Visualizing the gastric wall with a 30-MHz ultrasonic miniprobe: ex vivo imaging of normal gastric sites and sites of early gastric cancer.

Background: This study was performed to determine the echo layer structures of the normal gastric wall and early gastric cancer when visualized with a 30-MHz ultrasonic miniprobe.

Methods: Twelve surgically resected gastric specimens were used for an ex vivo study. Eighteen normal sites and 12 early gastric cancer sites were scanned with an Olympus (XUM-S30-25R) probe with a frequency of 30-MHz. Endoscopic ultrasound images were compared with corresponding histopathologic sections stained with hematoxylin and eosin.

Results: The normal mucosa was visualized as at least four alternating echo layers; the muscularis mucosa was delineated at all normal sites. Lymphoid aggregates within the mucosa could be seen. The submucosa was clearly visualized in most cases, but the muscularis propria and subserosa were seldom depicted due to attenuation of ultrasound waves. At the sites of gastric cancer, the layered architecture of the mucosa was disturbed by an irregular hypoechoic lesion. Minimal submucosal infiltration (400 and 750 micrometer) was clearly depicted in two cases, without ulceration at or around the tumor site. However, attenuation at the site of a deep ulcer scar prevented adequate visualization of the tumor extent in two other cases with ulceration.

Conclusion: A 30-MHz ultrasonic miniprobe may provide additional imaging information of the gastric wall and could play a role in the assessment of early cancer lesions.