acute brain infarct:detection and delineation with ct angiographic source images versus nonenhanced

7/30/2019 Acute Brain Infarct:Detection and Delineation with CT Angiographic Source Images versus Nonenhanced

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Acute Brain Infarct:Detectionand Delineation with CTAngiographic Source Imagesversus Nonenhanced

Presented by : dr Rivani Kurniawan

Lecturer : dr Farhan Anwary .SpRad(K)MH.Kes

Erica C. S. Camargo, MD, PhD et all

RSNA, 2007 radiographics.rsnajnls.org


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Introduction

The Alberta Stroke Programme Early CT Score (ASPECTS) isan established scale for quantifying hypoattenuation fromacute stroke on non-enhanced computed tomographic (CT)scans and helps in the prediction of clinical outcome

ASPECTS has been used as a reliable and convenientsurrogate for visual interpretation of lesion volume not only onnon-enhanced CT scans but also on CT angiographic sourceimages and diffusion-weighted magnetic resonance (MR)

images

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The purpose of our study was to retrospectivelycompare the sensitivity and specificity of admissionnon enhanced CT scans with those of CT angiographicsource images in the detection of early ischemicchanges in middle cerebral artery (MCA) stroke and

to retrospectively compare admission non enhancedCT scans with CT angiographic source images in thedelineation of final infarct extent

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Material and methode

We analyzed data from 110 consecutive patientsenrolled in a prospective cohort study at twouniversity-based hospitals, part of the ScreeningTechnology and Outcomes Project in Stroke (alsoknown as STOPStroke), at which emergency CT

angiography for patients suspected of havingischemic stroke (stroke, transient ischemic attack, orstroke mimics) was performed

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Patients were excluded if iodinated contrast agentadministration was contraindicated (ie, history ofcontrast agent allergy, pregnancy, congestive heartfailure, increased creatinine level) or if there wasevidence of intracranial hemorrhage on non

enhanced CT scans

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Within our cohort, 82 patients had signs andsymptoms suggestive of MCA territory stroke andwere enrolled in the study from March throughAugust 2003. Of these, 51 patients who were imagedwithin 12 hours of symptom onset and who did not

have evidence of old strokes on admissionnonenhanced CT scans were included in the study.Mean patient age was 64.3 years (range, 2196years); 53% (27) were women and 47% (24)weremen

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Neuroimaging protocol

Non enhanced CT was

performed

120140 kVp, 170 mA,

2-second scan time,

and 5-mm section

thickness

Non enhanced CT and CT angiographic acquisitions were performed

according to standard departmental protocols with eight- or 16-section multi detector

CT angiography was performed

after a 25-second delay (40

seconds for patients in atrial

fibrillation) and administration of

100140 mL of a non ionic contrast

agent at an injection rate of 3mL/sec by using a power injector

via an 18-gauge intravenous

catheter. Parameters were 140 kVp,

220250 mA, 0.8 1.0-second

rotation time, 2.5-mm section

thickness.


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Follow-up neuroimaging as reference standard.1

All patients underwent follow-up neuroimaging studies within 10

days after stroke onset. The patients treating physicians

decided timing of follow-up imaging and the imaging modality to

be used

When available, preference was given to diffusion weighted MR images,

followed by fluid-attenuated inversion-recovery MR images, and finally

nonenhanced CT scans

When more than one appropriate follow-up image was available,we

selected for inclusion the follow-up image that most clearly confirmed the

presence or absence of a new ischemic stroke

.


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B

C

A

For non enhanced

CT scans, low-

attenuation regions in

the MCA territory that

were not suggestive

of encephalomalacia

and/ or chronic

infarction on the

admission non

enhanced CT scans

.

For diffusion-

weighted MR

images, hyperintense

regions in the MCA

territory, with

corresponding

restricted diffusion on

the apparentdiffusion coefficient

maps

For fluid-attenuated

inversion-recovery

MR images,

hyperintense regionsin the MCA territory

that were also not

suggestive of chronic

infarct and that

corresponded to

regions of restricteddiffusion on the

admission apparent

diffusion coefficient

maps

The criteria used to define the presence or

absence of an ischemic stroke on follow-upimages were as follows


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Image Review

Image review was independently on a picture archiving andcommunication system workstation by a board-certified

neuroradiologist and a clinical neurologist experienced in stroke

neuroimaging interpretation (M.H.L. and W.J.K., 15 and 25years of

neuroimaging review experience, respectively)

Reviewers were blinded to follow-up clinical and imaging

findings but had information in regard to the patientsage, sex,

and presenting clinical symptoms

Neither of the reviewers had participated in the selection of the

patients


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In all cases, non enhanced CT images obtained foracute stroke were reviewed first, followed by CTangio-graphic source images, and finally, follow-upimages for confirmation of true-positive or true-negative infarct regions.Disagreements in readings

were resolved in consensus

we reviewed each of 10 regions for the presence orabsence of ischemic lesions according to a five-pointlevel of certainty score (score 5,definitely present;

score 4, probably present; score 3, equivocal;score 2,probably absent; score 1, definitely absent)

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These regions included the insula (I), caudatenucleus (C), lentiform nucleus (L), internal capsule(IC), superior parietal lobe (M6), precentral and

superior frontal lobe (M5), anterior superior frontallobe (M4), inferior parietal and posterior temporallobe (M3), temporal lobe (M2), and anterior inferiorfrontal lobe (M1)

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Statistical analysis

Stroke detection: To compare stroke detection rates with non

enhancedCT and CT angiographic source images, weused standard receiver operating characteristic(ROC) curve analysis methods

The standard for the presence or absence of strokewas determined by using follow-up images

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Stroke delineation Standard linear regression coefficients were

calculated to determine the correlation of each of thenon enhanced CT scan and CT angiographic sourceimage ASPECTS with final infarct volumes on follow-up images by using the optimal level of certainty cutoff score

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Of the 33 patients with stroke, one had a top of theinternal carotid artery T lesion, three had internalcarotid artery and M1 MCA segment occlusions, sevenhad M1 MCA segment occlusions, two had M1 and M2MCA segment occlusions, and nine had M2 MCA

segment occlusions. No other arterial occlusionswere detected in the remaining 11 patients withstroke

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Stroke detection

With a level of certainty cutoff score of 4 or greater(probable, definite) for the presence of any acute

ASPECTS template ischemic hypo attenuation, strokedetection sensitivity was 48% (16 of 33) with nonenhanced CT scans and 70% (23 of 33) with CTangiographic source images

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Stroke delineation

For a cutoff score of 4 or greater, linear regressionanalysis revealed an R2 0.42 (P.001; slope1.53; 95%

CI: 1.01, 2.05) for correlation between admissionnon enhanced CT scan ASPECTS and follow-up imageASPECTS and an R 2 0.73 (P.001; slope 1.11; 95%CI: 0.91, 1.30) for correlation between admission CTangiographic source image ASPECTS and follow-up

image ASPECTS

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Discussion

CT angiographic source images were both

(a)more sensitive than non enhanced CT scansin the early detection of irreversible MCA

infarction within 12 hours of symptomonset

(b)more accurate than non enhanced CT scansin delineation of final infarct extent, as

measured by using ASPECTS

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The combination of vascular CT angiograms with

parenchymal CT angiographic source images,compared with admission non-enhanced CT scansalone, improves the overall accuracy of infarct

localization, vascular territory determination, vesselocclusion identification, stroke subtyping, andprediction of final stroke extent

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CT angiography with CT angiographic source imagesis typically more available, faster, affordable, andeasier to perform in critically ill patients than is MRimaging

When used in conjunction with quantitative first-pass

CT perfusion images, which provide a measure ofpenumbral tissue at risk, CT angiographic sourceimages compared with CT perfusion images forischemic lesion size mismatch have the potential toaid in the selection of patients for treatments in a

manner analogous to diffusion-weighted MR imagescompared with perfusion images for mismatch

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because non enhanced CT read-out was performed

prior to CT angiographic readout, this difference mayhave biased the detection of ischemic hypoattenuation with CT angiographic source images, as

readers were aware of the presence or absence ofintra- and ex-tra cranial arterial occlusions whenthey rated the CT angiographic source images

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This was a conscious intention of our study design,however, as the order of readout was chosen tosimulate the actual clinical scenario in which the nonenhanced CT scans are reviewed first. In-deed, thefact that readers were aware of pertinent presenting

signs and symptoms when they were interpreting thenon enhanced CT scans clearly influenced the pretestprobability that a given hypo attenuation was real orartifactual , although this knowledge should haveaffected the non enhanced CT scan and CTangiographic source image readouts equally

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awareness of the clinical history was intended to

simulate the clinical setting, and, if anything, the biasis toward favoring non enhanced CT scan sensitivity,as previous work has shown that knowledge of the

emergency clinical findings at presentation improvesdetection of stroke with nonenhanced CT scans (butnot with diffusion-weighted MR images)

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In conclusion, the results of our study support therole of CT angiographic source images, rather thannon enhanced CT scans alone, in improving both thedetection of early ischemic changes and theprediction of final infarct extent and, hence, favor the

use of CT angiography and CT angiographic sourceimages in the emergency setting for diagnosis andtri-age of patients with potential stroke.

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Material and methode

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We analyzed data from 110

consecutive patients enrolled in aprospective cohortstudy at two

university-based hospitals

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acute brain infarct:detection and delineation with ct angiographic source images versus nonenhanced

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