18F Protection Issues: Human and γ-Camera Considerations

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FIGURE 1.
Experimental setup. ¹⁸F source was placed directly behind lead shield. Dose rates were measured on other side of lead shield at different distances from source using high-pressure ionization chamber.
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FIGURE 2.
Dose rates of ¹⁸F vial (• and solid curve) and cylinder (▪ and dashed curve) in air as function of distance. Both curves were obtained by fitting to data points using inverse square function. Fitting result is given in Equation 3.

TABLE 1

Dose Rates of ¹⁸F Vial and ¹⁸F Cylinder in Air

Distance (m)	Vial dose rate (μGy/h/370 MBq)	Cylinder dose rate (μGy/h/370 MBq)	Cylinder/vial dose-rate ratio
0.10	3,686	2,662	0.72
0.50	226	150	0.66
1.00	63.3	38.0	0.60
1.50	30.5	17.2	0.56
2.00	14.3	10.1	0.71
2.50	9.32	6.50	0.70
3.00	6.25	4.51	0.72
3.50	4.85	2.90	0.60
4.00	3.93	2.47	0.63
4.50	3.27	1.67	0.51
5.00	2.55	1.29	0.51
5.50	1.80	0.86	0.48

TABLE 2

Dose Rates of ¹⁸F Vial in Air and Shielded with 0.318 or 5.08-cm-Thick Lead

Distance (m)	Dose rate in air (μGy/h/370 MBq)	0.318-cm lead shielding			5.08-cm lead shielding
Distance (m)	Dose rate in air (μGy/h/370 MBq)			Dose rate (μGy/h/370 MBq)	Lead/in-air dose-rate ratio	Dose rate (μGy/h/370 MBq)	Lead/in-air dose-rate ratio
0.50	226	136	0.60	4.53	0.020
1.00	63.3	35.0	0.55	2.48	0.039
1.50	30.5	15.9	0.52	1.39	0.046
2.00	14.3	8.99	0.63	0.56	0.039
2.50	9.32	5.44	0.58
3.00	6.25	4.06	0.65
3.50	4.85	2.95	0.61
4.00	3.93	2.34	0.60
4.50	3.27	1.76	0.54
5.00	2.55	1.19	0.47

TABLE 3

Measured and Calculated Dose Rates of ¹⁸F Vial Shielded with 0.318-cm-Thick Lead

Distance (m)	Measured dose rate (μGy/h/370 MBq)	Calculated dose rate* (μGy/h/370 MBq)	Measured/calculated dose-rate ratio
0.50	136	132.8	1.02
1.00	35.0	33.2	1.05
1.50	15.9	14.8	1.08
2.00	8.99	8.3	1.08
2.50	5.44	5.3	1.02
3.00	4.06	3.7	1.10
3.50	2.95	2.7	1.09
4.00	2.34	2.1	1.13
4.50	1.76	1.6	1.07
5.00	1.19	1.3	0.90

↵* Calculated using Equation 1 with I₀ the in-air dose rate given by Equation 3 for same distance.