DOPA Test: Definition, Procedure & Uses

A specialised nuclear medicine imaging test that gives information on certain biological processes in the body is called the DOPA test, or F-DOPA PET scan / DOPA PET scan. It's based on a radioactive compound called fluorine-18 fluorodopa (18F-FDOPA) that's associated with dopamine metabolism. The scan can yield functional data that won't be found through conventional imaging. Specialized nuclear medicine imaging can, at Molecular Diagnostics and Therapy, enable physicians to use sophisticated imaging and diagnostic methods to assess various health conditions. Performing a DOPA PET scan will be determined by a patient's symptoms, medical history and clinical question being evaluated.

What Is a DOPA PET Scan?

A DOPA PET scan is a type of PET scan that uses an 18F-FDOPA radiotracer. Once given to the patient, the tracer is detected by the PET scanner, providing images of related biological activity. F-DOPA relates more specifically to pathways in the brain involving dopamine. F-18-DOPA PET could be used in a subset of neurological patients to evaluate dopamine activity and help evaluate Parkinsonian disorders. Depending on the disease and the purpose of the scan, applications of DOPA PET may be for the evaluation of selected neuroendocrine and brain tumors.

Why Is a DOPA Test Done?

There are several primary uses for DOPA PET scans, depending on the region being studied and the suspected condition. It can also be used in neurological imaging for the evaluation of the pathways involved in the production of dopamine and may assist in differentiating some other conditions with similar symptoms from the Parkinsonian syndromes.

F-DOPA PET can give information about the biological activity and specific information about certain tumours and be used in selected cancer-related situations. It can be especially helpful when conventional imaging doesn't provide enough information to answer the clinical question. This test is not a routine screening test for all neurological or cancer problems. A specialist decides if it is appropriate for their individual situation.

DOPA PET Scan Procedure

Typically, the DOPA PET scan procedure starts with an infusion of the radioisotope 18F-FDOPA, which is usually an injection into a vein (intravenous infusion). Once injected, the tracer is allowed to pass so it can reach and be concentrated in the tissue under evaluation. The patient is then placed on the PET scanner, and the radioactivity is detected to provide a detailed image. When pictures are taken, the patient must not move to make sure the image is clear. In some examinations, the patient might be asked to prepare for the scan beforehand, while the centre may also provide instructions to follow during the imaging process itself. These images are then analysed and interpreted by a skilled and trained nuclear medicine doctor. PET imaging can also offer functional data, and when clinically indicated, PET/CT can combine functional and anatomical information from CT.

DOPA PET Scan for Parkinsonian Disorders

An important use of F-DOPA PET scan is to measure how active the dopamine system is in the brain. Parkinsonian disorders may sometimes be hard to differentiate from other diseases that may also produce tremor, stiffness, or movement-related abnormalities. With the reduced dopamine activity shown by F-18-DOPA PET, the scan could also potentially help in the clinical assessment of Parkinson's disease and other Parkinsonian-related disorders. However, the scan alone cannot provide a diagnosis; its images must be interpreted by a trained nuclear medicine physician in the context of the patient's symptoms and other findings.  To establish a diagnosis, doctors will consider the person's symptoms and look for signs in their neurological assessment, medical history, and other tests.

DOPA PET Scan in Cancer Evaluation

In selected tumour-related investigations, F-DOPA PET can be used as well. Amino-acid PET tracers (e.g. FDOPA) may be used to assess the type of certain brain tumours, including gliomas. It can be used to give information on the biology of the tumour and may be used to supplement MRI scans and other imaging techniques. The value of DOPA PET differs with the tumor type and with the clinical question. This should only be done if the treating professional or nuclear medicine doctor recommends it.

How Should You Prepare for a DOPA Test?

The preparation will depend on the reason for the scan and the “protocol” of the centre. Important history to capture consists of the patient's current medications, medical or surgical history, prior imaging studies, and any treatment received. The nuclear medicine staff will give you special instructions on diet, fluids, medication, and other preparation instructions. These instructions should be followed carefully and not changed without guidance from the healthcare provider or nuclear medicine team. 

Is the DOPA PET Scan Safe?

Exposure in DOPA PET comes from a small amount of radiation from the radioactive tracer. When carefully prescribed and administered, nuclear medicine procedures are generally safe, although any risks and benefits should be weighed for the individual patient. Pregnant women or those suspected of being pregnant or who are breastfeeding should tell the medical team so that extra precautions are taken.

What Happens After the Scan?

Patients will be able to return to normal activity upon completion of the exam unless otherwise directed. The radioactivity of the radiotracer slowly fades over time, and the radiotracer is excreted from the body. With certain nuclear medicine procedures, patients may be required to consume fluids, depending on their medical status and the procedure.

Why Choose Molecular Diagnostics and Therapy?

Molecular Diagnostics and Therapy offers cutting-edge diagnostic and nuclear medicine services to assist in the interpretation of various health conditions. Specialist molecular imaging can supply functional information in addition to normal anatomical imaging. Depending on the patient's condition and the question to be answered, a DOPA PET scan may or may not be considered. A specialist will be able to suggest what imaging techniques will be necessary and what the results will mean, taking into account the general condition of the patient.

Conclusion

DOPA test (also known as F-DOPA PET scan) is a special kind of nuclear medicine study that can get information about dopamine activity and other biochemical processes. It is used in some neurological examinations (e.g., Parkinsonian disorders) and in some investigations related to tumors. The DOPA PET scan procedure generally involves injecting the 18F-FDOPA radiotracer, followed by PET imaging to evaluate the relevant biological activity. The test is a special test and should be used if it is indicated for a certain clinical situation. Molecular Diagnostics and Therapy provides advanced diagnostic and nuclear medicine services to support appropriate evaluation and care for patients.