A DaTscan, or Dopamine Transporter Scan, is a specialized diagnostic imaging test. It provides objective information about the brain’s dopamine system by visualizing specific structures. This helps medical professionals assess the health of nerve cells and evaluate various neurological conditions.
How the DaTscan Works
The DaTscan operates on the principle of detecting dopamine transporters (DATs). It uses a radioactive tracer called Ioflupane I 123 Injection. This tracer binds specifically to DATs on dopamine-producing neurons in a brain region called the striatum.
Once administered, the tracer travels to the brain and attaches to these transporters. Dopamine transporters are proteins on nerve cells responsible for reabsorbing dopamine from the space between neurons, regulating its levels. The amount of tracer that binds reflects the density of these transporters. A SPECT scanner (Single-Photon Emission Computed Tomography) then detects the gamma rays emitted by the radioactive iodine in the tracer. These signals are converted into images that show the distribution and concentration of DATs in the striatum.
Why It’s Used for Parkinson’s
The DaTscan plays a role in evaluating symptoms that could be related to Parkinson’s disease because the condition involves the degeneration of dopamine-producing neurons. This degeneration leads to a reduction in the number of dopamine transporters in the striatum. By visualizing the density of DATs, the scan can provide evidence of this neuronal loss.
The scan is particularly useful for differentiating Parkinson’s disease from other conditions that might have similar symptoms, such as essential tremor or drug-induced parkinsonism. In essential tremor, for example, the dopamine neurons are generally unaffected, so a DaTscan would typically show normal results. Conversely, in Parkinson’s disease, the scan would reveal a reduction in DATs, helping to support a diagnosis. While it confirms the presence of dopamine neuron loss, the DaTscan cannot distinguish between Parkinson’s disease and other atypical parkinsonian syndromes like multiple system atrophy or progressive supranuclear palsy, as these also involve DAT loss.
What to Expect During the Scan
Undergoing a DaTscan involves several steps, usually completed within a few hours. Before the radioactive tracer is injected, patients typically receive an oral medication, such as potassium iodide, to protect the thyroid gland from absorbing the radioactive iodine. This is usually given about an hour before the main injection.
Following this preparation, the Ioflupane I 123 tracer is administered intravenously, often into a vein in the arm. A waiting period of approximately three to six hours then follows, allowing the tracer to travel through the bloodstream and adequately bind to the dopamine transporters in the brain. During this waiting time, patients may be able to leave the facility. The actual scanning process takes about 30 to 45 minutes, during which the patient lies still on a table, and a SPECT camera rotates around their head to capture images.
Interpreting Scan Results
Interpreting DaTscan images involves assessing the pattern and intensity of the tracer’s uptake in the striatum. A normal scan typically shows two symmetrical, comma-shaped areas of tracer uptake in both sides of the striatum. These “commas” indicate a healthy density of dopamine transporters.
In contrast, an abnormal DaTscan, which suggests a loss of dopamine neurons, will often show reduced or asymmetrical uptake. This can appear as a less distinct, more rounded, or “period-shaped” pattern, particularly in the putamen part of the striatum. Such findings are consistent with Parkinsonian syndromes. The DaTscan is a diagnostic aid, and its results are interpreted by a medical professional in conjunction with a patient’s clinical symptoms, neurological examination, and other relevant medical information.