Robert E. Short

Sentinel node detection using contrast-enhanced power Doppler ultrasound lymphography

Rationale and objectivesTo establish the feasibility of using contrast-enhanced interstitial ultrasound (US) lymphography as an alternative to current sentinel node detection methods. MethodsAqueous US contrast microbubble suspensions of varying diameter were evaluated in vitro to characterize response to insonation. Contrast media were then injected subcutaneously into the distal extremities of 11 normal dogs to target the cervical and popliteal lymph nodes (nodes, n = 40). First-order (sentinel) lymph nodes and second-order sublumbar nodes were imaged intermittently from 0 to at least 120 minutes following contrast injection using continuous power Doppler mode. Lymphoscintigraphy studies were performed on 4 dogs to verify lymphatic drainage patterns and sentinel lymph nodes. ResultsContrast enhancement occurred in 34/40 (85%) sentinel nodes overall and in 30/32 (94%) nodes when submicron or near-micron diameter bubble formulations were used. In many instances, enhancement persisted throughout the imaging period. Contrast response was most pronounced using a high mechanical index and tissue artifact was reduced or eliminated when using a high pulse repetition frequency. ConclusionsContrast-enhanced interstitial US lymphography could serve as an alternative to current sentinel node detection methods. Preliminary findings suggest that submicron or near-micron-diameter bubbles may be suitable for lymphatic imaging applications.

Contrast Enhanced Intermittent Power Doppler Ultrasound with Sub-Micron Bubbles for Sentinel Node Detection

A sentinel lymph node can be defined as the first node to receive lymphatic drainage from a solid neoplasm and sentinel nodes are at greater risk for regional metastasis than other nodes. Sentinel node detection using perilesional injected blue dye, radiopharmaceuticals and intraoperative gamma probes has recently become the standard for localization and intraoperative sampling of high-risk lymph nodes for such neoplasms as breast cancer and melanoma that have significant regional metastatic potential (1–6). The purpose of this investigation was to evaluate lymphatic uptake of interstitially delivered sub-micron ultrasound contrast media for targeted regional lymph node enhancement using intermittent Power Doppler imaging in a normal dog model. Our goal was to determine the feasibility of contrast enhanced interstitial lymphography using ultrasound as an alternative to current intraoperative sentinel node detection methods.