RADIATION PROTECTION

Dr.P.P.MohananThrissur

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Outline

• Basis for protection, radiation risk and recommendations

• Personal dosimetry• Protection tools

Vulnerable Interventional Cardiologist

POTENNTIAL HAZARDS

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Coronary interventionalists must also have a thorough knowledge of specialized equipment, techniques, and devices used to perform PCI competently

AHA Scientific Statement - 2014Approaches to Enhancing Radiation Safety in Cardiovascular ImagingA Scientific Statement From the American Heart Association

RecommendationsAll healthcare providers who can request cardiac imaging procedures should be required to know (a) which cardiac imaging tests use ionizing radiation; (b) basic concepts related to medical radiation exposure, including the concepts of absorbed dose and effective dose; and (c) typical dose estimates for the most commonly used cardiac imaging procedures (Class I; Level of Evidence C).

All healthcare providers who will perform cardiac imaging with ionizing radiation, including interventional cardiologists and electrophysiologists, should be required to demonstrate adequate knowledge of contemporary dose-optimization techniques for patients and dose-minimization techniques for operators and staff (Class I; Level of Evidence C).

Recommendations

1.Education. of clinicians and patients

2.Justification that a particular cardiac imaging test with radiation is needed

3.Optimization of radiation exposure (choosing the smallest dose that provides high-quality images).

Lecture 6: Standards and guidance 8

Importance of training

• European Guidelines published in 2000.

• Radiologists 30-50 hours• Cardiologists 20-30 hours• Other doctors using

fluoroscopy X rays systems 15-20 hoursAvailable at:

http://europa.eu.int/comm/environment/radprot

Lecture 6: Standards and guidance 9

Cardiologist Patient Protection

Responsibilities

Advice of qualified expert Training

criteria

Optimization

Equipment design and suppliers Quality

assurance

Justification

Lecture 6: Standards and guidance 10

Limits on Patient Doses?

• There are no regulatory limits on the radiation dose a patient may receive

– Question: do you think that the benefit outweighs the risk???

Time of onset of clinical signs Time of onset of clinical signs of skin injury depending onof skin injury depending on

dose receiveddose received

SymptomsSymptoms Dose range Dose range Time of onset Time of onset

(Gy) (Gy) (day) (day)

Erythema 3-10 14-21 Epilation >3 14-18 Dry desquamation 8-12 25-30 Moist desquamation 15-20 20-28 Blister formation 15-25 15-25 Ulceration >20 14-21 Necrosis >25 >21

Ref.: IAEA-WHO: Diagnosis and Treatment of Radiation Injuries.

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X-Ray

Scatterradiation

Measures taken to reduce radiation exposure to patient will also benefit the operator/cath. lab. staff

Radiation risk

• Stochastic effect

• Deterministic effect

Deterministic vs. stochastic effects (representative, not scaled).

Picano E et al. Eur Heart J 2014;eurheartj.eht394

Radiation effectsRadiation effects

Early(deterministic only)

LocalRadiation injury ofindividual organs:functional and/or

morphologicalchanges withinhrs-days-weeks

CommonAcute radiation disease

Acute radiation syndrome

Late

DeterministicRadiation dermatitisRadiation cataractaTeratogenic effects

StochasticTumours LeukaemiaGenetic effects

Deterministic effect

• Gray is unit of exposure of radiation

• ONE CHEST X RAY 0.15 mGRAY• 10000 chest x ray • Or• 100 CT abdomen =• 30 mins to 1 hr fluoroscopy exposure

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1- 5 mSv/h

0.5 – 2.5 mSv/h

2- 10 mSv/h

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Limits on Occupational Doses (ICRP)*Annual Dose Limit

(mSv)

Effective dose, worker 20

Equivalent dose to lens of eye

150

Equivalent dose to skin 500

Equivalent dose to hands and feet

500

Effective dose to embryo or fetus

1

Effective dose, public 1*Please follow the recommendations as prescribed by your national authority

Threshold doses for some deterministic effects

0,1 Gy – detectible opacities 0,2 Gy – sterility for woman0,4 Gy – visual impairment 0,4 Gy – temporary sterility for man

0,4 Gy – depression of haematopoiesis1,0 Gy – chronic radiation syndrome2,0 Gy – permanent sterility for man

Radiation dose in coronary angiography and Intervention:

Journal of Medical Radiation Sciences

A Typical Fluoroscopic LabOverhead shields need to be positioned down next to the patient and adjacent to the image intensifier to seal scatteroff from below.

Table skirts shield the highest backscatter levels from the x-ray tube.

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To obtain the images …

• Two technologies are used:– Image intensifier– Flat panel detector

The X-ray Imaging Process

Absorption and transmission of x-rays contribute to the imaging process and patient dose.

Scattered or partially absorbed x–rays contribute to occupational exposure, but are less than 1% of the primary beam intensity.

TubeFocalSpot

Absorption

Transmission

Scatterx-rays

Primaryx-ray beam

ImageReceptor

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65.9

22.9

11.314.8

6.12.6 3.2

56.5

25.5

15.3

10.2

3.6 2.96.6

0

10

20

30

40

50

60

70

H 3000

Innova

Comparison of Philips H 3000 and Innova 2000 in PCI Characteristics of procedures & lesionsCharacteristics of procedures & lesions

%

Recommendations

1.Education. of clinicians and patients

2.Justification that a particular cardiac imaging test with radiation is needed

3.Optimization of radiation exposure (choosing the smallest dose that provides high-quality images).

Basic Radiation Safety TechniquesTime - As exposure time increases, dose accumulates -- Keep fluoro times as short as possible. A bell or buzzer will go off after 5 minutes of beam time, keep track of fluoro time, Distance - As distance from the radiation source increases, the radiation intensity decreases rapidly -- Keep patient anatomy and staff as far away from the x-ray tube port as possible

Shielding - Diagnostic x-rays are easily shielded with thin sheets -- Wear lead aprons, thyroid shields, leaded glasses and use overhead leaded shields and table skirts

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Optimization means ...

• To avoid acquiring more images than necessary:– Take care of the fluoroscopy time.– Take care of the number of series.– Take care of the number of frames per series.

• To avoid acquiring images with more quality (and more dose) than necessary:– It could be possible to accept sometimes some

noisy images in fluoroscopy and also in cine acquisitions.

ALARA rule

• As low as reasonably achievable

• Reduce number of exam • Reduce time of exam• Use alternaive

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Minimize Exposure Time

• Everything you do to minimize exposure time reduces radiation dose!!– Minimize fluoro and cine times– Whenever possible, step out of room– Step behind barrier (or another person)

during fluoro or cine– Use pulsed fluoroscopy– minimizes time

X ray tube is producing X rays

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Siemens Axiom ArtisCine normal mode20 cm PMMA177 Gy/fr (entrance PMMA)

Siemens Axiom Artis, Fluoro low dose 20 cm PMMA13 Gy/fr (entrance PMMA)

Lecture 9: Optimization of Radiation Protection in Cardiology

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The proposed reference levels for Coronary Angiography and PTCA were DAP 45 Gy•cm2 and 75 Gy•cm2; fluoroscopy time 7.5 min and 17 min and number of frames 1250 and 1300, respectively.

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Influence of operation modes: from low fluoroscopy to cine, scatter dose rate could increase in a factor of 10(from 2 to 20 mSv/h for normal size)

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Distance between patient and detector

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d

2d

Because the same energy is spread over a surface 4 times larger at a doubled distance, the same object will receive only a fourth of the dose when moved away from “d” to “2d”

Source

Doubling the distance from the source divides the dose by a factor of 4

The inverse square law

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The inverse square law

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Collimation

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Collimators use in reduce exposure

FOV 15

dose reduction 25%

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FOV 20

Collimators reduce exposure

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Anti-scatter grid

Increase DAP and skin dose x 2 timesImprove image quality

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proper filtering

improper filtering causes image deterioration

FILTERING

Filtering prevents image saturation in low absorption areas

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Optimization requires……….

• Knowledge of factors contributing to patient and staff radiation dose

patient factors procedural factors equipment (machine) factors

• Knowledge of dose reduction capabilities of our X ray system

• Periodic update of our clinical and technical working protocols

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• Optimization is especially important in more complex PTCA procedures

chronic total occlusion bifurcation lesion degenerated saphenous

vein graft lesion lesion in severely

tortuous vessel ostial lesion

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Exposure variation in exposure rate (DAP rate) with projection

Cusma JACC 1999

Projection Fluoroscopy entrance dose

rate

(mGy/min)

Cine

entrance dose rate

(mGy/min)

AP 31 388

RAO 30° 19 203

LAO 40° 20 216

LAO 40°, Cran 30° 80 991

LAO 40°, Cran 40° 99 1236

LAO 40°, Caud 20° 29 341

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Optimisation

1. Use of the wedge filter on bright peripheral areas2. 2-3 sequences (except for difficult anatomic details)3. 12.5-15 frames/s (25-30 only if heart rate exceeds

90-100 bpm or in paediatric patients) 4. 60 images per sequence at average (12.5-15 fr/s)

except if collaterals have to be imaged or in case of slow flow

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Basic Radiation Protection

• Time (T), Distance (D), and Shielding (S)

• Time– minimize exposure time• Distance– increasing distance• Shielding– use shielding effectively;

portable and pull-down shields, protective aprons; stand behind someone else

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1- 5 mSv/h

0.5 – 2.5 mSv/h

2- 10 mSv/h

Lecture 7: Occupational exposure and protective devices

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Radiation Monitoring Badge

Plastic filter Metal filters Open windows

Open window

Lecture 7: Occupational exposure and protective devices

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The use of electronic dosimeters to measure occupational dose per procedure helps in the optimization

Lecture 7: Occupational exposure and protective devices

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Types of Personal Radiation Monitors• Film• Thermoluminescent dosimeters (TLDs)• Optically stimulated luminescence (OSL)

dosimeters• Electronic personal dosimeters

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Advantages and Disadvantages of Personal Radiation Monitors

• Electronic dosimeters— insensitive to heat, no permanent record, minimum dose > 0.1 mSv, no imaging capability, calibration can be difficult, must rely on employee for care of device (somewhat delicate), employee must read-out dosimeter and record results, weekly or monthly readout

Multiple BadgeFluoroscopic Dosimetry

Effective dose equivalent is calculated for multiple badge wearers using the ANSI formula as required by CT State DEP regulatory guidance.

Effective Dose Equivalent = (0.11 x collar badge) + (0.89 x waist badge)

An American National Standard (ANSI)

Criteria for Performing Multiple Dosimetry

Protection tools

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Personal protective equipment

• Registrants and licensees shall ensure that workers are provided with suitable and adequate personal protective equipment.

• Protective equipment includes

• lead aprons, thyroid protectors, protective eye-wear and gloves.

• The need for these protective devices should be established by the RPO.

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Weight: 80 gramsLead equivalent: 0.75mm front and side shields leaded glass

Lead apron typically attenuates >90%Vest-Skirt Combination distributing 70% of the total weight onto the hips leaving only 30% of the total weight on the shoulders.

Option with light material reducing the weight by over 23% while still providing 0.5 mm Pb protection at 120 kVp

C. Radiation Protection and How does it Work?

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0.25 mm lead

60 kV; 100% 2 - 3 %

100 kV; 100% 8 - 15 %

Attenuation measured with lead apronsAttenuation measured with lead aprons

X ray beam filtration has a great influence!!

Thyroid collar

• Standard 0.5mm lead apron• Protect you from 95%• FROM RADIATION EXPOSURE

Wear Protective Eyewear

“In the 59 interventional radiologists aged between 29 and 63 (median age 35), PSC cataracts were found in five participants and an additional 22 had evidence of PSC changes”

46% experienced changes in the eyes

G. Eyewear

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DETERMINISTIC LENS THRESHOLD AS QUOTED BY ICRP

OPACITIES THRESHOLD

>0.1 Sv/year CONTINUOUS ANNUAL RATE

>0.15 Sv/year CONTINUOUS ANNUAL RATE

CATARACT

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UP TO 2 mSv IN LENS COULD BE RECEIVED IN A SINGLE PROCEDURE

if protection tools are not used

WITH 3 PROCED./DAY IT IS POSSIBLE TO RECEIVE 1500 mSv/year

IN FOUR YEARS WILL BE POSSIBLE TO HAVE LENS OPACITIES

Lecture 7: Occupational exposure and protective devices

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Radiation Protection of HandsBest way to minimize dose to fingers and hand:Keep your fingers out of the beam!!!

Dose rate outside of the beam and on side of patient opposite X ray tube:

Very low compared to in the beam!!!

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Protective Surgical Gloves

• Minimal effectiveness• Transmission on the order of 40% to 50%, or more• Costly ($40 US), not reusable• Reduces tactile sensitivity• Dose limit for extremities is 500 mSv• Hands on side of patient opposite of X ray tube so

dose rate is already low compared to entrance side• Lead-containing disposable products are

environmental pollutants

H. Gloves

ProteXProGuard

2 Thicknesses

Non-reactive Latex

Anatomically correct

Resterilize up to 4x

Come sterile

Sizes 6-9 w/ ½ sizes

Reduces Radiation

Powder Free

FDA 510(k)

Cost effective

Beaded Cuff

Thicker Feel

Premium, Higher $

Soft-Touch™ interior finish

Thinner Texture

ATTENUATION 60 KvP 80 KvP 100 KvP 120 KvPProGuard RR1, ProteX PX-10.0088” / 0.22mm

45% 35% 26% 23%

ProGuard RR2, ProteX PX-20.012” / 0.30mm

55% 43% 35% 31%

Protech Radiation Reducing Gloves

Rate of appropriateness for the four procedures.

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Procedure optimization in the cath. lab.patients and staff share a lot……

– correct indications– fluoro time reduction– frame rate reduction (25 12,5/sec)– collimation/filtering– LAO cranial projection limitation – distance from X ray source – lead apron and thyroid protection– protective glasses and suspended screen

(staff)

(patient)