What is Flor-18 NaF PET/CT, how does it reveal tumor focus?

Theranostic is an emerging field in the medicine world. It is an approach in which tumor and metastases detected by imaging with a tumor-specific drug and they can be treated with a same specific drug, which is already known, how far it will go and its power to affect the diseased tissue. This approach enables the transition from traditional medicine to personal contemporary medicine practices.

In prostate cancer bone metastases, on the one hand, with Fluorine-18 NaF (F-18 NaF) PET / CT, can be imaged with high sensitivity; on the other hand, specific and targeted treatment of these tumoral tissues can be performed with Radium-223. This is a very good example for theranostic applications. More than 90% of patients with metastatic castration-resistant prostate cancer have evidence of bone metastasis, which is the main cause of disability and decreased quality of life and death,. Unlike deaths from many other types of cancer, deaths from prostate cancer often result from bone metastasis and complications.

What are the advantages of Flor-18 NaF PET/CT ?

F-18 NaF PET / CT has ideal properties as a bone imaging agent and produces superior quality images in as short time as 45-60 minutes. The ability of F-18 NaF PET to show changes in the bone matrix and high resolution tomographic skeletal images of the PET / CT scanner are much higher in sensitivity compared to conventional Nuclear Medicine SPECT or planar bone scintigraphy. In addition, its ability to image the entire skeleton tomographically makes F-18 NaF PET / CT useful in the diagnosis of a wide variety of bone diseases. F-18 NaF PET / CT is an ideal alternative with more successful results compared to traditional bone scintigraphy for many patients, especially those who have been investigated for bone metastasis.

PET / CT imaging with F-18 NaF, a bone imaging agent with a short half-life of 100 minutes, allows a unique evaluation of regional bone metabolism. F-18 NaF binds to new bone formation sites and acts as a marker of bone blood flow and osteoblastic activity.

2/3 of bone is made up of minerals, 1/3 is made up of collagen, extracellular matrix and various bone lining cells. The mineral matrix consists of calcium hydroxyapatite. After the chemisorption of fluoride ions onto the hydroxyapatite surface, they form fluoroapatite replacing with hydroxyl (OH−) ions in the crystal. Due to the first pass clearance of F-18 NaF close to 100%, it is very fast to clear from plasma, which allows much earlier imaging than conventional bone scintigraphy.

Many studies have shown that F-18 NaF PET / CT is more accurate than traditional bone scintigraphy or bone SPECT in the evaluation of malignant bone diseases. Results such as higher quality imaging, increased clinical accuracy, greater convenience for the patient and referring physician, pave the way for the use of F-18 NaF PET / CT in the imaging of malignant skeletal diseases and more efficient use of Nuclear Medicine resources.

Who is Flor-18 NaF PET/CT applied to ?

The main clinical indications of F-18 NaF PET / CT can be listed as follows:
● Identification of bone metastases
● Determining the extention of the disease correctly
● Localization of malignant bone lesions
● Evaluation of the distribution of osteoblastic activity before Radium-223 application for the treatment of bone pain
● Evaluation of treatment response

Is Flor-18 NaF PET/CT safe ?

F-18 NaF PET / CT scanning is a safe and routine procedure. Millions of PET / CT scans are being performed all over the World without any problems. The injected radioactive substance F-18 NaF is safe and has no known side effects. The amount of radioactivity administered for PET / CT scanning is small and is cleared from the patient’s body at the end of the day. It takes a few hours for patients to leave the Nuclear Medicine Clinic and it is recommended that contact with others (especially children and pregnant women) be minimized for 6 hours following the PET / CT scan.

Preperation before Flor-18 NaF PET/CT

Information required during F-18 NaF PET / CT appointment
• Indication
• History of malignancy
• Type and date of previous oncological treatments (e.g. chemotherapy and / or radiotherapy)
• Previous fractures or recent trauma (location and date)
• Previous orthopedic surgical interventions (date, type and place of intervention)
• Previous infection and location
• Urinary diversion procedures
• Location of each bone pain
• Other images and reports (especially bone scintigraphy, CT or MRI)

Patient preperation

Patients do not need to be fasting for F-18 NaF PET / CT procedure.
They can take their medication as usual.

Patients should drink at least two glasses of water before and after F-18 NaF injection to increase renal excretion, reduce radiation exposure and achieve optimal image quality. It will be beneficial in reducing radiation exposure if they continue to drink water for the rest of the day after the examination.

Immediately before F-18 NaF PET / CT imaging, patients should empty their bladder.

All metal items / jewelry / prostheses should be removed to avoid image artifacts.

How is Flor-18 NaF PET/CT performed ?

F-18 NaF PET / CT imaging was performed approximately 30-60 minutes after the IV bolus injection of F-18 NaF at a dose of 1.5-3.7 Mbq / Kg (0.04-0.1 mCi / Kg). The maximum recommended total dose for obese patients is 370 MBq (10 mCi).

It takes a few hours for patients to leave the Nuclear Medicine Clinic and it is recommended that contact with others (especially children and pregnant women) be minimized for 6 hours following the PET / CT scan.

Normal biodistribution and image interpretation

In general, in normal F-18 NaF PET / CT, a symmetrical and homogeneous distribution of F-18 NaF is observed in the entire skeleton. In addition, since F-18 NaF is excreted through the urine, in cases with normal renal function, kidney, ureter and bladder are also displayed.

Any reason that may altered bone metabolism, usually due to regional blood flow and / or new bone formation, can also cause increased F-18 NaF uptake.

Lesions with minimal osteoblastic bone changes or lesions with mainly osteolytic character may show many different patterns, such as, from a lesion that does not show an increase in activity, to activity only surrounding the lesion, or significantly increased F-18 NaF uptake. F-18 NaF uptake can also be quite prominent in benign bone lesions. Therefore, the degree of F-18 NaF uptake (SUVmaximum etc.) cannot distinguish benign from malignant lesions. However, the pattern of involvement can be quite characteristic for the specific diagnosis. While the CT component of PET / CT is also used for lesion localization, it potentially improves interpretation.

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