The discovery of X-rays was first reported at the end of 1895 when Wilhelm Conrad Rontgen 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.

Figure 1. The PimaxScan combines digital and analog circuitry to provide a robust imaging system for X-ray angiography.
Angiography is an x-ray-based medical image processing technique that shows soft tissues such as arteries, veins, and organs. During a procedure, a patient receives an injection of a radiocontrast agent, which is absorbed by the x-rays to highlight the vascular structures. The acquired image - the angiogram - also includes the surrounding structures such as bones and organs. 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 the bloodstream and shows other structures in the background with very low contrast. Thus, digital subtraction angiography is 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 UADE (Universidad Argentina de la Empresa). “They wanted to incorporate digital acquisition and processing modules to their machines,” he explained. “Because we used off-the-shelf components, we were able to bring an affordable product to the market within two years of its inception.”

Analog/Digital Hybrid

The PimaxScan is an analog/digital hybrid imaging 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. A module prints and stores the images.

“Adding the intensifier lets us convert an analog system to a digital one,” said Dr. Sentoni. “We used the existing analog circuitry to connect the new digital components.” He added that the cost of the hybrid system is on par with the original analog system, making digital medical equipment affordable 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,” he said.

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,” explained Dr. Sentoni. “We also used some LUTs to enhance the images for display on dual-screen terminals.”

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