Lecture 1

Radiation Protection for Cardiologists

John SaundersonRadiation Protection AdviserPRH ext 6690

Plan

• 3 afternoons of lectures (30/1/04, 13/2/04, 26/3/04)

• 1 afternoon in Cath Lab with phantoms and dosemeters (2/4/04)

Radiation Protection?

• The law – IRMER – “adequate training”

• Higher Medical Training Curriculum for Cardiology – April 2003

• Angiography = 0.8% of X-ray procedures, but 10% of X-ray dose

• Radiation can be dangerous

Why bother?

700 CANCER CASES CAUSED BY X-RAYS

X-RAYS used in everyday detection of diseases and broken bones are responsible for about 700 cases of cancer a year, according to the most detailed study to date.

The research showed that 0.6 per cent of the 124,000 patients found to have cancer each year can attribute the disease to X-ray exposure. Diagnostic X-rays, which are used in conventional radiography and imaging techniques such as CT scans, are the

largest man-made source of radiation exposure to the general population. Although such X-rays provide great benefits, it is generally accepted that their use is associated with very small increases in cancer risk.

30 January 2004

Syllabus• Physics & hazards of ionising radiation to

patients & staff• Statutory requirements for Medical

Exposures• Equipment• Factors affecting patient & staff dose• Important aspects of cardioradiology

• Above covers IRMER “Core of Knowledge”.

www.hullrad.org.uk

Radiation Hazards

Wilhelm Roentgen

• Discovered X-rays on 8th November 1895

Henri Becquerel

• Discovered radioactivity on 26 February 1896

Frau Roentgen’s hand, 1895

Colles’ fracture 1896

Dr Rome Wagner and assistant

”First radiograph of the human brain” 1896

In reality a pan of cat intestines photographed by H.A. Falk (1896)

First Reports of Injury

Late 1896

Elihu Thomson - burn from deliberate exposure of finger

Edison’s assistant - hair fell out & scalp became inflamed & ulcerated

Mihran Kassabian (1870-1910)

Sister Blandina (1871 - 1916)

1898, started work as radiographer in Cologne

held nervous patients & children with unprotected hands

controlled the degree of hardness of the X-ray tube by placing her hand behind of the screen.

Sister Blandina

After 6 months strong flushing & swellings of hands

diagnosed with an X-ray cancer,

some fingers amputated

then whole hand amputated

whole arm amputated.

Sister Blandina

1915 severed difficulties of breathing

extensive shadow on the left side of her thorax

large wound on her whole front- and back-side

Died on 22nd October 1916.

First Radiotherapy TreatmentEmil Herman Grubbé

• 29 January 1896

• woman (50) with breast cancer

• 18 daily 1-hour irradiation

• condition was relieved

• died shortly afterwards from metastases.

Radiotherapy 1899Basal Cell Carcinoma

A) Before B) 30 years on

William Rollins

• Rollins W. X-light kills. Boston Med Surg J 1901;144:173.

• Codman EA. No practical danger from the x-ray. Boston Med Surg J 1901;144:197

Early Protective Suit

•Lead glasses

•Filters

•Tube shielding

•Early personal “dosemeters”

•etc.

Protection Progress

• 1898 Roentgen Society Committee of Inquiry

• 1915 Roentgen Society publishes recommendations

• 1921 British X-Ray and Radiation Protection Committee established and reported

• 1928 2nd International Congress of Radiology adopts British recommendations + the Roentgen

• 1931 USACXRP publishes first recommendations (0.2 r/d)

• 1934 4th ICR adopts 0.2 Roentgens per day limit

Life Span Study

• About 94,000 persons, • > 50% still alive in 1995• By 1991 about 8,000 cancer deaths 430 of these attributable to radiation• 21 out of 800 in utero with dose > 10

mSv severely mentally retarded individuals have been identified

• No increase in hereditary disease• http://www.rerf.or.jp/eigo/glossary/lsspopul.htm

Mechanisms of Radiation Injury

• LD(50/30) = 4 Gy280 J to 70 kg man1 milli-Celsius rise in body temp.drinking 6 ml of warm tea

i.e. not caused by heating, but ionisation.

Radiation Quantities and Units

• Absorbed dose • Equivalent dose• Effective dose• others .

Absorbed Dose (D)

• Amount of energy absorbed per unit mass [D=d/dm]

• 1 Gray (Gy) = 1 J/kg• Specific to the matierial, e.g.

– absorbed dose to water– absorbed dose to air– absorbed dose to bone.

Typical Values of D

• Radiotherapy dose = 40 Gy to tumour (over several weeks)

• LD(50/30) = 4 Gy to whole body (single dose)

• Typical 1 minute screening = 20 mGy skin dose

• Chest PA = 160 uGy skin dose• Threshold for transient erythema = 2

Gy .

Equivalent Dose (HT,R)

• Absorbed dose to tissue x radiation weighting factor [HT,R = wR.DT,R]

• Units are Sieverts (Sv)– All photons, electrons and muons, wR = 1– Neutrons, wR = 5-20 (depending on energy)– Protons, wR = 5– Alpha particles, wR = 20

• For X-rays and gamma rays, 1 Gy = 1 Sv• For beta particles and positrons, 1 Gy = 1 Sv• For alphas, 1 Gy = 20 Sv .

Effective Dose (E)

• Sum of equivalent doses to each tissue/organ x organ weighting factors [E = T wT.HT]

• Units are Sieverts (Sv)

Tissue or organ wT

Gonads 0.20Red bone marrow 0.12Colon 0.12Lung 0.12Stomach 0.12Bladder 0.05Breast 0.05Liver 0.05Oesphagus 0.05Thyroid 0.05Skin 0.01Bone surfaces 0.01Remainder 0.05

e.g. if gonads alone received 2 Gy to tissue, E = 0.20 x 2 = 0.4 Sv.

Typical Values of E

• Pulmonary angiography = 5.4 mSv• CT abdomen = 10 mSv• Conventional abdomen X-ray = 1 mSv• Chest PA = 20 uSv• Annual dose limit for radiation workers = 20

mSv• Annual background dose = 2.5 mSv

• (risk of inducing cancer or hereditary disease is proportional to Effective Dose) .

36

Others• Dose area product (Gy.cm2) - dose x field size

• Collective dose (manSv) - effective dose x number of people exposed (e.g.Angiography gave 1,923 manSv in UK in 2000)

• Exposure (R or C/kg) - charge produced in 1 kg of air• Air kerma (Gy) - energy released in 1 kg of air (dose meters

usually read in air kerma)• Dose equivalent (Sv) - superseded by equivalent dose • Effective dose equivalent (Sv) - superseded by effective

dose• Ambient dose equivalent (Sv) - dose a particular depth

(often used for personal dosimeter results)• CTDI (mGy), DLP (mGy.cm)• Committed effective dose (Sv) – from ingested

radionuclides over 50 y .

Old Units

• 100 rad = 1 Gy = 100cGy• 100 rem = 1 Sv• 100 R 0.9 Gy

Main Units for Cardiology• Effective dose in mSv • Skin dose in mGy or mSv• DAP in Gy.cm2

Two Types of Effect

•Deterministic effects (“threshold effects”)

•Stochastic effect (“chance effects”) .

Deterministic Effects• Caused by significant cell necrosis

• Not seen below a threshold dose

• Above the threshold, the bigger the

dose, the worse the effect

• Do not accumulate over long term .

5000

3500

3000

2500

2000

500 500150

500

500

1000

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Cataracts

Perm

. male

sterility

Temp.

epilation

Fem

alesterility

Transienterythem

a

Lens damage

B. m

arrowsupression

Temp. m

alesterility

Fetal death

1 min fluoro

skin dose

mill

i-Gra

y

From FDA, Sept 1994, “Avoidance of serious x-ray induced skin injuries to patients during fluoroscopically-guided procedures”

Effect ThresholdFluoroscopy time to reach threshold Time to

onset ofDose Typical fluoro. dose

rate of 20 mGy/minHigh-level dose rate

of 200 Gy/mineffect

Early transient erythema 2 Gy 1 hr 42 min 10 min hours

Temporary epilation 3 Gy 2½ hr 15 min 3 weeks

Main erythema 6 Gy 5 hr 30 min 10 days

Permanent epilation 7 Gy 6 hr 35 min 3 weeks

Dry desquamation 10 Gy 8 hr 50 min 4 weeks

Invasive fibrosis 10 Gy 8 hr 50 min

Dermal atrophy 11 Gy 9 hr 55 min > 14 wks

Telangiectasis 12 Gy 10 hr 1 hr > 52 wks

Moist desquamation 15 Gy 12½ hr 1 hr 15 min 4 weeks

Late erythema 15 Gy 12½ hr 1 hr 15 min 6-10 wks

Dermal necrosis 18 Gy 15 hr 1 hr 30 min > 10 wks

Secondary ulseration 20 Gy 17 hr 1 hr 40 min > 6 wks

Example of Radiation Injury in Cardiology

•40 year old male

•coronary angiography

•coronary angioplasty

•second angiography procedure due to complications

•coronary artery by-pass graft

•all on 29 March 1990 .

Fig. A6-8 weeks after multiple coronary angiography and angioplasty procedures

Fig. B16 to 21 weeks after procedure, with small ulcerated area present

Fig. C18-21 months after procedure, evidencing tissue necrosis

Fig. DClose up of lession in Fig. C

From injury, dose probably in excess of 20 Gy .

Fig. EAppearance after skin grafting procedure .

75-year-old woman with 90% stenosis of right coronary

artery. Photograph of right lateral chest obtained 10 months after percutaneous transluminal coronary angioplasty shows area of hyper- and hypopigmentation, skin atrophy, and

telangiectasia (poikiloderma)

56-year-old man with obstructing lesion of right coronary artery.

Photograph of right posterolateral chest wall at 10 weeks after

percutaneous transluminal coronary angioplasty shows 12 x 6.5 cm hyperpigmented plaque with hyperkeratosis

below right axilla

49-year-old woman with 8-year history of refractory supraventricular tachycardia. Photographs show sharply demarcated erythema above right elbow at

3 weeks after radiofrequency cardiac

catheter ablation

48-year-old woman with history of diabetes mellitus and severe coronary artery disease who

underwent two percutaneous transluminal coronary angioplasties and stent placements within a month. Photograph of left mid back 2 months after last procedure shows well-marginated focal erythema and desquamation

69-year-old man with history of angina who underwent two angioplasties of left coronary artery within 30 hr. Photograph taken 1-2 months after last procedure shows secondary ulceration over left scapula

To prevent deterministic effects

• Keep skin dose below 2 Gy

• Keep eye dose below 500 mGy .

Stochastic Effects

• Caused by cell mutation leading to cancer

or hereditary disease

• Current theory says, no threshold

• The bigger the dose, the more likely effect

• So how big is the risk?.

Cancer deaths between 1950 and 1990 among Life Span Study survivors with significant exposure

(i.e. > 5 mSv or within 2.5 km of the hypercentre)

Dose range Number of

cancer deaths

Estimated excess death

Attributable fraction

5 - 200 mSv 3391 63 2 %

200 - 500 mSv 646 76 12 %

0.5 - 1 Sv 342 79 23 %

> 1 Sv 308 121 39 %

All 4687 339 7 %

Fraction of cancers induced by radiation

0%

10%

20%

30%

40%

50%

0 500 1000 1500

mSv

%

Fraction of cancers induced by radiation

0%

10%

20%

30%

40%

50%

0 500 1000 1500

mSv

%

Risk of inducing fatal cancer = 5 x 10-2 Sv-1

Data Sources for Risk Estimates

• North American patients - breast, thyroid, skin• German patients with Ra-224 - bone• Euro. Patients with Thorotrast - liver• Oxford study - in utero induced cancer

• Atomic bomb survivors - leukaemia, lung, colon, stomach, remainder .

ICRP risk factors

Detriment per mSv

Exposed Population Fatal cancer Non-fatal cancer Severed hereditaryeffects

Total

Adult workers 4.0 x 10-5 0.8 x 10-5 0.8 x 10-5 5.6 x 10-5

Whole population 5.0 x 10-5 1.0 x 10-5 1.3 x 10-5 7.3 x 10-5

(fetus 3.0 x 10-5 3.0 x 10-5 6.0 x 10-5)

5.0 x 10-5 per mSv 1 in 20,000 chance .

Pregnancy - Radiation Risks

Age Minimal dose (mGy) for:

(weeks) Lethality Gross malformation Mental retardation

0-1 No threshold at day 1? No threshold at day 1?

100 thereafter No effects observed to

2-5 250-500 200 about 8 weeks

5-7 500 500

7-21 > 500 Very few observed Weeks 8-15: nothreshold?

Weeks 16-25: thresholddose 600-700 Gy

To term > 1000 Very few observed Weeks 25-term: no effectsobserved

Total risk of cancer up to age 15 years following in utero exposure (per mGy)

Cancer type Fatal Non-fatal Total

Leukaemia 1.25 10-5 1.25 10-5 2.5 10-5

Other 1.75 10-5 1.75 10-5 3.5 10-5

Total 3.0 10-5 3.0 10-5 6.0 10-5

at 8-15 weeks it is estimated that 30 IQ points are lost per 1000 mGy. Risk of heritable effects estimated at 2.4 10-5 per mGy

"Natural Risks"

Heritable disease 1 10-2 to 6 10-2

Fatal cancer to age 15 years 7.7 10-4

Lifetime cancer risk 20 10-2 to 25 10-2

For diagnostic procedures

• Doses unlikely to be high enough to cause fetal death or malformation

• Increased risk of childhood cancer• Risks must be assessed for each

individual case.

Doses in CardiologyTaken from “Real-time quantification and display of skin radiation during coronary angiography and intervention”, den Boer A, et al., Oct 2001

•332 patients

•25 - 99 Gy.cm2 dose-area product

•4 - 18 mGy effective dose

•1:5000 - 1:1100 risk of inducing fatal cancer .

Dose Area Product

•Stochastic risks approx. proportional to DAP•Skin dose is DAP / area irradiated•1 Gy.cm2 3 mGy skin dose

•1 Gy.cm2 0.2 mSv effective dose .

DAP meter reading(Gy.cm2)

Risk to patient

50 About 1 in 2000 risk of inducing fatal cancer




There is a risk of early transient erythema if the same area of skin isexposed (onset a few hours after exposure)


There is a risk of main erythema, if same area of the skin is exposed(onset about 10 days after exposure)

20/11/96

2 Gy erythema threshold 666 Gy.cm2 DAP (v. approx!!)

“Small” risks so why worry?

• Average effective dose for angiography = 6 mSv

• Risk of fatal cancer from 6 mSv only 1 in 3,300

• But, large number of patients– 321,174 angiography procedures in 2000– Therefore, high probability that radiation from

angiography will kill some patients

• So– All exposures must be JUSTIFIED– Doses to patients, and staff, must be As Low As

Reasonably Achievable (ALARA principle) .

Still to do

• Production and interaction of X-rays

• Image formation• Dose reduction – patients and staff• Legislation and guidelines• Equipment

Lecture 1

Documents

Transcript of Lecture 1