PET Application In Psycology
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PET Application In Psycology



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PET Application In Psycology PET Application In Psycology Presentation Transcript

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