Hemodynamics and Ultrasound Principles

Vocabulary flashcards covering key hemodynamics, Doppler physics, and digital imaging concepts from the lecture.

Harmonics

Sound waves created within the tissues that vibrate at twice the fundamental frequency.

Flow (Volume Flow Rate)

The volume of blood moving during a particular time, commonly measured in units such as liters per minute.

Velocity

The speed of fluid movement, calculated as distance divided by time (such as $\text{cm/s}$), answering the question of how fast blood is moving.

Pulsatile Flow

Blood flow that accelerates and decelerates in arteries as a result of cardiac contraction.

Phasic Flow

Venous blood flow (also termed spontaneous flow) that changes in velocity in response to respiration.

Steady Flow

Flow that occurs when fluid moves at a constant speed or velocity, present in venous circulation when respiration ceases and absent in arterial circulation.

Laminar Flow

Layered, silent flow patterns characterized by parallel streamlines commonly associated with normal physiological blood flow.

Plug Flow

A form of laminar flow where all layers of blood travel at the same velocity.

Parabolic Flow

A form of laminar flow with a bullet-shaped profile where velocity is highest in the center of the vessel and decreases toward the vessel walls.

Turbulent Flow

Chaotic blood flow characterized by swirling currents, multiple directions, and many speeds, commonly occurring downstream from a narrowing.

Eddy Current

Another technical term used to describe turbulent flow.

Bruit

An abnormal sound heard with a stethoscope in a vessel, such as a carotid artery, produced by turbulent blood flow.

Murmur

An abnormal sound heard in the heart caused by turbulent flow.

Thrill

A palpable murmur or tissue vibration that can be felt by hand due to turbulent blood flow.

Reynolds Number

A dimensionless number predicting flow character, where values less than $1,500$ indicate laminar flow and values greater than $2,000$ indicate turbulent flow.

Wall Filter (High Pass Filter)

A Doppler control used to eliminate low-frequency, low-velocity flow signals along the baseline.

Spectral Broadening

The filling in of the spectral window on a Doppler display caused by increased velocity and multiple directions of flow.

Energy Gradient

The force created by blood moving through a closed circulatory system that enables fluid to move from one location to another.

Kinetic Energy

Energy associated with a moving object, determined by the object's mass and speed.

Pressure Energy

A form of potential or stored energy that provides the ability to perform work.

Gravitational Energy

A form of stored potential energy associated with an elevated object.

Viscous Energy Loss

Energy loss resulting from the thickness of a fluid, determined in blood by the hematocrit.

Hematocrit

The percentage of whole blood volume composed of red blood cells, normally approximately $45\%$.

Inertia

The tendency of fluid to maintain the status quo and resist changes in velocity, resulting in energy losses during pulsatile flow, phasic flow, or stenosis.

Stenosis

The narrowing of the lumen of a blood vessel.

Coaptation

The complete collapse of a vessel wall associated with changes in venous volume and pressure.

Hydrostatic Pressure

Pressure related to the weight of blood pressing on a vessel; it is equal to $0$ at all body locations when a patient is in a supine position.

Pixel

The smallest unit of a digital picture, directly related to spatial resolution.

Bit

The smallest unit of digital computer memory, where the total number determines shades of gray ($2^n$) and contrast resolution.