Figure 1: Tissue structure of the Human Thorax Model. The
numbers in the diagram indicate the thickness of the tissue layers in
millimeters.
When the thorax is illuminated by the UWB signal emitted by a
transmitter, the signal encounters various tissues. The signal
propagates from the front through the pulsating heart and then leaves at
the back of the thorax. A pulsating heart is subject to the variation of
dimensions longitudinally towards its apex (pointed end) during diastole
and systole of each cardiac cycle. 26 With reference
to the transverse cross-section of human heart 19shown in Figure 2, the parts of the pulsating heart close to its apex
and along its short axis the UWB signal is assumed to encounter during
its propagation are, the right ventricle (RV) wall, RV cavity, inter
ventricular septum, left ventricle (LV) cavity and LV wall. The
instantaneous heart dimensions 19 calculated as the
sum of the instantaneous dimensions of all the above parts during one
cardiac cycle are shown in Figure 3.