RAD BIOLOGY
Terms
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- What is radiation safety?
-
ALARA
Limit the exposure to ionizing radiation to the smallest amount to the patient an yourself - ALARA
- As Low As Reasonably Achievable
- Basic Concepts of Risk vs. Benefit
-
82 % natural Radiation
11 % man made - Potential threat to the well being of a human
- Risk
- improvement of the quality of life of a human
- Benefit
- Asks individuals or groups their perception of risk
- Perceived risk
- Makes comparisons between 2 or more activities
- Risk comparisons
- Bert
-
Background
Equivalent
Radiation
Time - The Risks- Benefit Continuum
- Basic assumption: there is no threshold (level below which no effects will be seen) consequently, all radiation poses a potential risk of some sort
- 3 basic categories of radiation hazards
-
Somatic effects (to the body)
Genetic effects (future generations)
Fetal effects - Smoking 11.4 cigarettes or driving 28 miles on a highway or equal to the risk of dying on the way to a hospital
- Chest x-ray
- 128 cigarettes or driving 313 miles
- BE
- Diagnostic Radiology may benefit ___ the US population annually
- 1/2
- Diagnostic Radiology may also induce up to
-
3600 extra mutations
712 cases of leukemia
910 total cancers - A lead apron covers approximately ___% of your body’s active bone marow
- 75
- Protects you from radiation-induced leukemia
- Lead Apron
- The professional role of the radiologic technologist 3 common goals:
-
1. To promote efficacy (to do the best job, the 1st time)
2. Provide radiation protection
3. Provide the highest level of patient care - The professional attitude
- Technologists who do not show their professionalism by limiting patient exposure are a burden on the profession
- The public’s first line of defense against excess radiation is ___
- The radiologic technologist
- GSD
-
Genetically significant dose
genetic dose index
currently the US uses the standard of 20 mrads/per year - MMD
-
Mean Marrow Dose
Somatic dose index for leukemia/measure of radiation dose - Public and Patient Attitudes
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Provide patient with accurate information and protection
ESE (entrance skin exposure) -
True of False
Do not use fluoroscopy to locate anatomy prior to an overhead film! - True
- PBL
-
Positive beam requirements
Automatic collimation - The role of motivation
- A technologist whose only motivation to provide radiation safety is based on requirement of laws is practicing an occupation, not a profession
- RT’s must
-
Provide education to the patients
Other health care workers and the general public - Six orientations to learning
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Oblivious (does not want to know or learn)
Uninvolved
Resistant
Previous bad experiences
Focused person
Comprehensive person - Radiologic Technologist as Leader
- Example: Norlin Winkler’s protective curtain
- Are rules of behavior that must be followed (based on ethics)
- Laws
- Call for a higher level of care than law requires
- Ethical standards
- Ethics: to do good
- beneficence
- Ethics: bad
- maleficent
-
True or False
Do not fluoro the patient to determine where to center. - True
- If you use fluoro to determine where to center on a patient it can add up to __ which is higher than a repeat film
- 5 rad/min
- What is a RT code of ethics?
- ASRT code of ethics
- Legal issues and Radiation protection
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1.Pregnancy laws
2.Radiation exposure
3.Equipment laws (both state and federal) - Authorizes civil penalties to technologists and other health care workers who do not report defects and failures in medical devices
- Safe Medical Devices Act, 1991
-
Permission given to qualify a person to perform specific activities
Goal is to protect the public - Licensure
-
Lawsuits and other legal actions
To prove negligence: -
1.It must be shown that a duty on the part of the professional exists
2.If a duty is shown, a breach of duty must be shown
3.The cause must be due to an action on the part of the professional
4.If cause is proven, an injury must be proven - Determined that if permissible dose limits were not exceeded for occupational workers in the industry, no breach of duty occurred
- 1990 ILLINOIS COURT DECISION
- What is the student’s role in radiation protection?
- ALWAYS USE ALARA
-
A form of electromagnetic radiation
Similar to visible light but are shorter in wavelength
Behave as both waves and particles
They have no mass/ no charge - x-radiation
- Physical properties of x-rays
-
1.Ability to pass through matter (extremely penetrating)
2.They are heterogeneous (many different wavelengths), polyenergenic (many different energies
3.Travel in a straight line
X-rays
4.cannot be focused by a lens
5.Electrically neutral
6.Produce secondary and scatter radiation when interacting with matter
7.They are luminescent- cause certain crystals to fluoresce (give off light)
8.Affect photographic film
9.They ionize gases
10.Cause biologic changes - Some x-rays will pass through some will be absorbed
- Differential absorption
- Examples of diagnostic uses:
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Diagnostic radiology
Fluroscopy
Tomography
Mammography
Digital radiography
CT - Other uses of radiation
-
Forensic studies
Authenticate painting (uses grenz rays/low energy)
Crystallography
buildings - X-ray tube components
-
X-ray tube generates x-rays (vacuum diode tube)
3 basic components
evacuated glass envelope
cathode
anode -
1.Prevents radiation leakage
2.Supports the tube
3.Insulates against electric hazards - Lead lined housing
- Pyrex (2 electrodes)
- Glass envelope
-
Negatively charges electrode source of electrons
1.large filament (tungsten wire)
2.Small filament (tungsten wire)
3.Negatively charged focusing cup - cathode
-
Positive most have rotating tubes to help dissipate heat receives the electrons
Target
Stem
Rotor - Anode
- Basic operation of the x-ray tube:
-
Filament of the cathode is heated (mAs)
Generates a stationary cloud of electrons
They are weakly repelled by the negative filament (called a space charge)
Thermionic emission (production of electrons by heat) - X-rays are generated by 2 processes when the high speed electrons are stopped at the target
-
1.Bremsstrahlung (braking radiation)
2.Characteristic radiation (binding energy of the k-shell of tungsten) - Radiation produced in the tube
- Primary radiation
- Radiation passes through the window
- Useful or primary beam radiation
- Mostly inside the tube
- Leakage radiation
- Portions of the primary beam that pass through the patient
- Remnant radiationorExitorImage Forming Radiation
- Interacted with the patient and has changed direction and energy
- Scatter radiation
- From the patient’s body
- Secondary radiation
- Not Commonstart at the highest mA and falls during the exposure allows better use of tube limits(we cannot control mA or mAs)
- Falling Load
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Dynamic imaging or imaging of motion
Low mA ( 1-3 )
High kVp (90 – 120)
TV monitor displays 1-2 line pairs per
millimeter of resolution
Diagnostic film displays 9 line line per mm (lp/mm) - Fluoroscopic Equipment
- Amplifies the brightness of the image
- Image intensifier
- Ratio of the area of the screen (input phosphor) to the output screen square
- Minification gain
- X-ray Beams
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mA Time kVp
Diagnostic 10-120 0.001-10 sec
20-150 kVp
Therapy
below 20 1-60 min 4-40 MV - The target is removed and a scattering foil is added uses MeV monoenergetic electron beam is left used to treat superficial tumors (head and neck)
- Electron beams