Infrared optoelectronic volumetry, the ideal way to measure limb volume.

OBJECTIVES: The aim of the study was to compare a novel infrared optoelectronic system (Perometer) of limb volume measurement with water displacement and two indirect measurement techniques.
DESIGN: A prospective experimental study.
METHODS: In 10 healthy male volunteers (20 limbs) we compared limb volume measurements obtained by water displacement, infrared perometry, the disc model method and the frustrum method. In a further 17 patients with swollen limbs due to lymphatic (9 limbs) or venous (11 limbs) disease, perometry was compared to the disc model method and the frustrum method only.
RESULTS: In normal limbs, mean +/- S.D. limb volume using water displacement was 1802 +/- 268 ml. Perometer values agreed almost exactly (1809 +/- 262 ml, r = 0.97, variation +/- 7% by limits of agreement) but both the disc (1923 +/- 306 ml, r = 0.90, variation +/- 14%) and frustrum (1905 +/- 372 ml, r = 0.72, variation +/- 28%) methods significantly overestimated limb volumes (p < 0.05 (ANOVA, Fisher's Least Significant Difference)). In diseased limbs perometer, disc method and frustrum method results were 2415 +/- 995 ml, 2494 +/- 969 ml, and 2413 +/- 870 ml representing variation of +/- 17% and +/- 23% for disc method and frustrum method respectively compared to perometry.
CONCLUSIONS: Perometry is a novel, extremely accurate and easy method for assessing limb volume. It provides more accurate results than traditional indirect measurement of limb volume and potentially is a very useful clinical and research tool.