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Feature Articles

Vision Technologies Improve Medical X-ray, OCT, and Hyperspectral Systems

by Winn Hardin, Contributing Editor - AIA

Growing demand for medical services around the world is pushing technologists to develop better preventive, diagnostic, and minimally invasive treatments to better serve an aging population and help governments manage costs.

Mobile C-arm systems are one example. A mobile C-arm is a medical imaging device that is based on X-ray technology and can be used flexibly in various operating rooms. The name is derived from the Vision Technologies Improve Medical X-ray, OCT, and Hyperspectral SystemsC-shaped arm used to connect the X-ray source and X-ray detector to one another. The unit can be moved to the patient rather than bringing the patient to the X-ray machine and provides real-time guidance for surgeries and/or radiation treatment for cancer, among other applications.

Taking X-ray on the Road

X-ray mobile C-arms traditionally use image intensifier (vacuum tube) -based X-ray detectors due to their low-dose detection capability. However, with recent advancements in CMOS flat-panel detector technology, C-arm image quality and system robustness can be dramatically improved while maintaining the low-dose capability of image intensifiers.

Due to portability, form factor, budget, and operating room infrastructure, mobile C-arm systems can rarely afford the benefit of liquid cooling subsystems. This results in a twofold problem: first, the x-ray sources cannot be cooled, challenging the detector because the amount of X-ray dose is quite limited. Second, the detector itself cannot be cooled, which makes it a tough environment for older amorphous silicon flat-panel detectors that need cooling to manage undesirable dark current and noise levels. This combination of lower dose and the absence of cooling makes it hard to detect single X-ray photons per image in these traditional image intensifiers.

“With their single X-ray photon detection capability, image intensifiers have sustained a low-dose advantage for several decades,” explains Bryan Delodder, director of life sciences at Teledyne DALSA Teledyne DALSA Xineos X-ray detectors are a standard area scan CMOS flat detector panel.(Waterloo, Ontario, Canada). “CMOS flat-panel detectors, rather than amorphous silicon flat-panel detectors, will eventually replace image intensifiers in these applications because of their robustness and low-dose performance. CMOS flat-panel detectors also offer significantly better linearity, dynamic range, and sharpness, enabling surgeons and radiologists to see more than ever before.”

X-ray imaging performance is measured by the industry standards for Detective Quantum Efficiency (or DQE, as defined by IEC 62220-1). DQE is a detector’s photon detection capability expressed as a percentage when compared to the theoretical maximum. Detector entrance doses between 1 and 0.1 microR, which are needed in many low-power C-arm systems, will measure higher than 60% in many traditional image intensifier–based systems. In low-dose conditions Teledyne DALSA’s Xineos flat panels deliver greater than 70%, while amorphous silicon flat-panel detectors can drop below 20%, Delodder adds.

But when cost is an issue, as it is for X-ray systems sold into emerging BRIC markets, image intensifiers still have legs, says both Delodder and Adimec’s (Eindhoven, the Netherlands) strategic marketing manager Marcel Dijkema. “The image intensifier offers excellent quality and is the preferred solution when price pressure is a major consideration,” says Dijkema.

In the future, C-arm systems may also move from Camera Link and other proprietary interfaces to CoaXPress (CXP), and not just because CXP is a high-speed data interface. “Medical X-ray systems tend not to operate at high frame rates so they may not need CXP frame grabbers, but the smaller, rugged CXP cables offer benefits to mobile C-arm systems,” says Donal Waide, director of sales at BitFlow Inc. (Woburn, Massachusetts). “CT, MRI, and high-speed automated microscopy systems for tissue screening are also looking at CXP due to both cabling and high-speed data transfer requirements.”

While X-ray and CT system designers have looked at Gigabit Ethernet (GigE) as a low-cost data interface alternative, this interface is too slow and the systems still need sensor-control capabilities found in frame grabbers.

New OCT Sensor Could Change Cancer Treatment

This fall in Stuttgart, Germany at VISION 2014, Adimec together with LLTECH (France) and CMOSIS (Belgium), will talk more about a new Full-Field Optical Coherence Tomography (FFOCT) system under development that will allow physicians to use endoscopic probes to detect cancer cells in-vivo in real time.

Developed with funding from the European Union Seventh Framework Program, the device features imaging technology developed in cooperation by Adimec, CMOSIS, and LLTECH. The handheld endoscope integrates the optical probe, FFOCT engine, and camera with a new application-specific sensor.

The sensor, engineered by CMOSIS and developed into a camera by Adimec, offers a high full well that can hold more electrons per pixel than a normal camera. OCT systems are basically interferometers that use bright, broadband, and/or infrared light sources to image internal structures in a few millimeters of tissue. The image is created by measuring minute differences between a reference beam path and the probe beam, hence the need for a sensor that can hold high numbers of electrons without saturation.

“Application of the FFOCT through endoscopy will drive early recognition and improved surgery of cancerous tissue in the operating room,” says Adimec’s Dijkema. “The new tool aims to significantly increase the certainty for correct tissue biopsy and improve the surgeon’s ability to determine the margins of cancerous tissue in situ. For patients this means a less stressful experience and an improved diagnostics process. Typically up to 30% of biopsies need to be redone today, depending on the tissue type, as the removed tissue does not provide representative samples for diagnosis. During surgery, the certainty of removing the cancer will be improved.”

Medical imaging systems represent one of the most powerful tools at a physician’s disposal for early detection and prevention of disease. By developing sensors and interfaces tailored to the specific needs of medical imaging systems, machine vision is doing its part to keep a growing global population healthy.

 

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