Variable Aβ tracer uptake in hyperostosis frontalis interna: implications for brain Aβ PET/CT interpretation

Area of Science:

• Neurology
• Radiology
• Nuclear Medicine

Background:

• Hyperostosis frontalis interna (HFI) is a common incidental finding on head CT scans.
• HFI involves thickening of the inner table of the frontal bone.
• Its impact on amyloid-beta (Aβ) positron emission tomography (PET) imaging is not well understood.

Purpose of the Study:

• To report two cases of HFI identified during amyloid-beta PET/CT imaging.
• To describe distinct patterns of tracer uptake in the calvarium affected by HFI.
• To highlight potential misinterpretations in quantitative PET analyses due to HFI.

Main Methods:

• Two patients with HFI underwent 18F-florbetaben PET/CT imaging.
• Scans were assessed for amyloid-beta plaque burden using Centiloid values.
• Tracer uptake within the HFI region of the calvarium was specifically examined.

Main Results:

• Patient 1 showed marked 18F-florbetaben uptake within the HFI region, with a Centiloid of 59.
• Patient 2 exhibited HFI but no 18F-florbetaben uptake in the affected calvarium, with a Centiloid of 82.
• Distinct patterns of tracer retention were observed in the HFI areas.

Conclusions:

• Off-target tracer retention in HFI can lead to visual and quantitative misinterpretations in Aβ PET scans.
• This is particularly relevant for older women with HFI.
• Careful visual inspection and adjusted quantification masks are crucial for accurate PET measurements in HFI patients.