Small fluctuations in blood sugar can lead to very different PET/CT results!

Author: Gao Mingyue

First review: Shi Xue

Final judge: Zhao Yinlong

Have you ever wondered: When you go to the hospital for a PET/CT scan, why do doctors repeatedly remind you to fast? The reason has a lot to do with blood sugar. Today, let's talk about the impact of blood sugar on PET/CT scans.

1. What is PET/CT examination?

PET/CT is an advanced medical imaging technology that combines PET (positron emission tomography) and CT (computed tomography). In simple terms, PET can show the activity of body cells, while CT can provide clear images of anatomical structures. The combination of the two can not only detect early tumors, but also accurately locate the location of lesions.

During a PET/CT scan, doctors inject patients with a tracer called fluorodeoxyglucose (FDG). FDG is a glucose-like substance that is taken up in large quantities by metabolically active cells in the body, such as tumor cells. By scanning the distribution of FDG, doctors can detect potential lesions.

2. Why does blood sugar affect PET/CT examination?

FDG and glucose have a very similar structure. The cells in our body are like "little greedy cats" that usually "eat" glucose first to obtain energy. When blood sugar rises, the cells are "full" and the uptake of FDG will decrease. This may lead to insufficient uptake of FDG by metabolically active cells such as tumor cells, which will not be clearly displayed on the image, affecting the doctor's judgment of the condition.

How to control blood sugar before the test

1. Non-diabetic patients

Before the test, blood sugar must meet the test standards, <7.8mmol/L.

It is recommended to fast for 4-6 hours before the examination and not to inject sugary liquids.

Diabetic patients

Before examination, blood sugar levels of diabetic patients should be controlled at <11.1mmol/L, and blood sugar levels should be kept as stable as possible.

Patients taking insulin

Rapid-acting insulin: It is recommended to check 4 hours after injection.

Short-acting insulin: It is recommended to check 6 hours after insulin injection and low-sugar meal;

Intermediate-acting insulin: It can be injected the night before, which can control blood sugar levels without interfering with PET examination.

Long-acting insulin: It will interfere with PET examination and is not recommended for use before the examination.

Patients taking oral hypoglycemic drugs: Metformin can significantly increase the intestinal uptake of 18F-FDG, causing excessive intestinal development. Stop taking this drug 48 hours before PET scanning.

4. What should you pay attention to after the inspection?

Drink plenty of water: This helps the body excrete any remaining tracer as quickly as possible.

Avoid contact with pregnant women and children: There is still a small amount of radiation in the body within 24 hours after the examination. Try to avoid long-term close contact with pregnant women and children.

It is very important to control blood sugar before PET/CT examination, which is related to the accuracy of the test results. You must fast before the examination as required, and there are corresponding precautions after the examination. I hope everyone can pay attention to blood sugar health. After all, only when blood sugar is stable can the body be better and the test results are more reliable.