Radiation Protection

Standardize Dose Reporting

Allows ordering docs to maintain awareness of dose accumulation & make informed decisions dictate doses for rad studies in report

ALARA

As Low As Reasonably Achievable- standard for techs & institutions synonymous with ORP vital in filtering unnecessary studies, informing/prepping pts for the study, using optimal positioning and optimal technique

Stochastic Effects

could occur with any amount of exposure- the probability increase with greater dose

Biological Damage

damage in living tissue

Exposure

defined as: the total electrical charge (+ or -) per unit mass generated in a fixed volume of dry air at 760 mm Hg and 22 degrees

Protons

Positively charged subatomic particles Can be made into a source of radiation by interaction of cosmic rays with the Earth's atmosphere

Absorbed Dose

(D) the amount of energy transferred (per unit mass absorbed by irradiated object) determined by atomic #, density of the object and energy of the photon Absorption increases as atomic # (z) and density increase and as a photon energy decreases- absorbed dose is directly prop to mass density- double density= double absorption The SI unit is Gy unqualified to risk higher energy kv different absorbed dose than lower energy kv (more/less penetrating/ attenuating) 1 Gy= 100 rads

Exposure in the air

*the traditional unit is the Roentgen (2.58x10^-4 C/Kg):* Coulomb= quantity of electrons- 6.24x10^18 measures ionization in rad

EqD & Biological Effects- Whole Body Doses

-0.25 Sv- blood changes (hematologic depression-lower lymphocytes) -1.5 Sv- nausea, diarrhea -2.0 Sv- skin arrhythmia -2.5 Sv- temporary sterility -3.0 Sv- LD 50/30 -6.0 Sv- Death

ALARA Responsibilities

-Facilities must have a written form of an effective radiation safety program -necessary resources & appropriate environment to practice ALARA -Rad workers must be aware of the rules governing a workplace -rad workers must perform duties consistent with ALARA

Sources of Radiation

-manmade or artificial radiation- created by humans for various uses -radioactive consumer products, air travel, nuclear fuel/fallout, nuclear disasters and us(medical radiation) -contribute an additional 65 mrem to the total annual EqD received by a US resident- per 1987 figures -Or contribute around 313 mrem per the total in 2006

Chest Dose

0.1 mGy ESE 0.1 mGy bone marrow <1 gonadal

Expansion of CT/Nuc Med/Fluoro

2009 300 mrem from manmade sources Total Annual EqD: 625 mrem Natural Background radiation hasn't changed *medical imaging contributes to 48% of the total background radiation VS 15% in 1987* doubled radiation affected dose per individual

Abdomen Dose

4.0 mGy ESE 0.3 mGy bone marrow dose 1.25 mGy gonadal

BERT

Background Equivalent Radiation Time Compares radiation dose to natural background radiation USA: 3 mSv/year or 300 millirem

Radiation Dose

Based on the amount of energy transferred to electrons by ionizing radiation

Alpha Particles

Consist of 2 protons & 2 neutrons emitted from the nuclei of certain radioactive elements (positively charged uranium or plutonium) highly energetic but doesn't travel far doesn't penetrate/ absorb

Radiation Protection

Defined as: effective measures employed by radiation workers to safeguard patients, personnel, and the general public from unnecessary exposure to ionizing radiation *The goal is to minimize the possibility of causing damage to healthy biologic tissue*

Early deterministic somatic effects

Happen within minutes, hours, days or weeks of exposure: nausea fatigue diffuse erythema hair loss intestinal disorders fever blood disorders shedding of outer skin

Ionizing Vs Nonionizing

In the EM spectrum, only x-ray, gamma, and high energy uv radiation have enough energy to remove electrons from atoms

Natural Background Radiation

Ionizing radiation from environmental sources

LD 50/30

Lethal Dose: the dose level at which 50% of the population will die within 30 days- whole body dose of 3Sv/ 300 rem

Absorbed Dose

Measures the amount of radiation absorbed by tissue in terms of Energy per unit of tissue Mass SI unit is Gray-an absorption of 1 joule per kg 1 Gray= 100 rads (gray=Gy) Determined by the atomic number, the density of the object and the energy of the photon Absorption increases as atomic number (z) and density increase and photon energy decreases-absorbed dose is directly proportional to mass density double density=double absorption traditional unit is the radiation absorbed dose (rad)

Beta Particles

Negatively charged particles identical to high speed electrons, but they originate in the nucleus (electron w/ high kinetic energy= more penetrating)

Neutrons

Neutral charged subatomic particles Produced by nuclear fission/fusion

Effects of Radiation

Pg 66 box 4-1 genetic effects early deterministic somatic effects late deterministic and stochastic somatic effects

RSO

Radiation Safety Officer Person in hospital setting in charge with -Execution -Enforcement -Maintenance of ALARA policy *in a small hospital it could be a radiologist/physician*

What is our largest risk of natural background radiation?

Radon

Equivalent Dose

Standard of measurement that allows for comparison of dose between different types of radiation SI system: Sv-Sievert = to rem 1 Sievert= 100 rem uses the quality factor (Q) and linear energy transfer (LET) to create a radiation weighting factor (Wr) Absorbed dose is multiplied by Wr to compare the doses of different types of radiation to each other

Patient Dose

can be evaluated and expressed in different terms - entrance skin exposure (ESE) - bone marrow dose - gonadal dose - fetal dose entrance into the body & risk

Air Kerma

The amount of kinetic energy released in a unit mass-joule/kg An SI unit that is replacing the unit exposure expresses radiation intensity in air, and is used in measuring concentration at a point in space *Acronym for kinetic energy released in matter* photon entering and how much kinetic energy is released unit of mass Can also be converted to express tissue Kerma

Risk Vs Benefit

The benefit of exposure through diagnostic imaging must outweigh the potential risk of biological effects The physician determines this, and the patient must be informed to this and agree to it

Diagnostic Efficacy

The degree to which the study accurately reveals the presence/absence of disease- involves minimizing the the exposure/ risks of radiation and maximizing the quality of data produced *minimize risk/ maximize data*

Maximum Permissable Dose

The largest dose that an occupationally exposed person could receive that had little likelihood of causing adverse biological effects

Dose Area Product

The total of the air kerma delivered multiplied by the area of tissue irradiated expressed in mGy-cm^2

Cardinal Rules for Patients & Radiographers

Time Distance Shielding

1987

Total Natural Background: 3 msv Total Medical: 0.53 msv Total Manmade Background: 0.65 msv Total Annual EqD: 3.65 msv

2006

Total Natural Background: 3.11 msv (Thoron included)*hasn't really changes* Total Medical: 3.0 msv *big increase* Total Manmade Background: 3.14 msv *big increase* Total Annual EqD: 6.25 msv *big increase*

Patient Education

Understand why procedure is being performed and what is expected of the patient can put the patient at ease & produce better results *A patient has the right to refuse a procedure* explaining risks/benefits help them make informed decision

Collective Effective Dose (CoLEfD)

Used to study the effects of low doses of radiation received by groups of people Multiplying average EfD by the # of people exposed- the unit is the person-sievert 100ppl exposed to .5 sievert would constitute a CoLEfD of 50 person-sieverts

Total Effective Dose Equivalent (TEDE)

Used to study track the cumulative effective dose to individuals particularly occupation ally exposed ones

Concept of Absorbed Dose

X-rays will either interact with the atoms of the pts body or will pass through Any interaction that results in the transfer of energy from the photon to the pts body is considered absorption Absorbed dose (D): the amount of energy absorbed per unit mass any absorber and how much energy is transferred

Cellular Damage

abnormal cell function or loss of cell function

Late deterministic and stochastic somatic effects

appear within months or years of exposure: cancer genetic effects cataracts fibrosis organ atrophy loss of parenchyma cells reduced fertility sterility

Somatic Damage

biological damage to the body of the exposed induvidual

Effective Dose

equivalent dose modified by the type of tissue being irradiated- different tissues have different absorbing qualities and different sensitivities (Sv/rem) risk of induviduals factors in the difference in sensitivity to the effects of radiation by different tissues equiv dose is multiplied by a tissue weighting factor (Wt) to find effective dose (EfD) EfD makes the possible use of BERT to communicate risk to pt

Terrestrial, cosmic, and internal

examples are radon, gamma rays (high altitude flights) and ingested naturally occurring radioisotopes

Tolerance/ threshold dose

level below which occupationally exposed individuals could be subjected without acute effects-0.2 (200 mrem) Roentgen per day first (1934) then 0.1 Roentgen per day (1936)

Direct Transmission

photons that interact with the subject, but still reach the image receptor (higher kv photons- more penetrating)

Skin Erythma Dose

quantity of radiation that causes diffuse redness in an area of skin

Genetic Damage

radiation damage that will appear in subsequent generations

Occupational Exposure

radiation exposure received by radiation workers in the course of exercising their professional responsibilities

Radiodermatitis

reddening of the skin caused by radiation exposure

Small Angle Scatter

slight bending of a photon's path that still results in the photon reaching its intended destination related to higher kv's

Exit Radiation (remnant beam)

the radiation that emerges from the absorber and strikes the image receptor

Primary Radiation

the radiation that is produced at the target

Attenuation

the reduction in the number of photons in the primary beam by absorption and scatter processes

Absorption

the transference of EM energy to atoms

Radiographic fog

undesirable additional radiographic density not related to actual anatomy

Deterministic Effects

will happen if a certain threshold dose is received- the severity goes up with greater dose