What a DaT scan does and why doctors use it for Lewy body dementia

A DaT scan (dopamine transporter scan) is a brain imaging test that helps doctors see whether you have lost dopamine-producing nerve cells in a specific part of your brain. Lewy body dementia damages these cells, so a DaT scan can show a pattern that matches the disease. The scan does not diagnose Lewy body dementia by itself — your doctor will combine the DaT scan result with your symptoms, medical history, and sometimes other tests — but it is one of the most useful tools for telling Lewy body dementia apart from Alzheimer's disease or Parkinson's disease, which can look similar at first.

The scan works by injecting a small amount of radioactive tracer into your bloodstream. This tracer attaches to dopamine transporters in your brain. A camera then takes pictures to show where the tracer collects. In a healthy brain, the tracer spreads evenly. In Lewy body dementia, the tracer shows a pattern of loss in the striatum, a region deep in the brain that controls movement and motivation.

Key Takeaways

  • A DaT scan shows whether dopamine-producing cells in your brain have been damaged, which is a hallmark of Lewy body dementia.
  • The scan involves a small injection of radioactive tracer and takes about 15 to 20 minutes, with results available within a few days.
  • A DaT scan is most useful when combined with your symptoms and other test results, not as a standalone diagnosis.
  • Insurance often covers a DaT scan when a doctor orders it to rule out other types of dementia, though you should check your plan's requirements.

How the DaT scan procedure works

The scan takes place in a hospital or imaging center. A technician injects the radioactive tracer into a vein in your arm. You then wait about three to four hours while the tracer travels through your bloodstream and binds to dopamine transporters in your brain. During this waiting period, you can usually leave the imaging center and return when it is time for the scan.

When you return, you lie still on a table while a gamma camera rotates around your head, taking pictures from different angles. The scan itself lasts 15 to 20 minutes. You will not feel anything during the imaging. The radioactive tracer is very small in dose and leaves your body naturally within a few days. Your doctor receives the images within a few days and reviews them to look for the pattern of dopamine loss that suggests Lewy body dementia.

What the results mean

A normal DaT scan shows even distribution of the tracer throughout the striatum. An abnormal result shows reduced tracer uptake, meaning fewer dopamine transporters are present — a sign that dopamine-producing cells have been damaged or lost. This pattern is consistent with Lewy body dementia, Parkinson's disease, or Parkinson's disease dementia.

An abnormal DaT scan does not prove you have Lewy body dementia on its own. Your doctor will look at when your symptoms started, what those symptoms are, and how they have progressed. Lewy body dementia typically begins with visual hallucinations or movement problems, while Alzheimer's usually starts with memory loss. Your doctor may also order other tests, such as an MRI or PET scan, to rule out other causes. Together, the DaT scan and your clinical picture help your doctor narrow down the diagnosis.

When doctors order a DaT scan

Your doctor may recommend a DaT scan if your symptoms suggest Lewy body dementia but could also fit Alzheimer's disease or Parkinson's disease. Common reasons include visual hallucinations early in the disease, movement problems like stiffness or tremor alongside memory loss, or confusion about which type of dementia you have. The scan is particularly useful when your symptoms are mixed or when the diagnosis is unclear after an initial evaluation.

A DaT scan is not routine for everyone with dementia. If your symptoms clearly point to Alzheimer's disease — such as gradual memory loss without hallucinations or movement problems — your doctor may not order one. However, if there is any doubt, a DaT scan can provide concrete information that helps guide treatment and planning.

Cost and insurance coverage

The cost of a DaT scan varies by location and imaging center, ranging from several hundred to over a thousand dollars. Most insurance plans, including Medicare, cover a DaT scan when a doctor orders it to help diagnose or rule out Lewy body dementia or Parkinson's disease. You will need a doctor's order and a medical reason for the scan. Some plans require prior authorization, meaning your doctor must get approval from the insurance company before the scan is scheduled.

If you do not have insurance or your plan does not cover the scan, ask the imaging center about their cash-pay rates or whether they offer payment plans. Some centers offer discounts for uninsured patients. Before scheduling, call your insurance company or check your plan documents to understand what you will owe.

Limitations of the DaT scan

A DaT scan shows dopamine loss, but dopamine loss alone does not equal a diagnosis. Parkinson's disease and Parkinson's disease dementia also show dopamine loss on a DaT scan, so the result must be interpreted alongside your symptoms and timeline. Additionally, a normal DaT scan does not rule out Lewy body dementia completely, though it makes the diagnosis less likely. Some people with Lewy body dementia may have a borderline or mildly abnormal scan.

The scan also exposes you to a small amount of radiation, though the dose is considered safe for diagnostic purposes. Pregnant women should not have a DaT scan. If you are pregnant or think you might be, tell your doctor and the imaging center before the procedure.

What happens after the scan

Your doctor will review the images and discuss the results with you, usually within a week. If the scan shows dopamine loss and your symptoms fit Lewy body dementia, your doctor may begin treatment to manage your symptoms. Medications for Lewy body dementia differ from those for Alzheimer's, so an accurate diagnosis shapes your care plan. Your doctor will also discuss what to expect as the disease progresses and may refer you to a neurologist or dementia specialist if they have not already.

If the scan is normal or shows a different pattern, your doctor will explore other diagnoses or may order additional tests. A single test rarely answers all questions, so be prepared for your doctor to recommend follow-up imaging or specialist evaluation if needed.

Frequently Asked Questions

Is a DaT scan safe?

Yes. The radioactive tracer used in a DaT scan is a very small dose and is designed to be safe for diagnostic imaging. The radiation exposure is comparable to a standard CT scan. The tracer leaves your body naturally within a few days. Pregnant women should not have the scan, and you should tell your doctor if you are breastfeeding.

Can a DaT scan diagnose Lewy body dementia on its own?

No. A DaT scan shows dopamine loss, which is consistent with Lewy body dementia, but it cannot diagnose the disease by itself. Your doctor combines the scan result with your symptoms, how the disease has progressed, and sometimes other tests to reach a diagnosis. A normal scan does not rule out Lewy body dementia, and an abnormal scan could also fit Parkinson's disease.

How long does it take to get results?

The scan itself takes 15 to 20 minutes, but you will wait three to four hours between the injection and the imaging. Your doctor typically receives the images within a few days and will discuss the results with you within a week.

What if my insurance does not cover the scan?

Ask your doctor to submit a prior authorization request to your insurance company, explaining the medical reason for the scan. If your plan still denies coverage, ask the imaging center about cash-pay rates or payment plans. Some centers offer discounts for uninsured patients.

Will a DaT scan change my treatment?

Yes, if it helps confirm Lewy body dementia. Treatment for Lewy body dementia differs from Alzheimer's treatment, so an accurate diagnosis allows your doctor to prescribe medications and strategies that work better for your specific condition. The scan can also help your doctor explain your diagnosis to you and your family.