Ultrasound Image Optimization Settings

Image Optimization

• Image optimization involves adjusting settings to improve image quality
• Settings include output power, frequency, depth, zoom, gain, and focus

Output Power

• Adjusting output power varies sensitivity and detects weaker echoes
• Increasing output power:
  • Increases pulses and echo signals
  • Increases acoustical exposure (ALARA principle)
• Reducing output power:
  • Reduces intensity of pulses and energy transmitted to the patient
  • Reduces brightness of echoes visualized within the displayed image

Frequency

• Increasing frequency:
  • Increases resolution
  • Decreases penetration
• Multifrequency transducers are used for different applications:
  • Transabdominal: 3-5 MHz
  • Transvaginal: 5-20 MHz

Depth

• Depth of field of view varies with transducer type
• Increasing depth:
  • Increases far field and reduces near field
• Decreasing depth:
  • Focuses on superficial structures
  • Increases near field and reduces far field

Zoom

• Read zoom magnifies still image
• Write zoom magnifies live image
• Provides greater anatomical detail

Gain

• Echo signal amplification compensates for attenuation loss
• Increasing gain:
  • Brightens image
  • No change to amount of energy transmitted
  • High gain setting: noise and misdiagnosis
• Decreasing gain:
  • Darkens image
  • No change in energy transmitted
  • Low gain setting: misdiagnosis

Focus

• Focal zone can be single or multiple
• Decreases frame rate
• Artefacts can occur due to equipment malfunction, operator error, violation of assumptions, or physical principle

Artefacts

• Occur due to equipment malfunction, operator error, violation of assumptions, or physical principle
• Types of artefacts include:
  • Reverberation
  • Comet tail
  • Ring down
  • Mirror image
  • Shadowing
  • Enhancement

Reverberation Artefacts

• Produced due to repeated reflections
• Causes false echoes
• Characteristics:
  • Equally spaced echoes
  • Strong echoes due to high acoustic mismatch
  • Can be result of defective equipment or improper technique
  • Examples: biopsy needle, comet tail artefact

Comet Tail Artefact

• Type of reverberation artefact seen in US imaging of metallic objects
• Characteristics:
  • Single long hyperechoic echo
  • Parallel to sound of beams main axis
  • ‘Trails off’ distally
  • Examples: IUDs, surgical clips, needle tips

Ring Down Artefact

• Similar to comet tail artefact
• Typically occurs due to resonance of fluid trapped among gas bubbles after being insonated with ultrasound
• Characteristics:
  • Vibrations produce a continuous sound wave that is transmitted to the transducer

Mirror Image Artefact

• Created as sound reflects off strong reflector and is redirected towards object
• Characteristics:
  • Appears as second copy of object – deeper on image
  • Straight line: true reflector and artefact are equal distances from mirror

Shadowing Artefact

• Occurs when ultrasound beam meets reflector that causes almost total reflections
• Characteristics:
  • Everything posterior to reflector appears black – no energy

Enhancement Artefact

• Lower density mass – little attenuation
• Characteristics:
  • Increased through transmission amplitude of distal echo signal
  • Area of increased brightness relative to echoes from adjacent tissues
  • Examples: cystic/fluid masses

Test your knowledge on optimizing ultrasound image quality by adjusting settings such as output power, frequency, depth, gain, focus, and artifacts. Understand how changes in settings affect the image clarity and exposure levels.