Use of a Novel Portable Three-Dimensional Imaging System to Measure Limb Volume and Circumference in Patients with Filarial Lymphedema

Abstract

The World Health Organization's Global Program to Eliminate Lymphatic Filariasis (LF) has reduced LF transmission worldwide, but millions remain affected by filarial lymphedema. Tools for clinically monitoring lymphedema in developing nations are limited. We tested a novel, portable, infrared three-dimensional imaging system (3DIS) against water displacement (WD) and tape measurement of limb circumference (TMLC) among patients with filarial leg lymphedema in Galle, Sri Lanka. Outcomes were accuracy and reproducibility of imaging system measurements. In parallel, we also tested the reproducibility of skin thickness ultrasound (STU) measurements. We examined 52 patients (104 limbs) with lymphedema of stages 0-6 ( = 28, 19, 20, 21, 2, 4, and 10, respectively). 3DIS measurements correlated nearly perfectly with WD ( = 0.9945) and TMLC values ( > 0.9801). The median time required to acquire imaging system measurements for both legs was 2.1 minutes, compared with 17, 7, and 29 minutes, respectively, for WD, TMLC, and STU. Median interexaminer coefficients of variation (CVs) for volume measurements were 1.1% (interquartile range [IQR] 0.5-2.1%) for WD and 1.7% (IQR 1.2-2.4%) for the 3DIS. CVs for circumference measurements were 1.4% (IQR 0.8-2.4%) by TMLC and 1.3% (0.8-1.9%) by 3DIS. Median interexaminer CV for STU was 13.7% (IQR 8.5-21.3%). The portable imaging system noninvasively provided accurate and reproducible limb volume and circumference measurements in approximately 2 minutes per patient. This portable technology has the potential to greatly improve assessment and monitoring of lymphedema in the clinic and in the field.

Portable infrared imaging for longitudinal limb volume monitoring in patients with lymphatic filariasis

“…Due to a miscalibration in the LT-NTD software that resulted in a mean offset of 5.4% (range 2.0% - 10.0%) between primary and backup volume measurements (Fig 2A), the primary (LT-NTD) measurements were systematically adjusted before examining CV among all (primary and backup) replicate measurements. After adjustment, CV among all replicate volume measurements per visit ranged from 0.0%– 8.2%, which was consistent with the results of our prior study [8]. When analyzed separately, CV for primary scans was not significantly different from CV for backup scans, or from CV for all measures combined.…”

“…The team visited between four and ten participants each study day in the morning (between 6:00–9:00 AM) and the afternoon (between 2:00–6:00 PM). At each visit both examiners used the 3DIS system (LymphaTech, Atlanta, Georgia) to collect 3D scans of both limbs of the participant as previously described [8]. Each scan requires that the participant stand on a flat, smooth surface in an open area with room for the examiner to circle (walk around) the participant at a distance of about 1 meter.…”

“…The LymphaTech software analyzes the 3D model to calculate customizable measurements of limb volume and circumferences. We chose to calculate leg volumes at a height of 32 cm, because this height was validated vs. water displacement in our prior study [8]. …”

“…After our initial validation of the 3DIS system [8] LymphaTech updated the software for both functions. We began the current study using an updated software package (LT-NTD) for both acquisition and analysis.…”

“…Historically, water displacement was the gold standard for measuring limb volumes, but it is logistically difficult to implement and infrequently used. We recently reported that a portable three-dimensional infrared imaging system (3DIS) enabled rapid and accurate lower extremity volume measurements comparable to those obtained by water displacement while requiring much less time and with less inconvenience to patients [8]. To understand the utility of repeated 3DIS measurements of limb volumes, however, one needs to understand both the amount of variability in the method, and how much limb volumes may actually vary in the absence of true lymphedema progression.…”