Performance of novel tissue harmonic echo imaging using endoscopic ultrasound for pancreatic diseases

Abstract

Background and study aims: Recently, tissue harmonic echo (THE) imaging has advanced with the development of a new endoscopic ultrasound (EUS) monitor/processing unit. With this new technology, penetration (THE-P) and resolution (THE-R) images can be obtained. The aim of this study was to investigate the performance of this novel THE imaging using a new processing unit for pancreatic diseases.

Patients and methods: Fifty patients with pancreatic lesions (38 cystic, 12 solid) were retrospectively analyzed. At each examination, 3 EUS images of the same pancreatic lesion were obtained using B-mode, THE-P mode, and THE-R mode imaging. Each set of EUS images was randomly arranged and evaluated independently by 4 physicians blinded to the imaging technique. Images were compared using a Likert scale 5-point grading system for each parameter.

Results: For cystic lesions, THE-P mode images were significantly superior to conventional B-mode images for visualizing the boundary, septum, nodules, and total image quality (P < 0.05). THE-R mode images were significantly superior to conventional B-mode images for visualizing the boundary, septum, and total image quality (P < 0.05). However, for solid lesions, there was no significant difference in all the evaluation points between THE-P and conventional B-mode images. THE-R mode images were inferior to conventional B-mode images for visualizing the boundary, internal structure, and total image quality (P < 0.05).

Conclusions: For pancreatic cystic lesions, THE mode images provided better lesion characterization than conventional B-mode images. Further research is required to determine if this improvement will result in improved EUS diagnostics.

Fig. 1

The EU-ME2 is a high-quality compact ultrasound processor for use with endoscopic ultrasound equipment that has been designed for integration with conventional endoscopy on a single workstation. It is possible to use new functions such as Tissue Harmonic Echo (THE), Contrast Harmonic EUS (CH-EUS) and Elastography.

Fig. 2

Main duct intraductal papillary mucinous neoplasm of the pancreas in a 67-year-old woman. a Conventional B-mode imaging showed mural nodules (arrows) in the dilated main pancreatic duct (MPD) of the pancreatic body (arrows). b THE-P mode imaging showed mural nodules (arrows) in the dilated MPD more clearly than B-mode. c THE-R mode imaging clearly showed mural nodules (arrows) in the dilated MPD, similarly to the THE-P mode imaging.

Fig. 3

Intraductal papillary mucinous neoplasm of the pancreatic body in a 78-year-old woman. a Conventional B-mode imaging could not clearly detect the mural nodule in the cyst. b THE-P mode imaging revealed a mural nodule (arrows) in the cyst and more clearly visualized the boundary and total image. c THE-R mode imaging demonstrated a mural nodule (arrows), similarly to THE-P mode imaging.

Fig. 4

Intraductal papillary mucinous neoplasm of the pancreatic body in a 51-year-old man. a Conventional B-mode imaging could not clearly visualize the thickening of the septum (arrows) and nodule in the cyst. b THE-P mode imaging more clearly visualized the thickening of the septum (arrows) and nodule (arrowhead) in the cyst. c THE-R mode imaging was better than conventional B-mode imaging; however, it was slightly less clear than THE-P mode imaging.

Fig. 5

An 83-year-old woman with cancer of the pancreatic head. a Conventional B-mode imaging clearly revealed the boundary of the solid lesion (arrows). The pancreatic cancer caused an obstruction in the main pancreatic duct (MPD) and invaded the superior mesenteric vein (SMV) (arrowhead). b THE-P mode imaging clearly demonstrated the boundary and internal structure, similarly to B-mode imaging. c THE-R mode imaging was not superior to the other imaging techniques, particularly because the distal image produced was poor.

Fig. 6

Correlation between mode grade and distance in pancreatic cystic lesions The grade for the total image quality of B-mode was not significantly correlated with the distance from the EUS probe to the center of the lesion (r = 0.011, P = 0.17). The grade of THE-P mode was also not significantly correlated with the distance from the EUS probe to the center of the lesion (r = 0.062, P = 0.45). The grade of THE-R mode was inversely and weakly correlated with the distance from the EUS probe to the center of the lesion (r = – 0.22, P = 0.0058).

Fig. 7

A 72-year-old man with cancer of the pancreatic head. The distance from the EUS probe to the lesion center was 3.5 cm. a Conventional B-mode imaging could visualize the distal side of the boundary of the lesion (arrows). b THE-P mode imaging could visualize the distal side of the boundary of the lesion, similar to B-mode imaging (arrows). c THE-R mode imaging could not clearly visualize the distal side of the boundary of the lesion (arrows).

Fig. 8

Correlation between mode grade and distance in pancreatic solid lesions The grade of the total image quality of B-mode was not significantly correlated with the distance from the EUS probe to the center of the lesion (r = – 0.047, P = 0.76). The grade of THE-P mode was also not significantly correlated with the distance from the EUS probe to the center of the lesion (r = 0.027, P = 0.86). On the other hand, the grade of THE-R mode was inversely and weakly correlated with the distance from the EUS probe to the center of the lesion (r = – 0.37, P = 0.0092).