C-Arm is the general name of x-ray imaging equipment which is based on an x-ray source and electronic image detector. Such equipment is used in cath labs, angiographic rooms, fluoroscopy rooms etc.
The C-Arm itself is a large arc bearing the x-ray tube on one end and the detector system on the other end. It can be maneuvered around the patient to the necessary position for capturing the image.
However, C-Arm equipment is an integrated system of several major C-Arm parts:
- The C-Arm – This C-Arm part is arc-shaped like the letter “C” or “U”. It is either floor-mounted or ceiling -suspended. It can be moved, turned and angulated to enable practical degrees of freedom as much as possible. This C-Arm part should be very robust and stable, easily moved and well balanced. It is electronically controlled. However, it can be manually moved in all directions and angles. The load which is carried by this C-Arm part is very heavy: the x-ray which emits the radiation, and the image intensifier which is also a major C-Arm part. In modern equipment this C-Arm can be replaced by a flat panel detector.
- The x-ray tube (and its assembly) is the C-Arm part which provides the x-rays. This C-Arm part is a high-power device which produces a lot of heat. The whole system should be designed to prevent rapid aging of the tube.
- The image intensifier is a very important C-Arm part seen on the older systems. This C-Arm part is basically a vacuum tube with a large input screen, which is sensitive to x-ray photons and emits electrons. The electrons are accelerated by the electrostatic field inside the tube and focused on a small screen which converts the electron flow to a small visible bright image. An electronic camera converts the image to a metrics of numbers which are later processed and displayed on video screens.
- The flat panel detector is the modern C-Arm part replacing the image intensifier. It is relatively small and its output fits modern electronic systems.
- The generator is the high voltage high power C-Arm part. It is the source of the direct current which energizes the x-ray tube. Old generators (50/60 Hz) are very bulky and heavy.
- In newer systems, the generators are of the high-frequency type, so they are light and occupy less space.
- The patient table is another important C-Arm part. It is completely separated from the C-Arm and the other C-Arm parts. However, it is electronically integrated into the system and should be stable and easily controlled by the operator.
- Automatic collimation through using shutter and iris collimators C-Arm parts to minimize x-ray dose to the patient and the operator.
- X-ray switching C-Arm part, which controls on/off periods of the exposure. It plays an important role in the cine mode during coronary angiography and peripheral angiography.
- A specialized digital image processor with the selected programs. This C-Arm part can contribute a lot to the diagnostic value of the image.
- The working station of the system. This C-Arm part should be designed to perform advanced processing of the locally acquired images or imported images (via the PACS system or by other ways).
Some big medical centers install two C-Arm systems in the cardiac catheterization room or in neurological dedicated angio rooms. In these situations, one C-Arm is floor-mounted and the other is ceiling-suspended. Each system includes its own separate set of C-Arm parts, however both systems can be synchronized. Such an approach can save the quantity of the injected contrast media, and simultaneously provide two different images.
Advanced imaging modalities are accelerating the knowledge and understanding of vascular and cardiovascular disease at a rapid rate, and new imaging modalities are no longer in the domain of the non-invasive specialist, as these new techniques also apply to imaging in the cardiac catheterization laboratory and general angio rooms.
In particular, 3 Dimensional (3-D) rotation angiography is a novel and exciting modality rapidly finding a number of applications. This technique entails the C-Arm rotation, acquiring sequential projection images from the multiple angles and reconstituting them into 3-D data sets.