Reflux sonography, as an alternative to micturating cystography (MCU), evaluates vesico-ureteral reflux (VUR), a common problem in children. Contrast enhanced pulse-inversion imaging shows best results. During the instillation of an ultrasound contrast agent into the bladder, (as for a conventional MCU) the lower ureters and renal pelves are scanned transabdominally as the bladder is filled to stimulate micturition.
Advantages for reflux sonography are a high sensitivity and the avoidance of X-rays. A disadvantage is the poorer depiction of the posterior urethra. However, for girls and for all follow-up studies, the ultrasound MCU has become standard in many pediatric ultrasound departments.

See also Urologic Ultrasound, Kidney Ultrasound, Ultrasound Safety, Ultrasound Imaging Modes.

The transorbital window allow to insonate ophthalmic artery and ipsilateral carotid siphon through the eye. It is also possible to use the transorbital entrance to scan the middle and anterior cerebral arteries, if it is impossible through the transtemporal window.
The patient is asked to remove any contact lenses prior to examination and is instructed to close the eyes. The power output of the Doppler instrument has to be decreased to 10-20% to reduce the ultrasonic exposure of the eye.

See also Transcranial Doppler, Ultrasound Safety.

(US) Also called echography, sonography, ultrasonography, echotomography, ultrasonic tomography.
Diagnostic imaging plays a vital role in modern healthcare, allowing medical professionals to visualize internal structures of the body and assist in the diagnosis and treatment of various conditions. Two terms that are commonly used interchangeably but possess distinct meanings in the field of medical imaging are 'ultrasound' and 'sonography.'
Ultrasound is the imaging technique that utilizes sound waves to create real-time images, while sonography encompasses the entire process of performing ultrasound examinations and interpreting the obtained images. Ultrasonography is a synonymous term for sonography, emphasizing the use of ultrasound technology in diagnostic imaging. A sonogram, on the other hand, refers to the resulting image produced during an ultrasound examination.
Ultrasonic waves, generated by a quartz crystal, cause mechanical perturbation of an elastic medium, resulting in rarefaction and compression of the medium particles. These waves are reflected at the interfaces between different tissues due to differences in their mechanical properties. The transmission and reflection of these high-frequency waves are displayed with different types of ultrasound modes.
By utilizing the speed of wave propagation in tissues, the time of reflection information can be converted into distance of reflection information. The use of higher frequencies in medical ultrasound imaging yields better image resolution. However, higher frequencies also lead to increased absorption of the sound beam by the medium, limiting its penetration depth. For instance, higher frequencies (e.g., 7.5 MHz) are employed to provide detailed imaging of superficial organs like the thyroid gland and breast, while lower frequencies (e.g., 3.5 MHz) are used for abdominal examinations.

Ultrasound in medical imaging offers several advantages including:

Diagnostic ultrasound imaging is generally considered safe, with no adverse effects. As medical ultrasound is extensively used in pregnancy and pediatric imaging, it is crucial for practitioners to ensure its safe usage. Ultrasound can cause mechanical and thermal effects in tissue, which are amplified with increased output power. Consequently, guidelines for the safe use of ultrasound have been issued to address the growing use of color flow imaging, pulsed spectral Doppler, and higher demands on B-mode imaging. Furthermore, recent ultrasound safety regulations have shifted more responsibility to the operator to ensure the safe use of ultrasound.

See also Skinline, Pregnancy Ultrasound, Obstetric and Gynecologic Ultrasound, Musculoskeletal and Joint Ultrasound, Ultrasound Elastography and Prostate Ultrasound.

Regulations governing the output of diagnostic ultrasound have been largely set by the USA's Food and Drug Administration (FDA), although the International Electrotechnical Commission (IEC) is currently in the process of setting internationally agreed standards.
The relevant national societies for ultrasound users (e.g. American Institute of Ultrasound in Medicine (AIUM), British Medical Ultrasound Society (BMUS)) usually have safety committees who offer advice on the safe use of ultrasound. In 1992, the AIUM, in conjunction with the National Electrical Manufacturers Association (NEMA) developed the Output Display Standard (ODS), including the thermal index and mechanical index which have been incorporated in the FDA's new regulations.
Within Europe, the Federation of Societies of Ultrasound in Medicine and Biology (EFSUMB) also addresses safety and has produced safety guidelines (through the European Committee for Ultrasound Radiation Safety). The World Federation (WFUMB) held safety symposia in 1991 (on thermal issues) and 1996 (thermal and non-thermal issues), at which recommendations were proffered.
The FDA ultrasound safety regulations from 1993 combine an overall limit of spatial peak time averaged intensity (I-SPTA) of 720 mW/cm2 for all equipment. A system of output displays allows users to employ effective and judicious levels of ultrasound appropriate to the examination. The output display is based on two indices, the mechanical index (MI) and the thermal index (TI).

See also ALARA Principle, and Radiological Society of North America.

The various gas microbubble contrast media are generally safe with low toxicity in humans. The tolerance of these agents is much higher than that of most x-ray agents, a reflection perhaps of the higher expectation of safety and convenience for ultrasound.
Extensive preclinical and clinical trials have demonstrated an excellent ultrasound contrast agent safety profile, the main side effect being a mild and transient local discomfort at the injection site which results from the high osmolality of these agents. Each contrast agent has its own profile of adverse effects, but all have been trivial thus far.

See also Ultrasonic Contrast Agents.