DAT Scan

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A DaT Scan is a nuclear medical imaging technique used to assess dopaminergic reuptake within the brain. The more accurate name is 123I-isofluane-SPECT (single photon emission computed tomography) as DaTScan is actually the trade name of the manufacturer (General Electric).
The scan involves injecion of an intravenous radio-labelled ligand of the presynaptic dopamine amine transporter (DaT) followed by a SPECT using a gamma-camera, thereby evaluating the amount of presynaptic dopamine transporters in the striatum. These transporters are under-expressed in certain neurodegenertaive conditions particularly those that involve neurodegeneration in the substantia nigra, the site of the cell bodies of the dopamine-releasing neuron.
It can be used to support the diagnosis of dopaminergic deficiency seen in Parkinson's Disease or Lewy Body dementia, as well as to help differentiate 'true' Parkinson's Disease from drug-induced Parkinsonism, vascular Parkinsonism and other causes of Parkinsonism.

The degree of abnormality on the DaT scan is often correlated with the clinical degree of disability; however there are cases where there is marked discrepancy between DaT-scan abnormalities and clinical severity:
- Parkinson's Disease caused by mutations in the Parkin gene often have devastating appearances on the scan but often mild clinical signs.
- "Scans Without Evidence of Dopaminergic deficit" (SWEDD) have been described in a significant proportion of patients with a clinical diagnosis of Parkinson's Disease.