The updated link for the Introductory PET CT lecture (Part 1) is now available; additional parts will be uploaded soon.

1. PET CT Beginners Guide
Miad Alsulami.MD.FRCPC
PART : I

2. Outlines
• Normal distribution of FDG .
• Pitfalls and Technical issues in FDG PET CT.
• Most common Oncological applications of FDG PET CT ( part I).
• Surviving as junior physician in PET CT Department .

3. Normal Distributionof FDG
• The normal distribution of F-18 FDG reflects glucose metabolism.
• The brain is an obligate glucose user, so uptake is high.
• The kidneys, ureters, and bladder also show intense activity from
urinary clearance of F-18 FDG.
• Moderate and sometimes heterogeneous activity is seen in the liver.
• Variable activity occurs in the heart, gastrointestinal tract, salivary
glands, and testes.

4. • The uterus may show endometrial uptake depending on the
menstrual cycle stage.
• Low-level activity is normal in the bone marrow.

5. Normal distribution and normal variants

6. Pitfallsand Technicalissues in FDG PET CT.

8. Muscle activity from increased
insulin levels
Paralyzed vocal cord artifact on
PET

9. Vascular Activity
• Focal F-18 FDG accumulation may localize to vessels, particularly in
the aortic arch.
• Can be associated with calcifications from atherosclerotic disease.
• This pattern of uptake is totally different from vasculitis and mycotic
aneurysm ( will be discussed in future LinkedIn posts ).

10. Thyroid Activity
• Diffusely increased uptake may be seen in thyroiditis, goiter, and
Graves disease.
• Normally the thyroid should not take up the FDG .
• Focal thyroid uptake should always be flagged as it carries a risk of
thyroid cancer ( percentage ?).

12. Brown fat
• Caused by cold weather.
• Can be seen in young, thin patients .
• Brown fat contains adrenergic receptors that contribute to uptake in
anxious patients.
• it can decrease sensitivity for tumor detection ( head and neck
cancers /Lymphoma )… always look at the CT part for confirmation .

13. Brown fat uptake versus adenopathy?
Look at the CT part

14. How to suppressbrownfat activity ?
• Valium.
• Warming patients for 30 to 60 minutes before injection.
• Beta blockers .

15. Infection /inflammation

16. Pleurodesis vs mesothelioma

17. Bone marrow stimulation Thymic rebound

18. Artifacts will not be included in this lecture as it has been extensively
discussedin previous lectures /posts .

19. Most common Oncological applicationsof FDG
PET CT ( PART 1)

20. Lymphoma
• Malignant lymphoma is classified as either Hodgkin disease or the
more common non-Hodgkin lymphoma .
• Hodgkin disease tends to spread in an orderly fashion in contiguous
lymph node chains.
• Non-Hodgkin lymphoma is often widespread at the time of diagnosis.
• PET CT has a major role in staging and therapy assessment of FDG
avid lymphoma .
• Will be discussed further in dedicated lectures .
• Updates are available on LinkedIn .

21. Melanoma
• The thickness of the primary lesion is the most important prognostic
factor, and this is graded according to the Breslow classification.
• Prognosis is extremely poor, with nodal or distant metastases.
• Metastatic disease may occur in unusual locations, such as other
cutaneous and subcutaneous sites, spleen, distant nodes, liver, and
gallbladder.
• Always FDG avid.
• CT is more sensitive than PET in detecting small parenchymal lung
lesions and MRI best identifies brain metastases.

22. FDG PET in melanoma.

23. Head and Neck Carcinoma
• PET CT has a role in staging and therapy response .
• The prognosis depends on the disease stage.
• Conventional modalities are better in assessing tumor size.
• PET can identify the unknown primary tumor in 20% to 50% of
patients.

24. Thyroid Carcinoma
• Differentiated tumors accumulate iodine-131 and are best evaluated
and treated with radioactive iodine.
• Has a role in poorly differentiated thyroid cancers and recurrent
thyroid cancers with negative iodine scan .
• PET may help direct surgical resection or external beam radiation
therapy.

25. Lung Carcinoma
• The histological classification of lung cancer is NSCLC and SCLC.
• 75% of SCLC cases are initially diagnosed with disseminated disease.
• NSCLC is often respectable.
• Early diagnosis and proper staging are critical to therapeutic planning
in NSCLC.
• PET CT has a major role in staging and therapy assessment .

26. SPN
• F-18 FDG PET has proved to be an accurate method to differentiate
benign from malignant nodules and decrease biopsy of benign lesions.
• Malignant nodules generally have increased F-18 FDG uptake.
• FDG PET scans can change the surgical approach for nodules
demonstrating increased uptake by identification of mediastinal
lymph nodes with abnormal uptake and distant metastases.
• False negative results can be seen in lesions smaller than 1 cm.
• False negative PET results can occur in certain tumors such as
adenocarcinoma and carcinoid.

27. False positive and False negative lesions
• False positive:
1. Inflammatory process.
2. Infection (TB, histoplasmosis, aspergillosis,inflammatory pseudo-
tumor).
• False negative:
1. Well differentiated adenocarcinoma.
2. Carcinoid.
3. Small lesion.
4. Mucin secreting metastasis

28. Breast Carcinoma
• Breast cancer is classified to ductal or lobular , invasive and non
invasive (carcinoma in situ).
• Primary assessment depends on the size ,type of breast caner and
molecular subtypes.
• Detection of lobular carcinoma and ductal carcinoma in situ being
much more limited than in invasive ductal carcinoma.
• P.S: please revise the dedicatedteaching posts on LinkedIn .

29. Gastrointestinal Tumors

30. Esophageal Carcinoma
• Most commonly due to squamous cell cancer in the upper two thirds
of the esophagus , adenocarcinoma occurs in the lower third.
• FDG PET has been used in cases of equivocal biopsy or to assess
patients with biopsy-confirmed tumor.
• Has a major role in staging and therapy assessment .

31. Colorectal Carcinoma
• Both adenoma and carcinoma may appear with increased FDG
uptake.
• Hemorrhoids can have increased uptake secondary to inflammation.
• Nodular uptake is often due to focal lesion.
• Segmental uptake is often secondary to inflammation.
• Diffuse uptake can be normal especially in right colon .

32. Colorectal Carcinoma
• Preoperative staging with PET CT is not indicated.
• The role of PET CT mainly reserved in patients with high CEA level
with normal conventional imaging ( recurrence ).
• PET CT has a role in rectal cancer if neoadjuvant chemoradiation is
considered as it may upstage these patients and detect distant
metastasis /Synchronous disease.
• Differentiating post radiation changes from residual / recurrent
disease .

33. GIST
• It can show high FDG activity .
• PET more accurately assesses early response than CT and predicts
improved patient survival.

35. Prostate Cancer

36. Prostate Cancer
• FDG PET has very limited sensitivity for prostate cancer.
• Focal prostate activity should be always flagged for further
evaluation.
• FDG has a role in patients with biochemical recurrence with negative
PSMA scans .
• It is a must in some centers before radioligand therapy .

37. Musculoskeletal Tumors

38. • Benign tumors (giant cell tumor, fibrous dysplasia, and eosinophilic
granulomas) have been shown to accumulate FDG.
• FDG PET CT has a role in staging and therapy assessment for patients
with high grade sarcomas.
• Not sensitive in assessing lung metastasis and patients should have CT
thorax .

39. Survivingas junior physician in PET CT
Department

40. Survivingas junior physician in PET CT
department
❖Checking :
• recognize altered biodistribution , Identify the causes , rescadule the
study if it significant, sit with patients and educate them to avoid
future recurrence .
• Look for significant motion artifact .
• Any need for extra images ( dedicated abdomen , head and neck , etc)
• Any urgent findings that we need to act on ? Very important !

41. ❖Reporting :
• Gather the clinical data before start dictating your case .
• Always be systematic .
• Start with head neck , reduce your intensity , identify your blind spots
( for me pituitary fossa ).
• Then move to chest , check each region , always examine the lung
carefully as many of the metastatic pulmonary nodules are small to
be metabolically resolved by PET CT ( partial volume effect ). Please
be extra carful in patients who don’t have recent CT chest .

42. • Examine the abdomen very carefully.
• Focal colonic activity can be challenging , obtain delayed images if you
are not sure and see if the activity moves ( benign) , fixed ( requires
further evaluation with colonoscopy ).
• When you are assessing the urinary bladder and prostate make sure
that you reduce and adjust the intensity .
• In case of beam hardening artifact , make sure you examine the
region on non attenuated corrected images.
• Examine the osseous skeleton on all planes( coronal most important
for the spine to check for fractures)

43. • Bone marrow is better to be assessed on MIP images .
• Diffuses bone marrow activity in most of the cases are reassuring (
Should be homogenous), it can differ from case to another .
• Focal bone marrow activity should be contextualized .
• Before finalizing you report make sure that you reexamine the MIP
images again .

44. Interesting cases ( Part I)

45. 76 years old male withmetastatic RCC forPET CT
Surveillance.

48. Teaching points :
1. FDG PET imaging can be valuable in differentiating between
malignant and benign gallbladder lesions by analyzing the intensity
and pattern of radiotracer uptake.
2. If acute cholecystitis is detected on FDG PET, it will present as a
ring-like radiotracer uptake.
3. In such cases, it is recommended to flag the finding and pursue
further evaluation using ultrasound (US).

49. 28 years old femalewith colon cancerin remission
For PET CT surveillance .

51. Teaching points:
• Large PE can be detected Incidentally on PET scans.
• They are usually hypometabolic ( lower activity than the background).
• PET used to Differentiate pulmonary artery sarcoma from chronic PE ,
Pulmonary artery sarcoma usually demonstrates increased FDG
uptake .

52. 53-year-oldfemalewitha historyof
chondrosarcomaforPET CT surveillance.

55. Teaching points :
• Facial fillers using various dermal and sub-dermal injectable
compounds .
• These procedures can sometimes cause focal inflammation, fat
necrosis, and calcifications.
• it is important for us to be familiar with the radiographic appearance
of such cosmetic procedures to avoid misinterpretation of the
findings .

56. •To be Continued …..