Radionucleide imaging of the brain


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  • 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.
  • Radionucleide imaging of the brain

    2. 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.
    3. 3.  Radionuclide angiography  PET/SPECT  Radionuclide cisternography
    4. 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. 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. 6. Image of a typical positron emission tomography (PET) facility
    7. 7. PET/CT-System with 16-slice CT; the ceiling mounted device is an injection pump for CT contrast agent
    8. 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. 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. 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
    11. 11. B-Non oncologic Indications (PET) 1. 2. 3. 4. 5. 6. Refractory epilepsy-- pre-surgical evaluation. Alzheimer disease. Dementia differential diagnosis. Parkinson disease. Huntington disease, senile chorea Schizophrenia Stroke, cerebral vasospasm.
    12. 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. 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. 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. 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. 16. PET in oncology Imaging of gliomas by means of MRI and PET to demarcate biologically active tumour tissue
    17. 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. 18. Brain PET in oncology RECURRENCE VS RADIATION NECROSIS,
    19. 19. Brain PET To distinguish functionally important brain areas
    20. 20. B-Non oncologic Applications(PET)
    21. 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. 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. 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. 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. 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. 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. 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.
    28. 28. Alzheimer's dementia (Case 3)
    29. 29. 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.
    30. 30. 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.
    31. 31. LEWY BODY DISEASE-----diffuse cerebral hypometabolism Occipital cortex is also affected(difference from AD)
    32. 32. Frontotemporal dementia There is mild-moderate hypometabolism involving both frontal and contiguous temporal lobes. The brain otherwise has normal symmetric metabolism without focal abnormality. FRONTO TEMPORAL LOBE DEMENTIA.
    33. 33. 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.
    34. 34.  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
    35. 35. 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
    36. 36. 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.
    37. 37. 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.
    38. 38. 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.
    39. 39. 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.
    40. 40. 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.
    41. 41.  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.
    42. 42.  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).
    43. 43. PET------- in Epilepsy abnormally high activation of the left part of the brain of a patient during an epileptic seizure
    44. 44. PET------- in Epilepsy
    45. 45.  Epilepsy - lesional  Mesial Temporal Sclerosis (MTS)  MRI: Atrophy, enlarged temporal horn. Increased T2 signal. Bilateral changes in 10%.   PET: Hypometabolism Pathology: Neuronal Loss, Gliosis.
    46. 46. Mesial Temporal Sclerosis (MTS)
    47. 47. 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.
    48. 48. 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)
    49. 49. 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)
    50. 50. 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 .
    51. 51. r CBF imaging(interpretation) Normal tracer uptake Abnormal tracer uptake  Symmetric distribution  Absent  Higher radioactivity: gray matter, basal ganglion, occipital cortex, cerebellum  Lower radioactivity: white matter, ventricles infarction, trauma, surgical resection  Reduced ischemia, dementia, depression, seizure(interictal)  Increased luxury perfusion, seizure(ictal)
    52. 52. r CBF imaging SPECT imaging
    53. 53. 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
    54. 54. 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).
    55. 55. (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.
    56. 56.  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.
    57. 57. 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
    58. 58. THANK YOU