Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 7620-3 (1991): Medical electrical equipment - DiagnosticX-ray equipment, Part 3: Radiation safety requirements [MHD19: Immuno-Biological Diagnostic Kits]

IS 7620 ( Part 3 ) : 1991

Indian StandardMEDICAL ELECTRICAL EQUIPMENT -

DIAGNOSTIC X-RAY EQUIPMBNTSPART 3 RADIATION SAFETY REQUIREMENTS

( First Reprint AUGUST 1997 )

tiDC 621’386’1 : 614’876: 616-073

0 BIS 1991

BUREA?U O F I N D I A N S T A N D A R D SM A N A K B H A V A N , 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

December 199 1 Prke Group 4

Electromrdical Equipment Sectional Committee, MHD 19

FOREWORD*

This Indian Standard ( Part 3 ) was adopted by the Bureau of Indian Standards, after the draftfinalized by the Electromedical Equipment Sectional Committee had been approved by the MedicalEquipment and Hospital Planning Division Council.

This standard ( Part 3 ) specifies exclusively the requirements for radiation safety in the use ofdiagnostic medical X-ray equipment. Other parts of this standard are:

Part 1 Mechanical and electrical safety requirementsPart 2 Performance requirements

The Atomic Energy Regulatory Board ( AERB ), constituted by the Government of India inNovember 1983, is entrusted with the responsibility of developing and implementing appropriateregulatory measures aimed at ensuring radiation safety in all applications involving ionizingradiations. Before the constitution of AERB, the division of radiological protection of the BhabhaAtomic Research Centre and the Safety Review Committee of the Department of Atomic Energywere responsible for the implementation of safety provisions envisaged in the Atomfc EirergyAct, 1962.

In preparing this standard, assistance has been derived from the following documents :

a) IEC Pub 407-( 1973 ) - Radiation protection in medical X-ray equipment, 10 kV to 400 kV(first edition ). International Electrochemical Commission; and

b) International CommZssion on Radiological Protection (ICRP) - Publication 33 - Protec-tion against ionizing radiation from external sources used in medicine.

For the purpose of deciding whether a particular requirement of this standard is complied with,the final value, observed or calculated, expressing the result of a test, shall be rounded off inaccordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( revised )‘. The number ofsignificant places retained in the rounded off value should be the same as that of the specified valuein this standard.

Indian StandardIS 7620 ( Part 3 ) : 1991

MEDICAL ELECTRICAL EQUIPMENT -DIAGNOSTIC X-RAY EQUIPMENTS

PART 3 RADIATION SAFETY REQUIREMENTS

1 SCOPE

1.1 This standard ( Part 3 ) specifies the mea-sures for radiation safety of diagnostic X-rayequipment uved in medical practice by personshaving adequate knowledge and understandingof radiation hazards and protection.

1.2 This standard does not apply to dentalX-ray equipment.

2 TERMINOLOGY

2.1 For the purpose of this standard. the follow-ing definitions in addition to those given in Part1 of this standard, shall apply.

2.2 Accessible Surface

The external surface of X-ray tube enclosure orhousing provided by the manufacturer.

2.3 Aluminium Equivalent

In respect of a material under specified condi-tions, the thickness of aluminium that underthose conditions, affords the same attenuationas that material.

2.4 Assembler

Any person engaged in the business of assembl-ing, replacing or installing one or more com-ponents into an X-ray equipment or sub-system.

2.5 Attenuation

A decrease in radiation intensity caused byabsorption and scattering in a medium.

2.6 Automatic Exposore Control

A device which automatically controls one ormore technique factors to obtain at a pre-selec-ted location(s), a required quantity of radiation.,

2.7 Beam Axia

A line from the source through the centres ofthe X-ray fields.

2.8 Exposure

The quotient of dQ/dm where dQ is the absolutevalue of the total charge of the ions of one signproduced in air when all the electrons ( nega-trons and positrons ) liberated by photons in avolume element of air having mass dm arecompletely stopped in air.

1

2.9 Field Emission Equipment

Equipment which uses an X-ray tube in whichelectron emission from the cathode is due solelyto the action of an electric field.

2.10 Filter

A layer of radiation attenuating material incor-porated in the tube housing to preferentiallytibsorb the less penetrating components of theuseful beam; ‘permanent filter’ is an integralpart of the tube housing and cannot be removedby the user unlike the ‘added filter’.

2.11 Fluoroscopic Imaging Assembly

The assembly of components comprising of thedevice in which X-ray photons produce afluoroscopic image and include as appropriatethe fluorescent screen image intensifier, equip-ment housing, electrical interlocks, primaryshielding and structural linkage between imagereceptors and diagnostic X-ray tube assembly.

2.12 Half Value Layer ( HVL )

The thickness of specified material which whenintroduced in the path of radiation beamattenuates the beam of radiation to one-halfof its original value.

NOTE -In this definition, the contribution of allscattered radiation other than any which might bepresent initial1 y in the beam concerned, is deemedto be excluded.

2.13 Image Receptor

Any device, such as, fluorescent screen orradiographic film, which converts incident X-rayphotons either into a visible image or intoanother form which can be made into a visibleimage by further transformations.

2.14 Kerma

The energy transferred ( per unit mass ) bygamma rays, X-rays or neutrons in the form ofkinetic energy of secondary charged particles atthe point of interest in an irradiated medium.If the irradiated medium is air, the correspond-ing kerma is called air kerma. The SI unit ofkerma is gray.

2.15 Lead Equivalence

Thickness of lead which under specified condi-tions of irradiation affords the same attenuationas the material under consideration.

IS 7620 ( Part 3 ) : 1991

2.16 Leakage RadiationRadiation emanating from the diagnostic sourceassembly except for the useful beam.

2.17 Leakage Technique FactorsThe technique factors associated with the tubehousing assembly which are used in measuringleakage radiation.

2.18 Light Field

The area of light in the plane of the imagereceptor that is directly outlined by the beamlimiting device, the perimeter of which is thelocus of points at which the illumination is one-fourth of the maximum in the plane of theimage receptor.

2.19 Mobile EquipmentTransportable equipment designed to be movedfrom one location to another, between periodsof use, on its own wheels or similar means ofsupport.

2.20 Portable EquipmentThe equipment intended to be moved from onelocation _to another or between periods of rusewhile being carried by one or two persons.

2.21 Primary Protective BarrierThe material excluding filters placed in the use-ful beam and incorporated into the equipmentby the manufacturers to- reduce the radiationexposure to the medical personnel duringoperation.

2.22 Radiation Protection

Measures taken to minimiz: exposure topatients, medical and para-medical staff andgeneral public so as to limit the bidogical conse-quences of ionizing radiation to acceptablelevels.

2.23 Radiation Tberapy Simulation System

A diagnostic type X-ray system intended forlocalizing the volume to be exposed duringradiation therapy and confirming the positionand size of the therapeutic irradiation field.

2.24 Rated Tube Current

The maximum allowable tube current of theX-ray high voltage generator.

2.25 Rated Output Voltage

The maximum allowable p:ak potential in voltsat the output terminals of the X-ray tube.

2.26 Safety

Safety means radiation safety and does notinclude electrical/mechanical and other safetyconsiderations.

2.27 Scatter

Scatter or scattered radiation means radiationscattered by the medium on which the primarybeam is incident.

2.28 Source

The focal spot of the X-ray tube.

2.29 Source Image Receptor Distance ( SID )

The distance from the source to the centre of thesurface of the image8 receptor on which X-raystransmitted ~by the patient are incident.

2.30 Useful Beam

Useful beam or primary beam is the part of theemergent radiation from an X-ray tube housingwhich is capable of being used for the purposefor which the X-ray equipment is intended.

2.31 Variable-Aperture Ream-Limiting Device

A beam limiting device which has capacity forstepless adjustment of the X-ray field size at agiven SID and is provided with an opticalsource for light field.

2.32 X-Ray Field

The area of the intersection of the useful beamand any one of the set of planes parallel to andincluding the plane of the image receptor whoseperimeter is the locus of points at which theexposure rate is one-fourth of the maximum inthe intersection.

2.33 X-Ray Tube

Any electron tube which is designed for theconversion of electrical energy into X-rayenergy ( henceforth termed ‘tube’ ).

3 MARKING

3.1 The provisions of Part 1 of’ this standardshall apply.

.3.2 In addition, the equipmen~t shall bear themarkings of a warning sign that:

a>b)

includes a statement prohibiting un-authorized use, andindicates that hazardous radiationemission is produced when the equipmentis in operation.

3.2.1 The X-radiation warning sign is shown inFig. 1.

4 ACCOMPANYING DOCUMENTSRelevant requirements of*Part 1 of this standardshall apply.

5 RADIATION SAFETY5.1 All components except those specified in thisstandard shall meet the relevant and available

3

IS 7620(Part 3_):1991

CAUTION X-RAY

F I G. 1 X-RADIATION W ARNING S I G N

Indian Standard specifications on the design,construction and performance and be certified tothat effect. Such certified components onlyshall be used in the manufacture/assembly ofX-ray equipment/accessories.

5.2 The X-ray tube shall be securely fixed andcorrectly aligned within the tube housing.

The manufacturer of X-ray tube housingassembly shall specify the source to collimatorilange distance and maintain this for tube-housing assemblies within a tolerance of f3mm.

5.3 The X-ray tube housing shall maintain itsrequired exposure position or movement withoutexcessive drift or vibration during operation.5.4 Where more than one X-ray tube iscontrolled by one control panel except in thecase of a diagnostic X-ray machine specificallydesigned for simultaneous two-tube operation,it shall not be possible to energize more than oneX-ray tube at the same time and there shallbe at the control panel, a clearly visible indica-tion as to which X-ray tube is connected and isready to be energized.5.5 The diagnostic X-ray machine shall be.equipped with the following:

a>

,b)

Means to compensate for variation’ inX-ray tube potential caused by line voltagefluctuations to within f10 p:rcent of thesnlected value.A visible indication that warns theoperator or alternative!y, a device thatprevents X-rays from belrg produced whenthe variation in line voltage causesvariation in tube potent ia l in Excessof fl0 percent of tb selected value.

3

cl

1)

2)

3)

A control panel having the followingfeatures:Separate warning lights in clear view ofthe operator that respectively indicate:i) When the control panel is energized

and the device is ready to produce X-rays, and

ii) When X-ray are produced.Where the device has adjustable techniquefactors, electrical meters or otherindicators that enable the followingfactors or any combination thereof to bedetermined before the irradiation isinitiated:i) Operating tube potential in kV,

ii) Tube current in mA, andiii) The exposure time in s.Where the device has non-adjustabletechnique factors, permanently affixedmarks or labels or electrical meters orother indicators that enable,~at specifiedsource to image receptor distances, thefolkwing factors or any combinationthereof to be. determined before theexposure, is initiated:

i>

ii)iii)iv)

Operating tube potential in kV,Tube current in mA,The exposure time in s, and

Keyed filter interlock switches or otherpositive means to ensure that necessaryadded filtration is in place in any tubehousing assembly that;- has permanent inherent filtration

of 0’5 mm or less aluminiumequivalence, and

IS 7620( Part 3):1991

-- is designed to be operated withadded filtration.

v) Where the device is designed to moveunder remote control around or acrossa patient, provision for an emergeccystop switch, the activation of whichimmediately terminates both themotion of the device and theproduction of X-rays.

6 BEAM LIMITATION AND PROTECTIONAGAINST PRIMARY AND STRAY RADIA-TION

6.1 Tube Housing Leakage

Every tube housing for medical diagnostic X-rayequipment shall be so constructed that theleakage radiation through the protective housingin any direction. averaged over an area notlarger than 1 m’J shall not exceed an air kermaof pGy, in one hour ( approximately 115 mRin one hour ) at a distance of 1’0 m from theX-ray source when the tube is operating at eachof the ratings specified by the manufacturer.

6.2 Radiation Leakage from Transformers

The radiation level at 50 mm from the trans-former surface of the X-ray unit shall notexceed pGy, in one hour ( approximately 0.6 mRin one hour ).

6.2.1 Compliance shall be determined bymeasurements averaged over an area of 10 cm2.

6.3 Beam Limiting Devices

Beam limiting devices, such as light beamdiaphragms, cones or collimators shall beprovided to limit the useful beam to the area ofclinical interest. Wherever practicable, pre-ference should be given to the use of light beamdiaphragms. The beam limiting devices incombination with the tube housing shall complywith the requirements for leakage radiationspecified under 6.1.

6.4 Filtration

In such cases, the presence of t’ne lowerfilteration shall be indicated at the tubeassembly.

Additional filters should be provided for theuse of these tubes for normal techniques. Inthis case, -the appropriate filtration for thevarious ranges of potential differenceshall bemarked on the control panel and should beelectrically interlocked.

6.5 The Half Value Layer ( HVL )

6.5.1 HVL of the use!ul beam for a given X-raytube potential shall be not less than the valuesshown in Table 1.

6.5.2 If it is necessary to determine such half-value layer at an X-ray tube potential which isnot listed in Table 1, linear interpolation orextrapolation may be made. Positive meansshall be provided to ensure that at least theminimum filtration needed to achieve the abovebeam quality requirement is in the useful beamduring each exposure.

Table 1 Half-Value Layer(Clauses 6.5.1 and 6.5.2 )

Design Operating Measured PotentialRange Range

(kV penk ) ( kV peak J( 1 ) ( 2 )

Below 50ETotal filtration 0.5 mm Al49

HVL

(mm)( 3 )0.30.40.5

50 to 70Total filtration 1.5 mm Al I 70

;:;1’5

2-l2.32.52.7

120 3.2130 3.5140 3.8150 4.1

7 PARTICULAR REQUIREMENTS FORRADIOGRAPHIC EQUIPMENT

The total filtration in the useful beam fornormal diagnostic work shall be equivalent to

7-O The provisions of this clause apply to

not less than 2’5 mm Al of which 1’5 mm shallequipment used for radiography.

be permanent. 7.1 Every radiographic X-ray machine shall bedesigned and constructed to include:

6.4.1 Special Application ( Mammograplly )

For certain applications, it may be desirable towork with a total filtration less than that givenabove ( for example, for mammography ) betin no case shall the total filtration be less than0’5 mm Al equivalent.

a) field limitation,

b) exposure control system,c>l icdication of technique factors, andd) radiographic timing device.

7.1.1 When a light localizer is used to define thefn the case of use of an edge filter, for X-ray field, it shall provide an averageexample, molybdenum in mammography, theattenuation equivalent shall be given for the

illumination of not less than 50 lux (4’693 footcandles) at 1 m or at the mamximum SID,

low energy side of the absorption edge. whichever is less. The average illumination

4

shall be based upon measurements made in theappropriate centre of each quadrant of the lightfield in perfect darkroom.7.2 Except when spot-film devices are provided,every mobile and stationary general purposeradiographic X-ray system shall meet the follow-ing requirements.

a) There shall be a means provided forstepless adjustment of the size of theX-ray field with collimator completelyclosed. The field size at an SID of 1 m

b)

c>

shall not exceed 50 mm x 50 mm.Means shall be provided for visually de-fining the perimeter of the X-ray field.The total misalignment of the edges ofthe visually defir,ed field with the respec-tive edges of the X-ray field along eitherthe length or width of the visually definedfield shall not exceed 2 percent of thedistance from the source to the centre ofthe visually defined field when the surfaceupon which it appears is perpendicularto the axis of the X-ray beam.When a light localizer is used to definethe X-ray field, it shall provide an averageillumination of not less than 100 lux( 9’385 foot candles ) at 1 m or the maxi-mum SlD, whichever is less. Theaverage illumination shall be based uponmeasurements made in the appropriatecentres of each quadrant of the lightfield in perfect darkroom.

7.3 Except when spot film devices are provided,every statiouary general purpose X-ray systemshall meet the following requirements in additionto those prescribed in 7.2.

a) Means shall be provided to indicate whenthe axis of the X-ray beam is perpendi-cular<to the plane of the image receptor,to align the centre of the X-ray field withrespect to the centre of the image receptorto within 2 percent of the SID, and toindicate the SID to within 2 percent.

b) The beam-limiting device shall numeri-cally indicate theafield size in the planeof the image-receptor to which it isadjusted.

c) Indication of the field size dimensions andSID’s shall be specified in millimetres andshall be such that aperture adjustmentsresult in X-ray field dimensions in theplane of the image receptor which ‘corres-pond to those of the image receptor towithin 2 percent of the SID when thebeam axis is perpendicular to the plane ofthe image receptor.

d) Compliance measurements shall be madeat discrete SID’s image receptor dimen-sions in common clinical use and nominalimage receptor dimensions at which thebeam-limiting device or its associateddiagnostic X-ray system is uniquelydesigned and operated.

e) The radiographic system shall be capableof operation at the discretion of the

IS 7620 ( Part 3 ) : 1991

operator such that the field size at theimage receptor can be adjusted to a sizesmaller than the image receptor.

7.4 A radiographic timing device provided witha diagnostic X-ray machine shallbe designedso that:

a) it terminates an exposure onof any one of the following:

I ) A preset time interval,

completion

2) A preset produgt of current and time( mAs ), or

3) A preset number of pulses.

b) it permits the operator to terminate theexposure at any time; and

c) it automatically resets to its originalposition or zero at the termination of theexposure.

7.5 Permanent diaphragms, cones or otherbeam limiting devices shall be provided with adiagnostic X-ray equipment to collimate theuseful beam and these shall afford the samedegree of shielding as that required of the sourcehousing assembly.

7.6 Every radiographic equipment equipped withan automatic exposure control shall:

4

b)

be designed to include on the controlpanel, a clear indication as to when theautomatic exposure control mode ofoperation has been selected;where the X-ray tube operating potentialis 50 kV peak or greater, be designed andconstructed to have minimum exposuretime capability as under:

1) in the case of a field emission machinerated for pulsed operation equal to orless than the time interval equivalentof two pulses, or

2) in the case of all other machines equalto or less than l/60 second or the timeinterval required to deliver 5 mAs,whichever.is the greater.

c) be equipped with a means for ensuringthat:

1) where the X-ray tube potential is lessthan 50 kV peak, the product of theX-ray tube current and the exposuretime does not exceed 2 000 mAs perexposure, or

2) where the X-ray tube potential is 50kV peak or more:i) the product of, the X-ray tube

current and the exposure time doesnot exceed 600 mAs; however, forspecial radiography equipment, suchas, neuro radiography, the value isup to 800 mAs.

IS 7620 ( Part 3 ) : 1991

ii) the product of the peak X-ray tubepotential, current and exposure timedoes not exceed 60 kWs per ex-posure.

d) be equipped with a back-up timer havinga maximum setting:

1) in the case of a tomographic machine,of 10’0 s, and

2) in the case of any other machine, of3’0 s.

e) be designed :

1)

2)

to include, on the control panel, avisible light indicator that will warn theoperator, and

to require manual resetting of themachine before another automaticallytimed exposure can be made whentermination of an automatically timedexposure occurs because the limitsspecified in 7.6( c ) or ( d ) abovehave been reached.

8 PARTICULAR REQUIREMENTS FORFLUOROSCOPY EQUIPMENT

8.0 The provisions of this clause apply toequipment for fluoroscopy with or without animage intensifier.

8.1 Every fluoroscope X-ray machine shall bedesigned arid constructed to include:

a) beam limitation device,b) primary productive barrier,

c) exposure control system,

d) indication of X-ray and exposure para-meters, and

e) fluoroscopic timer.

8.2 Fluoroscopy X-ray equipment may bedesigned and constructed as combined radio-graphy and fluoroscopy equipment or exclusivefluoroscopy equipment and may have facilitiesor attachments for tine fluorography.

8.3 Mobile X-ray equipment shall not be usedfor fiuroscopy unless an image intensifier isemployed. The equipment shall be so construc-ted that the radiation beam is fully interceptedby the image receptor area of the image intensi-fier. It is preferable to use image storagedevices.

8.4 An adjustable collimator or diaphragmshould be provided to define the useful beam.

8.5 The X-ray tube, adjustable beam liyitingdevice and image receptor shall be linkedtogether~so that the beam will not fall outsidethe image receptor at any source-image receptordistance. In case of failure, an indication shallwarn the operator.

8.6 When the adjustable diaphragms are fullyopen, the X-ray field produced by non-imageintensifier fluoroscopic -equipment shall notextend beyond the entire visible area of theimage receptor.

8.6.3 The focus to table top distance must beso adjusted mechanically that it shall not inany case be less thin 300 mm for fluoroscopyunits and should preferably be ( a ) 450 mm forgeneral fluoroscopy units and ( b ) 600 mm forunits used exclusively for chest screening.8.7 For image intensiped fiuoroscopy equipmentother than treatment simulators, the useful beamshould be centred on the input phosphor andduring fluoroscopy or tine recording, it shouldnot significantly exceed the diameter of inputof phosphor. The primary protective barrieraround input phosphor shall extend at least25 mm each side beyond the edges of the usefulbeam.8.8 The image intensifiers and adjacent fittingswhich may be exposed to the useful beam shallprovide the same protection as that required forfluoroscopic screen assembly.

8.9 The fluoroscopic screen shal! be coveredwith a protective glass sheet having a leadequivalence of not less than the following:

kV Lead Equivalent ofProtective Glass

-Co; eringI

S O 1’570 1’5

10’;2’02.0

110120 ;:;

150 2’5200 3’0

8.10 The Auoroscopy tube shall not produceX-rays unless the primary protective barrier ofthe fluoroscopic image assembly is in positionto intercept the entire useful beam. In casewhere a separate X-ray tube is provided forfluoroscopy, the equipment shall provide pro-tection against inadvertent operation of theflcoroscopy tube when the image assembly isnot intercepting the useful beam. The focusto the table top distance must be so adjustedmechanic:llly that it shall not in any case beless than 300 mm for fluoroscopy units andpreferably 450 mm for gene:-al fluoroscopy unitsand 6CO mm for units used exclusively for chestscreening. The exposure rate due to trans-mission through the barrier, shall not exceed2 mR/h at 100 mm from any accessible surfaceof the fluoroscopic imaging assembly beyondthe plane of the image receptor for each 5 R/minof entrance exposure rate. This requirement isnot applicable for treatment simul:itors providedthe systems are intended only for remote control

6

operation. The manufacturer shallinstructions to the user concerningportance of remote control operation.

8.11 Table Top Dose

providethe im-

The air kerma rate measured at the table topfor the minimum focus to table to distanceshould be as low as possible and in any caseshall not exceed 5 cGy per minute ( approxi-mately 5’75 R per minute ).

8.12 Compliance with 8.11 shall be determinedas follows:

a) If the source is below the table, exposurerate shall be measured IO mm above thetable top; and

b) Jn the C arm type of fluoroscope, theexposure rate shall be measured 300 mmfrom the input surface of the fluoroscopicimaging assembly.

NOTE -The exposure switch for Ruoroscopyshall be of the ‘deadman’ type. that is, a switchso constructed that a circuit closing contact canbe maintained only by continuous pressure on theswitch.

In equipment for those applications where a‘deadman’ type exposure switch for fluoroscopywould prejudice the radiologist’s conduct of theexamiration, a permanent contact switch in-stead of a ‘deadman’ typz switch can bzaccepted provided the cumulative timing devicementioned below is constructed and connectedto terminate the fluoroscopic exposure at theend of a predetermined time not more thanIO minutes.

In all cases, a cumulative timing device activatedby the exposure-circuit for fluoroscopy shallbe provided which shall ~give a characteristicsignal at the end df a predetermined time notmore than IO minutes.The cumulative timirg device activated by theexposure-circuits should terminate the irradia-tion when the total exposure time of fluoros-copy exceeds a predetermined limit not exceed-ing IO minutes. In that case, instead of thecharacteristic signal at the end of the predeter-mined limit, a characteristic signal shall indicatejust prioi to the end of~the predetermined timein order to permit the device to be reset, ifnecessary.

The use of a patient area exposure meter orother type of measuring instrument indicatingpatient exposure is recommended.

8.13 The exposure rate due to transmissionthrough the primary barrier combined withradiation from image intensifier shall be deter-mined by measurements arranged over an areaof 1 ma with no linear dimension greater than200 mm. If the source is below the table top,the measurement should be made with the input

IS 7620 ( Part 3 ) : 1991

surface of the fluoroscopic imaging assemblypositioned 300 mm above the table top.Movable grids and compression devices shall beremoved from the useful beam during themeasuremer t.

8.14 If a provision for taking spot films duringfluoroscopic examination is made, the beamshall be intercepted by a barrier having a leadequivalent specified in 8.9 and shall be designedfor the highest X-ray tube voltage at whichradiographic exposure can be made.

8.15 All tables and stand: for fluoroscopy shallbe provided with barriers for protecting thefluoroscopist against scattered radiation fromthe patient and from materials between thesource and the patient. Openings such as buckyslots should be covered with barrier having alead equivalence of not less than 0’5 mm.Protective flaps or drapes which may consist ofoverlapping parts shall be attached to the loweredge of the screen holder when the screen isvertical or to the nearest edge to the operatorwhen the screen is horizontal. The lead equi-valence of the flaps or drapes shall be not lessthan 0’5 mm.

8.16 Electrical meters or other visual indicatorson the control panel shall provide continuousindication of X-ray tube potential ( in kV ) andcurrent (in mA ).

8.17 The total aluminium equivalent of all thematerials other than the screen, its associatedmechanical support panel or grids that arkpresent ~between the patient and the imagereceptor shall not exceed 3’5 mm.

8.18 X-ray production in the fluoroscopic modeshall be controlled by a switch or a device whichrequires continuous pressure by the operatorfor the entire time of any exposure. Whenrecording serial fluoroscopic images, the ope-rator shall be able to terminate the X-rayexposure( s ) at any. time but means mny beprovided to permit completion of any singleexposure of the series in process.

8.19 Means shall be provided to represent thecumulative on-time of the fluoroscopic tube.The maximum cumulative time of the timingdevice shall r.ot exceed IO minutes withoutrzsetting. To allow resetting if clinicallyessential, it shall be supplemented by an audiblesignal giving warning of the impending cessationof fluoroscopy. TLe elapsed fluoroscopy timeshould be visible to the fluoroscopist. 117 caseof treatment simulators, means to indicate thetotal cumulative exposure and provision of itsresetting between X-ray examination shall beprovided.

8.20 The fluoroscopic table top and the radiationcassette faces and non-opaque parts of gridshould preferably be made of materials of lowX-ray attenuation, such as, carbon fibre.

7

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goods andattending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publication), BIS.

Review of Indian Standards8

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issueof ‘BIS Handbook and ‘Standards Monthly Additions’.

This Indian Standard has been developed from Dot: No. MHD I9 ( 2223 )

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002Telephones: 323 01 31,323 33 75,323 94 02

Regional Offices:

Telegrams: Manaksanstha(Common to all offices)

Telephone

C e n t r a l : Manak Bhavan, 9 Bahadur Shah Zafar MargNEW DELHI 110002

E a s t e r n : l/14 C.I.T. Scheme VII M, V.I.P. Road, ManiktolaCALCUTTA 700054

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3237617,3233841

337 84 99,337 85 61337 86 26,337 9120

{ 60 60 38 20 43 25

{ 235 235 02 15 16,23519,235 04 23 42 15

832 92 95,832 78 58832 78 91,832 78 92

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