The DaTscan is a specialized nuclear medicine procedure used to evaluate the integrity of the dopamine system in the brain, primarily to help differentiate between essential tremor and tremors caused by parkinsonian syndromes. This imaging test utilizes a small amount of a radioactive tracer, Ioflupane I 123, which temporarily binds to dopamine transporters. The total time commitment for a patient undergoing a DaTscan is not a single continuous block, but is instead divided into a brief injection phase, an extended period of passive waiting, and a relatively short imaging session. This structure means the overall appointment can span several hours, with most of that time dedicated to waiting for the tracer to distribute correctly.
Required Preparation Steps
Preparation for a DaTscan begins well before the appointment date, focusing mainly on managing medications that could interfere with the tracer’s ability to bind to the dopamine transporters in the brain. Certain drugs, including some antidepressants, stimulants used for ADHD, and specific anti-nausea medications, must often be stopped for a period equivalent to at least five half-lives of the medication. This temporary cessation ensures that the dopamine transporters are free to bind the Ioflupane I 123 tracer. The decision to halt any medication is a significant medical consideration that must be made by the prescribing physician, weighing the benefits of the scan against the risks of stopping treatment.
Another important preparation step is the administration of a thyroid-blocking agent, which is generally taken at least one hour before the tracer injection. The radiotracer contains a small amount of free iodine-123, and the blocking agent prevents the thyroid gland from accumulating this radioactive iodine. This step reduces the overall radiation dose to the thyroid. Patients are also typically advised to maintain adequate hydration before and after the procedure to help the body clear the tracer quickly.
The Uptake Phase
Upon arriving at the facility, the Ioflupane I 123 tracer is administered intravenously, marking the beginning of the uptake phase. This phase is the longest component of the patient’s time commitment on the day of the scan. The tracer must circulate through the bloodstream and cross the blood-brain barrier to reach and bind to the dopamine transporters in the striatum, the area of the brain being visualized.
A mandatory waiting period is required for this binding process to occur and for any excess tracer to clear from the surrounding brain tissue and blood vessels. This uptake phase typically lasts between three and six hours from the time of injection until the imaging can begin. The exact timing within this range depends on the specific protocol used by the nuclear medicine facility and the need for optimal clearance.
During this extended waiting time, the patient is generally free to move around, read, or relax, though they are usually asked to remain at the facility or nearby. This passive period is necessary for the tracer to distribute and clear, ensuring the final images accurately reflect the concentration of dopamine transporters.
The Imaging Procedure
Following the lengthy uptake phase, the patient proceeds to the imaging room for the actual scanning session, which involves a Single-Photon Emission Computed Tomography (SPECT) machine. The patient is positioned lying on a table while a specialized gamma camera detects the gamma rays emitted by the I-123 tracer accumulated in the brain, constructing detailed tomographic images.
The duration of the active imaging procedure is relatively short compared to the total appointment time, typically lasting between 30 and 45 minutes. During this time, the camera rotates around the patient’s head to collect data from multiple angles. It is important for the patient to remain completely motionless throughout the entire acquisition period to prevent blurring or artifacts in the resulting images.
If the patient moves significantly, the technologist may need to halt the scan or utilize motion correction software, but substantial movement often necessitates repeating the entire imaging sequence. To help minimize movement, the patient’s head is sometimes secured with gentle restraints or tape.
Total Appointment Duration and Variables
When combining all phases, a patient should expect the total time commitment for a DaTscan appointment to fall within a range of approximately four to six hours from check-in to departure. This timeline includes several smaller, non-imaging components that contribute to the overall duration. The initial process, including check-in, consent review, and establishing intravenous access for the tracer injection, can take 30 to 60 minutes.
The longest segment remains the three-to-six-hour uptake phase, which is the non-negotiable waiting period required for the tracer to bind effectively. Once the 30- to 45-minute SPECT imaging is complete, the patient is still not immediately discharged. A technologist or radiologist must perform an initial quality check on the images to ensure they are clear and adequate for diagnostic interpretation.
Several variables can extend the total duration beyond the anticipated six hours. Facility scheduling delays are common, especially if the radiotracer’s arrival is delayed, as it is a short-lived radioactive material that must be used within a specific time frame. Patient-related factors, such as the need for anti-anxiety medication or the inability to remain still during the imaging, may necessitate a longer scanning time or even a complete rescan. If initial images are suboptimal due to patient movement, acquiring a second set of images can add another 30 to 45 minutes to the total time.