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Core > Nuclear: PET for Cancer > Flashcards

Nuclear: PET for Cancer Flashcards

1
Q

How is 18-FDG produced?

A

Cyclotron

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2
Q

What is the cause of FDG uptake at the arrow?

A

Attenuation correction artifact from a respiratory motion artifact

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3
Q

What is the difference between B and C?

A

C is the non-attenuation correction image (reduced attenuation correction artifact from a metal breast implant port)

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4
Q

How can you tell whether apparent FDG uptake near a cardiac pacemaker is due to attenuation correction artifact?

A

Look at the non-attenuation corrected images

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5
Q

What is the critical organ for 18-FDG?

A

Bladder

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6
Q

How does FDG enter cells?

A

GLUT1 transporter

Note: Once inside, it is phosphorylated by hexokinase which traps it in the cell.

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7
Q

How long should you wait after treatment to repeat a FDG PET?

A

Chemotherapy: Wait 2-3 weeks

Radiation: Wait 8-12 weeks

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8
Q

How do you calculate SUV?

A

FDG concentration at time T/(fdg dose/body weight)

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9
Q

What is the limit of resolution for FDG PET?

A

Lesions less than 1 cm are generally too small for PET

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10
Q

What is considered an abnormal SUV?

A

In general, people say that an SUV > 2.0 is usually abnormal (cancer or infection/inflammation)

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11
Q

How do blood glucose levels affect FDG PET?

A

Higher blood glucose levels artificially lower SUVs

Note: This is why serum glucose is tested and should be less than 150-200 prior to the study.

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12
Q

What happened?

A

Insulin was given to the pt before the FDG PET

Note: Insulin will drive the radiotracer (and other glucose) into muscles.

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13
Q

When is thymus uptake of FDG normal?

A
  • Young pts (<13 y/o)
  • After chemotherapy (i.e. thymus rebound)
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14
Q
A

Brown fat (classic distribution in the neck/supraclavicular region and upper abdomen)

Note: This is more often seen in younger pts and pts who were cold during the uptake period.

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15
Q

How can you reduce FDG uptake in brown fat?

A
  • Keep the waiting room warm
  • Give medications (e.g. propranolol or reserpine)
  • Diet (have a high fat and very low carb diet the night before and morning of the study)
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16
Q
A

Hibernoma (benign brown fat tumor)

Note: These are often taken out because they can’t easily be distinguished from liposarcoma.

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17
Q

How does obesity affect FDG PET?

A

Obesity causes artificially increased SUV values (fat takes up less glucose than muscle)

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18
Q

Ki67

A

An antigen associated with cellular proliferation (more Ki67 = more aggressive tumor)

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19
Q

How should you alter FDG PET protocol when the pt has breast cancer?

A
  • Make sure the FDG is injected on the side opposite the breast cancer
  • Scan with arms up
20
Q

When might FDG PET be used during screening for breast cancer?

A

If the pt needs an MRI for problem solving, but has a contraindication (e.g. metal in eyes)

21
Q

What cancers are classically cold on FGD PET?

A
  • Bronchoalveolar carcinoma
  • Carcinoid/neuroendocrine (if low/intermediate grade)
  • Renal cell carcinoma
  • Hepatocellular carcinoma
  • Peritoneal/bowel/liver implants
  • Prostate cancer
  • Any mucinous cancers
22
Q

Focal FDG uptake in thyroid…

A

Get thyroid ultrasound (could be cancer or nothing)

23
Q

Diffuse thyroid uptake…

A

Most often autoimmune Hashimoto thyroiditis

Note: Can be normal in young pts or pts after chemotherapy.

24
Q

Which type of renal mass is classically FDG hot?

A

Oncocytoma

25
Q

Ground glass pulmonary nodule without FDG uptake…

A

Think cancer (or too small if less than 1 cm)

Note: If FDG hot, think infection.

26
Q

How does hepatocellular carcinoma appear on FDG PET?

A

Cold (60% of the time)

Note: Variability depending on the functional status of glucose-6-phosphatase (if not functional, the HCC can’t trap FDG in the cells).

27
Q

Are testicular cancers FDG hot?

A

Seminomatous cancers are usually hot

Non-seminomatous cancers are usually cold (or mildly warm)

28
Q

FDG-avid ovaries

A

Suspicious in a postmenopausal pt, recommend a pelvic ultrasound

Note: If younger, correlate with menstrual cycle.

29
Q
A

Metformin use (intense FDG uptake in colon)

30
Q

How long before an FDG PET should you stop metformin?

A

2 days prior

31
Q

Focal FDG uptake in colon…

A

Recommend colonoscopy

32
Q

FDG PET

A

Pituitary mass (adenoma vs carcinoma), recommend hormonal workup and MRI brain

33
Q

Is FDG uptake in the adrenal glands?

A
  • Mild uptake is normal
  • Uptake greater than liver is abnormal, recommend adrenal mass CT (could be a simple adenoma)

Note: Be more cautious is the pt has lung cancer (which often metastasizes to the adrenals).

34
Q

Is FDG uptake in the right ventricle normal?

A

No, usually means the right ventricle is enlarged

35
Q

Is lymphadenopathy in sarcoidosis FDG hot?

A

Yes, which can help direct biopsy target

36
Q

How can you differentiate thymus rebound from recurrent lymphoma in the anterior mediastinum?

A

If it is FDG HOT, then it is lymphoma (thymus rebound will only be warm on PET)

Note: Thymus rebound also usually maintains the same thymus contour, draping over the heart (lymphoma will be round and mass-like).

37
Q

Almost all lymphomas are very FDG hot. Which type of lymphoma has low FDG avidity?

A

Extranodal marginal zone lymphomas (including mucosa-associated lymphoid tissue/MALT)

38
Q

If FDG uptake in the endometrium normal?

A

Yes, but only during menstruation (~days 0-4) and ovulation (~day 14) AND only if diffuse uptake

Note: Endometrial uptake in a postmenopausal pt is always suspicious. Focal uptake is always suspicious.

39
Q
A

Corpus luteal cyst

40
Q

Why is it important to recognize existence of a vesicovaginal fistula on FDG PET?

A

Spillage of urine into the vagina will cause very high SUVs, which can be mistaken for tumor

41
Q

What should you do to look for perivesical disease on an FDG PET?

A

Look at non-attenuation corrected images (anything near the bladder will be drowned out on the attenuation corrected images)

42
Q

Which has the worse prognosis: primary or secondary osteosarcomas?

A

Secondary osteosarcomas (e.g. Pagets, Radiation, multiple chondromas, etc.) have a much worse prognosis

43
Q

Where does osteosarcoma tend to metastasize to?

A
  • Other bones
  • Lung
44
Q

Do SUVs correlate with osteosarcoma tumor grade?

A

Yes, higher SUVs typically mean higher grade cancers

Note: Baseline SUV is also an independent and significant predictor of overall survival.

45
Q

What are some benign bone masses that often appear hot on FDG PET?

A
  • Giant cell tumors
  • Fibrous dysplasia
  • Osteomyelitis
46
Q

What is the most important prognostic factor for osteosarcoma?

A

FDG PET response to neoadjuvant chemotherapy

47
Q
A

Rheumatoid arthritis

Note: Symmetric, periarticular FDG uptake.

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