XRay Training

Who Discovered X-rays?

1895 – Wilhelm Roentgen discovered X-rays while studying luminescence produced by cathode tubes.
Because he didn’t know what they where he called them X-rays (X for unknown).
He also noticed that the rays caused photographic plates to darken.
X-ray photographs revealed the inner structure of objects.

What is an X-ray?

Basically the same thing as visible light rays
Both are wavelike forms of electromagnetic energy carried in discrete bundles called photons
The difference is the energy level of the individual photons - expressed as the wavelength of the rays

What is an X-ray?

Visible light and X-ray photons are both produced by the movement of electrons in atoms.
Electrons occupy different energy levels (orbitals) around the atom’s nucleus.
When electrons drop to a lower orbital it releases energy in the form of a photon.
The energy of the photon depends on how far the electron dropped between orbitals.

Radiation Physics

Radiation is “energy in transit” in the form of high speed particles and electromagnetic waves.
At lower levels, this energy makes up visible light, radio and television waves, UV light, and microwaves.
Because these energies do not carry enough energy to separate molecules or remove electrons from orbits, they are classified as non-ionizing radiation.

Radiation Physics

Ionizing radiation is radiation with enough energy to remove electrons from their orbit.
This causes the atom to become charged or ionized.
This energy is emitted in the form of waves or particles.

Ionizing Radiation

Type	Atomic Mass	Electrical Charge	Range in Air	Range in Body Tissue	Attenuation
Alpha	4	+2	<inch	Unable to penetrate skin	Stopped by a sheet of paper or skin
Beta	1/1840	-1	Several feet	1/3 inch	Stopped by a thin sheet of aluminum
Gamm/X-ray	N/A	None	Passes through	Passes through	Thick lead or steel
Neutron	1	Neutral	Hundreds of feet	About 10% goes through	Several feet of water or plastic

X-ray and Gamma Ray Properties

Charge: None

Mass: None

Velocity: 3 x 10⁸ m/s

Origin:

Gamma Rays: originate from a nucleus undergoing radioactive decay.
X Rays: originate in the electron cloud surrounding the nucleus. This includes bremsstrahlung x-rays.

The fundamental characteristics of X-rays are…

Electromagnetic radiation
Originate in energy shells of atom
Produced when electrons interact with a target

What are X-rays?

X-rays are produced when accelerated electrons interact with a target, usually a metal absorber, or with a crystalline structure. This method of x-ray production is known as bremsstrahlung.
The bremsstrahlung produced is proportional to the energy of the accelerated electrons used to produce it and the atomic number (Z) of the target (absorber).

How are X-rays Produced?

When fast-moving electrons slam into a metal object, X-rays are produced. The kinetic energy of the electron is transformed into electromagnetic energy.

X-ray Equipment

Many different types of machines produce x-rays (intentionally or inadvertently).

X-ray Diffractometers
X-ray Fluorescence
Electron Microscopes
Photoelectron spectrometers

Radiation Basics

X-rays are known as ionizing radiation because x-rays possess sufficient energy to remove electrons from the atoms with which x-rays interact
There are three quantities primarily used to describe the intensity of an x-ray beam

Biological Effects of X-rays

Injury to living tissue results from the transfer of energy to atoms and molecules in the cellular structure.
Atoms and molecules become ionized or excited.
These excitations and ionizations can:

Produce free radicals
Break chemical bonds
Damage molecules that regulate vital cell processes

Prompt and Delayed Effects

Radiation effects can be categorized by when they appear.
Prompt, acute effects – skin reddening, hair loss and radiation burns which develop soon after large doses of radiation are delivered over short periods of time.
Delayed effects – cataract formation and cancer induction that may occur months or years after a radiation exposure.

Prompt Effects

Will develop within hours, days or weeks depending on the size of the dose. The larger the dose the sooner the effect will occur.
Limited to the site of the exposure.

Prompt Effects

The skin does not have receptors that sense radiation exposure. No matter how large a radiation dose a person receives, there is no sensation at the time the dose is delivered.
Some people who have received large doses claim to feel a tingling at the skin, however it is believed that the tingling is due to static charge at the skin surface rather than the direct sensation of radiation exposure.

Delayed Effects

Cataracts – induced when a dose exceeding 500 rems is delivered to the lens of the eye. Radiation induced cataracts may take months or years to appear.
Extremely unlikely to receive a substantial dose to the eye working with XRD (X-ray Diffraction) units.

Old handheld fluoroscope showing imaging of hand. What you don’t see is the x-ray beam being shot through hand and directly into fluoroscope. What's behind the fluoroscope?

Delayed Effects

Studies have shown that people exposed to high doses of radiation have a risk of cancer induction.
Studies demonstrate that cancer risk is linearly proportional to the dose of radiation exposure.
Radiation induced cancers may take years to appear.

Cancer Risk Estimates-Putting Risk into Perspective

1 in a Million chance of death from activities common in society:

Smoking 1.4 cigarettes in a lifetime (lung cancer)
Eating 40 tablespoons of peanut butter (aflatoxin)
Spending two days in New York City (air pollution)
Driving 40 miles in a car (accident)
Flying 2500 miles in a jet (accident)
Canoeing for 6 minutes (drowning)
Receiving a dose of 10 mrem of radiation (cancer)
(1/500th of the allowable dose as a radiation worker)

Personnel Exposure Limits

Annual Dose Exposure limits have been established by the Nuclear Regulatory Commission based on the recommendations of national and international commissions.
Exposures at or below these limits should result in no exposure effects

Whole Body – Radiation Workers	5 rem/year (5,000 mrem/yr)
Extremities – Radiation Workers	50 rem/year (50,000 mrem/yr)
General Public	0.1 rem/year (100 mrem/yr)

Exposure Effects

1,000 rad – second degree burns
2,000 rad – intense swelling within a few hours
3,000 rad – completely destroys tissue
400 rad – acute whole body exposure is LD 50/60*

*LD 50/60 – lethal to 50% of population within 60 days without medical intervention

Radiation Protection Techniques

X-ray Diffraction Systems

Analytical X-ray machines are used extensively for microstructure analysis.

When a sample is irradiated with a parallel beam of monochromatic x-rays, the atomic lattice of the sample acts as a 3-dimensional diffraction grating, causing the beam to be diffracted to specific angles related to the inter-atomic spacings.

Analytical X-ray Systems

This x-ray pattern is recorded by film or angular x-ray detectors.

By measuring the angles of the diffraction, the inter-atomic spacing of the material can be determined and used to identify the crystallographic structures of the material.

X-ray Diffraction

X-ray diffraction units consist of:

X-ray generator
Goniometer (optical instrument for measuring crystal angles)
Sample holder
X-ray detector

X-Ray beam impinges sample and scattered radiation is measured by radiation detectors located at various angles with respect to the sample.

Causes of Accidents

Although it is rare that an injury or accident occurs when using an analytical x-ray system, some causes include...

Poor equipment configuration
Manipulation of equipment when energized
Equipment failure – shutter failure/warning light failure
Inadequate training – incorrect use of equipment
Violation of procedures – over-riding interlocks

Preventing Accidents

Know location and/or presence of primary and diffracted beams at all times.
Provide and inspect shielding.
Do not perform maintenance without confirming the beam is not energized.
Perform routine check of safety devices.
Don’t put your body parts in the beam path!

Principle Hazard
Analytical XRD Units

Analytical X-ray units make use of a very narrow collimated x-ray beam.

Exposure of the skin to the primary beam may result in very high doses within fractions of a second that will result in severe radiation burns.

Open Beam XRD Units

This is an OLD open beam X-ray diffraction device. New diffraction X-Ray devices for FSU research must be contained in a fully shielded interlocked cabinet or housed in their own dedicated room.

Open Beam XRD Units

The x-ray tube, detector, and sample are contained in a housing that provides shielding to the user and others in the lab. The access doors are interlocked and will shut off the x-rays when opened. The large viewing area is made possible by using leaded glass or Plexiglass that shield the user from harmful x-rays.

Possible Radiation Intensity Near Analytical X-ray Equipment

Location	Dose Rate
Primary beam at tube port	Several thousand rems per second
Primary beam at 10 cm collimator	Several hundred rems per minute
Scatter radiation near sample	Hundreds of mrems per hour
Outside the x-ray housing	Indistinguishable from background radiation

Precautions and Guidelines

Prior to operating the systems, complete proper training and instruction from an authorized user.
Never assume the unit was left in a safe working condition by the previous user.
Do not by-pass any safety device or interlock.
Know the location and/or presence of primary and diffracted beams at all times.
Do not leave the unit unattended when operational.
Know what you are doing and where to expect problems.