ARRT Sonography key terms

An acronym meaning as low as reasonably achievable; the guiding principle that ultrasound exposure should be kept to the minimum needed to obtain diagnostic information, balancing image quality against potential bioeffects.

A displayed value estimating the potential for tissue heating from absorbed ultrasound energy; it compares expected temperature rise to a reference and rises with higher output and longer exposure.

A displayed value estimating the likelihood of cavitation and mechanical bioeffects from peak rarefactional pressure relative to ultrasound frequency; higher values indicate greater potential for tissue disruption.

Infection-control practices applied to all patients regardless of diagnosis, including hand hygiene, gloves, and protection from blood and body fluids, to prevent transmission of pathogens during sonographic examinations.

A process that destroys most microorganisms, including some spores, on semi-critical devices such as endocavitary transducers; it requires approved chemical germicides and appropriate contact time after cleaning.

A supine position with the head lowered and legs elevated; used in sonography to shift abdominal organs and fluid, improve venous return, or help visualize pelvic structures.

A forced exhalation against a closed airway that raises intra-abdominal pressure; used during pelvic or abdominal scanning to demonstrate prolapse, reflux, or changes in venous flow.

The property of certain crystals to deform when an electric voltage is applied and to generate voltage when mechanically deformed; this conversion underlies transducer transmission and reception of sound.

The resistance of a medium to sound passage, determined by tissue density and propagation speed; differences in impedance at interfaces cause reflections that form ultrasound images.

The reduction in sound beam intensity as it travels through tissue due to absorption, reflection, and scattering; higher-frequency beams attenuate more rapidly, limiting penetration depth.

The ability to distinguish two reflectors lying along the beam path, determined mainly by spatial pulse length; shorter pulses and higher frequencies improve it, typically to a fraction of a millimeter.

The ability to separate two reflectors side by side perpendicular to the beam; it depends on beam width and is best at the focal zone.

The maximum Doppler frequency shift that can be correctly displayed without aliasing, equal to half the pulse repetition frequency; shifts above this threshold wrap to the opposite direction.

An artifact in pulsed-wave or color Doppler in which blood velocities exceeding the Nyquist limit appear as reversed or wrap-around colors; it can be corrected by adjusting scale, baseline, or frequency.

A control that selectively amplifies returning echoes according to depth to counteract attenuation, allowing deeper structures to appear with similar brightness to superficial ones.

Enlargement of the liver beyond normal dimensions; sonographically suggested when the liver extends below the right kidney or spans an increased craniocaudal length, often with rounded inferior margins.

Abnormal accumulation of fat within liver cells; at ultrasound the liver appears diffusely echogenic, often brighter than the kidney, and deep structures may be poorly seen.

The presence of gallstones in the gallbladder; typically seen as mobile echogenic foci with posterior acoustic shadowing, sometimes associated with wall thickening or sludge.

Dilation of the renal collecting system caused by urine obstruction or reflux; appears as anechoic fluid branching within the kidney, separating the central sinus echoes.

A focal enlargement of the abdominal aorta, generally defined as a diameter greater than 3 cm; ultrasound measures the outer-to-outer wall and checks for mural thrombus.

Abnormal accumulation of free fluid in the peritoneal cavity; appears as anechoic areas around organs and bowel, and can be graded or sampled by ultrasound guidance.

Enlargement of the spleen beyond normal size; sonographic assessment includes craniocaudal length, thickness, and volume, with common thresholds around 12–13 cm in adults.

The first visible sign of early pregnancy, a fluid-filled structure within the endometrium; its location, shape, and contents help confirm intrauterine pregnancy and estimate gestational age.

The measurement of the embryo or fetus from head to rump in early pregnancy; it is the most accurate sonographic method for dating between roughly 7 and 13 weeks.

A fetal head measurement taken across the parietal bones at a standard axial plane; used with other parameters to estimate gestational age, weight, and head growth.

A condition in which the placenta covers or lies very close to the internal cervical os; diagnosed by transvaginal ultrasound and associated with bleeding risk near delivery.

A semiquantitative estimate of amniotic fluid obtained by summing the deepest vertical pocket in each of four uterine quadrants; used to assess oligohydramnios or polyhydramnios.

Implantation of a pregnancy outside the uterine cavity, most often in a fallopian tube; sonographic clues include an adnexal mass and empty uterus with elevated hCG.

The central echogenic interface of the endometrium seen on transvaginal ultrasound; its thickness and appearance change with the menstrual cycle and help evaluate bleeding or fertility.

A discrete lesion within the thyroid gland; ultrasound characterizes size, echogenicity, margins, calcification, and shape to estimate malignancy risk and guide biopsy.

A common benign breast mass composed of fibrous and glandular tissue; typically oval, well-circumscribed, and hypoechoic, often with smooth margins and homogeneous echotexture.

A collection of fluid between the layers of the tunica vaginalis around the testicle; appears as an anechoic area surrounding the testis and is usually benign.

Twisting of the spermatic cord that compromises blood flow to the testis; an emergent condition requiring prompt diagnosis, often with absent or reduced Doppler flow.

A blood clot within a deep vein, commonly in the lower extremity; compression ultrasound showing a noncompressible vein is the primary sonographic sign.

Abnormal dilation of the pampiniform venous plexus, usually left-sided; seen as multiple tortuous anechoic tubes that enlarge with Valsalva and may show reflux on Doppler.

A small immune structure often evaluated with ultrasound; benign nodes are typically oval with a thin cortex and fatty hilum, while rounded, hypoechoic nodes raise concern.