wk9b Future directions bone scans

This set covers the future directions of bone scanning, focusing on the mechanism, technique, and comparison of 18F Sodium Fluoride (NaF) PET/CT imaging.

$18F\text{ NaF}$ Bone Imaging

A PET/CT bone agent ($18F$ Sodium Fluoride) used for detecting benign and malignant bone disease with improved sensitivity and specificity for lytic lesions compared to $^{99m}Tc\text{ MDP}$.

Chemisorption

The mechanism of uptake where $18F\text{ NaF}$ is directly incorporated on to the surface of the hydroxyapatite matrix of bones.

Ion exchange

A process following chemisorption where fluoride ions exchange with hydroxyl ions in the crystal to form fluoroapatite.

First pass extraction

The phenomenon where approximately $50\%$ of $18F\text{ NaF}$ is taken up by bones immediately after injection.

Bladder wall

The target organ for $18F\text{ NaF}$ imaging that requires extra hydration and frequent voiding from the patient to minimize radiation dose.

Standard $18F\text{ NaF}$ Dose

$185-370\,MBq$ administered via intravenous injection (IVI).

Epiphyseal plates

Areas in children that exhibit symmetric increased uptake as part of a normal appearance on an $18F\text{ NaF}$ scan.

Pool Scans

Imaging that must be acquired immediately post-injection due to the rapid blood clearance of $18F\text{ NaF}$.

$18F\text{ NaF}$ Imaging Timing

Begins $45\,\text{minutes}$ to $1\,\text{hour}$ post-injection, with longer wait times required for better quality images of extremities.

$^{99m}Tc\text{ MDP}$ vs $18F\text{ NaF}$ Radiation Dose

The radiation dose to the patient is approximately $7\,\times$ higher for $18F\text{ NaF}$ compared to $^{99m}Tc\text{ MDP}$.

Hydroxyapatite matrix

The crystal structure of the bone where $18F\text{ NaF}$ undergoes chemisorption and subsequent ion exchange.

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