iaea training course on radiation protection for doctors (non-radiologists, non-cardiologists) using...

IAEA Training Course on Radiation Protection for Doctors (non-radiologists, non-cardiologists)

using Fluoroscopy

What can radiation do?

Answer True or False

1. It is accepted that the carcinogenic effects of radiation have a threshold.

2. For deterministic effects of radiation, the severity increases with dose.

3. Radiation risk in children is 2-3 times lower than people above 45 years.

4. Skin injuries and lens opacities are deterministic effects of radiation.

IAEA Training Course on Radiation Protection for Doctors (non-radiologists, non-cardiologists) using Fluoroscopy

L03. What can radiation do?2

Educational Objectives

• Different radiation effects

• Their probability in fluoroscopy practice

• Special concerns in children, young & pregnant females

• When used appropriately it can benefit an individual by aiding in the diagnosis of disease at an early stage where treatment may be more effective than if detected late.

• In case of inappropriate use it also has a potential to harm an individual by placing them at increased risk of radiation-induced cancer later in life.

• Benefit and Risk must be carefully balanced when X ray imaging is undertaken

CancerGenetic effectsSkin injuriesCataractInfertilityDeath

L03. What can radiation do?

Deterministic Effects(predictable and preventable)

• Cataract formation

• Skin injury

• Impaired fertility

Threshold

Stochastic and Deterministic Effects

• A stochastic effect is one where the severity of radiation damage is not related to the dose and the probability of occurrence increases with increasing radiation dose, e.g., development of cancer. There is no threshold for stochastic effects.

• A deterministic effect is one where the severity depends upon the radiation dose, e.g., skin burns. There is a threshold for deterministic effects.

You mean I can get cancer even if I am working with small amount of radiation?

This requires discussion on how radiation effects occur

Physician

Is there RADIATION in this room?

Radiation from Natural Sources

• Normally 1-3 mSv/year

• In areas of high background, 3-13 mSv/year

High dose fluoroscopy

Radiography

Relative Dose Ranges in Medical Imaging

Effects of Radiation on Cells

NucleusDouble membrane surrounding the chromosomes and the nucleolus.

Pores allow specific communication with the cytoplasm. The nucleolus is a site for synthesis of RNA making up the ribosome.

Chromosomes

Direct Effect

• Incoming photon strikes the DNA molecule and damages it; either a base pair is damaged or a support strand is damaged.

• Damage from direct effect is rare; possibly as low as 1%.

Indirect effect

• Incoming photon interacts with a water molecule

• The ionizing radiation breaks chemical bonds in the water molecule

• The water molecule fragments form highly reactive chemicals such as hydrogen peroxide and other free radicals

• These highly reactive chemicals attack the DNA molecule damaging its chemical bonds

Induction of DNA changes

radiation hits a cell nucleus!

No change

DNA mutation

DNA Mutation p a D

Cell survives but mutated

Stoch.eff.

Mutation repaired

Unviable Cell

Viable Cell

Cell death

Deterministic effects caused by cell death: burns, organ failure, death

At 3 wks At 6.5 mos Surgical flap

Following ablation procedure with arm in beam near port and separator cone removed. About 20 minutes of

fluoroscopy. Reproduced from Wagner – Archer, Minimizing Risks from Fluoroscopic X Rays, 3rd ed, Houston, TX, R. M. Partnership, 2000 21

Normal process Altered process due to mutated genes

Stochastic effects

Carcinogenesis

Hereditary effects

Effects in the embryo/foetus

Carcinogenesis

So now that you have scared me with this information, what should I do?

It is not our intent to scare you with these facts, but to educate about potential long-term risks.

OK, I agree that radiation can cause cancer, but how do I

know if I will get cancer!!!

Life Insurance Agent

Malpractice Insurance

Probability

Radiosensitivity

• Probability of a cell, tissue, or organ suffering an effect per unit dose

• Will be greater if the cell:• Is highly mitotic

• Is undifferentiated

• Younger Cells

Risk versus Age at Exposure

Estimated Risks of Radiation-Induced Fatal Cancer fromPediatric CT

David J. BrennerCarl D. EllistonEric J. HallWalter E. Berdon

AJR2001;176:289–296

Cancer risk estimate: 4–6% per 1000 mSv

(depending on projection method)

! Note: The probability best applies to a group of people and is not suitable for individual cases

LIFE SPAN STUDYAtomic Bomb Survivors

Heritable Effects

Heritable effects

• Effects to be observed in offspring born after one or both parents had been irradiated prior to conception.

Heritable effects

Descendants of Hiroshima and Nagasaki survivors

were studied

but no statistical abnormalities but no statistical abnormalities were detected.were detected.

A cohort of A cohort of 31,150 children born to parents who31,150 children born to parents who were within 2 were within 2

km of the hypocenter at the time of the bombing was compared km of the hypocenter at the time of the bombing was compared

with a control cohort of 41,066 childrenwith a control cohort of 41,066 children..

No indicator was significantly modified by parental radiation exposure.

Heritable effects

In the absence of human data the estimation of hereditary effects is based on animal studies.

ICRP publication 103

HERITABLE EFFECTS OF RADIATIONHERITABLE EFFECTS OF RADIATION

Risks to offspring following prenatal exposure:

•Whole population: 0.2% per Sv

•Adults: 0.1% per Sv

……aboveabove the prevalent the prevalent background dosebackground dose, ,

an an increment in doseincrement in dose results in a results in a

proportional incrementproportional increment in the probability of in the probability of

heritable effectsheritable effects of of 0.1-0.2% per Sv 0.1-0.2% per Sv

of doseof dose..IAEA Training Course on Radiation Protection for Doctors (non-radiologists, non-cardiologists) using Fluoroscopy

OK, I understood that these radiation effects have a probability

But, I want to know about ME, if I will get these

Do you worry about?

Not reallyYes

Yes, Very much

Do you worry about?

If you work in such a manner that you adhere to prescribed dose limits of 20 mSv per year for whole working life of 18 to 65 years, your chance of excess

cancer is 1 in 1000.

Note: The probability calculations are for a group of people and not for individual cases

That sounds interesting. Is it possible to work in such a manner that I remain within 20 mSv/yr?

It should be possible to achieve conditions so that you do not exceed ≈ 3 mSv/yr.Just wait for later information in this course

Are there reports of increased cancer incidence among doctors using fluoroscopy ?

One, Last Question!!!

Let us look into the data for other professional groups like radiologists…

(Not all specialists using fluoroscopy have traditionally interacted with safety and radiation effects professionals)

Radiologists & radiological personnel:

Eight cohorts

1. 3 from US (radiologists, Army X ray technologists, radiological technologists

2. 1 each from China, Canada, Denmark, Japan & UK

Variety of data pertaining to cancer incidence for different sites, mortality data (cancer), now also to other diseases such as cardiovascular

Variation from healthy worker effect to small increase

UK Radiologists

Around 2700 male radiologists, registered from 1897 to 1979.Standardized mortality ratio (SMR)Annual exposure 0.1 Sv before 1950, 0.05 Sv in early 1950’sCompared mortality rates and death from circulatory disease: Observed number of deaths were generally close to or lower than expected.

US Radiological Technologists

• Over 146,000, predominantly females, 73%• Total cancer death rates were lower than

expected in general population• Risks higher for those before 1950 • Relative risk of mortality from circulatory

disease higher for those starting work in earlier years [<1940=1.22, 1940’s=1.00, 1960+=1.00]

US Radiologists Study

1920-1939: Cohort with highest exposure, 15% higher mortality from cardiovascular disease than other physicians, after age 55. No information about smoking and other risk factors.

Studies of the Mortality of Atomic Bomb Survivors

An Overview of Cancer and Non-cancer Diseases

•Follow up period: 1950–2003

•86,611 cohort members

•People of both sexes and all ages

•Irradiated at different agesStudies of the Mortality of Atomic Bomb Survivors, Report 14, 1950–2003: An Overview of Cancer and Noncancer Diseases. K Ozasa et al 2012. RADIATION RESEARCH 177, 229–243 (2012)

• The sex-averaged excess relative risk per Gy was 0.42 for all solid cancer at age 70 years after exposure at age 30 based on a linear model

• The risk increased by about 29% per decade decrease in age at exposure

Studies of the Mortality of Atomic Bomb Survivors

Non neoplastic diseasesSignifican risks for non-neoplastic diseases of:•Blood (ERR/Gy = 1.7) •Circulatory system (ERR/Gy = 0.11) •Respiratory system (ERR/Gy = 0.21)•Non malignant respiratory diseases (pneumonia and influenza) ERR/Gy = 0.24

Whether these are causal relationships requires further investigation

Non-neoplastic effects of Radiation

Risk of Cardiovascular

Diseases

following Radiation Exposures

Non cancer effects

Data from the LSS cohort of Japanese atomic bomb survivors (Ozasa et al 2012*)

•excess risk of mortality •ERR/Gy = 0.11, for heart disease overall

•ERR/Gy = 0.09, for cerebrovascular disease

*Ozasa et al 2012. RADIATION RESEARCH 177, 229–243 (2012)

Non cancer effects

• Threshold for effects• Heart disease: no threshold • Cerebrovascular disease: Threshold of 0.5 Gy

However, there is considerable uncertainty about the shape of the dose response at doses below 0.5 Gy

There are excess risks of heart disease for radiotherapy patients with average heart doses of 1-2 Gy (single dose equivalent, after correction for fractionation effects).

Excess risks of cardiovascular disease only become apparent 10-20 years after exposure at low doses. Long follow-up times are therefore required for assessment of risk

May involve small children, young females and pregnant patients

Radiosensitivity In Children and Young Patients

• Age is a primary determinant of radiosensitivity– the younger the patient, the higher the radiosensitivity

• Breast of 15 year old is 15 times more sensitive to radiocarcinogenesis than the breast of 45 year old

Mortality excess per Sv (BEIR VII 2005)

0 10 20 30 40 50 60 70 80 90

Year of exposure

Females

674 children who underwent cardiac catheterization due to congenital anomalies, between the years 1950-1970 Expected number of malignancies for all sites was 4.75, while the observed number was 11.0

ICRP statement in its last 2007 recommendations

• The available data on possible excess in non-cancer diseases (e.g., cardiovascular disorders) are judged to be insufficient to inform on risks at low doses.

L03. What can radiation do? 65

DETERMINISTIC LENS THRESHOLD AS

QUOTED BY ICRP

OPACITIES THRESHOLD

0,5 - 2,0 Sv in SINGLE EXPOSURE

5 Sv in FRAC. EXPOS. >0,1 Sv/year CONTIN.

ANNUAL RATE

5 Sv SINGLE EXPOS. > 8 Sv FRAC. EXPOS. >0,15

Sv/year CONTIN. ANNUAL RATE

CATARACT

https://rpop.iaea.org/RPOP/RPoP/Content/InformationFor/HealthProfessionals/6_OtherClinicalSpecialities/radiation-cataract/index.htm

Re-Cap

1. What can radiation do?2. Effects that have threshold3. No threshold effects - cancer, genetic4. Effects at the level of cell, DNA5. Probability of cancer, genetic effects6. Individual risk7. Radiologists, technologists8. Patients- Children, young & pregnant female

1. ICRP states that radiation induced cataract can be produced if more than 150 mSv* is received in the lens as a continuous annual rate.

2. The risk for cancer is 10%/Sv.

3. Women have slightly higher risk (increase in cancer probability per unit effective dose) than men.

*In a recent statement ICRP (Statement on Tissue Reactions Approved by the Commission on April 21, 2011) the ICRP proposed a limit of 20 mSv/yr, averaged over 5 years, not exceeding 50 mSv at any single year.

4. ICRP considers that the available data is insufficient to infer possible non-cancer diseases (e.g., cardiovascular disorders) particularly at low doses.

5. Breast of a 15 year old women is many times more sensitive to radio-carcinogenesis than the breast of a 45 year old women.

Thank you

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