Diagnostic ultrasounds are used to examine internal sections and organs in the body without x-rays or invasive surgery. When a patient goes for an ultrasound, a clear, jelly-like substance will be applied to the skin over the part of body being examined. A device that looks somewhat like a plastic knob will then be gently pressed against the body. This device sends high-frequency sound waves through the body that a computer then uses to produce images of the body. The procedure is painless and generally takes forty minutes to one hour.