Perfusion

Question 1

Why perform perfusion imaging?

Answer 1

1) Demonstrate disease-related changes before they manifest in anatomical imaging e.g. demonstrate poor perfusion following stroke, before this is apparent on anatomical imaging.
2) Added value on structural imaging e.g. tumours well perfused.

Question 2

What is DSC CE MRI and how is it used to quantify perfusion?

Answer 2

CA reduces T2*
GRE with EPI read-out
Observe S(t)

S(t) -> C(t) -> I(t) -> rCBV -> CBF

Question 3

What are the assumptions of indicator dilution theory?

Answer 3

Assumptions
1) Indicator does not perturb sys. and represents fluid it is in
2) No changes in flow or vascular volume
3) Mass cons. (no indicator pooling / BBB leakage)
4) No recirculation

Eqns
1) rCBV = time integral of c
2) CBF = CBV/MTT

Question 4

How is perfusion quantified in DCE MRI?

Answer 4

T1w time series
injection, uptake, washout
Qualitative or quantitative analysis
e.g. 2 compartment model
S(t)-> C(t) -> I(t) -> Ktrans, ve

Question 5

DSC equation to convert signal to concentration?

Answer 5

C propto DeltaR2*

Question 6

DCE equation to convert signal to concentration?

Answer 6

R1=R1_0 + r1.C

=> C = DeltaR1/r1

Question 7

Typical duration and time resolution for brain perfusion scan?

Answer 7

Duration 2 mins
Time resolution 1 - 2 s (EPI)

Question 8

Typical duration and time resolution for a breast perfusion scan?

Answer 8

10 min study
15 s time resolution