AJR: Skeletal imaging with 18F-NaF is 'superior' to standard tracers

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Skeletal imaging with 18F-NaF harnesses both the imaging characteristics of PET and the improved biodistribution of the fluoride tracer in comparison with standard nuclear techniques, resulting in images that can effectively be used to investigate the cause of bone pain in children, according to the September issue of the American Journal of Roentgenology.

Although not commonly used in current clinical practice, the PET agent 18F-NaF provides an “excellent alternative” to the standard tracers used for radionuclide bone scintigraphy, the study authors wrote.

They explained that 18F-labeled NaF has a biodistribution generally similar to that of 99mTc-MDP, but its lower protein binding in blood allows a more rapid single-passage extraction by bone, thus permitting earlier image acquisition.

Thus, Laura A. Drubach, MD, of the department of radiology at the Children's Hospital in Boston, and colleagues demonstrated the use and appearance of 18F-NaF PET and showed examples of its utility in the assessment of bone pain in children.

In an experimental model performed in rats, investigators found that stress fractures produced an increase in the uptake of 18F-NaF and that the uptake was proportional to the level of the initial bone damage, the researchers reported. The increased uptake was seen as early as one day after a loading injury, with peak uptake at approximately one week after injury. 

“These results provide a rational basis for the use of 18F-NaF PET when imaging trauma patients and those with sports injuries,” they wrote. “In the specific setting of trauma related to child abuse, 18F-NaF PET has been shown to be useful in the detection of skeletal fractures and, in particular, to be highly sensitive for the detection of rib fractures that may be difficult to identify radiographically.”

Drubach and colleagues obtained 18F-NaF PET images shown on an Advance Nxi PET scanner (GE Healthcare). Whole-body scans or limited images of the region of interest were acquired in either the 2D or 3D mode, beginning 30 to 45 minutes after tracer injection, with the use of both emission and transmission scans for attenuation correction.

Because these studies were performed as PET and not PET/CT acquisitions, fusion software was used to register PET with diagnostic CT images, when relevant, according to the researchers. When PET/CT is available, concomitant acquisition of PET and CT provided convenient localization of findings, Drubach et al wrote.

In conclusion, the researchers wrote that “the excellent image quality obtained with 18F-NaF PET skeletal imaging makes it an attractive option for the evaluation of suspected bone trauma and stress-related injuries.”