Core Imaging Controls (Grayscale)

Transducer: the correct transducer is critical.  You are not going to be doing a carotid with a phased array.  The correct transducer is a high frequency rectangular array.  However, always keep in mind that the default transducer may not be the best choice when imaging a specific pathology.  Most late obstetrics are scanned with a curved array.  However, if the fetus is in a good position a detailed view of accessible structures may be obtained with a rectangular high frequency array.  Keep your options open. 

Depth: This adjusts the field of view and the reproduction scale on the monitor.

Importance: Using more depth than necessary decreases the frame rate and degrades image resolution 

Adjustment: Use the smallest depth necessary to keep the structure of interest well positioned within the field of view. 

Frequency: Many transducers are "wide bandwidth," allowing the operator to toggle between higher and lower frequencies 35-37.

Importance: Higher frequencies provide better resolution but have poorer tissue penetration.

Adjustment: Always start with the highest frequency and decrease it only if you cannot reach the required depth. 

Acoustic Power (Transmission Power): Regulates the amount of energy exciting the transducer crystal, determining the strength of the transmitted beam.

Importance: It directly affects patient exposure; you must keep this at the minimum level required to achieve adequate penetration.

Adjustment: It should be adjusted according to the ALARA (As Low As Reasonably Achievable) principle. 

Overall Gain (Receiver Gain): This amplifies the returning echo signals equally across the entire image.

Importance: It adjusts general brightness without increasing patient exposure.

Adjustment: It should be set to achieve even brightness; however, setting it too high adds electronic noise and may hide subtle tissue textures.

Time Gain Compensation (TGC): Compensates for attenuation.  Sound attenuates (weakens) as it travels deeper, therefore the TGC applies incremental gain at specific depths to compensate for the loss in sound intensity.

Importance: It ensures the image has uniform brightness from top to bottom, compensating for sound loss.

Adjustment: Sonographers use slider controls to increase gain in deeper segments to match the brightness of superficial ones. 

Focus (Focal Zone): Defines the depth where the ultrasound beam is narrowest, providing the best lateral resolution.

Importance: It allows for the most precise and detailed visualization of side-by-side structures.

Adjustment: Position the focal zone marker at or just below the structure of interest Note: Using multiple transmit focal zones can improve overall resolution but may significantly reduce the frame rate.