Evaluation of radiation exposure upon visual organs during a head CT scan

Figures & data

Figure 1. Anatomical position and constitution of the Phantom.

Table 1. Composition of the tissues for the phantoms.

Element	Percent by weight
	Brain	Skeleton	Eye^a
H	10.454	7.337	10.7
C	22.663	25.475	3.8
N	2.490	3.057	1.2
O	63.525	47.893	84.3
F	0	0.025	0
Na	0.112	0.326	0
Mg	0.013	0.112	0
Si	0.030	0.002	0
P	0.134	5.095	0
S	0.204	0.173	0
Cl	0.133	0.143	0
K	0.208	0.153	0
Ca	0.024	10.190	0
Fe	0.005	0.008	0
Zn	0.003	0.005	0
Rb	0.001	0.002	0
Sr	0	0.003	0
Zr	0.001	0	0
Pb	0	0.001	0
Density	1.04 g/cm^3	1.4 g/cm^3	1.03 g/cm^3
Note: ^aInclusion of lens and cornea.

Table 2. Estimation of the absorbed dose of the head, eyes, corneas, and lenses according to energy level.

Organ	Energy
	80 kV (mGy)	Brain/rate (%)	100 kV (mGy)	Brain/rate (%)	120 kV (mGy)	Brain/rate (%)
Eye	0.425	1.353	0.515	1.355	0.623	1.354
Cornea	0.285	0.907	0.35	0.920	0.423	0.921
Lens	0.030	0.095	0.036	0.094	0.044	0.094
Brain	31.38	100	38.02	100	45.97	100

Table 3. Estimation of the absorbed dose of the head, eyes, corneas, and lenses when using an eye shield (thickness of shield: 0.5 mm).

Organ	Energy
	80 kV (mGy)	Brain/rate (%)	100 kV (mGy)	Brain/rate (%)	120 kV (mGy)	Brain/rate (%)
Eye	0.332	1.087	0.393	1.067	0.489	1.094
Cornea	0.229	0.749	0.276	0.749	0.343	0.766
Lens	0.019	0.062	0.022	0.059	0.029	0.065
Brain	30.51	100	36.85	100	44.68	100

Table 4. Estimation of the absorbed dose of the head, eyes, corneas, and lenses when using an eye shield (thickness of shield: 1.0 mm).

Organ	Energy
	80 kV (mGy)	Brain/rate (%)	100 kV (mGy)	Brain/rate (%)	120 kV (mGy)	Brain/rate (%)
Eye	0.313	1.033	0.383	1.043	0.468	1.053
Cornea	0.217	0.714	0.269	0.732	0.328	0.738
Lens	0.017	0.055	0.020	0.056	0.026	0.059
Brain	30.32	100	36.74	100	44.46	100

Table 5. Estimation of the absorbed dose of the head, eyes, corneas, and lenses when using an eye shield (thickness of shield: 1.5mm).

Organ	Energy
	80 kV (mGy)	Brain/rate (%)	100 kV (mGy)	Brain/rate (%)	120 kV (mGy)	Brain/rate (%)
Eye	0.309	1.020	0.381	1.038	0.464	1.046
Cornea	0.214	0.706	0.268	0.730	0.326	0.733
Lens	0.016	0.053	0.020	0.056	0.026	0.058
Brain	30.26	100	36.71	100	44.40	100

Figure 2. Absorbed dose reduction rate before and after use of an eye shield. (a) 80 kV. (b) 100 kV. (c) 120 kV.