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Introduction
Emergence of digital technology has brought innovations in the field of medicine. Amongst them is the emergence of mini C-arm. C-arm technology is based on the use of digital electronics and provides benefits that were not available in the 1970s and 1980s. Forces behind the modern mini C-arm technology are not different from those in any other field1. Some of the main features of mini C-arm are digital imaging technology, easily portable, image accessible at multiple locations at the same time, images can be transmitted over long distances without being distorted and better image quality.
In this article the emphasis will be on the features of the most advanced mini C-arm and its benefits over conventional and earlier versions of C-arm/mini C-arm. This study aims to review the mechanism, functioning, advantages, disadvantages and recent advances in mini C-arm technology2.
C-arm/mini C-arm mechanism
The mini C-arm mechanism is based on the fluoroscopic imaging. X-rays cause ionisation of atoms and can alter the DNA. The ionisation of atoms causes the movement of free electrons and that is termed the current. The fluoroscopy is performed by using the current value of around 3-6mA and it requires a voltage value of 80-125kVp. The production of X-ray is proportional to the current flowing through the X-ray tube; however, sensitivity is increased by increasing the voltage. A fluoroscope consists of various components; Figure 1 shows a typical fluoroscope and its components:
The X-ray generator allows the adjustments of voltages and currents through the X-ray tube; the function of the X-ray tube is to convert the electrical energy into an X-ray beam. The collimator determines the X-ray beam by using the blades; whereas patient table and pad provide support to the body of the patient and minimise the attenuation of X-ray. The image intensifier converts X-rays and enhances the brightness of the image. There are different sized diameter intensifiers based on the devices e.g. conventional and mini C-arm etc2.
Figure 1: Typical Fluoroscope model2
A fluoroscopic unit operation is based on the automatic brightness model (ABC). In the ABC model the brightness of the image is monitored by the image intensifier. If there is not enough brightness the ABC enhances kVp which increases X-ray penetration through the body or tissue of the patient2.
X-rays are electromagnetic radiations and when they strike a tissue they either completely penetrate or are absorbed completely or partially with scatter. A complete penetration results in an image, complete absorption means no image. Partial absorption will result in an image with scattered radiation being potentially harmful to the theatre staff. To overcome such issues the C-arm technology was introduced2,3,4.
A C-arm unit can be manoeuvred in different ways based on whether the whole unit or only the C-arm part of the unit is moved, see Figure 2.
Figure 2: C-arm unit2
Some of the advancements in the C-arm technology are discussed in the next section.
Advantages and disadvantages
Fluoroscopic imaging systems such as mini C-arm and conventional C-arm both use X-rays to provide images, but there are many advantages offered by the mini C-arm compared with the conventional C-arm. Mini C-arm is smaller in size which gives better workplace access, mini C-arm is surgeon operated, it is easy to use and without the need for a radiographer, which will reduce delays, cost of surgery, and demand on the radiology department5,6,7.
It has been found that the use of the machine that allows surgeon control of the foot pedal can significantly reduce the screening time and scattered radiation dose7. The main benefit of mini C-arm over the conventional C-arm is to reduce the dose of scattered radiation to patient, surgeon and theatre personnel. And it can be explained by its small detector area, lower laser power, tight beam collimation, surgeon control of screening and the new technique of pulse fluoroscopy. Other benefits of mini C-arm are better manoeuvrability, precision and also immediate printout facility3,5,6,7,8,9.
There are some disadvantages as well, because of small low power X-ray generator and small field of view; the image quality of conventional C-arm is better than that of mini C-arm6. The