Dr sridhar role of CT and CT perfusion in evaluation of stro

Goals of Acute Stroke • Perfusion : Assess cerebral blood volume, cerebral blood flow, and mean transit time • Penumbra : Assess tissue at risk of dying if ischemia continues without re

Role of CT in Acute Stroke

Dr PG Sridhar

Sr Consultant

• Estimated stroke related death

1.2 % of the total deaths**Neurology Asia 2006; 11 : 1 – 4 **Neuroepidemiology 2004;23:261–268

“Time is Brain”

National Institute of

Neurological Diseases and

Stroke trial (NINDS)

(N Engl J Med 1995;333:1581-7.)

3Hrs

European Cooperative Acute

Stroke Study III (ECASS III)

(Stroke 2009;40:2262-2263 )

4.5 Hrs

Goals of Acute Stroke

• Perfusion : Assess cerebral blood volume, cerebral

blood flow, and mean transit time

• Penumbra : Assess tissue at risk of dying if ischemia continues without recanalization of

intravascular thrombus

Rowley HA AJNR 2001;22:599–601.

Unenhanced CT

• R/o hemorrhage

• Insular ribbon sign

• obscuration of the lentiform

nucleus

• Cerebral swelling

• Dense vessel sign (MCA or MCA dot sign)

Intracranial Hemorrhage

obscuration of the lentiform

nucleus

May be seen on CT images within 2 hours after the onset of a Stroke

Insular Ribbon Sign

73Y/F, 2 1⁄2 hours after the onset of left hemiparesis

66Y/M, Left hemiparesis

history of a visit to a chiropractitioner

Stroke Window

Follow Up

24 Hrs 1 Week

Stroke window

Std soft tissue window windowStroke

width

centre

80 20

8 32 Sensitiv

small attenuation difference

between normal and acutely

edematous brain tissue can be

accentuated by using variable,

nonstandard window width and

center level settings

Lev et al Radiology 1999; 213: 150-155

Alberta Stroke Program Early CT

Score(ASPECTS)

Dense Basilar and PCA

85Y/F, Change in mental status

41Y/F, right sided

weakness

4 Day F/UP MRI & MRA

False Positive Dense

CT PERFUSION

CT PERFUSION

• Cerebral blood volume (CBV): the

volume of blood per unit of brain tissue

• Cerebral blood flow (CBF): the volume

of blood flow per unit of brain tissue per minute

• Mean transit time (MTT): defined as the time difference between the arterial

inflow and venous outflow

• Time to peak (TTP): The time from the beginning of contrast material injection

to the maximum concentration of

contrast material within a region of

interest

• Dynamic contrast material–

enhanced perfusion imaging (First pass technique)

• Perfused-blood-volume mapping

Steps in CT Perfusion Data Postprocessing

• Freehand or automated

placement of an ROI over an

input artery to obtain the

arterial time-attenuation curve

or arterial input function

• Freehand or automated

placement of an ROI over an

input vein to obtain the venous

time-attenuation curve

• Generation of the arterial and

venous time-attenuation

curves

Perfusion Parameters

• MTT- Deconvolution of arterial and tissue enhancement curve

• CBV- calculated as the area under the curve in a

parenchymal pixel divided

by the area under the curve in

an arterial pixel

• CBF- using the central volume equation:

CBF= CBV/MTT

•Since the input artery is usually smaller than the input vein,

the venous ROI serves to correct for volume averaging in the arterial ROI

NORMAL DIFFERENCES IN PERFUSION PARAMETERS BETWEEN GRAY AND WHITE

CT PERFUSION

Wintermark M, Stroke 2006;37:979–985.

90% Sensitivity 70% specificity

<40% of normal

90% Sensitivity 86% specificity

1) Hakim AM J Cereb Blood Flow Metab 1989;9:523 2) Marchal G Stroke 1996;27:599 3) Schramm P Stroke 2002;33:2426

50 Y/F, fluctuating left facial

droop and left arm weakness(> 3 hrs)

CT Perfusion

Penumbra with no infarct No residual weakness following I/V tPA

2.5 hours left hemiparesis

A

NECT CBF CBV Day 5 NECT

Large penumbra with focal infarct in the right basal ganglia

CBF MTT

CBV

Matched Defect

No penumbra

No Treatment, Hemorrhage

Perfused-blood-volume

mapping.

(slow infusion technique)

• Quantitative cerebral blood volume

values are obtained by subtracting the unenhanced CT image data from the

CT angiographic source image data.

brain

evaluate cerebral blood flow and

mean transit time (hence, the

penumbra)

CT Angiogram

• to enable more accurate determination of prognosis

• To guide therapy

CT Angiogram

• Site of occlusion

• R/o arterial dissection

• grade collateral blood flow

• characterize atherosclerotic disease

• whole-brain "perfused blood volume map

CT Angiogram

Our Stroke Protocol (64

slice)

Time (in sec)

Slice Thickne ss

(in mm)

KV MA

Contrast

ml (ml/sec)

Comme nts

contrast

Brain

Other Emerging CT Imaging Techniques In