Measurement of Probe Angle for Ultrasound Evaluation of Articular Cartilage Using “Rise-to-Peak Time”

Abstract

Background. Ultrasound evaluation of articular cartilage is not accurate if the ultrasound probe is not perpendicular to the cartilage surface. However a probe angle adjustment is difficult because of the manual procedure and the lack of angle index for the measurer. The aim of this study is to propose “Rise-to-Peak time” as an index of probe angle and to evaluate its effectiveness in evaluating articular cartilage surfaces. Methods. The “Rise-to-Peak time” is defined as the time interval between the rise of the first peak (50% amplitude of the first peak) and the first positive peak following the minimum peak of the echo. The relationship between the Rise-to-Peak time and probe angle was evaluated using several reflection surfaces including that of articular cartilage. Findings. The “Rise-to-Peak time” increased monotonically with increases in the angle between the probe and the reflection surface, and showed good agreement with calculated values for small angle changes (<3 degrees). Interpretation. The “Rise-to-Peak time” provides an index of probe angle in the ultrasound measurement of articular cartilage. Availability of echo-amplitude correction using the “Rise-to-Peak time” is evaluated.

Keywords

• ultrasound
• cartilage
• evaluation
• measurement support