# Comparison of filter-based and software-based image enhancement systems for endoscopic swallowing diagnostics: a head-to-head study

## TL;DR

This study compares two image enhancement systems for endoscopic swallowing diagnostics and finds they both improve visibility of food dyes, with preferences depending on color and user choice.

## Contribution

The study provides a direct comparison of NBI® and PIET® systems for enhancing food dye visibility in FEES, revealing color-specific preferences and similar overall effectiveness.

## Key findings

- Both NBI® and PIET® systems enhanced food dye visibility tenfold.
- PIET was preferred for red and purple dyes, while NBI was favored for yellow, green, and orange.
- Raters agreed 100% on maximum visible dilution across both systems.

## Abstract

Flexible endoscopic evaluation of swallowing (FEES) is a gold standard for diagnosing swallowing disorders. This study investigates two image enhancement technologies usable in FEES—hardware filtering (Narrow Band Imaging, NBI®) and software filtering (Professional Image Enhancement Technology, PIET®)—to assess their effectiveness in improving the visibility of food dyes.

This Head-to-head study compared NBI® and PIET® by creating 190 videos showcasing food dyes diluted from 1:10 to 1:100,000, tested in the oral cavities of four volunteers. Four raters evaluated the maximum visible dilution for both systems across all colors. Sixteen snippets representing eight colors (red, yellow, blue, green, purple, orange, black, and white) at a 1:10 dilution were analyzed by 14 raters, including two with no prior FEES experience, all blinded to the filtering method.

The study used a point system to assess subjective image quality, color intensity, and contrast to the mucosa. Both systems produced similar hues for yellow and red and their secondary colors. PIET was preferred for red and purple, while NBI was favored for yellow, green, and orange. For blue, black, and white (all showing no intensification), PIET was nearly unanimously chosen. Raters agreed 100% on the maximum visible dilution, showing no significant difference between systems; both enhanced visibility tenfold.

Both image enhancement systems improved the visibility of specific food dyes effectively. Each method has distinct advantages. The choice between them depends on personal preference and available systems.

The online version contains supplementary material available at 10.1007/s00405-025-09413-w.