OCR A-Level Physics - Medical Imaging Questions with Complete Solutions

1. What provides the energy of the X-rays in an X-ray tube? - AnsThe kinetic energy of the accelerated electrons. 2. What is an X-ray? - AnsA photon produced by the deceleration of a fast-moving electron 3. What is the typical p.d. of an X-ray tube for medical imaging? - Ans30-100kV 4. What causes the emission of electrons from the cathode in an X-ray tube? - AnsIt is heated to produce thermionic emission. 5. What name is given to the anode in an X-ray tube? - AnsThe target metal. 6. What is an essential property for the target metal in an X-ray tube? - AnsHigh melting point. 7. What causes the production of X-rays in an X-ray tube? - AnsThe deceleration of electrons when they hit the target metal/anode. 8. In an X-ray tube what happens to most of the kinetic energy lost by the electrons when they hit the anode? - AnsIt is transferred to thermal energy of the anode. 9. What measures can be taken to prevent an anode melting in an X-ray tube? - AnsIt is cooled by oil or rotated 10. What feature of X-ray tubes protects the radiographer? - AnsLead lining. 11. What determines the maximum frequency of X-rays produced in an X-ray tube? - AnsThe maximum kinetic energy of a single electron. 12. When is the equation λ = hc/eV used? - AnsTo find the minimum wavelengths of X-ray produced (by an X-ray tube) 13. What is V in the equation λ = hc/eV? - AnsThe accelerating potential difference. 14. Describe the beam used by CAT scanners. - AnsA thin (1-10mm) fan. 15. What happens to the position of the X-ray tube during a CAT scan? - AnsIt rotates around the patient. 16. What are the key advantages of CAT scans over conventional X-rays? - AnsThey produce a 3D image and can distinguish between tissues with similar attenuation coefficients. 17. What are the disadvantages of CAT scans compared to conventional X-rays? - AnsThe radiation dose is greater and they are more expensive and take more time. 18. How does a CAT scan produce a 3D image? - AnsA series of slices are imaged and processed via a computer. 19. What is X-ray attenuation? - AnsThe decrease in intensity as X-rays pass through matter. 20. What are the four mechanisms of X-ray attenuation? - AnsSimple scatter, Photoelectric Effect, Compton Scattering, Pair Production 21. What occurs during simple scatter of X-rays? - AnsThe X-ray interacts with an electron in an atom and changes direction but not energy. 22. Which method of attenuation is most significant with X-rays with energy in the range 1-20keV? - AnsSimple scatter 23. What occurs during the photoelectric effect attenuation of X-rays? - AnsThe X-ray is absorbed by an electron in an atom which gains the energy of the photon and leaves the atom. 24. Which method of attenuation is significant with X-rays with energies up to 100