35.8 IRR17 and IR(ME)R 2017

3. UK Radiation Protection Regulations: IRR17 vs. IR(ME)R 2017

In the United Kingdom, dental radiography is governed by two complementary but completely separate statutory regulations, both updated in 2017.

UK Statutory Radiation Regulatory Framework
  │
  ├── IRR17 (Ionising Radiations Regulations 2017)
  │     ├── Regulated by: Health and Safety Executive (HSE)
  │     ├── Primary Focus: Protection of Workers, Staff, and the General Public
  │     ├── Key Appointments: Radiation Protection Adviser (RPA) & Radiation Protection Supervisor (RPS)
  │     └── Operational Mandate: Controlled Areas, Local Rules, Equipment Maintenance, Contingency Plans
  │
  └── IR(ME)R 2017 (Ionising Radiation [Medical Exposure] Regulations 2017)
        ├── Regulated by: Care Quality Commission (CQC) in England, HIS in Scotland, HIW in Wales
        ├── Primary Focus: Protection of the Patient Undergoing Diagnostic Exposure
        ├── Key Duty Holders: Referrer, Practitioner, and Operator
        └── Core Principles: Clinical Justification, ALARP Optimisation, Diagnostic Reference Levels (DRLs)

Detailed Comparison: IRR17 vs. IR(ME)R 2017

IRR17: Key Roles and the Controlled Area

• Radiation Protection Adviser (RPA): Every dental practice utilizing ionising radiation must formally appoint an RPA in writing. The RPA is an external expert (typically a chartered medical physicist) who provides technical advice on radiation shielding, design of controlled areas, equipment specification, contingency planning, and staff dose monitoring.
• Radiation Protection Supervisor (RPS): Must be an in-house member of the practice staff (typically a dentist or senior hygienist/radiographer) who holds appropriate training. The RPS is responsible for supervising daily operations and ensuring staff adhere strictly to the practice Local Rules.
• The Controlled Area: The designated area around the X-ray tube head and patient where radiation doses could exceed statutory worker limits. In primary dental radiography, the controlled area is defined as 1.5 metres from the X-ray tube head and the patient along the direction of the primary beam, or the physical walls of the room if the room is smaller and appropriately shielded. Only the patient is permitted inside the controlled area during exposure.
• Local Rules: Must be displayed prominently inside every room housing X-ray equipment. The Local Rules must clearly specify: the name of the RPS and RPA, the physical boundaries of the Controlled Area, equipment operating instructions, and clear Contingency Plans (e.g., actions to take if the X-ray exposure light remains illuminated and fails to terminate: immediately isolate the main power supply switch at the wall, evacuate the room, lock the door, and notify the RPS/RPA).

IR(ME)R 2017: Duty Holders and Radiation Principles

• The Three Statutory Duty Holders:
  1. The Referrer: A registered healthcare professional (dentist or doctor) who supplies sufficient clinical data regarding the patient to allow the exposure to be justified.
  2. The Practitioner: A registered healthcare professional who takes primary clinical responsibility for justifying the medical exposure, weighing the individual diagnostic benefit against the radiation detriment.
  3. The Operator: Any individual who carries out a practical aspect of the radiographic procedure. This includes: positioning the patient, positioning the image receptor, setting exposure factors (kV, mA, exposure time), pressing the exposure button, developing/processing digital plates, and reporting/evaluating the image clinically. A single dentist often acts simultaneously as Referrer, Practitioner, and Operator.
• Core Principles of IR(ME)R:
  • Justification: Every exposure must be clinically justified on an individual basis. Routine "screening" radiographs at fixed time intervals without prior clinical examination are illegal under IR(ME)R.
  • Optimisation (ALARP Principle): Radiation doses must be kept As Low As Reasonably Practicable (ALARP) consistent with obtaining required diagnostic information. Technical optimization measures include:
    • Rectangular Collimation: Mandated standard; reduces radiation dose to the patient by 40% to 50% compared to standard circular collimators.
    • Fast Image Receptors: Digital solid-state sensors or photostimulable phosphor plates (or E/F-speed analog film).
    • Focus-to-Skin Distance (FSD): Long cone technique with minimum FSD of 200 mm.
    • Tube Potential: Operating between 60 kV and 70 kV to maximize diagnostic image contrast while minimizing low-energy scatter.
  • Diagnostic Reference Levels (DRLs): National benchmark doses set by the UK Health Security Agency (UKHSA). Primary care dental practices must establish and audit local DRLs (e.g., standard intraoral periapical DRL is approximately $1.2\text{ mGy}$ entrance surface dose; adult panoramic radiograph DRL is approximately $80-100\text{ mGy}\cdot\text{cm}^2$).
• Radiographic Quality Assurance (CGDent / FGDP Standards):
  • Grade A (Excellent Quality): No errors; optimal diagnostic value. Target: $\ge 90%$.
  • Grade B (Diagnostically Acceptable): Minor positioning or processing errors that do not obscure diagnostic utility. Target: $\le 10%$.
  • Grade C (Unacceptable): Severe errors rendering the image unreadable; must be repeated. Target: $\le 5%$.

Applying the Duty Holder Roles in a Dental Practice

The examinable subtlety is that one person frequently holds several IR(ME)R roles, and candidates must be able to allocate them for a described scenario. In a typical practice the employer is the practice owner or corporate body, who must have written procedures and protocols in place. The referrer is the registered healthcare professional entitled to refer, and supplies sufficient clinical information for justification. The practitioner justifies the exposure and takes responsibility for it. The operator carries out any practical aspect, which includes pressing the exposure button, positioning the patient and the receptor, processing the image, and clinically evaluating it. A general dental practitioner taking a bitewing on their own patient is therefore acting as referrer, practitioner and operator simultaneously; a dental nurse who has completed appropriate training and is acting under protocols may be an operator but is not a practitioner. Every operator must be adequately trained and their training records kept.