The use of X-rays in medical diagnosis gives rise to an increased exposure of the patient to radiation.

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.