Sonography Notes

Introduction to Sonography

Objectives

  • Explain the pulse-echo principle used in sonographic imaging.

  • List differences between Operating Principles 1 and 2.

  • Describe the image formats used in sonography.

  • Explain how the Doppler effect is applied in sonography.

  • List the ways in which Doppler information is presented.

  • Learn basic sonographic appearance terminology

Ultrasound

  • Sound with a higher pitch than humans can hear.

  • Above 20kHz20 kHz. Bats, dolphins, and other animals use ultrasound.

Diagnostic Medical Sonography

  • Medical 2D and 3D anatomic and flow imaging using ultrasound

  • A visible counterpart of an invisible object.

  • Accomplished with a pulse-echo technique.

Pulse-Echo Technique

  • Pulses of sound are sent into the tissues.

  • Echoes returning from the tissues provide anatomic information.

  • The ultrasound instrument processes the returning echoes and presents them as visible dots, which form the anatomic image.

  • Brightness of the dot corresponds to the echo strength.

  • Location corresponds to the echo return time.

Two Principles of Operation

  • Two principles of operation are present in the variety of current sonographic systems

    • Operating Principle 1

    • Operating Principle 2

Operating Principle 1

  • Positional information is determined by:

    • Knowledge of the direction of the pulse

    • Measurement of the echo return time

  • The instrument uses the echo arrival time to determine the depth of the structure that produced that echo

  • Accomplished with pulse-echo technique

  • One-to-one correspondence

    • Echoes from one pulse appear as one scan line

  • Not all of the ultrasound pulse is reflected back

  • Most of the original pulse continues on to be reflected from deeper structures

  • Each scan line represents a series of echoes returning from a pulse traveling through the tissue

  • Multiple scan lines are used to create an image

Operating Principle 2

  • Used in more recent, sophisticated sonographic systems

  • Produces improved image quality compared to Operating Principle 1

  • Does not rely on a one-for-one correspondence of pulse and displayed scan line

  • Several pulses sent through all regions of cross section of anatomy

  • All echo information is collected

  • Massive computational processes determine location and strength of each echo produced

Two-Dimensional Scan Formats

  • Principle 1:

    • The scan format determines the starting points and paths for individual scan lines, according to the starting point and path for each pulse used to generate each scan line

  • Principle 2:

    • Retrospective computational beam-forming determines echo information at each location in the scan

  • Cross-sectional images produced are called B scans or gray-scale scans

  • Commonly limited to three types:

    • Linear

    • Sector

    • A combination of the two

Linear Format

  • Closely spaced parallel vertical scan lines

  • Pulses travel in the same direction

  • Different starting points for each subsequent pulse

  • Rectangular display

Sector Format

  • Each pulse originates from the same starting point

  • Subsequent pulses go out in slightly different directions

  • “Slice of pie” display

Sector and Linear Combination

  • Pulses originate from different starting points (linear)

  • Each pulse travels in a slightly different direction from that of the previous one (sector)

  • Curved display

Volume Imaging

  • Three-dimensional echo data acquired by many two- dimensional sections of echo information

  • Forms a three- dimensional volume of data

Doppler Effect

  • Change in frequency caused by a moving object

  • Used to detect and measure tissue motion and blood flow

Doppler Ultrasound

  • Doppler information is presented in audible, color Doppler, and spectral-Doppler forms

Color Doppler

  • Color-coded presentation of Doppler information superimposed on gray-scale images

Spectral Doppler

  • Doppler information is applied to loudspeakers for audible evaluation and to spectral displays for quantitative analysis

Ultrasound Terminology

  • Isoechoic- echo strength is the same as what it is next to

  • Anechoic- absence of echoes (fluids) -black

  • Hypoechoic- less bright than object next to it

  • Hyperechoic- brighter than object next to it

  • Echogenic-

  • Homogeneous- all similar echoes (Like liver)

  • Heterogeneous- different echoes

  • Cystic- meets criteria of STAR fluid filled

  • Solid-

  • Complex (Mass, Structure, Tumor)- both cystic and solid

  • Septation- little separations

  • Spiculation- like fingers that go out

    • Artifacts: Enhancement Shadow Banding Reverberation Noise

Echogenicity

  • Hyperechoic -

  • Isoechoic-

  • Hypoechoic-

  • Anechoic-

Homogeneous vs Heterogeneous

  • Homogeneous-

  • Heterogeneous (Inhomogeneous)-

Enhancement vs Shadowing

  • Posterior Enhancement- an artifact that occurs when sound waves travel through a structure that is less dense than surrounding tissues, resulting in an increased echogenicity behind the structure.

  • Posterior Shadowing- an artifact that is observed when sound waves encounter a structure that is denser than the surrounding tissues, leading to a decrease in echogenicity behind the structure.

Cystic

  • Anechoic- no echoes inside of it

  • Well-defined borders

  • Posterior enhancement- caused by fluids

Solid

  • Hyperechoic, hypoechoic, or anechoic

  • Homogeneous or heterogeneous

    • Echo brightness can be changed

    • Irregular, often poorly defined margins

    • Low-amplitude (strength) echoes or shadowing posterior

Complex

  • Both anechoic and echogenic areas

  • From both fluid and soft tissue

Septation & Spiculation

  • Septation

    • Division or partitioning of a cavity into parts

  • Spiculation

    • Fingerlike extension of a malignant tumor

Other Medical Terminology

  • Parenchyma – functional tissue of an organ

  • Lumen – cavity within a tubular structure

    • Inside of aorta

  • Fossa – anatomical pit, groove or depression

    • Where gallbladder lives

  • Ipsilateral – on the same side of the body

  • Contralateral – on the opposite site of the body

  • Congenital – condition or trait present at birth

  • Systemic – affects the entire body, rather than a single organ or body part

  • Diffuse – widely spread

  • Focal – limited to one specific area

More Medical Terminology

  • Neoplasm – abnormal growth of cells (tumor)

  • Benign – condition or growth that is not cancerous (does not spread)

  • Malignant – cancerous cells that have the ability to spread

  • Metastasis – spread of cancer cells from where they first formed to another part of the body

  • Neovascularization – formation of new blood vessels

  • Necrosis – death of body tissue (necrotic)

  • Hepatomegaly – enlargement of the liver

  • Splenomegaly – enlargement of the spleen

  • Lymphadenopathy – swelling of lymph nodes