Download Brain Tumor Imaging

Brain Tumor Imaging
Ryan Murtagh, MD, MBA
University of South Florida
College of Medicine
Tampa, FL
Conventional – Advanced
Overview



Conventional, more traditional methods of
imaging
“Advanced” neuroimaging with MRI
Other modalities – important but not addressed
in this talk due to time

FDG PET, FMISO PET
Conventional – Advanced
Conventional modalities




X-ray
Angiography
CT
MRI
Conventional – Advanced
X-ray



Becoming a lost art
Good for bone, not for soft tissue
Can identify

Bony changes in skull
Lesions that destroy bone (lytic)
 Lesions that thicken bone (sclerotic)


Lesions that calcify or ossify

Meningioma
Conventional – Advanced
Angiography





Less of a role with advent of CT and MRI
Originally done by direct carotid injection
Improved technique with flexible catheters and
digital subtraction imaging (DSA)
In its day had much larger role in diagnosis
(tumor, trauma, hydrocephalus, etc…)
Now largely replaced by MRI and CT with
respect to tumor imaging
Conventional – Advanced
Angiogram
Conventional – Advanced
Computed Tomography
Conventional – Advanced
CT scan
Conventional – Advanced
CT in brain tumors

Diagnosis
Not as good as MRI but still good initial test
 Good for looking at edema/swelling and mass
effect
 Composition of hemorrhagic or calcified tumors


Peri-operative period


Post operative bleeding/complications
Management/follow-up
MRI better for tumor recurrence
 Pacemakers/MRI contraindications
 Role in shunt management, acute changes

Conventional – Advanced
Magnetic Resonance Imaging
Conventional – Advanced
MRI in Brain Tumors

Role in initial management:
Identifying first that there is abnormality in the brain
 Differentiating benign from malignant, some role in
grading
 Identifying size, location and relevant landmarks for
surgical/treatment planning



Peri-operative – complications of surgery and
baseline for future follow up
Follow up – to look for tumor recurrence
Conventional – Advanced
Example of CT vs MRI



New onset difficulty
speaking
CT shows large, low
attenuation lesion on left
Appearance suggests
pathology (infarct) but
not definitive
Conventional – Advanced
Acute infarct (stroke)
DWI
FLAIR
MRA
Conventional – Advanced
Difficulty speaking…b/c of GBM
FLAIR
T1 post
Conventional – Advanced
What are the limitations of MRI??





MRI, although better than CT, is not perfect
Most brain tumors have edema (swelling) and/or
enhancement – these are not specific to tumors
Edema
 Primary tumor, metastasis, MS, infection,
inflammation, trauma, etc…
Enhancement
 Tumors, radiation injury, post op granulation tissue,
MS, vascular malformations, infection,
inflammation, etc
Sometimes these lesions can look very similar on MRI
Conventional – Advanced
Tumor?
MS?
Radiation?
Infarct?
GBM
Radiation
Conventional – Advanced
Tumor?
MS?
Radiation?
Infarct?
Abscess?
Abscess
MS
Conventional – Advanced
Advanced techniques

Newer MRI techniques that can provide
additional useful information in diagnosis and
management of brain tumors
Spectroscopy
 Perfusion
 Functional MRI
 Diffusion weighted imaging/diffusion tensor
imaging

Conventional – Advanced
Spectroscopy
Conventional – Advanced
Spectroscopy



Noninvasive
MRI technique in which we are able to evaluate
biochemical composition of areas in the brain
Does not require contrast
Conventional – Advanced - Others
Major normal metabolites


Many metabolites in brain
Mainly follow:
NAA – N-acetyl aspartate
 Cho - Choline
 Cr – Creatine


Other minor metabolites
(lactate, glutamate,
“baseline”
glutamine, etc…)
3.5
3.2
Parts per million (PPM)
2.2
1.8
Conventional – Advanced
NAA



Resonates at 2.0 ppm
Marker found in normal
neurons
As a result, proportion of
NAA decreases with processes
that destroy or replace normal
neurons (neoplasm, infarct,
dementia/atrophy, etc…)
Conventional – Advanced
Choline



Peak is at 3.2 ppm
Involved in turnover
(building and breakdown)
of cell membranes
Therefore, increased with
processes with increased
cell turnover (like fast
growing tumors)
Conventional – Advanced
Creatine


Major component resonates
at 3.0 ppm (can have
second at 3.9 ppm)
Energy source – remains
relatively stable and is used
as comparison (relative
value for Cho and NAA)
Conventional – Advanced
When is it applicable?

Not a primary diagnostic tool (i.e. don’t do on
everyone) but helpful in ambiguous settings as a
problem solving tool
Tumor vs normal brain tissue in abnormal place
(called a hamartoma)
 Tumor vs benign lesion like multiple sclerosis
 Tumor vs radiation induced injury

Conventional – Advanced
Example: hamartoma or low grade tumor?
FLAIR
FLAIR
Conventional – Advanced
Hamartoma
FLAIR
Cho
Cr
NAA
Conventional – Advanced
Another patient – hamartoma or
tumor??
T1 post contrast
T2
Conventional – Advanced
Low grade tumor
Conventional – Advanced
Glioblastoma
Ch
Cr
NAA !?!
Lactate doublet
Conventional – Advanced
Perfusion
Conventional – Advanced
Conventional MRI
Regular MRI uses contrast to look for
enhancement on T1 weighted images.
 Tumors “enhance” because they have abnormal
blood vessels that allow contrast to “leak” out of
the blood vessels, accumulate, and cause signal
abnormalities that look bright on T1 imaging.
 Unfortunately, enhancement is not specific (also
see in radiation injury, infarct, MS, infection,
multiple others) so can often be confusing
 In addition, many tumors do not enhance early
on (or ever)

Conventional – Advanced
Perfusion Imaging



Measures amount of blood flow, volume and
speed as it passes through the tumor.
Independent of the integrity of the blood vessels
(i.e. don’t have to be “leaky”)
Can show entire area of increased
perfusion/increased vascularity, not just area
where there are abnormal vessels and
enhancement
Conventional – Advanced
Technique



Requires contrast
Administer contrast very quickly and image
rapidly and repetitively before, during, and after
the injection
Review the changes in the signal characteristics
of the area of interest as the contrast bolus
passes through
Conventional – Advanced - Others
Perfusion

Specifically, evaluation of the data can tell
you
How much blood flow (rCBF)
 How much blood volume (rCBV)
 The time to maximum amount of contrast (TTP)
 The total time for contrast to enter then leave
(MTT)


Data recreated in image form is called a
“color map”
Conventional – Advanced
rCBV
TTP
Color Maps
rCBF
MTT
Applications

Some of most useful applications for perfusion
imaging in tumors are
Differentiating benign from malignant
 Grading of a newly diagnosed tumor
 Determining highest grade portion of tumor for
biopsy/resection purposes
 Differentiating treatment related changes from
recurrent tumor

Conventional – Advanced
Benign from malignant


Benign lesions have lower perfusion while tumors
recruit vessels and have higher perfusion
Example:
FLAIR
T1 Post
Conventional – Advanced
Looks benign on spect/PET
Spectroscopy (basically normal)
Normal PET
Conventional – Advanced
Increased perfusion – biopsy proven LGG (WHO II)
rCBV
is
equal
to 2.4
Normal
WM
rCBV
of.56
Conventional – Advanced
Staging/Grading


Higher grade tumors  recruit more vessels  have
increased vascularity  have increased perfusion
Cutoff rCBV of around 1.7 low grade from high grade
Grade II
Grade III
Grade IV
Conventional – Advanced
Guide biopsy/treatment




Tumors do not grow homogeneously and often
have some areas of low grade cells and some
with high grade cells
Inappropriate biopsy can leave to understaging
and under-treatment
Areas of increased perfusion correlate with
higher grade cells
From this can guide biopsy, size of resection
Conventional – Advanced
low
high
Conventional – Advanced
Radiaton (XRT) injury




XRT often used in treatment of brain tumors
Tumors can enhance but so can radiation
induced injury (often very confusing on regular
MRI)
Radiation causes vascular injury and decreases
blood flow to tumor
Therefore, tumors have increased perfusion
while radiation changes are decreased
Conventional – Advanced
XRT injury
Conventional – Advanced
Another example
GBM treated with XRT
4 months later
Conventional – Advanced
Nodule is XRT but there is tumor
behind it
XRT
rCBV 2.3
Tumor
Conventional – Advanced - Others
Functional MRI
Conventional – Advanced
fMRI



“fMRI” often incorrectly applied collectively to
all techniques in this discussion
Correctly refers to the use of non contrast MRI
technique used to identify areas of increased
brain activity while doing specific tasks
Most commonly used MRI technique is BOLD
(Blood Oxygen Level Dependent) imaging

Identifies areas of greatest brain activity by
utilization of oxygen relative to less active brain
Conventional – Advanced
What are applications?


Extensively studied in psychiatry with memory
disorders, cognitive testing, etc…
Role in brain tumors mainly in identifying
eloquent structures relative to tumor
Guide approach
 Maximal safe resection


Most commonly used to identify the motor and
speech cortex for pre-surgical planning
Conventional – Advanced
General overview of fMRI paradigm (test)
REST
30 SEC
PERFORM
30 SEC
REST
30 SEC
PERF.
REST
PERF.
REST
30 SEC
30 SEC
30 SEC
30 SEC
Conventional – Advanced
Glioblastoma – preop fMRI study to
identify speech cortex
T1 post contrast showing the tumor
Conventional – Advanced - Others
Motor paradigm (finger tapping)
identifies motor cortex
T1 image with BOLD overlay
Conventional – Advanced
Speech paradigm (silent counting)
identifies area of speech activation
T1 post contrast
Conventional – Advanced
Example 2
non-enhancing left temporal lesion
Conventional – Advanced
Speech paradigm
shows right sided speech center
Conventional – Advanced
Diffusion weighted imaging
and diffusion tensor imaging
(DTI)
Conventional – Advanced
Diffusion Weighted Imaging


Diffusion imaging is (VERY simply) a non-contrast
MRI technique that allows us to see the direction and
rate at which water molecules flow.
Basis is that normal water motion is equally likely in all
directions (Brownian motion) – aka, isotropic
Conventional – Advanced
Diffusion Weighted Imaging



DWI done by (typically) applying three gradients
(fields) to area of interest
Processes that restrict the normal free motion of
water in any direction will cause an abnormality
on diffusion weighted imaging
These processes include (but not limited to):
Stroke – most common application
 Tumor
 Abscess

Conventional – Advanced
Example 1: Acute infarction
CT
MRI (FLAIR)
DWI
Conventional – Advanced
Diffusion weighted imaging in
tumors



Water movement on DWI is measured by
something called the Apparent Diffusion
Coefficient or ADC value
Measured in 10-6 mm2/s
ADC values shown to be useful in
Grading tumor
 Differentiating benign from malignant
 Differentiating tumor types (i.e. lymphoma vs
others)

ADC values in oligodendroglioma

ADC values can
differentiate grade II
vs grade III (using
cutoff of 925 10-6
mm2/s)
Khalid, et al, AJNR May 2012
Conventional – Advanced
Diffusion Tensor Imaging (DTI)




In DTI apply gradients in up to 256 different
directions (vs just 3 for DWI)
Each plane will produce a map (“tensor”) of
water motion in the plane
White matter tracts in brain are large
pathways of anisotropic water movement
From the compilation of DTI data can
recreate the major white matter tracts in the
brain (aka tractography)
Conventional – Advanced
DTI/Tractography




How is it useful clinically?
Tractography can identify damage/changes in
white matter very early (before see them on
MRI)
Microstructural changes in WM have been
studied in trauma and chronic diseases
(Alzheimers)
In oncology, mostly used for presurgical
planning to determine approach, resection
volume and maximal safe resection
Conventional – Advanced
DTI in 2D…

Compilation of DTI data
are presented in image
form as fractional
anistotropy (FA) maps
Color shows direction
 Intensity shows strength
and integrity of tracts

Conventional – Advanced
…DTI in 3D
Conventional – Advanced
Surgical applications of DTI in
the brain
In conclusion





CT is cheap, fast and good (but has radiation)
MRI is readily available and very effective in
diagnosis, peri-operative planning, and
management of brain tumors
MRI is not perfect and advanced neuroimaging
techniques like spectroscopy, perfusion, fMRI
and DWI/DTI can be useful as problem solving
tools (where available)
THANK YOU
[email protected]