New method for internal anal sphincter measurements: feasibility study

Area of Science:

• Medical imaging analysis
• Gastroenterology
• Anorectal physiology

Background:

• Accurate measurement of the internal anal sphincter (IAS) is crucial for understanding anorectal function and dysfunction.
• Existing methods may lack the precision required for detailed morphological analysis.

Purpose of the Study:

• To present a novel method for quantitative analysis of the internal anal sphincter using three-dimensional (3D) endosonographic images.
• To develop software capable of calculating multiple measurements (thickness, length, area, volume) to describe the 3D shape of the IAS muscle.

Main Methods:

• A software tool was developed to perform quantitative analysis of 3D endosonographic images, calculating thickness, length, area, and volume of the IAS.
• Measurements were standardized using a common reference system and modeled spatially.
• The method's precision and reproducibility were validated using phantom models and subsequently tested on fifteen healthy patients by two independent operators.

Main Results:

• Phantom measurements showed high accuracy with minimal errors (e.g., thickness: 0.05 +/- 0.1 mm).
• Inter-observer variability was assessed, with most measurements showing good agreement.
• In vivo measurements for healthy patients yielded mean thickness of 1.71 +/- 0.34 mm, length of 33.24 +/- 6.10 mm, and area of 111.28 +/- 29.08 mm².

Conclusions:

• The developed 3D endosonography method offers satisfactory accuracy and precision for IAS measurements.
• The analysis confirms good inter-observer agreement for most IAS segments, with minor variability noted in specific regions.
• This quantitative approach enables detailed studies of IAS morphology.