Scattered radiation in function of voltage
The change between 77 and 81 kVp may be due the transition between the Compton effect and photoelectric effect.
Voltage and exposure were correlated and linear regression analysis confirmed that the radiation secondary is directly proportional to the voltage (R = 0.9994) (Figure 1).
Scattered radiation in function of the current-time product
The variation of the scattered radiation is similar for both configurations because it increases with the increase of the current-time product (Figure 2).
The correlation between the scattered radiation and the current-time product showed that the secondary radiation is directly proportional to the current-time product (R = 0.9995).
Scattered radiation in function of the angle of the dosimeter
Graphics created designated by isodose curves in two dimensions for the three configurations.
These are the variations of the distance that are measured with constant radiation dose depending on the angle around the patient (Figure 3).
Scattered radiation in function of the height of the dosimeter
The intensity of the scatter radiation is higher from above 100cm.
At 120 and 130cm the scatter radiation reaches its maximum.
Between 20 and 40cm and 60-80cm there are variation of the scatter radiation which may be explained by metallic structures of the litter (Figure 4).
Scattered radiation in function of the distance of the dosimeter
Comparing the measured values with the framework theory,
both results overlap from 1m due to the inverse square law.
Up to this distance,
the measured values are different because the patient simulates a set of multiple sources (Figure 5).
Estimation of exposure
To estimate workers exposure we considered a Radiographer day's work,
25 exposures,
with voltage and current-time product of 77 kVp and 2.5 mAs,
respectively. The average value of the scattered radiation is of 3.29 x 10-4 mSv (obtained from Figure 1 and 2) for 1 m.
Based on the inverse square law,
we determined various exposures on the Radiographer in relation to the center of the IP (0.5,
2.00,
3.00,
4.00 and 5.00 m,
were 1.32 × 10-3,
8.23 × 10-5,
3.66 × 10-5,
2.06 × 10-5 e 1.32 × 10-5 mSv,
respectively).
Figure 6/ equation 1 allowed to calculate the exposure per year: 12 mSv/year to 0.5 m,
3 mSv/year to 1.00 m,
0.75 mSv/year to 2.00 m,
0.33 mSv/year to 3.00 m,
0.19 mSv/year to 4.00 m and 0.12 mSv/year to 5.00 m.
For members of the public we considered 5 exposures in a day. Thus,
patients in the nearby beds would be exposed to radiation scattered by five times.
Making the explicit calculations previously (equation 4),
the results obtained for 0.5,
1.00,
2.00,
3.00,
4.00 and 5.00 m were 2.4,
0.6,
0.15,
0.067,
0.038 and 0.024 mSv/year,
respectively.