What's on your plate?
MIL and Meteor-II used to develop new imaging system for rapid reading and diagnosis of specimen plates
To facilitate the reading and diagnosis of microbiological specimen plates, a UK-based company has developed a new imaging system using Matrox Imaging Library (MIL) software and the Meteor-II PCI frame grabber.
For over 30 years, MAST has developed and marketed consumables and instrumentation for microbiology. The company, with over 70 distributors world-wide, now employs about 200 people at its Liverpool, UK manufacturing site and other locations in France, Germany and South Africa.
MAST originally began working on imaging systems for plate reading back in 1983, which culminated in 1997 with the development of the 'mastascanelite' - a complete, computer-driven system for rapid reading and diagnosis of standardized specimen plates.
mastascanelite consists of three software modules for carrying out different types of diagnostic tests. In the classic disc diffusion test, nutrient agar (gel) is inoculated with an organism isolated from a patient sample. Antibiotic discs are then placed on the nutrient surface to diffuse their contents into the gel. Each antibiotic will kill the organism within a certain radius from the centre of the disc. By measuring the diameter of the antibiotic spread on a look-up table, it can be determined which drug will best treat the infection.
A view of the threshold look-up tables for calculating the susceptibility of an individual antibiotic for an individual/group of organisms.
Millimetric measurement (combined with trend analysis) is also used to determine whether an organism is moving from a 'Sensitive' status to 'Intermediate' or even 'Resistant' (SIR) - which is increasingly becoming a problem with the rise of so-called 'superbugs' that develop a resistance to antibiotics on the market.
With most labs receiving 50-200 specimen plates per day, speedy measurement and analysis of these plates is critical. Where it would take two people spending hours to go through a batch of plates in a lab, a system like mastascanelite can take 60 readings of each disc on a plate (a maximum of 25 discs per plate) in less than a second. In addition, the speed at which these plates are read can be further enhanced by the connection of multiple systems to a mainframe computer.
Enter MIL
The entire MAST application is written in Visual Basic and makes comprehensive use of Matrox Imaging Library (MIL). The program directs the machine to locate the exact centre of the discs on each plate, reading around the zone edge 60 times. The result of each scan is color-coded on screen - red is resistant, blue is intermediate and green is sensitive. The program then calculates and displays the millimetric dimensions of the antibiotic effectiveness and delivers the interpretation.
An image of a test plate that has been read.
The control, image capture and processing functions of this system are based on a Dell PC, running Windows '95 - to ensure consistent quality and reliability - while the standard camera used is a monochrome PAL composite analog unit.
Observing mastascanelite at work, discs where the bacterial or viral spread is barely visible to the naked eye become crystal clear when viewed on screen. This is made possible by specially developed image enhancement in the capture and processing of each disc. The functionality of the application is a result of the close interaction between the hardware and software.
According to Simon Snowden, Instruments Manager at MAST, it was the existence of MIL that determined Matrox as the chosen supplier of image capture boards for MAST. Boards that MAST had used previously came with very limited imaging capability, which meant that MAST had to build all the required functionality in-house - a very labor-intensive process.
MIL's ability to do thresholds, binarize images, carry out convolutions and histogram equalizations, plus a multitude of other functions, gave the MAST development team the freedom to try out a much wider variety of system solutions than otherwise possible. Using prototyping software such as Matrox Inspector to build up scripts, potential solutions could be tested very rapidly and then just as rapidly built into the mastascanelite software from the scripting process.
Meteor-II transition
The mastascanelite system is based on a Matrox Meteor-II capture board, to which the team was able to port much of the development work previously carried out on a Matrox Meteor. This in itself was a considerable improvement on MAST's previous development experience, when another supplier's board became obsolete and necessitated extensive re-coding for its replacement.
"It was brilliant - all the code we were working with on the Matrox Meteor was immediately usable on Meteor-II," says Snowden. "It has removed all our worries about board obsolescence at a stroke. Choosing a company that could provide both the hardware and the software development toolbox was a key criterion in selecting Matrox and our experience has been that this was exactly the right thing to do."
The mastascanelite.
Another test performed by mastascanelite is the multipoint test, which puts a different spin on the standard disc diffusion test - instead of a single isolate being tested with multiple antibiotics, a single antibiotic in the growth medium itself is tested with multiple isolates. So bulk sensitivity testing, such as urine tests, becomes very cost-effective. Multipoint testing also allows isolate identification, based on color analysis. The sugar-based growth medium contains a pH indicator so that when the organism consumes the sugar, its excretion will change the pH balance and thus the indicated colour. A color camera is therefore used in this application.
"Where we benefit greatly from Matrox in this area is in the use of different color domains, which means we can use HSI instead of being limited to RGB, so that changes can be measured by intensity as well as color and can then be interpreted by binary code. Then, a few more simple calculations enable us to work out what the organism actually is," says Snowden.
Data gathered from the mastascanelite is sent to a database that utilizes the JET engine, as does Microsoft Access, so compatibility with MS Office - in widespread use in many labs - is guaranteed. Analysis and reporting via MS Access is therefore completely straightforward. The mastascanelite software also enables management to log who has been operating the system and what consumables have been used. mastascan elite also provides extensive security protection to ensure that each user must log in and can only access necessary features to a specific security level.
Looking to the future, Snowden envisages that the system will be able to alert doctors by pager or email when specific pre-set conditions arise, so that they can take prompt action. Expanding into expert systems technology means that the system will also be able to detect anomalies and alert users to them. Further automation could also mean that plates would be loaded and read in stacks unattended, but with each scanned image being saved for later inspection when convenient. The possibilities are endless!
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