X-ray Physics & Biological Risks

HERTAULT A, CLOUGH R, SPEAR R, MARTIN-GONZALEZ T, SOBOCINSKI J,

AZZAOUI R, HAULON S

Physics Basics

Electromagnetic Waves + Photons

Move in straight lines

Wavelength 0.03-10 nm

Transport Energy

eV

Medical applications: 10-150 KeV

Visible light around 2 eV

2

Physics Basics

Interaction with matter

No Interaction Diffusion Absorption

With Energy

Loss Without

Energy loss

Transmission of Energy

3

Compton Effect Photoelectric Effect

Physics Basics

Interaction with matter

Diffusion Absorption

No IMAGES without RISKS

4

Ionization

Biological Risks

Image Formation

Compton Effect Photoelectric Effect

X-Ray Production 5

Current is applied

Electrons are accelerated

Projected onto the anode, which creates:

99% = Heat

1% = Photons

Cooling system

Overheating

Vacuum

1%

X-ray beam

99 %

Heat

Applied

Energy

Image Formation

Tube

Detector

Patient &

Table

Uniform beam

Transmission of

Energy

Inhomogeneous

beam

Interaction with

matter

Image Formation

6

Image Formation 7

High density (Bone)

Absorption strong

Transmission low

Low density tissue (Lung)

Absorption low

Transmission strong

Intermediate density

(Soft tissue)

Absorption intermediate

Transmission intermediate

X-ray Production Is Beam Energy homogeneous?

8

0 20 40 60 80 100 120

0

0.2

0.4

0.6

0.8

1.0

Energy (keV)

Nor

mal

ized

Cou

nts

X-Ray Production

What type of X-Rays are there?

9

Absorption by Patient

No image formed

Partially absorption

= Image produced

Crossed without interaction

No image formed

„Soft“ X-rays

„Intermediate“ X-rays

„Hard“ X-rays

Low KeV – Low energy

X-Ray Production

Spectral filtration

10

Add a Cu filter

„Soft“ X-rays

Modulation of energy

„Hard“ X-rays

„Intermediate“

X-rays

Biological Risks

Transmission of energy:

Ionization

Two mechanisms:

Direct:

DNA

Proteins

Indirect:

Formation of free radicals

Scatter radiation

Secondary

source

Patient Patient Medics

Primary

beam

11

Deterministic Effects

Patient

Medics

THRESHOLD Onset can be

predicted

Severity is

well-correlated

to Intensity

Radiation

Dermatitis

Incidence 1/10 000 to 1/100 000

Severity can be

predicted

Real Incidence = Unknown…

Delayed injuries On patients

Back

Lack of

awareness

12

Deterministic Effects Patient

13

Deterministic Effects Patient

Koening, AJR, 2001

Evolve over time

6 months 7 months 10 months

22 months 23 months

14

Deterministic Effects: Risk Factors

Prolonged exposure on the

same area

Overlapping skin folds

Repeated exposure on the

same areas

Anterior part of the neck & Tibias

Flexor surface of extremities

Active smoking

Malnutrition

Diabetes Mellitus

Hyperthyroidism

Obesity

Skin fold

Compromise Skin integrity

Linked to the

patients Linked to the

procedure

Linked to the

topography

Ataxia Telengectasia

Lupus Erythematosus

Sclerodermia

Specific Background

Actinomycin

Doxorubicin

Bleomycin 5FU

Methotrexate

Drugs

15

Deterministic Effects Medics

Posterior

Subcapsular

Disease > 50%

Interventional

Cardiologist

> 40% nurses &

radiographers in

the OR

< 10% in control

unexposed

population

vs.

Vano JVIR 2013

16

Deterministic Effects Medics

45 µSv to the

head

< 10 µSv under the

lead apron vs.

Albayati EJVES 2015

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Stochastic Effects

Patient

Medics

NO THRESHOLD Onset cannot be

predicted

Severity is not

correlated to

Intensity

Solid Cancers or

Leukemia

Severity cannot be

predicted

Incidence??

Risk remains over

lifetime

Likelihood increases

with exposure

Malformation in the

offspring

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Stochastic Effects

Roguin Am J Cardiol 2013

Andreassi FASEB 2005

31 cases Incidence > Gen. Population?

31 Interventional

cardiologists

31 matched medical

cardiologists vs.

DNA

damages Years of

practice

19

Dose estimators (I)

X-ray production

Foot on pedal

Poor correlation

Fluoroscopy time

The sum of the air kerma at

the interface between beam

and patient skin

Good estimator of

deterministic risk

Cumulative dose

AK x cross-sectional area

Widely used

Good estimator of stochastic risk

Dose area product

Energy delivery by the beam

to the air at the reference

point

Air Kerma

min

Gy

Gy.cm²

CAK > 5 Gy

FT > 60 min

Gy

PDS > 500

Gy.cm²

Stecker JVIR 2009

20

Dose estimators(II)

ESD

Deterministic

effects

mGy

ED

Stochastic

effects

mSv

PSD

Absorbed dose to a specific organ

x

Specific sensitivity to X-rays

PSD > 2 Gy

1 Gy = 1 Sv

21

Summary

X-Rays = Electromagnetic waves + photons

Production of images means transfer of energy

X-Rays = Ionising radiation

Biological risk

Need for dose and risk estimators

22

X-ray Physics & Biological Risks

HERTAULT A, CLOUGH R, SPEAR R, MARTIN-GONZALEZ T, SOBOCINSKI J,

AZZAOUI R, HAULON S