a) Define the terms linear ottenuation coefficient and mass attenuation coefficient and state the 6. units of measu...
a) Define the terms linear ottenuation coefficient and mass attenuation coefficient and state the 6. units of measurement of each quantity. b) A layer of homogeneous material with physical density p and linear attenuation coefficient μ has uniform thickness t.A narrow beam of monoenergetic x-radiation is incident on this layer at right angles. State the relationship between the transmitted intensity Ivan and the incident e. Hence obtain an expression for the attenuation A defined as A = 1 intensity c) If the area of this beam is B, calculate the mass m of the layer that is irradiated and hence show that the attenuation is also given by the product of the mass attenuation coefficient and areal density (defined as mass per unit area). d) Bone mineral content may be measured in vivo using an x-ray tube operating at two different voltages. Make the simplifying approximation that the x-ray beams behave in the same way as monoenergetic radiation of energies 40 keV and 90 keV. Assuming that the human body consists of bone mineral of equivalent thickness t and homogeneous soft tissue of equivalent thickness t derive an expression for the areal density of bone mineral in terms of the attenuations at 40 kev and 90 kev, the linear attenuation coefficients of bone mineral and soft tissue at these two photon energies and the physical density of bone mineral. [91 e) Bone mineral has a defined chemical composition and so its linear attenuation coefficients and physical density are known. Explain why the same is not true of soft tissue. In practice, how are the attenuation coefficients of soft tissue measured in an individual patient to enable the f bone mineral areal density?
a) Define the terms linear ottenuation coefficient and mass attenuation coefficient and state the 6. units of measurement of each quantity. b) A layer of homogeneous material with physical density p and linear attenuation coefficient μ has uniform thickness t.A narrow beam of monoenergetic x-radiation is incident on this layer at right angles. State the relationship between the transmitted intensity Ivan and the incident e. Hence obtain an expression for the attenuation A defined as A = 1 intensity c) If the area of this beam is B, calculate the mass m of the layer that is irradiated and hence show that the attenuation is also given by the product of the mass attenuation coefficient and areal density (defined as mass per unit area). d) Bone mineral content may be measured in vivo using an x-ray tube operating at two different voltages. Make the simplifying approximation that the x-ray beams behave in the same way as monoenergetic radiation of energies 40 keV and 90 keV. Assuming that the human body consists of bone mineral of equivalent thickness t and homogeneous soft tissue of equivalent thickness t derive an expression for the areal density of bone mineral in terms of the attenuations at 40 kev and 90 kev, the linear attenuation coefficients of bone mineral and soft tissue at these two photon energies and the physical density of bone mineral. [91 e) Bone mineral has a defined chemical composition and so its linear attenuation coefficients and physical density are known. Explain why the same is not true of soft tissue. In practice, how are the attenuation coefficients of soft tissue measured in an individual patient to enable the f bone mineral areal density?