Appendix

Abstract

As proposed by SNEEK (1971, internal report M82), the ventricle within the thorax is modelled by a sphere of radius R, filled with a volume concentration c of contrast medium with a linear extinction coefficient µ_c, embedded in a flat layer of thickness D of water-like substance with a linear extinction coefficient µ_w. The mixture within the ball then has a linear extinction coefficient

$$\mu _2 = c\mu + \left( {1 - c} \right)\mu _w$$

(13.1)

If monochromatic radiation is assumed, the intensity I(x) of the outgoing radiation as a function of the distance x from the center amounts to (Fig. 13.1)

$$I_2 \left( X \right) = I_0 e^{ - \left\{ {\mu _2 2\sqrt {R^2 - x^2 } + \mu _1 \left( {D - 2\sqrt {R^2 - x^2 } } \right)} \right\}}$$

(13.2a)

for 0≦|x|≦R, and to

$$I_1 \left( x \right) = I_0 e^{ - \mu _1 D}$$

(13.2b)

for |x|≧R; I_o being the incident radiation intensity.