I find solution for my issue:
public static BitmapImage Base64StringToBitmap(string base64String)
{
byte[] byteBuffer = Convert.FromBase64String(base64String);
MemoryStream memoryStream = new MemoryStream(byteBuffer);
memoryStream.Position = 0;
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.SetSource(memoryStream);
memoryStream.Close();
memoryStream = null;
byteBuffer = null;
return bitmapImage;
}