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

## TL;DR

This study compares 60-minute and 90-minute FDG uptake times in PET/CT scans for diagnosing cardiac sarcoidosis and finds similar diagnostic accuracy with shorter uptake times.

## Contribution

The study demonstrates that a 60-minute uptake time is as effective as a 90-minute uptake time for cardiac sarcoidosis detection when myocardial suppression is adequate.

## Key findings

- Diagnostic accuracy was 97% at 60 minutes and 92% at 90 minutes for cardiac sarcoidosis detection.
- No statistically significant difference in diagnostic performance was observed between the two uptake times.
- Shorter uptake protocols may improve workflow and patient comfort without compromising diagnostic accuracy.

## Abstract

[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.

The online version contains supplementary material available at 10.1186/s13550-026-01380-5.