Gonad shielding in pelvic radiography: modern optimised X-ray systems might allow its discontinuation

Insights into Imaging

Table 5 Detriment-adjusted risks for adults of reproductive age caused by AP pelvic radiography

Year	Origin of data at basis of calculation	Total risk X-ray without shielding^a		Total risk X-ray with shielding^b		Reduction risk by shielding gonads^c
		Males	Females	Males	Females	Males	Females
		per 10⁶	per 10⁶	per 10⁶	per 10⁶	per 10⁶	per 10⁶
1905	Beck, Biddle, Albers-Sch	1075	341	308	307	767	35
1958	Janker, Lincoln	116	47	39	41	77	5.6
2010	“European” DRL^d (RP180)	40	23	17	19	23	3.3
2017	Dutch target DRL^d	20	11	8.5	9.7	12	1.7
2018	MUMC+	8.6	5.4	4.0	4.6	4.6	0.77

^a Using abbreviations R = detriment-adjusted risk, E = effective dose and H = equivalent dose, the risk was approximated as R_male = 5.5 × 10⁻² × {E − 0.04 × (H_Testes + H_Ovaries)} + 5.4 × 10⁻³ × H_testes and analogously for females. Applied for instance to “1958 males without shielding”, this gives R_male = 5.5 × 10⁻² × {1.32 × 10⁻³ − 0.04 × (15 × 10⁻³ + 2.1 × 10⁻³)} + 5.4 × 10⁻³ × 15 × 10⁻³ = 116 × 10⁻⁶. Note that we used data from Table 3 and that the equivalent dose equals the absorbed dose multiplied by the relative biological effectiveness of the radiation causing the absorbed dose. For X-rays, this factor is 1 Sv/Gy, so absorbed and equivalent dose are numerically equal
^b With gonad shielding, the last term in R_male is modified into: 5.4 × 10⁻³ × (1 − GS) × H_Testes, with GS the shielding factor of 0.95 for males. Analogously for females, but with GS = 0.5
^c Decrease in total risk resulting from the reduction in hereditary (“gonad”) risk by shielding
^d Most common European DRL, i.e. KAP = 3.0 Gy cm²; Dutch target DRL is KAP = 1.5 Gy m²