Mobile X-Ray Equipment.
Features :
The word ‘mobile’ means that the x-ray equipment is capable of being moved. It is mounted on the wheels and can be pushed by operator. It is larger and heavier than portable equipment and needs to be motorized.It cannot be separated into smaller components and cannot be taken outside the hospital.
Mobile sets have high value and heavier. Mobile xray units designed to fulfill a wide range of cinical application in any location of department such as ICU, CCU , emergency.
Physical Features.
1. Size: Mobile equipment must be so designed as to e easily accomodated in limited space. i.e. ward, alongside beds.
Range of Movements.
The range of movements available is one of the most important factors of mobile equipments, The range of movement can be spilt into five major componments:
1. Rotation around the centre of column
2. Cross arm movement, the extension of tube head away from the centre of the column.
3. Rotation around the axis of the cross arm.
4. Angulation across the long axis of the tube head
5. Vertical movement up and down clumn.
In order to prevent damage to cables all movements should have mechanical stops.
Some machines have an extending column to increase the range of height movement.
Movement locks and limites are of four types.
1. Frictions locks.
2. Electro-mechanical locks
3. Counter balance system.
4. Rack and penion electrical drive.
Cable Storage: Some equipment has special retracting cable drum that minimize cable damage.
Light beam diaphgram : Most mobile equipments has light beam collimator with fully adjustable collimation.
Wheel and drive:
1. Motor power is provided by human effort.
2. Motor driven.
Electric Supply : Low power mobile unit oprtates at 10 mA to 30 mA with 40-30kvp.High power mobile upto 300mA -125 kvp.
Components:
1. X-ray tube: The X-ray tube for high power mobile set is a dual focus, rotating anode x-ray tube.
2. Tube Stand: The base of the unit is usually 629 mm wide and 1219mm long. A strong vertical column mounted on the base supports the cross arm has telescopic extension so that the tube can be positioned at a distance of 1067mm from the centre at the vertical arm.
3. High Tension generator:
Ø Gives maxiumum output 300mA, 125 Kvp
Ø Includes full wave rectification.
High tension generator , filament , transformer are enclosed in one oil filled earthed steel tank.
4. Control Unit: It includes
a) Mains on/off switch.
b) mA selector allows six different tube current. (5mA , 50, 100, 150, 250 ,300 mA).
c) Kvp selector, 40steps of selections.
d) Exposure timer: 0.02-5 sec
Portable X-ray unit: The word portable means that the x-ray unit is capable of being carried outside from the radiological department.
Physical features:
1. Size : It is often heavy but major part can be separated during transportation.
2. Weight: Each individual part is usually light enough to carry but composite weight may be too heavy. The major weight are the x-ray tube head abd support system.
Typical tube head may weigh about 30 kg.
3. Electrtical Supply : The unit is being operated from a standard domestic 15 Amp socket.
Typical maximum power range 240 volts at 15 Amp peak for an exposure of 70Kvp at 10-15 mA.
Components of portable x-ray unit.
1. X-ray tube
2. Tube stand.
3. Control Unit.
4. High tension generator
5. Radiographic output and mains requirements
X-Ray Tube: The x-ray tube and high tension generator are enclosed in one earthed enclosure is called tube head. High tension cable are not required, only low tension cable are not carry supply voltage to the tube head.
The X-ray tube is small stationary self reatified and connected directly across the secondary winding of high tension (H.T) generator. The tank(enclosure) is constructed in such a wat that it doesn’t take much space. Small stationary X-ray tube generally has effective focal spot about 1.0mm with relatively low radiographic rating.
The tank is filled with oil to insulate and cool the component contained in it end it is vaccum selaed. There is the facility for attaching the beam limiting devices on to tube head.
Tube Stand: The tube head is attached to a support which is on a carriage mounted on the vertical mounted on the vertical column of movable stand. There is handle which moves the tube head up movement of the tube focus from floor is 690mm- 950 mm when tube projected downword.
The Control unit: Control unit is housed in a small box. It consist of 3 leads.
1. The low tension cable coming from the tube stand plugs into the control unit.
2. Control unit takes the plug of thinner cable to hand switch. The hand switch carry push button to initiates the exposure . The length of cable should be at least 2m.
3. The third lead is the main lead with plugs that goes into the wall socket at outlet point of the supply.
Advantage:
1. Permits radiographic examination in location only limited by standard electric supply.
2. Very simpler, less expensive, lighter.
Disadvantage:
1. Low output.
2. Difficult to control X-ray safety for radiation protection.
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