Effect of dental metal prostheses and its metal artefacts on the incidence of nodular overcorrection on PET/CT images: a comparison between silicon photomultiplier and photomultiplier tube PET

Objectives Positron emission tomography (PET) images are reconstructed using computed tomography (CT)-based attenuation correction, which may cause artefactual errors due to CT artefacts. This study aimed to investigate the effects of metallic dental prostheses and metal artefacts on the incidence of nodular overcorrection in PET/CT images of the oral cavity in patients with head and neck tumours. Methods We retrospectively reviewed the F-18 fluorodeoxyglucose PET/CT images of 27 and 20 patients using silicon photomultiplier (SiPM) and photomultiplier tube (PMT) PET, respectively. We evaluated the presence or absence of overcorrection of tumour-like nodular uptake, number of metallic dental prostheses, number of metallic prosthetic blocks, mean CT values, bright-band artefact area/ratio, and dark-band artefact area/ratio. Results There was no significant difference in the incidence of overcorrections between SiPM and PMT PET; however, overcorrections in the former were significantly smaller in size than those in the latter. Overcorrection in PMT PET was more likely to occur when the number of metallic dental prostheses, number of metallic dental prosthetic blocks, mean CT value, and bright-band artefact area/ratio were high. However, there was no significant difference in SiPM PET overcorrection between the positive and negative overcorrection groups for the above conditions. Conclusions Overcorrection was associated with metallic dental prostheses and CT artefacts; however, the conditions may have scanner-specific characteristics. Advances in knowledge Small tumour-like overcorrections appear on SiPM PET, which should be noted because it is more difficult to notice overcorrections. It is important to analyse the images while checking the pre-attenuation correction PET.