Is digital image plethysmographic (DIP) acquisition a valid new tool for preoperative body composition assessment? A validation by dual-energy X-ray absorptiometry

Background: The increasing incidence of obesity and the wider acceptance of laparoscopic surgery, have lead to a 10-fold increase in bariatric operations in the last 10 years. Widely used indices of obesity (weight and body mass index - BMI) cannot adequately distinguish between fat mass (FM), represented by the sum of kilograms (kg) of lipid, and fat-free mass (FFM), inclusive of lean (kg of proteins), bone (kg of minerals), glycogen, and total body water (TBW), which are important parameters for clinical and physiological studies. Methods. Anthropometric variables were measured in 19 Caucasian Italian individuals according to standard methods. Body weight (kg) and height (m) were measured, and BMI was calculated as kg/m(2). Body composition was evaluated, with a mean BMI of 25.95 +/- 5.04 kg/m(2), by dual X-ray absorptiometry (DXA) and by digital image plethysmographic (DIP) acquisition with a digital camera. The clear-colored body of the subjects was automatically converted into a front and lateral red-shaped figure, and then through algorithms the 2 pictures were transformed into a nominal volume; body weight was then divided by the estimated volume, so that the body density could be obtained. DXA was used as a comparison to assess fat mass and fat-free mass. Radiation exposure was <0.6 mSv. Results: Significant positive correlation (R = 0.971, P<0.001) was found between data of body composition obtained by DXA and DIP. Conclusions: Body volume assessed using DIP or DXA did not differ. According to this validation study, DIP represents a new promising tool for clinical applications.