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RADIATION SAFETY (GENERAL) REGULATIONS 1983 - SCHEDULE 9

RADIATION SAFETY (GENERAL) REGULATIONS 1983 - SCHEDULE 9

[Regulation 36]

Conditions imposable on registration of irradiating apparatus

1.                 In the case of irradiating apparatus which is operated or used for dental radiography, including panoramic (tomographic) and cephalometric radiography —

            (a)         the x‑ray tube shall be enclosed in a housing in such a manner that the absorbed dose rate in air from leakage radiation measured at a distance of 1 metre from the focus of that x‑ray tube does not exceed —

                  (i)         for apparatus used with intra‑oral x‑ray film, 0.25 milligray in 1 hour; and

                  (ii)         for other apparatus, 1 milligray in 1 hour,

                at every rating specified by the manufacturer for that tube in that housing and, to determine compliance with this condition, measurements may be averaged over an area not larger than 10 000 square mms at a distance of 1 metre from that tube; and

            (b)         cones, diaphragms or collimators which serve to limit the useful beam shall be so constructed that, in combination with the x‑ray tube housing, they comply with the leakage radiation limits set out in paragraph (a); and

            (c)         the minimum power capability of apparatus —

                  (i)         used for —

                        (A)         dental radiography with intra‑oral x‑ray film; or

                        (B)         lateral oblique radiography of the mandible with extra‑oral x‑ray film,

                or both, shall be 60 kV(peak) at 7 milliamps for 3 seconds;

                  (ii)         used for dental radiography with intra‑oral x‑ray film but also used for cephalometric or trans‑cranial tempero‑mandibular joint radiography, shall be 70 kV(peak) at 10 milliamps for 3 seconds;

                and

            (d)         the selected —

                  (i)         tube potential difference in kV(peak), the x‑ray tube current in milliamps (mA) and the exposure time in seconds or fractions of a second; or

                  (ii)         kV(peak) and the product of the tube current and exposure time (mAs),

                shall be indicated by analogue metres, digital displays or scales, or calibrated permanent markings, but apparatus which provides for object programmed control (exposure selection by diagrammatic representations of the part to be examined) shall indicate the exposure time in seconds on the control panel; and

            (e)         when object programmed control exposure times can be modified by a further control which can be adjusted to account for variations in the speed of the film used —

                  (i)         that control shall be provided with a tool for its adjustment; and

                  (ii)         that control shall be clearly labelled to indicate its purpose; and

                  (iii)         there shall be clearly indicated on or adjacent to that control the setting to be used with “D” speed intra‑oral x‑ray film;

                and

            (f)         all conductors to the primary winding of the high voltage transformer shall be effectively inoperable when the exposure switch is in the OFF position and the failure of any component of the timing circuit or an earth fault shall not lead to the production of x‑rays; and

            (g)         the useful x‑ray beam shall incorporate filtration so that the half value layer of the useful x‑ray beam for a given x‑ray tube potential in kV(peak) is not less than the values given in the following table — 



Table



Design Operating Range

(kV(peak))

Measured Potential

(kV(peak))

Half Value Layer

(millimetres of aluminium)

60 to 70

60

1.5



70

1.5

Above 70

71

2.1



80

2.3



90

2.5



100

2.7



110

3.0



120

3.2



130

3.5



140

3.8



150

4.1

                and

            (h)         the exposure timer shall be electronic and the circuit of the apparatus shall be so designed that in the event of any component failure such failure is to a safe condition and does not lead to the x‑ray tube becoming energized or continuing to be energized; and

                  (i)         it shall not be possible to initiate an exposure without the exposure timer set to a nominated exposure time greater than zero (or to a projection in the case of an object programmed control) and the exposure control switch shall be protected against accidental operation; and

            (j)         the apparatus shall incorporate —

                  (i)         a visual signal in the form of a yellow light which —

                        (A)         is clearly visible; and

                        (B)         is marked as to its function; and

                        (C)         illuminates when the x‑ray tube is energized;

                and

                  (ii)         an audible signal (discernible from sounds produced by switching devices or contactors during the exposure) which sounds for the duration of the exposure or at its termination,

                and both the visual and audible signals shall be —

                  (iii)         located at the control panel; or

                  (iv)         in the case of remotely controlled equipment, where those signals could not otherwise be seen or heard, at the position of the operator;

                and

            (k)         the exposure control switch shall be so arranged that the operator can remain well outside the useful x‑ray beam and at least 2 metres from the x‑ray tube and the patient during the exposure, but if this distance cannot be achieved and if the Council so requires, a protective barrier shall be provided; and

            (l)         where the exposure is initiated by an infra‑red or wireless remote control handpiece, that handpiece shall —

                  (i)         be encoded so that no other remote control handpiece can initiate exposures; and

                  (ii)         be permanently labelled with a warning identifying the purpose of the handpiece; and

                  (iii)         have provision at the control panel for its storage;

                and

            (m)         the exposure control switch, including that for infra‑red or wireless remote control handpieces, shall be “dead man” so that continuous pressure is necessary to maintain the x‑ray exposure and it shall not be possible to make repeat exposures without releasing that switch; and

            (n)         it shall not be possible to initiate an exposure other than for a preset time interval, except in the case of apparatus equipped with an automatic exposure control device, in which case an overriding timer shall be provided to limit the total exposure time —

                  (i)         in the case of apparatus used with intra‑oral x‑ray film for —

                        (A)         lateral oblique examinations of the mandible; or

                        (B)         cephalometric examinations,

                to not more than 3 seconds; and

                  (ii)         in the case of panoramic (tomographic) apparatus, to not more than 20 seconds;

                and

            (o)         the accuracy of the timer shall ensure that —

                  (i)         the measured exposure time is within plus or minus 10% for exposure times greater than or equal to 0.1 second and within plus or minus 20% for exposure times less than 0.1 second, with the exposure time in seconds determined —

                        (A)         for single phase generators, by counting the total number of pulses in the radiation waveform and multiplying by a factor of 0.02 if half wave rectified or a factor of 0.01 if full wave rectified; and

                        (B)         for other generators, from the time the radiation waveform first rises to 65‑85% of the kV(peak) until the time at which it finally drops below this value of the final peak;

                  (ii)         for any specified combination of selected exposure factors the coefficient of variation (as defined below) of radiation exposure does not exceed 0.05 and compliance with this requirement shall be based on 10 consecutive measurements taken within 60 minutes each with an exposure time of not less than 0.1 seconds.

Coefficient of variation (C) means the ratio of the standard deviation to the mean value of a series of measurements calculated as follows —



                Where —

        X i =         ith measurement

        =         mean value of measurements

        S =         estimated standard deviation

        n =         number of measurements;

                and

            (p)         the current delivered to the x‑ray tube shall be within plus or minus 15% of the indicated value; and

            (q)         where the tube current can be varied, then for any single value of the x‑ray tube voltage in kV(peak) within the range specified for the apparatus, the average ratios of the dose in air (in milligray) to the product of the tube current and exposure time (as mAs) obtained at any 2 tube current settings at the same focal spot size, shall not differ by more than 0.2 times their mean calculated as follows —



                Where —

        =         the average of 10 consecutive measurements of the ratios of the measured values of the dose in air to the mAs;

                and

            (r)         the kilovoltage applied to the x‑ray tube shall be within plus or minus 5% or plus or minus 5 kV(peak), whichever is the lesser, of the nominal or pre‑set value averaged over the first 100 milliseconds of the exposure; and

            (s)         except for equipment used for panoramic (tomographic) radiography, the x‑ray tube head shall remain stationary when placed in position for radiography; and

            (t)         where a light beam collimator is provided to define the shape and size of the useful x‑ray beam —

                  (i)         the illuminance of the light beam shall not be less than 100 lux at a distance of 1 metre from the focal spot of the x‑ray tube or at the plane of the x‑ray film, whichever is the lesser;

                  (ii)         the contrast (as defined below) at the edge of the illuminated field at the distance referred to in subparagraph (i) shall not be less than 3;

                contrast means the ratio of the illumination measured 3 mms from the edge of the field towards the centre of the field to the illumination measured 3 mms from the edge of the field away from the centre of the field, using a measuring aperture not greater than 1 mm;

                  (iii)         the collimator shall be designed so that the irradiated area does not exceed the illuminated area under any conditions and the edges of the irradiated and illuminated areas are coincident to within 10 mm at 100 cms;

                  (iv)         the collimator shall be attached to the x‑ray tube housing so that it cannot be detached without the use of tools;

                and

            (u)         for apparatus intended for use with intra‑oral x‑ray film and which may also be used for lateral oblique examinations of the mandible, the cone, diaphragm or collimator referred to in paragraph (b) —

                  (i)         shall limit the diameter of the useful beam at the end of that cone, diaphragm or collimator to a diameter not exceeding 60 mm or, if the x‑ray beam is not circular, to a maximum diagonal dimension of 60 mm; and

                  (ii)         shall be open ended and shall be so constructed that the minimum distance from the outer end to the x‑ray tube focus is not less than 200 mm and the internal diameter is greater than the diameter of the useful beam at the outer end;

                and

                  (v)         for apparatus used for panoramic (tomographic) radiography, the cone, diaphragm or collimator referred to in paragraph (b) —

                  (i)         shall provide a useful x‑ray beam with dimensions not greater than the dimensions of the slot in the secondary collimator immediately adjacent to the x‑ray film and that cone or diaphragm shall also restrict the vertical dimension of the useful beam so that it cannot exceed the height of the x‑ray film (or its smallest dimension); and

                  (ii)         in conjunction with the x‑ray tube housing shall limit the distance between the x‑ray tube focus and the patient’s skin to not less than 150 mm;

                and

            (w)         for apparatus used for cephalometric radiography —

                  (i)         the cone, diaphragm or collimator referred to in paragraph (b) shall restrict the useful beam to the size of the x‑ray film and shall not exceed —

                        (A)         180 x 240 mm or 180 mm in diameter for an x‑ray film with dimensions of 180 mm x 240 mm; and

                        (B)         240 x 300 mm or 240 mm in diameter for an x‑ray film with dimensions of 240 x 300 mm;

                and

                  (ii)         the x‑ray tube and x‑ray film shall be so arranged that the x‑ray tube focus to film distance is not less than 1.5 metres and the minimum x‑ray tube focus to the patient entrance surface is not less than 300 mms;

                and

                  (x)         where the apparatus is designed —

                  (i)         exclusively for one of the purposes referred to in paragraph (u) or (v), the cone, diaphragm or collimator shall be attached to the x‑ray tube housing so that it cannot be detached without the use of tools;

                  (ii)         for more than one such purpose the cone, diaphragm, or collimator selected shall be interlocked so that the use of the apparatus is restricted only to the purpose appropriate to that cone, diaphragm or collimator;

                and

            (y)         the x‑ray tube assembly shall be marked with —

                  (i)         the name of the supplier or manufacturer;

                  (ii)         the type number of the x‑ray tube or the x‑ray tube assembly;

                  (iii)         the nominal value of the inherent filtration of the x‑ray tube assembly and, where appropriate, the value of any permanently added filtration including that provided by cones, diaphragms or collimators;

                  (iv)         the position and nominal size of the focal spot or spots;

                  (v)         the values of the x‑ray tube potential in kV(peak) and the tube current where those values are fixed;

                and

            (z)         intra‑oral x‑ray tubes shall not be used; and

            (za)         fluoroscopy shall not be used.

2.                 In the case of irradiating apparatus which is operated or used for diagnostic medical radiography —

            (a)         the x‑ray tube shall be enclosed in a housing in such a manner that the absorbed dose rate measured in air from leakage radiation measured at a distance of 1 metre from the focus of that tube does not exceed 1 milligray in 1 hour at each rating specified by the manufacturer for that tube in that housing and, to determine compliance with this requirement, measurements shall be averaged over an area not larger than 10 000 sq mm at a distance of 1 metre from that tube;

            (b)         diaphragms, cones or collimators used to limit the useful beam to the area of clinical interest shall be so constructed that, in combination with the tube housing, they comply with the leakage radiation limits set out in paragraph (a);

            (c)         except in relation to irradiating apparatus or procedures specified in writing by the Council —

                  (i)         a continuously adjustable multiplane rectangular collimator shall be fitted to the x‑ray tube and that collimator shall, except in the case of examinations utilizing a serial changer in association with a fluoroscopic apparatus, be a light beam unit; and

                  (ii)         the lack of alignment between any boundary of the light beam and the equivalent boundary of the x‑ray beam in the plane of the image receptor shall not exceed 1% of the distance between the target of the x‑ray tube and the plane of the image receptor; and

                  (iii)         the illuminance of the light beam shall be not less than 100 lux at a distance of 1 metre from the light source; and

                  (iv)         when provision is made for the automatic adjustment of the collimator referred to in subparagraph (i) to the size of the film in use, it shall be possible, at the discretion of the operator, to adjust that collimator to produce an x‑‑ray beam smaller than the size of the film in use;

            (d)         when more than one x‑ray tube can be operated from a single control panel, there shall, except in the case of the undertable and associated overtable x‑ray tubes on fluoroscopic equipment, be an indication at or near the tube housing and on the control panel showing which x‑ray tube is selected;

            (e)         when x‑ray tube potential and current —

                  (i)         are capable of being varied, control settings or meters shall be provided in the control panel referred to in paragraph (d) to indicate that potential and current; or

                  (ii)         are not capable of being varied, the values of that potential and current shall be indicated on the control panel referred to in paragraph (d);

            (f)         filtration shall be added, when necessary, to the useful x‑ray beam so that the half value layer of the beam for a given x‑ray tube and collimator shall not be less than the values shown in the following table —

Table

Design operating

range

(kilovolts peak)

Measured potential

(kilovolts peak)

Half value layer

(millimetres of

aluminium)

Below 50 .....................







50 to 70 .......................







Above 70 .....................

30

40

49



50

60

70



71

80

90

100

110

120

130

140

150

0.3

0.4

0.5



1.2

1.3

1.5



2.1

2.3

2.5

2.7

3.0

3.2

3.5

3.8

4.1

                and either positive means shall be provided to ensure that at least the minimum filtration needed to achieve the beam quality specified in the above table is in the useful beam during each exposure or, failing that provision, the filtration shall be not less than is required to achieve the beam quality specified in the above table for the maximum x‑ray tube potential at which the x‑ray tube can operate with its associated control, and the Council may require permanent filtration in addition to the minimum filtration given above;

            (g)         the total filtration permanently in the useful beam as specified in paragraph (f) shall be indicated on the tube housing, or the separate components of that filtration shall be indicated on the tube housing and diaphragm;

            (h)         a device shall be provided to terminate the exposure after a preset time interval or exposure and, when an automatic exposure control is provided, that control shall limit the exposure time in such a manner that the product of x‑ray tube current and exposure time per exposure does not exceed —

                  (i)         1 000 mAs; or

                  (ii)         if the x‑ray tube potential is less than 50 kVp, 2 000 mAs,

                and, when an exposure has been terminated at the limits described in this paragraph, a visible or audible signal shall indicate that termination has occurred and that manual resetting is required before further automatically timed exposures can be made;

                  (i)         when an automatic exposure control is used to terminate the exposure, the selection of that control shall, when it takes place, be visibly indicated on the control panel;

            (j)         the exposure switch shall —

                  (i)         be designed so that it is protected against accidental operation; and

                  (ii)         except in special circumstances specified by the Council, be so arranged that it cannot be operated outside a shielded area,

                but this requirement does not apply to exposure switches used in conjunction with fluoroscopic equipment or to portable or mobile x‑ray apparatus unless the Council otherwise directs in writing;

            (k)         the x‑ray tube head shall, except in tomography and other procedures in which it is a requirement that the x‑ray tube head move in a predetermined manner, be supported in such a way that it remains stationary when placed in position for radiography;

            (l)         “Inverted T” collimation shall be provided for full spine radiography to enable the x‑ray beam to be confined to the spinal column and the pelvic bones;

            (m)         the aluminium equivalent of each of the items listed in the following table which are used between the patient and image receptor shall not exceed the limits indicated in that table and compliance with this requirement shall be determined by x‑ray measurements made at a potential of 100 kilovolts peak and with an x‑ray beam which has a half‑value layer of 2.7 millimetres of aluminium, but this requirement does not apply to such items as a fluorescent screen and its associated mechanical support panel or grids —

Table

Item

Aluminium equivalent (millimetres)

Front panel(s) of cassette holder

(total of all)

Front panel(s) of film changer

(total of all)

Stationary tabletop

Movable tabletop

(including stationary subtop)

Cradle



1.0



1.0

1.0



1.5

2.0

            (n)         involving portable or mobile x‑ray apparatus —

                  (i)         paragraphs (a), (b), (c), (e), (f), (g), (h) and (k) apply to that apparatus, except that the continuously adjustable rectangular collimator referred to in paragraph (c) need not be multi‑plane; and

                  (ii)         a cable not less than 2 metres in length shall be provided for the exposure control switch of that apparatus so that the operator thereof can remain outside the x‑ray beam at least 2 metres from the x‑ray tube and from the patient; and

                  (iii)         the equipment shall be so arranged that an x‑ray tube focus to film distance of at least 750 mm may be utilized for medical radiography; and

                  (iv)         that apparatus shall have a minimum x‑ray exposure capability of 85 kVp at 20 milliamperes for 2 seconds;

            (o)         involving photo fluorography —

                  (i)         high efficiency optical systems shall be used; and

                  (ii)         when there is a fixed relationship between the x‑ray tube and the photo fluorographic camera, a fixed diaphragm is provided which limits the x‑ray beam to dimensions no larger than those of the fluorescent screen and the equipment is designed for one image size only, it shall not be necessary for a continuously adjustable rectangular light beam diaphragm to be provided; and

                  (iii)         when a light beam diaphragm is provided, it shall not be possible for the dimensions of the x‑ray beam to exceed those of the fluorescent screen;

            (p)         involving equipment in which the x‑ray tube is energised by a capacitor energy storage system (capacitor discharge x‑ray equipment), radiation emitted from the x‑ray tube when the exposure switch or timer is not activated shall not exceed 20 microsieverts per hour at 50 mm from any accessible surface of the x‑ray tube or associated diaphragm or collimator with the collimator fully open and, to determine compliance with this requirement, measurements shall be averaged over an area not exceeding 10 000 square mm with no linear dimension greater than 200 mm and the response time of the measuring instrument shall not be less than 3, nor greater than 20, seconds.

3.                 In addition to the requirements specified in item 2, in the case of irradiating apparatus that is operated or used for medical or veterinary fluoroscopy —

            (a)         the irradiating apparatus shall, for the purpose of viewing fluoroscopic images, always be used in conjunction with an electronic image intensifier;

            (b)         the irradiating apparatus shall be so constructed that the entire cross‑section of the useful x‑ray beam is always intercepted by a primary protective barrier irrespective of the source to image receptor distance;

            (c)         the useful x‑ray beam shall automatically terminate when that barrier is removed from the useful x‑ray beam;

            (d)         the primary protective barrier, which includes the electronic image intensifier and adjacent mounting components subject to exposure to the useful x‑ray beam, shall have a lead equivalence not less than —

                  (i)         1.5 mm for maximum operating potentials less than or equal to 70 kV(peak);

                  (ii)         2.0 mm for maximum operating potentials greater than 70 kV(peak) and less than or equal to 100 kV(peak);

                  (iii)         2.0 mm for maximum operating potentials greater than 100 kV(peak) plus 0.01 mm for each kV(peak) above 100 kV(peak),

                and this lead equivalence shall also apply to radiographic exposures made using the fluoroscopic tube and the associated serial spot film device;

            (e)         for mobile fluoroscopic apparatus —

                  (i)         the fluoroscopic x‑ray beam at the image intensifier input shall be limited by a collimator to a circle or square whose diameter or diagonal respectively is no greater than the diameter of the image intensifier input;

                  (ii)         if the user can select a different field size or x‑ray tube focus to image intensifier input distance, the collimator shall automatically adjust to comply with these limits;

                  (iii)         the size of the x‑ray beam at the image intensifier input shall in no case be greater than the area imaged on the television display;

                  (iv)         the radiographic x‑ray beam shall be limited by a collimator to a size no greater than the image receptor selected and, if the collimation is circular, to a circle whose diameter is no greater than the smallest linear dimension of the image receptor;

                  (v)         where a range of discrete radiographic beam sizes can be selected, indication shall be provided on the control panel of the irradiating apparatus to show which beam size has been selected;

                  (vi)         if the beam size can be varied continuously, the collimation shall automatically adjust so as not to be greater than the image receptor size selected;

            (f)         for other fluoroscopic apparatus —

                  (i)         the fluoroscopic x‑ray beam at the image intensifier input shall be limited automatically by a collimator to a circle or square whose diameter or diagonal respectively is no greater than the diameter of the image intensifier input regardless of the effective field size or tube focus to image intensifier input distance selected;

                  (ii)         the size of the x‑ray beam at the image intensifier input shall in no case be greater than the area imaged on the television display;

                  (iii)         the radiographic x‑ray beam shall be limited automatically by a collimator to a size no greater than the image receptor selected and if the collimation is circular, to a circle whose diameter is no greater than the smallest linear dimension of the image receptor;

                  (iv)         where the apparatus can be used without an intervening tabletop or where the image intensifier is fixed beneath the table (overtable tube fluoroscopy), the x‑ray beam shall be defined by a light beam collimator that complies with the requirements of item 2(c);

            (g)         for apparatus where the image intensifier is fixed beneath the tabletop (overtable tube fluoroscopy), control of the fluoroscopic procedure shall be made from a location remote from the table and this location shall be shielded as directed by the Council;

            (h)         the minimum distance between the x‑ray tube focal spot and the patient support or the patient’s skin, depending on the apparatus configuration, shall be as specified in the following Table —

Table

Apparatus Configuration

Patient Support

Minimum Distance

Undertable x‑ray tube

Permanently between the x‑ray tube and patient

400 mms between the x‑ray tube focal spot and the patient support

Overtable x‑ray tube

Permanently between the image intensifier and patient

700 mms between the x‑ray tube focal spot and the patient support

Mobile C‑arm apparatus

May or may not be permanently in the useful x‑ray beam

200 mms between the x‑ray tube focal spot and the patient’s skin

Other fluoroscopic apparatus

May or may not be permanently in the useful x‑ray beam

700 mms between the x‑ray tube focal spot and the input surface of the image intensifier

                  (i)         except where it cannot reasonably be avoided, no person shall operate mobile fluoroscopic apparatus in such a manner that the distance between the x‑ray tube focus and the patient entrance surface is less than 300 mms;

            (j)         a timing device shall be provided to indicate the elapsed fluoroscopic exposure time and an audible signal requiring manual resetting shall provide a warning to the fluoroscopist at intervals not exceeding 5 minutes and provision shall be made for the display to be set to zero for each patient but resetting of the alarm need not necessarily also reset the timer to zero;

            (k)         subject to paragraphs (l) and (m), the maximum absorbed dose rate in air for the apparatus configurations specified in the following Table at the measurement points and under the conditions specified in that Table shall not exceed 50 milligray per minute —

Table

Apparatus Configuration

Patient Support

Measurement Point

Other Conditions

Undertable x‑ray tube

Permanently between the x‑ray tube and patient

10 mms from the patient support on the patient side of the support

Shortest distance between the x‑ray tube focal spot and patient

Overtable x‑ray tube

Permanently between the image intensifier and patient

300 mms above the patient support on the x‑ray tube side of the support

Shortest distance between the x‑ray tube focal spot and patient

C‑arm or U‑arm apparatus where the x‑ray tube and image intensifier are mechanically linked

May or may not be permanently in the useful x‑ray beam

300 mms from the input surface of the image intensifier

Shortest distance between the x‑ray tube focal spot and the image intensifier but not less than 400 mms from the x‑ray tube focal spot

Other fluoroscopic apparatus

May or may not be permanently in the useful x‑ray beam

400 mms from the x‑ray tube focal spot or the minimum distance, whichever is greater



            (l)         notwithstanding paragraph (k), where the apparatus is fitted with automatic dose rate control and a higher dose rate is temporarily required, a maximum dose rate in air of 100 milligray per minute is permitted for the apparatus configurations specified in the Table to paragraph (k) at the measurement points and under the conditions specified in that Table, subject to the higher dose rate facility —

                  (i)         being activated by a clearly identified control requiring a deliberate action by the fluoroscopist; and

                  (ii)         being accompanied during activation by —

                        (A)         a continuous signal audible to the fluoroscopist and distinguishable from the signal required under paragraph (j); or

                        (B)         an identified and readily distinguishable visible signal at the image viewing position occupied by the fluoroscopist;

                and

                  (iii)         automatically returning to the lower dose rate setting if the higher dose rate facility is —

                        (A)         not activated by a “dead man” switch; and

                        (B)         unused for 5 minutes or more or otherwise disconnected from the power source;

            (m)         paragraph (k) does not apply during pulsed cinefluorography or electronic radiography;

            (n)         for apparatus with automatic dose rate control, or at 90 kV(peak) for apparatus with semi‑automatic dose rate control, the dose rate in air measured under the conditions specified in the Table to paragraph (k) with the x‑ray beam attenuated by a methyl methacrylate and aluminium abdominal phantom, as defined in American National Standards Institute publication ANSI PH2.43‑1982, item 3.1, shall not exceed 15 milligray per minute;

            (o)         the apparatus shall provide either an analogue or digital display to indicate both the fluoroscopic x‑ray tube voltage and the fluoroscopic current whenever the x‑ray tube is energized;

            (p)         the fluoroscopic exposure switch shall be “dead man” and foot switches shall be protected against accidental activation;

            (q)         for conventional undertable x‑ray tube fluoroscopic apparatus —

                  (i)         an apron or drape consisting of overlapping segments and providing shielding equivalent to not less than 0.5 mm of lead shall be attached to the edge of the serial changer in such a way that there is no gap between the drape and the serial changer or between the segments when the drape hangs vertically and unobstructed;

                  (ii)         the apron or drape shall not be smaller in width than the width of the serial changer measured parallel to the table length and shall be long enough to reach the tabletop with the table horizontal and the serial changer at its maximum height above the table;

                  (iii)         any bucky slot opening in the side of the table adjacent to the person performing fluoroscopy shall be covered during fluoroscopy with a barrier equivalent to not less than 0.5 mm lead.

4.                 In the case of x‑ray therapy apparatus which is operated or used for medical therapy and in which the x‑rays produced have a maximum energy not exceeding 500 000 electron volts —

            (a)         an x‑ray tube used for conventional x‑ray therapy shall be enclosed in such a housing that, at every specified rating of that tube in that housing, the absorbed dose rate in air from the leakage radiation measured —

                  (i)         at a distance of 1 metre from the focus does not exceed 10 milligrays per hour, or 300 milligrays per hour at any position accessible to the patient at a distance of 50 mm from the surface of that housing or its accessory equipment; or

                  (ii)         in the case of an x‑ray tube which is operated at a potential of 60 kilovolts peak or below, does not exceed 1 milligray per hour at any position 50 mm from the surface of that housing or its accessory equipment,

                and for the purpose of determining compliance with this requirement, measurements shall be averaged over an area not exceeding 10 000 square mm at a distance of 1 metre or 1 000 square mm at a distance of 50 mm, as the case requires, from the x‑ray tube or source housing;

            (b)         the high tension generator shall be —

                  (i)         so designed that it maintains the tube potential and current within plus or minus 2% of the preset values; and

                  (ii)         provided with —

                        (A)         a meter to indicate a deviation from the preset values of the tube potential or current; or

                        (B)         a visual or audible indicator to react if the tube potential or current transgresses the preset values;

            (ba)         electronic circuits shall be provided to identify the choice and location of interchangeable filters;

            (bc)         where a choice of interchangeable filters can be made by an operation within the treatment room —

                  (i)         exposure shall not be capable of being made until the choice has been verified by a confirming operation at the control panel; and

                  (ii)         when the confirming operation has been completed, the chosen filter combination shall be displayed at the control panel;

            (c)         permanent diaphragms or cones shall be so constructed that, in combination with the x‑ray tube housing, they comply with the exposure requirements for leakage radiation set out in paragraph (a);

            (d)         adjustable or removable beam limiting diaphragms or cones shall not transmit more than 5% of the useful beam at the maximum operating kilovoltage and with the maximum treatment filter in position;

            (e)         the x‑ray tube shall be so secured in its housing that it cannot move in relation to the useful beam aperture and there shall be a clear mark on the exterior of the x‑ray tube housing to indicate the position of the focal spot;

            (f)         the x‑ray tube housing shall remain stationary during stationary portal treatment;

            (g)         there shall be a clearly visible indicator on the control panel which indicates when x‑rays are being produced;

            (h)         equipment in which the useful beam is controlled by a shutter shall have clearly visible indicators on the control panel which indicate whether the shutter is open or closed;

                  (i)         an indicator light shall be provided near the entrance to the treatment room to indicate when the useful beam is being transmitted;

            (j)         the equipment shall be so designed that —

                  (i)         the full operating tube potential and current are attained within a period of time such that the skin dose to the patient does not exceed 50 milligrays during that time; or

                  (ii)         the tube assembly carries a remotely operated shutter to control the useful beam so that the skin dose to the patient does not exceed 50 milligrays during the period of time it takes for the shutter to open;

            (k)         subject to paragraph (q), the equipment shall be provided with 2 automatic timers, comprising a primary timer and a back‑up timer;

            (l)         the timers referred to in paragraph (k) shall be so designed and arranged that —

                  (i)         the failure of one timer does not affect the operation of the other timer; and

                  (ii)         the possibility of accidental communication between the timers is minimised; and

                  (iii)         the failure of the main power supply to either timer will terminate the exposure; and

                  (iv)         each timer is capable of terminating the exposure independently of the other timer; and

                  (v)         the 2 terminating circuits are kept physically separated; and

                  (vi)         each timer counts upwards from zero so that an over exposure will give a reading; and

                  (vii)         the primary timer terminates the exposure when the preset time for termination of the exposure is reached; and

                  (viii)         the back‑up timer terminates the exposure after, but not more than 0.1 minutes after, the preset time for termination of exposure on the primary timer; and

                  (ix)         each timer continues to record and display until the exposure is terminated by whatever means and retains the display of its readings on and after termination; and

                  (x)         in the event of a power failure, readings displayed at the time of that failure are stored in a retrievable form; and

                  (xi)         a single preselection of the exposure time presets both timers; and

                  (xii)         the displays of the timers are positioned closely together on the control panel, identical in form and easy to read; and

                  (xiii)         the timers are single scaled in minutes and decimals of minutes or in seconds only and are capable of being read without further calculation;

            (m)         there shall be a clearly visible or audible indicator on the control panel which is activated when the exposure is terminated otherwise than by the primary timer referred to in paragraph (k);

            (n)         subject to paragraph (o), the electronic circuits of the equipment shall be so designed that after each exposure —

                  (i)         the tripping mechanism of the back‑up timer is checked; and

                  (ii)         the setting of each timer is returned to zero,

                by the operator of the equipment before a new exposure can be made;

            (o)         the procedures referred to in paragraph (n) may be carried out automatically if the equipment is provided with timers that produce a permanent printout or chart record;

            (p)         equipment which can operate at tube potentials exceeding 150 kilovolts peak shall be provided with a transmission monitoring ionisation chamber or equivalent device positioned in the useful beam to provide a continuous check on the constancy of the radiation output;

            (q)         the chamber referred to in paragraph (p) may be used as an integrating dose meter to control treatment dose in the place of the primary timer referred to in paragraph (k) and where that chamber is so used —

                  (i)         the integrating dose meter shall terminate the exposure by switching off the high tension or closing the shutter when the preset dose for the treatment is reached; and

                  (ii)         the equipment shall be provided with a back‑up timer so designed and arranged that it —

                        (A)         is capable of terminating the exposure independently of the integrating dose meter; and

                        (B)         terminates the exposure after the expiry of a period of time that exceeds the period of time estimated for the treatment by not more than 10% of that estimated period of time;

                and

                  (iii)         the integrating dose meter and the back‑up timer shall count upwards from zero so that an over exposure will give a reading; and

                  (iv)         the integrating dose meter and the back‑up timer shall continue to record and display until the exposure is terminated by whatever means and shall retain the display of their readings on and after termination.

5.                 In the case of irradiating apparatus which is operated or used for veterinary radiography —

            (a)         the requirements specified in item 2 in relation to the use in diagnostic medical radiography of fixed and mobile equipment, other than the requirements set out in paragraphs (c) and (n)(iv) of that item, shall apply to that irradiating apparatus;

            (b)         sheet lead at least 1 mm thick shall, when an x‑ray table is used for radiography, be provided in the top of that table or, if a bucky is fitted, below the bucky tray, so as to intercept the x‑ray beam fully, but this requirement may be waived by the Council in writing in respect of approved special procedures;

            (c)         the film or cassette shall, whenever radiography with an angulated or horizontal beam is necessary, be supported by mechanical means;

            (d)         such devices for restraining and immobilising animals for radiography as the Council directs in writing shall be provided.

6.                 In the case of x‑ray equipment which is used for industrial radiography and in which x‑rays are produced by the direct application of a high voltage to the x‑ray tube, that tube shall be enclosed in a housing in such a manner that the exposure from leakage radiation measured at a distance of 1 metre from that tube does not exceed 10 milligrays per hour at every specified rating of that tube in the housing.

7.                 Cabinet x‑ray apparatus shall comply with the specifications relating to cabinet x‑ray equipment set out in the publication entitled “Revised statement on cabinet x‑ray equipment for the examination of letters, packages, baggage, freight and other articles for security and related purposes” approved by the NHMRC at its 85th session in June 1978.

8.                 X‑ray analysis equipment shall comply with —

            (a)         the requirements for equipment used for x‑ray analysis set out in the NHMRC publication entitled “Code of Practice for Protection against Ionizing Radiation emitted from X‑ray Analysis Equipment 1984”; or

            (b)         if that equipment is of such a kind that the requirements of the publication referred to in paragraph (a) cannot readily be complied with, such requirements as the Council specifies in writing in relation to that equipment for the purpose of achieving a level of safety equivalent to that attained by compliance with the requirements of that publication.

9.                 In the case of x‑ray equipment used by chiropractors for radiography of human beings the requirements specified in this Schedule for fixed medical diagnostic x‑ray apparatus must be met.

        [Schedule IX amended: Gazette 15 Mar 1991 p. 1127‑9; 28 May 1993 p. 2588‑94; 11 Jun 1993 p. 2873‑7; 4 Feb 1994 p. 341; 22 Jul 1997 p. 3824.]