Can CT Perfusion Evaluate Cerebral Hemodynamic Changein Chronic Occlusive Cerebrovascular Diseases?

- Comparison with Diamox-enhanced SPECT -

M. Hirata MD , Y. Sugawara MD , K. Kikuchi MD , H. Miki MD , T. Mochizuki MD , K. Murase PhD , S. Yamauchi RN

INTRODUCTIONCerebral perfusion parameters such as cerebral blood flow

(CBF), cerebral blood volume (CBV), and mean transit time (MTT) are important for the determination of medical treatment plan and/or prognostic prediction of patients with cerebrovascular diseases (CVDs) (1, 2). Although the utilities of CT perfusion in acute stroke have been reported by many investigators (3-6), the role of quantitative CT perfusion parameters in patients with chronic occlusive CVD has not been elucidated enough (7) .

Prior studies from our group and others have shown that CBF and cerebral perfusion reserve (CPR) measurements using Diamox enhancement and SPECT are useful to evaluate hemodynamic status in chronic occlusive CVDs (8, 9).

In this exhibit, we will present the quantitative results of CT perfusion parameters in chronic occlusive CVDs and compare these with the data of Diamox-SPECT. Finally, we will discuss about the advantages and limitations in each of perfusion imaging modalities.

Learning Objectives:

1. Describe the comparative results for quantitative values of CBF, CBV and MTT measured by CT perfusion in comparison with Diamox-enhanced SPECT.

2. Clarify the utilities and limitations in CT perfusion parameters in management of patients with chronic occlusive cerebrovascular diseases.

BACKGROUNDXe-133 SPECT in patients with chronic CVDs

Significantly increased immediately after treatment. Therapeutic effects continue on follow-up

Increased little immediately after PTA and stenting. No significant changes on follow-up

Cerebral Perfusion Reserve

PTA and/or stenting

Cerebral Blood Flow

We previously reported that cerebral perfusion reserve (CPR) significantly increased, but cerebral blood flow increased little immediately after PTA and /or stenting. Therefore, measurement of CPR is useful for evaluating therapeutic effects and for follow-up after PTA and stenting.

Sugawara, et al. (SNM 2000) Hirata , et al. (SNM 2003)

BACKGROUND

• The MTT values in the territories of severely decreased CPR were significantly higher than those in the territories of moderately decreased or normal CPR

• Severe CPR impairment can be estimated with MTT (8).

MR perfusion in patients with chronic CVDs

Perfusion reserve

Severely decreased CPR ≦ 0%

Moderately decreased

0% < CPR ≦ 15%

Normal CPR > 15 %

CBF

CBV

MTT

CBF

CBV

MTT

REST

DIAMOX

42(27%)

Post PTA

MR Perfusion

133Xe-SPECT CT Perfusion

30

1.6

5.4

32

1.6

5.1

29

BACKGROUND

MR Perfusion

CBF

CBV

MTT

REST

DIAMOX

23(-13%)

133Xe-SPECT

Pre PTA

26 Decrease of CPR

Increase of MTT

Improvement of CPR

Normalization of MTT

An example case: 73/M, PTA for Lt. MCA stenosis

Can CT Perfusion Evaluate Cerebral Hemodynamic Changein Chronic Occlusive Cerebrovascular Diseases?

CT perfusion

Mean Transit Time(MTT)

Cerebral Blood Volume(CBV)

Cerebral Blood Flow(CBF)

Diamox-enhanced 133Xe SPECT

Cerebral Perfusion Reserve (CPR)?

relation

Comparison of CBF, CBV and MTT measured by CT perfusion with CPR measured by Diamox-enhanced SPECT

METHODS• CT perfusion protocol

– CT Scanner: Light Speed QX/i (GE) or Ultra (GE)– Dynamic Scan:

• Contrast medium: 300 mgI/ml, total 30-40 ml• 3-4 ml/s with power injector• Cine mode (5mm x 4i, 1 sec/rot) • 5 sec delay for 60 sec

– Data Analysis: Advantage Workstation 4.2 with CT perfusion 3• Xe-133 SPECT protocol

– Xe-133 gas (1850 MBq) inhalation (Kanno-Lassen method)– Dynamic SPECT (20 s/scan x 16, Hitachi SPECT 2000H-40)– At rest and after Diamox® (1g)

• SUBJECTS– 6 male patients with chronic occlusive CVDs

(Mean age = 63.3 ± 9.3 years)Rt. MCA stenosis: 2

Lt. MCA stenosis: 2

Rt.ICA and MCA stenosis with Lt. ICA occlusion: 1

Rt.ICA occlusion : 1

METHODS

MTT

CBV

CBF

CT perfusion

CPR = ×100 (%)CBF(Diamox) - CBF(Rest)

CBF(Rest)

133Xe-SPECT

Mean value inMCA territory

Mean CPR inMCA territory

• Regions of interest were placed in the MCA territories. The values of CBF, CBV and MTT measured by CT perfusion were compared with CPR values obtained from Diamox-enhanced 133Xe-SPECT.

Results -Relation between CPR and CTP parameters-

• Positive correlation was found between CBF and CPR.

• Negative correlation was found between CBV and CPR.

• Negative correlation was found between MTT and CPR.

• The strongest correlation was found in MTT

0

10

20

30

40

50

- 20% 0% 20% 40% 60%CPR

CBF(mL/100g/min)

r = 0.58 CPR

CBV(mL/100 g)

r = -0.34

02468

1012

- 20% 0% 20% 40% 60%CPR

MTT(sec)

r = -0.63

-20 0 20 40 60 (%) -20 0 20 40 60 (%)

-20 0 20 40 60 (%)

• Positive correlation was found between CBF and CPR.

• Negative correlation was found between CBV and CPR.

• Negative correlation was found between MTT and CPR.

• The strongest correlation was found in MTT

REST

DIAMOX

CBF

CBV

MTT

CT Perfusion

41

52(27%)

29

1.7

5.5

19

2.0

10.4

133Xe-SPECT

133Xe-SPECT

REST

DIAMOX

36

32 (-10%)

Case 1: 57/M, Rt. MCA Occlusion

No abnormal findings

CBF ↓CPR ↓

CBF ↓CBV ↑MTT ↑ ↑

Summary 1

• Every CT perfusion parameters correlate with CPR.

• MTT is the most sensitive to reflect severely decreased CPR in chronic occlusive CVDs.

What is the limitation in CT perfusion in management of patients with chronic occlusive cerebrovascular diseases?

Assessment of the therapeutic effects -

Two example cases

CASE 1• STA-MCA anastomasis for Rt. ICA occlusion

CASE 2• CEA for Rt. ICA Stenosis

CASE.1 66/M, STA-MCA anastomasis for Rt. ICA occlusion

REST

Pre STA-MCA

DIAMOX

CBF

CBV

MTT

CT Perfusion

30(0%)

30 35

44(26%)

35

2.9

4.66.2

3.4

27

133Xe-SPECT

REST

Post STA-MCA

DIAMOX

CBF

CBV

MTT

CT Perfusion

39

2.2

4.9

30

3.2

6.8

28

29(4%)

36

39 (6%)

133Xe-SPECT

On CT perfusion•CBF values were decreased.•CBV and MTT values were increased.

On 133Xe-SPECT•CBF and CPR were decreased in Rt. MCA territory.

On 133Xe-SPECT and CT perfusion•No remarkable change was found.

NormalDecrease of Perfusion ReserveMisery PerfusionInfarction

CBF

CBV

MTT

OEF

CMRO2

CASE.1

133Xe-SPECT CT Perfusion

CBF↓ CBF↓

CPR↓ CBV↑

MTT↑

On 133Xe-SPECT, both CBF and CPR were decreased in Rt. MCA territory. This area could be categorized to "misery perfusion" in which CBF is reduced and the oxygen extraction fraction (OEF) is increased to maintain the cerebral metabolic rate of oxygen (CMRO2) (10) .

CT perfusion represented decrease of CBF and increase of CBV and MTT.

On 133Xe-SPECT•CPR increased after treatment. •No remarkable change was found on CBF.

On CT perfusion•No remarkable change was found

on CBF, CBV and MTT.

On 133Xe-SPECT•CPR was decreased in the Rt. MCA territory. •CBF was not decreased.

CASE.2

51(18%)

43(2%)

57(29%)

61 (37%)

CBF

CBV

MTT

CBF

CBV

MTT

Pre CEA Post CEA

REST REST

DIAMOX DIAMOX

45454442

40

2.1

4.7

40

2.1

48

2.3

3.9

43

2.1

4.1

68/M, CEA for Rt. ICA Stenosis

CT Perfusion CT Perfusion133Xe-SPECT 133Xe-SPECT

On CT perfusion•CBF, CBV and MTT were normal.

4.6

NormalDecrease of Perfusion ReserveMisery PerfusionInfarction

CBF

CBV

MTT

OEF

CMRO2

CASE.2

133Xe-SPECT CT Perfusion

CBF → CBF →

CPR ↓ CBV →

MTT →

On 133Xe-SPECT, only CPR was decreased in Rt. MCA territory. In this case, CBF , OEF and CMRO2 were maintained by autoregulatory

vasodilatation (i.e. increase of CBV) (10) .However, all CT perfusion parameters were

normal. This suggest that CT perfusion potentially has limitation in the detection of mild hemodynamic changes.

Summary 2

• Severe ischemic change is detectable by CT perfusion

• CT perfusion potentially has limitation in the detection of mild ischemic changes.

Conclusion

• MTT is the most sensitive to reflect severely decreased CPR in chronic occlusive CVDs.

• CT perfusion potentially has limitation in the detection of mild ischemic changes.

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