Ultrasound Transducers and Beam Mechanics

Vocabulary flashcards covering transducer types, beam steering, electronic focusing, crystal arrangements, and image formats based on lecture notes.

Electronic Focusing

A method of focusing the ultrasound beam electronically that is only possible with array transducers.

Curved Electrical Pattern

A curved excitation delay pattern across transducer elements that produces a focused ultrasound beam.

Steep Curve Delay

A large delay between the middle elements and outer elements that produces a shallow focus.

Flatter Curve Delay

A small delay between the middle elements and outer elements that produces a deep focus.

Single Focus Limit

Only one focus can be created per pulse.

Unfocused Beam

A beam created when electrical voltages interact with all crystals at the exact same time without delay.

Sound Propagation Path

The fixed rule that sound can only travel in a straight line.

Beam Steering Methods

The four methods used to steer an ultrasound beam: manual steering, mechanical steering, electronic steering, and combination steering.

Mechanical Steering

An outdated method of steering an ultrasound beam.

Combined Steering

A steering approach combining electronic steering and mechanical steering, dedicated to creating $3\text{D}$ images by using a motor to move a $2\text{D}$ array across $3$ different planes simultaneously.

Sloped Electrical Pattern

A sequential firing delay pattern that causes the ultrasound beam to be steered.

Sloped and Curved Pattern

An electrical firing pattern that causes simultaneous steering and focusing of the ultrasound beam.

Phasing

The delay in exciting crystals that uses all elements to create a sound beam; also used to steer the beam outward in wide scanning, steer Color Doppler boxes, and steer pulsed wave Doppler scan lines.

Sequencing

The process of using small groups of crystals to create a beam moving across the surface of the transducer (such as in B-mode image creation), which can also incorporate phasing within the small group.

Pixels

The picture elements that compose $2\text{D}$ ultrasound images.

Voxels

The volume elements that compose $3\text{D}$ ultrasound images.

$4\text{D}$ Imaging

$3\text{D}$ imaging captured in "real time," requiring a large amount of processing.

Pedof Transducer

A continuous wave transducer with no image created, containing $2$ semicircle crystals, manual steering, and fixed focus (external or internal); commonly used for vascular studies, and damaged PZT results in no signal sent or received.

Mechanical Sector Transducer

A transducer with a sector imaging shape, $1$ circular crystal, mechanical steering, and fixed focus (external or internal); commonly used for cardiac imaging, and damaged PZT causes complete image loss.

Mechanical Annular Array Transducer

A transducer with a sector imaging shape, $5$ concentric circle crystals, mechanical steering, and fixed focus achieved electronically; commonly used for cardiac imaging, and damaged PZT causes horizontal drop out.

Linear Switched Array Transducer

A transducer with a rectangular image shape, approximately $200$ rectangular crystals, no steering, and fixed focus (external or internal); commonly used for vascular (and some general) imaging, and damaged PZT results in vertical drop out.

Phased Array Transducer

A transducer producing a sector image shape using $4\text{--}128$ rectangular crystals, electronic steering, and electronic focusing; commonly used for cardiac imaging, and damaged PZT leads to poor steering and focusing.

Linear Sequential Array Transducer

A transducer with a rectangular image shape, $200\text{--}300$ rectangular crystals, electronic focusing, and none and/or electronic steering; features adjustable focal points and multi-focus capability, commonly used for vascular and small parts, and damaged PZT results in vertical drop out.

Curved Linear Sequential Array Transducer

A transducer producing a blunted sector image using $200\text{--}300$ rectangular crystals, electronic focusing, and none and/or electronic steering; uses sequencing to create B-mode images, commonly used for abdominal, vascular, and OB/GYN exams, and damaged PZT results in vertical drop out.

Vector Array Transducer

A transducer producing a flat top sector image using approximately $200$ rectangular crystals, electronic steering, and electronic focusing; commonly used for abdominal, vascular, OB/GYN, and cardiac imaging, and damaged PZT results in poor steering and focusing.

Sector Image Shape

An image display geometry characterized by a pointed top and a curved bottom.

Blunted Sector Image Shape

An image display geometry characterized by a curved top (which can have a shallow or steep curve) and a curved bottom.

Rectangular Image Shape

An image display geometry that is flat on all sides with $90^\circ$ angles.

Wide Scanning

A modern system capability that applies phasing to steer the beam outward, converting a rectangular scan into a trapezoid shape.

Older Rectangular Steering

An older system function that allows the B-mode beam of a linear transducer to be steered, creating a parallelogram.

Flat Top Sector (Trapezoid)

An image format that is flat on the top and curved on the bottom.

Continuous Wave

An ultrasound transmission mode that does not create images.

Single Element Transducer

A transducer category consisting of only one crystal or PZT element at the face of the transducer.

Array Transducer

A transducer category containing multiple crystals arranged in rows or patterns, capable of adjusting focus and/or multi-focus.

$1\text{D}$ Array

An array transducer that has crystals aligned in a singular row.

$1\frac{1}{2}\text{D}$ Array

An array transducer with crystals arranged in a minimum of $3$ rows where the center row is the widest, allowing for increased control of beam thickness.

$2\text{D}$ Array

An array transducer with crystals aligned in a square pattern, capable of $3\text{D}$ imaging.

Ultrasound Channel

An operational circuit comprising three components: the crystal, the wire, and the machine electronics.

Ring-Shaped PZT Elements

A transducer crystal arrangement of concentric rings indicating that multi-focus capability is achieved.

Modern $3\text{D}$ Transducer

A transducer built from a $2\text{D}$ array (applicable to sector, linear, and curvilinear formats) containing $2000$ to $9000$ elements that simultaneously sweeps through all $3$ planes and renders an image.