Re: digital imaging

Nick Shackleton — Tue, 19 Oct 2010 18:06:40 GMT

I know I've sent this as a PM but thought I'd share this for others:

I don't have much experience with digital radiography as now working in CT and MR and had wet processing where I used to work.

If your really struggling I can see what I can put together.

There are two main types or digital systems

CR (computed radiography) which uses a cassette (much like the ones used in conventional radiography) and a reader

http://idexx.com/view/xhtml/en_us/smallanimal/inhouse/digital/cr-1417.jsf?selectedTab=Images

The cassette contains a phosphor plate which stores energy that is produced when tiny crystals interact with xray beam. the reader causes this energy to be released and then converted into an electrical signal which is in turn used to produce a digital image. the reader then erases the plate so that it can be reinserted into the plate read for use again.This process is all automatic although some systems are available where the phosphor plate to be manually removed from the plate and inserted into the machine. This can be done in subdued lighting. Although exposure to bright light can cause the latent image to fade and be removed from the phosphor plate.

DDR (Direct Digital Radiography). In these kind of systems there are no actual plates, but a detector plate which an xray beam is fired at through the area of interest and this captures the xray image. and almost instantly displays it on a computer screen. The computer screen and the detector plate are linked by a cable. In some systems the detector plate is built into the table. Although this has its limitations with regards to views that can be taken for example horizontal beams.

One of the main advantage of both these types of systems allows for manipulation of the images captured.

Application of filters to enhance the edges of structures, or alter the gray scale
Altering of contrast and brightness
Zoom into areas of interest
Orientation can be flipped and rotated
Altering contrast / brightness
Measurements can be taken from images

Images are stored as computer files, so require less spaces than traditional film packets require. Regular back-ups should be performed to prevent loss of images. An external hard drive can be used to do this.

ADVANTAGES:

Reducing running cost: No film or chemicals to purchase
Decreased radiation doses – digital systems can function equivalently to conventional systems with less radiation
No need for storage and disposal of processing chemicals, avoiding issues with health and safety, and hazardous waste disposal
Time saving: DR systems – Instant images
Reduced repeat rate
Improved images in some cases – bone/soft tissue detail
Easy image storage and retrieval
Space saving – no dark room needed, greatly reduced need for storage space
Easy communication of images for referral / 2nd opinion
Portable – instant images in ‘field’

DISADVANTAGES:

Set up costs can be substantial
Adapting to change: Viewing images – computer screen vs film
Use of computers by staff
Access to images limited by availability of computers – consulting rooms, theatre
Artefacts can be created eg lucency around screws
Ensuring adequate back-up of files