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 |
Measured Potential |
Half Value Layer |
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 |
Measured potential |
Half value layer |
---|---|---|
Below 50 ..................... |
30 |
0.3 |
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 Front panel(s) of film changer Stationary tabletop Movable tabletop Cradle |
1.0
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.]