(a) A chest radiograph tube has a tungsten target ( ), is run at with a tube current…

PHYSICS · Subjective · Fermi University Physics · Biophysics & Medical Physics · Radiation physics and diagnostic imaging · Nuclear medicine, dosimetry and radiotherapy

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

Problem

(a) A chest radiograph tube has a tungsten target (

Z_{\rm at} = 74

), is run at

V_{\rm t} = 120\,\mathrm{kV}

with a tube current of

500\,\mathrm{mA}

, for an exposure time of

20\,\mathrm{ms}

. Using the empirical efficiency

10^{-9}Z_{\rm at}V_{\rm t}

, estimate the X-ray power output and the total X-ray energy emitted in this exposure. (b) In a skeletal bone scan, an organ retains

20\%

of an injected

800\,\mathrm{MBq}

dose of a technetium-99m-labelled bisphosphonate, which emits its

140\,\mathrm{keV}

gamma photon in

89\%

of decays. The camera's collimator accepts a fraction

1.2\times10^{-4}

of an isotropic emission, and the photons must cross

8.0\,\mathrm{cm}

of overlying tissue with

\mu = 0.154\,\mathrm{cm^{-1}}

. Estimate the detected count rate and the time needed to collect

1.0\times10^{6}

counts.

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