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Nuclear: PET for Cancer Flashcards

(47 cards)

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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?

Study These Flashcards
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?

Study These Flashcards
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?

Study These Flashcards
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…

Study These Flashcards
A

Get thyroid ultrasound (could be cancer or nothing)

23
Q

Diffuse thyroid uptake…

Study These Flashcards
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?

25
Ground glass pulmonary nodule without FDG uptake...
Think cancer (or too small if less than 1 cm) Note: If FDG hot, think infection.
26
How does hepatocellular carcinoma appear on FDG PET?
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
Are testicular cancers FDG hot?
Seminomatous cancers are usually hot Non-seminomatous cancers are usually cold (or mildly warm)
28
FDG-avid ovaries
Suspicious in a postmenopausal pt, recommend a pelvic ultrasound Note: If younger, correlate with menstrual cycle.
29
Metformin use (intense FDG uptake in colon)
30
How long before an FDG PET should you stop metformin?
2 days prior
31
Focal FDG uptake in colon...
Recommend colonoscopy
32
FDG PET
Pituitary mass (adenoma vs carcinoma), recommend hormonal workup and MRI brain
33
Is FDG uptake in the adrenal glands?
- 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
Is FDG uptake in the right ventricle normal?
No, usually means the right ventricle is enlarged
35
Is lymphadenopathy in sarcoidosis FDG hot?
Yes, which can help direct biopsy target
36
How can you differentiate thymus rebound from recurrent lymphoma in the anterior mediastinum?
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
Almost all lymphomas are very FDG hot. Which type of lymphoma has low FDG avidity?
Extranodal marginal zone lymphomas (including mucosa-associated lymphoid tissue/MALT)
38
If FDG uptake in the endometrium normal?
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
Corpus luteal cyst
40
Why is it important to recognize existence of a vesicovaginal fistula on FDG PET?
Spillage of urine into the vagina will cause very high SUVs, which can be mistaken for tumor
41
What should you do to look for perivesical disease on an FDG PET?
Look at non-attenuation corrected images (anything near the bladder will be drowned out on the attenuation corrected images)
42
Which has the worse prognosis: primary or secondary osteosarcomas?
Secondary osteosarcomas (e.g. Pagets, Radiation, multiple chondromas, etc.) have a much worse prognosis
43
Where does osteosarcoma tend to metastasize to?
- Other bones - Lung
44
Do SUVs correlate with osteosarcoma tumor grade?
Yes, higher SUVs typically mean higher grade cancers Note: Baseline SUV is also an independent and significant predictor of overall survival.
45
What are some benign bone masses that often appear hot on FDG PET?
- Giant cell tumors - Fibrous dysplasia - Osteomyelitis
46
What is the most important prognostic factor for osteosarcoma?
FDG PET response to neoadjuvant chemotherapy
47
Rheumatoid arthritis Note: Symmetric, periarticular FDG uptake.

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