**3. Materials and methods**

The study was approved by the Ethics Committee of 'The Russian Medical Academy of Continuing Professional Education' of the Health Ministry of the Russian Federation and the Ethics Committee of the Chelyabinsk Regional Children Clinical Hospital. Written informed consent of legal representatives was obtained for all patients. Liver biopsy was not included in the algorithm of examination of patients with cystic fibrosis. Ultrasound examination was performed by an Aixplorer device (Supersonic Imagine, France) with a broadband convex sensor operating in the frequency range of 1–6 MHz. A standard ultrasound examination of the liver, supplemented by two-dimensional shear wave elastography, was performed in 232 children. There were 200 healthy children aged 3 to 18 years (control group) and 32 patients with cystic fibrosis aged 2 to 17 years (study group) among them.

The control group included healthy children. The following criteria were taken into account:


*Shear Wave Elastography in the Assessment of Liver Changes in Children with Cystic Fibrosis DOI: http://dx.doi.org/10.5772/intechopen.103185*


The diagnosis of cystic fibrosis was established on the basis of a comprehensive clinical and laboratory examination with history data analysis, DNA diagnostics with genotype specification, and it was confirmed by a positive sweat test. The course of the disease in 17 (53.1%) children was regarded as moderate (subgroup I), in 15 (46.9%) children – as severe (subgroup II). The severity of the disease course was assessed by the Schwachman-Brasfield scale, modified by S.V. Rachinsky and N.I. Kapranov. This scale takes into account the general activity of the patient, state of his nutrition and physical development, clinical manifestations of the disease, as well as the results of X-ray examination [32].

After a standard ultrasound examination of the abdominal organs in the grayscale mode, the stiffness of different segments of the right liver lobe was measured in the areas free of vascular structures at a depth of 3–5 cm from the capsule. The study was performed fasting, the patients breathing calmly, the older children holding breath for no more than 10 seconds or during shallow inhalation, in a supine position. The sensor was positioned perpendicular to the body surface with minimal manual pressure, using subcostal, intercostal and epigastric approaches. The area of interest (colour window) was selected, the image stabilization was set, the measurement was considered successful if more than 90% of the colour window was filled with colour. Ten measurements of the average value of the Young modulus (Emean) (kPa) were performed, and according to the results, the arithmetic mean value of Emean was calculated. Examples of liver stiffness assessment in patients of both groups are shown in **Figures 1–4**.

#### **Figure 1.**

*An example of stiffness assessment of unchanged liver parenchyma in a healthy child: B-mode and twodimensional shear wave elastography mode. The results of one of 10 measurements. Emean = 4.4 kPa. The child is 10 years old.*

#### **Figure 2.**

*An example of liver stiffness assessment in a child with cystic fibrosis: B-mode and two-dimensional shear wave elastography mode. The results of one of 10 measurements. Emean = 5.6 kPa. The child is 13 years old.*

#### **Figure 3.**

*An example of liver stiffness assessment in a child with cystic fibrosis: B-mode and two-dimensional shear wave elastography mode. Emean = 11.2 kPa. The child is 11 years old.*
