High-Frequency and Ultra-High Frequency Ultrasound: Musculoskeletal Imaging up to 70 MHz

Abstract

Musculoskeletal (MSK) ultrasound has well-established advantages, able to investigate very small structures with high resolution and a quick and real-time dynamic evaluation with the possibility of contralateral comparison. Thus ultrasound has kept its own almost exclusive fields of application in daily clinical practice, and it is considered the first-level imaging technique to assess tendons, bursae, and capsuloligamentous structures of small peripheral joints as well as peripheral nerves. Up to now, however, clinical MSK ultrasound imaging could not go beyond the first 1 to 2 cm under the skin, using high-frequency probes up to 18 to 20 MHz with spatial resolution just below millimeters. We present the impressive technical advancements leading to image resolution as low as 30 µm using ultra-high frequency ultrasound (UHFUS) probes up to 70 MHz. High-frequency ultrasound and UHFUS, with frequencies ranging from 22 to 70 MHz, are promising tools to evaluate very superficial structures. In the MSK system, only two articles have assessed its value in limited case series. Future developments may be aimed to better assess ultrastructural changes of very superficial peripheral nerves and other thin structures such as pulleys, retinacula, and tendons.

Ultra-high frequency ultrasound (UHFUS) applications in Sjogren syndrome: narrative review and current concepts

“…As in other clinical fields (18,(38)(39)(40)(41)(42)(43), UFHUS is being explored in the pSS scenario in order to evaluate its potential contribution to improve the evaluation of the SGs, particularly regarding minor SGs.…”

“…UHFUS is a novel diagnostic technique which is finding an increasingly important role in several medical fields (18,19,(38)(39)(40)(41)(42)(43)(44)(45), including ophthalmology (38), dermatology (39,40), oral medicine (18,19,44,45), musculoskeletal (41,42) and vascular imaging (43). Since the axial resolution achievable increases with the frequency, the use of frequencies between 30-100 MHz allows to investigate superficial structures at a higher axial resolution compared to conventional US (46).…”

Ultrasonic Retinal Neuromodulation and Acoustic Retinal Prosthesis

“…To our knowledge, the highest resolution reported for laboratory investigation of ultrasonic retinal stimulation is ~100 µm with the 43 MHz stimuli [ 54 ]. It may be possible to achieve a resolution of 30 μm with a 70 MHz transducer [ 79 , 80 ] or even a resolution of on the scale of 10 μm with a higher-frequency transducer [ 81 ]. However, previous studies indicated a reduced stimulation efficiency with the increase of the frequency.…”

Evaluation of Tendon Disorders With Ultrasonography and Elastography

“…Ultra‐high‐frequency US transducers, with frequencies ranging from 22 to 70 MHz, provide lower resolution to 30 μm. Small structural tendon abnormalities and also tiny superficial tissues such as the pulley, retinacula, volar plate, and superficial peripheral nerve can be better assessed 34,35 …”