Question 2
The use of X-rays in
medical diagnosis gives rise to an increased exposure of the patient to
radiation.
Explain why
(a)
an aluminium filter may be placed in the X-ray beam when producing
an X-ray image of a patient, [3]
(b)
the radiation dose received by a patient is different for a CT scan
from that for a simple X-ray image. [4]
Reference: Past Exam Paper – November 2014 Paper 41 & 42 Q11
Solution:
(a)
The X-ray
beam contains many wavelengths (a spectrum of wavelengths).
The aluminium
filter absorbs long wavelength X-ray radiation that would be absorbed by the
body (and not contribute to the image).
(b)
CT scan
consists of (many) X-ray images of a slice and there are many slices.
So, there is a much greater exposure with CT scan as X-ray image is a single exposure.
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