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Feature Articles

Machine Vision Brings Advanced Medical Technology to Life

by Winn Hardin, Contributing Editor - AIA

 

Machine vision opportunities in the medical field have traditionally come from packaging applications: blister packs, thermally-sealed sterile plastic packages, vial inspection, etc. But as the variety of medical tools and procedures increases -- driven by an aging global population, the growing success of genomics and proteomics, and a need to reduce medical costs while improving the level of medical care – machine vision is moving deeper into medical applications.

Today, machine vision is being used more in R&D, as a diagnostic tool (e.g., digital radiography, and blood/drug screening), as well as a quality inspection tool for medical manufacturing of advanced devices from catheter tubing to complex biochips for point-of-care testing.

Bringing the Lab to You
While packaging applications for everything from barcodes to blister packs remain the largest medical applications for machine vision, specialists are moving beyond traditional applications into new horizons of medical care.

Machine vision integrator moviMED (Irvine, California) is bringing machine vision to the medical industry.  ‘‘One active new application for us is the inspection of biochips,’‘ explains Markus Tarin, President and CEO of moviMED. ‘‘Biochips are used for point-of-care testing, often for testing blood using chemical reagents, to look for everything from diseases to genetic anomalies.’‘
 
Biochips combine both electronics and micro-fluidics. Using various electric or mechanical means, biochips guide, mix and pump fluids on the order of pico- and nano-liters for mixing with chemical reagents. Then, the result is placed in a machine, optically excited, and a return fluorescent signal yields the result. Biochips can perform many of the same screening and blood tests typically done by labs, but without the wait and cost of sending the samples to a  separate location. Using semiconductor technologies to miniaturize the biochips greatly reduces the cost of each test and allows for large arrays to be created for batch testing common to pharmaceutical drug discovery. The combination of small devices and high-volumes means that machine vision systems have to be able to resolve features on the micrometer scale, but often across fields of view measuring several centimeters.

Digital X-Rays: A Glowing Opportunity

Digital radiography, or x-rays without the film, has been a technology on the cusp of major commercial realization for almost 20 years. That may seem like a long time, but like many good ideas, the consumer (e.g. the medical community) simply was not prepared. Just 10 years ago, few hospitals had Picture Archiving and Communication Systems (PACS) – high bandwidth data networks necessary to store, transmit and display digital x-rays. More to the point, radiologists were both unfamiliar with the technology and concerned about the accuracy of digital images, particularly the possibility for computer-based artifacts.

Fast forward to 2008, and much has changed. Infrastructures are in place. Radiologists are more familiar with digital technologies, and more to the point, digital x-ray systems are saving hospitals money, a huge benefit as most medical costs continue to escalate. According to experts, digital radiography rooms can process between 5 and 7 times the number of images as traditional film-based x-rays. They also don’t require film, processing and associated environmental and labor costs.

But hurdles still remain. Consumers have several choices when it comes to digital radiography, according to Marcel Dijkema, System Architect and Marketing Specialist for Adimec Advanced Image Systems bv ( Eindhoven, Netherlands ). “Until the 1990s, all x-ray systems were tube and film based. Adimec has been providing CCD based cameras for medical X-ray since the end of the 1990s. Based on the newest CCD technology, Adimec is now lauching a new generation of camera-lens-assemblies, offering versatile and integral cost-effective solutions for x-ray imaging OEM’s,” notes Dijkema.

Under this technology, x-rays pass through the patient, and those rays that are not absorbed strike an image intensifier, which converts them to visible light. The CCD then collects the light projected from the image intensifier/phosphor screen.

Newer technologies include large-area amorphous silicon and selenium flat panel detectors (FPD), as well as large phosphor screens combined with megapixel CCD or CMOS sensors. Selenium interacts directly with x-ray radiation, converting x-ray radiation to an electrical signal, while silicon uses a phosphor scintillator screen to convert the x-ray energy to visible light. FPDs come in both static and dynamic varities for taking snapshots or x-rays at video frame rates. These technologies are quickly reaching maturity and offer the potential for higher-quality images; however, low volumes common to new technologies translate to higher purchase prices. Phosphors with megapixel sensors, or direct digital radiography (DDR) offer high resolution and relatively inexpensive price tags, but cannot generate fast frame rate images as can image intensifier/CCD modules, and dynamic FPDs.

‘‘We have developed machine vision for several steps in the production of biochips, including a robotic gantry system for inspecting 50 biochips at a time,’‘ says moviMED’s Tarin. ‘‘As part of that project, machine vision technology locates fiducial marks on the biochips and tells the specialized dispenser– similar to an ink jet printer -- where to dispense chemical reagents on the biochip. After they’re dispensed and the curing process begins, we use machine vision to make sure the required properties are being met, such as where the center of mass for the chemical agent is with respect to the fiducial mark, and the size and shape of the chemical sample. Today, our inspection systems quality check two to three million biochips per year.’‘

moviMED, which also regularly combines motion control and other automation systems with machine vision to solve medical applications, is also helping to qualify porcine tissue for use in human heart valve replacement surgery. ‘‘We developed a four-axis motion control system to stretch the valve tissue, and a machine vision to measure the elasticity of the tissue over time. Certain parts of the pig valves are more resilient than others. This system is now moving out of R&D and into production.’‘

One of the most unique applications moviMED has developed relates to tracking digital magnetic beads. In this case, Maxwell Sensors, Inc. (Santa Fe Springs, California) has developed a process for manufacturing micro-beads 100 to 300µm long. Each bead is printed with a unique identifier and carries a fluorophore -- a molecule that emits light when energized through some chemical, mechanical or electrical means. Maxwell Sensors designed the microbeads to work in high-volume, rapid drug discovery, medical screening, or biochemical sensing for military and related applications. In theory, many of the microbeads, each with a different chemical fluorophore or sensor, would interact with an unknown sample under test. This meant that the group needed an imaging system that could detect an individual fluorescent signal from a micro-bead as it travels through a micro-fluidic channel while also reading the unique identifier on the micro-bead.

‘‘It hasn’t been easy, but we’ve developed a conceptual prototype capable of reading 3000 micro-beads per second in a micro-fluidic channel,’‘ explains moviMED’s Tarin. As more nanotechnology is used for drug delivery and fighting disease, machine vision’s unique ability to see what humans cannot, and at speeds we could never achieve, will help the world to be a safer – and healthier – place.

 

 

 

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