A C-arm is an imaging scanner intensifier. The name derives from the C-shaped arm used to connect the x-ray source and x-ray detector to one another. C-arms have radiographic capabilities, though they are used primarily for fluoroscopic intraoperative imaging during surgical, orthopedic and emergency care procedures. The devices provide high-resolution X-ray images in real time, thus allowing the physician to monitor progress and immediately make any corrections.
X-ray image intensifier
An x-ray image intensifier (XRII) is an image intensifier that converts x-rays into visible light at higher intensity than mere fluorescent screens do. X-ray imaging systems use such intensifiers (like fluoroscopes) to allow converting low-intensity x-rays to a conveniently bright visible light output.
Through its intensifying effect, the viewer can more easily see the structure of the imaged object than fluorescent screens alone. The XRII requires lower absorbed doses due to more efficient conversion of x-ray quanta to visible light.
Permanent/Fixed Fluoroscopic Systems
There are two main configurations of permanently installed fluoroscopic systems. One class commonly utilizes a radiolucent patient examination table with an under-table mounted tube and an imaging system mounted over the table. The other is commonly referred to as a C-arm system that is used where greater flexibility in the examination process is needed.
The C-arm systems are commonly used for studies requiring the maximum positional flexibility such as:
- Angiography studies (peripheral, central and cerebral);
- Therapeutic studies (Line placements, transjugular biopsies, TIPS stent, embolizations);
- Cardiac studies;
- Orthopedic procedures
How does a mobile C-arm work?
Mobile Fluoroscopic System, also known as portable or mobile C-arm, comprises a generator (X-ray source) and an image intensifier or flat-panel detector. The C-shaped connecting element allows movement horizontally, vertically and around the swivel axes, so that X-ray images of the patient are produced from almost any angle.
The generator emits X-rays that penetrate the patient’s body. The image intensifier or detector converts the X-rays into a visible image displayed on the C-arm monitor. Physician can check anatomical details such as bones and the position of implants and instruments at any time.
Flat-panel detectors VS Image intensifier
Flat-panel detectors (FDP) are increasingly replacing image intensifiers (II) on mobile C-arm systems, part of a migration of technology once available only in fixed room systems.
The advantages of this technology include: lower patient dose and increased image quality and no deterioration of the image quality over time.
Despite FPD’s higher cost, the noteworthy changes in the physical size and accessibility for the patients is worth it.
Three-dimensional (3D) C-arm computed tomography is a new and innovative imaging technique. It uses two-dimensional (2D) X-ray projections acquired with a FDP C-arm system to generate CT-like images. To this end, the C-arm system performs a sweep around the patient, acquiring up to several hundred 2D views. They serve as input for 3D cone-beam reconstruction. Resulting voxel data sets can be visualized either as cross-sectional images or as 3D data sets using different volume rendering techniques. Initially targeted at 3D high-contrast neurovascular applications, 3D C-arm imaging has continuously improved over the years and now provides CT-like soft-tissue image quality. In combination with 2D fluoroscopic or radiographic imaging, 3D C-arm imaging provides valuable information for therapy planning, guidance, and outcome assessment all in the interventional suite.
Potential safety issues
Failure of the x-ray beam collimation may lead to primary beam x-ray exposure outside of the selected image intensifier input area. This would result in image degradation. Light generated outside the area of the image intensifier input at magnification causes additional loss of contrast of the image with increased noise. Additionally, unnecessary additional dose to the patient would result. If the C-arm or fittings are damaged, the x-ray tube and intensifier may become misaligned resulting in image degradation or loss, as well as presenting a potential injury to staff and patient if the structural integrity of the C-arm or mounted components are compromised.
Major market players
Here’s a look at what the major players in mobile C-arm are offering in their systems.
The latest ARCADIS platform provides a strong focus on image quality and dose reduction. The technology allows for longer procedures and accommodates larger patients while virtually eliminating overheating and procedure delays. Plus the improvement in image quality makes it possible to accomplish longer, more complex exams. All systems have integrated software to automatically control contrast and brightness and also dose control to help support safety without compromising image quality. ARCADIS Orbic 3D, the high-end C-arm with isocentric design and 190-degree orbital movement, was developed for spine and neuro work. It can be equipped with NaviLink 3D1, the direct 3D navigation interface.
Today, three in four US surgeons use in surgery. GE has introduced several programs and enhancements around issues of particular customer interest: workflow, ergonomics, cost, and reducing clinician dose. There are more than 34,000 OEC mobile C-arms, including 10,000 OEC 9900 Elite systems, in use throughout the world. OEC has proprietary precision imaging technology using Dynamic Range Management for high-quality images in almost every situation.
Philips continues its innovation of flat-detector technology with its second-generation Veradius Neo, following the introduction of the Veradius flat-panel detector system. The company’s fixed system shares the detector technology, offering superior image quality while lowering dose.
Veradius Neo features a new C-arc geometry with maneuverability specially designed to accommodate even obese patients.
Once in the desired position, the system’s flat-detector technology provides high-quality images without the distortion. Surgeons can use these undistorted images to help place screws and other devices with precision. The flat detector on the Veradius Neo has a greater dynamic range than older II technology.
X-ray dose remains a concern for all C-arm manufacturers, particularly in general procedures and long minimally invasive procedures. Veradius Neo incorporates a full range of dose management features that allow low X-ray dose without compromising image quality.