How is the X-ray tube cooled?
The anodes in most radiographic equipment are cooled by the natural radiation of heat to the surrounding tube enclosures. However, anodes in some high powered equipment, such as that used in CT, are cooled by the circulation of oil through the anode to a heat exchanger (radiator).
Why is there a cooling system in X-ray tube?
Medical imaging systems require conflicting requirements of increased heat pumping performance with lower power consumption. As a result, liquid cooling systems are often the preferred choice to move heat away from the X-ray tube to ensure quality images are produced.
Why it is necessary to provide cooling for the anode?
ANODE BODY. The heat capacity of the focal spot track is generally the limiting factor for single exposures. In a series of radiographic exposures, CT scanning, or fluoroscopy, the build-up of heat in the anode can become significant. Excessive anode temperature can crack or warp the anode disc.
How do you warm up an X-ray tube?
Typical warm-up exposure settings use low kVp (60-70), and a long exposure time (1-5 seconds). One warm-up exposure should be made using a small focal spot (50, 100, 150, 200, or 300 mA), and a second exposure should be made using a large focal spot (400, 500, 600, 700, or more).
What is anode cooling chart?
Anode Cooling Chart. Conveys the capacity of the anode and its heat dissipation characteristics. Causes of tube failure. A single excessive exposure causes pitting or cracking of the anode. Long exposure time causes excessive heating of the anode, resulting in damage to the bearings in the rotor assembly.
What is focusing Cup in xray?
A focusing cup is a negatively charged, shallow depression on the surface of the cathode of an x-ray tube, which concentrates the electron beam towards the focal spot of the anode. It is typically composed of nickel. The negative charge of the focusing cup helps to accelerate the electrons towards the anode.
What is anode heat?
The anode converts the energy of incident electrons into x-rays dissipating heat as a byproduct. Most x-ray tube anodes are made of tungsten (the target material). Tungsten has a high atomic number (Z=74) and a high melting point of 3370°C with a correspondingly low rate of evaporation.
What is a tube warm up CT?
By warming up your CT system’s x-ray tube, you’re helping to prevent tube damage due to thermal shock. Normally, warming up the x-ray tube is done by taking several exposures while waiting 30 seconds – 1 minute between them, but varies due to the variety of CT manufacturers.
What is stationary anode?
A stationary anode is used in dental X-ray machines, portable X-ray units, and special purpose units, where high tube current and power are not required. Tubes with rotating anodes are used in X-ray units of larger capacity capable of producing high intensity X-ray beam in a short time.
What is focal spot?
Focal spot is the area of the anode surface which receives the beam of electrons from the cathode. It is the apparent source of x-rays.
What kind of coolant is used for medical X-ray?
Medical X-ray systems may utilize two different types of X-ray tubes that impacts the type of coolant used in the liquid cooling system. With bipolar tubes, the cooling fluid around the anode is in contact with the electrical potential, so it must be a liquid that does not conduct electricity, such as oil.
When was the Coolidge X ray tube invented?
Wilhelm Roentgen discovered x-rays using a Crookes tube in 1895. Until the invention of the Coolidge tube in 1913, all x-ray tubes were based on the Crookes or cold cathode gas tube technology. From the late 1910s onwards there was a rapid replacement of gas tubes by the far more effective Coolidge tubes.
Why was the specialheat unit added to the X-ray tube?
Although the joule is the basic unit for energy and heat, it is not always used to express x-ray tube heat. The specialheat unit (HU)was introduced when single-phase equipment was common to make it easy to calculate heat. The relationship between a quantity of heat expressed in heat units and in joules is given by
Why do we need a cooling system for X-ray?
Usually requiring a low heat load of <300 Watts, cooling systems must provide precise temperature control for X-ray detectors to enhance image resolution. The trend is to reduce the size of X-ray machines and increase power densities as product form factors continue to shrink.