Public radiation dose calculation.

1. Investigations of public dose due to stray
radiation in X-ray installations in Mizoram
Jonathan Lalrinmawia1, Kham Suan Pau2
and Ramesh Chandra Tiwari*1.
1Department of Physics, Mizoram University, Aizawl-796004
2Mizoram State Cancer Institute, Zemabawk, Aizawl-796017
1MIZORAM SCIENCE CONGRESS 2016

2. OUTLINE
A. Introduction
B. Materials and Methods
C. Results and Discussion
- Exposure rates outside PED due to stray radiation during chest
mission
- Exposure rates outside PED due to stray radiation during couch
mission
- Workload in chest and couch mission
- Public dose due to stray radiation
D. Conclusions
E. Acknowledgement
F. References
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3. A. INTRODUCTION
W. C. Roentgen established physical characteristics of his new found
rays almost fully within a short period of time. These rays
were not only magnificent and useful in medicine, but
dangerous too.
Until the 1950s, scientific reports that concerned late radiation effects
of low levels radiation exposure did not appear. The somatic
late effects are leukemia and other malignancies. Genetic
material can also be harm and the effect can only become
evident in future generation.
These lead to the radiation protection regulations of today. The
International Commission for Radiation Protection (ICRP) is
the international regulatory body. Each country has its own
national counterpart of the ICRP and in India it is the Atomic
Energy Regulatory Board (AERB).
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4. A. INTRODUCTION
These bodies recommend norms for permissible doses limits for
radiation workers and the general public. The shielding
required for the walls of an X-ray room etc..
In the present study we are measuring the exposure rates outside
Patient Entrance Door (PED) which are originated from the
tube as leakage radiation and scattered radiation mainly
from the patient. And compare to national safety standard.
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5. B. MATERIALS AND METHODS
To measure stray radiation; pressurized ion chamber survey meter
(Model 451P, FLUKE) is used. The calibration measurements are
traceable to the National Institute of Standard and Technology (NIST).
There are 67 units in the present study; which are install in 48
different institutions (Table 1).
Table 1: Detail diagnostic X-ray facilities installation in the present study.
Working &
Out of Order Aizawl’E Champhai Kolasib Mamit Saiha Lawngtlai Lunglei Serchhip Total
No of Ins 4 11 6 3 3 4 12 5 48
Fixed X-ray 1 4 4 1 2 5 7 2 26
Mibile -Fixed 3 8 4 3 2 3 9 4 36
Mobile 0 0 0 1 0 0 2 0 3
Dental 0 0 1 0 1 0 0 0 2
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6. B. MATERIALS AND METHODS
Out of 67 units, 25 units are not measurable in this parameter (Table
2).
Table 2: Detail of diagnostic X-ray facilities which is not study
Public dose are calculated from 37 units which cover Mizoram except
Aizawl West division. In this study, 63% diagnostic X-ray units are
AERB type approved unit and 37% are not known type .
Reason Champhai Kolasib Mamit Saiha Lawngtlai Lunglei Serchhip Total
Out of order 3 2 3 2 0 5 1 16
Mobile 0 0 1 0 0 2 0 3
Not Installed 1 0 0 0 2 1 0 4
Dental 0 1 0 1 0 0 0 2
Total 4 3 4 3 2 8 1 25
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7. B. MATERIALS AND METHODS
Sketches are made for all installations indicating dimensions of the
room, x-ray source, couch, chest stand and PED. Distance from chest
stand to PED and couch to PED as well as type of door are measured
and recorded.
A water phantom is used as a source of scattered which is placed on
couch for vertical exposure and at a chest stand for horizontal
exposure. Field sizes are adjusted to maximum; focused at the water
phantom and exposed by setting maximum accelerating potential
and minimum current with fixed exposure time (Table 3).
Table 3: X-ray input parameters used for dose rate measurements at PED
Parameters Set value As per reference
Accelerating Potential 85 to 120kV Maximum kV
Current 25 to 50mA Minimum mA
Time 1s Fixed
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8. B. MATERIALS AND METHODS
(In this set up, the survey could measure radiations scattered from
the phantom, the walls, the floor and the ceiling as well as leakage
radiation)
Workload is calculated for each installation by using the relation
(NCRP, 2004);
Dose is calculated using the relation;
Where, mA is the set input current in survey.
.min 1 1
60
mR mA mR
Dose Workload ExposureRates
Week Week h mAused
         
            
         
min 1min
60
mA patients films mAs days
W
Week day patient film week s
 
     
 
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9. C. RESULTS AND DISCUSSION
1. Exposure rates outside PED during chest mission
5% installations are not having any type door and 95% are using
wooden door for protection. Exposure rates for installations with
wooden door ranges from 0.001 to 200mR/h and without door 3.1 to
3.9mR/h.
200
0
50
100
150
200
250
90 270 280 310 345 350 360 380 390 390 400 430 433 440 442 458 500 570 700
DoseRate(mR/h)
No of X-ray Units
PED Dose Rate Due to Chest Mission
Figure 1: Distance effects on exposure rate in chest mission.
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10. C. RESULTS AND DISCUSSION
There is a negative moderate relation between distance and exposure
rates in public places (Table 4).
Chest to PED
Chest dose
rate
Chest to PED Pearson Correlation 1 -.404*
Sig. (2-tailed) .013
N 37 37
Chest dose rate Pearson Correlation -.404* 1
Sig. (2-tailed) .013
N 37 37
*. Correlation is significant at the 0.05 level (2-tailed).
Table 4 : Correlations between Distance & Dose rate
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11. D. RESULTS AND DISCUSSION
2. Exposure rates outside PED during couch mission
Exposure rates at public place for installations using wooden door
ranges from 0.02 to 185mR/h and no door 0.245 to 1.8mR/h. There is
no lead line door in our study area and wooden door for protection
has no significant impact on radiation rates.
185 180
0
50
100
150
200
130 175 190 204 220 230 240 290 300 310 340 350 360 378 380 390 430 458 500 560
DoseRate(mR/h)
No of X-ray Units
PED Dose Rate Due to Couch Mission
Figure 2: Distance effects on exposure rate in couch mission.
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12. D. RESULTS AND DISCUSSION
There is a negative weak relation between distance and exposure rate
in couch mission (Table 5).
Couch to PED Couch Dose Rate
Couch to PED Pearson Correlation 1 -.260
Sig. (2-tailed) .110
N 39 39
Couch Dose Rate Pearson Correlation -.260 1
Sig. (2-tailed) .110
N 39 39
Table 5: Correlations between Distance & Dose rate
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13. D. RESULTS AND DISCUSSION
3. Workload
The general diagnostic X-ray examinations are chest, skull, abdomen,
pelvic and extremities. Chest examination in chest stand required
horizontal projection of x-ray, whereas all other examinations are
done on couch in vertical projections. The number of films used;
current (mA); time (s) applied in different institutions for different X-
ray examinations are shown in Table 6.
Table 6: No of Films and mAs applied for different X-ray examinations.
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Examinations Chest Skull Abdomen Pelvic IVP Extremeties
Films per examination 1 or 2 2 1 or 2 1 or 2 5 or 6 1 or 2
mAs per Examination 6 to 50 30 to 120 18 to 120 30 to 120 20 to 120 12 to 120

14. D. RESULTS AND DISCUSSION
Only 10% units are having workload more than 100mA.min/week;
90% units are having workload less than 100mA.min/week.
504
0
100
200
300
400
500
600
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Workload(mAmin/week)
No. of X-ray Units
Chest
Couch
Total Workload
Figure 3: Workload, chest mission; couch mission; total.
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15. D. RESULTS AND DISCUSSION
4. Public Doses
Public dose at PED in chest mission ranges from 2.08 X 10-5 to
0.325mR/week and 5.3X10-5 to 2.2744mR/week in couch mission (Fig
4). According to AERB safety code, there is 1 unit, which shows
excessive radiation dose at public places 2.524375mR/week.
2.524375
1.47402
0
0.5
1
1.5
2
2.5
3
1 3 5 10 15 17 20 22 24 26 29 31 33 36 38 41 46 52 55
PublicDose(mR/week)
No. of X-ray Units
Chest Mission Dose
Couch Mission Dose
Total Dose
Figure 4: Public dose, chest mission; couch mission; total.
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16. D. RESULTS AND DISCUSSIONS
In comparing fixed X-ray and mobile X-ray, there is no difference in
public dose when the tube loading of mobile unit is same as fixed unit
(Fig 5).
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0
0.5
1
1.5
2
2.5
3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
PublicDose(mR/week)
No of x-ray Units
Fixed X-ray
Mobile X-ray
Figure 5: Public dose; fixed X-ray and mobile X-ray
16

17. D. RESULTS AND DISCUSSION
There is a moderate relation between chest dose and chest rates;
strong correlation between couch doses and couch rates as shown in
the following tables.
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Table 8: Correlations between dose and
exposure rates in Couch Mission
CouchDose
CouchExpr
ates
CouchDose Pearson
Correlation
1 .808**
Sig. (2-tailed) .000
N 34 34
CouchExprates Pearson
Correlation
.808** 1
Sig. (2-tailed) .000
N 34 34
**. Correlation is significant at the 0.01 level (2-tailed).
Table 7: Correlations between dose and
exposure rates in Chest Mission
ChestDose
ChestExpra
tes
ChestDose Pearson
Correlation
1 .548**
Sig. (2-tailed) .001
N 33 33
ChestExprates Pearson
Correlation
.548** 1
Sig. (2-tailed) .001
N 33 33
**. Correlation is significant at the 0.01 level (2-tailed).
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18. D. RESULTS AND DISCUSSION
And we have a weak relation between dose and workload in different
institutions as shown in the following tables. This means that
exposure rates is the main factor of public dose.
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Table 10: Correlations between dose and
workload in Couch Mission
CouchDose CouchWld
CouchDose Pearson Correlation 1 .135
Sig. (2-tailed) .445
N 34 34
CouchWld Pearson Correlation .135 1
Sig. (2-tailed) .445
N 34 34
Table 9: Correlations between dose and
workload in Chest Mission
ChestDose ChestWld
ChestDose Pearson Correlation 1 .117
Sig. (2-tailed) .517
N 33 33
ChestWld Pearson Correlation .117 1
Sig. (2-tailed) .517
N 33 33
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19. E. CONCLUSIONS
• It is found that there is no lead-line door for radiation protection
and none of the installations have warning light to warn
persons at the waiting area.
•There is no significant difference between installations with wooden
door and without door in exposure rates at public place.
•Exposure rate is the main factor of public dose while the present
workload has no significant effect on public dose.
•According to AERB safety code, 1 installation is out of acceptance
limit 2mR/week (AERB, 2001). If a mobile X-ray is used as
mobile-fixed in a fixed proper room, the shielding required is
same as fixed X-ray.
•However, high exposure rates at public place can be significantly
reduced by employing lead lined door and proper shielding as
per safety regulation.
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20. F. AKNOWLEDGEMENT
The authors would like to thank Committee for Safety Research
Programme (CSRP), Atomic Energy Regulatory Board (AERB)
Government of India for financial assistance through Project
No.AERB/CSRP/58/02/2014 Dated September 30, 2014 for
completion of this work.
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21. G. REFERENCES
AERB, (2016). Safety Code No. AERB/RF-MED/SC-3 (Rev. 2), ‘Radiation Safety in
Manufacture, Supply and Use of Medical Diagnostic X-ray Equipment’,
AERB, Mumbai.
AERB, (2001). Safety Code No. AERB/SC/MED-2 (Rev. 1), ‘Safety Code for Medical
Diagnostic X-ray equipment and installations’ AERB, Mumbai.
Bushong SC. (1991). Radiation protection. In: Ballinger PW, editor. 7th ed. Merrill’s
atlas of radiographic positions and radiologic procedures, vol. 1. St.
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Grover S B, Kumar J, Gupta A and Khanna L. (2002). Protection against hazards:
Regulatory bodies, safety norms, dose limits and protection devices.
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Maree GJ. (1995). Determination of the genetically-significant dose from diagnostic
radiology for the South African population 1990 – 1991. PhD Thesis of the
University of Cape Town, South Africa.
NCRP (2004) Report No. 147. Structural Shielding Design for Medical X-ray Imaging
Facilities.
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22. G. REFERENCES
Operator manual 451P Ion Chamber Survey Meter, (2013). PN FBC-0059, Rev 1,
Fluke Corporation, USA.
Seeram E and Travis EC, (1997) Radiation protection, Philadelphia, New York,
Lippincott.
Sonawane A. U., Meghraj Singh, Sunil Kumar J. V. K., Kulkarni Arti, Shirva V. K., and
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