Technical Assessment

Technical Assessment: Liver Ultrasound

A technical assessment for liver ultrasound involves evaluating the image quality, anatomical coverage, and sonographic technique to ensure accurate diagnosis and documentation. This is typically done by the sonographer or radiologist and is often included in structured reporting. Below is a sample technical assessment section and the key points usually covered:
1. Study Type:

• Complete abdominal ultrasound
• Focused liver ultrasound
• ollow-up / Targeted liver exam
• Doppler liver ultrasound

2. Image Quality:

• Adequate / Good / Suboptimal
• Acoustic window: Clear / Limited due to bowel gas, body habitus, or motion artifact
• Liver parenchyma: Well visualized / Poorly visualized

3. Structures Evaluated:

• Liver size and contour
• Liver echotexture (homogeneous/heterogeneous, fatty infiltration, cirrhotic changes)
• Intrahepatic bile ducts (normal/dilated)
• Hepatic vessels (portal veins, hepatic veins, IVC)
• Gallbladder and biliary tree
• Focal liver lesions (if any)
• Right kidney and Morrison’s pouch (for reference)

4. Doppler Assessment (if performed):

• Hepatic artery and portal vein flow direction and velocity
• Liver echotexture (homogeneous/heterogeneous, fatty infiltration, cirrhotic changes)
• Hepatic venous waveform
• Portal hypertension signs (e.g., collaterals, reversed flow)

Technical Assessment

Transducer Selection

1. Transducer Selection

• Curved Array Transducer (2–5 MHz):Primary probe for abdominal imaging; allows deep penetration with wide field of view suitable for liver evaluation.
• Linear Array Transducer (5–12 MHz):Used for evaluating superficial lesions in thin patients or for guiding interventional procedures.
• Phased Array Transducer:Occasionally used in intercostal views or in critically ill patients where access is limited.

2. Imaging Modes Utilized

• 2D Grayscale Imaging:Standard for evaluating liver size, contour, parenchymal echotexture, lesions, biliary ducts, and vessels.
• Color Doppler Imaging:Evaluates flow in the portal vein, hepatic veins, hepatic artery, and any vascular lesions. Helps identify flow direction and turbulence.
• Spectral Doppler:Used for waveform analysis in hepatic veins (triphasic), portal vein (hepatopetal monophasic), and hepatic artery (resistive index).
• Elastography (if available):Strain Elastography or Shear Wave Elastography to assess liver stiffness in suspected fibrosis or cirrhosis.
  Provides quantitative kPa or m/s values.
• Contrast-Enhanced Ultrasound (CEUS):Performed using microbubble contrast agents to characterize liver lesions (e.g., hemangioma, HCC, metastases). Requires low MI (mechanical index) settings and dual-screen for contrast dynamics.

3. Machine Settings and Optimization

• Depth and Gain:Adjusted to ensure full liver coverage with optimal parenchymal contrast. Time gain compensation (TGC) balanced from near to far field.
• Focal Zones:Positioned at or just below the area of interest to maximize lateral resolution.
• Dynamic Range:Tuned for optimal contrast resolution to differentiate lesions from normal liver tissue.
• Harmonic Imaging:Enabled to enhance lesion detectability and reduce artifacts in obese patients or deeper organs.g:
• Doppler Settings:
• Color box size and angle minimized to maximize frame rate.
• PRF (Pulse Repetition Frequency): Set appropriately for expected flow velocities.
• Wall filters: Lowered for detecting slow venous flow in portal vein.
• Angle correction: Applied when measuring velocities (>60° avoided if possible).
• Elastography Calibration:Performed with patient in breath-hold, right lobe through intercostal space, avoiding large vessels.
• CEUS Optimization:
• Low MI settings (e.g., 0.08–0.2)
• Real-time dual-imaging for contrast tracking
• High frame rate, low persistence

Ultrasound Transducer Types

Type	Frequency (MHz)	Use
Curvilinear (Convex)	2–5 MHz	Standard transducer for adult abdominal imaging. Provides deep penetration and a wide field of view.
Linear Array	5–12 MHz	Used for high-resolution imaging of superficial structures, pediatric patients, or focal lesions in thin patients.
Phased Array	2–4 MHz	Occasionally used in intercostal views or limited acoustic windows.

Technical Assessment

Imaging Modes

Ultrasound Imaging Modes

Mode	Purpose
B-mode (Brightness Mode)	Main mode for liver parenchyma, contour, and lesion visualization.
Color Doppler	Assesses blood flow in hepatic vessels (e.g., portal vein, hepatic veins).
Spectral Doppler	Measures velocity and direction of flow in specific vessels.
Power Doppler	More sensitive than color Doppler for detecting low-velocity flow (e.g., portal hypertension, small vessels).
Elastography (optional)	Assesses liver stiffness (fibrosis staging).
Contrast-Enhanced Ultrasound (CEUS)	For detailed lesion characterization (requires contrast agent).

Technical Assessment

Machine Settings and Optimization

To ensure diagnostic-quality images, the following settings should be carefully adjusted:
a. Depth

• Set so the liver fills most of the screen without cutting off posterior segments.
• Keep the area of interest centered.

b. Gain

• Adjust to enhance overall brightness without overexposing the image.
• Time-Gain Compensation (TGC): Adjust for even brightness from near to far field.

c. Focus

• Position the focal zone at or just below the area of interest (e.g., lesion or vessel).

d. Dynamic Range

• A moderate dynamic range provides a balance between contrast and detail.
• Narrow range: High contrast (good for lesion detection).
• Wide range: More grayscale detail (good for parenchymal texture).

e. Frame Rate

• High frame rate preferred, especially when assessing motion or blood flow.
• Adjust sector width and depth to optimize.

f. Doppler Settings

• Scale (PRF):Set appropriately to avoid aliasing.
• Gain:Increase until background noise appears, then slightly reduce.
• Wall filter: Lower settings for slow venous flow.
• Angle correction:Keep angle < 60° for accurate velocity measurement.

Additional Tips

• Ensure the patient fasts for 6–8 hours to reduce bowel gas and improve visualization.
• Use gel liberally for better acoustic coupling.
• Reposition the patient (e.g., left lateral decubitus) if rib shadowing or poor windows occur.