Core Imaging Controls (Grayscale)

Transducer: the correct transducer is critical.  This is a key decision.  For example, you are not going to be doing a carotid with a phased array.  The correct transducer for carotids is a high frequency rectangular array.  So selecting the correct transducer for the procedure is paramount.  

However, always keep in mind that the default transducer may not be the best choice when imaging a specific pathology.  Fore example, 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.