Age-related changes in liver, kidney, and spleen stiffness in healthy children measured with acoustic radiation force impulse imaging

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Abstract

Objectives

To evaluate the feasibility and age-related changes of shear wave velocity (SWV) in normal livers, kidneys, and spleens of children using acoustic radiation force impulse (ARFI) imaging.

Materials and methods

Healthy pediatric volunteers prospectively underwent abdominal ultrasonography and ARFI. The subjects were divided into three groups according to age: group 1: <5 years old; group 2: 5–10 years old; and group 3: >10 years old. The SWV was measured using a 4–9 MHz linear probe for group 1 and a 1–4 MHz convex probe for groups 2 and 3. Three valid SWV measurements were acquired for each organ.

Results

Two hundred and two children (92 male, 110 female) with an average age of 8.1 years (±4.7) were included in this study and had a successful measurement rate of 97% (196/202). The mean SWVs were 1.12 m/s for the liver, 2.19 m/s for the right kidney, 2.33 m/s for the left kidney, and 2.25 m/s for the spleen. The SWVs for the right and left kidneys, and the spleen showed age-related changes in all children (p < 0.001). And the SWVs for the kidneys increased with age in group 1, and those for the liver changed with age in group 3.

Conclusions

ARFI measurements are feasible for solid abdominal organs in children using high or low frequency probes. The mean ARFI SWV for the kidneys increased according to age in children less than 5 years of age and in the liver, it changed with age in children over 10.

Introduction

Acoustic radiation force impulse (ARFI) imaging is a new, non-invasive method for quantifying tissue stiffness that can be performed in real-time during ultrasound examination. This technique is based on the emission of short-duration acoustic pulses into tissues that induce localized tissue displacement, resulting in shear wave propagation away from the region of excitation [1]. The shear wave speed can be detected as ultrasonic waves, and is measured in m/s and is proportional to the square root of tissue stiffness.

Numerous studies have used the ARFI technique to measure the stiffness of organs in adults. These studies were mainly performed in the liver to evaluate hepatic fibrosis, and were extended to patients with non-alcoholic fatty liver disease and patients with ascites. Other organs have also been evaluated using this technique, including the thyroid [2], prostate [3], pancreas [4], and transplanted kidneys [5]. However, these studies were all performed in adults and little is known about the feasibility and utility of ARFI measurements in children.

Recently, a high-frequency linear transducer was developed for ARFI, however this has only been applied to breast and thyroid lesions [2], [6]. This probe may also be suitable for the evaluation of abdominal solid organs in young children.

The purpose of this prospective study was to evaluate the feasibility of performing ARFI shear wave velocity (SWV) measurements on normal livers, kidneys, and spleens of healthy children using high-frequency and low-frequency probes, and to evaluate the effects of age on the ARFI SWV of each organ.

Section snippets

Study subjects

This prospective study was approved by the Institutional Review Board of our hospital. The parents of all study subjects and older children provided informed consent. Healthy pediatric volunteers less than 18 years of age without any medical history or present illness were enrolled and underwent abdominal ultrasonography and ARFI between July 2011 and August 2011. Body weight and height were recorded on the day of the study. Body mass index (BMI) was calculated as weight (kg)/height (m)2.

All

Results

Two hundred and seventeen children underwent abdominal ultrasonography. Fifteen children were subsequently excluded because of incidental pathologic findings (fatty liver in seven, renal cysts in two, and hydronephrosis in six). A total of 202 children (girls = 110, boys = 92) were ultimately enrolled and the mean age was 8.1 ± 4.7 years. Age, height, weight, and BMI were not significantly different between males and females (Table 1). There were 59 children in group 1, 77 children in group 2, and 66

Discussion

There have been many studies on the utility of ARFI imaging, however most of these studies were performed with adult populations. There is no standardized protocol for ARFI SWV measurements with regard to frequency, measurement depth, or acquisition number. Therefore, the first goal of our study was to evaluate the feasibility of ARFI SWV measurement in children of varying age.

Previous studies have largely used a low frequency convex transducer for measurements in adults and children [7]. In

Conclusions

ARFI SWV measurements are feasible for solid abdominal organs in children using high frequency or low frequency probes and the ARFI SWVs showed age-related changes in these organs. The mean ARFI SWV for the kidneys increased according to age in children less than 5 years of age and changed with age in the liver in children aged over 10 years. The spleen showed age-related changes in all children.

References (19)

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