General rules of ionizing radiation applications Adam Salik Anna Motoc Radiation Protection Training Course, 2018 Semmelweis University Faculty of Dentistry Department of Oral, Dental and Maxillofacial Surgery

Repeat (Introduction) Ionising radiations: Radioactive radiations (alfa, beta, gamma) X-rays Neutron radiation

MEDICAL EXPOSURES I. Justification Medical exposure shall show a sufficient net benefit, weighing the total potential diagnostic or benefits it produces, including the direct benefits to health of an individual and the benefits to society, against the individual detriment that the exposure might cause, taking into account the efficacy, benefits and risks of available alternative techniques having the same objective but involving no or less exposure to ionising radiation.

MEDICAL EXPOSURES II. Optimisation The medical exposure for radiodiagnostic are kept as low as reasonably achievable consistent with obtaining the required medical information, taking into account economic and societal factors. the optimisation includes the selection of equipment, the consistent production of adequate diagnostic information, the practical aspects of medical radiological procedures, quality assurance, and the assessment and evaluation of patient doses or, taking into account economic and societal factors.

Optimization of Protection in Dental Radiology Technical characteristics of intraoral, panoramic, and cephalometric dental x-ray equipment are summarized, along with operating characteristics Although doses are generally low, the high frequency of examinations requires radiation protection and quality control in dental radiology Some tests are detailed for quality control of dental equipment. What Tests ? Processor QC– most critical Collimation Dose Exposure Time Half-Value Layer Kilovoltage (kVp)

MEDICAL EXPOSURES III. Responsibilities Procedures Any medical exposure takes place under the clinical responsibility of a practitioner. Procedures written protocols for every type of standard medical radiological procedure are established for each equipment for relevant categories of patients

MEDICAL EXPOSURES IV. Equipment All medical radiological equipment in use is kept under strict surveillance regarding radiation protection; an up-to-date inventory of medical radiological equipment for each medical radiological installation is available to the competent authority; acceptance testing is carried out before the first use of the equipment for clinical purposes, and performance testing is carried out thereafter on a regular basis, and after any maintenance procedure liable to affect the performance.

Radiation protection (RP) For the effective operation of radiation protection, it is necessary to have appropriate laws and decrees. Complying with these, their revision and development can only be done based on prescribed constitutional form Organizations of International radiation protection - the main recommendations and regulations Basic documents for Hungarian regulation

Governmental regulation ICRP Publication 103. (2007) IAEA/IBSS EURATOM Directive 2013/59 (2013) Act No. CXVI of 1996 on Atomic Energy Governmental Decree No. 487/2015 Authority: Hungarian Atomic Energy (OAH)

Safe Use of X-Ray Equipment although doses incurred during dental examinations are in general relatively low, dental radiology accounts for nearly one third of the total number of radiological examinations in the EU and therefore merits specific attention with regard to radiation protection.

The aim of the study to provide a practical guide to radiation protection for professional groups of dentists and their assistants, based upon the two relevant Council Directives of the European Union: Directive 96/29/Euratom, of 13 May 1996, laying down the basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionising radiation; Directive 97/43/Euratom of 30 June 1997, on health protection of individuals against the dangers of ionising radiation in relation to medical exposure (Medical Exposures Directive). is to provide a practical guide to radiation protection for professional groups of dentists and their assistants, based upon the two relevant Council Directives of the European Union:

Issues to avoid unnecessary or excessive exposure to radiation and to improve the quality and effectiveness of medical uses of radiation no exposure to X-rays can be considered completely free of risk, so the use of radiation by dentists and their assistants implies a responsibility to ensure appropriate protection.

Dental X-ray equipment X-rays are an important tool that help dentists to diagnose, plan treatments and monitor both treatments and lesion development. Types of dental radiological procedure: intraoral bitewing or periapical radiography panoramic examinations cephalometric examinations According to the [UNSCEAR Report] and [IAEA RS-G-1.5], dental examinations are the most frequent type of radiological procedure, and account for 21% of the total on a global scale.

Intraoral dental X-ray equipment natural background: ~3000 µSv/y (0,1µSv/h typical x-ray paramters U: 65-70 kV I: 6-7 mA t: 0,5 sec skin-source distance SiD: 20 cm patient dose (PD) Effecitve dose 4-5 µSv/exposure

Panoramic X-ray equipment typical x-ray paramters U: 70-80 kV I: 8-10 mA t: 11-15 sec skin-source distance SiD: 25 cm patient dose (PD) Effecitve dose 20-30 µSv/exposure Dose limits(employee): 20.000 µSv/y

Protection of the patient thyroid protection lead apron Front?? Behind??

Cephalometric X-ray equipment typical x-ray paramters U: 75-90 kV I: 12 -14 mA t: 20-40 sec skin-source distance SiD: 25 cm patient dose (PD) Effecitve dose 200-500 µSv/exposure Obsolete-elavult natural background: ~3000 µSv/y (0,1µSv/h)

Combined technology Panoramic operation CT operation

Cone Beam CT (CBCT) typical x-ray paramters U: 75-90 kV I: 12 -14 mA t: 20-40 sec skin-source distance SiD: 25 cm patient dose (PD) Effecitve dose 200-500 µSv/exposure Dose rates around CBCT units are reported as being in the range of 2 to 40 μGy per scan at 1 metre (HPA 2010a) compared with intraoral and panoramic radiography scatter doses of less than 1 μGy per exposure at 1 metre (Sutton & Williams, 2000). Standing position Seating position

Mobile intraoral X-ray equipment Dose received by the operator due to scattered radiation (µSv/exp) Nomad EZX-60 Hand 0.18 2.88 Head 0.01 0.12 Gonad 0.00 0.05 Distance=70-80 cm texp=0.35 s NOMAD (Aseptico, USA) Additional shielding EZX-60 (Genoray, Korea)

Licensing procedure Acquisition of the licenses Establishment of the facility Installation of the equipment Operation of the equipment Ceasing of activity Grant, license

Grant conditions of the licenses First step radiation protection and safety plan (design) form radiation protection expert Establishment, Installation and operation license at the same time Workplace Radiation Protection Rules Setting up of the RP Service, assignment of the RP officer(s)

Conditions for employees Age (>18 years) Pregnant women Health eligibility (suitability) for the position Professional aptitude Acquisition of an appropriate radiation protection training

Radiation protection for medical and veterinary work places Hungarian Standard: MSZ 824:1999. RP of the workers and the public Occupational exposure – not exceed 3/10 of the dose limit ((Goverment Decree 487/2015) Surroundings (vicinity: dwellings, maternity ward, nursery, school) < 100 μSv Room design (made by a qualified expert) Size planning requirements: size of the basic area in m2, length of side in m (intraoral dental X-ray, inside switchgear 9 m2 / 2.5 m, outside switchgear 4 m2 /1.8 m), room height (2.65 m))

Installation of the dental radiography equipment Room design Positioning of the examination equipment (focus - wall distance; in case of two equipments a reciprocal bolt prevents simultaneous activation) These instructions should detail the responsibility for exposure, positioning of staff, use of protective devices, any restriction on primary beam direction Adequate auxiliary rooms (waiting rooms, corridors, restrooms)

In case of two equipments a reciprocal bolt prevents simultaneous activation

Design of the facility Protection of adjacent areas In deciding where to install dental X-ray equipment, it is essential to consider the likely consequences in terms of radiation dose to staff and members of the public in adjacent areas. This is particularly important if equipment is located close to a partition wall (i.e. within 1.5m for low workload situations), for any walls or floor in the direction of the primary beam (intraoral and cephalometry) and for high workload use. Ideally, the advice of a qualified expert should be sought to establish the required wall and floor structural attenuation.

Room layout It is essential that equipment operators can position themselves so that they have a view of: patient, controlled area and ‘X-rays on’ indicator light. If the room size is limited, it might be necessary for staff to position themselves outside the room, in which case a mirror/camera might be required to ensure a clear view of the room. The exposure switch should be located so that the operator can either remain outside of the controlled area or be behind a protective screen. Consideration needs to be given to the layout of the room so that radiation safety is optimised. The room should be of adequate size to allow all staff who need to remain within the room to position themselves outside the controlled area during exposure.

Principles of protection Primary and scattered radiation - X-rays travel in a straight line unless they interact with matter when their direction of travel can change. - The main beam of X-rays emitted by the X-ray tube is known as the primary beam. When this primary beam interacts with the patient’s head, radiation will be scattered in all directions. Optimisation of RP

Staff protection Dose limits In normal dental practice, effective dose should never exceed the annual dose limit for the workers (and would normally be expected to be lower). Likewise, dose to the skin of the hands should be well below the dose limit. Applying ALARA principle: “as low as reasonably achievable” However, in the past, incidences of deterministic damage to fingers have been reported in dentists due to the custom of holding the film in the patient’s mouth, a practice that should never happen now.

Use of time Absorbed dose rate: 10 µGy/h 1 hour = 10 µGy X time = absorbed dose 1 hour = 10 µGy 2 hours = 20 µGy

Use of distance For a point source of radiation: the dose rate falls off as the inverse of the square of the distance from the source (as light intensity falls off at distance from a light bulb).

Use of shielding Protective equipment (walls, leaded doors, leaded partition wall, leaded apron) thick 12 cm brick equal 0,5 mm lead

Results -for intraoral film radiography, the radiation dose in the primary beam is typically a few mGy at the end of the cone -the dose at 1 m – due to scattered radiation – is at least 1000 times less (a few µGy) -standing at a distance of 2 m from the patient’s head will lead to a dose of roughly a quarter of that received standing only 1 m away -for scattered radiation, the use of distance alone is often adequate protection in the dental situation

Patient exposure in dental practices Individual doses in basic dental radiography (intra-oral, panoramic and cephalometric) are low, being equivalent to those associated with a few days of background radiation. Individual doses from more complex imaging (CT scans and multiple slice cross-sectional tomography) can be substantially higher. Individual risks in dental radiography are small but are greater in the younger age groups (below 30) in which (in many EC member states) dental radiography is most frequently performed.

Patient exposure in dental practices 2 All X-ray examinations must be justified on an individual basis by demonstrating that the benefits to the patient outweigh the potential detriment. The anticipated benefits are that the X-ray examination would add new information to aid the patient’s treatment. No radiographs should be selected unless history and clinical examinations have been performed. ‘Routine’ radiography is an unacceptable practice.

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