Often times when customers are shopping for C-arms they have many questions as to which one is right for them. This will be the first of a multi-part series  to answer these questions and more about surgical C-arms. With so many options and features, there is no one-size fits all C-arm. These posts will provide the fundamental knowledge required to optimize the use of C-arm imaging technology.  After reading them you will be able to make an informed decision on which C-arm best suits the needs of your business.

The Parts of a C-arm

Image Intensifier

The image intensifier is the primary component which separates C-arms from other radiation-based medical devices. While it puts out no radioactivity itself, it acts as a collector for radiation generated by the device’s generator, converting the projected x-rays and the shadows cast by the patient’s body into a usable image. This image can then be displayed on screen, printed to paper or film, or shared digitally with your facility network, as per the capabilities of the particular C-arm being used.

Image intensifiers can be set up for plain fluoroscopy or digital subtraction angiography, but they all offer adjustable radiation levels to allow for fine-tuning the exposure to the particular part of the body being analyzed. For example, in simple fluoroscopy, imaging of the wrist would not require the same amount of exposure as the abdomen.

The image intensifier is often referred to with the simple acronym “I.I.” and is usually rated in terms of both sensor size and magnification options. As image intensifiers require rads from the generator to illuminate their viewfinders, larger sensors call for greater radiation exposure and, therefore, considerably more over-all lifetime cost for the purchased machine as an asset. For this reason, it is important to determine precisely the usage case scenario for the C-Arms you wish to acquire. As these machines are designed to serve a wide customer base in all medical and even non-medical fields of application, no one set of specifications can be suggested; rather, the axiom about minimization should be scrupulously followed.

Planning precisely which type of procedures your future C-arm will perform on a regular, profit-earning basis will allow you to best determine how much excess radiation cost leakage and patient exposure liability best meets your state’s particular regulatory environment.

Once you have articulated your facility’s business case for this capital outlay in a procedure-by-procedure accounting of the expected use patterns, you’ll be ready to begin selecting appropriate major components which will comprise your ideal C-arm unit for that particular application.

Digital subtraction angiography is a feature of some image intensifiers. It allows preset programs from the user to dictate rate of how many images are captured and displayed every minute. Increasing this frame rate makes displayed video of the observed area smoother, but also increased dollar and rad costs.

Image intensifiers found on modern C-arm equipment are  commonly either 9″ or 12”, with Siemens also manufacturing a specialized 13″ model for some applications. They are primarily “tri-mode” view-finding devices, capable of focusing their observation over a smaller region to achieve a resultant magnification of the x-ray illumination.

9″ image intensifiers comprise the preponderance of currently-available C-arms. They are widely used for cardiac, orthopedic, pain management, general surgery pacemaker placement and sports medicine. 12” image intensifiers, on the other hand, are used almost exclusively in the vascular and neurovascular field, although they may be used for complex orthopedics as well. 12” I.I.’s are more costly, but they offer considerable advantage in some procedures; extra inches of diameter allow operators to scan more of the body at once, and this can enable run-offs and other specialized procedures which are not possible on a single run with a 9″ unit.

The other important factor in I.I. selection is the magnification modes. Although both 9″ and 12″ systems hove tri-mode image intensifiers, the relative magnification levels they offer are often not directly comparable. OEC, as an example, produces 12″ I.I.’s which offer zoomed image areas of 12/9/6, while their 9″ units can focus on targets in a 9/6/4.5 inch bracket. Thus, the smaller 9″ systems actually offer greater magnification, and so OEC only makes their cardiac platform with a 9″ I.I. Generally, specialized practitioners doing delicate work will find higher magnification more beneficial than a wider field of view. Thus, those who wish to have rads and dollars from their C-arm budget would to well to consider 9” I.I.s for all C-arm installations not specifically relating to vascular work or multi-limb simultaneous imaging.

The Image intensifier is affixed to an imaging system unit which can perform a variety of movements applicable to different surgical procedures. This, in turn, is compact and
lightweight, to allow easy positioning with a wide range of motion and adequate space for staff to work around, while remaining firm enough to avoid misalignment.