aot l radiationhazards

7/31/2019 AOT L RadiationHazards

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Radiation hazards in orthopaedictrauma care


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Learning outcomes

Describe the physical and biological facts of radiation.

Demonstrate an understanding of how and when to use x-rays duringorthopaedic trauma procedures.

Protect patients, teams and surgeons from radiation during surgery.


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Outline

Physical facts

Biological facts

How to protect team and surgeon

C-arm and x-ray tube position Protective clothing

Efficient use of radiation

Planning

Positioning

"C-arm attitude"


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Physical facts

Radiation is energy from electromagnetic waves

X-radiation = ionizing radiation

Wavelength: 150.01 nanometer (nm)

Frequency: 2.5x10176x1019 Hz

Energy: 1 eV250 keV

Units of measurement

Rem:energy delivered by x-radiation

Gray(1 Gy = 1 Joule/kg):energy deposited in material, reflects physical effect

Sievert (1 Sv = 1 Joule/kg):dose equivalent, reflects the biological effect


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Units

100 rem = 1 Gy = 1 Sv

100 milirem = 1 mGy = 1 mSv (=1000 Sv)

Normal exposure

Cosmic ray in high-altitude flights: 0.0010.01 mSv/hour

Natural background radiation: 0.01 mSv/day

In USA: natural cosmic radiation is 0.27 mSv/year

Physical facts


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Physical facts

Medical exposure

Chest x-ray: 0.1 mSv

CT scan head: 1.5 mSv

CT whole body: 9.9 mSv

Cardiac CT angio: 6.713 mSv


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Accidental exposure

Radiation sickness: 5001000 mSv

Radiation from nuclear bomb: 5001000 mSv

Physical facts


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Somatic effects

determined by dose Early effect: radiation sickness from 5001000 mSv

Late effect: leukemia, thyroid cancer, radiation cataract

Below certain threshold, no increased risk ofradiation-induced problems

Stochasticeffectsnot determined by dose (chance)

Cumulative damage, no threshold

Late effect, eg, thyroid cancer, leukemia

Biological factsionizing radiation


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85% of papillary carcinomas = radiation induced

Carcinogenic dose of radiation to induce thyroid carcinoma = 100 mSv

Threshold value per year: Thyroid 300 mSv

Eye 150 mSv

Hand 500 mSv

Biological facts


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Increased exposure of surgeon, patient, and team to

radiation by minimally invasive procedures

Intramedullary (IM) nailing

Percutaneous K-wire fixation

Vertebroplasty

MIPO

Modern orthopaedic trauma surgery


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K-wire

distal radiusIntramedullary nail External fixator lumbar spine

Average radiation dose Sv (1/1000 mSv)

Eye 1.1 Sv 19.0 Sv 49.8 Sv

Thyroid 1.1 Sv 35.4 Sv 55.5 Sv

Hand 3.1 Sv 41.7 Sv 117.0 Sv

Gonads - - -

Safety regulation limits radiation exposure on professionals to 300500 mSv/y

Exposure during MIO proceduresFuchs M et al (1998) Intl Orthopedics


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How to protect staff and surgeon

Physical facts

X-ray tube position

Factors affecting patient and staff doses

Protection measures


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Absorption and scatter:

For every 1000 photons reaching the

patient

~100200 are scattered

~ 20 reach the image detector

rest are absorbed (= radiation dose) by thepatient

In radiology, radiation scatter is mainly

directed toward the source

Physical facts

The main source of radiation for the team and surgeon

during fluroscopy is scattered radiation from the patient


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X-ray tube position

Scatter-dose rate is lower when distance between patient and surgeon increases


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Stand at safe distance fromimage intensifier and x-raytube!

Further away from patient,lower rate of scatteredradiation

Example of dose rate around mobile C-arm


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3-month period: 107 consecutive operations

Radiation doses of surgeon and assistant

Surgeon always > 90 cm from beam

Assistant approx 10 cm from beam

Outer dosimeter:

Surgeon 0.0375 mSv

Assistant 0.21 mSv

Under-gown dosimeter: Surgeon 0.0 mSv

Assistant 0.05 mSv

Who receives the most exposure?Tasbas BA et al (2003) Arch Orthop Trauma Surg


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22 procedures of IM nailing of long bones

Senior group (12) vs junior group (10)

Dosimetry data and fluorometric time

Fluorometric time statistically greater for junior group

Experience and exposure during IM nailingBlattert TR et al (2004) Arch Orthop Trauma Surg


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X-ray tube position


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X-ray tube position

Tube position below OR table reduces high-dose rates to eye lens

Best configuration

intensifier up

x-ray tube down

intensifier up

x-ray tube down

Radiation dosereduced tolens by 3 or

more times


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X-ray tube position

Scattered dose is higher at the x-ray tube side

Stand on intensifier side

Staff should stay clear of the x-ray tube area during fluoroscopy


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Risks:

Thyroid exposure

Source side (x-ray tube) 34 times higher than on intensifier side

Dose rates to torso

0.53 mSv/min on source side

0.02 mSv/min on intensifier side

X-ray tube positionRampersaud YR et al (2000) Spine


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Patient size increases skin dose and scattered radiation

Patient skin doseand level ofscatteredradiationincreases

substantially

Use additional protective devices or keep a safe distance from large size patients

Factors affecting staff and patient doses
http://www.bar-ray.com/images/apron/close/collar-unattached2_Resized.jpghttp://www.bar-ray.com/images/products/close/basics_Resized.jpg


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A smaller image intensifier diameter can increase patient entrance dose

Dose 150

Dose 200

Intensifier diameter Relative patient entrancedose

32 cm (12 in)

22 cm (9 in)

16 cm (6 in)

11 cm (4.5 in)

Dose 100

Dose 300

Factors affecting patient doses


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Important parameters: Focuspatient skin distance

Patientimage intensifier distance

Patient dose will increase if:

Focusskin distance is short

Patientimage intensifier

distance is large

Reduce scatter: place patient close toimage intensifier and far from x-ray tube

Factors affecting staff and patient doses

dose


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Specific body exposure

Hands have greatest exposure risk

Eyes: first determinant of workload

(radiation cataract)

Thyroid: 85% of papillary carcinoma are

radiation induced

Carcinogenic dose of radiation to induce thyroid

carcinoma = 100 mSv

[Devalla KL, Guha A, Devadoss VG 2004]

Image on the right courtesy of Fuezesi I,Gastroenteropathology UMG, Goettingen


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Apron

AP: decreased 16-fold

lateral: decreased 4-fold

Thyroid collar

2.5-fold further decreases

0.15 mm lead-equivalent gogglesprovide 70% attenuation of radiographic beam

6064% protection at 5258 KV

Practical radiation protection
http://www.bar-ray.com/images/apron/close/collar-unattached2_Resized.jpghttp://www.bar-ray.com/images/products/close/basics_Resized.jpg


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Shielding, leaded aprons,gloves, thyroid protectors, etc,must be available in the OR!

They must always be properly

used!

Practical radiation protection
http://www.bar-ray.com/images/apron/close/collar-unattached2_Resized.jpghttp://www.bar-ray.com/images/products/close/screen10_Resized.jpghttp://www.bar-ray.com/images/products/close/basics_Resized.jpg


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Technical contributions to radiation dosereduction

Integrated lasers on both x-ray tube andimage intensifier,easier positioning, reduce radiationexposure

Pulse acquisition

Virtual patient anatomy selection ensurecorrect dose is given to correspondingbody area

Selectable dose rate according topatient size

reduced dose

reduced dose

standard dose

increased dose


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Clinical C-arm application: C-arm attitude

Landmarks (floor, body)

Laser

Pulsed acquisition

Distance

Position of x-ray tube

Protection
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Clinical C-arm applicationDHS


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Summary

Radiation hazard can be reduced by:

C-arm orientation

Positioning x-ray tube underneath the patient

Lateral view: stay away from x-ray tube

Keep x-ray tube at maximal distance to the patient

Keep image intensifier close to the patient Do not overuse magnification

Considering scatter radiation

Wearing protective clothing

Keeping distance

Keeping your hands out of the beam!

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