Читать книгу Essential Endocrinology and Diabetes - Richard I. G. Holt - Страница 100

Ultrasound travels as sound waves beyond the range of human hearing and, according to the surface encountered, is reflected back towards the emitting source (the ultrasound probe). Different tissues have different reflective properties. By knowing the speed of the waves and the time between emission and detection, the distance between the reflective surfaces and the source can be calculated. These data allow a two‐dimensional image to be generated (Figure 4.6). The major advantage of ultrasound is its simplicity, safety and non‐invasiveness. Machines are portable. It is helpful as an initial imaging investigation of many endocrine organs. For instance, the thyroid has a characteristic appearance in Graves disease because of its increased vascularity (Chapter 8). The ovaries can be delineated transabdominally, or with specific consent, transvaginally, when the shorter distance between probe and ovary and fewer reflective surfaces create higher resolution images (Figure 4.6).