Optimizing PET/CT protocols: is 60-minute [18 F]F-FDG uptake sufficient for cardiac sarcoidosis?

[¹⁸F]F-FDG PET/CT is an established imaging modality for diagnosing cardiac sarcoidosis (CS). While a 90-minute uptake time is commonly recommended to enhance target-to-background ratio, its added diagnostic value remains unclear. This study aimed to compare the diagnostic performance of 60-minute versus 90-minute uptake times. Eighty-seven patients (45 females, 42 males) with suspected CS underwent whole-body FDG PET/CT at 60 min post-injection (p.i.), followed by an additional chest scan at 90 min p.i. Patient preparation included a low-carbohydrate diet, prolonged fasting, and weight-based heparin administration. Three blinded readers with varying experience independently assessed the scans using binary classification for typical sarcoidosis-related FDG uptake, provided adequate myocardial glucose suppression was achieved. Inter- and intrarater agreement were analyzed using Fleiss' and Cohen's κ, respectively. Diagnostic accuracy was determined by majority vote, using Japanese Circulation Society (JCS) criteria as the reference standard.

Interrater agreement was substantial (Fleiss' κ = 0.690-0.693), and intrarater agreement ranged from substantial to almost perfect (Cohen's κ = 0.703-0.899). Among patients with sufficient myocardial suppression, diagnostic accuracy was 97% (n = 62) at 60 min and 92% (n = 65) at 90 min. No statistically significant differences were observed between the two time points (p = 0.22).

FDG PET/CT with a 60-minute uptake time offers diagnostic accuracy comparable to that of a 90-minute uptake for CS detection, provided adequate myocardial suppression is achieved. Shorter uptake protocols may streamline workflow and improve patient comfort without compromising diagnostic integrity.