PET Scan and Diabetes

What is a PET Scan?

A PET scan is an imaging test that allows your doctor to look for diseases in your body.

The test uses a special dye containing radioactive tracers. These tracers are either swallowed, inhaled, or injected into an arm vein, depending on the body part being examined. Certain organs and tissues then absorb the tracer.

When detected by a PET scan, the tracers help your doctor see how your organs and tissues are functioning.

The tracer accumulates in areas of high chemical activity, which is helpful because some body tissues and diseases have a higher level of chemical activity. These areas of disease show up as bright spots on the PET scan.

A PET scan can measure blood flow, oxygen use, how your body uses sugar, and much more. PET scans are usually outpatient procedures. This means you can go about your day after the exam.

How Does a PET Scan Work?

In a PET scan, a radioactive tracer called FDG is used. FDG mimics glucose, the body's main sugar. Since diabetics have difficulty processing glucose, FDG may not work as well if blood sugar isn't well-controlled.

This procedure is performed to produce detailed images of your body. Before the procedure, you will receive a small injection of radioactive sugar (called FDG) into a vein. You will be asked to relax in a recliner for up to an hour while the FDG travels throughout your body. It's important that you don't move during the scan. The scan itself will be completed in 45 to 60 minutes.

How Does Diabetes Affect a PET Scan?

Diabetes can affect the PET scan in two ways:

• To ensure efficient FDG uptake in your body, it's crucial to have normal blood sugar levels. Otherwise, it could compromise the imaging results.
• To optimize scan results, maintaining a balanced insulin level is important. High insulin can cause excessive FDG uptake by healthy tissues and organs, altering the images.

To ensure accurate PET scan results, patients must have adequate blood glucose levels. Therefore, before the radiotracer injection, all patients undergoing this exam will have a blood glucose test to measure their blood sugar. An optimal level of 4 to 10 (millimoles per liter) is recommended before the scan procedure. If the level is above 12.5 mmol/l, the scan will generally need to be rescheduled.

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Tips for Your PET Scan When You Have Diabetes

Here are some tips to help you get the best results from a PET scan:

• To avoid altering PET scan results, avoid strenuous physical activity and caffeine for 24 hours before the test.
• For optimal image quality during your PET scan, it's recommended to follow a high-protein, low-carbohydrate diet for 24 hours prior to the exam.
• At your appointment, avoid all food or drinks containing glucose. This includes chewing gum, candy, cough syrup, mints, flavored water, coffee, and tea. Due to the test's sensitivity, the presence of sugar can negatively affect the results. However, you can drink unlimited plain water until your scheduled PET scan time. Keep this in mind for accurate results.
• You may take any medications you normally take before your appointment if they can be taken on an empty stomach. For simplicity, diabetes medications are generally allowed. However, ensure your blood sugar is between 70-100 mg/dL or below 150 mg/dL before the exam.
• Wear comfortable clothing on the day of your exam for your comfort. Avoid dresses with buttons or zippers;
• Before the scan, an IV line will be placed in your arm to inject the medication. You'll need to wait approximately 60 minutes for the tracer to reach all parts of your body. You may also be asked to drink oral contrast. The entire procedure takes about 3 hours;

PET Scan Preparation: Type I and Type II Diabetes

Type I Diabetes

If you have Type I diabetes, schedule your PET scan for early morning. The day before, take your normal insulin dose. Avoid eating anything after midnight. On the day of your PET scan, you can receive your insulin injection after the scan and have your breakfast medication.

Type II Diabetes

Schedule your PET scan for the morning or afternoon if you have Type II diabetes controlled with diet or oral medication. Just ensure you fast for at least 4 hours before the scan and take your medications at your usual time.

Getting a PET Scan with Diabetes

For optimal appointment results, it's crucial to inform your diagnostic center of any diabetes condition you have.

To ensure proper PET scan preparation, your medical team will guide you on pre- and post-exam measures and appropriate medication to manage your blood sugar if you are diabetic. They will also inform you about the foods and medications to consume on the day of the scan. Keep in mind that your PET scan appointment time may be influenced by your recent glucose level and your tendency towards low morning blood sugar.

If your fasting blood sugar is below 70 mg/dl, you may drink a glass of fruit juice before your PET scan.