Diagnostic Imaging (no images) Flashcards
Cathode vs anode
Cathode = -
Anode = +
Ionization
process of forming an ion pair
How does x-ray work
This flow of electrons from the cathode to the anode generates a current across the x-ray tube and is called the tube current. The magnitude of this current is regulated by the milliampere control (see Fig. 1.10, mA selector), which adjusts the resistance and the current flow through the filament, thereby regulating the number of electrons produced.
select the highest mA value available and operate the machine at this setting; this allows the shortest exposure time and minimizes the chance of patient movement.
A high voltage is required between the anode and cathode to give electrons sufficient energy to generate x-rays. The kilovolt peak (kVp) selector adjusts the high-voltage transformer to boost the peak voltage of the incoming line current (110 or 220 V).
https://www.olympichp.com/understanding-differences-between-kvp-and-mas/
How is an x-ray formed
Time
Distance
Power
(intensity, energy, collimation)
what is the energy
kvp
ontrols the power of each particular x-ray particle which influences penetration of the beam through tissue → “quality of beam”
what is the exposure rate or determines the number of photons
mA- milliampere
milliamperage, works in conjunction with exposure time to impact the number of X-rays the patient is exposed to over time → “quantity of exposure = mA+Time”
ALARA
as low as reasonably achievable
digital radiography
the use of solid-state detectors is referred to as digital radiography (DR).
computed radiography plates
photostimulable phosphor (PSP) technology. This technology consists of a phosphor-coated plate in which a latent image is formed after x-ray exposure. The latent image is converted to a digital image by a scanning device through stimulation by laser light.
film parallel to object, beam perpendicular, most accurate image
Parallel technique
Caudal mandible only at 90 degrees
most common type, theory of equilateral triangles, most accurate representation of root
Bisecting angle technique
does note measure the angle for each area individually but rather relies on generalized estimates for all teeth
Simplified technique
relies on approximate angles to create diagnostic images -
90 – Mn molars, caudal PMs
45 – maxillary premolars and molars
20 – canines and incisors
Not good for: MX canine, MN premolar, MX cheek teeth cat, MX PM4 mesial root
SLOB technique for MXPM4
Same lingual opposite buccal
1. lingual/palatal root will move distally if tube shifted distal
distal root away from M1
palatal root in middle
2. lingual/palatal root will move more mesial if tube shifted mesial
distal root of PM4 imaged over M1
buccal root in middle
Images are produced by making multiple radiographs of an object which are digitized
CT
What percent of bone loss is required before apparent on radiographs
40
Uses a magnetic field and radio-frequency pulses rather then radiation. Images are based on hydrogen atoms
MRI
4 risks of DNA damage
radiation-induced cell death
heritable mutations
carcinogenesis
ionizing radiation by production of free radicals
Correction of radiographs that are too dark or overexposed
Decrease exposure time or millamps
the x-ray settings are set too high (kV and mA/s increased), there will be too much energy in the primary beam. As a result, little energy will be absorbed by the patient and more x-ray radiation will hit the detector. The detector starts off white and turns dark as radiation hits it, and as a result the image will become too dark and no longer be diagnostic.
Correction of underexposed or too white films
If the x-ray settings are set too low, there won’t be enough energy in the primary beam. A proportionally large amount of energy would be absorbed from the primary beam, meaning very little radiation would hit the x-ray detector and turn the image darker. This means there will be very little change from the detector’s original white colour, and the overall image will be too light.
What is the nose up technique
Laterorostral-laterocaudal
A type of electromagnetic radiation that does not have enough energy to knock out electrons from atoms
non-ionizing
deterministic effect
This effect occurs when cells are killed by high enough radiation and there are consequences of cell death on the function of a tissue or organ.
iodinated contract medium is administered at this dose
600-880mg iodine/kg
