Overseas Registration Exam (ORE) Radiology, Radiography and Diagnostic Imaging Syllabus

Radiology, Radiography and Diagnostic Imaging syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Radiology, Radiography and Diagnostic Imaging in Overseas Registration Exam (ORE), not a summary of it.

1. 1

   Radiation Physics and Protection

   3 topics

   • Production and Properties of X-rays
   • Radiation Protection Legislation
     • IRR 2017 and IR(ME)R 2017 duties
     • Justification, optimisation and ALARP
   • Dose Limitation and Quality Assurance
2. 2

   Radiographic Techniques

   3 topics

   • Intraoral Radiography
     • Periapical paralleling and bitewing technique
     • Occlusal views and faults
   • Extraoral and Advanced Imaging
     • Panoramic (DPT) and cephalometric imaging
     • Cone beam CT indications and limitations
   • Digital Imaging and Image Quality
3. 3

   Radiographic Interpretation

   4 topics

   • Normal Anatomy on Dental Radiographs
   • Radiographic Features of Caries and Periodontal Bone Loss
   • Pathology on Imaging
     • Periapical and bone lesions
     • Cysts, tumours and incidental findings
   • Reporting and Audit of Radiographs

Radiology, Radiography and Diagnostic Imaging flashcards for Overseas Registration Exam (ORE)

23 of 51 cards from the Radiology, Radiography and Diagnostic Imaging deck — real questions with worked answers.

1. How are X-rays produced in a dental X-ray tube head?

   Electrons are 'boiled off' a heated tungsten filament (cathode) by thermionic emission, accelerated across a high voltage (kV) toward the tungsten target (anode), where their sudden deceleration converts kinetic energy into X-ray photons (mainly bremsstrahlung) and heat.

2. What are the two mechanisms of X-ray photon production at the target?

   Bremsstrahlung ('braking radiation') — produces a continuous spectrum as electrons decelerate near tungsten nuclei (majority of dental X-rays). Characteristic radiation — produces discrete energy peaks when an inner-shell electron is ejected and replaced by an outer-shell electron.

3. What proportion of the kinetic energy of electrons hitting the target becomes X-rays versus heat?

   Only about $1\%$ is converted into X-rays; roughly $99\%$ is lost as heat, which is why the target is tungsten (high melting point) often set in copper for heat dissipation.

4. What is the relationship between X-ray photon energy, frequency and wavelength?

   $E = h\nu = \frac{hc}{\lambda}$, where $h$ is Planck's constant, $\nu$ is frequency, $c$ is the speed of light and $\lambda$ is wavelength. Higher energy means higher frequency and shorter wavelength.

5. What effect does increasing the tube voltage (kV) have on the X-ray beam?

   Increasing kV raises both the maximum and mean photon energy (beam quality/penetrating power) and increases the quantity of photons, producing a higher-energy, more penetrating beam and a lower-contrast (longer grey-scale) image.

6. What effect does increasing the tube current (mA) or exposure time have on the beam?

   It increases the quantity (number) of X-ray photons produced, proportional to $mAs$ ($mA \times s$), without changing the maximum photon energy or beam quality. This increases image density/darkness.

7. Why is aluminium filtration added to a dental X-ray beam, and what is the minimum requirement?

   Filtration preferentially removes low-energy ('soft') photons that would only contribute to patient dose without reaching the image. For beams above $70\,\mathrm{kV}$, a minimum total filtration equivalent to $2.5\,\mathrm{mm}$ aluminium is required.

8. What is the focal spot and the line-focus principle?

   The focal spot is the small area of the target struck by electrons. The line-focus principle angles the target so that the effective (projected) focal spot is small (sharp image) while the actual area is larger (better heat dissipation).

9. State the inverse square law for radiation intensity and its formula.

   Radiation intensity is inversely proportional to the square of the distance from the source: $I \propto \frac{1}{d^{2}}$, so $\frac{I_{1}}{I_{2}} = \frac{d_{2}^{2}}{d_{1}^{2}}$. Doubling distance reduces intensity to one-quarter.

10. What are the five fundamental ways X-ray photons interact with matter?

    Photoelectric effect, Compton (incoherent) scatter, coherent (Rayleigh) scatter, pair production, and the photonuclear effect. In the diagnostic dental energy range, photoelectric absorption and Compton scatter predominate.

11. Which X-ray interaction is responsible for image contrast in dental radiography, and why?

    The photoelectric effect, because its probability is proportional to $\frac{Z^{3}}{E^{3}}$ (atomic number cubed over photon energy cubed). High-$Z$ tissues like bone and enamel absorb far more than soft tissue, creating contrast.

12. Which X-ray interaction is the main source of scattered radiation (dose to operator and image fog)?

    Compton scatter, in which a photon ejects an outer-shell electron and is deflected with reduced energy. It is largely independent of atomic number and is the dominant source of scatter and occupational dose.

13. Distinguish deterministic (tissue reaction) effects from stochastic effects of radiation.

    Deterministic effects have a threshold dose below which they do not occur, and severity increases with dose (e.g. skin erythema, cataracts, sterility). Stochastic effects have no threshold, with probability (not severity) increasing with dose (e.g. cancer induction, heritable effects).

14. Define absorbed dose and its SI unit.

    Absorbed dose is the energy deposited per unit mass of tissue. SI unit is the gray ($\mathrm{Gy}$), where $1\,\mathrm{Gy} = 1\,\mathrm{J\,kg^{-1}}$.

15. Define equivalent dose and how it is calculated.

    Equivalent dose accounts for the type of radiation: $H_{T} = \sum_{R} w_{R} \cdot D_{T,R}$, where $D_{T,R}$ is absorbed dose and $w_{R}$ is the radiation weighting factor (1 for X-rays). SI unit is the sievert ($\mathrm{Sv}$).

16. Define effective dose and how it is calculated.

    Effective dose accounts for the radiosensitivity of different tissues: $E = \sum_{T} w_{T} \cdot H_{T}$, where $w_{T}$ is the tissue weighting factor. SI unit is the sievert ($\mathrm{Sv}$); it allows comparison of whole-body risk from partial-body exposures.

17. What are the three core principles of radiation protection (ICRP framework)?

    Justification (the benefit must outweigh the detriment), Optimisation/ALARP (doses kept As Low As Reasonably Practicable), and Limitation (dose limits applied to workers and the public, but NOT to patients undergoing medical exposures).

18. Which two sets of UK regulations govern dental radiography, and what does each cover?

    IRR17 (Ionising Radiations Regulations 2017) — protection of staff and public (equipment, controlled areas, dose limits). IR(ME)R 2017 (Ionising Radiation (Medical Exposure) Regulations) — protection of the patient (justification, optimisation, duty holders).

19. Name the duty holders defined under IR(ME)R 2017.

    Referrer (requests the exposure), Practitioner (justifies/takes responsibility for the exposure), Operator (carries out practical aspects, e.g. positioning and exposing), and the Employer (provides the legal framework, written procedures and protocols).

20. What is the annual whole-body effective dose limit for a classified radiation worker in the UK?

    $20\,\mathrm{mSv}$ per year for classified employees. For members of the public the limit is $1\,\mathrm{mSv}$ per year. There is no dose limit for patients.

21. What is a controlled area in dental radiography, and how large is it?

    An area requiring special procedures to restrict significant exposure. For dental units it extends to $1.5\,\mathrm{m}$ from the X-ray tube and patient in all directions, plus the primary beam until adequately attenuated. The operator must stand outside it (or behind a barrier) during exposure.

22. What is the recommended minimum operator distance and position when no protective barrier is used?

    At least $1.5\,\mathrm{m}$ from the tube and patient, and standing at $90^{\circ}$ to $135^{\circ}$ to the primary beam direction (in the 'safe zone' to avoid the main beam and reduce scatter).

23. What is a Diagnostic Reference Level (DRL) and an example for a dental intraoral exposure?

    A DRL is a dose level for a standard procedure that, if consistently exceeded, prompts investigation of technique. A typical national DRL for an adult intraoral (periapical) radiograph is around $1.2\text{–}1.5\,\mathrm{mGy}$ patient entrance dose (or about $0.8\,\mathrm{mGy}$ in some current standards).

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