Ultrasound can be used to examine the arterial system; the heart; the pancreas; the peritoneal cavity; the urinary tract; the ovaries; the venous system; the brain; and the spinal cord. When ultrasound is used to examine the heart, it is known as echocardiography. Echocardiography is used to study congenital heart disease, coronary artery disease, tumours of the heart, and other cardiac disorders. Ultrasound diagnostic can also be used to guide surgical procedures, for example during amniocentesis or the insertion of a biopsy needle into a particular area. Doppler ultrasound machines are used to measure the flow of a body liquid, for example blood flow. The best-known application of ultrasound machines is while the examination of the foetus during pregnancy. Unlike X-rays, ultrasound diagnostic is completely safe during pregnancy, with no risk to either mother or baby. It is used to monitor the growth, development, and well-being of the foetus, and can be used to check the due date. The size of the foetus's head can be measured to estimate its age. If twins are likely or if fertility drugs had been administered prior to conception, ultrasound may be used to confirm the number of foetuses present. It can be used to detect foetal abnormalities such as spina bifida, achondroplasia (short-limbed dwarfism), or severe congenital heart diseases, where in each case early diagnosis allows appropriate treatment to be given during the rest of pregnancy and at birth. Ultrasound machines also have a limited use in the treatment of various disorders of deep tissue and can be used to break up gallstones or stones in, for example, the kidney. They are also useful when used in conjunction with physiotherapy to treat soft-tissue damage and other injuries. Ultrasound machines are noninvasive, involve no emission, and avoid the possible hazard such as hemorrhage, contagion, or reactions to chemical of supplementary pinpointing methods. The ultrasound machine transmits high-frequency from 1 to 5 megahertz resonance pulses into the body, by means of a check out the resonance waves move into the body and strike a margin flanked by tissues, for instance flanked by liquid and yielding tissue, yielding tissue and fillet.In treating a patient, the physiotherapist may employ heat treatments; massage; manipulation; ultrasound, which is ultrasonic waves that produce heat internally; and diathermy (application of electric current to generate heat in body tissues). Other types of image are obtained by means of ultrasound machimes or MRI, or by recording the radioactivity of isotopes internally administered and deposited in specific body organs or organ systems. This latter practice, called nuclear radiology or nuclear medicine, includes such modern techniques as positron emission tomography (PET), which uses positron decay patterns to study metabolic reactions in body systems. Each technique has unique features that, under various conditions, make it more likely to reveal clearly the part to be examined. Thus, the radiologist has the opportunity to select-after consulting the attending doctor-the ultrasound diagnostic procedure or imaging modality best suited to meet the diagnostic needs of the patient. Unsurprisingly, an ultrasound machine for engineering use will be entirely dissimilar to the one viewed for corporeal treatment.