Rad Bio - Radiation (Unit 1-1)

Define Radiation:

Transfer of energy from one location to another.

What do x-rays produce when passing through normal matter?

Ionizing Radiation

What are the Consequences of Ionization in Human Cells? (6)

• Creation of unstable atoms

• Production of free electrons

• Production of low-energy x-ray photons

• Creation of highly reactive free molecules capable of producing substances poisonous to the cell

• Creation of new biologic molecules detrimental to the living cell

• Injury to the cell that may manifest itself as abnormal function or loss of function

What are the Goals of Radiation Protection?

Measures employed to safeguard patients, personnel, and general public from unnecessary exposure to ionizing radiation, that may affect organs or the whole body.

What are the three radiation quantities?

• Exposure (Air Kerma)

• Absorbed Dose

• Effective Dose

Exposure (Air Kerma)

Energy transferred from x-ray photons as they expend energy to electrons during ionization. (J/kg)

• Gray (Gy_a) - “grays in air”

Absorbed Dose

Amount of x-ray energy that is absorbed in a material per unit mass of the material.

• Gray (Gy_t) - “grays in tissue”

Effective Dose

Product of the average absorbed dose, the type of radiation delivered, and the radiosensitivity of the exposed tissue.

• Sievert (Sv)

0.007 Sv is equal to how many mSv?

7 mSv

Diagnostic Efficacy

Degree to which the diagnostic study accurately reveals the presence or absence of disease in patient, while adhering to radiation safety guidelines; basis for determining whether an imaging procedure or practice is justified.

The basis for determining whether an imaging procedure/practice is justified takes into account 1) is the ordered procedure ____?, 2) did the patient receive ____?, 3) were ____ produced? and 4) were there any repeat exams due to ____?

• Justified

• Minimal Exposure

• Optimal Images

• Technical Error or Carelessness

ALARA

Keep radiation exposure “as low as reasonably achievable”.

3 Basic Principles of Radation Protection

• Time

• Distance

• Shielding

Radiation-induced cancer does not appear to have a ____, therefore maintaining ALARA should always be practiced.

Fixed Threshold Dose

What is the natural background radiation of a chest x-ray?

10 days

Which of the following quantities of radiation is measured in Sieverts?

Effective Dose

5 mSv is equal to how many Sv?

0.005 Sv

What is Natural Radiation?

Radiation that is always present in the environment.

What is Human-made Radiation?

Artificially created by humans for specific purposes.

Types of Ionizing Radiation

• X-rays

• Gamma rays

• High UV light

Ionizing radiation has _______ energy, _______ frequency, and ________ wavelength.

• Higher

• Higher

• Shorter

Types of Non-Ionizing Radiation

• Visible light

• Microwaves

• Radio waves

Nonionizing radiation has ________ energy, ________ frequency, and ________ wavelength.

• Lower

• Lower

• Longer

Equivalent Dose

Takes into account the type of radiation that was absorbed and provides an overall dose value that includes the different degrees of tissue interaction that could be caused by the different types of ionizing radiation.

Equivalent Dose/EqD is measured in ___.

mSv

Absorbed Dose is measured in _____.

mGy

Effective dose is measured in ____.

mSv

Effective Dose (EfD)

Absorbed dose to a human, given the type of radiation and organs/part of body irradiated. Best overall measure of the biological effect of ionizing radiation or general harm in humans.

The effective dose to the extremities is _________ than dose to internal organs.

Less Dangerous

Ionizing radiation primarily causes biologic damage by _____ from the atoms composing the tissues of the human body.

Ejecting electrons

Cellular damage can lead to _________ or __________.

Abnormal cell function or even complete loss of cell function.

0.25 Sv Biologic Effects

Blood changes

• Measurable hematologic depression, substantial decreases within a few days in the number of lymphocytes or white blood cells that are the body’s primary defense against disease.

1.5 Sv Biologic Effects

Nausea, diarrhea

2.0 Sv Biologic Effects

Erythema

2.5 Sv Biologic Effects

If dose is to gonads, temporary sterility.

3.0 Sv Biologic Effects

50% chance of death; lethal dose for 50% of population over 30 days.

6.0 Sv Biologic Effects

Death

The point at which biologic effects occur is termed the ____.

Threshold Dose

______% of the man-made radiation exposure in the United States.

79%

Medical radiation exposure now contributes ____% of the public’s exposure to ionizing radiation.

50%

3 Examples of Nuclear Accidents

• Three Mile Island, PA 1979

• Chernobyl 1986

• Fukishima, Japan 2011

Medical radiation accounts for approximately ______ of the average annual individual EfD of ionizing radiation.

2.3 mSv

Which diagnostic exam has the highest entrance skin dose and what is it?

CT Head. 40.0 mGy_t

Which diagnostic exam has the highest bone marrow dose, and what is it?

Lumbar Spine. 0.60 mGy_t

Which diagnostic exam has the highest gonadal dose and what is it?

CT Pelvis. 20.0 mGy_t

Which exams are more likely to result in a fetal dose in pregnant patients?

May occur when imaging areas close to the lower spine, abdomen, pelvis, and hip.

• Chest, head, and extremities do not typically result in any fetal dose.

Which one of the below imaging exams has the highest radiation dose to bone marrow?

• CT Pelvis

• CT Head

• Pelvis XR

• Lumbar Spine XR

Lumbar Spine XR

Which of the following options include natural sources of ionizing radiation?

• Medical x-radiation and cosmic radiation

• Terrestrial elements and the human body

• Solar radiation and medical x-radiation

• Nuclear accidents and nuclear energy plants

Terrestrial elements and the human body.

An equivalent dose as low as 250 mSv delivered to the whole body may cause which of the following within a few days?

• An increase in the number of lymphocytes in the circulating blood.

• A substantial decrease within a few days in the number of lymphocytes or white blood cells that are the body’s primary defense against disease.

• A drop immediately to zero in the lymphocyte count.

• A large increase in the number of platelets.

A substantial decrease within a few days in the number of lymphocytes or white blood cells that are the body’s primary defense against disease.

Peak Kilovoltage (kVp)

Highest energy level of photons in the x-ray beam, equal to the highest voltage established across the x-ray tube.

• Quality and Quantitiy

Milliampere-Seconds (mAs)

Product of electron tube current and the amount of time in seconds that the x-ray tube is activated.

• Quantity

If x-ray enter the patient, they may be: (3)

• Absorbed

• Scattered

• Pass though without interaction

Primary Radiation

Emerges from the x-ray tube target and consists of x-ray photons of various energies.

___ is the energy of specific x-rays. ___ is the energy of the most energetic photon.

• keV

• kVp

With 100 kVp, the most energetic x-ray photon can have no more than ____ keV, with an average energy of ___ keV.

• 100

• 33

Primary photons minus exit photons =

Attenuation

Absorbed X-Rays

Interact with patient and give up all energy and cease to exist. (4)

Scattered X-Rays

Interact with patient, surrender some energy, continue to exist but scatter. (2/3)

Attenuated X-Rays

Photons have undergone either absorption or scatter and did not strike the IR. (3/4)

Transmitted X-Rays

Did not interact with the patient or else interacted through scatter but still struck IR. (1/2)

Direct Transmission X-Rays

Photons pass through without interacting with patient and strike IR. (1)

Indirect Transmission X-Rays

Interacted with patient, scattered and then happened to strike IR. (2)

Primary Photons

Photons that emerge from the x-ray tube. (1,2,3,4)

Exit Photons

Image-forming photons pass through patient and reach IR. (1/2)

Attenuated Photons

Photons interacted with patient and then scatter or absorbed in such a way that they do not reach the IR. (3/4)

Which number illustrates x-rays that are absorbed?

4

Which number illustrates x-rays that are scattered?

2 and 3

Which number illustrates x-rays that are attenuated?

3 and 4

Which number illustrates x-rays that are transmitted?

1 and 2

Which number illustrates x-rays that are indirectly transmitted?

2

Which number illustrates x-rays that are directly transmitted?

1

Which two interactions are the most important in x-ray imaging?

Compton and Photoelectric

Photoelectric Absorption

An x-ray photon interacts with an inner-shell electron.

• Incident photon ejects the electron from its inner shell and is totally absorbed in the interaction.

• K or L shells

A photoelectric interaction is more likely to occur with an electron that is ____________________ in its orbit.

More tightly bound

Probability of a photoelectric interaction increases dramatically as the atomic number ____________.

Increases

Compton Scattering

Occurs when an incident x-ray photon interacts with a loosely bound outer-shell electron, removes the electron from its shell, and then proceeds ina different direction as a scatter photon.

Blurring of the image due to too much scatter is called ____.

Radiographic Fog

What directions can Compton scatter go?

In all directions.

• Backscatter

• Side scatter

• Small-angle scatter

What is the primary cause of occupation radiation exposure to the radiographer?

Scatter radiation

Compton scatter is ___ common and ___ desirable, while photoelectric absorption provides ____.

• Most

• Least

• Diagnostic information

When figuring the amount of x-rays attenuated by the patient, the # of exit photons should be __________ the # of primary photons.

Subtracted from

Which of the following types of x-ray photons surrender some energy when initially interacting with the patient, but continue to exist?

Scattered photons

Which types of x-ray photons actually strike the IR during a patient's x-ray exam? (select all that apply)

• Attenuated

• Exit

• Direct transmission

• Indirect transmission

• Exit

• Direct transmission

• Indirect transmission

When were x-rays discovered?

November 8, 1895

Somatic Damage

Damage to the individual organism’s cells during their lifetime.

Genetic Damage

Hereditary effects or damage to the offspring’s cells.

Clarence Madison Dally

Assistant to Edison. First American to die of radiation induced cancer in 1904.

Elizabeth Fleischman

Medical radiographer for US Army during Spanish-American war. 1st women to die of radiation induced cancer.

Radiodermatits

Starts with reddening or erythema of skin; may lead to lesions, cancer due to continued exposure.

Aplastic Anemia

Failure to make new blood cells.

Leukemia

Abnormal overproduction of white blood cells.

Early Tissue Reactions (NBIRFSFH)

• Nausea

• Blood Disorders

• Intestinal Disorders

• Diffuse Reddening of Skin

• Fatigue

• Shedding of Skin

• Fever

• Hair Loss

Late Tissue Reactions (CPOFFS)

• Cataract

• Parenchymal Cell Loss

• Organ Atrophy

• Fibrosis

• Fertility Reduced

• Sterility

Stochastic Effects

• Cancer

• Genetic/Hereditary Effects in Offspring’s Cells

Radiosensitivity

Consequences from radiation exposure to the health of a human as a whole depended on the radiosensitivity of the irradiated part.

____ measures energy transferred from x-ray photons as they expend energy to electrons during ionization. It is measured in ____.

• Air Kerma

• J/kg

Dose Area Product (DAP)

Total of air kerma over the exposed area of patient, expressed in milligray per cubic centimeter (mGy x cm²).

The SI unit for air kerma is ____.

Gy_a

The traditional unit for air kerma is ___.

Roentgen (R) or air ionization

1 J/kg = ____ Gy

1