Radiology I Flashcards
Radiation is the transmission of energy through space and matter and occurs in what 2 forms?
Particulate
Electromagnetic
Radioactivity releases alpha or beta particles or gamma rays generated where?
Inside the nucleus
Oral and maxilofacial radiology involves only what type of radiation?
Electromagnetic
What type of radiation in the electromagnetic spectrum is capable of ionizing matter?
High energy (UV and up)
T/F
Electromagnetic radiation is generated when the velocity of an electrically charged particle is altered
True
The energy of dental x-rays is 60k to 90 k…. (unit?)
eV
The x-ray tube is surrounded by insulating material, usually what?
oil
The X-ray tube has electrons stream from the ______ to target the ______.
Cathode
Anode
*energy from some e- is converted into x-rays
The Filament (the source of electrons within an x-ray tube) is a coil of ______ wire.
The Focusing Cup is a negatively charged concave reflector of ________ surrounding the Filament.
Tungsten
Molybdenum
The Anode is a ______ target embedded in copper
Tungsten
The sharpness of an x-ray image ________ as the size of the focal spot Decreases.
Increases
What type of Radiation primarily emanates from an x-ray tube?
Bremsstrahlung Radiation
*German for “braking radiation”
Bremsstrahlung Radiation generates x-ray photons with a continuous spectrum of energy and the beam is usually described by its peak operating voltage which is what?
70 kVp
*so, fluctuated up to 70
The exposure time of an x-ray takes how long?
*time is directly proportional to photon exposure
fractions of second
The number of photos that reach the patient and image receptor is directly proportional to what 2 things?
current (mA)
time (s)
Beam quantity/intensity refers to what?
Number of photons in x-ray beam
What factor is related to the Tube Voltage Peak (kVp)?
Quality (meaning energy of x-ray beam)
Increasing the kVp of an x-ray increases what 3 things?
photons
mean energy of those photons
maximal energy of photons
T/F
Low energy photons that can’t reach the receptor still might do damage to the patient and these can be removed by a filter
True
There is inherent filtration the x-ray passes through like glass, oil, etc. as passes through the machine, but what kind of filter preferentially removes low Energy photons?
Aluminum
T/F
The Collimator is a metallic barrier used to restrict x-ray size and is Round or Rectangular
True
The Collimator improves the image quality by decreasing what?
Scattered Radiation produced by absorbed photons
Describe the Inverse Square Law that applies to x-ray beams.
Double distance, intensity of beam is now 1/4
X-rays have an Incident Beam, Attenuation, and Scatter - what are the 3 types of Attenuation?
Coherent Scatter 7%
Photoelectric absorption 27%
Compton scattering 57%
A Coherent Scatter is the change in direction of a photon, a Compton Scatter involved both a ______, like Photoelectric Absorption, and a scattered photon of _____ energy
Recoil Electron
Lower
T/F
Different tissues have different Radiosensitivities, so effective dose is a calculation of radiation type and tissue type to determine risk of cancerous formation
True
X-rays travel at the speed of light and have no ______ and no ______
mass
charge
T/F
X-rays cause fluorescence and ionization
True
T/F
Males have a higher chance of developing cancer throughout life
True
44% vs 37%
Ionizing Radiation is able to remove what?
Orbital e- from atoms
Radiation exposure is measured in what?
Roentgen (R)
What is used to compare the biologic effects of different types of Radiation?
unit?
Equivalent dose = REM - roentgen equivalent man
Sievert (Sv) = 100 rems
T/F
The Effective dose expresses radiation risk to the whole body even though whole body was not exposed and sums the Equivalent dose to each tissue/organ and a tissue weighting factor
True
T/F
The amount of radiation on the skin (Skin Entrance Dose) is the same as the Effective Dose
False
The amount of radiation incident on an organ:
Radiation absorbed by tissue:
Biological comparison of different Radiation types on different Tissues:
Organ dose
Absorbed dose
Equivalent dose
What dose is used to estimate radiation risks, compares radiosensitivities, weighting factors and is calculated in Sieverts?
Effective Dose
T/F
Salivary Glands are highly Radiosensitive
False
- down around skin
- *bone marrow highest
Example of a Direct radiation effect:
Example of an Indirect radiation effect:
alters structure/function of molecule ***(1/3)
water ionization - free radical ionization
Indirect Attack causes ____ of DNA damage
2/3
The cell killing is Dental Radiography can be described as…
negligible
T/F
The primary risk from dental radiography is the unlikely chance of radiation-induced cancer
True
What are the critical organs affected by Radiation?
3
Bone Marrow
gonads
Thyroid
The Effective Dose, based on tissue type, is measured in what?
Sieverts
Deterministic effects are caused by Lethal DNA damage and cell death, while Stochastic effects are based on what?
Gene mutation
*leukemia, thyroid cancer, etc
Bone marrow, testes, _____, ______, and _____ are highly radiosensitive organs.
Lymphoid organs
Intestines
Mucous membranes
T/F
Neurons and muscle have Low Radiosensitivity
True
Radiation is a weak mutagen and there is no evidence for a dose ______
Threshold
*damage possible at any dose
T/F
Germ cell mutations arising from radiation are possible, but have not been observed in humans
True
*Hiroshima/Nagasaki didn’t pass on defects
T/F
Radiation might activate latent carcinogenic viruses or create conditions that favor tumor growth
True
The most radiosensitive cells tend to have high mitotic rates, undergo many future mitoses, and are the most primitive in differentiation.
What are the two exceptions?
Small lymphocytes
Oocytes
The most radiosensitive tissue is Bone Marrow, what is the least?
Nerve cells
Cells are most radiosensitive at mitosis and least sensitive during what phase?
Late S
The average energy released from ionization and excitation to absorbing medium per unit track length:
*most widely used term for comparisons of the quality of different radiations
Linear Energy Transfer (LET)
X-rays have ___ LET, while Alpha particles and Neutrons have ____ LET
low
high
T/F
High LET radiation tends to generate clustered DNA damage, while low LET radiation creates isolated lesions on DNA
True
100 Gy, death in 1 to 2 days by:
10 Gy, death in 5-10 days by:
2-5 Gy, death in 3 weeks by:
cerebrovascular syndrome
GI syndrome
Hematopoietic syndrome
2 Gy exposure will result in Transient ______ in hours and last 1 -2 weeks
Erythema
focused 10 Gy can result in Dry _______
above 15 Gy ______
Desquamation
Moist Desquamation
When during a lifetime is cancer more likely to be fatal?
Early
*changes around 30
T/F
A fetal dose of radiation can double cancer rates
True
T/F
Dental radiographs have a scatter dose to a fetus that is indistinguishable from background radiation
True
*therefore, cannot produce birth defects (this is motivated reasoning, but whatever)
Rectangular Collimation can decrease the radiation dose by how much?
90%
What is the term that expresses the “one in a million” chance of things?
Micromort
Dental x-rays are ___ mrem
NY to Cal flight ___ mrem
background radiation ___ mrem/yr
3
5
300
Long plane flight = 1 Micromort
The average man in his 50’s has a ____ micromort day risk
Average woman in her 50’s has ___ micromort day
- 1
1. 3
400 million x-rays taken/year in the US, How many dental?
100 million
Of all the Ionizing Radiation a person receives a year in the US about ____ is background and ____ is medical
What % is Dental?
half
half
2.5%
Because the effects of ionizing radiation at low doses are not fully understood, what concept is invoked?
ALARA
as low as reasonably achievable
What is the Maximum permissible dose of whole body radiation/year?
Lens of eyes?
All other specific areas of the body?
50 mSv
150 mSv
500 mSv
T/F
The MAD - maxi accumulated dose is 10 mSv x Age
True
F speed film reduces radiation by:
Rectangular Collimation reduces dose by:
60%
2/3
Exposures should use Thyroid Collars and be at w/ _______ kVp
60-70
T/F
The image receptor holding device is more accurate and reduces image retakes
True
Aluminum absorbs low energy photons, what absorbs highest and lowest energy?
Rare earth metals
T/F
The focal spot receptor distance can reduce skin dose when moving closer
True
What distance should personnel be from the radiation source?
6 feet
*behind lead glass window or mirror
Large pts increase exposure time by ___%
Small/child/edentulous pts decrease by ___%
25
30
Intensity = 1/D squared
Inverse Square Law
What is the Maximum Allowable radiation dosage from diagnostic radiography?
No Limit
T/F
A Lithium fluoride crystal can be used as a Personnel Monitoring Device
True
T/F
Rapid and accurate diagnosis is usually most beneficial to the patient
True
The average medium FOV CBCT scan carries a ____ micromort risk
5
Potential risk to a fetus is _______
Fetal exposure is entirely ______
childhood cancer
indirect
T/F
Pregnancy is a Contraindication to diagnostic radiography
False
Dental radiographic images contribute to _____% of total Exposure from medical imaging
- 26%
* despite being 1/4 of all medical imaging
5 hr airline flight = 25 uSv or ___ pan and ___ BW’s
1 pan
2 BW’s
Average occupational radiation dose is ___% of allowable exposure
1%
T/F
There are no limits on the exposure a pt can receive from diagnostics, etc
True
1 byte = ___ bits
8
The grayscale puts black at 0 and white at _____
255
The bit scale is:
bit depth, gray scale
exponential
What are the 2 types of resolution in Digital imaging?
Spatial - pixels, dpi, etc
Contrast - how many shades
Aside from Spatial and Contrast resolution, the ____ also must have good resolution in digital imaging
Receptor
What are the 2 types of Digital Detectors?
Solid State
Photostimulable Phosphor (PSP)
CCD and CMOS sensors are what type?
Solid State
Intraoral CCD is ____, while intraoral CMOS is ____
wired
wireless
T/F
Extraoral Solid State detectors can be Digital Direct, Panoramic, or Cephalometric sensors
True
T/F
PSP, Photostimulable Phosphor are the same size as film and disposable
False
100% re-usable
In Storage Phosphor Technology, the Latent Image produced on the plate goes through what?
***definitely on test
Red Laser Scan
The latent image on a ______ can be erased and 100% re-used.
PSP - Photostimulable Phosphor
PSP cycle: Acquisition, ______, view, erase, hygiene
Laser Scanning
The advantage to CCD/CMOS (solid state) over PSP is what?
Direct image
The advantage of PSP over CCD/CMOS are what 3 things?
Film-like
Large exposure latitude
Cheap plates
T/F
Brightness, Contrast, and Gamma adjustment are types of Digital Processing to enhance image
True
T/F
LUT inversio, Color conversion, and Embossing are all considered “toys” and aren’t real image enhancement
True
T/F
Resolution is not that important for detecting dentoalveolar disease, contrast and density play a much larger role.
True
T/F
Most systems have more resolution than the human eye can detect
True
The Sensor Resolution is ____ Microns (XIOS Plus)
15
In X-ray film, the ______ is sensitive to x-rays and visible light, and the _____ supports it.
Emulsion
Base
Emulsion is composed of what?
Silver halide/bromide
Direct Exposure Film is exposed by X-rays, _____ film is used with intensifying screens and extraoral projections
This type of film is sensitive to what?
Screen film
Visible light (and x-ray)
How would you know if X-ray film is loaded backwards?
Lead film on back casts pattern and image is light
In an Intensifying Screen, what causes visible light from x-rays?
Inorganic salts/phosphors
***The use of Intensifying Screen has what effect on patients?
REDUCES dose of x radiation
Developer, water bath, fixer, water, dry
Film processing
The _____ converts silver bromide crystals with neutral silver atoms deposited at latent image sites into black, solid silver metallic grains
Developer
What removes unexposed, undeveloped silver bromide crystals, leaving the film clear in unexposed areas?
Fixer
Light, radiopaque areas means:
Dard, radiolucent areas means:
few photons reached film
many photons reached film
Film that is too light can mean what?
Film that is too dark?
underexposed
overexposed
T/F
Spots on film can be from faulty processing, blurred can be caused by pt. movement
True
Sharpness can be increased with a small focal spot, increasing distance between _____, and minimizing distance between ______
focal spot and object
object and image receptor
Foreshortening can be caused by not aligning with the _____.
Elongation can be caused by not aligning with the ______
tooth (or other object)
film/plate
What technique minimizes distortion?
Paralleling
In a tube shift or dual image technique what rule determines where objects are in relation to one another?
SLOB
Same Lingual, Opposite Buccal
Mesial shift, object moves mesially:
Mesial shift, object moves distally:
Lingual side
Buccal side
Eggshell effect:
rim is radiopaque (3D effect)
The backbone of imaging for the general dentist is Intraoral Radiographic, what are the 3 Categories?
Periapical (PA)
Bitewing (BW)
Occlusal
A Full Mouth (FMX) or Complete Mouth Series (CMS) consists of what?
PA’s, BW’s, and 18 images
T/F
The use of correct imaging modalities often excludes cone beam CT, etc
True
*used intraoral imaging instead
What are the drawbacks to Panoramic imaging?
Resolution
Large field of view
What are the drawbacks to cone beam CT (CBCT)?
4
Cost
Dose
restoration interference
artifacts
T/F
Overlap can be caused by bad angulation of the Tube Head
True
What method may be useful when the operator is unable to apply paralleling technique for whatever reason?
Bisecting Angle Technique
T/F
Position the tube head to the side of the pt that will be radiographed
True
The open end of the cylinder must be ____ with the guide ring
Flush
What are the 6 Rules for Intraoral Imaging
(principles of Dental Imaging)?
Receptor completely covers teeth
Vertical sides of receptor parallel with long axes of teeth
Horizontal sided of receptor parallel with horizontal plane of teeth
Open end cylinder parallel with receptor
Central ray enters Proximal Embrasure at 90 degrees
Central ray directed at center of Receptor
When are Vertical Bitewings used?
Perio disease
*alveolar crest more apical
T/F
Occlusal Radiographs can see more structures, are used if pt can’t open mouth, can determine locus, and are limited by receptor size
True
What force carrier particle makes up the x-ray beam?
Photon
What has greater energy than x-rays?
Gamma
Quantum Theory of radiation has been successful in correlating experimental data of what?
Production of X-rays
***polarization, refraction, diffraction all wrong
What % of the kinetic energy of e- that hit the anode are converted to heat?
99%
Increasing the kVp does what 2 things?
Increases # photons and Mean Energy
What is the primary means of dental x-ray attenuation?
Thickness of the mass and energy of the beam
What is the most common type of scattering?
Compton
When lower energy photons are removed by aluminum filtration, the mean energy ____, and the beam intensity _____.
increases
decreases
Deterministic effects have a ______
Stochastic effects have no _____
threshold
threshold
What tissue type of the Oral Mucosa is particularly Radiosensitive?
Basal cells
In a child, radiation therapy may destroy what (esp if combined with chemo)
Tooth buds
If a pt has head/neck therapy avoid intraoral radiographs for how long?
6 months
What organ has the lowest susceptibility to induced cancer?
Salivary Glands
Most of the radiation the world’s population is exposed to comes from what?
Radon
Dental x-rays account for less than 1% of the average daily human exposure.
True
E/F speed is faster than D speed, what has more quality?
Same
State regs require the x-ray beams to be _______ cm or ______ inches to the pts skin surface.
7 cm
2 3/4 inches
What size dental films is normally used for adult bitewings?
Size 2
How long can a safe light be used in a dark room before it affects the picture?
5 minutes
Increasing the focal spot of the film distance does what?
Decreases film density
What makes up the Antral Y?
Maxillary sinus and the floor of the nasal cavity
What is above the Maxillary molars on a radiograph?
Maxillary sinus
A “U” shape on every board exam is what?
Zygomatic process
T/F
The Hamulus will be at the same level as the molars
True
Striations through the Maxillary sinus are what?
Blood vessels in lateral wall
Ridges on the top of the palate:
Torus palatinus
Inferior nasal cavity bone
Inferior turbinate
