Digital [18F]FDG PET/CT showed higher sensitivity for cranial giant cell arteritis when the scan included a specific assessment of the arteries in the head, according to an international prospective study. Sensitivity rose from 50.0% to 86.4%, meaning the test identified a larger share of patients who ultimately received a GCA diagnosis. The reported specificity was 100.0%, but its 95% confidence interval, the range given for uncertainty around that estimate, was 91.2% to 100.0%.
The authors say the results point to digital PET/CT as a potentially useful first-line test for suspected cranial GCA. The study does not establish that PET/CT should replace DUS or temporal artery biopsy, nor does it show that using the scan changes treatment decisions or patient outcomes.
How the tests compared
For comparison, DUS, an ultrasound examination of the temporal and axillary arteries, had a sensitivity of 68.2% and a specificity of 92.5%. In practical terms, PET/CT with cranial-artery assessment identified more of the patients with a final GCA diagnosis in this study, while its reported rate of correctly ruling out GCA among those without the diagnosis was higher than the DUS figure. The 95% confidence intervals were 52.4% to 81.4% for DUS sensitivity and 79.6% to 98.4% for DUS specificity.
The investigators compared both tests with a final clinical diagnosis made at six months. PET/CT was read independently by two blinded readers using standardized visual grading scales, with a third reader settling disagreements. A temporal artery biopsy could be performed, but it was left to the treating physician rather than required for every participant.
What the study measured
The analysis included 84 people after eight of 92 enrolled subjects were excluded because they did not undergo DUS. GCA was diagnosed in 44 of the 84 analyzed patients. Participants were at least 50 years old and had suspected GCA based on classical symptoms and inflammatory markers. People who had received corticosteroids for more than three days before PET/CT, or who had prior vasculitis, were excluded.
The analyzed subjects had a mean age of 72 years and a mean CRP level of 70.7 mg/L. Mean follow-up was 27 months, with individual follow-up ranging from six to 74 months. These details describe the group studied and do not show that the same performance would apply in other suspected-GCA populations or clinical settings.
A promising result with unanswered questions
The higher sensitivity was reported when cranial-GCA assessment was incorporated into the PET/CT interpretation. That finding makes the way the scan is read central to the reported result. The figures therefore apply to the particular PET/CT and DUS procedures used in this study, rather than automatically to every imaging protocol.
The study was cross-sectional and focused on diagnostic accuracy. It therefore cannot answer whether making PET/CT the first test would improve clinical decisions, symptoms, or long-term outcomes. The supplied analysis also reports no formal statistical test of superiority between PET/CT and DUS, so the results should not be presented as a statistically proven win for one test over the other.
The lack of a uniform biopsy procedure is another constraint on interpretation, as is the exclusion of the eight enrolled subjects who did not undergo DUS. The analysis does not provide site-specific recruitment, biopsy completion, or detailed diagnostic counts. Further work would need to establish whether the reported performance is reproducible across participating sites and broader groups of patients with suspected GCA.
Publication details
The article was accepted on 6 August 2026 and published as the version of record on 21 August 2026 in the European Journal of Nuclear Medicine and Molecular Imaging. The study was supported by a CIORA grant from the Canadian Rheumatology Association Foundation, and the authors report no sponsor involvement that could have influenced the outcome or conflicts of interest regarding the manuscript material.
Paper data and sources
Original title: Digital [F]FDG PET/CT as first-line diagnostic modality for cranial giant cell arteritis.
Authors: Gad Abikhzer, Aubert Roy, Maxime Samson et al.
Journal/Repository: European journal of nuclear medicine and molecular imaging
Status: Peer-reviewed
First online: 2026-08-21
DOI: 10.1007/s00259-026-08131-7
Original paper · Full text