What ultrasound depth and probe settings should be used for routine lung scanning in adults, thin adults, and children, and how should they be adjusted for deeper pathologies such as large consolidations or pleural effusions?

Ultrasound Depth Settings for Lung Scanning

For routine lung ultrasound in adults, set the depth at 12-18 cm using a curvilinear or phased array probe at 2.0-5 MHz; for thin adults and children, use 4-5 cm depth with a high-frequency linear probe at 5.0 MHz or higher. 1, 2

Standard Depth Settings by Patient Population

Adults (Standard Build)

• Depth: 12-18 cm provides optimal image quality for routine lung scanning 3
• Use curvilinear abdominal or phased array cardiac probe at 2.0-5 MHz (mean 3.5 MHz) 1
• A depth of field up to 25 cm may be required in large patients to adequately visualize deeper structures 1
• Small footprint probes facilitate scanning between ribs 1

Thin Adults and Children

• Depth: 4-5 cm is the recommended setting for pediatric and smaller adult patients 2
• Use high-frequency linear array transducer (5.0 MHz for children, 12-14 MHz for neonates) 1, 2
• Higher frequencies provide better resolution for superficial structures in smaller patients 2

Neonates

• Depth: 4-5 cm with high-frequency linear probe (12-14 MHz) 2
• Select preset suitable for lung examination or small organs 2
• Keep probe perpendicular to ribs or parallel to intercostal space 2

Adjustments for Specific Pathologies

Superficial Structures (Pleural Line Assessment)

• Reduce depth significantly when examining for pneumothorax or pleural sliding 1
• Adjust frequency, depth, focus and gain settings to optimally image these superficial structures 1
• Focus should be positioned at or near the pleural line for optimal visualization 3

Deep Pathologies

Large Consolidations:

• Increase depth as needed to visualize the full extent of consolidation 4
• Convex-array broadband probe (2-5 MHz) penetrates deeper than linear probes 4
• May require depths approaching 25 cm in large patients 1

Pleural Effusions:

• Standard adult depth (12-18 cm) usually adequate 3
• Posterior axillary line above the diaphragm is the optimal site for detection 1
• Microconvex transducer is preferable; if unavailable, use phased array or convex transducer 1

Additional Technical Parameters

Gain Settings

• Use at least 50% gain for optimal B-line visualization 3
• Gain of 90% improves B-line detection but decreases overall image quality 3
• Gain less than 90% provides better image quality while maintaining diagnostic accuracy 3

Focal Zone Position

• Set 1-2 focal zones close to the pleural line 2
• Focal point at the pleural line improves B-line visualization (odds ratio 1.64) but may decrease overall image quality 3
• For neonates, adjust focal zones close to the pleural line 2

Probe Selection

• Curvilinear transducer is superior for B-line visualization (63% vs 37% with linear probe) and provides higher image quality 3
• Linear probes are appropriate for superficial structures and pediatric patients 2, 4
• High-frequency linear array (5-12 MHz) combined with convex probe (2-5 MHz) provides comprehensive assessment in children 4

Common Pitfalls to Avoid

• Don't use excessive depth in thin patients or children - this degrades image quality and makes pleural line assessment difficult 2
• Don't use gain below 50% - this significantly impairs B-line detection (odds ratio 7.04 for 50% vs 10% gain) 3
• Don't set depth below 12 cm or above 18 cm for routine adult scanning - image quality is suboptimal outside this range 3
• Don't forget to adjust settings when switching from superficial to deep structures - anterior pleural assessment requires different parameters than deep consolidation evaluation 1

Additional Technical Considerations

• Use fundamental frequency with speckle reduction 2-3 or similar techniques for neonates 2
• Turn off spatial compounding imaging in neonatal exams 2
• Adjust time-gain compensation to achieve uniform image from near-to-far field 2