Acoustic Radiation Force Impulse imaging of the kidney – a pilot study

Purpose: To establish Acoustic Radiation Force Impulse (ARFI) imaging on the human kidneys using the Philips ultrasound system iU 22. The first goal of this study was to define the measuring location with the least variation of ARFI results. The further aim is to establish ARFI Imaging as a non-invasive surrogate marker to evaluate kidney parenchymal stiffness and kidney function.

Material and methods: 20 healthy volunteers (age range 21 – 32 years) underwent ultrasound elastography on their kidneys with ARFI. We used the Philips iU 22 ultrasound system with a C5 – 1 MHz curved array probe. On both the right and left kidney the upper pole, the lower pole, and the parenchyma around the hilus were examined in two sections – longitudinal and axial. 10 measurements were perfomed in each region and their median was built.

Results: Intraclass-correlation is a statistical method to show the most agreement between the ten measurement in one region also the measurements of al 20 volunteers in this region. For this study, the best agreement was observed performing the ARFI Imaging in the parenchyma around the hilus of the kidney in a longitudinal section. The mean ARFI values in ths Position were 1.61 m/s (± 0.40 m/s) for the right, and 1.61 MS (± 0.44 m/s) for the left kidney.

Conclusion: Kidney parenchyma of the hilus region showed the least variation in ARFI values. So, this position will be used for sampling elastography data in the next step of our study. Healthy adults have values around 1.61 m/s. We expect to have a change in ARFI values in children with solitary kidneys compared to healthy children.