Impact of respiratory gating and ECG gating on 18F-FDG PET/CT for cardiac sarcoidosis

BACKGROUND

The aim of this study was to estimate the impact of respiratory and electrocardiogram (ECG)-gated FDG positron emission tomography (PET)/computed tomography (CT) on the diagnosis of cardiac sarcoidosis (CS).

METHODS AND RESULTS

Imaging from thirty-one patients was acquired on a PET/CT scanner equipped with a respiratory- and ECG-gating system. Non-gated PET images and three kinds of gated PET/CT images were created from identical list-mode clinical PET data: respiratory-gated PET during expiration (EX), ECG-gated PET at end diastole (ED), and ECG-gated PET at end systole (ES). The maximum standardized uptake value (SUVmax) and cardiac metabolic volume (CMV) were measured, and the locations of FDG accumulation were analyzed using a polar map. The mean SUVmax of the subjects was significantly higher after application of either respiratory-gated or ECG-gated reconstruction. Conversely, the mean CMV was significantly lower following the application of respiratory-gated or ECG-gated reconstruction. The segment showing maximum accumulation was shifted to the adjacent segment in 25.8%, 38.7%, and 41.9% of cases in EX, ED, and ES images, respectively.

CONCLUSION

In FDG PET/CT scanning for the diagnosis of CS, gated scanning is likely to increase quantitative accuracy, but the effect depends on the location and synchronization method.

Respiratory-gated 18F Fluorodeoxyglucose Positron Emission Tomography/Magnetic Resonance Imaging in Evaluation of Primary Gastric Lesions and Gastric Lymph Nodes in Patients with Gastric Cancer

AIMS

To evaluate the added value of respiratory-gated positron emission tomography (PET) in ¹⁸F fluorodeoxyglucose (FDG) PET/magnetic resonance imaging (MRI) in the visual and semi-quantitative assessment of primary gastric lesions and gastric lymph nodes for patients with gastric cancer.

MATERIALS AND METHODS

In total, 102 upper abdominal respiratory-gated and whole-body ¹⁸F FDG PET/MRI of 88 patients with gastric cancer were evaluated visually and semi-quantitatively. For 41 patients who underwent surgery, histopathological and PET findings were compared. Three PET images were obtained from upper abdominal PET data: non-Q static (non-QS) PET from all counts, respiratory-gated Q static (QS) PET from counts in the end-expiration phase of breathing, shortened 4 min (S4min) PET that was reconstructed to obtain similar counts to QS PET. The semi-quantitative parameters (standardised uptake values, metabolic tumour volume, total lesion glycolysis) of primary lesions for each PET image, the sizes of primary lesions and the patient's body mass index were recorded. According to lymph node stations, the presence and numbers of positive lymph nodes and visual scores of lymph nodes for each PET image were recorded.

RESULTS

The patients with smaller gastric lesions (≤30 mm) or higher body mass index (>30) had significantly higher standardised uptake value percentage changes in QS PET compared with non-QS PET (all P < 0.05). The third (lesser curvature), fourth (greater curvature) and sixth (infra-pyloric) lymph node stations had significantly higher visual scores in the QS PET than in the others. The fourth lymph node station had a significantly higher number of FDG-positive lymph node in the QS PET than in the non-QS and the whole-body PET images. In the fourth station, sensitivity, positive predictive value, negative predictive value and accuracy increased in the QS PET compared with the others.

CONCLUSION

Respiratory-gated PET/MRI was found to be significantly superior in the evaluation of especially the fourth lymph node station, smaller gastric lesions and in the patients with a higher BMI compared with the non-respiratory-gated PET images.