Continuing to cover the latest imaging technology for medical applications, this column will focus on the the use of USB 3.0 video interfaces for real-time medical imaging. Previous postings introduced vision standards and the deployment of GigE Vision-compliant video interfaces in the operating room.
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Thanks primarily to its ease of use, USB has become the backbone for wired data connectivity in a wide range of medical electronics devices. In particular, portable and home-based healthcare monitoring devices have benefited from the “plug-and-play” simplicity of USB connections.
One clear exception is medical imaging, where previous versions of USB failed to deliver the bandwidth required to support real-time image delivery. This began to change thanks to the raw speed offered by USB 3.0 and the development of USB3 Vision, a new standard designed specifically to regulate high-speed image transfer over USB 3.0 links.
Real-Time Image Transfer
As part of the continuing evolution toward home-based care, a growing number of USB-enabled medical devices allow patients to monitor and manage their own health and wellness. Personal or prescribed monitoring devices record and store data until they’re simply plugged into the USB port of a computer, where information can be displayed, analyzed, or transmitted to a healthcare provider.
For the majority of these applications, there’s no real-time requirement for data delivery. The few seconds its takes to transmit data from the device to a computer does not impact a patient’s ability to monitor their response to treatment.
However, the same is not true for advanced medical imaging systems, where high-resolution images must be transferred in real-time, and with low, consistent latency (or delay). A medical telepresence robot, for example, requires instantaneous transfer of imaging data from a camera to a processor to precisely navigate its environment. The visual, auditory, and tactical technologies must all work together at near-zero latency to reproduce a level of care for a remote patient that rivals an in-person visit. Similarly, microscopy and surgical applications requiring live analysis demand real-time visual data for display and analysis.
A key component to ensure instantaneous image transfer is the video interface--the hardware and software used to format image data and transmit it to a computer or display. In a previous posting, we provided an overview of video interface standards and how they relate to cost and performance trade-offs. In summary, video interfaces in medical imaging systems are often based on standards developed for other industries, such as LVDS, commonly used in telecom and consumer communications, HD-SDI from the broadcast industry, and Camera Link from the machine vision market.
All of these standards have significant downsides. They provide the bandwidth required for high-resolution sensors and fast frame rates, but the trade-off is complexity and cost. Each camera or sensor requires a PCIe or PC card frame grabber at the computing endpoint to capture data. This limits the types of computers that can be used, drives up component costs, and increases complexity. Moreover, all three require expensive or complex switching equipment to support video networking.
Alternatively, some manufacturers have chosen to design their own custom video interface. This approach has issues as well. Custom interfaces are often costly to develop and maintain, introduce integration challenges in multi-vendor systems, and can sidetrack internal R&D resources from more valuable core projects.
Recognizing these limitations, medical imaging system designers are increasingly adopting industry standards initially developed to support higher performance, more flexible, and less costly machine vision systems. Building on the concepts introduced with the widely adopted GigE Vision standard, in combination with the release of the “super speed” USB 3.0, USB3 Vision provides a framework for transmitting video and control data over more flexible USB cabling.