Neuro Nuclear Medicine

General Neuro Nuclear Med

• Brain

  • 3 Major types of imaging

    • Planar

      • Uses perfusion agents

      • Really only brain death studies fall under this category

      • 2 phases

        • Dynamic/Angiographic phase —>many rapidly acquired of the arrival of the tracer —> shows brain perfusion basically

          • Done 2-3 sec after administration

        • Delyaed static phase —> show distribution of tracer and can make note of place it is (and should not be) or should be (and is absent)

          • Done 15 min after administration

    • SPECT brain perfusion imaging

      • Uses lipophilic agents that can cross BBB —> can enter brain tissue in same proportion as normal blood supply to area would

    • PET

Brain Death Study

• Form of planar imaging

• Radiotracers used

  • Tc-99m - DTPA OR Tc-99m-pertechnetate —> Transient perfusion agent —> preferred agents to be used for brain death study

    • If you see some faint tracer over what looks like the brain, it is not actually uptake in the brain because it cannot cross the BBB, it is actually uptake in the scalp which is projected over the brain

      • Can put a rubber band around the scalp to pinch off blood supply to it is not mistaken for brain activity

    • Tc-99m pertechnetate only —> choroid plexus will normally have tracer uptake

  • Tc-99m - HMPAO —> Perfusion agent extracted by brain on first pass —> not typically used

• Trident sign

  • Should see a 3 pronged structure shortly after administration of tracer —> Middle cerebral artery + both MCAs

• Positive study

  • Tracer uptake in carotids up to skull base and then none after due to compression from cerebral edema

  • NOTE: Need to evaluate that there is tracer uptake in the common carotid to show that a good bolus was given

    • If there is not significant tracer uptake in the common carotids then the bolus was likely shit and study needs to be redone

  • Hot nose sign —> basically maxillary branch of external carotid artery is still patent and supplies the face which may be hot, can still be brain dead with this

Brain SPECT

• Agents

  • Uses lipophilic agents that can readily cross the BBB and be retained by brain parenchyma in proportion to their cerebral blood flow

  • Tc-99m-HMPAO

    • Uptake and metabolism is highest in gray matter

    • Uptake is proportional to cerebral blood flow

    • Excretion through intestines & kidneys

  • Tc-99m- ECD

• Technique

  • Tracer injected IV

Seizures

Seizure Studies

• Ictal & Inter-ictal

• Ictal studies

  • Done while having the seizure

  • Use Tc-99m-HMPAO or Tc-99m-ECD

  • Ictal is more sensitive that inter-ictal

CSF Leak Study

• Intrathecal administration of In-111 DTPA

• Nasal pledget placement

• Serum blood draws are obtained at intervals determined by the radiologist

  • At the same time that the blood is drawn the nasal pledget counts are also obtained

• Serum blood is counted so that you can get a ratio of the nasal pledget to serum pledget

• CSF pledget to serum ration of 1.5+ = positive test

Imaging

• Prep for SPECT in suspected dementia

  • Ensure patient is in a dimly lit and quiet room

  • Patient is not to speak or read

  • You are not to interact with the patient before, during or 5 min after the procedure

  • They can have eyes open tho…idk it was a question

• 3 types of PET that can be used in dementia evaluation

  • FDG

    • Hypometabolism in fucked up areas

  • Amyloid

    • Diffuse uptake in abnormal cases

  • Tau

    • Deposition where there is atrophy

FDG PET

• 1 = normal

• 2 = Bilateral parietal lobe decreased uptake

• 3 = Bilateral frontal and temporal lobe decreased uptake

• 4 = Alzheimer pattern + occipital lobe involvement

Fronto-temporal dementia

• MRI will show atrophy of

  • Frontal lobe

  • Temporal lobes

  • Anterior cingulate gyrus

• FDG PET Hypometabolic Areas

  • Same 3 as above

• Negative amyloid PET

Dementia

I-123 loflupane study

• Used to assess for parkinson’s and adjacent shit which appears to almost walways be progressive supranuclear palsy and multiple system atrophy

• Appears to be used when there is a tremor and want to see if from parkinson’s or some other shit

• I-123

  • Decay by electron capture

  • T1/2 = 13 hours

  • 159 keV

  • Dose = 5 mCi

  • Has high affinity for dopamine transporters (DAT), typically in striatum region

• Normal study = bilateral comma shaped shit in putamen region (pic to right)

Parkinson’s Disease

• I-123 loflupane study