Reference no: EM13975

1. (a) With reference to Fig. 1(a) show that the magnification of an object is given by M=SID/SOD.

(b) With reference to Fig. 1(b) show that the size of the penumbra (blur) f is given by f=F×(M-1).

2. Consider the task of identifying a 1 cm thick breast cancer that is embedded inside a 4.2 cm thick fibroglandular breast as depicted in Fig.2.

The cancerous tumor has a cross-sectional area of A=1 mm². Let us assume the beam is monoenergetic with photons of energy 20 keV. The total linear attenuation coefficients for the breast cancer and fibroglandular breast tissue at 20 keV are respectively µ_cancer=0.844 cm^-1and µ_{fibroglandular}= 0.802 cm^-1.

I. First let's consider the case with no scatter at image receptor. Calculate the local radiographic contrast [i.e. C=|Nt-Nb|/Nb] for this particular imaging task.

II. Next, suppose that there was a constant S/P = 3 at the image receptor. Calculate the local radiographic constrast as in I but now including the scatter contribution.

3. A radiograph is made of an object with a width of 3 mm using an x-ray tube with a 2 mm focal spot at a source-to-film distance of 100 cm. The object being imaged is 15 cm from the film.

Find the size of the image and the size of the blurred region at its edges.

4. By means of a diagram, discuss what effect will be produced on a film when a focused grid designed for 100 cm is used at 150 cm.