test 2 - quizlet Flashcards
purpose of diagnostic imaging?
The primary purpose of diagnostic imaging is to transfer the information from an x-ray beam to the eye-brain neurological system of the interpreting radiologist
The ____________ beam aka exit x-ray beam: exits the tube and enters the patient resulting in series of events discussed previously
remnant
True or False: Using intensifying screens will allow only 5% film exposure or “blackening” due to direct x-ray-film interaction. This will significantly reduce the patient’s dose
TRUE
True/False: After interaction with matter the exit beam reaches the intensifying screens of a cassette. The screen will fluoresce emitting light and exposing (blackening) the film
TRUE
In Film design there are 2 basic parts, what are these parts?
base and emulsion
True/False: Most films are coated with double emulsion or screen-film
TRUE
__________ is the part where the image is formed
emulsion
__________ is the part where the image is formed
Emulsion
The history of development of modern film base went from _______ plates to ____________ films to __________ material, which is what we use today
glass plates, cellulose, films, polyester material
what does the base provide?
The Base provides rigidity and dimensional stability.
emulsion is made of gelatin and contains what crystals?
Silver halide crystals (SHC) 98%-silver bromide with 2% silver iodide
When x-rays and light interact via(PE) and Compton with SHC- the initial or ________ image is formed
latent
During manufacturing process a part of the emulsion is “contaminated” by silver sulfide which is located in the center or just to the side of the Silver bromide (SHC). This is known as a what?
sensitivity centre or speck
True or False: When photons strike the emulsion and SHC, the speck is responsible for attracting and trapping an ion of silver (Ag+) and the electron, producing the latent image
TRUE
Modern SHC are _________ in shape which provides for better distribution of coating and more uniform exposure
tabular
True/False: Larger crystals will develop faster providing a lower scale of radiographic contrast and smaller crystals will develop slower providing a higher scale of contrast
TRUE
When some x-rays and emitted light photons from the intensifying screen interact with SHC it occurs primarily via _______________ and some ____________
photoelectric and some compton
what is a secondary electron and what does it do?
secondary electrons are formed from PE and compton x-rays hitting the emulsion and have sufficient energy to dislodge other electrons in the lattice, Thus a single x-ray/light photon is capable of dislodging a number of electrons which migrate to the sensitivity centre of the SHC and become trapped or locked. Once the sensitivity centre captures the photoelectron it attracts interstitial ionic silver (Ag+) and the latent image is formed
True or False: In the optimally exposed film most SHC have collected and retain 4-10 silver atoms at their sensitivity centre with the latent image being formed. At this point the Latent image is invisible and It requires to be processed or chemically converted to manifest image or being developed
TRUE
__ films are used in dentistry
direct
True/False: In mammography, a single intensifying screen is used on the back side and a single emulsion film
TRUE
Size and distribution of SHC plays an important role in film __________
contrast
________ contrast film’s emulsion contains small SHC with relatively uniform distribution and ________ contrast films contain larger SHC and of less uniform distribution
high
low
True or False: Screen-Film is widely used within the image receptor (IR) and is commonly used with the cassette’s intensifying screens.
TRUE
Crossover exposure may occur when screen light crosses the base and exposes the opposite emulsion. How can this be avoided?
this is solved by adding a dye or crossover control layer to film base
Manual processing- before automatic processing was introduced, manual processing took approximately _________ and started with wetting or soaking of the film then immersing it in the developer, washing it with running water and hanging it to dry
1 hour
What is the Automatic processing sequence?
Developing-Fixing-Washing-Drying
How long does the automatic processing sequence take?
in 1987 Konica developed automatic processing with 45 sec per step system.
What does the developing step in an Automatic processing sequence involve?
electrons are supplied to ionic Ag+ to reduce it to metallic silver: (Ag+ + e- =Ag). The exact chemical composition of the developing agent is closely guarded by the proprietor. The sensitivity centre of the latent image has been exposed or reduced. When developer is introduced it can easily overcome the electrostatic charge(-) on the surface of the silver halide crystal and penetrate it, completing the reduction (exposure) process. Thus reducing ionic Ag+ to metallic Ag or black silver grains seen as exposed parts of the radiographic film. The process is repeated over and over
The main components of the developing step in an Automatic processing sequence are ___________ and _____________. Both are reducing agents with high electron content
hydroquinone and phenidone
In the developing step in an Automatic processing sequence ___________ acts faster and produces more light shades
phenidone
In the developing step in an Automatic processing sequence _______________ acts slowly and is responsible for more dark shades
hydroquinone
What does Fixing the film insure?
Fixing-this process ensures archival quality of the film and is added to remove remaining unexposed and underdeveloped SHC from film emulsion
what is being used for fixer?
Sodium thiosulfate known as Hypo is being used
In the fixing step Acetic acid, known as a(n) ____________ is added to neutralize the pH of the emulsion and stop the developer action. One potential problem is retention of the fixer (Hypo) which continue oxidizing, slowly combining with metallic silver forming Ag2S (Silver Sulfide)
activator
What step comes after fixing and why?
Washing is the next step which ensures removal of all fixer so that the film will become of diagnostic and archival quality
What solvent is used in the washing step?
H2O is a universal solvent and has been employed during this step
What step comes after the washing step and how is it performed?
Drying- warm dry air is blown at the drying chamber
An _______________ screen is used in the cassette to intensify the effect of the X-ray photon by producing more light photons by making certain compounds fluoresce
intensifying
True or False: The use of Intensifying screens decreases the mAs required to produce a particular density image, thus decrease the amount of patients’ radiation dose significantly
TRUE
True/False: In cassettes which use double emulsion films, two Intensifying screens are used, mounted on two sides of the cassette and the thickness of an intensifying screen is about 0.4 mm
TRUE
True or False: Rare earth elements are used in present day Intensifying screens as they are faster and have higher absorption and conversion efficiency: such as gadolinium, lanthanum, and yttrium
TRUE
True/False: Compounds in Intensifying screens need to fluoresce and not Luminesce because Fluorescing will involve a single film exposure where as Luminescing will continue to glow, exposing the film further that is undesirable
TRUE
It is important to note that the color of the light emitted (wavelength) from an Intensifying screen must match the light sensitivity of the film used. This is known as ____________ matching
spectral
