Use the attenuation coefficients water

PHYSICS · Multi-part · Fermi University Physics · Nuclear Physics · Biophysics & Medical Physics · Radioactivity and decay modes

Life at Thermal Energy, Ch Images from attenuation and from decay

Problem

Use the

60\,\mathrm{keV}

attenuation coefficients water

0.206\,\mathrm{cm^{-1}}

, soft tissue

0.217\,\mathrm{cm^{-1}}

, fat

0.188\,\mathrm{cm^{-1}}

, cortical bone

0.604\,\mathrm{cm^{-1}}

. ((a)) A radiograph is taken with a beam that passes through

2\,\mathrm{cm}

of cortical bone embedded in soft tissue. Calculate the subject contrast

C_{\rm s} = 1 - e^{-\Delta(\mu t)}

of the bone against the surrounding tissue. ((b)) Elsewhere in a reconstructed CT slice a voxel of soft tissue reads

\mu = 0.217\,\mathrm{cm^{-1}}

. Convert this to Hounsfield units, taking water as

\mu_{\rm w} = 0.206\,\mathrm{cm^{-1}}

. ((c)) A syringe is labelled

600\,\mathrm{MBq}

of technetium-99m (

t_{1/2} = 6.0\,\mathrm{h}

, molar mass

99\,\mathrm{g\,mol^{-1}}

). Calculate the number of atoms and the mass, in nanograms, in the syringe. ((d)) The tracer above clears from the body with a biological half-life of

20\,\mathrm{h}

. Calculate its effective half-life.

Related theory

Nuclear Physics

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