Comparison of Reliability, Time Cost, and Participant Comfort of Lymphedema Assessments in Upper Extremity

Upper extremity lymphedema is a chronic and progressive condition characterized by the accumulation of protein-rich interstitial fluid, leading to tissue fibrosis and structural volume increases. Precise, reliable, and practical limb volume measurement is vital for diagnosis, staging, and therapeutic monitoring. While water displacement volumetry remains the gold standard, it poses practical challenges including cross-contamination risks, prolonged setup, and inapplicability to patients with wounds or severe limitations. Circumference tape measurement with frustum modeling is widely used but suffers from high examiner dependency and geometric approximation errors. Emerging non-contact technologies, such as mobile Light Detection and Ranging (LiDAR) sensors and optical 3D surface scanning, offer rapid, hygienic, and objective alternatives. However, gaps remain regarding their sensitivity to subclinical volume variations, the influence of post-processing operator experience, procedural time costs, and participant burden.

This methodological, comparative, cross-sectional pilot study evaluates upper extremity volume assessment methods across two cohorts: healthy adults (n = 40) and individuals clinically diagnosed with upper extremity lymphedema (n = 24). Measurements are conducted on the dominant upper extremity in healthy participants and on the affected upper extremity in patients with lymphedema, demarcated from the ulnar styloid process to 2-3 cm distal to the axilla.

All participants undergo the following sequentially:

1. Water Displacement Volumetry: Conducted using a custom overflow tank and precision graduated cylinders as the reference standard. The hand volume is measured first and subtracted from the full-arm immersion volume. Strict decontamination protocols are applied between sessions.
2. Circumference Measurement: Circumferential measures are taken at 4 cm intervals in a supine position and converted to limb volume using the truncated cone (Kuhnke/Frustum) formula. Measurements are obtained independently by both an experienced and an inexperienced evaluator.
3. LiDAR-Based Scanning: Acquired using an iPad equipped with Structure Sensor 3 (Structure application). Standardized positioning is utilized with adhesive anatomical landmarks.
4. Photogrammetric/Optical 3D Scanning: Acquired using the Creality Raptor X 3D scanner (Creality Scan software).

To address operator dependency in digital workflows, raw 3D point-cloud processing, mesh trimming, and volumetric integration are performed under a blinded protocol by both an experienced operator and an inexperienced operator.

In the healthy adult cohort, a simulated localized edema protocol is additionally conducted to determine method sensitivity to small volume fluctuations. A non-absorbent medical silicone pad (calibrated to exactly 50 mL via prior water volumetry) is affixed to the participant's forearm, after which circumference, LiDAR, and 3D optical scanning procedures are repeated.

Comprehensive time-motion analyses are recorded with a digital stopwatch across three distinct phases for each modality: equipment preparation, data acquisition, and post-processing computation. Participant-reported outcomes, including physical discomfort and fatigue, are documented using a Visual Analog Scale (VAS, 0-100 mm) immediately after each test and ranked comparatively at session conclusion.