Subharmonic and endoscopic contrast imaging of pancreatic masses – a pilot study

摘要

To use subharmonic imaging (SHI) to depict the vascularity of pancreatic masses compared to contrast-enhanced endoscopic ultrasound (EUS) and pathology.Sixteen patients scheduled for biopsy of a pancreatic mass were enrolled in an IRB-approved study. Pulse-inversion SHI (transmitting/receiving at 2.5/1.25MHz) was performed on a Logiq 9 system (GE Healthcare, Milwaukee, WI) with a 4C probe, while contrast harmonic EUS (transmitting/receiving at 4.7/9.4MHz) was performed with a radial endoscope (GF-UTC180; Olympus, Tokyo, Japan) connected to a ProSound SSD α-10 scanner (Hitachi-Aloka, Tokyo, Japan). Two injections of the contrast agent Definity (Lantheus Medical Imaging, N Billerica, MA) were administrated (0.3–0.4ml and 0.6–0.8ml for EUS and SHI). Contrast-to-tissue ratios (CTRs) in the mass and an adjacent vessel were calculated. Four physicians independently scored the images (benign to malignant) for diagnostic accuracy and inter-reader agreement.One subject dropped out before imaging, leaving 11 adenocarcinoma, 1 gastrointestinal stromal tumor with pancreatic infiltration and 3 benign masses. Marked subharmonic signals were obtained in all subjects with intra-tumoral blood flow clearly visualized using SHI. Significantly greater CTRs were obtained in the masses with SHI than with EUS (1.71±1.63 vs 0.63±0.89; p=0.016). There were no differences in CTR in the surrounding vessels or when grouped by pathology (p>0.60). The accuracies for contrast-EUS and SHI were low (<53%); albeit with a greater kappa value for SHI (0.34) than for EUS (0.13).Diagnostic accuracy of contrast-EUS and trans-abdominal SHI for assessment of pancreatic masses was quite low in this pilot study. However, SHI demonstrated improved tumoral CTRs relative to contrast-EUS.