PET Application In Psycology


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PET Application In Psycology

  1. 1. PET Application in Psychiatry Ramin V. Parsey and J. John Mann By Dan Diner
  2. 2. PET <ul><li>nuclear medical imaging technique </li></ul><ul><li>Produces 3D images(maps) of functional processes in the body </li></ul><ul><li>Scientists inject short half-life radioactive isotopes(tracers) into body, then detect gamma rays </li></ul>
  3. 3. <ul><li>isotope goes through positron decay </li></ul><ul><li>emits a positron(antimatter of electron) </li></ul><ul><li>Travels a few mm and annihilates with an electron, producing gamma photons moving in opposite directions* </li></ul><ul><li>The annihilation is detected by the scintillator material in the scanning device, which sends off a burst of light that is caught by the photomultiplier tubes </li></ul>
  4. 4. [ 15 O]-Water <ul><li>Half-life of 2 minutes </li></ul><ul><li>Used to image blood flow </li></ul><ul><li>Use of it also indicated pre-frontal cortex deficit in depression </li></ul>
  5. 5. 18 F-FDG (fluoro-2-deoxyglucose) <ul><li>used for the assessment of glucose activity in brain (and heart). Used for finding tumors. </li></ul><ul><li>Patients fast 6 hours beforehand </li></ul><ul><li>After injection, patient waits 1 hour </li></ul><ul><li>Taken in by tissues with high metabolic activities- such as tumors </li></ul><ul><li>High for tumors because not they don’t listen to body. Grow out of control. More Cells. </li></ul><ul><li>Patient does keeps physical activity to a minimum so as to minimize uptake of radioactive chemicals into muscles </li></ul>
  6. 6. <ul><li>Neuroimaging studies generally agree that mood disorders link with functional deficits but disagreed about structal deficits: </li></ul><ul><li>Study with depressed patients found 11/12 had low regional cerebral metabolic rate of glucose </li></ul><ul><li>Other studies studies claim that differences in key brain region volumes play roles in mood disorders </li></ul>
  7. 7. Serotonin <ul><li>Neurotransmitter in CNS </li></ul><ul><li>Regulates anger, sleep, body temperature, aggression, mood, appetite, vomiting, and sexuality </li></ul><ul><li>Deficits in Serotonin are associated with extreme mood disorders, such as Obsessive Compulsive Disorder, bipolar disorder, and clinical depression </li></ul>
  8. 8. Cont. <ul><li>Abnormal 5-HT transmission is thought to cause major depression </li></ul><ul><li>In postmortem studies, less serotonin transorter binding was found throughout the dorsal(upper)-ventral extent of the prefrontal cortex and in the brainstem of people with episodes of major depression </li></ul><ul><li>Found lower 5-HT transporter binding in midbrain, amygdala, and ventral striatum, but not the thalamus </li></ul>
  9. 9. <ul><li>The lab found that depressed people's prefrontal cortex responds poorly to forced brain activity using serotonin </li></ul><ul><li>this suggests that pre-frontal cortex might be malfunctioning in depressed people </li></ul><ul><li>Fenfluramine(drug) was used as the challenge. It is supposed to activate brain activity everywhere in the brain </li></ul>
  10. 10. Why? <ul><li>Hypotheses: </li></ul><ul><li>Low 5-HT transporter binding could be due to a functional change in the distribution of transporters </li></ul><ul><li>few serotonin nerve terminals due to fewer 5-HT neurons </li></ul><ul><li>Fewer terminals or fewer transporters per terminals </li></ul>
  11. 11. <ul><li>This is a PET McNeil scan result. </li></ul><ul><li>McNeil binds to the serotonin </li></ul><ul><li>transporter </li></ul><ul><li>(A) is an MRI </li></ul><ul><li>(B) is a healthy person pet scan </li></ul><ul><li>(C) is a depressed person </li></ul><ul><li>Notice that regions in a depressed person have much less serotonin transporter </li></ul><ul><li>This suggests that the serotonin system is different between healthy and depressed people. Future drugs could be made to stabilize this system. </li></ul>
  12. 12. Schizophrenia <ul><li>Mental disorder characterized by an impaired perception of reality </li></ul><ul><li>Often patients have hallucinogens </li></ul><ul><li>Hypothesized to be caused by abnormal Dopamine levels </li></ul><ul><li>PET scan is often used to understand why </li></ul>
  13. 13. Dopamine System in Schizophrenia <ul><li>Dopamine- a neurotransmitter released by the hypothalamus that is also used as a medication that increases heart rate and blood pressure </li></ul><ul><li>Studies using [ 11 C]-raclopride showed no result in D2 receptor binding abnormalities </li></ul><ul><li>but studies using [ 11 C]-N-methyl-spiper-one showed that schizophrenics tended to have more D2 receptor binding </li></ul><ul><li>[ 11 C]-raclopride have been used for same general purpose, and showed that decrease in [ 11 C]-raclopride binding was proportional to amount of dopamine released </li></ul>
  14. 15. Psychotropic Drug Development <ul><li>[ 11 C]-raclopride has been used to show that typical/classical antipsychotics (e.g. haloperidol) block over 70-80% of D2 receptors at doses with therapeutic effects. Atypical/newer generation antipsychotic block <70%. Atypical antidepressants produce much less side effects. </li></ul>
  15. 16. Cont. <ul><li>Antidepressants that enhance serotonin function(such as SSRI’s(Selective serotonin reuptake inhibitors)) have a therapeutic effects that evolve for weeks </li></ul><ul><li>SSRI prevents neurotransmitter from going back to the pre-synaptic neuron(reuptake) </li></ul>
  16. 17. END