For superficial structures (e.g. nerves in the interscalene, supraclavicular and axillary regions), it is ideal to use high frequency transducers greater than or equal to 7 MHz.
Transducers in the range of 10-15 MHz are preferred but depth of penetration is often limited to 2-3 cm below the skin surface.
For visualization of deeper structures (e.g. in the infraclavicular and popliteal regions), it may be necessary to use a lower frequency transducer (less than or equal to 7 MHz)
because it offers ultrasound penetration of 4-5 cm or more below the skin surface. However, the image resolution is often inferior to that obtained with a higher frequency transducer.
Linear transducers less than or equal to 5 cm wide are available for high frequency transducers. Smaller transducers, i.e., transducers with smaller footprints are useful for detailed
scanning where the patient's anatomy prohibits the use of bulkier transducers (e.g., the supraclavicular region where there is limited access). Curved transducers are best suited for scanning
whenever a wide field of view is required.