RDCS Pediatric key terms

The ability of ceramic crystals inside a transducer to change shape when a voltage is applied and to generate a voltage when struck by returning sound, so a single element both transmits and receives ultrasound.

The smallest separation along the beam direction at which two reflectors can still be seen as distinct; it equals half the spatial pulse length, so higher frequency and shorter pulses improve it.

A displayed number estimating cavitation risk, derived from peak negative pressure divided by the square root of frequency; the higher the value, the greater the potential for bubble formation, so it is kept low.

An on-screen estimate of how much tissue temperature could rise from absorbed ultrasound energy; a value of one corresponds roughly to a one degree Celsius increase and prompts the user to reduce output.

As Low As Reasonably Achievable: using the least acoustic output and shortest scanning time that still produces diagnostic images, a habit especially important for children facing decades of potential future exposure.

The highest Doppler frequency shift a pulsed system can record unambiguously, equal to half the pulse repetition frequency; deep sample sites and fast jets push the shift past this boundary.

Wrapping of a Doppler signal that exceeds the Nyquist limit, so the peak appears on the opposite side of the baseline; raising the velocity scale, shifting the baseline, or switching to continuous wave corrects it.

Doppler in which one crystal transmits while another receives without interruption, measuring very high velocities free of aliasing but without depth discrimination, since signal can arise anywhere along the cursor line.

The shortcut stating that pressure gradient equals four times the square of peak velocity, converting a Doppler velocity into a pressure difference across a valve, septal defect, or narrowing.

A one-dimensional trace of moving structures along a single cursor line, offering excellent temporal resolution for timing valve motion, measuring chamber dimensions, and catching rapid leaflet or septal movement.

A systematic method of describing any heart by situs, ventricular looping, and the connections of atria to ventricles and ventricles to great arteries, so complex malformations can be named consistently.

The arrangement of abdominal organs and atria as solitus (normal), inversus (mirrored), or ambiguus; it is the first step of segmental analysis and predicts atrial and often ventricular position.

The direction in which the embryonic heart tube bends, with a D-loop placing the right ventricle on the right and an L-loop placing it on the left, fixing ventricular position independently of atrial situs.

A flap-like fetal opening between the atria that lets oxygenated umbilical blood reach the left heart; it normally seals after birth but may remain probe-patent or enlarge into a true septal defect.

A fetal vessel joining the pulmonary artery to the descending aorta so blood bypasses the unventilated lungs; it usually constricts within days of birth but may persist as a patent ductus.

At birth, lung expansion and loss of placental flow lower pulmonary vascular resistance and raise systemic resistance, reversing the ductal shunt, closing fetal channels, and greatly increasing pulmonary blood flow.

A hole in the ventricular septum creating a left-to-right shunt whose size and gradient determine symptoms; perimembranous and muscular defects are most common, and many small ones close spontaneously.

An opening in the atrial septum allowing left-to-right flow that volume-loads the right heart; secundum defects are most frequent, and the murmur is often soft and easy to miss in children.

Persistence of the fetal aortic-pulmonary connection after birth, producing a continuous left-to-right shunt with a machinery murmur; it is common in premature infants and closed when hemodynamically significant.

A cyanotic lesion defined by a ventricular septal defect, overriding aorta, right ventricular outflow obstruction, and right ventricular hypertrophy; the severity of outflow narrowing governs how blue the child appears.

A cyanotic lesion in which the aorta arises from the right ventricle and the pulmonary artery from the left, creating parallel circulations that survive only through mixing at a septal defect or ductus.

A cyanotic lesion in which all pulmonary veins drain into a systemic vein rather than the left atrium, obligating an atrial septal defect; obstruction at the connection causes severe neonatal distress.

Severe underdevelopment of the left ventricle, mitral and aortic valves, and ascending aorta, so the right ventricle supplies the body through the ductus; survival depends on ductal patency and staged surgical palliation.

A narrowing, usually near the ductal site, that causes upper-body hypertension and a pressure difference between arms and legs; it may present in infancy or be found later in childhood.

A lesion combining an atrial septal defect, a ventricular septal defect, and a common atrioventricular valve, strongly associated with Down syndrome; the shared valve causes both shunting and regurgitation.

The ratio of pulmonary to systemic blood flow, derived from ventricular outflows or shunt velocities; a value above roughly 1.5 indicates a hemodynamically important left-to-right shunt worth considering for closure.

Irreversible pulmonary vascular disease from a long-standing large left-to-right shunt that raises pulmonary pressure until flow reverses or becomes bidirectional, causing cyanosis and making simple defect closure unsafe.

A disorder with a dilated, poorly contracting left or both ventricles and reduced ejection fraction, producing heart failure; pediatric causes include myocarditis, familial disease, and idiopathic forms.

Unexplained thickening of ventricular muscle, often asymmetric in the septum, with a small cavity and sometimes dynamic outflow obstruction; it is a leading cause of sudden death in young athletes.

An acute vasculitis of childhood that inflames and dilates the coronary arteries, causing aneurysms, thrombosis, and later ischemia; echocardiography measures coronary size serially against normal values.

A quick M-mode or two-dimensional measure of left ventricular systolic performance: end-diastolic minus end-systolic dimension divided by end-diastolic dimension; it is load dependent and assumes uniform contraction.

Also called myocardial performance index, it combines isovolumic contraction and relaxation times with ejection time into one number reflecting global ventricular function, and is less load dependent than ejection fraction.

A method that follows natural ultrasound speckles through the cardiac cycle to measure myocardial deformation, revealing regional dysfunction earlier than ejection fraction; global longitudinal strain is the value most often reported.

The number of standard deviations a measurement lies from the normal mean for a child's body surface area or age, letting valve, vessel, and coronary sizes be judged against pediatric normative data.

The view obtained from below the ribs using the liver as a window, giving excellent images of the atrial septum, pulmonary veins, and abdominal aorta in infants and small children.

A palliative tube graft from the subclavian or innominate artery to the pulmonary artery that increases pulmonary blood flow in cyanotic newborns; echocardiography checks its patency, flow, and any narrowing.

A staged surgical pathway sending systemic venous blood directly to the pulmonary arteries without a ventricular pump, usually through an extracardiac conduit; imaging focuses on conduit patency, fenestration flow, and ventricular function.

Supervised drug-induced calm used when a child cannot cooperate, requiring fasting, continuous monitoring, and recovery observation; agent choice follows institutional protocol and consent is obtained from the caregiver.