Body Composition Validation Study

Measuring body composition can be done via a wide range of technologies,
ranging from highly accurate and expensive to quick and cheaper methods. The
current issue is that these technologies are either not accessible for the
majority of the people, or provide too low accuracy or demand proper training
to be applied correctly.
Ultrasound is a risk free technology, mainly used for medical imaging
purposes. This technique is capable of measuring direct thicknesses of tissue
layers like subcutaneous adipose tissue and muscle mass. The most commonly used
method in literature is similar to the skin fold caliper principle: measuring
tissue layer thicknesses on dedicated spots on the human body. Compared to the
skin fold caliper method, ultrasound distinguishes between skin and adipose
tissue. Additionally, the probe contains pressure sensors to make sure the same
pressure is applied constantly. In the future this will help untrained
personnel to operate the device, and even make sure the probe is kept
perpendicular to the skin.
A second, novel method is tested in this trial. Instead of on the spot
measurements, trajectories will be scanned to gain considerably more tissue
layer information compared to just spot measurements which we expect to results
in a significant gain in accuracy. These trajectories include the most commonly
used spots as well. To control for scanning speed, a laser-based speed sensor
is added to the experimental set up.
The secondary objective of this trial is to test a thoracic impedance
measurement vest, designed to be used in the home environment (i.e. without
supervision or prior expertise). Measurements of thoracic impedance can be used
to evaluate fluid retention in the lung in patients with congestive heart
failure. However, impedance measurements can be affected by a number of factors
(electrode-skin contact, body composition, etc.). In order to obtain meaningful
and comparable thoracic impedance measurements between subjects, it would be
desirable to remove uncertainty due to measurable physiological factors. By
investigating the relationship between body composition and thoracic impedance
in healthy subjects with a range of BMI, we aim to model the effect of body
composition and eventually remove this effect from the impedance measurements.
This will allow thoracic bio-impedance measurements to be normalised and
therefore comparable between subjects.

Primary
This study aims:
1) To validate ultrasound (both on the spot & trajectory measurements) against
the gold standard 3-compartment model to assess body composition.
2) To compare the accuracy of ultrasound to assess body composition with skin
fold measurements.
3) To develop new models for assessing body composition by ultrasound
technology (both on the spot & trajectory measurements), by using the
3-compartment model as the reference technique.

Secondary
In addition to the main aims of the study, a parallel and independent objective
will be:
4) To evaluate the effect of body composition (i.e. total body fat-free mass
and fat mass) on inter-individual variability in thoracic bio-impedance.
5) To investigate the accuracy of total body volume measurements using 3D
imaging in comparison to underwater weighing.

The study will be a cross-sectional observational study.

All techniques used specifically for this study are non-invasive. All other
techniques are of a very low risk and place little burden on the subject.
Subjects will be informed about the results of the study and will receive their
personal data.