1. 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

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

3. 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.

4. 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.

5. 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)

6. 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

7. 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.

8. 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

9. 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)

10. 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.

11. 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:

12. 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.

13. 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.

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

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

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

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

18. Combined technology
Panoramic operation
CT operation

19. Cone Beam CT (CBCT) typical x-ray paramters U: 75-90 kV I: 12 -14 mA
t: sec
skin-source distance
SiD: 25 cm
patient dose (PD)
Effecitve dose
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

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

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

22. 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)

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

24. 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))

25. 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)

26. In case of two equipments a reciprocal bolt prevents simultaneous activation

27. 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.

28. 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.

30. 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

31. 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.

32. 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

33. 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).

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

36. 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

37. 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.

38. 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.

39. Thank you for your attention!