Ultrasound depth selection for vascular access

Transverse ultrasound images of the right arm demonstrate the importance of proper image parameter selection.
(A) Poor image quality due to excessive depth (green arrow) and improperly positioned focal zone (asterisk). Note signal dropout in the lower half of the image, as the high frequency transducer cannot penetrate to 8 cm depth.
(B) Improved image quality with properly selected depth (green arrow) and focal zone (asterisk). There is now detailed resolution of the brachial artery (red arrow), paired brachial veins (blue arrows), and the biceps muscle. The humerus is also seen as a bright curved line deep to the vessels.