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Getting a Clear Picture of HDTV
High-def technology's impact on surgery could be revolutionary.
Dianne Taylor
Publish Date: October 10, 2007   |  Tags:   Surgical Video and Imaging

Your surgeons may have watched the Super Bowl on high-definition TVs at home and, come Monday, performed endoscopic procedures with standard-definition imaging systems that aren't nearly as clear. The reason is that the entertainment industry drives imaging technology and the medical market plays catch-up only after the new technology becomes mainstream. We're now catching up, and it won't be long before you're operating with high-definition video - regardless of whether you think the clinical benefits are worth the extra 30 to 50 percent (or more) you'll have to pay. Here's a guide to understanding where we stand and some of the differences between HD imaging systems, based on our interviews with manufacturers.

What is HD?
The industry buzz is that HD is the biggest technological advance since TV went color.

"Until now, we haven't made huge leaps inside the OR," says Evan Krachman, marketing manager for surgery with Sony Medical in Park Ridge, N.J. "But HD is a huge leap."

HD is all about picture clarity. HD endoscopy is still largely in its first generation, but it will be like "looking through a plate-glass window" when it hits its peak, says David Kurowski, product manager for video integration with Richard Wolf Medical Instruments Corporation in Vernon Hills, Ill.

HD can mean different things to different people, so it will help to understand the basics before buying. The main feature that makes HD systems better than standard-definition systems is the ability to capture and display more imaging data, enabling much more detail and clarity than before. While this is due to upgrades in the entire imaging chain, the systems' high-capacity semiconductor chips and high-resolution video screens are key components.

  • High-capacity chips. All modern SD endoscopy systems capture images on light-sensitive semiconductor chips known as charged couple devices, or CCDs, inside the camera head. CCD chips contain an array of photo cells, which convert light into electrical charges that vary in frequency or amplitude depending on the characteristics of the light - like brightness and color. These charges are converted to voltages, which then travel in a continuously varying electrical waveform, or analog signal, to the picture tube, which translates them into many tiny dots of light, each with a specific color and brightness, on the video screen. From a distance, these pixels create a complete picture.

Newer, digital systems convert the analog signal into a series of binary digital bits, or groupings of 0s and 1s, before sending the signal to the video screen. The primary advantage of this analog-to-digital conversion is that these bits are stable and can recombine on the video screen to create an exact replica, whereas analog signals are prone to interference, artifacts and distortion. The newest HD systems go a step further: They combine higher-capacity semiconductor chips that capture a lot more data - thus producing more pixels - with the benefit of digital output, resulting in a more reliable picture with significantly greater detail and clarity.

  • High-resolution video screens. HD pixels are smaller and squarer than SD pixels, so they're sharper and you can stuff a lot more of them onto the screen. HD video screens have four times the resolution of standard SD screens, allowing them to show all of the fine detail that the high-capacity chips can deliver. "Like a pointillist painting, the image is clearer when you have more dots per area," says Tony Krizan with Olympus Surgical & Industrial America, Inc., in Orangeburg, N.Y. "You can stand closer to it and still see the overall image with clarity."

Beyond White Light

Thanks to advances in digital imaging technology, endoscopy systems will offer more capabilities than ever before. One capability that has already come to fruition is the ability to more clearly differentiate various types of tissues using blue and green wavelengths of light. The primary benefit is that abnormalities are easier to see and remove, according to industry reps.

"Under blue light, you can see things that are not visible under white light, like precancerous lesions of the bladder," explains Thomas Prescher, PhD, director of marketing for gynecology/video imaging at Karl Storz Endoscopy in Culver City, Calif. "This allows surgeons to see how big the lesions are and to know exactly where to cut to better ensure removal of the whole abnormality." According to Dr. Prescher, this technology also lets surgeons see into organs from the outside.

The reason, explains Tony Krizan with Orangeburg, N.Y.-based Olympus Surgical & Industrial America, Inc., is that different colors of light penetrate different types of tissue at different depths, resulting in visual tissue differentiation. "With traditional endoscopy, everything looks pink. You're seeing all colors," he says. "But narrow bands of blue and green don't penetrate tissue as deeply as warmer colors, so you can see surface structures like polyps, tumors and their edges more clearly and without dye." In addition, says Mr. Krizan, color imaging lets surgeons see patterns within the lesions and stage them, in part because the wavelengths offer a strong contrast ratio with hemoglobin. Olympus offers its Narrow Band Imaging technology for colonoscopy, bronchoscopy and ENT applications.

Manufacturers say this capability can improve accuracy. "The way of the future is to look beyond white light," says Dr. Prescher. "This improves both diagnosis and treatment."

- Dianne Taylor

Sure, but where's the clinical benefit?
The benefits of HD are hard to quantify in terms of clinical outcomes, but industry reps liken it to the digital camera most of us have at home. "Would you ever go back to film?" they ask.

"You can see more. You can see sutures better. You can tie better knots. And you can simply do better surgery," says Kevin Geraghty, product manager with Stryker Endoscopy in San Jose, Calif.

Others say that true HD also offers better depth perception. "HD breaks the boundaries of our old imaging standards by increasing the native amount of resolution to a substantially higher level in a digital manner, providing much more image detail, sharpness and depth," says Johan Stockman, director of PACS/medical imaging product management for Barco in Belgium. "Increased image depth, which gives you almost a 3-D feeling, is one of the remarkable improvements of HD imaging. This amount of increased image sensitivity, accuracy and stability is of central benefit to image-driven procedures like minimally invasive surgery. It's also very advantageous for post-surgery training purposes." And because of HD's clarity, adds Mr. Krizan, you can also bring the monitors nearer to the sterile field and work closer to them.

What you need to know
Endoscopy systems are driven by technology and components produced in the consumer world. When the consumer industry stops producing components of SD imaging systems, they'll no longer be available to the medical industry. So, like it or not, HD is coming your way. Before you start looking at HD systems, however, consider these tips.

  • Maximize your pixels. Ask about the native resolution, or the number of pixels produced by the camera, not the screen. So-called upscalers inside the system's processor can convert an SD signal into an HD one by breaking it down into more pixels, giving the impression but not the true clarity of HD, says Mr. Krizan. For example, Stryker touts its newest HD camera as one that produces 1,280 x 1,024 pixels of "native output." Mr. Stockman agrees: "HD endoscopy can be found in ' camera chipsets that offer various resolutions. The user needs to compare apples to apples, and inquire about the native resolution."

Of course, resolution also matters when it comes to the video screen. Just as an SD resolution camera can't produce true HD images, an SD screen can't display an HD image. The system needs to be HD-compatible through and through. At least three different screen formats are considered HD.

"Sony makes a consumer TV that is considered HD, yet it offers nearly half a million fewer pixels than our monitor with higher resolution," explains Mr. Krachman. The three HD screen formats are 1080p (1,920 x 1,080 progressive), 1080i (1,920 x 1,080 interlaced) and 720p (1,280 x 720 progressive). The "1080" designation means that the monitor has 1,920 pixels per line and 1,080 lines of pixels in the entire image. The 1080 format is generally regarded as the best because it has a higher number of pixels. The real-life difference between 1080p and1080i, however, is less clear. In the consumer industry, gaming and video experts consider the progressive format, in which the system scans the whole image and refreshes the entire screen every sixtieth of a second, the gold standard. Interlaced systems, on the other hand, refresh every odd line of pixels first, then refresh every even line, and so on. With interlaced displays, the screen shows only one-half of the image every sixtieth of a second, and some contend this merging of images may be noticeable on large screens or under certain conditions, like when you're recording with a lot of movement.

  • Fit screen size to your needs and preferences. HD monitors come in different shapes, with manufacturers distinguishing them through the ratio of screen width to height, or aspect ratio (see "HD Screen Options"). Aspect ratios of HD screens include 16:9, 4:3 and 5:4. You may prefer one over the other because each displays the same image differently. The challenge manufacturers face is that these screens are driven by the consumer industry and are not exactly compatible with the circular image produced by the endoscope. So the squarer 4:3 and 5:4 screens, while smaller, can accommodate most of the circular image while the larger 16:9 screen crops more of the top and bottom of the image when you're using the full screen. To get around this, however, some manufacturers offer two different 16:9 screen formats.

Firms will tout the benefits of each approach, depending on which screen configuration they offer. Certain procedures necessitate a fuller image to ensure that instruments are always in view, like urology procedures during which the surgeon uses a cutting loop or bipolar laser, says Mr. Kurowski. Manufacturers who've chosen the 16:9 aspect ratio, like Karl Storz Endoscopy-America, Inc., say it offers the benefit of a wider lateral view. This, says Thomas Prescher, PhD, director of marketing for gynecology/video imaging for Karl Storz Endoscopy in Culver City, Calif., lets the surgeon see instruments coming in from the sides sooner. "This gives the surgeon a wider margin of safety, especially when the surgeon is using a smaller scope," says Dr. Prescher. Adds Mr. Stockman: "HD finds its benefit on larger screens. That's where you really see the difference, with the big images."

  • Be sure what you get is what you see. Don't presume that an HD video monitor or a system promoted as HD will always produce HD images. Image quality depends on the quality of the entire imaging chain - from native resolution and internal optic quality to data transmission, data processing and screen resolution. "You may have an HD video monitor in terms of lines of resolution," says Mr. Krachman, "but what you're actually seeing may be anybody's guess."

One major reason, say the manufacturers, is that there can be a break in the chain of communication from the camera to the screen, and this is often due to use of improper connectors and cables. Industry reps say they've seen OR personnel connect standard video cables into HD monitors and work all day under the impression they're seeing HD images when they're not. To ensure an unbroken chain of digital communication, you typically need "DVI" or "HD-SDI" cables, says Craig Lingel, director of North American sales with National Display Systems, a flat-panel technology firm based in Morgan Hill, Calif. Before long, HD cables and connectors will be standardized to one or the other, making things much easier in the OR, he says. Eventually, the "holy grail" of HD connectors will be the DVI, or digital video interface. Unfortun-ately, DVIs can only transmit digital data 10 to 15 feet, so those with boom systems will need to install fiber adapters that temporarily convert the digital signal to an optical one for transmission purposes - at a cost of several thousand dollars per system.

Another reason you may see "sub-HD" images on an HD system is poor optical output. "You can tell the differences in quality between one camera head and another, just like you can see differences among consumer cameras," says Mr. Krachman. Companies attempt to quantify quality by explaining the technological aspects of their systems they believe are superior. Many talk about the number and types of CCD chips in the camera. Karl Storz, Smith & Nephew and Stryker all use three chips inside their camera heads and claim this approach offers truer color reproduction because lenses inside the camera head split light into red, green and blue, and each chip is dedicated to capturing a different color. Chip size, they say, is also an indicator of output quality. "We use three 1/3-inch chips in our camera. A 1/4-inch CCD chip produces 350,000 pixels. A 1/3-inch chip produces 2 million pixels," adds Dr. Prescher. "This is the end of the line in terms of native resolution for endoscopy."

Mr. Krizan touts Olympus Surgical's single, distal-chip technology as superior. In its newest system, the tip of the scope itself houses a single CCD chip that processes the whole image. "The prisms inside the three-chip cameras that split the light into colors may start out producing better quality, but they can warp and shift with use, and image quality can degrade slowly over time," he says. "Our single, distal-chip technology is like having the camera inside the body without the prism lenses."

There is one thing on which industry reps agree. In the end, it's the picture that matters, and the only good way to evaluate any system is to try it out for yourself. "Take the same scope, the same light, the same cables, the same screen and two different camera systems and compare them to see which image you like better," says Stryker's Kevin Geraghty.