PET CT

Question 1

What is the physics of PET

Answer 1

Positron antimatter electron, identical in mass but has an opposite charge of +1. 18F too many protons. Emits positron. Left with 18 ) positron encounters an electron and completely annihilates. 511Kev at 190 degrees coincidence detection. image creation.

Question 2

What is the low dose CT for?

Answer 2

Attenuation correction and lesion localization.

Question 3

What is the dose of the low dose CT

Answer 3

1-3mSv

Question 4

What is the physiology of FDG?

Answer 4

FDG is a Glucose analog. Gets taken up by cell via GLute transportter. Glut transporter is upregulated in most cancers. FDG half-life is 110 minutes.

Question 5

What is the preparation for PET?

Answer 5

Fasting for 6hours, blood sugar <10mmol/L. Metformin increases uptake in the bowel. Rest. Void prior to the scan. To reduce urinary bladder activity. Oral propranolol 10mg prior. avoid exercise/strenuous activity.

Question 6

What normally /physiologically uptakes FDG

Answer 6

Brain, breast, oropharyngeal, myocardial, Bowel, GU (renal excretion) Endometrial, Ovarian. Liver/spleen

Question 7

What are some common causes of false negatives

Answer 7

Tumor histology: Cystic/mucinous ovarian cancer or low-grade tumors. Lesions small Than 8mm. Negative lymph nodes: low tumor volume or necrotic. Diabetes/non-fasting patients (decreases sensitivity). F

Question 8

False positives

Answer 8

Normal physiological uptake. Granulomas and other infections. Postoperative post-treatment inflammation.

Question 9

What is SUV max?

Answer 9

Activity concentration in tissue divided by injected activity/body size. Many variables: patient weight, body size, blood glucose level, post-injection uptake time. respiratory motion, lesion size, technical scanner type.

Question 10

What is mild, mod, intense

Answer 10

Mild 2.5-5. Mod 5-7, intense >7. (loose interpretation)

Question 11

Is endometrial uptake normal or abnormal

Answer 11

Normal during mensturation. Abnormal in post menopausal patients.

Question 12

What can happen to the thymus post chemo?

Answer 12

Rebound thymic hyperplasia

Question 13

what percent of incidental thyroid nodules are malignant?

Answer 13

30%.

Question 14

What are the common parotid gland incientalomas

Answer 14

warthins, pleomorphic adenomas, .

Question 15

what is a warthins?

Answer 15

More common in somkers, commonly adrenals

Question 16

is PET useful in ovarian CA.

Answer 16

Limited use in initiail staging. ofovarian apthology. much overlap tween benign and malignant ovarian lesiosn. Pet is useful following intiital therapy or prior to surgical staging and cytoreduction.