rad Tech Unit 1

Ionizing radiation

Carries a benefit and a risk, benefit being information found out and risk being harming the patient. Ionizing radiation can hurt the patient or tech using it.

Particulate Radiation

Includes high energy electrons, neutrons, and protons that produce ionization in matter by direct atomic collisins. Two radioactive decays that go along is Alpha and Beta Decay.

Alpha particle

Contains two protons and two neutrons, as a result equivalent to helium nuclues. Emitted from the nuclei of very heavy elements as they undergo radioactive decay. Have postive charge and great mass. Alpha particles travel about 5cm. From external sources these are harmless

Beta particles

Identical to electrons with the exception of their origin. Emitted from nuclei or radioactive material. Negatively charged and light. Travel much further than alpha particles 10-100cm.

Electromagnetic Radiation

Includes X-rays and gamma rays, which produce ionization in matter by other types of interactions. X-rays and gamma rays are essentially the same with exception of origin.(less than 200keV)

Gamma rays

Emitted by the nuclei if radioactive materials.

X-rays

Human made in an X-ray tube

Transfer of energy from photon to matter

Results in ionization

Photoelectric absorption

Photon interacts with atom, causing electron to be set in motion→ results in kinetic energy being released in the material

Compton Scattering

Absorption of released kinetic energy via excitation and ionization. These occur along the tracks of charged patrickes set in motion increase biological damage in a tissue. One results biological damge due to charged patrucle set in motion and direct interaction. Other absorption of tadiatuon occurs in water mooecules producing high reactive species such as free radicals.

For X-rays and gamma rays

Approximately two thirds of biological effects on tissue are the result of indirect actions

Biological effects

ill health, nonspecific life shortening, developmental abnormalities, a d degenerative diseases. The effects from exposure to ionizing radion may be classified as somatic or genetic.

Somatic effects

May. Become wvident in the irradiated individual. Such effects are not usually expected to work In individuals exposed in the course of their work in the medical envoirment. Effects include Skin erythema, cataracts, and radiation induced malignancies.

Genetic effects

Dont produce any significant obvservable effect in exposed individuals. But may appear in descentdants of exposed individual. They may not manifest in the children of the exposed individual. They may lie dormant for several generations and eventually may be eliminated completely from the genetic pool. Example radiation induced mutatuons.

The first radiation exposure recorded death

Was in 1904 when they finally started taking the risk seriously.

The international commision on radiological personnel.

Created in 1928 and in 1929 the advisory committee on X-Ray and Radium protection and evolved into the national council on radiation protection and measurements (NCRP) in the us.

British X-ray and Radium protection commitee

Created in 1921, researched reducing radiation exposrue to patients and medical personnel.

ALARA

goal of radiation protection. As Low As Reasonably Achievable.

Roentgen

Used for specfying exposure

rad (radiation absorbed dose)

Used for specifying energy absorbed

rem(radiation equivalent in man)

Used for specifiying biologically equivallent dose.

Kerma

Kinetic energy released per unit mass

Air kerma

Kinetic energy released per unit mass of air.

Integral dose

Used to describe the total radiation energy imparted to matter

Effective dose

Used to measure the radiation and organ system specific used to measure the radiation and organ system specific damage in man.

Activity

Used to measure the amount of a radioactive material as it undergoes decay

Dose equivalent

Is based on the absorbed does at a point.

Equivalent dose

Based on the average absorbed dose in the tissue or organ

Sievert

Rem has been replaced by sievert in SI system.

Gieger-Mueller survey Instruments

Gieger mueller survey instruments or counters are primarly used to detect the presence of radiation. Rather than provide the exact measurements. A GM counter is a gas filled detector. Consists of a volume of gas between two electrodes. GM counters effective at measuring charged particles. Such as beta particles. Useless for x and gamma. Most commonly used in nuclear medicine. As radioactive contamination survey instruments.

Scintillation Detection Devices

Combine the use of a scintillator with a devicr that can convert light to an electic signal. Scintillators are materials that emit visible or ultraviolet light. When exposed to ionizing radiation. This light is converted to an electric signal and is measured. The most common applications for scintillation detectors are in gamma cameras in nuclear medicine.

Ionization Chamber Instruments

Commonly employed for the measurement if the primary and secondary radiation beam for purposes of evaluation and equipment performance, environmental exposure assessment if scatter and leakage radiation and for measurement of patient exposure. Designed to measure specific ranges of radiation intensity.

Optically stimulated Luminescence (OSL) dosimeter. Badge

Most common type of radiation monitoring device. Radiation that passes through thin strip of aluminum oxide. A laser light is used to stimupate the aluminum whoch becomes luminescent in proportion to the amount of radiation exposure it has recieved. Can report as low as 1mrem can reanalyze, great long term and envoirnmental stability.

Film badge dosimeter

Monthly basis and cosists of two pieces having different sensitivities to xrays and contained within a light, tight envelope. When badge is exposed to ionizaing radiation film emulsion darkens in proportion to the degree of radiation exposure recieved. Commonly used to measure total body exposure of the individual reading less then 10 mrem.

Thermoluminescent Dosimeter (TLD) (RING)

Personnel monitoring devices using thermoluminscence dosmiters containing small chips of material usually (Lithium floride). When exposed to radiation, a portion of the absorbed energy is stored in the crystal structure of the LiF chips in metastavle states. This absorbed energy remains as visible light. Measures exposure to extremities in form of ring badges

Pocket dosimeter

Electonic personal dosimeters, can be read from electric display and similar system of ionization of air in small chamber.

NRC (U.S Nuclear Regulatory commision)

Has been given the regulatory authority for special nuclear materials and by-products in a number of instances, the NRC has entered into agreements woth the states to oversee and enforce the regulations.

The primary purpose of establishing dose effects

To limit the risks of stochastic effects and to prevent deterministic effects.

Stochastic effects

No threshold dose of radiation exists, such as cancer and genetic effects. Random in nature, regardless of dose. Higher the dose higher the chance if effects such as cataracts, skin erythema and sterility. Dose has to be high ti reach the effect. Once does is high, effect rate if super high.

Radiation workers

An occupational risk, a certain likelihood of exposure to ionizing radiation in the course of their normal duties.

Occupationally exposed workers

Individuals who have highrr potential of exposure to radiation in course of employment.

Occasionally exposed workers

Individuals whose duties may occasionally bribg them into areas where radiation exposure may occur.

Effective dose limit for radiation workers

5rem/ 50msv per year

Dose limit equation/cummalitive effective dose

E=10 mSv X N

E=10 mSv X 19

E= 190mSv (19rem)

Dose limit for 19 year old radiation worker

Principles of personnel exposure radiation

1) reduce the amount of time spent in the vicinity if the radiation source while it is operating. (Time)

2) increase the distance between the radiation source and the individual to be protected(distance)

3) interpose a shielding materila, which will attenuate the radiation from the source.(shielding)

Time (radiographic procedures)

X-ray imaging equipment produces radiation only during the actual exposure used to form the image during a procedure. The time of exposure on a per-inage basis is very short. (Typically less then 1 second)

Time (fluroscopy)

Fluros are used when dynamic info is required the x-ray source may be on for several minutes to as long as an hour. To minimize exposure to radiation individuals should reduce amount of time they spend in the vicinity of an operable radiation source.

Distance

Increasing the distance between the individual and the source of radiation is an effective method to reduce exposure to radiation. As distancr from the source of radiation is increased the radiation level will decrease fast.

Shielding

Used when neither time or distance is effective in achieving the desired degree of reduction in exposure. Common materials are lead aprons, gloves etc. other materials are concrete.

Structural protective barrier

Made of materuals having effective x-ray attenuating properties, and the thicknesses sufficient to reduce exposres to the desired levels. Commonly used materials: lead sheet, concrete, lead glass, steel, and leaded acrylic.

Primary or secondary barriers

Primary barrier

Struck by the primary or useful bean exiting the x-ray tube. Thick

Secondary barriers

can only be struck by scattered and leakage radiation. Thin

Protective devices

Worn by all personnel, such as lead apron lead gloves, leaded glasses, and thyroid shields.

Bean limitation

Size of the x-ray veam should always be restricted to the area of clinical i terest and should never exceed the suze of the image receptor. Proper collimation not only reduces patient dose but also improves the overall wuality of the radiographic image.

Technique selection

Factors for a given examination should be selected to minimize doasge to the patient. High kVp/low mAs techniques preferred to decrease patient dose. However the selected kVp should be chosen so that the reauired contast in the radiographic image is not compromised as a result of a more penetrating xray beam. SID 40

Filters are placed at the x-ray

to selectively absorb low energy photons that would be absorbed by the patient normally and not contibute to image. If non existence occured this would increase a higher patient dose. Alluminum is the most common filtering material used and filtration is expressed in terms of the thickness of alllunminum. Filtration decreases patient exposure.

Radiographic grids

Placed between patient and the image receptor to absorb scatter radiation. Grids absorb primary and scatter radiation technical factors must be increased to produce an image of acceptable exposure. Higher technical factors increase patient dose but it increases image quality.

Gonadal shielding

Minimizes possibility of any genetic effect on the future children of an exposed individual. Special attention should be paid to shielding the gonads of chilsren and adults of childbearing age.

Flat contact shields

Made if various sizes of lead impregnated vinyl, placed between gonads and source of radiation.

Shaped contact shield

Cup like shape and designed to enclose full male genatalia these shields ensure maximum patient protection in these areas.

Shadow shields

Mounted to the tube and are placed in x-ray beam near the collimator. The collimatord light field must be precise for accurate shield placement. The device adjusted to cast a shadow over the patients gonads.

Image receptors (IR)

Speed of IR should be as high as possibke, consistent with the required information of the radiologic procedure. Key to image is the receptor.

Projection

The projection used for a particular examination should will have an impact on patient dose to speciric body tissues for example the lens of the eye recieves a greater dose during AP projections of cranium than it does if the PA projection is used.

Repeat images

Every time a repeat image is needed it highly increases patient dose. Should be very careful retaking and communicating between patient and the personnel taking the image.

Pregnancy radiation exposure

A situatuon deserving special consideration is the possibility of radiation exposure during the early weeks of pregnancy embryo must not exceed 50mrem or .05 rem

Declaring pregnancy

Pregnant radiation workers are referred to in U.S federal regulations as “declared pregnant” because a women has the right to declare or not declare pregnancy.

Special case on a pregnant women

If a radiographic exam on a pregnant patient is deemed necessary. A diagnostic radiological physicist should perform calculations to estimate the actual fetal dose.

Background radiation

Sources occur spontaneously in nature and are not affected by human activity. These forms include cosmic radiation from the sun and other planetary sources like uranium and radium.

Artificial radiation

Nuclear industry, radionuclides, medical and dental exposures and some consumer products. The nuclear industry has contributed fallout from abovegrounds weapon tests. Accidents in nuclear fields (chernoybl)

For X-rays to be produced

1) source of electrons

2) a means to rapidly accelerate the electrons and 3) something to rapidly stop this movement

Classic coherent scattering

X ray that possess energy levels below 10 keV cna interact with matter through classi coherent. Scattering occurs when an incoming x ray photon stimes an atom and is absorbed. Causin atome to become excited, atom then releases excess energy in form of another xray. Classic coherent scattering results in no energy transfer to the patient.

Physics

Studies matter and energy

Energy

Ability to do work

Law of conservation of energy

Law of conservation of energy

Energy can not be created or destroyed, can only be transformed.

Matter

Material of which everything is made

3 states of matter liquid, gas, and solid

Law of conservation of matter

Matter can not be created nor destroyed during physical or chemical change, but can be transformed.

Elements

Simplest form

Atom

Smallest particle or unit

neutral atom

The # of elections = the # of protons

Atomic number or z#

number of protons

Molecules

The chemical union of two or more elements in definite proportions

Ion

Atom with a surplus or deficient number of electrons

Isotope

2 atoms with the same atomic number but different atomic mass

Photon

A bundle of energy

Potential energy

Ability to do work by a position

Kinetic energy

Energy of motion

Electrical energy

Electrons move through an electric potential

Chemical energy

Released because of a chemical reaction

Thermal energy

Energy at the motion at the molecular level

Nuclear energy

Contained in the nucleus of an atom

Electromagnetic energy

Energy that is released or emitted from objects in the form of electrical and magnetic waves that can travel through space.

X rays are part of ____ spectrum

Electromagnetic

They are wavelike fluctuations of eelectric and magnetic fields

Energy emitted and transfered through matter is called

Radiation

Ionizing radiation notes

Any kind of radiation capable of removing an orbital electron to create an ion

Ions

Can cause biological damage

Photoelectric effect

Photon transfers all energy to the atom

Most harmful to patient* Causes contrast crucial to taking the photo in x ray

Notes on compton scattering

Some of its energy is transferred to the atom the rest is scattering. Most harmful to techs. Scatter is bad for techs

Notes on coherent scattering

Does not ionize the atom only interacts

Pair production

High energy photons which interacts with the nucleas (min 1.02MeV of energy needed for this process)

All processes are responsible for

Patient and tech dose,