A novel perfusion imaging technique of the pancreas: contrast-enhanced harmonic EUS (with video)

BackgroundContrast-enhanced harmonic-imaging techniques have been unavailable for EUS because of the limited frequency bandwidth and acoustic power output of current echoendoscopes.ObjectiveTo investigate the contrast harmonic imaging technique by using a prototype echoendoscope equipped with an adequate broad-band transducer that can detect harmonic signals from the US contrast agents.DesignIdentification of optimal settings (study I) and preliminary clinical investigations (study II).SettingBethesda General Hospital Bergedorf.PatientsA total of 104 patients undergoing standard EUS examinations.InterventionsContrast-enhanced harmonic EUS (CEH-EUS) was performed by using a prototype echoendoscope and extended pure harmonic detection mode, a specific mode for contrast harmonic imaging.Main Outcome MeasurementsIn study I, time-intensity curves for peak signal intensity were calculated after infusion of a contrast agent, SonoVue, and the changes in echo intensity were compared for different mechanical indices and interval times. In study II, intermittent and real-time continuous images of pancreatobiliary and gastroduodenal diseases obtained by CEH-EUS were evaluated in comparison with contrast-enhanced power-Doppler EUS (CED-EUS).ResultsIn study I, with the optimal mechanical index (0.4), homogeneous parenchymal perfusion images of the pancreas were obtained by intermittent imaging, and finely branching vessels of the pancreas were obtained with real-time continuous imaging. In study II, apparent perfusion and vessel images were observed in pancreatobiliary carcinomas, GI stromal tumors, and lymph-node metastases. CED-EUS failed to depict images of the fine vessels and parenchymal perfusion.LimitationsThe subjective nature of the findings, with a limited number of patients.ConclusionsCEH-EUS successfully visualized parenchymal perfusion and microvasculature in the pancreas and may play an important role in the differential diagnosis of digestive diseases.