Ultrasound Glossary

Pyelonephritis is a kidney infection that may show as enlarged, swollen kidneys with increased blood flow on ultrasound.

Pyloric stenosis is a thickening of the pylorus muscle in infants that causes projectile vomiting, diagnosed by ultrasound.

The quadriceps tendon connects the quadriceps muscles to the kneecap and is evaluated by ultrasound for tears and tendinopathy.

The radial artery is a major artery of the forearm, palpable at the wrist, and evaluated by ultrasound for patency and suitability for vascular access.

Registered Diagnostic Cardiac Sonographer — an ARDMS credential for cardiac sonographers (echocardiographers).

Registered Diagnostic Medical Sonographer — a credential awarded by ARDMS to sonographers who pass specialty examinations.

Ultrasound images that update continuously as you move the transducer, allowing you to see live movement of organs and structures. This is what makes ultrasound useful for watching how things move.

A refractive artifact occurs when the ultrasound beam bends at a tissue boundary, causing structures to appear duplicated or displaced.

The renal artery supplies blood to the kidney and is evaluated by Doppler ultrasound for stenosis and flow abnormalities.

Narrowing of the renal artery, evaluated with Doppler ultrasound by measuring peak systolic velocity and acceleration time in the renal vessels.

A kidney stone appearing as a hyperechoic focus with posterior acoustic shadowing on renal ultrasound.

Renal cell carcinoma is the most common kidney cancer in adults, often detected incidentally as a solid mass on ultrasound.

A renal cyst is a fluid-filled sac in the kidney, one of the most common incidental findings on abdominal ultrasound.

The renal parenchyma is the functional tissue of the kidney, assessed on ultrasound for thickness, echogenicity, and disease.

The renal pelvis is the funnel-shaped collecting area at the center of the kidney, evaluated by ultrasound for dilation indicating obstruction.

A renal transplant is a surgically placed donor kidney, monitored closely with Doppler ultrasound for vascular and parenchymal complications.

The renal vein drains blood from the kidney and is assessed by ultrasound for thrombosis and flow abnormalities.

A Doppler-derived ratio reflecting downstream vascular resistance, calculated as (PSV − EDV) / PSV.

Resistive Index (RI): Doppler ratio = (PSV − EDV) / PSV; measures vascular resistance; elevated in renal obstruction, transplant rejection, and parenchymal disease. The resistive index (RI) is a dimensionless Doppler-derived ratio calculated as (PSV − EDV) / PSV. It quantifies downstream vascular resistance and is used to assess renal parenchymal disease, transplant rejection, elevated…

The ability of an ultrasound system to distinguish two closely spaced structures as separate — includes axial, lateral, and temporal resolution.

Retained products of conception refers to tissue remaining in the uterus after pregnancy, diagnosed by ultrasound showing a thickened, echogenic endometrium.

Repeated parallel lines on ultrasound caused by sound bouncing back and forth between two highly reflective surfaces.

Rhabdomyolysis is the breakdown of muscle tissue that can cause kidney damage, with ultrasound used to evaluate both the affected muscles and kidneys.

A continuous streak of echoes trailing behind a gas bubble or crystalline structure, caused by resonating fluid layers.

A group of four muscles and tendons stabilizing the shoulder joint — the supraspinatus is the most commonly torn and evaluated on ultrasound.

A rotator cuff tear is a rip in one or more shoulder tendons, diagnosed by ultrasound as a defect in the tendon’s normal echogenic structure.

Registered Vascular Technologist — an ARDMS credential for sonographers specializing in vascular studies.

S/D Ratio: Doppler ratio of peak systolic to end-diastolic velocity; used primarily in umbilical artery surveillance for IUGR and placental insufficiency. The systolic-to-diastolic (S/D) ratio is a spectral Doppler measurement comparing peak systolic to end-diastolic velocity in a vessel. It is primarily used in obstetric Doppler assessment of the umbilical artery — a normal S/D…

An imaginary line that divides the body from front to back, creating left and right halves. A sagittal scan shows a side view of the body.

Salpingitis is inflammation of a fallopian tube, often seen on ultrasound as a fluid-filled, dilated tubular structure in the pelvis.

The adjustable gate in pulsed wave Doppler that defines the location and size of the region from which velocity information is sampled.

The seminal vesicles are paired glands behind the bladder that produce fluid for semen, visible on transrectal or transabdominal ultrasound.

SFU Grading System: 0–4 ultrasound grading scale for hydronephrosis based on pelvic/calyceal dilation and parenchymal thickness; grades 3–4 have higher surgical intervention rates. The Society for Fetal Urology (SFU) grading system is the standard ultrasound classification for hydronephrosis, graded 0–4 based on renal pelvis dilation, calyceal involvement, and parenchymal thickness. Grade 0 = normal; Grade…

A dark area deep to a strongly reflective or absorptive structure such as a stone or gas pocket.

Two opposite posterior acoustic artifacts used to characterize lesions: shadowing behind solid or calcified structures, enhancement behind fluid.

A quantitative elastography technique that measures tissue stiffness in kilopascals by tracking the speed of shear waves generated by acoustic radiation force.

A benign fluid-filled structure with characteristic ultrasound features: anechoic, thin walls, posterior acoustic enhancement.

A tissue-containing lesion on ultrasound that does not meet the criteria for a simple cyst, requiring further characterization.

Another term for elastography — ultrasound-based mapping of tissue stiffness using compression or shear wave techniques.

A healthcare professional trained to perform diagnostic ultrasound examinations.

Sonographic Murphy’s Sign: Maximum tenderness on direct ultrasound probe compression over the gallbladder; a positive sign supports the diagnosis of acute cholecystitis. The sonographic Murphy’s sign is maximal tenderness elicited by direct probe pressure over the sonographically identified gallbladder. It is a key diagnostic criterion for acute cholecystitis with a positive predictive value of ~92%…

Sonography is the use of high-frequency sound waves to create real-time images of the body’s internal structures for diagnostic purposes.

The foundational knowledge domain covering ultrasound physics, image formation, Doppler principles, artifacts, bioeffects, and quality assurance — tested on the ARDMS SPI exam.

An imaging technique that averages frames acquired from multiple beam angles to reduce speckle and improve tissue definition.

Speckle is the grainy texture seen on ultrasound images, caused by interference patterns of scattered sound waves within tissue.

Spectral Doppler is an ultrasound display that shows blood flow velocity over time as a waveform, used to analyze vascular and cardiac hemodynamics.

The graphical display of Doppler-detected blood flow velocities over time, showing systolic peaks, diastolic flow, and flow character.

A spermatocele is a benign, fluid-filled cyst near the top of the testicle, commonly found as an incidental finding on scrotal ultrasound.

SPI is an ARDMS exam on ultrasound physics and equipment. Learn about SPI exam content, cost, and preparation.

The Sonography Principles and Instrumentation exam — a required ARDMS prerequisite covering ultrasound physics and instrumentation.