Pulmonary NM

Question 1

Perfusion radiotracer

Answer 1

Tc-99m - MAA.

Question 2

Relative contraindication to MAA

Answer 2

Severe pulmonary hypertension (may exacerbate symptoms by occluding a few pulmonary capillaries).

Question 3

Findings of right to left shunt during pulmonary NM perfusion scan

Answer 3

Radiotracer activity in the kidneys and brain.

Question 4

Differentiate between Right –> L shunt and Free Technetium

Answer 4

R–>L shunt will show uptake in brain and kidneys

Free Tech will show activity in thyroid and none in brain.

Question 5

Why is Xe-133 imaged posteriorly?

Answer 5

Decreased artifacts from soft tissue anteriorly (breasts).

Question 6

Which two radiotracers are used in ventilation portion of V/Q scan? Advantages of each?

Answer 6

Xenon-133 and Tc-99m DTPA
Xe-133: requires patient cooperation but allows for dynamic imaging.
Tc-99m: no dynamic imaging but easier to use overall.

Question 7

Dose adjustment of Tc-99m-MAA in pregnancy?

Answer 7

Decrease the dose by 1/2.