You will be assigned to one of two groups based on your current fatigue level measured by the Fatigue Severity Scale. This scale helps doctors understand how tired you feel in your daily life.

Group 1 includes patients who currently have a fatigue score of 4 or higher, meaning you still experience significant tiredness after your COVID-19 infection.

Group 2 includes patients who previously had high fatigue scores but now have scores below 4, meaning your tiredness has improved over time.

You will complete several questionnaires about your health, symptoms, and how you feel. These forms help doctors understand your current condition and any ongoing problems you may have.

The questionnaires will ask about your breathing difficulties, tiredness levels, and other symptoms you may be experiencing since your COVID-19 infection.

You will undergo lung function tests to measure how well your lungs are working. These tests check how much air you can breathe in and out.

You will perform a 6-minute walk test, which measures how far you can walk in 6 minutes. This helps doctors understand your physical fitness and breathing capacity.

Blood samples will be taken to measure various markers in your blood that show inflammation and tissue changes in your body.

You will receive an injection of [68Ga]FAPI-46, which is a special radioactive substance that helps doctors see active tissue repair cells called fibroblasts in your body.

This medication is given as a single injection into a vein in your arm. The injection contains a small amount of radioactive material that is safe for medical imaging.

The radioactive substance will travel through your bloodstream and attach to areas where your body is trying to repair tissue damage, particularly in your lungs.

After receiving the injection, you will have a PET/CT scan. This is a special type of medical imaging that combines two different scanning techniques to create detailed pictures of the inside of your body.

The scan will focus on your lungs and chest area to see if there are active repair processes happening in your lung tissue.

You will lie still on a scanning table while the machine takes pictures. The procedure is painless, but you need to remain very still during the scanning process.

The doctors will analyze the scan images to measure the activity of fibroblasts in your lungs. They will calculate something called a target to background ratio, which compares the radioactive signal in your lungs to other areas of your body.

The scans will also measure the uptake of the radioactive substance in your back muscles near your spine, which serves as a comparison point.

If you have areas of ground glass opacities on your lung scans (cloudy areas that may indicate tissue changes), doctors will compare these to the radioactive uptake patterns.

Your scan results will be compared with your questionnaire answers, lung function tests, and blood test results to understand the relationship between tissue repair activity and your symptoms.

The doctors will look at whether patients with ongoing tiredness and breathing problems show different patterns of tissue repair activity compared to patients whose symptoms have improved.

Your individual results will be analyzed as part of the larger study group to help researchers understand how COVID-19 affects lung tissue repair over time.