2012.11.30.

Overview of Radiation Protection

• Every day all over the world people are exposed to ionising radiation, almost all from natural sources in the environment or for medical reasons. • Ionising radiation has enough energy to cause damage cells which can increase the risk of cancer later in life. • In general the health effects of ionising radiation are dependent on the dose received.

Bálint Vecsei dr.

Background radiation

2,4-3,4 mSv/year

• Radiation is indispensable in modern medicine. • The radiographic examination is one of the principal diagnostic methods used in all fields of medical services • The risk associated with low-level diagnostic exposures could be expected to be low, but greater than zero

• For this reason it is prerequisite to measure the dose to the patients in the diagnostic radiology precisely. • the radiation dose to the patients should be as low as reasonably achievable, a principle known as ALARA (International Commission on Radiological Protection) • The number of diagnostic examinations should also be taken into consideration because the risk is directly proportional to the frequency of X-ray exposure.

1

2012.11.30.

effects of radiation are grouped into two categories • Dental radiographic examinations are one of the most frequently performed radiological studies. • The effective dose delivered to patients per radiograph is low but the collective dose is significant because of the large number of radiographs made.

• Deterministic effects are based on cell killing and are characterized by a threshold dose. Below the threshold dose there is no clinical effect. With exposures above the threshold dose the severity of the injury increases with dose.

• Stochastic effects, including cancer and heritable effects are based on damage to DNA. There is no-threshold or ‘‘safe’’ dose.

Three types of exposure
Persons are medically exposed as part of their diagnostic or treatment
According to ICRP and BSS, two basic principles of radiation protection are to be complied with: justification and optimization
Dose limits are not applicable, but a guidance is given on dose levels

• Medical Exposure (principally the exposure of persons as part of their diagnostic or treatment) • Occupational Exposure (exposure incurred at work, and practically as a result of work) • Public Exposure (including all other exposures)


Investigation of exposures is strongly recommended 10

1 : Overview of Radiation Protection in Diagnostic Radiolog

Framework of radiological protection for medical exposure • Justification • Optimization • The use of doses limits is NOT APPLICABLE

Three levels of justification • General level: The use of radiation in medicine is accepted as doing more good than harm • Generic level: specific procedure with a specific objective (eg. chest radiographs for patients showing relevant symptoms) • Third level: the application of the procedure to an individual patient

– Dose constraints and guidance (or reference) levels ARE RECOMMENDED 12

2

2012.11.30.

Justification for an individual patient (third level)

Generic justification (I) • It is a matter for national professional bodies, sometimes in conjunction with national regulatory authorities • The exposures to staff (occupational) and to members of the public should be taken into account • The possibility of accidental or unintended exposures (potential exposure) should also be considered • The decisions should be reviewed from time to time as new information becomes available

• To check that the required information is not yet available • Once the procedure is generically justified, no additional justification is needed for simple diagnostic investigations • For complex procedures (such as CT, IR, etc) an individual justification should be taken into account by medical practitioner (radiologist, referral doctor..)

13

14

The optimization of protection (I)

The optimization of protection (II)


Optimization is usually applied at two levels: – The design and construction of equipment and installations – Day to day radiological practice (procedures)

• There is a considerable scope for dose reductions in diagnostic radiology (ICRP 60)


Reducing the patient dose may reduce the quantity as well as the quality of the information provided by the examination or may require important extra resources

• Simple, low-cost measures are available for reducing doses without loss of diagnostic information (ICRP 60, 34)


The optimization means that doses should be “as low as reasonably achievable, economic and social factors being taken into account” compatible with achieving the required objective

• The optimization of protection in diagnostic radiology does not necessarily mean the reduction of doses to the patient

15

16

Risk of different activities (not ordered)

Risk and Dosislevels

• • • • • • • • •

Atomenergy Smoking Antibiotics X-ray diagnostic Electrocity Cycling Food preservation Automobile Consumtion of alcoholic drinks

3

2012.11.30.

Risk of different activities (increasing risk) • • • • • • • • •

Smoking Consumtion of alcoholic drinks Automobile Electrocity X-ray diagnostic Cycling Atomenergy Food preservation Antibiotics

Risk

1 micro-risk • • • • • • • • • • • •

2500 km travel by train 2000 km flight 80 km by bus 65 km by car 12 km by bike 3 km by motor bike smoke of one cigarette 2 month living together with a smoker eat one more bread and butter for a fat man breath 1 hour in Budapest sleep in a house one week to be stroked by thunder in 10 years

Application of x-ray. • „It is safer to see, than feel.” (Motto)

• Monument in garden of St. Georg Hospital in Hamburg, Germany • Fast spread of x-ray machines • Use of the technique without knowing the nature of this radiation • Why? (EMF, Nano)

►Advertisement

Development in Radiology

►Shoe-store

Development in Radiology • 16 slices CT (best: over 256 slices)

Veins on a segmented CT 3D image

1917

4

2012.11.30.

Benifit and risk

Development in Radiaton protection

Benifit

Benifit and risk

Overview of dose quantities Radiation

Physical

Chemical

Bio-chemical

Biological

effect

effect

effect

effect

Absorbed dosis

Risk

Equivalent dose RISK

Benifit

Effective dose

• Reflects the combined detriment from stochastic effects due to the equivalent doses in all the organs and tissues of the body • The combination of probability and severity of harm is called “detriment”.

Estimated lifetime risk as a function of age

Risk • Risk = (amount of harm) x (probability of harm)

5

2012.11.30.

Risk • We always run a risk for some benifit • There is hardly any activity without risk

Risk • We always run a risk for some benifit • There is hardly any activity without risk

Risk in industry

Risk • Risk = (amount of harm) x (probability of harm) Example: Having a job Benifit: basis for the existence Loss: harms, accidences, death at work place

Can we know the risk of our job/profession? Probability of an acciedent Risk

~ number of accidents / all workers

~ Probability of an acciedent x losses per accident

manufacture of clothes, 0,01

Extra-risk of Chernobyl in Hungary Plus dose: 0,2 mSv / 30 Years Probability of plus cancer: 0,00001 • First way to communicate: "30 years of it's radiation in Hungary is as much as 1 month of natural background radiation." • Second way to communicate: "The extra-risk is as much as to smoke 1 cigarette, or 60 km of auto-driving." • Third way to communicate: "The radiation of Chernobyl killed 100 people in Hungary.” (0,00001*10 000 000 = 100)

Radiation We live with 1-3 mSv

Can kill 4000 mSv

Where to stop, where is the safe point? What are the effects of radiation?

6

2012.11.30.

Three types of exposure

Medical exposure

• Medical Exposure (principally the exposure of persons as part of their diagnostic or treatment) • Occupational Exposure (exposure incurred at work, and practically as a result of work) • Public Exposure (including all other exposures)

• Medical Exposure – Exposure of persons as part of their diagnostic or treatment – Exposures (other than occupational) incurred knowingly and willingly by individuals such as family and close friends helping either in hospital or at home in the support and comfort of patients – Exposures incurred by volunteers as part of a program of biomedical research

Changes in Dose Limit (ICRP)

Dose constraints for medical exposure

mSv

• For medical exposure dose constraints should only be used in optimizing the protection of persons exposed for medical research purposes, or of persons, other than workers, who assist in the care, support or comfort of exposed patients.

Year 40

PUBLIC - Optimization under Constraints

Dose constraints • for medical research purposes • for individuals helping in care, support or comfort of patients, and visitors

• DOSE LIMITS • effective dose of 1 mSv in a year • in special circumstances, effective dose of 5 mSv in a single year, provided that the average over five consecutive years in less than 1mSv per year • equivalent dose to lens of the eye 15 mSv in a year • equivalent dose to skin of 50 mSv in a year.

– 5 mSv during the period of the examination or treatment – 1 mSv for children visiting

1 : Overview of Radiation Protection in Diagnostic Radiology

41

42

7

2012.11.30.

Dose Limits (ICRP 60)

Occupational dose limits

Occupational Public

• 100 mSv/5 years effective dose

Effective dose

• BUT does not allowed over 50 mSv in any year!

Annual equivalent dose to ► Lens of eye 150 mSv ► Skin 500 mSv ► Hands & Feet 500 mSv

20 mSv/yr averaged* over 5 yrs.

1 mSv in a yr

15 mSv 50 mSv

N.B.: M.P.D. 1931 = 500 mSv, 1947=150 mSv, 1977=50 mSv & in 1990=20 mSv

Dose Limits (ICRP 60)

Guidance levels for diagnostic radiography (typical adult patient)

Students, trainee Effective dose

1 mSv/yr averaged*

Annual equivalent dose to ► Lens of eye 150 mSv ► Skin 50 mSv ► Hands & Feet 150 mSv

Examination

Entrance surface dose per radiograph (mGy)

Thoracic spine AP

7

Thoracic spine LAT

20

Dental peri-apical

7

Dental AP

5

N.B.: M.P.D. 1931 = 500 mSv, 1947=150 mSv, 1977=50 mSv & in 1990=20 mSv

46

Typical effective doses from diagnostic medical exposures

Guidance levels for diagnostic radiography (typical adult patient)

Examination

Entrance surface dose per radiograph (mGy)

Skull AP

5

Skull LAT

3

Dose values are in air with backscatter. They are for conventional film-screen combination (200 speed class). For higher speed film-screen combinations (400-600), the values should be reduced by a factor of 2 to 3.

Diagnostic procedure

Typical effective dose (mSv)

Equiv. no. of chest x-rays

Approx. equiv. period of natural background radiation

Chest (single PA film)

0.02

1

3 days

Skull

0.07

3.5

11 days

Thoracic spine

0.7

35

4 months

Lumbar spine

1.3

65

7 months

From: Referral Criteria For Imaging. CE, 2000. 1 : Overview of Radiation Protection in Diagnostic Radiology

47

48

8

2012.11.30.

Typical effective doses from diagnostic medical exposures Diagnostic procedure

Typical effective dose (mSv)

Equiv. no. of chest x-rays

Approx. equiv. period of natural background radiation

CT head

2.3

115

1 year

CT chest

8

400

3.6 years

CT Abdomen or pelvis

10

500

4.5 years

Comparison of doses from sources of exposure Source of Exposure Dental X-ray 135g bag of Brazil nuts Chest X-ray Transatlantic flight Nuclear power station worker average annual occupational exposure

Dose 0.005 mSv 0.005 mSv 0.02 mSv 0.07 mSv 0.18 mSv

UK annual average radon dose CT scan of the head UK average annual radiation dose USA average annual radiation dose CT scan of the chest Average annual radon dose to people in Cornwall

1.3 mSv 1.4 mSv 2.7 mSv 6.2 mSv 6.6 mSv 7.8 mSv

Whole body CT scan Annual exposure limit for nuclear industry employees

10 mSv 20 mSv

Level at which changes in blood cells can be readily observed

100 mSv

Acute radiation effects including nausea and a reduction in white blood cell count

1000 mSv

Dose of radiation which would kill about half of those receiving it in a month

5000 mSv

From: Referral Criteria For Imaging. CE, 2000. 1 : Overview of Radiation Protection in Diagnostic Radiology

49

Summary

Personal Dosimetry
Personal dosimetry provides the means to measure and record radiation doses received by individual workers.

• Exposure of patients as part of their diagnostic or treatment, has to be justified • Optimization of patient exposures means keeping doses to a minimum without loss of diagnostic information • Guidance dose levels are defined to serve as a reference for medical practitioners: if a level is exceeded some specified action or decision should be taken • Guidance (reference) levels are not dose limits. 1 : Overview of Radiation Protection in Diagnostic Radiology


Personal dosemeters should be worn by operators who take more than 100 intra-oral films or 50 panoramic films per week.
In practice, the majority of dentists and support staff do not need to wear dosemeters although many do so as a reassurance measure. 51

9