchoalveolar lung cancer
Hepatoma
Renal cell carcinoma
Prostate cancer
Histology
Size
< 10 mm
Post prandial scans
Hyperglycemia
> 150 mg/dL

3. Post Prandial Scan
57 year old man with stage IV left tonsillar scca treated with chemoradiation 21 months ago. Patient was lost to follow-up until he was referred for PET/CT. Coronal images show low FDG uptake in the brain, and high uptake in the heart and skeletal muscles.

4. Post Prandial Scan • Fasting: Euglycemia 6 hours Diabetes 12 hours
fed 04/25
fasting 05/08

5. Fasting Scan in a Diabetic
51 year old man with colon polyps and a stricture referred for PET/CT to evaluate for possible malignancy. Fasting blood glucose level = 289 mg/dL. Coronal images show a good quality scan with normal FDG biodistribution.

6. Hyperglycemia
69 year old man with 2.3 cm RUL NSC lung cancer. FBS = 309 mg/dL. No insulin was given. Coronal images show a good quality scan with high FDG tumor uptake (max SUV 5.4)

7. Insulin Effect on FDG uptake
63 year old man with 5 cm RUL adenocarcinoma. FBS = 299 mg/dL; 90 minutes after 15u of reg insulin IV FBS = 179 mg/dL at which time FDG was injected. Coronal images show a “muscle scan” with faint tumor uptake (max SUV = 2.0)

8. False Positive FDG PET
Physiologic
Benign Neoplasm
Adenoma
Inflammatory
Granuloma, sarcoid, rheumatoid
Miscellaneous
Prosthesis, grafts
Fractures

9. Physiologic Uptake
FDG subcutaneous infiltration 3

10. Physiologic Uptake
Tonsillar Hyperplasia 3

11. Physiologic Uptake
Talking
Nakamoto. Radiology 2005;234;

12. Physiologic Uptake: Brown Fat

13. Brown Fat • What is brown fat? • Methods to reduce FDG uptake
Reassurance
Heat
Sedatives
Beta blockers

14. Adenoma
74 yr old man with seizures and recent cognitive disorder

15. Adenoma 
70 yr old man 2 months post chemoXRT for R piriform sinus cancer stage 3, T3N2M0.

16. Adenoma
63 y/o man 4 months post chemoXRT for R tonsil cancer T2N1M0

17. Adenoma Adrenal adenoma SUV adrenal 4.0 SUV liver 2.2
51 yr old man with colon cancer treated with rectosigmoid colectomy and adjuvant chemotherapy.

18. Adenoma
82 year old man with wt loss and liver mass

19. Question 1
Which of the following neoplasms have been associated with focal FDG uptake in the colon?
Hyperplastic polyp
b. Adenomatous polyp
c. Adenocarcinoma
d. All of the above

20. Question 1 The correct answer is d. All of the above
Gollub et al. Combined CT Colonography and 18F-FDG PET of Colon Polyps: Potential Technique for Selective Detection of Cancer and Precancerous Lesions. AJR Am J Roentgenol Jan;188(1):130-8.
Friedland et al. 18-Fluorodeoxyglucose positron emission tomography has limited sensitivity for colonic adenoma and early stage colon cancer. Gastrointest Endosc Mar;61(3):
d. All of the above

21. Nodular Hyperplasia
74 y/o man with metastatic disease to neck from unknown primary, now NED after chemoXRT

22. Infection
68 year old man with solitary lung nodule. Biopsy: aspergillosis 3

23. Granulomatous Disease
62 year old man with hilar and mediastinal adenopathy. Biopsy: sarcoidosis

24. Miscellaneous Causes
Thyroiditis

25. Miscellaneous Causes
Rib Fracture

26. Problems with CT Attenuation and scatter Beam hardening
Volume averaging

27. Beam Hardening
Gollub et al. J Nucl Med 2007;48:

28. Beam Hardening

29. Volume Averaging
Gollub et al. J Nucl Med 2007;48:

30. Problems with PET/CT Patient movement Respiratory misregistration
Attenuation correction

31. Patient Movement
• Head movement
Secure head, or use head holder

32. Respiratory Misregistration
variation
Partial expiration best:
“Breathe in, exhale, don’t breathe”
from Ben Yeh MD, UCSF

33. Respiratory Misregistration
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:

34. Question 2 Respiratory misregistration in PET/CT is minimized when
CT is performed in end inspiration
b. CT is performed in mid expiration
c. CT is performed in end expiration
d. CT is performed during quiet breathing

35. Question 2 The correct answer is b. CT is performed in mid expiration
Sureshbabu W, Mawlawi O. PET/CT Imaging Artifacts. J Nucl Med Technol 2005;33:

36. Attenuation Correction
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:

37. Attenuation Correction
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:

38. Summary
• False negative FDG PET can be reduced by careful patient selection for appropriateness and proper preparation
• False positive FDG PET can be reduced by correlation with CT and knowledge of potential pitfalls

39. Summary • CT artifacts can be avoided by optimizing technique
• PET/CT artifacts can be reduced by proper patient preparation and instructions

40. 3