Consider two gadolinium phosphor screens. One screen is 100 mu m thick and the o
ID: 2088993 • Letter: C
Question
Consider two gadolinium phosphor screens. One screen is 100 mu m thick and the other is 200 mu m thick. The mass attenuation coefficient of gadolinium for 60 keV x rays is 11.75 cm2/g. The density of gadolinium is 7.90 g/cm3. Calculate the quantum efficiencies of each screen for x-ray photons of energy 60 keV. The PSF associated with the use of these screens with x-ray film are given by Gaussian distributions. Which of the two screens would yield the PSF with a larger sigma. Explain. Suppose the sigma of the PSF for the thin screen is 2 mm. How close can two points be so that they can be resolved as two points in the image?Explanation / Answer
a)
for 100 um :
EQ = 1 - e^(-u x) = 1 - e^(-11.75e-1 * 100e-6) = 0.000117
for 200 um :
EQ = 1 - e^(-u x) = 1 - e^(-11.75e-1 * 200e-6) = 0.000235