3.2.1. Ultrasonography (1960’s). In this modality, a transmitter sends high frequency
sound waves into the body where they bounce off the different tissues and
organs to produce distinctive patterns of echoes. These echoes are acquired by
a receiver and forwarded to a computer that translates them into an image on a
screen. Because ultrasound can distinguish subtle variations among soft, fluid-filled
tissues, it is particularly useful in imaging the abdomen. In contrast to X-rays, ultrasound
does not damage tissues with ionizing radiation. The great disadvantage
of ultrasonography is that it produces very noisy images. It may therefore be hard
to distinguish smaller features (such as cysts in breast imagery). Typically quite a
bit of image preprocessing is required. See Figure