Lecture #3 Effects of Radiation on Human Tissue DHY 117

What are 2 methods that cause chemical changes in cells?

ionization, free radical formation

The electrons displaced through the _____ _____ or ______ ____ can react with the cells of the absorbing tissues

Photoelectric Effect, Compton Scatter

Define free radical formation.

production of hydrogen and hydroxyl

How does x-radiation primarily cause cell damage?

free radical formation

Define direct theory. How often does damage occur?

photons hit critical areas in cells, infrquently

Define indirect theory. How often does damage occur and why?

formation of toxins, frequently, high water content in cell

What is this curve?

Threshold

What is this curve?

Nonthreshold

Define the threshold.

below no damage occurs

Define the nonthreshold.

any amount of radiation causes a response

How much ionizing radiation has the potential to cause changes?

ANY

In dental radiography, although the doses received by patients are

low, _______ does occur.

damage

Give the 3 periods of radiation injury sequence following exposure.

latent, injury, recovery

Define latent period.

time between exposure and clinical signs

Define period of injury.

cellular changes may occur

Define recovery period.

cells repair, low-level radiation

Repeated radiation exposure may lead to health problems such as cancer, cataracts, and birth defects. What is the term for this?

cumulative effects

During cancer treatment radiation is given in high doses in the same area, what do oncologist do during this time?

tattoos to mark areas, not radiated again

What are the 5 determining factors of radiation injury?

total dose, dose rate, amount of tissue, cell sensitivity, age

Define total dose.

amount of radiation

Define dose rate. Will a faster or slower rate cause more damage?

how exposure occurs, fast

Pertaining to cell sensitivity, what kind of cells are more prone to damage?

rapidly dividing and young cells

Are adults or children more susceptible to radiation?

children

These effects are examples of: redness of the skin, nausea, vomiting diarrhea, hair loss and hemorrhage

short term

These effects are examples of: cancer, birth abnormalities, cataracts and genetic defects

long term

This is pertaining to all cells except reproductive cells and NOT transmitted to future generations:

somatic

This is pertaining to reproductive cells and WILL be transmitted to future generations:

genetic

This radiation will affect the health of the person exposed:

somatic

This radiation will not affect the health of the person exposed:

genetic

What are the 2 degrees of sensitivity?

radiosensitive, radioresistant

Fill in the blank and give the term: cells that divide frequently

are _____ sensitive.

more, mitotic activity

Fill in the blank and give the term: immature or not highly

specialized cells are _____ sensitive

more, cell differentiation

Fill in the blank and give the term: cells with higher metabolism

are ___ sensitive

more, cell metabolism

What are the 2 systems of radiation measurement?

traditional, System International

How is EXPOSURE traditional radiation measured?

Roentgen (R)

How is EXPOSURE System International radiation measured?

Coulombs (C)

What is the limitation of exposure measurement?

measures energy reaching organism and not amount absorbed

Define exposure measurement.

ionization produced in air by x-rays

Define dose measurement.

energy absorbed in tissue

Define dose equivalent measurement.

compare effects of different radiation

How is DOSE traditional radiation measured?

Radiation Absorbed Dose (rad)

How is DOSE System International radiation measured?

Gray (Gy)

How is DOSE EQUIVALENT traditional radiation measured?

Radiation Equivalent in man (rem)

How is DOSE EQUIVALENT System International measured?

Sievert (Sv)

1 rad = ____ GY or 1 GY = ____ rads

0.01, 100

1 rem = ____ Sv or 1 Sv = ____ rems

0.01, 100

The traditional unit of exposure measurement is ______ and the SI unit is _____.

Roentgen, Coulomb

What are considered critical organs from radiation?

thyroid gland, bone marrow, skin, eyes

What are the 3 parts of inherent filtration built in an office?

glass window, insulating oil, tubehead seal

What is the added filtration for a patient?

aluminum disks

Inherent Filtration + Added Filtration =

Total Filtration

How thick are aluminum disks?

1.5 mm

What does the filtration do?

blocks long and low

What is the maximum kVp a 1.5 mm aluminum disk can block?

70

What kVp can a 2.5 mm aluminum disk block?

above 70

What is the distance of lead collimator?

2.75 inches

Is a round or rectangular collimator better for reducing patient exposure?

Rectangular

What percentage does a rectangular collimator reduce radiation?

60-70

To protect the patient a ______ PID is needed, less divergence of the beam occurs.

longer

What is this object? How does it help protect the patient?

film holder, reduces movement

What is this object?

lead apron

What is this object? How much does it reduce the radiation dose?

thyroid collar, 50%

____ receptor speed is the most effective way of reducing patient

exposure to radiation

Fast

What is the fastest film available?

F-speed (Insight)

______ _______ reduce exposure time of F-speed by 50%.

Digital Sensors

What kVp range reduces the skin dose and patient exposure?

70-90

Give the 9 most important aspects of protecting the patient.

1.5-2.5 filtration, collimator, long PID, film holders, fast film, lead apron, high KVP, no errors, judgement

How far away do you need to stand from the x-ray tube? (at least!)

6 feet

You need to avoid the path of the ____ beam that travels in a _____ line. Position yourself _____ to the primary beam.

primary, straight, perpendicular

Define shielding in operation protection.

protective barriers (walls)

What is this and where is it worn?

Radiation Monitoring Badge, waist

What is the maximum permissible dose for workers?

5 rems year

What is the maximum permissible dose for the general public?

0.1 rem year

Radiation workers must not exceed an accumulated lifetime dose. This is calculated by multiplying the workers ____ by ___ msv:

age, 10

Give the cumulative occupation dose for a 50 year old worker.

500 mSv

What is the Alada concept?

as low as diagnostically acceptable

What is the Alara concept?

as low as reasonably achievable