X-Ray Repair and Its Maintenance

 

achieve a good working knowledge kn owledge of equipment maintenance routines; 

adopt a logical and practical approach to diagnosing equipment problems; 

on returning to their respective areas areas after completed training, teach other members of their 

staff carry out the routines routines or techniques that they  the y  have to learned; .

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assistt inmaintenance assis establ establishing, ishing, programme; or imple implementing, menting, a suitable suitable routine main tenance ad justments ts  be encouraged to directly carry out adjustmen or minor repairs, or pro p rovide vide suitable suitabl e assistance to other staff as needed;  provide accurate reporting of problems to seniors or service engineers; engineers ; 

assist in establishing assist establishing criteria for equipme equipment nt replacement, where it is not cost effective to continue maintenance

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EXPECTED BENEFITS of departments departmen ts will ffind ind that the standard of radiography will b bee maintained maintain ed at the highest level.  There will be fewer equipment failures .This reduces costs.

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Heads

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 Where a failure does occur occur,, llocal ocal hospital staff  may be able able to repair repair without without an expensive expensive service ser vice call. 3

 

 When an external service servi ce call is required, the service servi ce technician can arrive fully informed to deal  with the situation, situation, together with appropriate equipment equipme nt or parts. This will will reduce the possibility possib ility,, and expense, of repeated visits

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 Where work work is carri carried ed tenance out by an external service vice organization, the main maintenance inspection inspe ctionser will ensure this has been carried out fully and effectively. 4

 

 Work environments will be improved. T  Work Tasks asks wi will ll becomee easier becom easier.  Repeat films will be kept to to a minimum. Staff job satisfaction will increase. less  Patients will receive less radiation and less inconvenience.  A record record and audit trail will exist exist as proof of high standards. 

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ROUTINE ROU TINE MAINTENANCE y y

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Contents a. What is routine maintenance?

b. Who should carry out routine routin e maintenance? c. Objections Objecti ons to routine routine maintenance mai ntenance d. How often should maintenance be carried out? e. Typical Typical objectives o bjectives of routine routi ne maintenance f. Familiarization of equipment g. Routine maintenance programme h. Keeping a logbook i. Routine maintenance modules 6

 

Routine maintenance y

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Routine maintenance is a procedure to ensure equipment is kept in good good condition, condition , and provide a long operating life. Routine maintenance may also discover potential problems, which could cause equipment failure. Potential problems can then be b e corrected, corrected, with a minimum of down time. Quality control procedures, to ensure correct operation and calibration, are also a part of routine routin e maintenance.

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Who should carry out routine maintenanc maintenance e

This depends on the size of the department, and available staff. When the department department has a number of staff one member should be selected as maintenance coordinator. coordinator. Other staff mem members bers may be allocated specifi speci ficc areas or items of  equipment equipm ent tto o be chec checked. ked.  Where possible, these duties should be rotated. rotated. This allows all staff to become familiar with the equipment.

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Objections Obj ections to routine maintenance Existing

staff may regard routine maintenance as an unwanted extra duty. duty. This list prov provides ides answers for possible objections.  This is boring.  Yes, it can be. But even more boring, or frustrating, is using equipment equipmen t that does not func function tion correctly correctly..  This is not my responsibility. E ven when a specific member of staff  does carry  out a comprehensive maintenance programme,your own input will be appreciated.This can be as simple as problem area, to taking direct action. Forreporting example,atighten that lloose oose screw on a Bucky  tray handle, before the handle falls off.

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The department is kept very busy. There is no spare time.

 And to make matters worse, you have to use equipment that does notdoes operate A maintenance programme not correctly. have to take the room out of action. Instead, I nstead, just j ust one section at a time can be checked .This may take take only ten minutes for each section .After . After the rreported eported problem areas have been fixed, the room will become more efficient.

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d. How often should maintenance be carried out? 

in heavy use, for example example a mobile travelling trav elling to different parts of the hospital, hosp ital, should shou ld 

Equipment

be checked every four months.  Other equipment, such as a Bucky or Fluoroscopy  room, every six months.  However, in many respects, maintenance in the form of observation is a continuous process. If I f a minor problem occurs, always enter this in the logbook, logboo k, so it will receive attention during the next opportunity.

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e.Typical objectives of routine maintenance

 A complete operation and function inspection, list any incorrect operation or area requiring further fu rther attention.  By means of prepared checklists, ensure all required 

areas are covered. The results are to be retained in a suitable folder folder.. Any problems or areas requiring requir ing further attention attention are entered in the logbook. lo gbook.  When a problem is located, if i f thi thiss is minor, minor, correct the problem immediately i mmediately.. In I n case of a larger problem, still stil l attempt to complete the rest rest of the routine maintenance, while whil e waiting to have the specific specif ic problem problem corrected.

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In case of a specific problem outside local resource

to immediately correct, correct, and then request an electrician, or the service serv ice department, for assistance. If such s uch a pr problem oblem is i s found, be sure to file fi le a report and enter specific details in the logbook. Inspection of all electrical plugs, cables, and other electrical connections.  A full mechanical inspection, adjustment and lubrication as required.

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Tests for calibration of equipment .This .Thi s may also be part of a quality control programme.  Cleaning of equipment. Remove pieces of sticky  tape, old sticking plaster marks etc. 

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 f.. Familiarization of  f o f equipment  eq uipment  During routine routin e

maintenance, you should attempt to be familiar with all operation modes of your equipm equipment. ent. This includes.  Indicator lights. When do they light up? What do they mean?  Audible signals. When do they occur? What is the reason? During preparation, preparat ion, or an exposure, do you hear a contactor or relay operating? operating ?  What is the normal sound produced by the X-ray  tube anode, during preparation?  What sound does the Bucky make during an exposure?  Meters or indicators can display different readings depending dependi ng on the generator operatio operation.For n.For example, a meter might first firs t display a percentage of X-ray  tube load, then display the mAs obtained after an

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exposure. 14

 

 g. Routine maintenance pro gramme

To commence a routine maintenance mainte nance programme, the fo following llowing is suggested.  Where a quality control programme is to be established established,, ensure that all required procedures for routine maintenance are properly  documented.  Make a list of replacement parts or materials that may be required.  Be familiar with all operation modes of the t he equipmen equipmentt to be maintained.  Allocation of a specified specif ied time period to carry out maintenance. maintenance. This will depend on the patient workload, workload, and will need to be fflexible. lexible.  Record keeping. keeping. A separate logboo logbook k shoul should d be k kept ept for each room of  equipment. In the case of mobile or portable equipment, an individual logbook should be kept for each unit 

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h. Keepin g a lo gbook   The logbook logb ook may be of any conv convenient enient construct construction. ion.  The logbook should not confine entries to a single line. Leave space to provide full full detail detailss  If additional columns are required, the logbook may also cover the opposite oppos ite page  The logbook need not be hard bound, but instead be a collection of  report sheets kept in an insert folder. This can include the checklists, produced after routin routinee maintenance. Coloured divide dividers rs can separate each section.  A single logbook can contain all the required information for an X-ray  room. A separate logboo logbook k shoul should d be kept for a mo mobile bile generator generator,, or a portable system.  The front page page of the logbook should include all details of the equipment, (Make, (Make, model, serial No. etc.) etc.)  The logbook should also contain a list of all equipment manuals. manuals. This should include any reference reference numbers, to facilitate re-ordering of lost or damaged manuals.

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i. Routine maintenance modules

The equipment covered in the maintenance modules includes the following.  X-ray generator, generator, fixed f ixed installation.  X-ray generator, generator, mobile unit.  X-ray generator, generator, capacitor discharge. di scharge. 

 X-ray tube generator, stand.portable system.  X-ray tube.  Collimator.  The Bucky table and vertical Bucky.  Tomography attachment.  Fluoroscopy table.  Fluoroscopy TV systems.  Automatic film f ilm processor processor.. 

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X-ray generator,f ixed ixed installation y

A im im The aim is to provide information information and procedures for routine maintenance of an X-ray generator generator,, iinstall nstalled ed as a fixed installation in an X-ray department.

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a. Safety precautions Before removing any covers, ensure the generator is switched off, and the room power-isolation switch is also turned off.

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b.Visual b.Vis ual inspection of the control desk, power p ower off 

Check all knobs and switch switches. es. Where knobs have a pointer attached, check that the pointer aligns correctly at all positions of the indicated scale. Tip ip.. Check the pointer at full clockwise and counter clockwise positions of the knob. Look for possibl possiblee loose knobs, or for push button switches that might tend to stick.  If controls ha have ve had extra labels attached, are these labels l abels still required? If so, are they in good condition?  Older X-ray control controlss often have analogue meters instead of digit digital al displays. i. With power switched switched off, tthe he meter needle should be pointing at the zero calibration mark. ii. Most Mos t meters have a small adjus adjustment tment screw for zero calibrat calibration. ion. If  adjusting, adjust ing, fir first st tap gently in case the meter tends to stick. iii. Caution. Contact the service department before adjusting. In some cases, the meter may be deliberately adjusted off zero, as an incorrect method of calibration. 

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c. O perational inspection of the control desk, power on 

Check all indicator lamps. If necessary necessary,, operate differ different ent selection techniquess to ensure all indicato technique indicators rs operate correctly correctly....

i. Small focus / broad focus selection indication. On some controls, the mA 

selection switches ii. X-ray tube number, number, or positio position.. n.. iii. X-ray tube overload overload protection. Select high pre exposure factors, and check operation of the overload light. (On some controls with a microprocessor, the system might not allow selection of excessive output.) iv iv.. Automatic Exposure Control (A EC), or Photo Pho to timer timer.. When this opti option on is fitted, check that all chamber and station selection indicators operate operate correctly. .vi. Illumination Ill umination of kV kV,, mA, and ti time me selection.  Where a digital readout of selected values is provided, select a number of  different values to ensure there are no displ display ay errors, or missi missing ng segments of the displ display ay.. 

Older controls controls ma mayy have manual adjustmen adjustmentt of power line voltage, with a meter to indicate correct compensation. Check the range of adjustment. It should shoul d be possi possible ble to reset the voltage by 10%,above, or below, below, the require required d  voltage. 21

 

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d. X-ray tube overload protection  M aximum aximum radiographic

kV.

i. Select a short exposure time, and a low mA station. Increase kV setting setting till the exposure prevention, or inhibit, i nhibit, light operates. ii. The maximum available available kV should not exceed the specif specified  ied  kV for the particular X-ray tube. iii. In some cases, the available kV limit may be 10% less than the possible maximum. For For example, a 150kVp tube may be limited to 140kVp. 140kVp. This is a safety precaution, as 150kV is the maximum limit only when the tube is in excellent excellent condition. 22

 

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Minimum radiographic kV 

This will often be set 40kV, depending individual country  regulat regulations. ions. V Variati ariations onsatwill exist where anon interlock at the collimator is provided for different filters. i. Select Select a low mA statio station n and a short ex exposure posure time. Adjust Adjust kV towards the minimum available value. An exposure inhibit should occur if kV is too low low.. ii. Repeat Re peat this In test forcase, systems removable filter ter in theinhibit collimator. this withthat the have filteraremoved, anfil exposure should occur as kV is increased. (Depending on the system, this may be above 60kV 60kV.) .) iii. Note. Although the collimator will have the required minimum filtration for full operation, an additional filter f ilter,, typically 0. 0.5mm, 5mm, may  be inserted. This is an option, and does do es not require an interlock. iv iv.. On ol older der generators, especiall especiallyy those with stud stud,, or switch select selection, ion, and pre-reading kV meters, it may be possible to set kV below the safety requirement. requiremen t. Where this can occur occur,, provide a warning no notice, tice, and contact the service serv ice provider in case an upgrade is availabl available. e.

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Minimum kV for filament over-heat protection.

Refer to the rating charts, to see if a particular combination of high mA  and low kV should be avoided. This is to avoid overheating the filament during preparation. i. Selec Selectt the maximum availabl availablee mA stati station on and a short exposure time Reduce kV towards thebelow minimum kV availabl available. e. Eithervalue, the kVorwill be permitted to extend extend the minimum specified elsenot should shoul d cause an exposure inhi inhibit bit to operate. ii. As an example, the minimum kV with 5500mA 00mA selected may be 55 55kV kV,,  while if 400mA is selected, the minimum kV might extend down to 45kV. iii. Repeat for both focal iv. iv. N ote. This protection protec tionspots. may not be aavailab vailable le on older X-ra X-rayy controls. If a combination of high mA and low kV is possible, provide a warning notice. In some so me cases, an upgrade may be available from your serv service ice provider. In other cases, a re-allocation of available mA stations may be available. 24

 

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 A nod node maximum heat load load.

This is the maximum instantaneous instantaneous heat input to the anode. Note. The X-ray tube rating charts assume a cold anode. For this reason, so some me X-r X-ray ay controls de-rate the maximum output. This allows all ows for anode heat produced by previous exposures. For example, on over-table operation, output output m may  ay  be limited to 95% of maximum, maximum , while with a f luoroscopy ttable, able, this lim limit it be rreduced educed to around 70~80% of maximum ou output. tput.

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i. Select Select the appropriate anode-rating chart for the  X-ray tube in use. The anode speed is normally normally controlled controlled by the power frequenc frequencyy. Take care to select between 50 or 60 hz for low y

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speed operation, operat operation. ion. or between 150 or 180 hz for highii. In addition to anode speed, sele select ct either single or three phase operation, depending on the type of  iii.generator. If you have a high frequency generator, select the three-phase chart. This will still still apply if the generator generat or is supp supplied lied by single-phase single -phase mains mains power. power. 26

 

iv. iv. Note. The rating charts provide a family of curves. It is not required to use the same mA or kV for testing. For example, 0.1se 0.1sec c, 125 125kV kV & 360mA  is the same as 90 kV & 500mA.  v. On the rating charts, select suitable time periods. (For example. 0.02, 0.1, 0.3, 1.0, 5.0 seconds). At these time selections, determine a suitable mA station, and the maximum kV that can be used with that mA  selection. Adjust the kV towards this maximum value. The exposure inhibit should occur before this value is reached. Repeat this test for each of the pre selected time settings.  vi. Repeat this test for eeach ach mA station; together w with ith both ffine ine and broad focus spot selection.  vii.. Some X-ray controls  vii controls ma mayy have provis provision ion for both high and low speed operation. In these cases, the maximum load available for low speed operation, should not exceed exceed 85~90% of the value indicated in the low speed chart.

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e. mA calibration y

For this test, the X-ray control is required to display the actual mA, or mAs, resulting from an exposure.The control may have either an mAs meter, or a quick  acting mA meter.

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Microprocessor controlled systems sy stems have have an internal switch, which is i s set to calibration mode. This should sh ould only be adjusted adju sted on direct advice from the service department.

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 W hen hen the X-ray control

has an m A s meter:

i.  version, mAs meters may ofmaximum two types. reading T Type ype one ball ballistic istic.before With this watch forbe the onisexposure, the

needle returns retur ns to zero zero..

ii. The other version is a true integrating integrati ng mAs meter meter.. This type will hold the reading for a period of time, often while the preparation button is keptpeak the pressed needle at the defend deflection, lection, of exposure. and onlyWith record this thetype steady of meter, reading. ignore iii. mAs meters meter s may be dual ffunctio unction. n. In some controls, the meter will first indicate the % of anode load, and on preparation change o over ver to the mAs function. Another type first indicates the pre selected mAs, and on exposure indicates the actual mAs. Actual mAs remains displayed until preparation is released. iv iv.. When choosi choosing ng an exposure time, avoid uneven times llike ike 0.01, 0.03, etc. This avoids timer problems that can exist on older units. Select Select an exposure time of 0.1 second for easy calculation.

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 v.  v. T Test est mAs out output put using two kV posit positions. ions.V Values suggested are 60 kV and 90kV.Repeat 90kV .Repeat this test for all mA stations and foc focal al spots. spot s.  vi. modern The testequipment mAs outputwithin should5%. beVariations within 10%offor older systems, and in mA  mAs between adjacent stations should be less than 5%, including incl uding older designs.  vii. When preparation is complete, allow another half to one second before exposing. This is to eliminate possible poss ible errors due to incorrect of athe filament.  viii.pre-heating To check for possible filament pre-heating problem, select 60kV, and the largest mA  station. Make an exposure immediately preparation is completed, and record the mAs output.. Now mak output makee another exposure, but tthis his time wait for about one after preparation completed, make an5%, exposure. ix. second If the difference betweenisthe two tests then is more than contact the service ser vice depart department ment for advice. The generator shoul should d have the filament pre-heating adjusted, or else a small increase in preparation time.

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 W hen hen the X-ray control has a m A  m A meter meter only:

i. Select a low kV, between 60 and 70kV. ii. Make an assessment of tube loading with the selected mA station by selecting an exposure time of two seconds. iii. Assuming Assumin g a two second time would permit an exposure; now select a time of  0.81.0 second. This Th is time allows the mA meter to reach a steady reading, during the exposure. iv iv.. When preparation preparatio n is complete, allow another half to one second before exposing. This is to eliminate possible errors due to incorrect pre-heating of the filament.  v.  v. On exposin exposing,watch g,watch the mA meter mete r needle arrive at the expected value. Record the steady reading. (Ignore (Igno re any bounce or overshoot.) overshoot.)  vi. MA should be within 10% of the required value.  vii. Repeat this test on both b oth focal spots. spot s. Test Test only the mA stations stat ions that are well  within the anode load safety limit, at the exposure times of 0.81.0 second.  viii. Between test exposures, allow at least three to five minutes min utes for anode cooling. ix. To To check for a possible pre-heating problem, select 60 kV kV,, and th thee largest mA  station that th at was previously tested.Make an exposure immediately preparation is completed, completed, and record the mA output. If the change in mA is more than 5%, contact the service department departme nt for advice. The generator should have the preheating adjusted, or else a small increase in preparation time.

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 f. Radiation reproducib reproducibility tests, usin g a step-wed  ge 

This test should be carried out after the film processor has received its general maintenance.  Adjust the FFD to 100 cm.  Place the stepwedge on a 24/30cm cassette.  Several exposures can be made on the one piece of film. Place two pieces of lead rubber on top of the cassette, positioned aagainst gainst either side of the stepwedge. As the stepwedge is repositioned, the lead rubber prevents unwanted radiation entering the cassette.  Select a suitable mAs and kV combination, and make a total of four exposures. i. Allow about 0.51.0 sec second ond delay after prepara preparation tion is ccompleted, ompleted, before making each exposure. This is to ensure the filament has reached a stable temperature. ii. After each exposure, repositi reposition on the stepwedge and lea lead d rubber on the cassette. iii. Develop the film. fi lm. As tthe he exposure settings are the same for all exposures, the film should show vvery ery little variation. iv iv.. If necessary, change kV or mAs so the fil film m displays a good range of  densities, then repeat this test. 32

 

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Make another series of four exposures, using the t he same settings as before.

i. This preparation time, doisnot completed. delay the exposure, but expose immediately  ii. This is a test for filament pre-heating, or temperature stability.  Compare all eight exposures. If available, u use se a densitometer densitometer.. As the same output settings were used, the exposures should sh show ow very litt little le  variation. i. Iffilament the second group is or ligh lighter ter,, or darker darker, , than tthe he firs first group, the pre-heating preparation time should be tadjusted. Contact the service serv ice depart department ment for advice. ii. In case there is a general variation of densities in either group, this may  be due to power power mains voltage f luctuations. If suspect, repeat this test at a later time when power is more stable. iii. Variable output can be caused by a poor connection to the X-ray tube filament. This is due to a problem with the cathode high-tension cable,  where the cable-end plugs into the X-ray tube housing.  Repeat the test for each focal spot.  Record the settings used in the maintenance logbook for future use. Include which cassette used. Retain the test films for comparison with future tests. 33

 

 g. X-ray X-ray output linearity line arity test, usin g a stepwed  ge y y

This is an important important check on overall performance. By using a step wedge, wedge, a comparison comparison test may be made, not only between between the mA stations of the unit under maintenance, but but also with other units in the department.

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ato or, mobile unit X-ray generat y

A im im The aim is to provide routine maintenance procedures for a mobile X-ray generator. Within the mobile generator capa capabiliti bilities, es, a similar similar check is made as used for a fixed installation. Maintenance includes mechanical operation of the mobile, together with the  X-ray tube and coll collimator imator

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a. General precautions  B

 efore removing testing any connections, ensureany thecovers, system or is switched off,wires and or  unplugged from the power point.  Mobil Mobilee high-fr high-frequen equency cy generator generatorss may be battery operated. The batteries in these are connected in series, and may have a total voltage of up to 240V DC. Refer to the operating or o r installation manuals for the position of the battery isolation switch, and ensure this is switched off before removing any covers.  If the power plug has loos loosee conn connection ections, s, have an electrician check the plug. The plug may be assembled incorrectly.

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b. Visual Visual inspection of the control panel,  power off 

(Same as previous)

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c. Mechanical Mechanical and electrical ins inspection, pection, power off  fo r any any loose loos e panels or sections. Pay particular  Look for attention to the mounting of the collimator.With collimator.With a screwdriver screwdriv er,, check for possible possib le loose screws, particularly  p articularly   with the tube support arm and the vertical vertical bearing tracks. X-ray tube set to minimum height, check the  With the X-ray  vertical suspension sus pension wire rope for possible broken strands.CAUTION, with and a instead test by rubbing rubbdo ingnot thetest cables upbare andfingers, down using piece of cloth. clo th.  Check the action of the tube-stand bearings. Are there any   visible  visib le gaps between the bearings beari ngs and the track surface?

 Also arewhich noises or jerking moved, wthere hich any can clunking indicatedamaged bearings. bea rings. when bear ings with a light  Spray the tube stand tracks and bearings aerosol lubricant.Wipe lubricant. Wipe down afterward, afterward, so onlya very very small film is left on the tube stand tracks.

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Check for possible loose lock l ock handles, and ensure manually operated operated locks have an adequate range of adjustment. adjust ment.

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Ensure

the mobile mobile brakes operate in a positive fashion when the hand is released from the handle, and that they are fully released while the mobile is travelling.

Pay particular attention to the cabling from fro m the Xray tube and tub tubee stand. All movements of the system should not cause any stress or pulling of the cables. Inspect the HT cables for any sign of damage to the safety earth shield at the X-ray tube cable ends. Ensure the cable ends are firmly inserted into the X-ray tube, and the securing ring nut is not loose.

 Where there is evidence of twisting or pulling on the HT cables, particularly at the X-ray tube end, investigate means of providing additional support. If necessary necessary,, discuss with the ser service vice de departmen partmen

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plugs and sockets attached to cable ends.The outer insulation insulation of cabl cables es should not be pulled out from the cable clamp.  Check the condition of the power cable. If necessary, remove the plug cover,, and ensure terminat cover terminations ions are tight, and no connections connection s are stretched or have broken strands. S Should hould tthe he cable exhibit excessive twisting, twistin g, or ha have ve cracks in the outer sheath, ask an el electric ectrician ian for to

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Examine carefully carefully all

replace the les cable orbattery plug. operated power assistance should have the Older mobi mobiles with battery electrolyte level checked. i. Ensure first firs t that the power cable is unp unplugged lugged fro from m the pow power er point. ii. To To gain access to the b battery attery,, refer to th thee operation or ser service vice manual. iii. Top Top up with ei either ther disti distilled lled water or else fres fresh h rainwater rainwater.. iv. Later systems use sealed or low maintenance batteries. This includes high-frequency mobile gener generators. ators. 

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d. O peration inspection of the control panel, power on 

Check all indicator lamps etc. If necessary necessary,, operate differe different nt selection techniques to ensure all required requi red status iindicato ndicators rs operate correctly correctly..

 Where a digital readout of radiograph settings is provided, select a number of different di fferent values to ensure there are no display errors or missing segments.

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Older controls controls ma mayy have manual adjustmen adjustmentt of power line voltage, with a meter indicating indicat ing correct compensati compensation. on. Check th thee range of  adjustment. adjust ment. It should be possible possib le to reset the voltage by 10%, above or below,, the requ below required ired voltage.

 With battery-operated battery-operated equipment, check the status of the battery  charge indicator. If low l ow,, pl place ace the unit on charge, and check that after a reasonable time the system indicates fully charged.This time should not be greater than an overnight perio period. d.

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e. Mechanical and electrical inspection, power  on locks. ks. There  Test operation of the electromagnetic loc should be b e no hesitation in operation, nor should the lock stick on. In some cases the surface of the lock may require cleaning, to obtain a better grip

 With power assisted mobile mobiles, s, check for correct operation in all forward and rev reverse erse modes. Where

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there is an anti-crash bumper bumper, ma manually nually operate the bumper. This should stop ,motor drive. (Do NOT test by standing in front while the unit is moving forward)

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 f. X-ray tube and collimator 

Inspect the X-ray X-ray tube housing for possible possib le oil leaks.  When in i n preparation, listen for excessive X-ray X-ray tube bearing noise. timer.  Check the operation of the collimator lamp timer.  With mechanical timers, listen for possible sticking of the t he clockw clockwork. ork.  Check the alignment of the c collimator ollimator lamp and  X-rayy beam. This should be check  X-ra checked ed through 180 1 80 degrees rotation of the collimator. collimator. 

The collimator collimator has a scale associated associa ted with the adjustment knob to indicate the field size.The knob can slip on the shaft, or not be correctly positioned after replacing a collimator globe. 

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To test the rotation accuracy of the light beam; i. Rotate the collimator 90 degrees in either direction. ii. With the light on, open the collima collimator tor so an average av erage size ffield ield is projected on the tabletop. For example, a 24/30 cm cassette cassette size. iii. Place Place markers tto o indicate indi cate the light beam position. iv.. Now rotate the colli iv collimator mator 180 degrees degrees in the the opposite opposi te direction. The light fi field eld should be  within 1% or better, compared to the previous position. 

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X-r r r, r ay gene ato capacito rge mobile discha y y

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A im im The aim is to provide routine maintenance procedures

for a capacitor discharge (CD) mobile generator.  Within the CD mobile capabilities, capabilit ies, a similar check is made as for a conventional mobile. There are however, some important impor tant differences. These relate to the nonlinear output due to the kV/mAs relationship, plus plu s other modes of operation. operation. Maintenance includes mechanical operation of the CD mobile, together with the X-ray  X-ray  tube and collimator

45

 

a. General precautions 

Before removin g any covers, or testin g any wires or 

connections, ensure the system is switched off, and  unplu gged from the power point.

loose connections, have have an electrician check the plug. The plug may be assembled incorrectly. 

t he pow power er plug has If the

Do NOT make any ad  justments to the HT cables  without first dischar  gin g the capacitor capa citor.. 

46

 

b.Visual inspection of the control panel, power off 

CD mobiles have an analogue kV meter  instead of a digital display. With power off, the meter needle should be on the zero zero calibration mark, providin g the capacitor is fully dischar  ged . If not, first f irst tap gently gently in case the meter tends to stick. Do not attempt to ad  just the meter zero position  without reference reference to the service ser vice manual, and  operation of the internal capacitor dischar  ge device. 



Older

O CDshould mobiles may have line voltage meter. Thisther meter read zero onapower off. If necessary, the meter zero position may be adjusted by the centre screw. Tap the meter gently first, to ensure the meter is not sticking.

47

 

c.  M echanical echanical and electrical inspection,  power off  y

(SA ME  )

48

 

d. O perational inspection of o f the control panel, power on

Check all indicator ind icator lamps operate.  For CD mobiles equipped with an analogue or digital kV  meter, test the kV adjustment for correct operation.



i. Set Se t the required required kV to 60kV and press the charge charge button. ii. The charge charge light should illuminate. Once the required kV  is reached, then the ready lamp should light li ght up. up. iii. Check that the kV displayed on the meter closely agr agrees ees  with that indicated at the Kv control knob. iv. Observe the kV meter for a few minutes. The kV should slowly drop drop back by about 2~3kV 2~ 3kV,, then return brief ly to the charge mode. (This is called topping up)

49

 

 v. Increase the set kV to 90 kV. The charge light should illuminate, until the kV meter reaches 90kV.  vi. Now reset the required kV back to 60kV. The X-ray ON light should illuminate. At the same time the indicated kV  should quickly qui ckly drop down to the required value.  vii. Note. A low mA X-ray exposure is produced when the kV  is reset. Radiation Radiati on is blocked in this mode by a lead shu shutter tter in the collimator coll imator..  viii. In case the th e kV resets very slowly s lowly,, similar simil ar to discharge discharge prior to topping-up, this can indicate ind icate a problem. problem.

50

 





Some CD mobil mobiles es hav havee an adjustment adjustment for power linee voltage. lin Am meter eter indicates indicofates whenent, theto voltage is correct. Check the range adjustm adjustment, ensure compensation may may be set approximately 10% above or below the required voltage. Note. The

power line voltage adjustment can directly direct ly affe affect ct the kV charge on the capacitor capacitor..

 With motorized mobiles, mobil es, check the status of the battery charge indica indicator tor.. If low low,, pl place ace the unit on charge. charg e. Charging time should not be great greater er than an overnight period.



51

 

 g. mAs calib calibration 

Note. This

only applies to mobiles fitted with an mAs control, and a kV meter meter..  A CD mobile has a direct relationship of mAs and kV.. During an exposure, kV exposure , the kV will dro drop p by one kV  per mAs. (This is for a one microfarad mobile) 

Ensure

the collimator is fully closed. Select 90 kV and 20mAs  Once charging is completed, make an exposure, observing obser ving the kV meter meter.There .There should be a drop from 90kV to 70kV 70kV.. 



(In somefrom cases small smaller er. drop ofdue kV may occur. occur. For example, 90ato 72 72kV kV. This is to capacitor manufacturing tolerance.)  Select several other combinations combinations of kV and mAs and repeat the above test.

52

 

X-ray generat ato or, portable unit  A im im The aim is to provide routine maintenance for a portable X-ray generator.Within the portable generator generat or capabilities, capabiliti es, a similar check is made as for a mobile mobile generator The portable port able generator generat or may be either self rectified rectif ied or else

full wave rectif rectified. ied. The stationar st ationaryy anode X X-ray  -ray  tube and HT transformer are contained contained in a single housing. Maintenance includes mechanical operation of the portable, together with the X-ray tube and collimator.

53

 

 A im im The aim is to provide routine maintenance for a portable X-

ray generator generator.Within .Within the portable port able generator capabilities, capabiliti es, a similar check is made as for a mobile generator The portable generator generator may be either self rectified rectifi ed or else full  wavee rectified.  wav rectified . The stationary statio nary anode X-ray tube and HT transformer are contained contained in a single housing. Maintenance includes mechanical operation of the portable,, together with the X-ray portable X-ray tubeand tub eand collimator. collimator.

54

 

a. General precautions  Before removin g any covers, or testin g any wires or connections, ensure the system is switched off, and unplu gged from the power point. power plug has loo loose se , hav have e an  If the power

electrician the plug. The plug may be assemblecheck d incorrectly.

55

 

b.Visual inspection of the control panel,power off   Check all knobs and switches  Where extra labels have been attached, are these labels still relevant? often ten have an analog analogue ue linevol linevoltage tage  The generator will of and mA meter meter.. These me meters ters should rea read d zero on power off.

56

 

. O peration inspection of the control panel,  power on indicator lamps operate in each mode of   Check all indicator operation. adjustme djustment nt of line voltage, to  Check the range of a ensurethe thisoptimum may be set approximately 10% ab approximately above ove or below position.

57

 

. X-ray tub tube head and collimator   Look for possible oil leaks. operation of the collimator lamp timer. timer. (If   Check operation fitted)  With clockwork lamp timers, check for possible sticking of the clockw clockwork ork  To test the alignment of the X-ray to the light beam;

58

 

 f . mA calibration 

Depending on system design, ma selection may be linked to the kV knob. Other units may have an independent selection of mA. collimator is fully fu lly closed.  Ensure the collimator  Select 60kV and the maximum associated mA station. Select an exposure time of 1.0 second.  Commence preparation, preparation, and expose when preparation is complete. Observe Obs erve the mA meter, meter, and record the indicated ind icated  value. 

Repeat test for all other mA and kV combinations. Record Recor d this the t he results. m A on any position has an error of more than 10%,  If mA recalibration is required.

59

 

X-ray tube-stand  A im im The aim is to provide routine maintenance maintenance procedures for the X-ra X-rayy tubetube-stand, stand, or suspension. T The he instructions provided provided are are for the floor f loor ceiling tube stand . Most of these procedures can also be applie applied d to a ceiling mounted tube suspension.

60

 

a. General precautions y

lectrical ical safety sa fety.. Electr

In most installations the tube-stand power will come from the generator generator,, but in some installations, installati ons, swi switching tching off the generator does not remove power from the tube stand. y

Before removing any covers, covers, ensure the generatoris switched off, and the room power power isola isolation tion switch is also turned off.

61

 

b. Mechanical and electrical electrical inspection  Inspect for any loose panels or sections. Pay particular

attention to the collimator and the control panel. s uspension, tracks tracks and bearings.  Check the tube-stand suspension, i. With the X-ray X-ray tube set to minimum height, check the  vertical suspensio sus pension n wire rope for broken strands.CAUTION, doand not down test with bare ffingers.T ingers.Test est by  rubbing rubbi ng the cables up with a piece of rag. ii. With the vertical lock lo ck released, the X-ray X-ray tube should balance in the vertical direction. It should need the same effort to move either up or down.

62

 

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lateral centre

Laterall centring Latera centring over over the Bucky table should be check checked ed in both directions. Infrom someone cases th this is may be accurate accurate only   when approached direction. i. Tape a thin piece of wire, or a paper clip, to the centre of a 24/30cm cassette. Place the cassette in the Bucky. ii. Position Positio n the X-ray X-ray tube to to the lateral centre positi position. on. iii. Adjust Adjus t the table top also to the lateral centre position. positi on. iv. Bring the collimator face to rest on the tabletop, and ensure it is flat f lat against the tabletop. Then rise to 100 cm S.I.D.  v. As the collimator moves away from the tabletop, check that the light beam remains central central to the tabletop. If not, adjust the tube angle a small amount so the light beam remains in position.

63

 

Tube stand command arm, or panel   The X-ray tube trunnion-ring rotation-lock should operate firmly f irmly,, and prevent unwanted rotation.  Hand grips should not be loose. sho uld rotate smoothly smooth ly,,  The indicator for tube angle should and not hesitate before changing its position.

Check all indicator lamps and switches swi tches for correct correct operation.  Check alignment of the Bucky centre light. (When fitted.)



64

 

X-ray tube y

A im im The aim is to provide routine maintenance procedures for the X-ray X-ray tube.This incl includes udes techniques to imp improve rove the high-voltage performance or reliab reliability ility of the X-r X-ray  ay  tube.

65

 

. General precautions  Before disconnecting any wires, or removing a cover, always ensure power is turned off and unplugged from the power point. If the equipment is part of a fixe fi xed installation, besides switching the generator power power off, ensure th the e isolation isola tion power switch for the room is also switched off.  During the seasoning technique, make sure thecollimator is closed. Aim the X-ray X-ray tube away from the  X-ray control.

66

 

 X-ray  X-r ay tube inspection Check rotation of the X X-ray -ray tube in the trunnion rings. The locking device should hold the housing firmly fi rmly in place, but allow free rotation on release. command arm  Ensure no attachments, such as a command control panel, or collimator, have become loose.  Examine electrical cables cab les to the X-ray X-ray tube. Ensure they are are securely clamped into position, and not n ot subject subje ct to to being pulled. pu lled. Where cables pass into the housing, they should sho uld be protected from sharp edges.  Inspect the HT cables for fo r any any sign of damage to the safety earth shield, shiel d, at the X-ray X-ray tube cable ends. 

67

 



Ensure

the HT cable ends are are ffirmly irmly inserted iinto nto the  X-ray tube, and the securing ring nut is not loose. twi sting or pulling on the  Where there is evidence of twisting X-ray tube receptacle, HT cables, particularly at the X-ray investigate means of providing additional support. 

E

xamine the X-ray X-ray tube housing hous ing for any oil leaks.  At the generator, go into preparation, then release preparation without exposing. Listen Lis ten to the anode rotation for excessive excessive noise. nois e. 

68

 

 X-ray tube seasonin g  This is also called ageing, and is a process to reduce residual gas in the X-ray X-ray tube. Seasoning S easoning improves the stability stabilit y of the tube, tub e, when operated at high k kV V. Seasoning ing should always be performed if i f a new X ray  ray   Season

tube is installed, or has not been used for more than one month. The same applies where the tube has not been used us ed over over 80~90kV fo forr some time, and then it is desired to use 110 kV or higher.

69

 

If using us ing an X-ray X-ray tube of 125 kV capacity at 110kV  or higher, higher, seasoning seaso ning should shou ld b bee performed each day  prior to use. If I f the tube t ube is rated at 150kV, 150kV, the same applies if operating ab above ove 125kV. 125kV. sea soning, an X-ray X-ray tube may at first appear  During seasoning, 

Unstable . After Af ter tw two o to three exposures , the tube should now be stable.

70

 

y y y y y y y y y y

y y y y

Table =Seasoning technique techniqu e for a 150 150 kVp X-ray tube Step kV mAs Times Pause Pause time

1# 2# 3# 4

60 20 70 20 80 20 90 20

2 2 2 2

40 40 40 40

5 6 7 8

100 20 110 20 115 20 120 20

2 2 2 2

40 40 40 60

9 10 11 12

125 20 130 10 135* 10 140** 10

2 4 4 2

60 60 60 60

71

 

y

Note

i. The majority of mobiles provide selection of mAs only.. If mA and time selection is available, then only t hen aim for exposure times less than 0.3sec. ii. # Steps 1,2, and 3 are only required if the tube is just installed, instal led, or has not been in i n use for more than one month. iii. * If, for example, you never use above 110kV, then ignore steps 8 and 9.

72

 

X-ray collimator

y

A im im

The aimX-ray is to collimator. provide routine for the collimator . Thesemaintenance maintenanceprocedures suggestions are for a standard collimator used on a standard tube-stand.

73

 

a. General precautions  W henever henever changing a collimator collima tor lamp, always ensure power is turned off and equipment unplugged from the power point. If the equipment is part of a fixed  installation, besides switching the generator power power off, ensure the isolatio iso lation n power switch for the room is also switched off.

74

 

General maintenance  Check electrical cable to the collimator. Ensure the cable entry is i s protect protected ed against agai nst sharp edges of  the collimator collimator housing. hou sing. Rotation of th thee collimator collimator should not stretch or pull the cable. 

Check the operation of the collimator blades.These should stay in position when adjusted, and not slip if the X-ray tube is repositioned. If adjustment of  the clutch or brake is required,

75

 



Check the operation of the collimator blades.These

should stay in position when adjusted, and not slip if the X-ray X-ray tube is repositi repositioned. oned.  Check the operation of the collimator lamp timer. timer.  With clockwork systems, look for possible sticking of the mechanism.  E  valuate the intensity of the light beam from the collimator.  Check the type of globe fitted.

76

 

The following precautions should be observed if  changing the globe. nsure power to the  generator and/or tube i. E nsure stand is turned off. ii. If a globe has just jus t failed, wait for it to cool down. iii. When unpacking and inserting a new globe, do not handle it directly. Instead use a tissue or a piece of cloth so your fingers do not touch the globe. This is very important when handling Quartz-Halogen globes. 

77

 

c. Alignment tests  Check the crosshair alignment of the front transparent cover. i. With the collimator collimator bl blades ades almost closed, the crosshai crosshairr should be in the centre of the light field. Check at both horizontal and vertical settings. ii. If adjustment ad justment is i s required, required, on most mo st collimators, collimators, the cover cover may be moved moved after loosening th thee four retaining screws. s crews. (In some cases, the cover cover may at first fi rst stick in i n place.)  Check the Bucky centre light, if fitted. If out of alignment.

78

 



The collimator has a scale combined with the knob kno b to

indicate the positioned fie ld field size.The kno knob b can slipa collimator the shaft, or not be correctly correctly pos itioned after replacing con ollimator globe.  To test the alignment of the X-ray to the light beam; i. Place the X-ray alignment template on a 24/30cm cassette. ii. rectangle. Collimate the light li ght beam to the outer 20 by 26cm iii. Make a low KV and mAs exposure. iv.. Develop the film. iv  v. In many cases the collimator is enabled to rotate. Repeat the above above test, with the t he ccollimator ollimator rotated 90 degrees clockwise, and then 90 degrees counter clockwise.

79

 

Bucky

table and vertical Bucky

y

A im im  Aim is to provide routine maintenance procedures for the Bucky table table and vertical Bucky Bucky..

80

 

General precautions  Before removing a cover, always switch the generator power off, and ensure the isolation isol ation power witch for the room is also switched off   When removing the cover from a vertical Bucky, make sure the Bucky cannot move upwards when the cover is removed. remov ed. For example, attach a rope to to hold it in position, or remove the cover with the bucky set to maximum height.  Keep all screws, or other small parts in i n a container, container, to avoid loss.

81

 

b. Bucky table  Examine the physical condition condition of the table. Clean Clea n the remains of adhesive tape etc from the table body.  Check for loose screws on the tabletop profile rails. The rails can become loose loo se due to using a compression device. 

E

xamine theect condition conditio n of the compression Check for correct corr operation. Remove Remov e the banddevice. from the mechanism, and have have it laundered. ind icator lamps.  Check the operation of switches and indicator

82

 

 With an elevating Bucky Bu cky table, use us e a tape measure to check the ttable able height at the centre stop position.  Check the operation of the magnetic locks. Note. Some movements may have two or more 

magnetic locks. Carefully observe these locks and ensure all locks are actually in operation.  Check the operation of the tabletop lateral centre stop.  Where this is mechanical, the spring tension may need adjustment. In case of operation by the magnetic locks, the stop position is normally controlled by a microswitch .  Adjustment  Adjust ment of this microswitch can control the width and position of the centre-stop operating position.

83

 

c. Potter Bucky Movee the Bucky to both ends of the t he table. Check  Mov that the Bucky carriage operates smoothly smo othly,, and that the Bucky lock operates correctly correctly in all position po sitionss across the table.  Electrical cables to the Bucky should be firmly  attached at the Bucky, Bucky, and no n o twisting or puling occurs on the cable, at any position positi on of the Bucky. Bucky.  Where there is a folding foldi ng support suppo rt arm for the connecting connecting cable, look l ook for possible possib le binding or ex excessive cessive droop. This can indicate loose mounting screws.



84

 

Spray the Bucky track with a light aerosol lubricant, lubrican t, and then wipe wip e the residue from the track.  Remove the Bucky tray. With a torch, examine the Bucky interior for lost film f ilm markers. fo r loose screws holding hol ding the tray handle. Take Take  Look for



care not to over-tighten, as this might damage the thread.  Test the action of the Bucky tray cassette clamps. They  should hold the cassette firmly .

85

 

Test the grid os oscillation. cillation. i. At the generator, select the lowest mA station, 50kV, and exposure time of 1~2 seconds.



E

ii. away nsure thethe collimator collimator is closed, anan d the tube iswith positioned positio from Bucky. Then makeand exposure the ned Bucky selected. iii. During the exposure, check for smooth operation of the grid. iv. Watch for any shaking, or vibration of the Bucky, as the grid reverses its movement. Or else, just as the grid first starts to move.  v.. S  v Should hould shaking s haking or o r vibration occur, occur, this can cause reduced

sharpness of the radiograph. If this occurs, contact the service serv ice department for advice.  

d.Vertical Potter Bucky  The vertical vertical Bucky should be checked checked in the same manner as the table Bucky, Bucky, but bu t with the following provision for retrieving lost film markers. These markers can fall into the motor section at the bottom of the Bucky Bucky,, and may cause a problem. problem.

86

87

 

Fluoroscopy table a. General precautions  Before removing any cover, always switch the generator power off, and ensure the isolation power switch for the room is also switched off. cover,, or disma dismantling ntling any section, place the  If removing a cover screws in a container to avoid loss.

88

 

b.  M echanical echanical and electrical inspection  Make a general inspection ins pection of the table body and serial-changer serialchanger.. Tighten Ti ghten any loose screws, or panels and fittings f ittings.. t he tabletop in place.  Check the rails holding the Tighten any loose screws.  Examine all suspension system cables and chains for any sign of wear, or uneven tension in the case of dual systems.

89

 



Check electrical cables, particularly par ticularly at the rear rear of 

the table. Pay special attention to cables that th at may  be twisted or tangled. It may may be necessary necessar y to removee existing cable ties, reposition remov repos ition the cables, and then install fresh cable ties. (Use plastic or nylon cable ties only)  Where electrical cables enter the table, check that the cable clamps properly secure secu re them.The protective outer insulation of the cable should not be pulled back, exposing inner conductors.  The footrest requires careful attention. If there is any tendency for the locking mechanism to slip, this

 will require urgent correction. 90

 

c. O peration test, table body  Check operation of all locks.Thelock should operate quickly when operated,and not stick on when when released.  Check all switches swi tches and indicator lamps lamp s for correct correct Operation . This especially includes i ncludes thos thosee on the table body,, which may be damaged by patient trolleys. body pos itions. Listen Li sten for any  any   Operate the tabletop in all positions. unusual squeaks or bearing rattles. 

On tabletops fitted f itted with a lateral centre stop, the stop position should be checked. it tend to continue or coast coast for fo r a shortwhile? shortwhil e? This could indicate a failure of the motor m otor brake system.

91

 

Rotate the table to the vertical and Trendelenburg positions. Listen for unusual bearing or motor noise while the table is rotating. rotati ng. Does the table tab le stop quickly after the rotation control is released, or o r does  The table should stop in the horizontal position, on returning from f rom the vertical position. pos ition. Use a spirit level to



check the horizontal position. posi tion in either  With the table tilted at maximum position direction, check the electrical cables are not pulled tight..  Some tables have power assistance for movements, this

should be smooth and free from sudden jerks. 92

 

Some tables have safety anti-crash bars or flaps. Pushing against again st these safety devices should prevent the table from rotating.  With the vertical or compression lock on, operate the tabletop longitudinal movement. On some y

y

tables, movement should not operate, and on others, the vertical lock should release on movement of the tabletop.

93

 

Fluoroscopy

TV

a. General precautions  Before removing any cover, always switch the generator power off, and ensure the isolation power switch for the room is also switched off.  Do not remove the cover of the TV monitor. Dangerous  voltages can exist for a considerable time ti me after the monitor is switched off.  Do not attempt any any adjustment adjustmentss to the TV camera,unless under instruction by the service department. cover,, or disma dismantling ntling any section, place the  If removing a cover

screws in a container to avoid loss. 94

 

 Mechanical and electrical inspection, TV  Mechanical T V system  Electrical cables should be securely attached to the monitor trolley. trolley. There should shou ld b bee no possibility possib ility of  pulling against cable connections. This also applies in case of wall mounted plugs and sockets. 

Examine

the video cable connection, both at the monitor and TV camera. The cable should be firmly f irmly attached attached to the plug, including the outer earth shield. Moving the cable at the plug should not no t cause any flicker f licker or change in the TV  image.

95

 

Image sharpness  An evaluation of image sharpness or focus is best carried out with a Line pair gauge. gau ge. The industry industr y standard is one made from 0.1mm lead. Tape the gauge onto the centre of the input face of the image intensifier. To avoid interaction with grid lines, attach the gauge so it is rotated approximately 25~45 degrees. (On ( On some CCD TV  cameras, this also avoids avoids interaction between pixels.) If the t he system has automatic automatic kV control, this should be be

y

y

y

turned off. Set manual fluoroscopy kV to 50~55kV. 96

 

y

y

y

 With fluoroscopy on, adjust kV or mA to obtain a normal brightnesss and contrast image on the monitor. brightnes monitor. Carefully observe the line-pair patterns. The limiting definition is the line pair group that isreasonably visible,  while the next group is completely completely blurred blu rred out. (This can sometimes be a good test of individual eyesight.) Record Rec ord the line pair resolution resolutio n

97

 

 Automatic bri ghtness/kV control  

 Automatic brightnes brightness adjusts the TV image as different sections of anatomy are ares examined.  Automatic brightness normally controls the fluoroscopic output, either by kV or mA, or else a combinati combination on of both kV and mA. Older methods operate by direct compensation in the TV camera only. Current systems often use a combinati combination on of both methods.

98

 

y

y

y

Place a plastic bucket or container container with about 3 .0 cm water on the table top.  With fluoroscopy on, the image on the monitor should be a normal brightness level. If automatic control is by kV only, or mA only, this may not provide complete compensat compensation. ion. If the image has exc excess ess brightness, b rightness, it i t may be necessary to reset the manual adjustment.