'A' Level Medical Option Questions - X-Rays

Q4. Diagnostic X-rays are produced using a rotating anode X-ray tube.


(i) State two methods which can be used to increase the intensity of the X-ray beam produced by the tube.

Method 1: increasing the potential difference (voltage) across the tube
Method 2:
increasing the tube current or increasing the filament temperature

(ii) For each method of increasing intensity, state the effect on the maximum X-ray photon energy.

Method 1: will increase the maximum photon energy

Method 2: will not change the maximum photon energy

(3 marks)

(b) Before taking an X-ray photograph, the X-ray beam emerging from the tube is passed through an aluminium filter. State and explain the reason for filtering the X-rays.

The aluminium filter reduces the intensity of low energy photons but hardly changes intensity of high energy photons at all. We need high energy for the X-ray picture production [low energy tend to be attenuated by the body] Therefore reducing low energy photons reduces the dose received by patient without affacting picture quality.

(3 marks max)

(Total 6 marks)