Diagnostic Ultrasound Instrumentation and Operational Modes

Ultrasound machine

Is an electronic imaging system that generates, receives, processes, and displays ultrasound signals

piezoelectric effect

The conversion of electrical energy into ultrasound waves and the conversion of returning echoes back into electrical signals occur within the ultrasound transducer through the ...

1. Piezoelectric crystal

2. Backing material

3. Matching layer

4. Acoustic lens

5. Physical housing

Parts of Ultrasound Transducer:

Piezoelectric crystal

heart of transducer

Jacques and Pierre Curie

Piezoelectric crystal was discovered by ... and ...

- converts electricity into ultrasound waves

- converts returning echoes back into electricity

Function of Piezoelectric crystal:

- Lead Zirconate Titanate

- Composite Crystal

Common Piezoelectric crystal materials:

Thinner elements - higher resonant frequencies - better image resolution

... elements - ... resonant frequencies - better image resolution

Inversely proportional

Size of diameter crystal and beam divergence relationship

Backing material

Part of the ultrasound transducer located behind the crystal

backing material

damping material

Epoxy resin, tungsten

Backing material is typically made of ... loaded with ...

- Dampens vibration

- Produces shorter pulses

- Improves axial resolution

Functions of Backing material:

Axial resolution

Ability of an ultrasound system to distinguish two structures that are positioned one behind the other along the direction of the ultrasound beam

directly proportional

Damping vibrations and production of shorter pulses relationship

Matching layer

Part of the ultrasound transducer located in front of the crystal

Matching layer

Improves transmission of sound tissue by reducing acoustic impedance mismatch

Acoustic lens

- Position at the tip of the transducer

- Focuses the ultrasound beam

- Improves lateral resolution

Lateral resolution

The acoustic lens improves ...

Physical housing

Protects internal components and provides electrical insulation

Convex (curvilinear) transducer

... has piezoelectric elements arranged along a curved surface, producing a wide, fan-shaped field of view

Convex (curvilinear) transducer

This type of transducer typically operates at low-to-moderate frequencies, providing good penetration for imaging deeper structures while maintaining adequate image resolution.

Convex (curvilinear) transducer

This type of transducers are commonly used for abdominal, pelvic, and obstetric examinations.

Convex (curvilinear) transducer

Transducer used for the second and third trimester of pregnancy

Linear transducer

an ultrasound transducer with piezoelectric elements arranged in a straight, linear array.

Linear transducer

This transducer produces a rectangular image with essentially parallel scan lines and typically operates at relatively high frequencies, providing excellent spatial resolution for superficial structures.

Linear transducer

These transducers are commonly used for musculoskeletal, vascular, breast, thyroid, nerve, and other superficial examinations.

Phased-array transducer

This transducer consists of multiple piezoelectric elements arranged in a compact array and uses electronic timing (phasing) to steer and focus the ultrasound beam.

Phased-array transducer

This transducer has a small footprint and produces a sector-or fan-shaped image, allowing visualization of

deep structures through narrow acoustic windows.

Phased-array transducer

These transducers are commonly used for cardiac imaging (echocardiography) and other examinations where access to the body surface is limited.

Endocavitary ultrasound transducer

A specialized ultrasound transducer designed to be inserted into a body cavity to obtain images of nearby internal structures.

Endocavitary ultrasound transducer

Its small footprint allows the transducer to be positioned close to the structures of interest, providing high-resolution images and a relatively wide sector-shaped field of view.

Endocavitary ultrasound transducer

These transducers are commonly used for obstetric and gynecologic (OB/GYN) and urologic examinations.

Endocavitary ultrasound transducer

Transducer used for the first trimester of pregnancy

Ultrasound transmission gel/Aqueous ultrasound gel

a water-based coupling medium placed between the ultrasound transducer and the patient's skin to eliminate air and improve the transmission of ultrasound waves into and back from the body.

Resolution

the ability of an imaging system to differentiate between structures

Spatial resolution

Resolution type: Detail in space

Contrast resolution

Resolution type: Gray shades

Temporal resolution

Resolution type: Changes over time (Frame rate)

Spatial (Detail) Resolution

The ability to display two structures situated close together

as separate image

Higher Frequency:

- Better resolution

- Lower penetrability

- Higher absorption

Higher Frequency:

- ... resolution

- ... penetrability

- ... absorption

Lower Frequency:

- Poor resolution

- Higher penetrability

- Lower absorption

Lower Frequency:

- ... resolution

- ... penetrability

- ... absorption

1. Axial resolution

2. Lateral resolution

Two components of spatial resolution:

Axial resolution

The ability to distinguish two objects parallel to the ultrasound to the beam

Lateral resolution

The ability to distinguish two objects perpendicular to the ultrasound beam

Spatial pulse length and wavelength

Axial resolution depends upon the ... and ...

Beam diameter

Lateral resolution depends upon the ...

Inversely proportional

Spatial pulse length and axial resolution relationship

inversely proportional

Beam width and lateral resolution relationship

Contrast resolution

• Differentiates tissue shades

• Optimized with correct gain

Directly proportional

Frame rate and temporal resolution relationship

Trackball

An input device that moves the pointer on the screen when the user rotates a ball, instead of moving the entire device--like a mouse.

1. Transducer

2. Central processing Unit (CPU)

3. Transducer pulse controls

4. Display monitor

5. Keyboard/Control panel

6. TCG (Time gain compensation) Sliders

Parts and function of ultrasound machine:

Transducer

Sends and receives sound waves.

sound waves

Transducer converts electrical energy into ... and back again.

Central Processing Unit (CPU)

The brain of the machine.

Central Processing Unit (CPU)

Processes raw echo signals and converts them into real-time images.

Transducer Pulse controls

Adjusts the amplitude, frequency, and duration of pulses sent to the transducer

Display monitor

Shows the real-time ultrasound image.

Display monitor

Used for observing and interpreting anatomical structures.

Keyboard/Control Panel

Used to input patient data and adjust scanning parameters (gain, depth, focus).

Keyboard/Control Panel

Includes buttons, trackballs, and knobs for navigation

TGC (Time Gain Compensation) Sliders

- Adjusts image brightness at different depths.

- Compensates for attenuation as the wave

travels deeper.

1. A-mode

2. B-mode

3. M-mode

4. Doppler mode

Display modes in diagnostic UTZ:

A-mode (Amplitude mode)

Displays echoes as spikes along a single line.

A-mode (Amplitude mode)

Used primarily in ophthalmology for axial length measurements.

B-mode (brightness mode)

Represents echoes as a 2D

grayscale image, where brightness corresponds

to echo intensity.

B-mode (Brightness mode)

The most common mode in diagnostic ultrasound

M-mode (motion mode)

Captures the motion of structures (like heart valves) over time along a single ultrasound line.

M-mode (motion mode)

Mode that is frequently used echocardiography.

Doppler mode

Evaluates blood flow by detecting frequency shifts due to the Doppler effect.

Color Doppler

Doppler mode: for visualizing flow direction and turbulence

Spectral Doppler

Doppler mode: for detailed velocity analysis

Power Doppler

Doppler mode: for detecting low-velocity flow in small vessels

Duplex Doppler system

Doppler mode: Combination of a B-mode and Doppler system; allows the Doppler beam to be directed accurately at any particular blood vessels

Continuous wave (CW) Doppler

Uses two crystals: one continuously sending ultrasound waves and the other continuously receiving returning echoes.

Continuous wave (CW) Doppler

Can measure very high blood flow velocities, making it useful in cardiology

Pulse wave (PW) Doppler

Uses a single crystal that alternates between sending and receiving ultrasound waves.

Pulse wave (PW) Doppler

Provides depth specificity, meaning it can measure blood flow velocity at a precise location using a sampling gate.

Linear scan

produces a rectangular or square-shaped image

because the utrasound beam lines are transmitted parallel to one another from a linear transducer.

1. Rectangular image

2. Parallel scan lines

3. Large footprint

4. Hugh frequency

Characteristics of linear scanning:

6-15 MHz

Linear transducers commonly use higher frequencies, often approximately ...- ..., depending on the application.

- Better spatial resolution

- Less penetration

Higher frequency provides:

sector scan

produces a fan-shaped or pie-shaped image in

which the ultrasound scan lines diverge from a relatively small point or aperture.

1. Fan-shaped image

2. Small footprint

Characteristics of sector scanning: