pt 4 Ultrasound Imaging Techniques: Important Concepts and Protocols

Transverse Plane Imaging

Depth Adjustment:

• The depth of the field of view should be adjusted using the depth knob on the ultrasound system control panel. This ensures optimal visualization of structures in different areas of the body.

Gain Settings:

• Adjust gain to achieve uniform texture of liver parenchyma, enhancing the contrast and clarity of the image.
• Compare echogenicity of the liver with the right kidney to assess if liver tissue appears hypo- or hyper-echoic relative to the kidney, which may indicate pathology.

Outline Visibility:

• Ensure echogenic contour of the vertebral column is well-delineated to avoid interference from bowel gas, which can obscure diagnostic details.
• Image the posterior border of the liver by angling the transducer toward the dome and inferior edge of the liver to capture comprehensive anatomical details.

TGC (Time Gain Compensation):

• Adjust TGC to boost echoes from deeper tissue, improving visibility of structures located further away from the transducer. This helps in defining the boundaries and internal structures of organs.

Overall Gain:

• Decrease if excessive echoes appear outside the liver, providing a clearer picture of the liver's morphology. Ensure anterior surface of the liver is clear with appropriate near gain settings for effective diagnosis.

Liver Evaluation

Condition Assessment:

• Evaluate for focal and diffuse abnormalities, which can indicate various liver conditions such as fatty liver disease, cirrhosis, or tumors.
• Identify vascular structures: hepatic veins, main portal vein (including branches), and inferior vena cava crucial for assessing liver blood flow and pathology.

Lobe Imaging:

• Observe the right, left, and caudate hepatic lobes, ensuring no lesions are present.
• Note the right hemidiaphragm and pleural space with steep transducer angulation to rule out any abnormalities in adjacent organs.

Gallbladder and Biliary System

View Requirement:

• Additional oblique, decubitus, and upright views are needed to assess gallbladder and biliary anatomy accurately, especially to detect stones or inflammation.

Preparation:

• Patient must be nothing-by-mouth (NPO) 8 hours prior for gallbladder distention, which enhances visualization of the gallbladder in the ultrasound.

Ducts Visualization:

• Intrahepatic ducts assessed via liver and portal vein imaging; not visible unless dilation occurs, which may indicate an obstruction.

Pancreatic Evaluation

Assessment Areas:

• All pancreatic sections (head, body, tail) should be evaluated, maintaining clear imaging to detect conditions like pancreatitis or tumors.
• Distal common bile duct best visualized in transverse view, ensuring proper flow assessment.

Contrast Administration:

• Consider oral contrast or water if pancreas visibility is inadequate to better differentiate between the pancreatic tissue and surrounding structures.

Vascular Structures Imaging

Locations:

• Ascertain aorta and inferior vena cava as anechoic structures, crucial for vascular assessments.
• Aorta generally positioned left of midline; IVC on the right side, essential for evaluating vascular pathology and hemodynamics.

Spleen Assessment

Positioning:

• Spleen best assessed with the patient in steep decubitus. Compare spleen parenchyma with left kidney echogenicity to ensure proper assessment of splenic conditions.

Bowel Examination

Evaluation Parameters:

• Check for wall thickening, dilation, or pathology, essential for diagnosing gastrointestinal diseases.
• Bowel Dynamics: Observe peristalsis and ensure normal bowel compresses under gentle pressure, aiding in functional assessment.

Kidney, Adrenal, and Bladder Sonography

Assessment:

• Visualize renal cortex and pelvis, record renal lengths ensuring no abnormalities are present.
• Utilize Doppler for evaluating renal vascular structure status (stenosis, thrombosis) which can affect kidney functionality.

Longitudinal Scans

Technique:

• Rotate transducer by 90 degrees to capture longitudinal views, providing a different perspective of the same structures.
• Define diaphragm and liver structure based on the imaging angle for comprehensive assessment.

Transducer Settings:

• Use lower frequency for deeper penetration; adjust gain for uniformity ensuring balanced imaging quality.

Doppler Ultrasound Techniques

Overview:

• Used for evaluating cardiovascular flow patterns, crucial for vascular health assessments.

Types of Doppler Techniques:

• PW Doppler: Common for lower-velocity blood flow patterns; essential for estimating hemodynamic changes and flow.

Flow Characterization:

• Positive flow toward the transducer; negative flow directed away, assisting in understanding vascular conditions.

Key Pearls for Sonographers

• Familiarize with ultrasound equipment and controls to enhance operational skills.
• Understand examination protocols and indications for effective diagnosis.
• Read patient orders to prioritize relevant details for each ultrasound exam.
• Master ultrasound terminology and anatomy to communicate effectively with medical professionals.
• Demonstrate ability to perform abdominal sonography following protocols maintaining high standards of care.
• Understand Dop