The half-value thickness of the tissue is 4.0 cm.

On the axes below, sketch a graph to show the variation with tissue thickness x of \(\frac{{{I_t}}}{{{I_0}}}\).

Calculate the attenuation coefficient of X-rays for this tissue.

For a different type of tissue, the ratio \(\frac{{{I_t}}}{{{I_0}}}\) is smaller for the same thickness x of material.

Compare the attenuation coefficient of this tissue with that of the tissue in (b).

Barium has an attenuation coefficient that is much larger than that for human tissue.

Explain why a patient is asked to drink a liquid barium meal to help produce an X-ray image of the digestive system.

smooth curved decay line beginning at \(\frac{{{I_t}}}{{{I_0}}} = 1\) when x=0;

passing through other three points as shown;

\(\mu  = \frac{{\ln 2}}{4}\);
0.17cm^-1;
Watch for alternative correct answers such as 17m^-1.

e^-μx smaller/e^μx is larger;
μ larger;

or

it has a shorter half value thickness;
and so μ larger;

stomach tissue has similar attenuation coefficient to nearby tissue (so does not show up on X-ray);
barium absorbs X-rays well (and lines the stomach after drinking);
barium allows stomach walls to show as contrast;