1. health and fitness
2. disease

EL-MINIA MED., BULL., VOL. 16, NO. 2, JUNE, 2005
El-Gebaly et al
IMAGING OF ISCHEMIC CEREBERAL INFARCTION DURING THE 1ST
WEEK: THE ROLE OF DIFFUSION & PERFUSION WEIGHTED
MAGNETIC RESONANCE STUDY
By
Ahmed f. El-Gebaly*, Mahmoud R. Kandil** and *Moustafa Ezz El-Din
Departments of *Radiology and **Neurology, Assiut Faculty of Medicine
ABSTRACT:
The purpose of the study to evaluate the role of diffusion & perfusion functional MRI in
evaluation of the hyperacute and acute stroke patients and the benefit of each examination and
what can add. One hundred thirty patients with clinical suspicion of ischemic brain lesions
selected to this study. DWI was performed, Fluid Attenuation Inversion Recovery (FLAIR)
WI and T2WI sequences also done for comparison with the DWI; three-dimensional time of
flight (3D-TOF) magnetic resonance angiography (done in 86 patients) and perfusionweighted images were obtained following administration of a bolus of gadolinium (done in 31
patients). PWI images and color maps (rCBV, TTP, MTT) were generated. Patients were
classified according to the onset of the ischemic lesions into: Hyperacute ischemic infarction
Time period: Group I (< 6 hours from the onset), group II (patients presented at 6- 24 hours).
& group III ( presented from 1st to the 7th days from the onset) DWI b1000 showed the
ischemic lesions as a bright signal in all cases ( of the group I), with sensitivity of 100% for
detection of the ischemic lesions, while FLAIR sequence showed faint hyperintense signal in
13 cases and no lesions detected in 16 patients with a sensitivity of 44.8% for detection of the
ischemic lesions. MRA detect no abnormalities in 13 cases while diffuse atherosclerotic
changes were found in 39.2% of patients (51 patients). Perfusion study was done only in 17
cases of the 1st, in 7 cases of the 2nd group and in 7 cases of the 3rd group . We have only one
patient with mild affection of the penumbra (TTP delay from the normal state of perfusion was
less than 4 seconds while rCBV was normal), this patient received thrombolytic therapy with
good response. Six patients with moderate affection of the penumbra (The TTP delay was
between 4-6 seconds; one with decreased rCBV and 5 cases with average rCBV) Five of them
showed good response after thrombolytic therapy. Comparison of the size of the lesions of the
group (I) patients by perfusion and diffusion study revealed: Seven cases with PI and DWI of
the same size; two of them were with increased regional cerebral blood volume, one with mild
TTP delay, and the other with marked TTP delay. The remaining five cases presented with no
change of cerebral blood volume; two of them with mild TTP delay and the remaining three
cases with no TTP delay. Two patients presented with small lesion in DWI with no associated
PWI defect and patients received only supportive measures and complete recovery occurred
within 24 hours and diagnosed as TIA. Information obtained by MRI about an ischemic lesion
is so extensive and a single early MRI study is all that most patients presenting with stroke
syndrome will need. The ability of DWI to identify areas of cerebral ischemia and infarction
within hours of their presentation, with sensitivity reaching100%. Perfusion-weighted imaging
(PWI) provided an answer to a fundamental question prior to initiation of treatment: is the
ischemic brain parenchyma already reperfused, insufficiently perfused, or completely
avascular. PWI measures the severity of ischemia and accurately differentiates irreversibly
injured core from penumbral, salvageable tissue. Earlier and more accurate diagnosis by MRI
methods will reduce costs arising from diagnostic error and treatment delay.
KEY WORDS:
MRI
Hyperacute
Diffusion
MRA
162
Perfusion
TOF.
EL-MINIA MED., BULL., VOL. 16, NO. 2, JUNE, 2005
INTRODUCTION:
Management of acute stroke
patients increasingly driven by the
advanced
imaging
modalities3.
Consideration and imaging of four Ps
(namely; parenchyma, pipes, perfusion
and penumbra) in their correct order
are necessary to understand the cause
and potential treatment option for
stroke in a particular patient23
El-Gebaly et al
Perfusion-weighted
imaging
(PWI) provides an answer to a
fundamental question prior to initiation
of treatment: is the ischemic brain
parenchyma
already
reperfused,
insufficiently perfused, or completely
avascular?9. PWI measures severity of
ischemia and accurately differentiates
irreversibly
injured
core
from
6,13
penumbral, salvageable tissue .
Identifying a lesion in the “pipes”
has important therapeutic implication
for understanding the source of emboli
or thrombi, identifying the site of
potential thrombolysis and assessing
gross collateral flow patterns23 MR
angiography providing a relatively
easy, non-invasive, time-efficient and
straightforward screening procedure for
the determination of the site of intracranial occlusion. Most importantly,
MRA techniques have a high negative
predictive value. Thus’ a normal or
near-normal MRA of the carotid
arteries can effectively exclude the
possibility of a high-grade carotid
stenosis11. Unfortunately, MRA does
not currently have the resolution to
identify occlusions of the smaller distal
branch vessels reliably and MRA
cannot visualize the perforating
arteries, which are frequently the
etiology of lacunar and deep white
matter infarcts12.
MRI has superior sensitivity and
anatomic resolution. The soft tissue
resolution of structural MRI is finer
than CT, especially near bone and in
the posterior fossa. The likelihood of
positive diagnosis is therefore greater
for all lesions, including ischemic
ones8.
PATIENTS AND METHODS:
This study was carried out in the
MRI
Unit
of
the
Radiology
Department, Assiut University Hospital
from January 2003 to September
2003.One hundred thirty patients with
clinical suspicion of ischemic brain
lesions selected to this study and
classified according to the time of
onset of clinical symptoms.
All
patients were subjected to thorough
history taking, neurological examination and routine investigations.
MR imaging was performed with a
1.5-T superconducting magnet system
(Gyroscan ACS-NT; Philips Medical
Systems, Best, the Netherlands)
Within the ischemic cerebrovascular bed, there are two major zones
of injury: the core “severely ischemic
zone” and the peripheral surrounding
zone "ischemic penumbra”. The
ischemic penumbra
“the 4th P” is
functionally impaired yet still viable
tissue surrounding the ischemic core.
the penumbral zone is supplied with
blood by collateral arteries anastomosing with branches of the occluded
vascular tree. The penumbra is where
pharmacologic interventions are most
likely to be effective.22
DWI was performed with a
multislice, single-shot, spinecho echoplanner imaging (EPI) sequence with
imaging time 1 or 2 minutes. The rapid
acquisition times made cardiac or
respiratory gating unnecessary.
Axial Fluid attenuation recovery
(FLAIR WI) sequence was done for
comparison with the DWI and T2WI
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sequences for staging of the ischemic
insult, and exclusion of subarachnoid
hemorrhage.
El-Gebaly et al
20 cm). Images were obtained at 40
time points per section with average
scanning time ranged from 40 seconds
to 1 minute and 21 seconds.
Intra cranial three-dimensional
time of flight (TOF) magnetic
resonance angiography was done in 86
patients. Intra cranial MRA was
performed for the vertebro-basilar
system including the posterior cerebral
arteries, the intracranial internal carotid
system, including the middle cerebral
and the anterior cerebral arteries, at
level of circle of Willis, with settings of
TR35, TE 7.2, Flip angle 200, images
interpolated to 1.5-mm slice thickness,
matrix 200x512, field of view 20, scan
time 6.18 min and superior saturation
band.
PWI images were transferred to
workstation and color maps (rCBV,
TTP, MTT, T0) were generated
automatically then the concentration
time curve was obtained which
represent the changes occurred .
Firstly, ROI put in the contralateral
normal hemisphere as control normal
region, and then multiple ROIs was put
in the different region of the lesion and
surrounding it to show the extension of
the lesion.
RESULTS:
Patients are classified according
to the stage of infarction (according to
Wolfgang, 1998,28 into: Group I:
Hyperacute ischemic infarction; those
presented within 6 hours from the
onset [29 patients, 17 males and 12
females]. Group II (represent acute
ischemic infarction substage I)
represent those patient presented from
6 to 24 hours from the onset [ 33
patients; 15 males and 18 females] &
Group III (also called acute ischemic
infarction substage II) represent those
patient presented from 1 to 7 days
from the onset [68 patients, 35 males
and 33 females].
Subacute (Time period: 7 - 30 days)
and chronic infarctions (Time period:
>30 days) were excluded.
Perfusion-weighted
sequence
(done in 31 patients) were obtained
following administration of a bolus of
gadolinium diethylenetriamine pentaacetic acid (DTPA) in a dose of 0.1
ml/kg body weight = (10 ml). MRcompatible power injector used at a
speed of 3-5 mL/s followed by 20 ml of
normal saline delivered via a large-bore
cannula (18 or 20 gauge) in the
antecubital vein.
An echo-planar imaging gradientecho sequence at (TE =80 msec),
(TR=2000msec) and flip angle of 30
degrees was used. Section thickness
was 6 mm with no gap between slices
(matrix, 256 X 128; field of view, 40 X
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Table (1): Age groups and onset by time period of the studied patients.
Onset by time period
HyperacuteAcute
(Group I)
(Sub stage IGroup II)
1
1
1
1
5
5
16
13
5
8
1
4
1
29
33
20-30 years
31-40 years
41-50 years
51-60 years
61-70 years
71-80 years
81-90 years
As shown in table (1); in all
patients of the 3 groups, the fifth
decade represent the most affected
decade ( 55.17% of group I-39.4% of
group II and 32.35% of group III)
Total
Acute
(Substage II
Group III)
2
1
7
22
31
4
1
68
4
3
17
51
44
9
2
130
Recurrence is some what common
in the cerebro-vascular ischemia, as
previous strokes were seen in 29.2% of
cases (38 patients) and lacunar infarcts
detected by MRI in 47.7% of patients
(62 patients)
Hypertension and diabetes are the
most common predisposing factor.
While hypertension present in 55.38%
of patients, [72 patients; 31 males and
41 females] diabetes present in
21.54% of patients; [28 patients; 13
males and in 15 females] with
commoner association of predisposing
factors in females than in males.
MRA was done to two thirds of
the examined patients (86 patients) and
normal in 10% of cases (13 patients)
while diffuse atherosclerotic changes
were found in 39.2% of patients (51
patients)
Table (2): MRI findings in hyperacute ischemic infarction.
DWI
b1000
DWI
b0
FLAIR
29
Faint hyper
intense signal
0
0
3
0
0
13
0
T2WI
0
3
0
Bright signal
In group I patients (table 2);
diffusion weighted image (DWI)
(b1000) showed the ischemic lesions as
a bright signal in all cases, with
Iso intense
signal
0
No lesions
detected
0
Total
26
16
26
sensitivity of 100% for detection of the
ischemic lesions, while FLAIR
sequence showed faint hyperintense
signal in 13 cases and no lesions
165
29
29
29
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detected in 16 cases with sensitivity of
44.8% for detection of the ischemic
lesions. Both DWI b0 and T2WI
showed faint hyperintense signal in 3
cases and no lesions detected in 26
cases with sensitivity of 10.3% for
detection of ischemic lesions.
El-Gebaly et al
100% for detection of the lesions,
while FLAIR sequence showed bright
signal in 64 cases and faint hyperintense signal in 4 cases with sensitivity
of 100% for detection of the lesions.
Both DWI b0 and T2WI showed hyper
intense signal in 63 cases, faint
hyperintense signal in 4 cases and no
lesions detected in only one case with
sensitivity of 98.5 % for detection of
the lesions.
Similarly, in group II patients
(Table 2); (DWI) showed the ischemic
lesions as a bright signal in all cases,
with sensitivity of 100% for detection
of the lesions, while FLAIR sequence
showed bright signal in 19 cases and
faint hyperintense signal in 13 cases
and no lesions detected in only one
case with sensitivity of 96.9% for
detection of the lesions. Both Diffusion
b0 and T2WI showed hyperintense
signal in 13 cases, faint hyperintense
signal in 11 cases and no lesions
detected in 9 cases with sensitivity of
72.7% for detection of the lesions.
ADC map also done in 60 patients
in our study; 4 patients in group I
showing hypointense signal in all of
them with the ADCr value measuring
<1. Thirteen patients from group II
and Twenty nine patients from group
III showed hypointense signal in all
the them with the ADCr value
measuring <1.
Thirty-one patients were evaluated
with perfusion study in various stages
of ischemia. Perfusion study was done
only in 17 cases of the 1st group, in 7
cases of the 2nd group and in 7 cases of
the 3rd group.
By the same manner; in group (III)
patients; DWI b1000 shows the
ischemic lesions as bright signal in all
cases (68 patients), with sensitivity of
Table (3): Relationship between rcbv and TTP delay in cases with mismatch between
PI and DWI (PI>DWI)
TTP delay
< 4sec:
decrease
yet still
good
perfusion.
Regional
rcbvr<1
cerebral blood
No difference
volume ratio
between Rt.
surrounding
and Lt. sides
the lesion
Total
>6-10sec:
4-6 sec: mild
bad
to moderate
perfusion.
decrease
perfusion.
1
1
5
1
6
The volume of the perfusion
abnormality was only assessed on the
MTT maps because these maps provide
the
best
contrast
between
a
Total
1
2
6
1
8
hypoperfused region and normal brain
(As decided by Schlaug and Benfield,
199926. The main advantages of using
Time to peak (TTP) maps to visualize
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the perfusion deficits being easy to
generate, time required for postprocessing is minimal, and abnormal
regions can be easily identified and
delineated. With regional cerebral
blood volume (rCBV) and rCBF maps,
the borders of the lesions are often less
distinct than on the TTP (or MTT)
maps
El-Gebaly et al
categorized the eight cases with
PI>DWI lesion into those with mild,
moderate and severe affection of the
penumbra region (Table 3).
Mild affection of the penumbra
was defined as the TTP delay from the
normal state of perfusion was less than
4 seconds while rCBV (state of
collateral)
was
normal/mildly
decreased/mildly increased. We have
only one patient in this group. Also, we
have 6 patients with moderate affection
of the penumbra (as defined above).
Severe affection of the penumbra was
defined as the TTP delay of more than
6 seconds up to 10 seconds, and with
rCBV markedly decreased and we have
only one patient in this group.
TTP measurements: in normal
brain usually measures 20-26 sec, may
be more if there was delay in starting
injection, so better to compare TTP
between normal and abnormal sides
(that also recommended by the study of
Shih et al, 200327 (Table 3).
According to Neumann et al.,
199916 and Abbas et al., 20022, we
Table (4): Different patterns of combined DWI and perfusion MRI study in group
(I) of patients.
Combined PI and DWI
lesion
PI>DWI lesion
PI and DWI deficits of
similar size
DWI deficit but no PI
deficit
Total
Frequency
8
7
47%
41.1%
2
11.7%
17
Comparison of the size of the
lesions of the group (I) patients by
perfusion and diffusion study revealed
(table 4): Seven cases with PI and DWI
of the same size; two of them were
with increased regional cerebral blood
volume, one with mild TTP delay, and
the other with marked TTP delay. The
remaining five cases presented with no
change of cerebral blood volume; two
of them with mild TTP delay and the
remaining three cases with no TTP
delay and this group of patients were in
need only for neuroprotective therapy.
Two patients presented with small
Percent %
100%
lesion in DWI with no associated PWI
defect and patients received only
supportive measures and complete
recovery occurred within 24 hours and
diagnosed as TIA.
In group II of patients;
7
examined by perfusion and three of
them had PWI lesion larger than DWI
lesion, while in the group III, from the
7 examined by perfusion MRI, we
found PWI lesion larger than DWI
lesion associated with moderate TTP
delay in three patients and one with
marked TTP delay.
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CASE PRESENTATION:
Figure (1) Hyertensive male patient aged 62 years presented with Rt. sided hemiparesis of 10
hours duration with history of old cerebro vascular stroke. (A) T2WI, (B) FLAIR, (C)
Diffusion b1000, (D) ADC Map show old Rt. Cerebellar infarction that appear bright only in
T2WI, dark in FLAIR and Diffusion b1000 which is bright again in ADC map, ( E)DWI
b1000 & (F) ADC map Recent Lt. parietal infarction which appear bright in DWI and is
confirmed by exhibiting dark signal in ADC
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Figure (2) Hypertensive female patient aged 59 year’s old presented with right sided
hemiparesis of 2days duration. (A) Axial DWI b1000, (B) Coronal DWI b1000, (C) FLAIR
and (D) T2WI show acute infarction in the left middle cerebral peduncle, exhibiting bright
signal in DWI b1000 and faint bright signal in both FLAIR and T2WI
(E) & (F) 3D TOF MRA show stenotic segment at the M1 segment of the left MCA,
atherosclerotic changes of the posterior circulation with multiple stenotic segments detected
at the basilar, posterior cerebral arteries more on the left PCA. Associated dominant right
vertebral artery.
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Figure (3) Hypertensive female patient aged 62 years old presented by sudden onset of Lt.
Sided flaccid weakness, difficult articulation and deviation of the mouth to the Rt. Side of 5
hours duration.
(A) Diffusion b1000, shows hyperintense signal in the genu and post limb of Rt. Internal
capsule extending to Rt. Corona radiata. (B) T2WI, (C) FLAIR show normal study.
(D) Post Gd T1WI shows positive leptomeningeal collaterals.
(E) rCBV map shows increased rCBV on the right side signifying good leptomeningeal
collaterals.
(F) Source Image, (G) corresponding intensity time curve showing that ROI 2 that represents
the hyper intense signal in DWI appear with TTP delay of 10 sec, with no decreased rCBVr
in comparison with the normal left side. With ROI 3 and ROI 4, there is no penumbra with
increased rCBVr signifying good collaterals.
(H) 3DTOF MRA showing occluded RT. ICA at the cavernous and supracavernous portions
with cross filling of ACA through A Com.
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Figure (4) Hypertensive male patient aged 49 years presented with left sided hemiparesis of 6
days duration, patient had a history of previous cerebro vascular stroke.
(A) &(B) Diffusion b1000, (C) & (D) T2WI, (E) & (F) FLAIR showing acute infarction in the
territory of Rt. ACA, exhibiting bright signal in DWI b1000, T2WI and FLAIR sequences,
with old infarction in the left parieto-occipital region exhibiting hyper intense signal in
T2WI, hypo intense signal in both DWI b1000 and FLAIR, multiple lacunar infarcts at
periventricular regions bilaterally.
(G) 3D TOF MRA shows thrombosis of A1 segment of Rt. ACA, with stenosis at M1 segment
of Lt. MCA.
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Figure (5) Diabetic female patient aged 66 years old presented with sudden onset of
right sided hemiplegia of 5 hours duration, she had a history of mitral valve stenosis,
atrial fibrillation and ischemic heart disease. (A) T2WI shows completely normal
brain.(B) FLAIR shows small area of very faint intense signal in the left frontotemporal region. (C) DWI b1000 shows a relative large zone of restricted diffusion
in the left fronto-temporal region displaying hyperintense signal with central light
bulb.
(D) rCBV map shows hypoperfused area in left fronto-temporal region with ROI 2 on
the center of this area and ROI 3 at the periphery. The contralateral hemisphere
appears normal (with ROI 1 upon) .
(F) Signal intensity time curve shows multiple ROIs which reveal that the normal one
(area 1) show T0 = 26sec; The central area (area 2) represent flat curve which mean
completely absence of CBF and the peripheral area (area 3) show slight TTP delay;
TTP = 28 sec with delayed TTP about 2 sec from normal curve, no definite changes of
rCBV of this area when compared with the same contralateral zone suggesting good
collateral flow; which means no expected extension of the infarct size from the
original size on DWI.
(G) 3DTime-of-flight MR angiography (MRA) showing: obstruction at the junction
between M1 and M2 segments of the left MCA.
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Figure (6) Diabetic and hypertensive female patient aged 60 year’s old presented with left
sided hemiparesis of one and half hour duration.
Diffusion b 1000, (B) FLAIR, (C) T2WI showing small ischemic infarction in the right high
parietal region, exhibiting bright signal in DWI, faint hyper intense signal in FLAIR and not
visualized in T2WI
(D) Time intensity curve (E) rcbv map, (F) TTP map showing relative TTP delay 2 sec with
good rCBVr reaching 0.9 of the normal rCBV on the left side, meaning good collaterals, this
patient was not in need for rTPA injection, complete recovery occurred with intra venous
heparin as the rTPA was not available at that time.
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Figure (7) Female patient aged 26 years presented with loss of consciousness of one day
duration with no specific neurological manifestations.
(A); T1WI demonstrates a loss of normal flow void in the superior sagittal sinus having been
replaced with an isointense signal.
& (C); T2WI and (D) & (E); FLAIR WI revealed faint hyperintense signal within both
cerebral hemispheres.
(F) & (G); DWI b1000 demonstrates multiple bilateral symmetrical increase in signal
intensity within the parenchyma (infarcts) in the high cerebral convexity, parasagittal
regions, involving both the ACA and MCA territories.
(H) & (I): ADC map show the lesions as hypointense signal confirming acute ischemic insult.
(J); 3D MRV Sagittal MR venogram demonstrates lack of normal flow within the area of the
superior sagittal sinus
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Figure (8) Female patient aged 53 years presented with dysarthria, Lt. sided numbness and
weakness of 5.5 hours duration. (A) Diffusion b1000, (B) FLAIR, (C) T2WI showing Rt.
Ventro posterior thalamic nuclear small focus of DWI restriction which appear as faint
hyper signal intensity in both FLAIR and T2WI possibly representing infarction.
(D) 3D TOF MRA revealed normal study
(E) Source image (F) Time intensity curve showing normal perfusion study with no
perfusion defects and with symmetrical curves on right and left cerebral hemispheres,
patient improved after medical treatment and this patient represents an example of TIA with
persistent lesions in MRI study, with no perfusion defects and with clinical recovery
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Figure (9) Male patient aged 33 years with known right frontal glioma, the patient developed
disturbed level of consciousness of 3 hours duration.
(A) FLAIR, (B) T2WI, (C) Post Gd T1WI show large Rt. fronto-temporal low grade glioma
(arrow) exhibiting bright signal in FALIR and T2WI with surrounding vasogenic edema
(short arrows) and post Gd heterogeneous enhancement.
(D) Diffusion b1000 shows mild hyperintense signal in the Rt. Fronto-temporal region from
the edema and also shows bright signal in the Rt. occipital region (short arrows).
(E) 3D TOF MRA showing marked displacement of both ACAs to the left side from the
tumor and surrounding edema (arrows).
(F) Time intensity curve showing decreased rCBVr on Rt. Occipital lobe reaching 0.48
compared with the normal left occipital lobe, with TTP delay of 2 sec yet with no flat curve
denoting ischemic not infarcted area.
(G) Source Image, (H) Time intensity curve after application of the ROI at the periphery of
the tumor showing increased rCBVr compared with normal brain at the left side.
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El-Gebaly et al
infarct events1. Gonzalez et al, 1999
have verified the ability of DWI to
identify areas of cerebral ischemia and
infarction within hours of presentation,
with sensitivity ranging from 94%100%7. Nouh and Aref, 2002; have
shown that hyperacute ischemic infarcts
were detected only in diffusion
weighted sequence and not seen in both
FLAIR and T2WI sequences17.
DISCUSSION:
Stroke MRI can not determine in
which patient vessel occlusion will
persist and in which patients vessel
recanalization will occur (no imaging
modality can answer this question at
present), however, it can answer the
critical questions of who may profit
from
recanalization,
in
whom
recanalization should be achieved by all
means, and in which patients there is no
tissue at risk or no ischemic disease at
all but only an excessive risk of
hemorrhage due to thrombolytic
therapy 25.
Apparent
diffusion
coefficient
(ADC) map are useful for estimating
lesion’s age. Acute ischemic lesions
are characterized by a high signal on
DWI and a low ADC. The mean ADCr
of ischemic lesions gradually increases
overtime, but remains significantly
decreased relative to that of a
contralateral control region for the first
7days after symptom onset, in agree
with
Marten et al, 200115 that
conclude’ in the ADC maps, the lesion
is hypointense up to day 7 and
hyperintense at 27 days, making it
possible to differentiate the acute from
the chronic lesion Our study revealed
the same findings explained by the
previous studies of Lutsep et al, 199714
and Jonathan et al, 199910. Patients in
hyperacute and acute ischemia substage
I & substage II (more than 6 hours –
7days) showed hypo intense signal in
all cases with the ADCr value
measuring <1 in all of them. An
additional benefit of DWI and ADC
map is that if they are completely
normal in a symptomatic patient, this
means that he is probably during a TIA
and that she-does not need immediate
injection therapy unless symptoms
persist and the DWI and ADC become
abnormal 20.
In our study of stroke patients, the
peak age of affection was between 5070 years (73%, 95 out of the selected
130 patients) of patients and men were
affected more than women (51.54%,,
67 males versus 63 females) and these
results were in agreement with many
investigators as Reeves et al, 2002 that
found the chance of having a stroke
more than doubles for each decade of
life after age of 55. 21
A new extension of a previous
ischemic lesion is identified using
DWI. Extensions of previously
established infarcts are frequently
difficult to identify on T2WI or FLAIR
images because of the similarity in
signal characteristics18.
In our study, Twenty nine patients
came within 0-6 hours from the onset
of symptoms and DWI b1000 showed
the ischemic lesions as a bright signal
in all cases, with sensitivity of 100%
for detection of the ischemic lesions,
while FLAIR sequence showed faint
hyperintense signal in 13 cases and no
lesions detected in 16 cases with
sensitivity of 44.8% for detection of the
ischemic lesions. This matches with
the study of Abbas and Aref, 20001;
they concluded that functional MR
sequence is very sensitive to hyperacute
Time of flight (TOF) MRA
technique gives the managing physician
an idea about the overall cerebral
vascular channel morphology and thus
has an important prognostic and
prophylactic value in the patient’s
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EL-MINIA MED., BULL., VOL. 16, NO. 2, JUNE, 2005
management. Clear demarcation of the
irreversibly damaged infarct core and
the ischemic but still viable and thus
salvageable tissue at risk of infarctions
seen on DWI/PWI/MRA should be
obtained before thrombolysis is
initiated within 3 to 6 hours19.
El-Gebaly et al
collateral)
was
normal/mildly
decreased/mildly increased. We have
only one patient in this group; this
patient received only IV heparin with
good response for the patient.
We have 6 patients with
moderate affection of the penumbra (as
defined above); one with decreased
rCBV and 5 cases with average rCBV.
Five of them received thrombolytic
therapy with good response occurs in
all of them, and the other patient;
unfortunately’ had history of bleeding
peptic ulcer and thrombolytic therapy
could not be given.
Three descriptors of perfusion
data (CBV, CBF, and MTT), all were
useful in imaging acute cerebral
ischemia. Of these three, CBV maps
have been shown to correlate best with
final infarct volume24 MTT is an easyto-interpret but has a tendency to
overestimate infarct size. Regional
cerebral blood flow (rCBF) maps may
include flow that comes in via collateral
vessels, and thus gives a snapshot of
cerebrovascular reserve All of these
perfusion techniques (both MRI and
non-MRI) appear to be unable to
distinguish between acute and chronic
hemodynamic compromise.Fortunately,
DWI can easily make this distinction6
.
Well-performed perfusion data
sets have a steady baseline followed by
a clear-cut arrival of the contrast bolus.
The signal drop is typically 20-30% or
more, has a relatively narrow time
course, and often a second smaller drop
in signal can be seen as the bolus
recirculates. Finally, the intravascular
contrast
has
some
residual
susceptibility effects, causing a slight
drop in signal (a few percent) compared
to pre-baseline.
Severe
affection
of
the
penumbra (TTP delay of more than 6
seconds up to 10 seconds, and with
rCBV markedly decreased), we have
one patient in this group and received
rTPA with no good respond as expected
from the bad perfusion curves with
improvement only in the level of
consciousness.
In hyperacute stroke patients if a
perfusion deficit is larger than a
diffusion deficit’ this implies the
presence of at risk hypoperfused tissue
(ischemic penumbra), which may be
salvageable with therapeutic restoration
of blood flow (reperfusion therapy e.g.,
thrombolysis)19.
Perfusion imaging deficit > DW
imaging deficit; those patients were
amenable for thrombolytic therapy, and
this is the most frequent pattern seen in
our study as we have eight patients out
of 17 patients studied with diffusion
and perfusion MRI with PWI>DWI in
hyperacute stage ( group I patients)
According to Neumann et al,
199916 and Abbas et al, 20022, we
categorized
the eight cases with
PI>DWI lesion into those with mild,
moderate and severe affection of the
mismatch or penumbra region.
In the group (I) of patients,
whenever PWI and DWI deficits of
similar size, this means that there is no
mismatch with no surrounding tissue at
risk and those patients are in need for
Mild affection of the penumbra
was defined as the TTP delay from the
normal state of perfusion was less than
4 seconds while rCBV (state of
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EL-MINIA MED., BULL., VOL. 16, NO. 2, JUNE, 2005
neuroprotective therapy only as there is
no tissue at risk that needs
thrombolysis.. In our study all cases
detected in this group receive only
neuroprotective therapy and recovery of
the patients was detected in all of them.
El-Gebaly et al
When, neither PWI nor DWI
lesions despite clinical deficit and this
is associated with TIAs. The patients of
this pattern were not in need for acute
interventional treatment unless symptoms persist and the DWI and ADC
become abnormal8,20.
If PWI less than that of DWI
deficit. This is explained by early
partial reperfusion that had occurred
before scanning but after the onset of
irreversible tissue damage. Other
possible explanations for this pattern
might relate to the establishment of
collateral
circulation
despite
a
persistently occluded feeding artery.
This DWI deficit correlated well with
the final infarct volume as there was no
potentially salvageable or "at risk"
tissue within the infarct at the acute
scan, and hence no enlargement of the
DWI lesion was likely expected In
some instances, DWI deficit only but
no PWI deficit and this means that early
full reperfusion had occurred before
scanning but after the onset of
irreversible tissue damage. In those
patients, no expected benefit from
thrombolytic
or
revascularization
therapies, with the added risks of such
treatment, but may be candidates for
neuroprotective strategies only4, 5.
In group II of patients;
7
examined by perfusion and three of
them had PWI lesion larger than DWI
lesion associated with moderate TTP
delay but they were not candidate for
thrombolytic therapy as they passed the
time window for that treatment. In the
group III, from the 7 examined by
perfusion MRI, we found PWI lesion
larger than DWI lesion associated with
moderate TTP delay in three patients
and one with marked TTP delay but
still not a candidate for thrombolytic
therapy as he passed the recommended
time window for that treatment.
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If PWI deficit detected without
DWI deficit, this means that the degree
of tissue hypoperfusion had not reached
to the threshold value for development
of hyperintensity on DWI. The patients
of this pattern either show spontaneous
restoration of clinical and perfusion
deficits within hours of imaging or
others failed to improve clinically or
radiologically and transition to infarction may occur. Thus, the absence of a
DWI lesion is not a false negative
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Advantage of Modified MRI protocol
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‫‪El-Gebaly et al‬‬
‫‪EL-MINIA MED., BULL., VOL. 16, NO. 2, JUNE, 2005‬‬
‫تقييم اإلحتشاء الدماغي في األسبوع األول‪ :‬دور الفحص بالرنين المغناطيسي‪:‬‬
‫نظامي االنتشار واإلرواء مقارنة بالفحوص األخرى‬
‫أحمد فتحي الجبالي*‪ -‬محمود رأفت قنديل** ‪ -‬مصطفى عزالدين*‬
‫أقسام *األشعة التشخيصية و**األمراض العصبية‪ -‬كلية طب أسيوط‬
‫تم فً هذه الدراسة فحص مائة وثالثٌن مرٌضا من المرضً المترددٌن على وحدة الرنٌن المغناطٌسً‬
‫بمستشفى أسٌوط الجامعً والمحولٌن من قسم األمراض العصبٌة بالمستشفى إلصابتهم بقصور الدورة‬
‫الدماغٌة‪.‬‬
‫وقد قسم المرضى لثالث مجموعات رئٌسٌة‪ :‬المجموعة األولى وتشمل تسعة وعشرون مرٌضا ممن لدٌهم‬
‫األعراض فً غضون الساعات الست األولى أما المجموعة الثانٌة ( ثالث وثالثون مرٌضا) فتشمل أولئك‬
‫المرضى الذٌن تم فحصهم فً خالل األربع وعشرٌن ساعة األولى والمجموعة الثالثة (ثمانٌة وستون‬
‫مرٌضا) تشمل أولئك المرضى الذٌن وصلوا فً غضون األسبوع األول‪.‬‬
‫تم عمل الرنٌن المغناطٌسً تقنٌة االنتشار ( ‪ )DWI‬لكل المرضى وأثبت حساسٌة ‪ %011‬فً اكتشاف‬
‫اإلحتشاء الدماغً فً الساعات األولى وأظهر التأثٌرات التً لم تظهر فً كافة الفحوص األخرى‬
‫وقد أجري الفحص لشراٌٌن المخ بالرنٌن المغناطٌسً تقنٌة ( ‪ )TOF‬لستة وثمانون من المرضً وأظهرت‬
‫النتائج سالمة الشراٌٌن فً ثالثة عشر مرٌضا بٌنما توجد ترسبات متكلسة منتشرة فً واحد وخمسون‬
‫مرٌضا وهو فحص آمن ٌمكن إجراؤه لكل المرضً وٌعطً فكرة جٌدة فً غالب األحٌان عن حالة الشراٌٌن‬
‫بالمخ بٌد أنه ال ٌصل إلى التفرعات الدقٌقة مع أنه غٌر دقٌق نسبٌا فً قٌاس مدي ضٌق الشراٌٌن‪.‬‬
‫وأٌضا تم عمل تقنٌة األرواء (‪ )Perfusion‬إلحدى وثالثٌن مرٌضا ( سبعة عشر من مرضى المجموعة‬
‫األولى وسبعة من مرضى المجموعة الثانٌة وسبعة من مرضى المجوعة الثالثة) وأٌضا تم عمل خرائط ملونة‬
‫لمعدل وصول الدم لألجزاء المصابة وما حولها (خاصة منطقة شبه الظل المحٌطة بمنطقة اإلحتشاء الدماغً‬
‫‪)Penumbra‬‬
‫ً‬
‫أظهر الفحص باإلرواء منطقة شبه الظل متأثرة تأثرا بسٌطا فً أحد مرضى المجموعة األولى وقد تحسن‬
‫تماما مع إعطاء مذٌبات الجلطات بٌنما أظهر تأثٌرا متوسطا لمنطقة شبه الظل فً ستة من مرضى المجموعة‬
‫األولى وقد تحسن خمسة منهم بعد العالج بمذٌبات الجلطات‬
‫وبمقارنة نتائج اإلرواء واالنتشار لمرضى المجموعة األولى تبٌن أنه فً ثمانٌة من المرضى كان حجم‬
‫اإلصابة باستخدام اإلرواء أكبر من حجم اإلصابة باستخدام االنتشار وهؤالء هم المتوقع أن ٌكون لدٌهم‬
‫استج ابة للعالج بمذٌبات الجلطات وقد حدث ذلك بٌنما أظهرت مقارنة النتائج أن اثنٌن من المرضى لدٌهم‬
‫إصابة ظاهرة فً الفحص باالنتشار بٌنما ال توجد إصابات ظاهرة فً الفحص بتقنٌة اإلرواء وهؤالء هم‬
‫مرضى اإلحتشاء المؤقت ( ‪ )TIA‬وقد تحسنا تماما فً خالل أربعة وعشرٌن ساعة‬
‫و ٌخلص البحث إلى أن الفحص بالرنٌن المغناطٌسً هو الفحص األمثل لحاالت السكتة الدماغٌة خاصة بعد‬
‫وجود تقنٌات األرواء واالنتشار وأٌضا فحص شراٌٌن المخ بالرنٌن المغناطٌسً وبمقارنة كل هذه التقنٌات‬
‫نستطٌع التشخٌص الدقٌق لهؤالء المرضى وتحدٌد خرٌطة العالج بصورة صحٌحة‬
‫‪181‬‬