RAD 111 Ch 1 Radiation and it's Discovery & Ch 9 Basic Radiation Protection and Radiobiology

Date X-ray were discovered

November 8, 1895

Who discovered X-rays?

Wilhelm Conrad Röntgen, German physicist

How did Dr. Roentgen make the discovery?

Crookes Tubes

Crookes Tube Experiment

• High voltage electricity through a low vacuum tube

• Tube would glow when energized

• Energized tube was causing paper coated with BA platinocyanide to glow or fluoresce

Who’s hand did Dr. Roentgen use for the first X-ray?

• His Wife, Anna Bertha

• 15-minute exposure

What does the “X“ mean in X-ray

unknown

What did Dr. Roentgen discover with x-rays?

Could not penetration all materials, like platinum

When did Roentgen submit his article to professional society?

December 1895

a new kind of rays

What did Dr. Roentgen think about his x-ray research?

• thought only had academic value and not practical applications

• Others assemble own tubes and curiosity concentrated on imaging humans for medical reasons

When did Roentgen received Noble prize for physics?

1901

In 1898 what did they discovered x-ray cause?

biological damage, first noticed erythema then tumors and chromosol changes

Properties of X-rays

• Invisible, cannot hear, taste, or smell

• Electrically neutral

• Has no mass

• Travel at the speed of light (3x108 m/s or 186,000 miles/sec)

• Cannot be focused

• Polyenergetic

• Travel in a straight line

• Will cause some substances to fluoresce

• Can penetrate anatomy

Polyenergetic

(heterogeneous) x-ray photons have many energies

• Produced at a range of energies (controlled by kVp)

X-rays can penetrate anatomy by

Being absorbed or scattered or produce secondary radiation

• Can cause chemical or biological damage

• Can ionize cells

Quantifies

• radiation exposure

• Dose

• Biological effects

What are the two systems of radiation measurement?

• Standard system

• International system (SI)

  • More widely adopted

Roentgen (R)

The amount of ionization or electrical charge in the air (intensity of exposure)

Gy a (coulomb/kilogram)

number of electrons liberated by ionization per kilogram of air

Gy t (coulomb/kilogram)

number of electrons liberated by ionization per kilogram of tissue

Air kerma

amount of energy delivered to a given point

• not an indication of patient exposure

Absorbed Dose of RAD/GY T: Measurement of transferred radiation into the body

1 Rad = 0.01 gray → 1 gray = 100 RAD

• Often used to describe patient low dose medical radiation absorbed exposure and the potential biological effects.

Equivalent Dose of REM/SV

Takes into account the biological effects (risk)of different types of radiation

• 1 REM = 0.01 SV → 1 SV = 100 REM

A weighting factor (Wr)/quality factor is assigned to the various types of radiation.

What is X-rays, gamma rays, beta particles, electron weight factor?

1

What is protons weight factor?

2

What is fast neutrons and alpha particles weight factor?

20

Effective Dose REM/SV used to measure occupational exposure

• Risk to humans of exposure to ionizing radiation.

• The type of tissue exposed is taken into consideration

• Different tissues have different weighting factors (Wt) based on sensitivity.

  • For example: Bone surface has a tissue weighting factor of 0.01 and bone marrow has a tissue weighting factor of 0.12.

• Does not take into consideration age, gender and weight.

  • For instance, a child’s tissue and organs are more radiosensitive as a whole because of the rapidly dividing cells.

1 R =

1 RAD

1 RAD =

1 REM

RADIOACTIVITY CI/BQ

• Applicable to radioisotopes used in Nuclear medicine.

• Unstable atoms emit particles and energy from the nucleus to reach stability.

• Process called radioactive disintegration or decay.

• Half life is time required for the radiation activity to be reduced by 50%

Exposure in air measurement would be what in both systems?

Standard: Roentgen (R)

International: Gya (coulomb/kilogram) air kerma

Absorbed dose in tissue measurement would be what in both systems?

Standard: RAD (radiation absorbed dose)

International: Gyt (Gray)

Equivalent dose measurement would be what in both systems?

Standard: REM (Radiation equivalent in man)

International: Sv (Sievert)

Effective dose measurement would be what in both systems?

Standard: REM (Radiation equivalent in man)

International: Sv (Sievert)

Radioactivity measurement would be what in both systems?

Standard: Ci (Curie)

International: Bq (Becqueral)

ALARA

As Low As Reasonably Achievable

• optimization for radiological protection

Shielding broadly

radiopaque (reduce radiation) materials

Examples of radiopaque (reduce radiation) materials

• Lead impregnated materials (lead aprons)

• Thyroid shields (especially worn during fluoroscopic exams)

• Walls of the exam room are thick with lead

• Lead curtains on fluoro equipment

What is YOUR responsibility as an radiographer?

• protection of the patient, others, and themselves

• ALARA

• Radiation dose is appropriate for procedure

• Avoid unnecessary exposures

• Produce quality images the FIRST time

Cardinal principles: radiographer, patient, other healthcare workers

• Time

• Distance

• Shielding

• Field of X-ray exposure- affects amount of tissue radiated

• Primary Exposure factors

• Unnecessary/duplication of exams

• Pregnancy screening

• Create a checklist that works for you

Time

Refers to length of exposure and # of times patient is exposed

Distance

Distance between oneself and the source of radiation

• Distance = less radiation

Field of X-ray exposure- affects amount of tissue radiated

Controlled by Beam restriction/collimation

• limits radiation dose and exposure

Primary Exposure factors

kVp and mAs (mAxS)

• Controls penetration and # of photons

• Factors selected based on anatomy, patient age, pathology, etc

JRCERT requirements addressing student radiation safety

• Dosimeters must be worn when in clinical

• Policy for threshold dose (RAD handbook)

• Policy for declared pregnant student (RAD handbook)

• Appropriate use of energized lab (RAD handbook)

• Student safety practices

  • Do not hold image receptors

  • Do not hold patients

  • Radiographer lead shielding