2. WHY THIS?? WHY NOT CT/MRI
Brain disorders start with functional abnormalities
that result in either an increase or decrease in
glucose metabolism at a cellular level. These
functional changes precede the formation of an
abnormal mass, the shrinkage of brain tissue, or
other abnormalities seen on anatomical
imaging, sometimes by years. PET and PET/CT
imaging can show precise areas of increased or
decreased glucose metabolism in the brain.
4. Table 7.2 -- RADIOPHARMACEUTICALS COMMONLY USED FOR A RANGE CLINICAL PROBLEMS
Clinical problem
Radiopharmaceuti
Imaging technique cal
Biological behaviour
Head
Cerebrovascular accident
Cerebral perfusion
SPECT
99mTc
HMPAO
Uptake proportional to
blood flow
Hydrocephalus
CSF rhinorrhoea
Cerebrospinal fluid 111In DTPA
(CSF) study
(intrathecal)
Encephalitis
Blood–brain barrier
(BBB) study
99mTc
HMPAO
Passage across
disrupted BBB
Dementia
Cerebral perfusion
SPECT
99mTc
HMPAO
Uptake proportional to
blood flow
Cerebral
metabolism PET
18F
Ictal SPECT
99mTc
Interictal PET
18F
Epilepsy (presurgical localization)
Marker of CSF flow.
Marker of glucose
fluorodeoxyglucose metabolism
HMPAO
Uptake proportional to
blood flow
Marker of glucose
fluorodeoxyglucose metabolism
5. PET AND SPECT SCANNING
Two high-powered imaging instruments in nuclear
medicine
use the tomographic approach
and range in the same general size ,category and cost,
especially designed to monitor dynamic processes such
as blood flow and cell metabolism.
SPECT instrument preceded in general use,, the later
PET technology.
Both instruments use a Gamma camera to detect gamma
ray photons emitted from the radioisotopes used in
imaging the body.
6. Image of a typical positron emission
tomography (PET) facility
8. Positron emission tomography= PET
= technique that permits noninvasive in vivo
examination of metabolism, blood flow, electrical
activity, neurochemistry
Concept:
The system detects pairs of gamma rays emitted indirectly by a
positron-emitting radionuclide (tracer), which is introduced
into the body on a biologically active molecule.
Labeling:
PET compounds---- radiolabeled with positron-emitting
radionuclides
9. • modern PET scanners
three dimensional imaging
with the aid of a CT X-ray scan performed on the
patient during the same session,
in the same machine.
•
HYBRID PET/CT IMAGING
10. Indications OF PET imaging
A----ONCOLOGIC
1-Brain tumor:
a)
tumor grading +estimation of prognosis
b)
Localization of optimal biopsy site(most malignant area--max.uptake)
2-radionecrosis versus residual / recurrent tumor
• decreased FDG uptake in necrosis
3-response to chemo- / radiation therapy
4-prediction of patient's average survival in pediatric primary
brain tumors:
•
6 months if FDG uptake = gray matter;
•
1-2 years if FDG uptake > white matter;
•
2.5 years if FDG uptake = white matter;
•
3 years if FDG uptake < gray matter
12. CONTRAINDICATIONS(PET)
Recent chemotherapy---min. interval of 2-3 wks
recommended
Recent radiotherapy–--- min. interval of 8-12 wks
recommended
Poorly controlled diabetes---serum glucose>8.5
mmol l at the time of scan.
13. radiopharmaceuticals
• GLUCOSE METABOLISM
•
for measurements of metabolic rate + mapping of functional activity
•
•
•
•
•
C-11 glucose:
rapid uptake, metabolization, and excretion by brain
F-18 fluorodeoxyglucose (FDG):
A gl.analogue,,cmpetes with gl.--------and
diffuses across blood-brain barrier --the brain is normally a
rapid user of glucose, since brain pathologies greatly decrease brain
metabolism of glucose
The consumption of FDG--- indicates the extent of
brain activity.
•
By indicating the consumption of FDG, PET imaging
gives---------a key to the working of a patient's brain
•
14. TECHNIQUE(FDG PET Imaging)
FDG = glucose analogue tracer 2-[fluorine-18] fluoro-2-
deoxy-D-glucose
Preparation:
fasting for 4-18 hours (FDG tumor uptake is diminished by an
elevated serum glucose level)
Dose: 10 mCi (370 MBq)
Physical half-life: 110 minutes
Imaging time:
50-60-70 minutes after administration (trade-off between
decreasing background activity and declining counting statistics)
15. Image Interpretation (PET)
FDG-PET
Glucose is the major source of energy for
the neurons.
FDG behaves as Glucose
Uptake in the neuron through GLUT1 and GLUT3.
PET Interpretation
Hypometabolism: Area of decreased FDG uptake
Hypermetabolism: rare and correlate with EEG.
16. PET in oncology
Imaging of gliomas by means of MRI and PET to demarcate
biologically active tumour tissue
17. Brain in oncology in oncology
PET PET
low- and high-grade gliomas,
GRADE
uptake ratio
pathology
0
no uptake ---------grade I or II
1 Tumor <normal white
matter ---------------- --- ~
2 Tumor >white matter ,<
normal cortex ----------grade III or IV
3 Tumor>normal cortex--- ~
18. Brain PET in oncology
RECURRENCE
VS
RADIATION NECROSIS,
21. Dementia
- Definition
Dementia is a clinical syndrome characterized by
acquired losses of cognitive and emotional abilities
severe enough to interfere with daily functioning.
22. Dementia in Alzheimer's disease
Vascular dementia
Dementia in other diseases classified elsewhere
Fronto temporal lobe D
Lewy body disease
Dementia in Huntington's disease
Dementia in Parkinson's disease
Dementia in [HIV] disease
Dementia in other specified diseases
Unspecified dementia
23. THESE DIAGNOSTIC INDICATIONS FOR
BRAIN PET:
accompanied by pre-test considerations ,supporting
clinical data and prerequisite information:
1----REFRACTORY SEIZURES/EPILEPSY
2----FRONTO-TEMPORAL LOBE DEMENTIA AND
ALZHEIMER’S DISEASE
24. AIM’s CRITERIA TO DETERMINE
IF FDG-PET DEMENTIA EVALUATION IS INDICATED
The use of FDG-PET scan in the diagnosis of Alzheimer’s
disease (AD) and Fronto-Temporal Lobe Dementia(FTD)
is Approved provided
The patient’s clinical symptoms meet the diagnostic
criteria for (AD), (FTD)
a comprehensive clinical evaluation which has
included:comprehensive medical history,physical and
mental status exam
neuropsychological testing, laboratory testing, and
structural imaging ---MRI or CT----to aid in identifying
structural, metabolic, and chemical abnormalities as a
cause for cognitive impairment.
25. Then We Do PET SCAN for dementia
PET Characteristics
Association Cortex Hypometabolism: posterior
parietal, temporal, anterior occipital
Preservation of Primary Sensory Motor Cortex,
visual Cortex, Cerebellum
Hypometabolism in Posterior Cingulate Gyrus
Bilateral But Can be Asymmetric
26. Alzheimer's dementia(Case 1)
severely reduced FDG activity ---in the bilateral parietal, temporal lobe and
frontal lobe. The primary sensorimotor cortex, visual cortex, basal ganglia,
thalamus and cerebellum are normal and spared
27. Alzheimer's
dementia (Case 2)
an area of
reduced FDG activity
10-50% seen in the
bilateral
parietal, temporal
lobes.
FDG uptake in the rest
of the cerebral
cortex, subcortical gray
matter, cerebellum is
within normal range.
33. DEMENTIAS------------- Diffuse Lewy body disease
after Alzheimer's disease, the second most common
cause of senile degenerative dementia
It is characterized histologically by the occurrence of
Lewy bodies in allocortical, neocortical and
subcortical structures.
34. DEMENTIAS----Lewy body disease
FDG-PET -- diffuse cerebral hypometabolism
with marked declines in association cortices
with relative sparing of subcortical structures and
primary somatomotor cortex, a pattern reported
previously in Alzheimer's disease.
Unlike Alzheimer's disease___~ also demonstrates
hypometabolism in the occipital association cortex
and primary visual cortex.
37. PARKINSONS DISEASE
PET scans are FDA-approved for the diagnosis of
dementia, but not for the diagnosis of Parkinson’s
disease.
In cases where the expert is not sure of the diagnosis
– is it essential tremor or Parkinson’s,
or where a potentially risky procedure is being
considered (e.g. deep brain stimulation surgery), it is
reasonable to recommend a PETscan or DaTscan.
38. DaTscan (Ioflupane I 123 injection, also known as
phenyltropane)
-------------a radiopharmaceutical agent which is
injected into a patient’s veins in SPECT imaging.
-----------contains a dopamine transporter radioligand
-----------used to assess striatal uptake
39. An example DaTscan; demonstrates essential tremor on the left (normal DaT), and
a parkinsonian syndrome on the right (decreased DaT). DaT/SPECT scans focus
on the activity of the dopamine transporter
40. PARKINSONS DISEASE (PET scan)
Parkinson's disease
decreased activity in the left caudate and putamen ;;;relatively symmetric thalamic FDG uptake
FDG uptake in the rest of the cerebral cortex, subcortical gray matter, cerebellum is within
normal range.
41. a PET scan ;top : a normal scan.
middle :abnormalities in the putamen (red uptake in the figure)
lower :a return to an almost normal scan following the introduction of levodopa.
42. A(SPECT) brain perfusion scan(Huntington's
disease).
Areas of highest tracer uptake --white/orange
(high blood flow);
lowest uptake -- blue/black (low blood flow).
markedly reduced uptake in the caudate nuclei
bilaterally (outlined by white dashed lines).
The adjacent thalami are normal. Activity in
the cortex is essentially normal. High activity
in the visual cortex is secondary to visual
stimulation the patient received in the partially
darkened room.
43. PET------- for Epilepsy
Surgery for Epilepsy
1. Surgery is indicated for refractory focal epilepsy.
2. PET is indicated only for pre-surgical evaluation,
not for diagnosis.
44. SUBTRACTION ICTAL SPECT SCAN
: During a seizure, the region where the seizure started
has the greatest amount of blood flow.
the patient is injected with a tracer that helps to measure
blood flow. The injection is most helpful when it is given
within 20 seconds of when the seizure started.
A SPECT scan is then done within two-three hours and
the brain region(s) with greatest blood flow are
identified. Although this scan is done hours after the
tracer is injected, an accurate image of blood flow during
the seizure (ictal) is obtained since the tracer remains in
the brain for up to four hours.
45. Another SPECT (inter-ictal) scan is done at another
time when the patient is not having a seizure (interictal).
The two scans are digitally subtracted and the
resulting image provides valuable information about
where the seizures begin.
46. This test is most valuable in patients with
1) an abnormal MRI and an EEG that does show the
area of seizures onset or shows a different area of
seizure onset than the MRI abnormality;
2) patients with a normal EEG with or without an
EEG that identifies the area that of seizuresonset.
In this figure, the region(s) in bright orange
represent the area where this patient's seizures begin
(the left temporal lobe).
52. SPECT
A Single Photon Emission Computed Tomography
(SPECT) scan is a type of nuclear imaging test that
shows how blood flows to tissues and organs.
The test differs from a PET scan in that the tracer
stays in your blood stream rather than being
absorbed by surrounding tissues, thereby limiting
the images to areas where blood flows. SPECT scans
are cheaper and more readily available than higher
resolution PET scans.
53. SPECT imaging in cerebrovascular disease
Measurement of regional cerebral blood flow (rCBF)
Diagnosis and prognosis of cerebro-vascular disease
SPECT: superior to CT/MRI in detecting cerebral
ischemia—
rCBF imaging: effective in acute phase, less sensitive
in the subacute phase
-8h: SPECT-80%; CT-20%
-72h: SPECT=CT/MRI
False negative: lacunar infarctions, luxury
perfusion(2~28 days)
54. radiopharmaceuticals
REGIONAL CEREBRAL BLOOD FLOW IMAGING
Inert gases are effective markers---LIKE
breathing of carbon monoxide (C-11 and O-15), which concentrates
in RBCs
Xe-133 inhalation / injection into ICA / IV injection after dissolution
in saline
BUT
Tc-99m HMPAO brain SPECT(high extraction efficiency by brain
tissue)
55. r CBF imaging( HMPAO technique)
requires no patient preparation.
typical activity of 500 MBq is injected intravenously.
patient in a quiet stable environment.
Images obtained from 20 min to several hours after
injection because the tracer distribution in the brain
is stable during this time.
Volumetric data are displayed in standardised
axial.coronal and sagittal planes, and colour displays
are used .
58. Massive infarction of the right middle cerebral artery territory. Note severe
ischaemia of the Frontal, temporal and parietal cortex and also of the basal ganglia
on right.------99m Tc—HMPAO brain SPECT
59. 99 Tc-exametazime brain SPECT: axial, coronal and right
parasagittal images showing very extensive perfusion deficits during the
acute ischaemic phase (top row) and substantial improvement several
months later after clinical recovery (bottom row).
60. (PET) scan of the brain of a stroke
patient. Colour- coding is:
high brain activity (yellow, red);
low activity (blue to black).
At upper right is a lesion (blue)
showing an area of brain damage
with reduced blood flow and low
activity due to stroke.
61. Brain stress test: vasodilatory response to CO2 or
acetazolamide
--compare resting images and vasodilated images
(20~30min after acetazolamide injection)
--diseased or at-risk areas show little or no
response
Normally ,there shud b 40%increase over resting flow.
62. PET Brain Scan - Benefits
Pinpointing brain abnormalities and whether these abnormalities are caused by:
Alzheimer's disease, blood flow shortages, depression, or some other reason
Assisting surgery for individuals with uncontrollable seizures by localizing the brain
site of seizure activity
Analyzing muscle tremor and evaluate whether it this is caused by Parkinson's
disease or some other movement disorder
Evaluating brain tumors and determine whether they are benign (alive tissue and
non-cancerous) or malignant (dead tissue and cancerous)
Assessing such medical conditions as degenerative brain diseases, movement
disorders, and dementias
Assisting surgical operations by identifying the areas of the brain responsible for
such critical functions as movement and speech
Analyzing the effectiveness of chemotherapy by examining cites of possible cancer
recurrence and distinguishing whether this structural change is due to tumor regrowth or is a form of scar tissue
Diagnosing Alzheimer’s earlier
Differentiating Alzheimer’s disease from other types of dementia
Monitoring the progression of the disease and the effectiveness of the treatment
DaT scans use a substance that "tags" a part of a neuron in the brain where dopamine attaches to it, showing the density of healthy dopamine neurons. Thus, the more of the picture that "lights up", the more surviving brain cells.
