Radiology Exam 3 Flashcards by Abby Fischer

Direct effect is and accounts for ___ of biologic effects:

the ionization or excitation of atoms w/in DNA leading to free radicals; these free radicals can induce biological changes
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Indirect effect is and accounts for ____ of biologic effects:

free radicals that can damage DNA are formed by the ionization of nearby H2O molecules; if O2 is present, H2O2 is formed
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4 DNA changes that radiation can cause:

break single or double DNA strands
cross-linking between separate DNA strands
substitute or lose a base
disrupt H bonds between strands

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Which type of breakage is responsible for most cellular killing?

Double strand breakage

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What two types of DNA changes may lead to chromosome aberrations?

radiation-induced breakage

2. incorrect rejoining in G1 phase

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What are the three LETHAL chromosomal aberrations?

Ring formation
Anaphase bridge
Dicentric formation

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Name two non-lethal chromosomal aberrations:

Symmetric translocations

Small deletions

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Cataracts, osteoradionecrosis, xerostomia, and stunted fetal development are examples of _______ effects. Cancers, tumors, and heritable disorders like leukemia, thyroid cancer, breast cancer, and salivary gland tumors are examples of ________ effects.

Deterministic (osteoradionecrosis, xerostomia, and stunted fetal development)
Stochastic (cancers, tumors, and heritable disorders like leukemia, thyroid cancer, breast cancer, and salivary gland tumors

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If there is sublethal damage to cells, resulting in cancer formation or heritable mutation, this is _______.

Stochastic effect

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If there is a mass killing of a large number of cells, this is _______.

Deterministic effect

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If the radiation dose does not exceed threshold level in _________, you 1. would or 2. would not see effects.

Deterministic effect

Would not

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In _________, any dose has potential to induce this effect.

Stochastic effect

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In ________ effect, the severity of the damage is proportional to the dose. In other words, the greater the exposure, the greater the cell killing.

Deterministic effect

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In _________ effect (like an action potential), there is an all or none response. In other words, the severity is independent of dose and you either have an effect or you don’t.

Stochastic

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In deterministic effect, you ________ and is _______.

must meet threshold

- dose dependent

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In stochastic effect, cells _____ but are _____ and is _______.

survive but are mutated

- dose independent of clinical effect

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What type of curve does a deterministic effect have?

Threshold curve

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What type of curve does a stochastic effect have?

Linear curve

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What is the short term effect of deterministic effect?

cell death

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What is the long term effect of deterministic effect?

progressive fibroatrophy due to damage to the vasculature (damage causes a narrowing of the lumen, nutrient transfer is impaired, cell death, replacement by fibrous CT)

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What is the dose of radiation given as treatment for H&N cancers?

60-70Gy over 6-7 weeks.

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What are three major effects and consequences from radiotherapy in the oral cavity?

Hyposalivation/Xerostomia- pH of 5.5 causing radiation caries
Mucositis- ulcers, difficulty with food intake and dentures, secondary yeast infection caused by Candida albicans
Taste loss

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What causes trismus and what is the consequence of trismus?

Trismus is the inflammation and fibrosis in muscles of mastication causing limited opening

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When should you complete dental treatment and improve oral hygiene?

Before radiation therapy

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What is the modifying factor of dosage?

Damage is proportional to the dose above threshold

What is the modifying factor of dose rate?

A higher dose rate causes more damage (1Gy/min vs. 1Gy/week)

Do you have more cellular killing with the presence of oxygen or without the presence of oxygen? What is an example of tumor treatment with this repercussion?

with the presence of O2 | I.E. fractionated hypoxic tumor treatment

______ linear energy transfer (LET) causes more biologic damage. What is LET?

Higher; energy deposited per unit path length

Three stochastic effects:

- sublethal DNA damage - Carcinogenesis - Heritable effects

The total energy deposited in matter per unit of mass:

absorbed dose (energy per unit of mass so... Joules = energy and kg is unit of mass = J/kg = Gy)

What is the SI unit for absorbed dose (remember the definition of absorbed dose)?

- Gray (Gy) | - J/kg

What does the equivalent dose take into account?

- accounts for radiations with different biologic effects | - it's a radiation weighted dose

``` What are the radiation weighting factors for: X-ray/Gamma rays: Protons: Neutrons: Alpha particles: ```

X-ray/Gamma rays: 1 Protons: 2 Neutrons: 2.5-20 Alpha particles: 20

What is the formula for equivalent dose?

radiation weighting factor x absorbed dose

What is the SI unit and traditional unit for equivalent dose?

Sievert (Sv): SI unit | rem (roentgen equivalent man): traditional unit

What is the conversion from sv to rem?

1Sv=100 rem

What is the effective dose?

Effective dose is the tissue-weighted dose (the risk comparison of CMS vs a chest x-ray)

What are the radiosensitivities of: Red bone marrow, breast, colon, lung, stomach: Gonads: Bladder, esophagus, liver and thyroid: Bone surface, brain, salivary glands and skin: Sum of all other tissues:

Red bone marrow, breast, colon, lung, stomach: .12 Gonads: .08 Bladder, esophagus, liver and thyroid: .04 Bone surface, brain, salivary glands and skin: .01 Sum of all other tissues: .12

What is the equation for the effective dose?

tissue weighting factor x equivalent dose

What is the SI unit for effective dose?

What is the linear non-threshold hypothesis?

there is a linear relationship between dose and the risk of inducing a new cancer, even at a very low dose

Rank these in order from least sensitive to most sensitive: Red bone marrow, breast, colon, lung, stomach: Gonads: Bladder, esophagus, liver and thyroid: Bone surface, brain, salivary glands and skin:

Bone surface, brain, salivary glands and skin: .01 Bladder, esophagus, liver and thyroid: .04 Gonads: .08 Red bone marrow, breast, colon, lung, stomach: .12

What is the dose of one day background exposure?

~8 microSv

There is a chart on page 2 of the second packet on dosages from different x-ray procedures. Check it out

Is there a dosage limit for patients?

No, ALARA (as low as reasonably achievable)

If you exceed doses of _____ during pre-implantation and organogenesis, or _____ during fetal period, you have a high risk of deleterious effect.

- 100 mSv | - 200 mSv

What would be the amount of radiation dosages of 100mSv during pre-implantation or organogenesis?

100,000 radiographs

What is UNMC's policy on radiographs on pregnant women?

We don't take radiographs on women who are pregnant.

What are the annual stochastic effect limits for dentists, hygienists, and assistants?

less than 50 mSv/year

The annual deterministic effect limits for the lens of the eyes are ______ and the for the skin, hands and feet are ______.

lens of eye: 150 mSv/year | skin, hands, feet: 500 mSv/year

Once pregnancy is declared, the embryo/fetus exposure limit is ____ which is the equivalent of ____ exposures per year. Fetal exposure limits for CMS are ______.

.5 mSv/ month equivalent of 50 exposures in one month's time 1 microGy

If you receive an annual dose of greater than ____, you should wear a ______.

1 mSv | dosimeter

``` Percentages of background radiation: Radon: Space: Internal radionucleotides: Terrestrial: ```

Radon: 73% Space: 11% Internal radionucleotides: 9% Terrestrial: 7%

Background radiation per year from environment:

3.1 mSv/year

For limiting radiation exposure: E/F ___ D Rectangular colliimator ____ round collimator Long cone ____ short cone

E/F > D Rectangular colliimator > round collimator Long cone > short cone

With a cone beam CT, there is a ______ source of ionizing radiation.

cone-shaped

Raw data at the detector are converted to ______ by a computer _____ utilizing filtered back projection.

cross sectional images | computer algorithm

What is the scan time of a CT scan? Patient can be positioned in ______ for CBCT?

- less than 20 seconds | - sitting, standing, or supine

ALARA:

as low as reasonably achievable

What is automatic exposure control?

the CBCT uses automatic exposure control in order to produce an ideal image w/out over radiating the patient. Takes a scalp (sp?) view which allows photon attenuation then adjusts the output of photons)

DICOM:

digital imaging and communications in medicine

What are DICOM?

the files coming out of the cone beam; name, DOB, etc.

What type of field of view is better and why?

smaller; reduces chance of misdiagnosis

What are the advantages and disadvantages of the i-CAT?

Advantages: patient is sitting so more comfortable and stable Disadvantages: patient can't use if in wheelchair

What are the advantages and disadvantages of the NewTom VGI?

Advantages: wheel chair accessible Disadvantages: not as stable

What are the advantages and disadvantages of the NewTom 5G:

Advantages: good image quality, good for sleep apnea Disadvantages: need large office space

Which field of view would you use for ortho?

15x15

What FOV will we use the most in general dentistry?

8x8 and 6x6

What is the most desirable thing about constructing an awesome algorithm?

you can reduce kVp and mA

The lower the kVp and mA the _______ the quality of the CT image.

the lower the kVp and mA the poorer the quality.

Is there ionizing radiation in an MRI? Why or why not?

No, a radio frequency (RF) pulse is used to construct the image.

What measurement is used to measure the MRI and what is its equivalent?

Tesla; 1-3 tesla (1.5T = 30k x earth's magnetic field

What resolution is very accurate in an MRI?

soft tissue resolution

How much do MRI's cost? Is it a long scan time or short scan time?

$1,000,000/Tesla | long scan time

What type of beam does a computed tomography or MDCT use and what is its pathway?

fan beam | helical/spiral

How many multiple detector arrays does CT/MDCT use?

64 to 128 detector arrays

What is the CT/MDCT quick scan and what is the advantage of using it?

.25 second/rotation it reduces motion artifact rotating anode

What is the operating kVp of CT/MDCT?

80-140 kVp (typically 120)

Rank in order of least to greatest radiation dose: CBCT MDCT MRI

MRI CBCT MDCT

Rank in order of worst to greatest spatial resolution: CBCT MDCT MRI

MRI MDCT (2 to 3) CBCT (3)

Rank in order of least to greatest soft tissue contact: CBCT MDCT MRI

CBCT MDCT MRI