Chapter 9 Intro to Radiologic & Imaging Sciences & Patient Care

_____________ _____________ is energy capable of penetrating matter and possesses sufficient energy to eject orbital electrons along its path

ionizing radiation

The two basic sources of ionizing radiation exposure are ______________ radiation and ____________________ radiation sources.

natural and human-made

The _____________ must outweigh the risks of any diagnostic study using ionizing radiation.

benefits

Human-made ionizing radiation is also known as

x-rays

a form of electromagnetic radiation that travels at the speed of light

x-rays

sources of human-made radiation include

nuclear industry, radionuclides, medical and dental exposures, and some consumer products

The largest portion of human-made radiation exposure comes from

medical and dental x-ray examinations

Conditions necessary for x-ray production

1. a source of electrons 2. a means to rapidly accelerate the electrons 3. something to rapidly stop this movement

What is an x-ray tube composed of?

A cathode - (negative terminal) and an anode + (positive terminal), enclosed in a special heat resistant glass envelope to maintain the vacuum necessary for optimal x-ray production.

The filament in the ______________ assembly is composed of thoriated tungsten, which provides the source of electrons

cathode

When milliamperage (electric current) is applied to the filament, it responds by boiling off electrons this is known as

thermionic emission

Once kilovoltage (high voltage) is applied to the tube terminals, the electrons resulting from thermionic emission instantaneously accelerate toward the ___________ end of the tube, x-rays are produced when the electrons strike the __________, undergoing an energy conversion that produces both x-rays and heat.

anode

The resultant x-ray beam is heterogeneous - that is, it has many energies measured in _________ ___________

kiloelectron volts (keV)

x-ray beam leaving the x-ray tube toward the patient is known as _______________ or ________________ ______________

primary or useful beam

Once x-rays strike matter, three possibilities exists:

1. they can be absorbed 2. they can transfer some energy and then scatter (no loss of energy) 3. they can pass through unaffected (undergo scattering and secondary interactions with some loss of energy)

x-ray interact with matter in five ways

1. classic coherent scattering 2. photoelectric interaction 3. compton scattering 4. pair production 5. photodisintegration

These two x-ray interactions are particularly important in diagnostic radiography

photoelectric interaction and compton scattering

x-rays that posses energy levels below 10 keV

classic coherent scattering

_____________ ____________ _______________ occurs when an incoming x-ray photon strikes an atom and is absorbed, causing the atom to become excited. The atom then released the excess energy in the from of another x-ray photon possessing the same energy as the original photon, but proceeding in a different direction.

classic coherent scattering

x-rays that result in no energy transfer to the patient or matter and no ionization occurs

classic coherent scattering

The ________________ ____________ occurs when an incoming x-ray photon strikes an inner shell electron and ejects it from its orbit around the nucleus of the atom, creating an ion pair. The atom, having lost an electron, is positively charged and the released electron, continues to travel until it combines with other matter. All the energy from the photon is completely consumed in this interaction

photoelectric effect

the last interaction common to the diagnostic x-ray range is the

compton effect

The _____________ _______________ occurs when an incoming x-ray photon strikes a target atom and uses a portion of its energy to eject an outer shell electron. The remainder of the photon's energy proceeds in a direction different from that of the incoming photon. This process results in a compton or recoil electron ejected from the other shell, which travels until it combines with matter and a photon of less energy.

compton effect

It is responsible for a majority of occupational worker exposure to radiation

compton effect

It constitutes the greatest hazard to patients in diagnostic radiography

photoelectric interaction

Requires very-high energy photons. Incoming photon must have at least 1.02 MeV of energy. Interacts with nuclear force field around nucleus and disappears. Two particles reappear, each with equal energy (0.51 mEv). The positron collides with a free electron and created an annihilation reaction. This creates two photons at opposites angles to each other.

Pair production

Requires photon energies that are extremely high. Incoming photon interacts with nucleus of atom, creating nuclear instability. Nuclear fragment is given off as nucleus seeks stability.

Photodisintegration

____________ has no role in medical imaging and is common interaction in the nuclear industry

photodisentegration

System of units based on metric measurement developed in 1948 and having units used to measure radiation

International System (SI) of Units

The measure of ionization in air as a result of exposure to x-rays or gamma rays.

Roentgen (R)

Being phased out as a unit of exposure since exposure may be expressed directly as coulombs per kilogram

Roentgen (R)

Measures the amount of energy absorbed in any medium, defined as 100 ergs of energy absorbed in 1 g of absorbing material; was expressed as rad but now has been replaced by gray

Radiation absorbed dose (Gy)

What is the SI unit of 2.08 x 10^9 ion pairs/cc

Coulomb/kilogram

What is the traditional unit of 2.08 x 10^9 ion pairs/cc

Roentgen (R)

What is the SI unit of 100 ergs/g

Gray (Gy)

What is the traditional unit of 100 ergs/ g

Rad

What is the SI unit of Rad x quality factor

sievert (Sv)

What is the traditional unit of rad x quality factor

Rem

What is the SI unit of 3.7 x10^10 drps

becquerel (Bq)

what is the traditional unit of 3.7 x 10^10 drps

curie (Ci)

Measured as rem. Unit of dose equivalence. Accounts for different types of radiation and their biologic effects. Rem has been replaced with seivert (sv) expressed as the product of the absorbed dose in rad and a radiation quality factor

Radiation Equivalent Man (Sv)

Used to measure energy transferred from radiation to material

Air Kerma

What does kerma stand for?

kinetic energy released in matter

the total kinetic energy released in a unit mass (kilogram) of air and is measured in joules per kilogram (j/kg)

air kerma

Measures the activity of a radioactive material (radionuclide)

Curie (Ci)

This is unit of measurement is used in nuclear medicine and radiation therapy

Curie (Ci)

SI unit of activity is the

Becquerel (Bq)

What does ALARA stand for?

As Low As Reasonably Achievable

Annual whole body effective dose limit for occupational worker is

50 mSv (5rem)

Maximum cumulative whole body dose limit is

10 mSv x age

Whole body dose equivalent limit is _______ for the general population, which represents 1/10 the occupational worker's limit

5mSv (0.5rem)

Cells have two major parts

Nucleus and Cytoplasm

genetic material of cell contained in

nucleus

_________ of cell content is water

80%

Two classes of human cells

somatic and genetic

two theories of cellular irradiation damage exist

direct-hit theory and indirect-hit theory

___________ cells perform all of the body's functions. They possess two of every gene on two different chromosomes.

somatic

__________ cells are reproductive cells of an organism

germ

proposes that any type of radiation transfers its energy directly to the key molecule it has struck, resulting in the formation of ion pairs or elevation to an increased, excited energy state.

direct hit theory

proposes that key molecules are affected by radiation depositing its energy elsewhere in the cell. Because cells are 80% water, indirect action occurs when water molecules are ionized.

indirect hit theory

during this interaction, it produces chemical changes within the cell that alter the internal environment, injuring the cell, which can result in eventual cell death. with x-radiation and gamma radiation, the vast majority of cellular damage is the result of

indirect hits

cellular _____________ is principally a result of the rate and duration of cellular mitosis

radiosensitivity

cells have different degrees of

radiosensitivity

to study the cell's response to radiation, a method of classification according to sensitivity was developed by

Bergonie and Tribondeau in 1906

Bergonie and Tribondeau determined what?

that mitotic activity and specific characteristics of each cell affected how the cell exhibited cell damage.

Cells are most sensitive to radiation during ________ ________, when they are primitive in structure and function.

active division

The theory by bergonie and tribondeau stated that Examples of radiosensitive cells

the basal cells of skin, crypt cells of the small intestine, and germ cells

The theory by bergonie and tribondeau stated that Cells resistant to radiation, being more specialize in structure and function, do not undergo repeated mitosis. These cells include

nerve, muscle, and brain cells

What are results of radiation to a cell?

Cellular death, delayed mitosis, altered mitotic rate

T/F most cells try to repair the damaged sustained through absorption of ionizing radiation.

True

The possibility of a cell repairing itself depends on

how sensitive the cell is to radiation, the type of damage sustained, the kind of radiation, the exposure rate, and the total dose given.

The total body response of any organism to radiation depends on the effect on all the systems of the body. Because every system is different in its sensitivity or resistance, the total body response at a particular dose is defined by the system most affected. This response is known as

acute radiation syndrome

__________ _________ _________, occurs only when the organism is exposed fully (total body) to an external source of radiation given in a few minutes. Only then does the organism develop the full set of signs and symptoms that define each syndrome, which depends on the dose received.

acute radiation syndrome

Three general stages of response exists for each acute radiation syndrome. They are:

prodromal stage, latent period, and manifest stage

commonly referred to as the nausea, vomiting, and diarrhea stage

prodromal stage

stage in which the organism feels well; however, during this time, the body is undergoing biologic changes that will lead to the final period

latent period

stage in which the organism feels the full effects of the exposure, leading to either recovery or death

manifest stage

The three radiation syndromes are

1. bone marrow syndrome 2. gastrointestinal (GI) syndrome 3. central nervous system (CNS) syndrome

occurs at doses of 2 to 10 Gy (200 to 1000 rad). Total body exposure results in infection, hemorrhage, and anemia

bone marrow syndrome

results from doses of 10 to 50 Gy (1000 to 5000 rad) Individuals experience massive diarrhea, nausea, vomiting, and fever when subjected to those doses

gastrointestinal (GI) syndrome

occurs at doses above 50 Gy (5000 rad) with the individual experiencing seizures, coma, and eventual death from increased intracranial pressure.

central nervous system (CNS) syndrome

Doses received from radiation syndromes are far _________ than those received by occupational worker or by a patient

greater

late effects of radiation exposure are divided into two groups:

somatic effects and genetic effects

develop in the individual exposed

somatic effects

occur in future generations as a result of damage to the germ cells

genetic effects

The two most frequently induced somatic effects are ______________ and ____________

cataractogenesis and carcinogenesis

The most important late somatic effect is _________ __________

cancer development

The cardinal rules of protection

Time, distance, shielding

When a radiographer minimizes the length of time a patient remains in the path of the x-ray beam, he/she is applying one of the primary rules of ____________.

protection

Another way to lessen the patient does is to maximize the _________ between the radiation source and the patient

distance

The increased __________ lessens the entrance or skin dose to the patient.

distance

The last rule of protection is to __________ by placing some material over the reproductive organs of the patient whenever they are within 4 to 5 cm of the primary beam.

shield

gonadal shielding should be used for all patients of reproductive age, unless

it interferes with the anatomy of interest

Shields are made of lead, which has an atomic number of

82

Lead absorbs x-rays through the process of

photoelectric effect

The three basic types of shields are

1. flat contact shields 2. shaped contact shields 3. shadow shields

are made of a combination of vinyl and lead, and are placed directly over the gonads of the patient. They are made in various sizes to accommodate the age of the patient

flat contact shields

are cup-shaped and designed specifically to protect the gonads of male patients. Because of their shape, they can remain in shape securely, even when the patient must turn to accommodate examination.

shaped contact shields

are mounted to the side of the collimator of the x-ray tube on a flexible extension arm. they can be manipulated to extend into the path of the beam and cast a shadow on the patient, indicating the area protected

shadow shields

____________ is the best, and most effective method of protection for the radiographer

distance

Any occupational worker who is regularly exposed to ionizing radiation mus be __________ to determine estimated exposure

monitored

T/F any worker who is likely to receive more than 1/10 of the recommended dose-equivalent limit should be monitored

true

________ ___________ devices measure the presence and rate of exposure in real time

field survey

Three popular monitoring technologies

1. pocket dosimeter 2. optically stimulated luminescence dosimeter (OSL) 3. thermoluminescent dosimeter (TLD)

_____________ _________ _________ __________ is the most common method used to monitor personal exposure.

optically stimulated luminescence dosimeter (OSL)

Monitors measure the quantity of ___________ received on the basis of condition in which the radiographer was placed

radiation

personal monitoring dosimeters must be worn

at collar level, outside of lead apron, device should be face forward, pregnant radiographers may have a second device worn at waist level and under lead apron

____________ _________ are those that can be struck by the primary beam exiting the x-ray tube.

primary barrier

_______ ________ are those that can be struck by secondary, scatter, or leakage radiation.

secondary barrier

During Fluoroscopy procedures, one must wear a lead apron with ________ _______ of lead equivalency

0.5 mm

The minimum permissible lead equivalency for a lead apron is ______ _____. Usually lead gloves posses this amount.

0.25 mm

OSL dosimeters consists of a strip of _____________ _____________, a copper filter, an open window, a tin filter, and an imaging filter.

aluminum oxide

_________ _______ provides an immediate reading of occupational dose.

pocket dosimeter

A common instrument used to detect x-radiation, gamma radiation, and beta radiation is the ________-_________ counter, which is an ionization chamber constructed of an electrode housed within a chamber.

Geiger-Muller

What is the equivalent dose annual limit for lens of eyes?

150 mSv / 15 rem

What is the equivalent dose annual limit for extremities (hands, skin, feet)?

500 mSv / 50 rem

What is the dose limit for a declared pregnant woman for the duration of her pregnancy?

50 mRem / 0.05 rem / 0.5 mSv

What is the fetal dose threshold?

5 rad

What is the monthly dose limit for a pregnant student?

0.005 rem / 0.05 mSv per month