High-definition video's ability to capture and display more data than previous video technology lets practitioners in such image-driven fields as endoscopy, laparoscopy and minimally invasive surgery enjoy colossal improvements in the detail and clarity of their view of a surgical site. If you've not upgraded your ORs to HD yet, you've likely thought about it. But before you equip, how familiar are you with the technical details that make up a sharp image? Test your knowledge by answering the questions to the right, then read on to learn more.

The components of HD
If you're dipping a toe into the deep waters of high-definition technology, begin by familiarizing yourself with the components required to capture, carry and present HD images in your surgical suite: the source, the distribution and the destination.

The source is the camera where the image originates, whether it's mounted on the tip of an endoscope, the arm of a boom or the lights over the surgical site, as well as the camera control unit that processes the captured images. The distribution is the cabling and video router that channel the stream of images from the source to its eventual output. That output, the destination, most often means a display monitor over the surgical site or mounted on the OR wall, but can also include image recording devices and video printers.

To get the intended visual benefit, every component in this HD chain must be of high-definition quality, capable of transmitting and reproducing high-definition signals. A standard-definition camera can't produce high-definition images, even if its signals are sent to an HD monitor, and the quality of an HD camera's images will suffer if displayed on a standard definition monitor. An image's quality depends upon the quality of every component.

Another thing to remember: The terms HD and HDTV are not interchangeable, and the designation HD is limited in its ability to define the technical capabilities of video equipment.

"HDTV is a specific broadcast standard," says Nathan Pinkney, BS, senior project engineer at the ECRI Institute's Health Devices Group in Plymouth Meeting, Pa. Unless you're watching TV in your OR, it's not relevant to discussions of the surgical applications of video technology. "HD is a designation indicating any image resolution that's higher than standard definition," with standard definition being 480 vertical lines of pixels (picture elements, the tiny dots or squares that compose an electronically reproduced image) in an image. But those 2 letters don't tell you what that resolution is. "Vendors may market a camera as high-definition, but that's useless information. How many pixels does it capture? All they're telling me is that it's better than standard definition."

From the source
Those eye-popping, high-def images your surgeons see on flat-panel monitors at other facilities or in the exhibit halls originate from and are defined by the native resolution of the source camera's imaging circuitry. Native resolution simply means the best image resolution, as measured in pixels, that a camera can capture and transmit for reproduction. In terms of resolution, the following 3 signal formats are each considered high-definition video:

• 1080p, or an image composed of 1,920 pixels per vertical line and 1,080 vertical lines, progressively scanned (commonly noted as "1,920 x 1,080 progressive");
• 1080i, or 1,920 x 1,080 interlaced; and
• 720p, or 1,280 x 720 progressive.

Progressive and interlaced scanning define video reproduction's frame rate. In a progressively scanned image, every line of pixels captured is transmitted to the monitor's screen every time the image is refreshed. In an interlaced image, on the other hand, only alternating lines are displayed in each cycle, meaning that only half of the image is on screen at any given time. The appearance of a whole image relies on the persistence of vision. For its high image resolution and complete scanning, the 1080p format is often described in equipment marketing as "true HD" or "full HD."

The camera captures its images by way of a light-sensitive semiconductor chip or chips, which measure the amounts of red, green and blue light — the primary colors of video imaging — that are given off by an illuminated subject. The resulting signal defines the amount of color to be represented in each pixel of each frame of an electronically reproduced video image. Camera buyers have 2 options here: In a single-chip camera, 1 chip manages all of the colors, but in a 3-chip camera, a separate chip measures each color.

The advantages of the 3-chip camera include a more precise color reproduction and a higher refresh rate, says Mr. Pinkney. "A chip configured to pick up all the different colors limits how quickly the camera is able to capture the image," he says. While a single chip must be scanned 3 times consecutively to transmit the image's colors, a 3-chip camera's chips are scanned once each simultaneously to produce the same image.

For the better part of the past 2 decades, the chips in question have been image sensors known as charge-coupled devices (CCDs), which have been standard in cameras. In recent years, however, the development of complementary metal oxide semiconductors (CMOSs) has begun to provide manufacturers with another option, even as most still employ CCDs. "The jury's still out on whether there's going to be any medical significance to CCD versus CMOS," says Mr. Pinkney. While CMOS is seen to offer some improvements in image quality, he says, it still shows a small amount of noise, or visible distortion, in the image.

Channeling the signal
Once a camera system acquires and processes an image, it is distributed to display monitors or other output devices by a network made up of cabling and a video router, a device used to select and direct sources and destinations.

In the computer and medical industry, digital visual interface, or DVI, and high-definition serial digital interface, or HD-SDI, are the standard modes of video data transmission. Both use high-quality coaxial cabling to enable high-speed connections between devices, and both carry video only. Any audio to be recorded or transmitted, such as documentation or communication with off-site viewers, must be carried through a separate channel. Many manufacturers have begun offering connections for both DVI and HD-SDI on their video equipment.

Another interface standard often encountered in HD marketing is high-definition multimedia interface, or HDMI. HDMI supports both video and audio, but it is more likely to be employed by mainstream consumer goods such as television sets and DVD players, and is not often seen in medical applications.

The main difference between the DVI and HD-SDI interfaces is the distances they can reliably transmit data, says Mr. Pinkney. While DVI cables can carry standard definition video signals about 180 feet, they can only carry high-definition video 15 feet at maximum before their multiple parallel signals degrade. HD-SDI cables, on the other hand, can send their serial high-definition signals 300 feet.

The signal loss experienced by DVI cables can be avoided by converting a camera's digital signal into an enhanced optical signal for longer-distance transmissions. Let's say your output device is further than 15 feet away: a monitor in a conference room, perhaps, or a server recording a procedure from an IT closet down the hall. In that case, Mr. Pinkney explains, a fiber optic transceiver pair can handle the conversion. One of the transceivers will convert the digital video signal, which has emerged from the camera control unit through the DVI output, into a signal made of light. The light is sent through a fiber optic cable, which can reliably transmit data long distances, until it reaches another transceiver. The second transceiver converts the light signal back into a digital one, and it reaches the destination device through its DVI input connection. It's an expensive option, though, he says, with each transceiver costing about $800.

The big picture
The most common, and the most visible, destination device for surgical video is a display monitor. Most, if not all, high-definition quality monitors presently available are flat-panel models, ideal for boom- or wall-mounting.

In addition to confirming that a monitor's resolution meets the native resolution of the source camera, for the faithful reproduction of captured images, potential HD system purchasers should consider the aspect ratio in which the monitor presents its images in relation to the sources that produce those images.

Those eye-popping, high-def images your surgeons see on flat-panel monitors originate from and are defined by the native resolution of the source camera's imaging circuitry.

The aspect ratio of an image is the ratio of its width to its height. The two most common aspect ratios for video are 4:3, a squarer image familiar to any TV viewer, and 16:9, a longer rectangle which accommodates a widescreen image. In the consumer electronics industry, the 16:9 aspect ratio has been adopted for most high-definition uses, but its elongated view slices the top and bottom from the circular view produced by endoscopic cameras, for instance, whose images may be better served by high definition in 4:3.

Mr. Pinkney warns potential buyers to be wary of the marketing surrounding display monitors, and particularly to seek out a product's specifications (such as "1,920 x 1,080 progressive") over descriptions (such as "full HD"). He cites some vendors' previously common practice of marketing monitors as 1080i when they were actually 720p with a resolution boost. "It can seem to be a numbers game, and a lot of people are buying on numbers," he says, "which is OK, as long as you understand the numbers in the specifications."

"You have to be careful about what you purchase," says Jeff Looney, communications group manager for equipment planning firm Gene Burton & Associates in Franklin, Tenn. "Drill down to the specifics and compare them from manufacturer to manufacturer. With a sheet of technical details from each, you can do a side-by-side comparison."

The terms "medical grade" or "hospital grade," when applied to display monitors, refer only to their having met safety requirements for operation in a surgical field. They have no bearing on image quality, especially since there is no HD standard for medical video the way there is for commercial broadcasts.

An impact on outcomes?
Recent estimates have put the cost of installing a high-def system in your surgical suite at $25,000 to $50,000, and as the components fall in price, says Mr. Looney, you can expect to see HD in more and more facilities.

But will that investment pay off? It depends on what you're measuring, says Martin A. Martino, MD, FACOG, director of robotics and minimally invasive surgery in gynecologic oncology at the Lehigh Valley Health Network in Allentown, Pa. "It's going to be hard to provide studies showing it makes a difference, to put a value identifier on it," he says. "There is a difference, but one that's too small to identify in a clinical study."

While published studies have noted the higher image resolution that HD brings to a case, its assistance in laparoscopic knot-tying, and its potential to improve anatomical identification, tissue dissection and 3-dimensional spatial positioning in laparoscopy, there has been no clinically proven consensus that it affects surgical outcomes. Still, Dr. Martino says, "if you're going to have surgery, you want your doctor to be able to see clearly, with the most advanced visual systems."

Even if clinical outcomes don't differ from standard to high def, he adds, the sharper pictures may bring more to the minimally invasive table. "It will give surgeons greater confidence in identifying surgical anatomy and let them bring things that were open procedures to minimally invasive surgery," says Dr. Martino. "If you can now see things the same way [as in open procedures], you can probably do the same things."

Answers: 1:b; 2:c; 3:a; 4:b; 5:b; 6:b; 7:b