The Analog-Digital Bridge
Matrox Imaging components upgrade analog X-ray equipment
The discovery of 'X-rays' was first reported at the end of 1895 when Wilhelm Conrad Röntgen was conducting experiments with electrostatic charges and cathode ray tubes. In 2008 we have such medical imaging technology as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission topography (PET), it might sound as though X-rays are antiquated. But they're not.
Angiography is an X-ray-based medical image processing technique that shows soft tissues such arteries, veins, and organs. During a procedure, a patient receives an injection of a radiocontrast agent that is absorbed by the X-rays to highlight the vascular structures. The acquired image, the angiogram, however, also includes the surrounding structures such as bones and organs, as well. For doctors who need to see a patient's blood vessels, bones and organs can obstruct the physician's view.
An imaging method called digital subtraction angiography removes the undesirable structures. With digital subtraction angiography, the technician first acquires an image without the contrast agent in the patient's bloodstream, then subtracts it from the image with the contrast agent. The resulting image highlights blood stream and shows other structures in the background with very low contrast. Digital subtraction angiography, then, is very useful for diagnosing conditions such as arterial and venous occlusions, and cerebral aneurysms.
A medical equipment manufacturer in Argentina wanted to add value to their existing X-ray angiography systems and contacted Dr. Guillermo Sentoni of the UADE, Universidad Argentina de la Empresa. "They wanted to incorporate digital acquisition and processing modules to their machines," he explains. "Because we used off-the-shelf components, we were able to bring an affordable product to the market within two years of its inception."
The PimaxScan is an analog/digital hybrid system. The analog radiology module produces the X-ray image which is then rendered visible to the eye with an intensifier. The visible 'X-ray' image is then captured by a high-resolution digital camera and transferred to the image processing module where it can be processed with software. Finally, there is a module to control printing and storing the images. "Adding the intensifier lets us convert an analog system to a digital one," says Sentoni, "We used the existing analog circuitry to connect the new digital components." He continues to say that the cost of the hybrid system is on par with the original analog system, making digital medical equipment an affordable option for developing countries. "If existing medical equipment can be retro-fitted with new components, developing countries will be able to offer the latest technologies to patients."
The digital components of PimaxScan include a Uniqvision UP930 Camera Link camera, a Matrox Helios XCL frame grabber, and an embedded PC fitted with an Intel 915-based motherboard and an Intel Pentium 4 processor. The system runs Windows XP Embedded. All the software was designed in C++ and built with the Matrox Imaging Library (MIL). Not only does the software control image acquisition, display and archiving, but the image processing as well. "MIL provides all the algorithms and functions for processing. In particular we used the Edge Finder module for border detection, as well as Low-pass filters, recursive filters, rotations, and digital subtraction," explains Sentoni. "We also used some LUTs to enhance the images for display on dual-screen terminals."
Overcoming the obstacles of compression
The greatest challenge for Sentoni was to find affordable components that could support the bandwidth without compressing the data. In Argentina and elsewhere, medical regulators prohibit image compression because of the potential for losing vital image data. "The core of the system acquires, processes, stores and displays 1024 x 1024 images at 30 fps. That generates 300 Mbps of information, which uses a good deal of the practical available PCI bandwidth," he says. "Our intention was to develop an affordable medical device, and that could only be fulfilled with off-the-shelf hardware." But not all hardware combinations were equal. Indeed, Dr. Sentoni discovered that visualization, an essential feature of a medical imaging systems, could only be achieved with the 915-based motherboard and Pentium 4 chipset.
Dr. Sentoni credits much of the work to his former student who implemented the design under Sentoni's guidance. Leonardo Seminara took on the project as an undergraduate and started his own company, Xineus Technology, after graduation. Today Xineus is responsible for the PimaxScan product and the fifteen systems deployed in Argentine hospitals and health-care facilities such as diagnostic clinics. The manufacturer also plans to export the system to other Latin American countries as soon as those health authorities determine that PimaxScan complies with their regulations. Sentoni's team is also developing additional functionality to help doctors diagnose, as well as adapt the current technology to the ecography market.
Compared to competition, PimaxScan is a high-quality, very-low cost diagnostic tool, thanks to the embedded PC and off-the-shelf hardware. "This also makes the system maintenance and upgrading easier," notes Sentoni.
Dr. Sentoni believes that Matrox Imaging's hardware and software products played a key role in the project's success. "The handy MIL API and the fabulous software-hardware integration with the Matrox [Helios] could be easily integrated with other components. Those were the main reasons to choose Matrox products." Once development began, Sentoni realized the combination of an easy-to-use API, the simplicity of integrating the hardware components, and "outstanding customer support" proved they made the right choice.