Module 3 & 4 : Image Recording and Storage Devices Flashcards
three reasons why having a recording device is important
- radiologist/cardiologist is not always present
- required for teleradiography
- images can be used for comparison
7 ways to record images
- multiformat cameras
- laser imagers
- color thermal printers
- fibre-optic recorders
- video thermal printers
- video tape recording
- computer storage
what was the most common means of storing a hard copy of images
- film
what are the three different types of film
- transparency film (negative)
- polaroid film (positive)
- paper film
what was the most common type of film used and why
- transparency film
- several years of shelf life and infinite resolution
disadvantages of film
- storage space
- ease of retrieval for viewing
- cost
- chemicals
how is transparency film constructed
- in layers with an acetate base toped with an emulsion layer that contains silver bromide crystals and a suspension gelatine
- light strikes the crystal to form the latent image and are converted to silver grains with chemical processing
with film how are the images made darker
- exposure to light increases more silver grains are activated and the darker the image becomes
what is film speed
- how fast it darkens
what two things must be matched to the monitor used for exposure
- film speed
- contrast
how long did it take to manually process transparency film
- 1 hour per film
4 steps to automatic processing
- development
- fixing
- washing
- drying
how long does it take to automatically process film
- 1-2 minutes
disadvantage to transparency film
- variations in density/contrast of processing
- use of chemicals was also expensive and caustic to the environment
- takes a long time
what is the multiformat camera
- one of the most common devices used to expose transparency film
- essentially a CRT that could fix an image onto the film
- has excellent gray scale and used a shutter and a lens to control the exposure time and position
disadvantages to multiformat camera
- CRTs have curved screens which could distort the image
- high quality lens increases cost
- one camera per machine
- dust and movement
what replaced the multiformat camera
- the laser camera
what does laser stand for
L- light A - amplification by S - stimulated E - emission of R - radiation
why are the intensity and size of the laser beam controlled
- to improve contrast and detail resolution
could more than one machine/modality use one laser camera
- yes
was the film used by laser camera sensitive or insensitive to light
- insensitive
what does laser camera film contain
- laser sensitive carbon layer that when activated by heat cause the carbon to stick and the back can be peeled off
what is polaroid film
- requires no special processing
- relatively inexpensive
- spatial resolution poor
how did the black and white polaroid film work
- exposure to light creates white on the film using silver halide crystals
what are the three layers of color polaroid film
- RGB that are activated with exposure
what is the video thermal printer
- fairly good quality but not as good as the multi format or laser printer
how does a video thermal printer work
- video signal is stored in the memory and transferred to a thermal printing mechanism
- the heat sensitive paper is then passed along a mechanism and the heat creates a gray scale where the shade of gray corresponds to the amount of heat produced
what was one of the biggest problems for video thermal printer
- archival stability
- could not place exposed film near a heat source or image would degrade over time
what is the color video printer
- similar to video thermal printer
- uses dye on paper
- if no dye is present then paper is white and RGB together make black
- printing requires single pass of each color which increases printing time
what is a magnetic tape recording
- used a lot
- gave ability to capture a video as opposed to a still picture
what is the format of the cassette for magnetic tape recorder and what were they played on
- video home system (VHS)
- video cassete recorder (VCR)
what is a super VHS (SVHS)
- better spatial resolution and used in more hospitals
how does a magnetic tape recorder work
- contains magnetic dipoles that can be aligned in a magnetic field where the strength of the signal determines the alignment
how is the tape played back
- tape passed through a red head and the fluctuating magnetic field produces a video signal
- an audio track can also be included in sync
what is the spatial resolution of a VHS
- 240 lines
what is the spatial resolution of a SVHS
- 200 lines
can both VHS and SVHS be played on both VHS machines and SVHS machines
- VHS machines = VHS only
- SVHS = VHS and SVHS
what are magneto-optic disks
- combined two technologies
+ magnetic and optics - large memory space and rewritable
- not susceptible to magnetic damage
how are the MO disks created
- laser heats the disk past its currie point so the magnetic crystals can be realigned when placed in a. magnetic field
how were the MO disks read
- a weaker laser scatter the light off the disk and the intensity is read to create the signal
one advantage and disadvantage to MO disks
- could hold hundreds of MB
- lack of compatible drives
what does PACS stand for
P - picture
A - archiving
C - communication
S - system
6 advantages to pacs
- storage
- external viewing
- connection to other modalities
- web access
- image quality
- time factor
how does a pacs system work
- electronically transfers digital data from a machine to a workstation
- with the internet images could be sent anywhere
what was a challenge with pacs and how was it solved
- manufacturers all use different programming and coding to digitize there images
- set a universal standard for compressing images called DICOM
what does DICOM stand for
D - digital
I - imaging
CO - communications in
M - medicine
disadvantages to pacs
- large cost investment (but eventually pays off)
- complexity of equipment and the additional backup require additional staff for upkeep and maintenance
