Radiology II Flashcards
What is the most popular imaging modality in the US?
Film
*this is on the verge of changing
If the pt is bumped during imaging, what results?
Big wave - motion artifact
What is one difference between Cone Beam CT (CBCT) and pano?
CBCT has NO magnification
Pano has magnification
What has more radiation dose, Panoramic or FMX?
*how much is the dose?
FMX
175 microsievers
FMX with Round Collimation and Film has 175 microsievers.
How much with Rectangular Collimation and Digital or F speed film?
1/5 the Radiation
What are the advantages to a Pano? (3)
What is the drawback?
one shot overview, less radiation, easy to take
less detail
Pano’s are fast and convenient but won’t show what?
Interproximal caries
PSP is how many steps?
Digital is how many steps?
2 step process
1
PSP goes into processing machine that uses what?
Laser beam
In Direct Digital imaging (the CMOS or CCD sensors), what fluoresces when exposed to x-rays and forms visible light radiographic image?
*this is on the active side of the sensor
Scintillator screen
What is on the active side of a metal oxide semi-conductor sensor?
Scintillator
What couples the scintillator screen (fluorescing) to the CMOS chip to reduce image noise?
Fiberoptic face plate
What is a Matrix of Individual Blocks?
What technology uses this?
Voxels (volume elements)
CT (computed tomographic scanning)
Voxels (volume elements) are made up of square images of matrix called ______
pixels
In either CBCT or a Pano, you need to put the pt where?
In the Focal Layer
What is the universal way to store/transfer images in medicine?
Dicomm
A Pano is made with what shape of beam?
Vertical, narrow beam
A Pano rotates around what?
Focal plane/Focal trough
Describe the center of Rotation in a Pano:
moves continuously as tube/receptor rotate around pt
T/F
The closer an anatomic structure is positioned to the center of the trough, the more clearly it is imaged on resulting radiograph
True
Film, PSP, Digital Receptors - which are similar?
Film and PSP similar
Digital receptor black box solid state
If the mandible is positioned Anterior of the bite block, what happens to the image?
If Posterior?
Minification
Magnification
Rotate a pts head toward the Right, which side is minified, which is magnified?
Right side minified *rotated further away
Left side magnified
Excessive downward chin tip will produce what in a Pano?
Excessive upward chin tip will produce what in a Pano?
Too much “smile”
Frown
If a pts head is rotated in a Pano, which side is Minified?
Side in direction of rotation
What are the 6 standard Maxillofacial Projections?
Posteroanterior (PA)
Lateral Skull
Occipitomental (Waters)
Reverse - Towne
Submentovertex
Lateral Oblique
Name 3 structures for which the Occipitomental (Waters) Projection is indicated?
Sinuses
Nasal cavity
Coronoid process
Occipotomental (Waters) Projection elevates the canthomeatal line ____ degrees
37
What projection is indicated for condylar neck and posterior wall of the maxillary sinus?
(also get in submentovertex)
Reverse-Towne projection
*head down, open jaw
What projection travels is taken vertically through the head?
Submentovertex projection
What projection is good for abnormal premolar/molar region and inferior border of the mandible?
Lateral Oblique (body projection)
What projection is good for abnormalities of the ramus/condyle region and 3rd molars?
Lateral Oblique (ramus projection)
What projection is good for the Mandibular Ramus?
Mandibular Oblique projection
Describe Submentovertex view:
Describe Waters view:
travels vertically
head up (NWA look)
Pano comes up at 12 degrees - this angle aka…
This causes horizontal structures to be displayed how?
parallax
vertically
A ghost image is more ____ than its real counterpart
blurred
What area in a Pano produces a particular angulated ghost image to the contralateral side?
Mandibular Ramus
What 2 forms of imaging have zero radiation?
MRI and Ultrasound
Basic guidelines for imaging children, radiographs 1st visit, Posterior bitewing intervals if Caries present?
If caries not present?
Adult caries present?
Adult caries not present?
6-12 months
12-24 months
6-18 months
24-36 months
CBCT software takes data and undergoes primary or 3D reconstruction once base images have been acquires. Goes through what process -
multi-planar reformation, 3D reconstruction, or primary reconstruction?
Multi-planar reformation???
When we’re talking about Cone Beam CT images vs other (medical) CT images
isotropic, mesotropic, magnification principles???
Isotropic means voxel same on each side
T/F
Sometimes better resolution film is inferior to high res digital b/c of noise
True
*digital can be better diagnostically
CCD and CMOS are ____ detectors
*can be wired or wireless
solid state
*these have the scintillator coating that fluoresces
CCD and CMOS are ____ detectors
*can be wired or wireless
solid state
*these have the scintillator coating that fluoresces
PSP makes a latent image that is scanned with what?
Laser
T/F
We see better in dim light so if you shift toward darker spectrum we see images better
True
_____ encoding takes advantage of the non-linear manner in which we perceive light and color.
Gamma
*we are more sensitive to relative differences of darker tones
Relative importance of resolution, contrast and density to detecting dentoalveolar disease.
Resolution - not really important
Contrast and Density - much larger role
What type of receptor opposite the vertical collimator of a Pano machine continuously reads exposure?
CCD - charge-coupled device
Appears higher up than real image, more blurred, larger vertical component.
Ghost images
Three types of images produced in Pano:
Real
Double
ghost
T/F
The oral airspace artifact washes out the apical surfaces of the maxillary teeth
True
What creates the most artifacts?
Motion
What is standard FOV for maxillofacial imaging?
6” close up
Effects where the risk is proportional to the dose:
Effects where the severity is proportional to the dose:
Stochastic
Deterministic
CBCT is equal to ___ days of background radiation
FMX F-speed, rectangular collimation:
FMX D-speed, round collimation:
10
4.3
47
FMX D speed round collimation to PSP rectangular collimation decreases radiation ___%
CBCT is around ___ times less radiation than D speed FMX
90
5
MDCT (medical) is ___ times CBCT dose
30
___% of calcium needs to be resorbed before seeing anything on a radiograph
10%
T/F
Dynamic Periapical allows scrolling through different views
*all kinds of indications, type of CBCT
True
CBCT stands for:
Cone Beam Computed Tomography
In CBCT software can reorient the data, optimize, view and format
True
All sides of Voxels are equal, meaning they are…
Isotropic
What CBCT software analysis is best to examine alveolar bone?
MPR - multiplanar reformation
*due to isotropic nature of voxels
An image slab in MPR (multiplanar reformation) is called…
Can slab be widened?
Ray Sum
Yes - to the point of full thickness
T/F
A selective display of voxels in the data set will result in a Volume Rendering
True
Max Intensity Projections (MIP) evaluates each voxel at its highest value as a type of ____ rendering
Direct Volume
Operator of a CBCT must provide a ______ of the entire image data set
written interpretive report
Jawline fracture sometimes won’t show up on what?
Pano
*CBCT will catch
3 orthogonal planes (high res FOV CBCT scan):
Axial (horizontal)
Coronal (fronal)
Saggital
Pixel assigned a number representing specific tissue density called a:
Hounsfield Unit (HU)
There is higher tissue contrast in MDCT b/c more radiation and scatter of CBCT
True
IV Contrast Imaging is based on ____
iodine
3 artifacts of CBCT:
Partial volume (differing densities will blur image)
Beam hardening (the more tissue goes through)
Metal streaking (metal absorbs x-ray completely)
Only place we use MRI in dentistry:
TMJ imaging
Nuclear medicine uses ___ rays
Gamma
Anterior mandible radiopaque artifact:
Lead apron
Images with Parralax aren’t ideal for implants
True
Vertical components of a ghost image are always larger and more blurred
True
