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Introduction:
Misr Radiology Center (MRC) has been always in
the front of extreme efficiency and scientific
excellence as regards all radiological and
imaging techniques. This is no where as true
as regards MRI with its rapid evolvement of
applications due to complex technological
advances.
At MRC, we do our best to keep up with such
advances in order to provide our referring
clinicians with state of the art MR
applications that definitively aid them with
their patient management.
We have an MR Philips (Intera) 1.5 Tesla, with
a gradient strength of 30 mT/min with the most
recent available software as were are
continuously upgrading our system.
In simple terms, the above means faster
acquisitions that decreases patients stay
inside the magnet and at the same time
acquiring high quality images during this
short period of time. In addition, this gives
us the capability to perform several state of
the art applications among which are MR
diffusion, MR perfusion, MR CSF flow, MR
spectroscopy, contrast enhanced MR angiography
for various vascular structures using bolus
tract method and also various post contrast
dynamic studies as for the breast, liver, soft
tissue tumors etc…
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Diffusion MRI
Diffusion is the
manner by which nutrients diffuse through
capillary wall. In MR diffusion, H2O motion is
measured with a constant known as Apparent
Diffusion Coefficient (ADC) measured in mm2/sec.
We can thus obtain Diffusion images (DWI), ADC
maps (images) and ADC values for a certain
region of the brain.
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Applications of MR diffusion:
Most important application is:
1.Evaluation of hyperacute stroke (5 mn - to 6
hrs from onset of clinical signs) for immediate
rt-PA management
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Case 1 (hyperacute infarction)?
Male patient aged 60 years presenting with
right sided hemiparesis since 3 hours.
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| CT scan
cut showing no particular finding |
DWI: faint
hypersignal of hyperacute infarction after
3 hours
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ADC
confirms DWI finding; hyposignal of left
MCA territory
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DWI:
definite hypersignal after 12 hours. |
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TOF-MRA
displaying no flow in left ICA & MCA .
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| Flair
sequence showing no particular finding |
DWI: bright right
sided hypersignal of hyperacute infarction
after 3.5 hours
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Corresponding FLAIR image |
Axial DWI
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Comment: FLAIR and DWI showing no
remarkable abnormalities at this level and all
other levels. As the DWI are normal then this
is a case of TIA because true hyperacute
infarct would have given an intensely bright
signal on diffusion images.
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applications of MR diffusion: |
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Other applications include:
2.Evaluation of hyperacute stroke (5 mn - to 6
hrs from onset of clinical signs) for immediate rt-PA
management
3.Differentiating true infarction from
transient ischemic attack (TIA)
4.Detecting the hyperacute or acute infarct
among multiple brain infarcts.
5.Grading of different brain neoplasm using
different ADC values.
6.Differentiating brain abscess & metastasis.
7.Differentiating extra-axial cysts as
arachnoid cyst from epidermoid cyst.
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| Case 5 (Low
grade glioma) |
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Female
patient aged 45 years presenting with
epileptic fits and headache. |
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A.Tumour shows high intensity on a
T2-weighted image
B.No enhancement is seen on a T1-weighted
image
C.On DWI, the tumor is isointense to
mildly hyperintense
D.On the ADC map, an ADC value of 1.4 was
found denoting low grade glioma |
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| Case 6 (High
grade glioma) |
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| 55 year
male patient presenting with signs and
symptoms of increased intracranial tension. |
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A.Hypointense tumour in the right
occipital lobe on a T2-weighted image
B.Relative homogenous enhancement is seen
after injection of contrast
C.On DWI, the solid part of the tumor is
isointense to mildly high in intensity
D.On the ADC map calculated ADC value was
of 0.8 was found denoting high grade
glioma |
Comment: From the above, we can see
that ADC values can grade gliomas as higher
ADC values (>1) denote non-restricted
diffusion found in low grade gliomas while low
ADC values (<1) denote more restricted
diffusion found in higher grade gliomas.
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| Male
patient aged 49 years presenting with low
grade fever and signs and symptoms of
increased intra cranial tension. |
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Axial T2-weighted fast SE |
Enhanced T1w |
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Axial DW Imaging |
Reduction in ADC value ranging from 0.3
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Multiple metastasis |
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patient aged 46 years presenting with
similar clinical presentation to case 5 |
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Axial T2w |
Non enhanced T1w |
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T1w post contrast |
Multiple metastases: DW Imaging |
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Corresponding ADC map |
ADC value for region of interest (solid
part of metastasis) is 1.4 |
Comment: Note that the abscess cavity
on DWI shows intense bright due to restricted
diffusion from increased proteinaneous and
cellular material with low signal on ADC (low
ADC value of 0.3) while in case 6 (multiple
metastasis) the necrotic cavity is of low
signal in ADC due to lack of cellular contents
with a high ADC value of 1.4. Is to be noted
that normal brain parenchyma is about 0.7.
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| Male
patient aged 70 years presenting with
dementia |
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Epidermoid cyst: T1-weighted SE |
Corresponding DW images |
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Isointensity with white and gray matter on
ADC maps |
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| Male
patient aged 50 years presenting with
headache |
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Arachnoid cyst: T1-SE+Gd-DPTA |
The arachnoid cyst has typical low signal
intensity on the DW image |
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Cyst isointensity with CSF on the ADC map |
Tips for MRI
MRI and pregnancy
No scientific evidence of any hazards of MRI
on the fetus, however, it is better generally
avoided in the first trimester except in very
urgent essential cases. Any MRI examination
can be done at any time during second and
third trimester.
P.S.: Wait for future MR tips in our
coming newsletter e.g. MRI contrats agents,
closed versus open MR, MRI and metallic
objects.
Next newsletters
- MR perfusion
- MR spectroscopy
- Contrast enhanced MR angiography
- MR CSF flow studies
- MR and liver transplant
- Dynamic MR studies for various organs
For more informations
Contact MRC at any time and ask for the
physician responsible for the MRI Unit.
________________________________________________________
Editor: Prof. Dr Yasser Abdel Azim,
Co-editor: Dr. Ahmed Samir Ibrahim, M.Sc.
Copyright © 2003 Misr Radiology Center
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