You want a mobile C-arm that's easy to use, that provides high-quality images and that's versatile, according to a recent Outpatient Surgery Magazine survey. Here's what you need to know in order to understand and evaluate the many features that contribute to getting what you want when it comes to this piece of capital equipment.

Ease of use
A key consideration in any application of a C-arm is its ease of use, which takes into account the C's range of motion, the size of the C-arm, footprint size and maneuverability. Here's how each plays into your C-arm's usability.

• Range of motion. "The most important factor to us was the C-arm's ability to expose any patient at every angle," says one survey respondent. "The size of our patients varies, and the type of procedures our pain management physicians do continues to change."

This need can be met by looking at the C-arm's orbital rotation, which determines the anteroposterior (AP), lateral and orthogonal views that can be obtained. The greater the C-arm's AP depth, its immersion depth and the depth of the C-arm itself, the easier it is to position the patient and obtain multiple imaging projections from various angles. In spine surgery, for example, at least 45 degrees of overscan is required to produce the oblique images necessary. Higher degrees of overscan allow for imaging at varying projection angles without having to reposition the C-arm. Ease of orbital rotation is another key factor in spine surgery, because most procedures require constant adjustment between the AP and lateral views.

Something to look for during the pre-purchase trial: a little too much motion.

"Arm articulation would be an item I would look at more closely if I were buying again," says Lisa Evans, RN, BSN, CNOR, the director or Oak Park Surgery Center in Arroyo Grande, Calif. "The one we have is very difficult to get to stay at the position the surgeon sets it at. It tends to drift."

A motor-driven C-arm will let the surgeon more precisely control all C-arm movements and will help keep the C in place.

• C-arm size. As the number of overweight and obese patients being seen in outpatient surgery centers has increased, so has the need for bigger C-arms. When Darlene Johnson, the administrator at the Surgery Center of Cleveland in Cleveland, Tenn., was shopping for her facility's machine, the No. 1 need was "a big C in order to accommodate large patients."

The size of the C is determined by the dimensions of the free space (the distance from the X-ray tube to the image interface) and the dimensions of the immersion/throat depth (the distance from the free space's midpoint to the base of the C). These measures define the unit's working geometry, which is important when positioning the patient in the C-arm. The greater the depth of the C, the easier it is to obtain multiple image projections. The challenge is to provide large free space and large immersion depth in a small footprint.

Larger C size is especially important in pain management applications, for which you want to minimize patient movement.

"The size of the unit and the diameter of the C - in terms of how big a patient is - and how much that C-arm will actually move within the degree of rotation as well as how high and low in coordination with the table [are key considerations]," says Robert Estes, MSPT, the director of operations for diagnostic imaging and rehabilitation at Pinnacle III, a consulting group in Fort Collins, Colo.

• Footprint size and maneuverability. A C-arm's size determines your ability to fit it into the space in which you working; this is important for surgery taking place where are a lot of people are working in a tight area, and where the C-arm competes for space with a lot of other equipment. Orthopedic and pain management environments, for example, tend to be cramped, so a small footprint is necessary.

As one survey respondent put it: "I want the smallest there is on the market that can still be fully functional."

Smaller C-arms are also often lighter, which in turn makes the machine easier to maneuver around and between ORs.

"Our C-arm is too big to get through the doors of the OR the C-arm is relegated to," which creates scheduling restrictions, says one surgery center administrator who responded to our survey.

"A lot of times, it's the nursing staff moving the C-arm, administering it, while we're waiting for the radiology tech to get there," says Shannon Meier, executive director of the Indiana Surgery Center North in Indianapolis. "So we were sure to pick one that's easy to actually push around. Some can be pretty heavy."

Image quality
Most of the readers who responded to our survey named image quality as a top priority when buying a C-arm.

"We bought ours for its clear, crisp image," says one ASC manager.

That clear, crisp image is a function of the various components of the image chain; its overall quality relies on many features.

• Power boost. If you do a lot of procedures on overweight patients, look for a machine that will boost milliamperes (mA) to compensate for the difficulty of viewing dense anatomy.
• Automatic focus. Much like the feature on a camera that makes taking pictures one-click, some manufacturers offer a function on their C-arms that will sense the region of interest and adjust the image to maximize the quality of that part of the viewing area.
• Brightness control. This is especially important for orthopedic surgery, because so much metal hardware, instruments and implants are involved - all of which can cause the automatic brightness control to overpenetrate the desired anatomy. Image sensitivity to metal is critical, and the C-arm needs to differentiate between the density of the anatomy and objects. Automatic brightness control regulates the amount of X-ray needed to penetrate the object and produce a desirable image.
• Spatial resolution. This is the C-arm's ability to resolve two very close objects and enable the user to discern these two objects as separate entities. This feature is especially important in pain management, because you are primarily working with such small needles. Some image intensifiers feature metal shielding to protect against distortion. The C-arm can therefore deliver a high-quality image quickly while compensating for metal introduced to the field.
• X-ray generation. A tradeoff exists between the imaging quality and the dosage of radiation used; the higher the amount of radiation, the better the image. Look then for a C-arm that has incorporated lead, which will block shatter radiation, in its C-arm shutters. In addition, smaller C-arms produce less scatter radiation than larger ones. Regardless, manufacturers recommend wearing lead garments to protect against scatter radiation.

Versatility and connectivity
The ideal C-arm will also be able to handle several different specialties as well as be easy to wire into a facility's system, according to respondents to our survey. In short, it will be versatile. The two sides of the versatility coin are multi-functionality and connectivity.

• Multi-functionality. Survey respondents said they wanted to be able to do procedures as varied as vascular, spine, urology, pain management, podiatric and general surgery.

"We bought our C-arm because of this," says Christine A. Therrien, RN, the administrator at Brookside Surgery Center in Battle Creek, Mich. "You can do general cases such as port placement as well as ortho and hand cases."

Look for a system that lets you generate multiplanar reconstructions of bony anatomy within a one- or two-minute scan, providing the surgeon with an intraoperative update of the patient's anatomy. With this volumetric data set of the patient's anatomy during surgery, the physician can make any necessary adjustments before completing the procedure. A C-arm featuring an isocentric design keeps the anatomy within the C-arm's field of view throughout a wide range of projections angles without having to reposition the C-arm.

"You want to be able to get lots of views and angles," says Peter Stevens, MD, a professor of orthopedics at the University of Utah who handles mostly pediatric cases. "That ability will let you use the C-arm for a variety of specialties."

Also, an intuitive, easy-to-use user interface is beneficial, no matter what the application, and large, flat-panel monitors allow surgeons to view images easily from a distance and at various angles to the monitor display.

• Connectivity. The ability to upgrade software to adapt your C-arm to different procedures only increases its multi-functionality. And if you can interface with your image-guided surgery system, image-capture processes and other computer software, the machine will be more versatile across your practice, not just among specialties.

Look for a C-arm that is Dicom-compatible - this refers to a networking feature that allows the display of preoperative CTs and MRIs as well as other important patient data. The Dicom system also communicates the status of the procedure - such as, "in progress," "completed" or "cancelled" - which is useful for the OR scheduling center as well as for the billing and administrative departments.

The toppers
Price is of course a consideration, but you do have to pay to get the features you want, depending on your needs. Better to take into account are your break-even point, projected durability, and the service and warranty.

One ASC's director of nursing reported that, the next time she is in the market for a C-arm, she would be looking for "service, quality and reliability. Many purchases we have made through a sales rep - not just C-arms - are supposed to include service after the purchase. But once you sign the contract, it is difficult to arrange service or the service is not what was portrayed."

Another key, especially for large facilities, is standardization.

"Radiology and clinical engineering should always be included in the decisions," says Lynda Petty, the director of perioperative services at the Ohio State University Medical Center in Columbus, Ohio. "As we bring on additional surgeons, and as additional services request C-arm availability for their cases, our need of C-arms continues to grow. [Because of this,] standardization is key."