2

DeathCancerSkin BurnsCataractInfertilityGenetic effects

3

Deterministic effectsdeath, skin burns, cataract, infertility

Stochastic effectscancer, genetic effects

1895 X Rays discovered by Roentgen 1896 First skin burns reported 1896 First use of X Rays in the treatment of cancer 1896 Becquerel: Discovery of radioactivity 1897 First cases of skin damage reported 1902 First report of X Ray induced cancer 1911 First report of leukaemia in humans and lung

cancer from occupational exposure 1911 94 cases of tumour reported in Germany

(50 being radiologists)

5

PREVENTIONPREVENTION of deterministic of deterministic effect.effect.

LIMITINGLIMITING the probability of the probability of stochastic effectstochastic effect

RS = Probability of a cell, tissue or organ of suffering an effect per unit of dose.

High RS Medium RS Low RS

Gonads

Thyroid

Eye lens

Bone Marrow

Spleen

Lymphatic nodes

Lymphocytes

Skin

Mesoderm organs (liver, heart, lungs…)

Muscle

Bones

Nervous system

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It is generally assumed that even very It is generally assumed that even very small doses of ionizing radiation can small doses of ionizing radiation can potentially be harmful .potentially be harmful .

Therefore, persons must be protected from Therefore, persons must be protected from ionizing radiation at all dose levels.ionizing radiation at all dose levels.

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Patients.Patients. Members of his/her family.Members of his/her family. Workers.Workers. General public.General public.

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We live with1-3 mSv/y

Can kill4000 mSv

Persons are medically exposed as part of their diagnostic or treatment

According to IAEA, ICRP and BSS, two basic principles of radiation protection are to be complied with:

justification and optimization

Justification Optimization Dose Limitations

Time (dose directly proportional to

length of exposure).

Shielding (b/w source and patient).

Distance (Intensity and StP distance).

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No use of ionizing radiation is justified if No use of ionizing radiation is justified if there is no benefit.there is no benefit.

All applications must be justified.All applications must be justified.

This implies: All, even the smallest This implies: All, even the smallest exposures are potentially harmful and exposures are potentially harmful and the risk must be offset by a benefit.the risk must be offset by a benefit.

The decision to adopt or continue any human activity involves a review of benefits and disadvantages of the possible options• E.g.: choosing between the use of X Rays or

ultrasound

Most of the assessments needed for the justification of a practice are made on the basis of experience, professional judgement, and common sense.

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Need to evaluate the benefits of Need to evaluate the benefits of radiation - an easy task in the case of radiation - an easy task in the case of nuclear medicine.nuclear medicine.

Radiation is the diagnostic and Radiation is the diagnostic and therapeutic agent.therapeutic agent.

Assessment of the risks requires the Assessment of the risks requires the knowledge of the dose received by knowledge of the dose received by persons.persons.

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When radiation is to be used then the When radiation is to be used then the exposure should be optimized to exposure should be optimized to minimize any possibility of detriment.minimize any possibility of detriment.

Optimization is “doing the best you can Optimization is “doing the best you can under the prevailing conditions”.under the prevailing conditions”.

Need to be familiar with techniques and Need to be familiar with techniques and options to optimize the application of options to optimize the application of ionizing radiation - this is really the main ionizing radiation - this is really the main objective of the present course.objective of the present course.

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.

Means that doses should be “As Low As Reasonably Achievable” ALARA, economic and social factors being taken into account” compatible with achieving the required objective.

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As Low As Reasonably Achievable This means radiation exposure should be

limited as much as possible keeping in mind the risk-benefit relation of radiation and its applications. For example, it is unreasonable to refuse an X-ray after a bone fracture because statistically this may shorten your life expectancy by one day. The benefits of the X-ray with its diagnostic value by far outweigh the risk associated with the radiation exposure.

Diagnostic objective Medical exposure

Image quality depends on:

Administered activity

Technical factors - equipment used- acquisition protocol- image processing &

evaluation- noise- spatial resolution

- scatter

Patient factors - size - age - disease

- movement

Justification Optimization The use of doses

limits is NOT APPLICABLE• Dose constraints

and guidance (or reference) levels ARE RECOMMENDED

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 incurred by volunteers as part of

a program of biomedical research.

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(a) (a) No patient to be administered a diagnostic No patient to be administered a diagnostic or or therapeutic medical exposure unless the therapeutic medical exposure unless the exposure exposure is prescribed by a medical is prescribed by a medical practitioner; practitioner;

(d) (d) For therapeutic uses of radiation, the For therapeutic uses of radiation, the calibration, calibration, dosimetry and quality assurance dosimetry and quality assurance requirements of requirements of the Standards be conducted by the Standards be conducted by or under the or under the supervision of a qualified supervision of a qualified expert in radiotherapy expert in radiotherapy physics.physics.

effective dose of 1 mSv/year equivalent dose to lens of the eye 15

mSv/yr equivalent dose to skin of 50

mSv/year.

ExaminationEntrance surface dose per radiograph (mGy)

Lumbar spine AP 10

Lumbar spine LAT 30

Lumbar spine LSJ 40

Abdomen, IVU and cholecystography AP

10

ExaminationEntrance surface dose per radiograph (mGy)

Pelvis AP 10

Hip joint AP 10

Chest PA 0.4

Chest LAT 1.5

From: Referral Criteria For Imaging. CE, 2000.

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

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

From: Referral Criteria For Imaging. CE, 2000.

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Dose Limits effective dose of 5mSv per year averaged over five

consecutive years equivalent dose to lens of eye of 150mSv in a year equivalent dose to extremities or skin of 500mSv in a

year.

For apprentices (16-18 years of age) effective dose of 6mSv in a year

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Female workers should notify pregnancy.

Working conditions shall be adapted to ensure that the embryo and fetus are afforded the same broad level of protection as for members of the public. .

Mr. Sharp, I am given to understand that 2 bone scans and a cardiac study done on me have given me 22 mSv whereas 20 mSv is the safe dose. I want to file legal suit against the doctor. What do you feel??

Class Activity 3