1. Portable and mobile radiographic unit
Presented by :
Dr Manjushree B M
Junior Resident

2. Introduction
Machines used for severely ill and unable patients, who cannot be brought in the radiology department.
Can be broadly divided into two types:
Portable and
Mobile equipment.

3. Portable unit
Portable - can be carried by one able bodied person at a time.
Can be taken around the hospital, some place distant from hospital or even to a patient’s home.
Simple
Can be dismantled for transfer.

4. Fig: portable radiographic units then (1912) and now

5. Components
1. Tube head:
(A) X-ray tube: Self-rectified, Stationary anode, single focal spot of 1.0mm.
(B) High-tension generator:
Tube and generator are enclosed in one oil filled tank, described as tank construction and the whole enclosure called the tube head.

6. 2. Tube stand:
support for the tube head,
3. A small control unit:
Rheostats: to vary the mA and kV.
Timer (s).
Exposure switches.

7. Fig: Schematic diagram of components of portable unit

8. Advantages
permit radiographic examination in locations limited by the availability of a standard electrical supply.
Disadvantages
Low output a typical maximum is 80 KVp at 15 mA for 1 second.
Difficult to maintain aspects of radiation protection.

9. Mobile Mobile means capable of being moved.
Mounted on wheels with the motion brake provided.
Larger and heavier than portable sets and need to be motorized or pushed by human power.
Motorized units require less effort but add to weight and cost of the unit.

10. Fig: Mobile units in 1940-1955 and now.

11. Components
Tube
Tube stand
High tension transformer
Control unit

12. Tube: Dual focus rotating anode x ray tube . Focal spot
About 1.0mm for fine focus
2.0 mm for broad focus.

13. Tube stand:
A strong vertical column mounted on the base that supports the cross arm which carries the x ray tube.
Range of movements:
Can be split into five major components.
To prevent damage to cables
movements should have mechanical stops.

14. Rotation around the centre of the column, (R)
Cross arm movements the extension of the tube head away from the centre of the column ,(A)
Rotation around the axis of the cross arm, (D)
Angulations across the long axis of the tube head,(B)
Vertical movement up and down main column (H)

15. High tension generator:
Gives a max output of 300mA and 125KVp.
Includes full wave rectification provided by means of selenium rectifiers .
The H.T. generator, its rectifiers and filament transformer for tube enclosed in one oil filled earthed steel tank.
Connected to the x ray tube by means of high tension cables.

16. Control unit: Located behind the generator tank on the base of unit.
It consists:
Mains on/off switch
mAs selector
kV selector
Focal spot selection
Body part selection
Exposure indicator

17. Mobile classification
By two ways:
By power supply:
Capacitor discharge unit
Battery powered unit
2. By output:
Low Power Mobiles: 10 to 30mA and 40 to 90 kVp.
Average Power Mobiles:100 to 150 mA and kVp.
High power mobiles : upto 300 mA and 125 kVp.

18. Capacitor Discharge Mobile Unit
Principle:
When charge circuit is activated, voltage from HTT charges a capacitor up to the kilo voltage required for the exposure.
The capacitor becomes source of power for x ray exposure. It is disconnected from the charging circuit and connected to the x ray tube for exposure.
Its discharge through tube constitutes the mAs of the radiographic exposure factors.

19. Fig : showing the working of capacitor discharge unit

20. CONTD…
When the charge button is pressed ,the capacitor is charged through high tension source by connections at G1andG2.
when required kV is reached ,charging is automatically stopped and the lamp indicates ready.
After charging has stopped when exposure button is pressed, capacitor is connected to tube at X1 and X2.it discharges through the tube and constitutes the x ray exposure.

21. kV drop:
In this design, the kV drop is around 1 kV per mAS used and the effective voltage is 1/3 of the voltage drop lower than the starting voltage.
Hence the equivalent kV=Starting kV-1/3 x mAS
Example for an exposure of 87Kv and 20mAS:
87-(1/3 x 20)= = 80Kv Effective.

22. +
X-ray Tube:
Rotating anode tube with single focal spot size of 1.2mm and heat storage capacity of 80,000 HU.
Grid controlled:
Uses a third electrode i.e. focusing cup to control flow of electrons from filament to target.
Voltage across filament-grid produces electric field along path of electron beam that pushes e-s closer.
Exposure start & stop controlled by voltage on grid.
Large enough negative voltage on grid blocks tube current from cathode to anode.

23. Control Unit Automatic charging circuit for charging the capacitor.
The kV range is from 30kv to 125kv. If pre selected Kv is altered after charging, the tube voltage is automatically adjusted to the new value.
A single mAs control, rather than mA and exposure time being selected separately. The units are usually designed to operate at a high, fixed mA value, so that exposure time becomes the main variable by default.
mAs control has 15 steps range from 2 mAs to 60 mAs.

24. Advantages:
less bulky and easily controllable.
No need for special installations as power is only required to charge the capacitor.
The voltage waveform across x ray tube is uniform rather than pulsating. It has no relationship with ac mains.

25. Shorter exposure time by use of grid controller.
Limitations:
Limited mAs output.
The maximum output range is 30-50mAs so cannot be used for heavy body part such as spine and abdomen.

26. Battery Powered Mobile Unit
Also called cord less mobile unit.
Ni-Cd batteries are used as a source of energy for x ray exposure .
The generator is referred to as constant potential generator (CPG).
Power supply is used to charge the batteries.
The batteries produces low voltage DC charge.

27. Major Components of battery Powered X Ray machine
3/26/2012
PORTABLE N MOBILE EQUIP BY SUDIL

28. Advantages
Stores considerable energy to generate x rays. can store 10,000 mAs.
Make exposures independent of power supply.
Supplies constant output of KV and mA through out the exposure.
Used in case of emergency power failure.

29. Disadvantages Batteries must be charged
Requires regular batteries maintenance
Heavy

30. Care and maintenance:
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).
Naked flames or lighted cigarettes should not be held near the batteries when they are being charged.
The acid level in the batteries should be checked every 2 weeks.

31. Mobile Image Intensifiers Units
Used in operating theatre for fluoroscopy examination.
This reduces the number of radiographs taken and saves the time during surgery.

32. Essential features of mobile unit for fluoroscopy
The x ray tube
The image intensifier
High tension generator
Control consol

33. The x ray tube and image intensifier:-
Mounted opposite to each other at the end of C –arm.
X ray tube head is at the lower end of C arm and the image intensifier is at the upper end with input phosphor facing towards the x ray tube.
The tube head houses the x ray tube.
The x ray tube is stationary anode and two focal spots.
A small focal spot of size 0.6mm is used for fluoroscopy and a large focal spot of size 1.8mm is used for radiography.

34. The C arm is mounted on a cross arm which extend from a carriage carried on a vertical support rising from the control console.
The x ray tube and the image intensifier are held directly opposite to each other with x ray beam permanently centered to the input phosphor.
At the back of I.I. is the television pick up tube, so that image can be viewed on monitor.

35. The input phosphor of the image intensifier is cesium iodide which gives good contrast.

37. Movements
The vertical support can be raised and lowered and the cross arm can be extended through the carriage.
The x ray tube and image intensifier are attached to the c arm and move together.
The c arm can be moved in any direction. so the equipment enables a good range of positions and projections to be used without wastage of time.

38. High tension generator:
The x ray tube and high tension generator are together in the tube head.
High tension generator are single phase with full wave rectification provided by silicon rectifiers i.e. the generator is two pulse.

39. Fig: Block diagram of sequence of transference of signal

40. Control unit :
Kilovoltage for fluoroscopy or radiography range from 50kv to 105kv.
mA settings or fluoroscopy range from 0.1to 3.0mA.for radiography the Kv and mA are linked .i.e.
50mA at 55kv
40mA at 80 Kv
30mA at 105 Kv
The timer for radiographic exposure is electronic and gives range from 0.1 to 3.0 sec.

41. For the television chain, circuit includes controls which allow the image to be transposed right to left and inverted top to bottom.
There is control for memory circuit with two magnetic disc that is image storage is possible.
There is facility for pulsed fluoroscopy with electronic selector: the rates provided vary from 1 flash per sec to 1 flash every 5 sec.
This allows to monitor dynamic events without subjecting the patient to continuous radiation.

42. Advancements High frequency generator mobile units
Computed radiography mobile x ray unit
Direct radiography mobile x ray unit

43. High Frequency Generator
Recently high frequency generators are more popular for use in radiology for mammography and mobile units.
One of significant advantages is its compact design.
Converts low frequency (60 HZ) to high frequency (KHZ) pulsed DC, by altering waveform of incoming electrical circuit which is subsequently increased to kilovolts, rectified and sent to the x-ray tube.

44. Produces a nearly constant voltage wave form with extremely low ripple(<1%).
Provides great x-ray quality(effective energy) and quantity. More efficient.
More expensive than previous mobile units.

45. Uses inverter circuit.
The DC power supply produces a constant voltage from either a single phase or three phase input line source.
inverter circuit creates the high frequency AC waveform.
This AC current supplies the high voltage transformer and creates a waveform of fixed high voltage and corresponding low current.

46. After rectification and smoothing two high voltage capacitor on the secondary circuits accumulates electron charges. These capacitors produce a voltage across the x-ray tube, that depends upon the accumulated charges

47. Fig: Block diagram of high frequency generator

48. Mobile CR

49. Digital portable unit

50. Construction

51. Includes a transport case housing several components, a digital x-ray image sensor and x-ray generator.
A pt. support unit is disposed b/w image sensor and x-ray generator.
An image display unit is connected to image acquisition unit and spaced from generator.

52. The image sensor is a thin film transistor (TFT) based digital x-ray image sensor. Preferably, digital image sensor is about the same size as standard medical x-ray films. The sensors can be grouped into two categories:
1)indirect x-ray sensors
2) direct x-ray sensors

53. indirect x-ray sensors: feature a TFT photodiode array that is sensitive to visible light. These sensors are covered by an x-ray to light converter such as gadolinium oxysulfide or cesium iodide which converts each incident x-ray photon into light photons. The light photons are converted into electronic charge at each pixel photodiode.

54. direct x-ray sensors: is coated with amorphous selenium which converts incident x-rays directly into electronic charge at each pixel.
In both cases electronic charge distribution collected by pixel array is proportional to intensity distribution of x-ray photons. This charge distribution is digitized and stored in a computer.

55. In order to display images generated by image sensor image display unit is provided with software that at least supports images in DICOM and JPEG format.

56. Table : Tube parameters of digital portable

57. Digital mobiles
The digital mobile units are the ultimate solution to mobile X-ray imaging for digitization in ER, traumatology, intensive care units (ICU), in patient wards and pediatrics.
The system represents an evolutionary move in mobile diagnostic imaging equipment and includes unique features in terms of operability, mobility and image quality.

58. The system meets today’s and future clinical demands providing the premium solution for
immediate image processing
an efficient clinical workflow
a rapid display of high-quality clinical images
fast integration into the hospital network

59. Digital mobile units

60. Features Generator: High frequency generator
Kvp Range: Kvp, adjustable in 1 kV increments
mA range: Fixed, 15 mA and 30 mA
mAs Range: 0.15 – 120 mAs
Exposure Time: s

61. Indicators: Digital display of kVp, mAs and Time, X-Ray, Ready, mA Station and Fault Indicators
Exposure Switch: Detachable two position switch
X-Ray Tube: Stationary Anode Filtration-2.7 mm aluminum
Target Material: Tungsten Anode Capacity: 30,000 HU Storage Focal Spot: 1.0 mm Target Angle: 15 degree.

62. Thank you