A digital image analysis method for diagnostic ultrasound calibration

Acoustic test objects are commonly used for quality assurance testing of diagnostic ultrasound machines. However, the accompanying calibration protocols rely heavily on the judgment of the sonographer, are dependent on machine settings and are semi-quantitative. In the current study, two unique test objects and protocols were designed to quantitatively determine diagnostic ultrasound parameters, namely axial resolution and geometric uniformity, and lateral resolution and geometric uniformity of the ultrasound field. The effect of focal zone, signal gain, and distance from the ultrasound probe on these parameters was assessed. The investigation was performed using a typical low-frequency diagnostic unit equipped with a 7.5 MHz linear pulse-echo probe. Results underline the need to ensure that sensitivity of routine testing regimes is adequate for the measurements to be made. This study is a preliminary part of a larger project developing an ultrasound technique to be used as an engineering design tool in a non-clinical industrial setting for quality assurance testing of total knee replacements immersed in water.