LESSON 2 IMAGING METHODS OF ACOUSTIC FIELDS MODES

LESSON 2 IMAGING METHODS OF ACOUSTIC FIELDS .

MODES OF SONOGRAPHY • A-mode: A-mode (amplitude mode) is the simplest type of ultrasound. A single transducer scans a line through the body with the echoes plotted on screen as a function of depth. Therapeutic ultrasound aimed at a specific tumor or calculus is also A-mode, to allow for pinpoint accurate focus of the destructive wave energy. • B-mode or 2 D mode: In B-mode (brightness mode) ultrasound, a linear array of transducers simultaneously scans a plane through the body that can be viewed as a two-dimensional image on screen. More commonly known as 2 D mode now. • C-mode: A C-mode image is formed in a plane normal to a B-mode image. A gate that selects data from a specific depth from an A-mode line is used; then the transducer is moved in the 2 D plane to sample the entire region at this fixed depth. When the transducer traverses the area in a spiral, an area of 100 cm 2 can be scanned in around 10 seconds. [14] • M-mode: In M-mode (motion mode) ultrasound, pulses are emitted in quick succession – each time, either an A-mode or B-mode image is taken. Over time, this is analogous to recording a video in ultrasound. As the organ boundaries that produce reflections move relative to the probe, this can be used to determine the velocity of specific organ structures.

A-scan

M-scan

M-mode

B-scan • there a line, sector and arc scanning line scanning sector scanning arc scanning

sector scanning

Electronic scanning There are two type system: • linear step displacement of the beam • phased array • Total focusing method

SYSTEM OF LINEAR MOVING STEP OF THE BEAM

Directional diagram

Devices with phased array • focusing Changing the angle of the acoustic beam focusing The combination of focus and change the angle of entry

BLOCK DIAGRAM OF Device with timedelay

Set time-delay circuits with constant time-delay

Delay unit with modify time-delay

Total focusing method α 1 ∑Aij Информационная матрица Aij α 2 i – Излучатель j – Приемник α… 1 2 3 4 . . . αN A 11 A 12 A 13 A 14 A 21 A 22 A 23 A 24 A 31 A 32 A 33 A 34 A 41 A 42 A 43 A 44

Total focusing method решетка Дефект 4 Дефект 1 Дефект 3 Дефект 2 Дефект 6 Дефект 5 15 x 15 16 x 16 14 x 14 11 x 11 9 x 9 13 x 13 10 x 10 12 x 12 4 x 4 35 x 5 x 3 6 x 6 7 x 7 1 x 1 2 x 2 8 x 8

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