# Characterizing Normal Upper Extremity Lymphatic Flow with 99mTc In-House Dextran: A Retrospective Study

## TL;DR

This study examines normal lymphatic flow in the upper extremities using a custom radiotracer to better understand its clinical use in diagnosing lymphatic issues.

## Contribution

The study characterizes normal upper extremity lymphatic drainage patterns using a specific in-house radiotracer for the first time.

## Key findings

- 92% of upper extremity lymphatic tracts were visualized within 45 minutes.
- Axillary node detection rates increased from 46% to 86% between early and late imaging intervals.
- Delayed imaging revealed additional lymph nodes and showed minimal uptake in injection sites.

## Abstract

Lymphoscintigraphy evaluates the lymphatic system using radiocolloid compounds like 99mTc-sulfur colloid and 99mTc-nanocolloid, which vary in particle size and distribution timing. A local in-house Dextran kit (15–40 nm) was developed in 2005 and began clinical use in 2008 to localize sentinel lymph nodes; diagnose lymphedema; and detect lymphatic leakage. The normal drainage pattern remains unexplored. We retrospectively analyzed 84 upper extremity lymphoscintigraphies from 2008 to 2021. 99mTc in-house Dextran was intradermally injected into both hands, followed by whole-body imaging at specified intervals (≤15 min; 16–30 min; 31–45 min; 46–60 min), with some receiving delayed imaging. Visual and quantitative analyses recorded axillary and forearm lymph nodes and liver, kidney, and urinary bladder activity. Results showed 92% (77/84) upper extremity lymphatic tract visualization within 45 min. Axillary node detection rates increased from 46% (≤15 min) to 86% (46–60 min). Delayed imaging further revealed nodes. Epitrochlear or brachial node visualization was rare (4%, 3/84). Hepatic, renal, and urinary bladder activity was noted in 54%, 71%, and 93% at 1 h, respectively. The axillary node uptake ratio was minimal (<2.5% of injection site activity; median 0.33%). This study characterizes normal upper extremity lymphatic drainage using 99mTc in-house Dextran, offering insights into its clinical application