From the Guidelines
No, a whole body PET-CT scan with 18F-FDG is not routinely ordered for suspected giant cell arteritis (GCA). The preferred imaging modality for GCA diagnosis is typically a temporal artery ultrasound or a temporal artery biopsy, which remains the gold standard 1. In some cases, high-resolution MRI of the cranial vessels, CT angiography, or targeted PET-CT of the cranial and large vessels may be used, but not whole body imaging. While 18F-FDG PET-CT can detect vascular inflammation in large-vessel vasculitis, its use in GCA is generally limited to evaluating large-vessel involvement rather than as a first-line diagnostic tool 1.
Some key points to consider:
- The radiation exposure, cost, limited availability, and lack of specificity for cranial vessel inflammation make whole body PET-CT impractical as a routine diagnostic test for GCA 1.
- Early diagnosis and treatment of GCA is crucial to prevent vision loss, so clinicians typically rely on more readily available and targeted diagnostic approaches 1.
- High-resolution MRI or FDG-PET can be used as alternatives to ultrasound for the assessment of cranial arteries in patients with suspected GCA, but whole body PET-CT is not recommended 1.
- The task force urged rapid access to diagnostic imaging tests, commensurate with fast-track clinics for patients with suspected GCA, and imaging should best be performed before, or at least, within 72 hours after commencing GC therapy 1.
Overall, the use of whole body PET-CT scan with 18F-FDG is not recommended for suspected GCA, and clinicians should rely on more targeted and readily available diagnostic approaches.
From the Research
Whole Body PET-CT Scan for Suspected GCA
- A whole body PET-CT scan with 18F-FDG can be ordered for suspected Giant Cell Arteritis (GCA) to assess large vessel involvement 2, 3, 4.
- The scan is particularly useful in patients with negative temporal artery biopsy results, providing a diagnostic accuracy of 73% 5.
- The timing of the examination and the cumulative dosage of glucocorticoids can influence the likelihood of a positive result, with earlier tests being more likely to detect inflammation 2.
- Different scoring methods can be used to evaluate the PET-CT scan results, including visual and semiquantitative methods, with the aorta-to-liver ratio showing high diagnostic accuracy 3.
- Laboratory markers such as C-reactive protein (CRP) and white blood cell count (WBC) may have limited diagnostic utility in ordering an 18F-FDG PET-CT scan for GCA patients 6.
Indications for Whole Body PET-CT Scan
- Suspected GCA with negative temporal artery biopsy results 5
- Assessment of large vessel involvement in GCA patients 2, 3, 4
- Monitoring treatment response in GCA patients 4