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L-0.2, r. 1 - Regulation respecting the application of the Act respecting medical laboratories and organ and tissue conservation
Schedule
Disposition versions
SCHEDULE 9
(ss. 195 and 198)
To determine the shielding of a general medical imaging or specific diagnostic radiology installation, it is imperative to know:
(a) The permissible exposure rate at the considered point (P/T)
P: being the maximum permissible weekly exposure under section 195 of the Regulation, that is:
100 m Rem/week for controlled zone
10 m Rem/week for uncontrolled zones.
T: being the occupancy factor, that is, the fraction of the working week during which a sector is usually occupied.
N.B. When T is unknown, use the values represented in Table II.
(b) Weekly exposure at the point of interest (E m R/week)
For practical computation purposes, 3 distinct radiation sources are distinguished for each operating tube:
(1) the primary beam;
(2) the radiation scattered by the patient:
(3) the radiation leakage.
The corresponding values of E are computed by using the following formulas:
(1)Epri= fn W.U./(dprim.)2 (1)
(2)Esca=fna W F/400 (dsca)2 (dsec) 2(2)
(3)Ef=fi W/d2sec(3)
(2)Esca=fna W F/400 (dsca)2 (dsec) 2(2)
(3)Ef=fi W/d2sec(3)
where W: is the weekly workload expressed as mA-min/week.
U: the use factor: that is, the fraction of time during which the useful beam is directed towards the barrier or the target sector.
N.B. When unknown, the values represented in Table 1 of this Schedule are used.
dpri: the distance in metres between the point nearest the surface to be shielded and the position of mean use of the tube-head.
dsca: the distance in metres between the focus of the tube and the surface closest to the patient (focus-skin distance generally used and compatible with sections 153 and 154 of this Regulation).
dsec: the distance in metres between the scattering focus and the point of interest.
fn :the exposure rate per current unit of the contemplated device expressed in milliroentgen/milliampere/minute (mR/mA-min.). This value must be known or measured at a distance of one metre from the focus, within the primary beam filtered according to section 156 of this Regulation under normal operating conditions. Such measure of f must necessarily be made by a physicist using the appropriate instruments and depends on the voltage and the method of rectification. Table III indicates the values recently measured by Kelley and Trout for pulsating potential devices (Ref.: J.P. Kelley and E. Dale Trout, Radiology 104: 171-172 July 1972).
fi:the unit exposure rate expressed in (mR/mA-min.) due to the maximum permissible radioation leakage.
fi = fn/1000 is written(4)
fi:the unit exposure rate expressed in (mR/mA-min.) due to the maximum permissible radioation leakage.
fi = fn/1000 is written(4)
F: the size of the field used expressed in cm2.
a: the mean ratio of the quantity of radiation emitted to the primary radiation for a field of 400 cm2. Such ratio depends on the angle of scattering and on the tube potential. Values are given in Table IV of this Schedule.
Knowing the permissible exposure rate (P/T) and the radiation intensity (E) at the point of interest, the transmission (B) and the required thickness X (mm of Pb) of the protective barrier is calculated by using the following formula:
B = P/T= 2-n (5)
E
E
where n: is the number of half-value layers required. The thickness of the half-value layer, for the polychromatic beam, varies with attenuation and the peak voltage. Its average HVL value is obtained by weighing the values indicated in Table V of this Schedule according to the desired attenuation.
E = Epri is written for the computation of the primary barrier.
and E = Esca + Ef for the computation of the secondary barrier.
And X = n (HVL) (6)
N.B. It is generally understood, in the case of devices of less than 500 kV, for the purposes of calculating shielding, that the average energy of the photons emitted is the same as that of the primary beam.
This method also applies to the computation of the thickness of barriers required to protect radiographic films. The film threshold exposure above which formation of shadows occurs being set at 0,2 m R, the value of the permissible exposure rate is determined by the formula:
P/T = 1.4\J mR/week.
where J: is the number of days during which the film remains in storage in proximity to a radiation source.
Weekly exposure, E, at this point is obtained by equations 1, 2 and 3 as warranted by the case.
The values contained in Tables VII to X of this Schedule for typical installations ensure sufficient shielding to reduce the exposure of pulsating potential devices to the level stipulated in this Regulation.
(Ref: NCRP Report No. 49 (Sept. 15, 1976). Structural Shielding Design and Evaluation for medical use of X Rays of Energies up to 10MEV. National Council on Radiation Protection and Measurements, 7910 Woodmont Avenue, Washington, D.C. Z0014.)
Table I
USE FACTORS U IN RADIOGRAPHY AND FLUOROSCOPY
Dental
X-rays Surface Radiography Radiography Fluoroscopy(3)
General Chest
Floor 1 N.A. 1/16 N.A.
Primary Walls 1/4 1 wall: 1 1/16 N.A.
Ceiling N.A. N.A. N.A. N.A.
Note: (1) N.A.: not applicable.
(2) For secondary radiation U = 1.
(3) U = 1 is used for calculating the protective barrier behind the camera.
Table II
OCCUPANCY FACTOR (T)
Full Partial Occasional
occupancy occupancy occupancy
(T = 1) (T = 1/4) (T = 1/16)
Control booth Waiting room Lavatories not
used by
radiological staff
Reception area Corridors too Unoccupied
narrow for offices storage rooms
Lavatories and Rest room not Stairways
rest rooms for used by radiological
radiological staff staff
Work rooms Automatic
Wards and elevators
patients’ rooms
Darkrooms Elevators with Sidewalks and
operator streets
Stores and shops Parking lots
Restaurants
Living quarters
Playgrounds and
play rooms
Neighbouring
offices
N.B. The occupancy factor for the controlled zone is equal 1.
Table III
f EXPOSURE RATE ACCORDING TO PEAK VOLTAGE AND FILTRATION
fn
FiltrationmR / mA-min
k Vc(mm AL) at 1m
500.5860
701.5470
1002.5570
1252.5760
1502.5980
N.B.Values at 50 and 70 k Vc. emanate from a self-rectified generator, 60 Hz.; those at 100, 125 and 150 k Vc. from a one-phase, rectified, full-wave generator. fn is a approximately double for 12-pulse triple phase devices.
fn
FiltrationmR / mA-min
k Vc(mm AL) at 1m
500.5860
701.5470
1002.5570
1252.5760
1502.5980
N.B.Values at 50 and 70 k Vc. emanate from a self-rectified generator, 60 Hz.; those at 100, 125 and 150 k Vc. from a one-phase, rectified, full-wave generator. fn is a approximately double for 12-pulse triple phase devices.
Table IV
RATIO, a, OF SCATTERED TO INCIDENT EXPLOSURE FOR A PULSATING POTENTIAL DEVICE
Scattering angle (from Central Ray)
k Vc 30° 45° 60° 90° 120° 135°
(X 10-3)
50 0.5 0.2 0.25 0.35 0.8 1.0
70 0.65 0.35 0.35 0.5 1.0 1.3
100 1.5 1.2 1.2 1.3 2.0 2.2
125 1.8 1.5 1.5 1.5 2.3 2.5
150 2.0 1.6 1.6 1.6 2.4 2.6
200 2.4 2.0 1.9 1.9 2.7 2.8
250 2.5 2.1 1.9 1.9 2.7 2.8
300 2.6 2.2 2.0 1.9 2.6 2.8
Ref. 3: See Ref. 1 of the Schedule.
Table V
HVL IN AVERAGE MM FOR LEADa
___________________________________________________________________________________
| |
TRANSMISSION B | PEAK VOLTAGE (KILOVOLTS) |
|______________________________________________________________|
| | | | | | | |
| 50 | 70 | 100 | 125 | 150 | 200 | 300 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
1 ≤ B < 10-1 | 0.01 | 0.01 | 0.05 | 0.08 | 0.11 | 0.19 | 0.27 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-1 ≤ B < 10-2 | 0.02 | 0.05 | 0.13 | 0.19 | 0.22 | 0.28 | 0.58 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-2 ≤ B < 10-3 | 0.03 | 0.09 | 0.24 | 0.25 | 0.28 | 0.36 | 1.01 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-3 ≤ B < 10-4 | 0.04 | 0.13 | 0.26 | 0.28 | 0.29 | 0.45 | 1.24 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-4 ≤ B < 10-5 | 0.05 | 0.15 | 0.27 | 0.29 | 0.30 | 0.51 | 1.37 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-5 ≤ B < 10-6 | 0.06 | 0.17 | 0.27 | 0.30 | 0.31 | 0.52 | 1.47 |
____________________|________|________|________|________|________|________|________|
a: These values were extracted from the curves of Fig. 1 and Fig. 2 of Appendix D
of NCRP Report No. 49. They therefore apply to radiation filtered according to
Table III.
| |
TRANSMISSION B | PEAK VOLTAGE (KILOVOLTS) |
|______________________________________________________________|
| | | | | | | |
| 50 | 70 | 100 | 125 | 150 | 200 | 300 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
1 ≤ B < 10-1 | 0.01 | 0.01 | 0.05 | 0.08 | 0.11 | 0.19 | 0.27 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-1 ≤ B < 10-2 | 0.02 | 0.05 | 0.13 | 0.19 | 0.22 | 0.28 | 0.58 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-2 ≤ B < 10-3 | 0.03 | 0.09 | 0.24 | 0.25 | 0.28 | 0.36 | 1.01 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-3 ≤ B < 10-4 | 0.04 | 0.13 | 0.26 | 0.28 | 0.29 | 0.45 | 1.24 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-4 ≤ B < 10-5 | 0.05 | 0.15 | 0.27 | 0.29 | 0.30 | 0.51 | 1.37 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-5 ≤ B < 10-6 | 0.06 | 0.17 | 0.27 | 0.30 | 0.31 | 0.52 | 1.47 |
____________________|________|________|________|________|________|________|________|
a: These values were extracted from the curves of Fig. 1 and Fig. 2 of Appendix D
of NCRP Report No. 49. They therefore apply to radiation filtered according to
Table III.
SCHEDULE 9
(ss. 195 and 198)
To determine the shielding of a diagnostic radiology installation, it is imperative to know:
(a) The permissible exposure rate at the considered point (P/T)
P: being the maximum permissible weekly exposure under section 195 of the Regulation, that is:
100 m Rem/week for controlled zone
10 m Rem/week for uncontrolled zones.
T: being the occupancy factor, that is, the fraction of the working week during which a sector is usually occupied.
N.B. When T is unknown, use the values represented in Table II.
(b) Weekly exposure at the point of interest (E m R/week)
For practical computation purposes, 3 distinct radiation sources are distinguished for each operating tube:
(1) the primary beam;
(2) the radiation scattered by the patient:
(3) the radiation leakage.
The corresponding values of E are computed by using the following formulas:
(1) Epri = fn W.U./(dprim.)2 (1)
(2) Esca = fna W F/400 (dsca)2 (dsec) 2 (2)
(3) Ef = fi W/d2sec (3)
(2) Esca = fna W F/400 (dsca)2 (dsec) 2 (2)
(3) Ef = fi W/d2sec (3)
where W: is the weekly workload expressed as mA-min/week.
U: the use factor: that is, the fraction of time during which the useful beam is directed towards the barrier or the target sector.
N.B. When unknown, the values represented in Table 1 of this Schedule are used.
dpri: the distance in metres between the point nearest the surface to be shielded and the position of mean use of the tube-head.
dsca: the distance in metres between the focus of the tube and the surface closest to the patient (focus-skin distance generally used and compatible with sections 153 and 154 of this Regulation).
dsec: the distance in metres between the scattering focus and the point of interest.
fn : the exposure rate per current unit of the contemplated device expressed in milliroentgen/milliampere/minute (mR/mA-min.). This value must be known or measured at a distance of one metre from the focus, within the primary beam filtered according to section 156 of this Regulation under normal operating conditions. Such measure of f must necessarily be made by a physicist using the appropriate instruments and depends on the voltage and the method of rectification. Table III indicates the values recently measured by Kelley and Trout for pulsating potential devices (Ref.: J.P. Kelley and E. Dale Trout, Radiology 104: 171-172 July 1972).
fi: the unit exposure rate expressed in (mR/mA-min.) due to the maximum permissible radioation leakage.
fi = fn/1000 is written (4)
fi: the unit exposure rate expressed in (mR/mA-min.) due to the maximum permissible radioation leakage.
fi = fn/1000 is written (4)
F: the size of the field used expressed in cm2.
a: the mean ratio of the quantity of radiation emitted to the primary radiation for a field of 400 cm2. Such ratio depends on the angle of scattering and on the tube potential. Values are given in Table IV of this Schedule.
Knowing the permissible exposure rate (P/T) and the radiation intensity (E) at the point of interest, the transmission (B) and the required thickness X (mm of Pb) of the protective barrier is calculated by using the following formula:
B = P/T= 2-n (5)
E
E
where n: is the number of half-value layers required. The thickness of the half-value layer, for the polychromatic beam, varies with attenuation and the peak voltage. Its average HVL value is obtained by weighing the values indicated in Table V of this Schedule according to the desired attenuation.
E = Epri is written for the computation of the primary barrier.
and E = Esca + Ef for the computation of the secondary barrier.
And X = n (HVL) (6)
N.B. It is generally understood, in the case of devices of less than 500 kV, for the purposes of calculating shielding, that the average energy of the photons emitted is the same as that of the primary beam.
This method also applies to the computation of the thickness of barriers required to protect radiographic films. The film threshold exposure above which formation of shadows occurs being set at 0,2 m R, the value of the permissible exposure rate is determined by the formula:
P/T = 1.4\J mR/week.
where J: is the number of days during which the film remains in storage in proximity to a radiation source.
Weekly exposure, E, at this point is obtained by equations 1, 2 and 3 as warranted by the case.
The values contained in Tables VII to X of this Schedule for typical installations ensure sufficient shielding to reduce the exposure of pulsating potential devices to the level stipulated in this Regulation.
(Ref: NCRP Report No. 49 (Sept. 15, 1976). Structural Shielding Design and Evaluation for medical use of X Rays of Energies up to 10MEV. National Council on Radiation Protection and Measurements, 7910 Woodmont Avenue, Washington, D.C. Z0014.)
Table I
USE FACTORS U IN RADIOGRAPHY AND FLUOROSCOPY
Dental
X-rays Surface Radiography Radiography Fluoroscopy(3)
General Chest
Floor 1 N.A. 1/16 N.A.
Primary Walls 1/4 1 wall: 1 1/16 N.A.
Ceiling N.A. N.A. N.A. N.A.
Note: (1) N.A.: not applicable.
(2) For secondary radiation U = 1.
(3) U = 1 is used for calculating the protective barrier behind the camera.
Table II
OCCUPANCY FACTOR (T)
Full Partial Occasional
occupancy occupancy occupancy
(T = 1) (T = 1/4) (T = 1/16)
Control booth Waiting room Lavatories not
used by
radiological staff
Reception area Corridors too Unoccupied
narrow for offices storage rooms
Lavatories and Rest room not Stairways
rest rooms for used by radiological
radiological staff staff
Work rooms Automatic
Wards and elevators
patients’ rooms
Darkrooms Elevators with Sidewalks and
operator streets
Stores and shops Parking lots
Restaurants
Living quarters
Playgrounds and
play rooms
Neighbouring
offices
N.B. The occupancy factor for the controlled zone is equal 1.
Table III
f EXPOSURE RATE ACCORDING TO PEAK VOLTAGE AND FILTRATION
fn
Filtration mR / mA-min
k Vc (mm AL) at 1m
50 0.5 860
70 1.5 470
100 2.5 570
125 2.5 760
150 2.5 980
N.B. Values at 50 and 70 k Vc. emanate from a self-rectified generator, 60 Hz.; those at 100, 125 and 150 k Vc. from a one-phase, rectified, full-wave generator. fn is a approximately double for 12-pulse triple phase devices.
fn
Filtration mR / mA-min
k Vc (mm AL) at 1m
50 0.5 860
70 1.5 470
100 2.5 570
125 2.5 760
150 2.5 980
N.B. Values at 50 and 70 k Vc. emanate from a self-rectified generator, 60 Hz.; those at 100, 125 and 150 k Vc. from a one-phase, rectified, full-wave generator. fn is a approximately double for 12-pulse triple phase devices.
Table IV
RATIO, a, OF SCATTERED TO INCIDENT EXPLOSURE FOR A PULSATING POTENTIAL DEVICE
Scattering angle (from Central Ray)
k Vc 30° 45° 60° 90° 120° 135°
(X 10-3)
50 0.5 0.2 0.25 0.35 0.8 1.0
70 0.65 0.35 0.35 0.5 1.0 1.3
100 1.5 1.2 1.2 1.3 2.0 2.2
125 1.8 1.5 1.5 1.5 2.3 2.5
150 2.0 1.6 1.6 1.6 2.4 2.6
200 2.4 2.0 1.9 1.9 2.7 2.8
250 2.5 2.1 1.9 1.9 2.7 2.8
300 2.6 2.2 2.0 1.9 2.6 2.8
Ref. 3: See Ref. 1 of the Schedule.
Table V
HVL IN AVERAGE MM FOR LEADa
___________________________________________________________________________________
| |
TRANSMISSION B | PEAK VOLTAGE (KILOVOLTS) |
|______________________________________________________________|
| | | | | | | |
| 50 | 70 | 100 | 125 | 150 | 200 | 300 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
1 ≤ B < 10-1 | 0.01 | 0.01 | 0.05 | 0.08 | 0.11 | 0.19 | 0.27 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-1 ≤ B < 10-2 | 0.02 | 0.05 | 0.13 | 0.19 | 0.22 | 0.28 | 0.58 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-2 ≤ B < 10-3 | 0.03 | 0.09 | 0.24 | 0.25 | 0.28 | 0.36 | 1.01 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-3 ≤ B < 10-4 | 0.04 | 0.13 | 0.26 | 0.28 | 0.29 | 0.45 | 1.24 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-4 ≤ B < 10-5 | 0.05 | 0.15 | 0.27 | 0.29 | 0.30 | 0.51 | 1.37 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-5 ≤ B < 10-6 | 0.06 | 0.17 | 0.27 | 0.30 | 0.31 | 0.52 | 1.47 |
____________________|________|________|________|________|________|________|________|
a: These values were extracted from the curves of Fig. 1 and Fig. 2 of Appendix D
of NCRP Report No. 49. They therefore apply to radiation filtered according to
Table III.
| |
TRANSMISSION B | PEAK VOLTAGE (KILOVOLTS) |
|______________________________________________________________|
| | | | | | | |
| 50 | 70 | 100 | 125 | 150 | 200 | 300 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
1 ≤ B < 10-1 | 0.01 | 0.01 | 0.05 | 0.08 | 0.11 | 0.19 | 0.27 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-1 ≤ B < 10-2 | 0.02 | 0.05 | 0.13 | 0.19 | 0.22 | 0.28 | 0.58 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-2 ≤ B < 10-3 | 0.03 | 0.09 | 0.24 | 0.25 | 0.28 | 0.36 | 1.01 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-3 ≤ B < 10-4 | 0.04 | 0.13 | 0.26 | 0.28 | 0.29 | 0.45 | 1.24 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-4 ≤ B < 10-5 | 0.05 | 0.15 | 0.27 | 0.29 | 0.30 | 0.51 | 1.37 |
____________________|________|________|________|________|________|________|________|
| | | | | | | |
10-5 ≤ B < 10-6 | 0.06 | 0.17 | 0.27 | 0.30 | 0.31 | 0.52 | 1.47 |
____________________|________|________|________|________|________|________|________|
a: These values were extracted from the curves of Fig. 1 and Fig. 2 of Appendix D
of NCRP Report No. 49. They therefore apply to radiation filtered according to
Table III.
