Beyond Ultra-high Frequency: Clinical Feasibility of 10-12 MHz and Portable Ultrasound in Lymphatic Imaging.

Lymphatic ultrasound has recently emerged as a noninvasive, contrast-free modality for evaluating lymphatic vessels, particularly as a preoperative tool for lymphaticovenous anastomosis. Although high-frequency linear probes (18-20 MHz) are commonly used, their availability may be limited, and ultra-high-frequency probes (≥30 MHz) are limited by poor tissue penetration. This study investigated the feasibility of using lower frequency linear probes (10-12 MHz), including a portable 10-MHz device, to visualize lymphatic vessels in patients with extremity lymphedema. A total of 24 limbs from 13 female patients were examined. Dilated lymphatic vessels were first identified using an 18-MHz probe, then reevaluated with either a 12- or 10-MHz probe. Among 44 sites, 86.4% of lymphatic vessels detected with the 18-MHz probe were also visible with lower frequency probes. Identification was more successful in the lower extremities (89.5%) than in the upper extremities (66.7%). Visualization rates were comparable between the 12- (87.0%) and 10-MHz (85.7%) probes. These findings suggest that lower frequency probes, including portable devices, can adequately visualize lymphatic vessels in most cases. This may facilitate wider adoption of lymphatic ultrasound in general clinical settings and resource-limited environments. However, further studies are needed to evaluate their standalone diagnostic performance and ability to assess lymphatic degeneration, and their limitations in de novo identification should also be acknowledged. Addressing these issues may help optimize probe selection and further expand the clinical utility of lymphatic ultrasound.