Transcript Mobile Radiography Course

Mobile Radiography Course
RAD 1304
Instructor: TAGELDIN ABUGROON
Mobile Equipment Feature
Introduction
 What is mobile x-ray equipment?
 It is equipment which can be moved from one place to
another and used at the patient’s bedside.
 What is used for?
 It can be used to provide facilities for the following cases:
(1) In-patients who could not leave their beds, especially
those who cannot be moved away from their ward.
(2) Surgeons who required X-ray control guidance during the
course of their work in the operation theatre.
 These days bedridden patients who are in need of
radiography are now transferred safely from their ward to
the imaging department, where they can be examined with
all the efficiency that the department can offer.
 These facilities include full radiation protection: for the
patient, of course, but also for other personnel who
otherwise, in the hospital ward, could have been at risk.
Therefore, their use should be restricted.
 Despite these points, the service of mobile X-ray equipment
can be in demand all day especially in a busy hospital and
with complicated situation patient. Study of the principal
features of their construction and operation is necessary, as
always, for correct and safe use.
X-Ray Equipments
Major X-ray Unit
Portable Units
Mobile Units
 What are the differences between mobile &
portable unit?
 The broad distinction between the two being the difference
in power output and the ability to transfer equipment.
 Portable units are small and light in weight, which normally
can be dismantled and carried, usually by one person, and
have relatively low radiation output.
 While Mobile x-ray units are bigger and heavier than
‘Portable’ units which is movable but because of its weight
and size can only be wheeled along flat surfaces to place
where required, they are usually have higher radiation
output.
Portable unit which can be dismantled & carried by one person
Portable units features
Advantages:
1- Light weight.
2- Standard power supply.
Disadvantages
1- Low output.
2- Lack of stability.
3- Lack of precision.
 The output of the machine can be determined by
The following equation:
P=I.E
 Where:
P= Power (Watt)
I= Current (Amper)
E= Voltage (Volt)
Example:
 Exposure factors: 100 kVp, 50 mA.
• P= _50_ A × 100,000 = 5000VA
Supply: 240 V
1000
• I= 5000 = 21A
240
 if we change the Volts to 480V, what would be happened?
• I= 5000 =10.5 A
480
 As we increase the line voltage, the current flowing is
reduced. Therefore the output of the machine will be
decreased.
 Remember that changing the exposure factors change the
current requirements. Therefore you need to know the
current required and the voltage of the power supply before
you do exposure.
Components of Portable units:
1- Oil-Filled lead lined tank:
In order to make the equipment simpler, lighter, less
expensive and easy to carry, it is usually constructed with:
(A) X-ray tube: Self-rectified, Stationary anode.
(B) High-tension transformer. (HTT)
(C) Filament transformer.
 This is described as a tank construction and the whole
enclosure is called the tube head.
2- A small control unit:
(A) Rheostats: to vary the mA and kV.
(B) Timer (S).
(C) Exposure switches.
Output: The maximum output is usually 80 kVp and 20 mA.
Mobile units feature:
 Capable of being moved either manually or motorized
drive.
Advantages
1. Great stability.
2. High output.
3. Wide range of KV & mA selections.
4. The control panel and the high tension generator (with fullwave rectification) all are carried by strong machine base,
away from the tube which have an advantage to greatly
increased the x-ray output.
5. It has a rotating anode.
6.Flexible tube movement.
Disadvantages:
1. It is heavy in weight.
2. It needs especial maintenance.
Output Up to 300 mA and maximum of 125 kVp.
Mobile Unit in 1940 -1955
Mobile units
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Construction of Mobile Unit:
1.High generation tank containing the HT transformer
2. Handle for pushing the unit.
3. Control unit.
4. Lock.
5. Tube Column.
6. Bowden cable allowing vertical movement of
the cross arm.
7. Movement of the cross arm.
8. Hinge joint to allow extension of the cross arm.
9. HT cables.
10. Column base allowing rotation of the cross arm
around column.
11. Base plate.
12. Large wheels for easy movement.
Mobile units Classification
They are classified by two ways: output & Power Supply.
(A) By output:
1-Low Power Mobiles :
These operate at max. x-ray current (mA) of 10 to 30 with a
range of 40 to 90 kVp.
Example: Dental, war x-ray equipment.
2- Average Power Mobiles :
These operate at a range x-ray current (mA) of 50 to 60, 100
to 150 mA with a range of 40 to 90 kVp, 95 kVp.
Example: for skull, limbs.
3-High power mobiles :
These operate at max. of 300 mA, at a max. 125 kVp.
Example: for CXR , abdomen, skull, Pelvimetry, IVU,
pediatrics.
By Power Supply
Main Supply Equipment
Capacitor Discharge Equipment
Battery powered Equipment
Main Supply Equipment
Advantages & disadvantages:
 Energy may be drawn for X-ray exposure directly from the
mains voltage supply. This is convenience if there is no
need for the energy to be carried around within the mobile
unit.
 But cable resistance and supply variation at different
locations where the unit is used can raise difficulties
affecting image quality.
Special Features
 This kind of equipment must have a robust connection
cable. This encloses 3 low resistance conductors, each with
a relatively large cross-sectional area. Two of the
conductors carry the current, which the generator draws
when an exposure is made. The third provides a safe,
reliable connection to earth.
 The cable must be long enough (2 meter) for equipment to
be used in most locations, provided there is a convenient
mains outlet socket, but not so long that its resistance
becomes significant. The cable should be manufactured to
tolerate physical damage.
Capacitor Discharge Equipment
Advantages & disadvantages
1.Small in size and light in weight, because there is no H.T.T.
2.This unit has the advantage of storing energy in the form of
electric charge for later use for X-ray exposures.
 Therefore, it can be used in places where there is no
electricity, or no a convenient mains outlet socket, or there
is electrical power but not adequate (not enough to operate
the X-ray unit), or suffers ‘drops’ in its values.
3.The unit has the advantage of providing high X-ray output
(usually high mA). The given kVp is from 30 or 40 up to
100 to 125 kVp and 500 mAs.
4.Shorter exposure time. By using grid-controller, this grid
plate is exist between the anode and the cathode in the
tube.
 This grid allow the electrons to pass through it and reach
the anode (by carrying zero charge or no charge on it), this
grid can stop the electrons passage after a specific time by
carrying -ve charge on it which will reverse action and stop
the exposure.
5.It has no timing control device since only the kVp has to be
selected, so the mAs depends on the kVp. As the kVp in the
capacitor discharge falls the mAs does so.
6.Simple in operation, it can be supplied by any voltage from
60V to 220V (so we shouldn’t worry from voltage
fluctuation).
7.Provides consistently reliable output and results (uniform
wave), which has the advantage of less absorbed dose to
the patient and good image quality.
 This consistency happened because the main voltage and
resistance variations only have their effects upon the act of
charging the capacitor, which takes place just before the Xray exposure is made.
 While in the mobile unit that use the conventional generator
provide the X-ray tube with a pulsating waveform voltage
which varies from peak to zero then go back to peak which
effect the image quality and patient protection.
8.Capacitor discharge is usually limited so that the drop in kVp
is only 35% on heavy exposure.
9.The disadvantage that it has the limitation in exposures.
Few times of exposure needs capacitor charge.
Working of the Capacitor
Charging Stage
After the radiological Technologist connects the unit to the
mains and selects a kVp value, the switch operated to
charge the capacitor to the required kVp (G1 & G2 will be
connected), via the high tension generator, then the
capacitor acts as a store or source of energy.
Discharging-exposure stage
By pressing the exposure switch the X1 & X2 will be
connected then the capacitor will discharges electrons
through the X-ray tube and produce X-ray exposure.
Special Features
1.Charging circuit contains solid-state rectifiers (selenium
types) and capacitors these two acts as energy storing
elements and as voltage multipliers (raise voltage to higher
kV values, instead of the high-tension transformer).
2.The size of the capacitor determines the maximum output
(mAs); this is called Capacitance Value (C.V.). For example;
if the typical C.V. for charging capacitor is 1.0 the typical
mAs are between 0.4-60 mAs. After every exposure we do
the mAs will be reduced.
3.Its tube has rotating anode and grid-controller.
Battery Powered Generator
 This is called also cordless mobile unit (mains-independent).
This unit use batteries as a source of energy for X-ray
exposure.
Advantages:
(1) This machine can be used freely, provides wide range of
satisfactory kVp & mAs.
(2) This machine could be recharging less frequently that the
capacitor one. Some machine allows you to take up to 500
exposures without re-charging.
Disadvantages:
 It needs special care and maintenance.
Special Features:
 This kind of machine usually uses 2 batteries of car kind
12V (24v d.c.). All batteries are sealed for safety.
 Charging is achieved by connecting the generator to the
mains at times when it is not required for radiography.
These batteries also used as a motor for the unit wheels
that makes the driving of the machine much easier.
 The batteries need regular care and maintenance. If the
machine is well maintained, it could last up to two years of
their working life.
Care & Maintenance of Battery powered Generator
 This care and maintenance includes:
(A) The unit should be left connected to the mains power
supply of (200v or 115v):
– Every night.
– During weekends.
– At all times when the unit is idle (not being used).
(B) Naked flames or lighted cigarettes should not be held near
the batteries when they are being charging up (because of
the risk of the hydrogen gas explosion).
(C) The acid level in the batteries should be checked every
2 weeks. Its proper recommended level is 6.0 mm above
the plate separation. If the level drops below this, distilled
water (only) must be added.