Location of the ovaries in children and efficacy of gonadal shielding in hip and pelvis radiography.

BACKGROUND: Patients with hip disorders undergo multiple radiographic examinations, so gonadal radiation risk should be minimized. Inaccurate shield placement, including obscuring landmarks, has been widely reported, and some studies reported that covering the true pelvis was inappropriate to shield young girls' ovaries. However, no reports on ovaries in Asian patients identified on magnetic resonance imaging exist. We aimed to identify the location of the ovaries in Japanese children and assess the efficacy of gonadal shielding. METHODS: Female patients aged ≤16 years who underwent magnetic resonance imaging for hip disorders that displayed at least one ovary were included. Sixty ovaries from 31 patients were classified into two age groups: <2 years and >2 years, and the ovaries' position was classified according to the following four zones on the anteroposterior pelvic radiograph: zone 1 (true pelvis) - area surrounded by the line of the anterior superior iliac spines, inner side walls of the ilium, and symphysis pubis; zone 2 - areas lateral to zone 1; zone 3 - sacral area superior to zone 1; and zone 4 - areas lateral to zone 3. The ovaries' position was analyzed according to age group. RESULTS: Thirty-one ovaries in 16 patients were <2 years, and 29 ovaries in 15 patients were >2 years. Thirteen ovaries in the true pelvis, 18 ovaries in the false pelvis were <2 years, and 27 in the true pelvis and 2 in the false pelvis were in >2 years. In girls aged <2 years, most ovaries in the false pelvis were located in zone 3. CONCLUSIONS: Girls aged >2 years mostly have their ovaries in the true pelvis, and ovaries in infants tend to be located superior to the true pelvis. Covering the true pelvis is plausible for shielding ovaries. Shields should be placed slightly more cranially than the true pelvis for infants.

Gonadal shield: is it the Albatross hanging around the neck of developmental dysplasia of the hip research?

PURPOSE: Prospective randomized controlled trials and long-term studies are essential future directions for building -evidence-based practices in developmental dysplasia of the hip (DDH), however, sufficient attrition in data (> 20%) can introduce bias deteriorating research quality. Pelvic radiography is synonymous with DDH assessment and so are -Gonadal Shield (GS) recommendations with pelvic radiography. -Nonetheless, losses to diagnostic information and inadequate protection have been increasingly implicated to GS usage, with significantly worse implications in female patients. Understandably for DDH, a disease with 80% female prevalence, the impact of GS usage on quality of radiographs and readability of radiological data may be drastic. This study aims to objectively define the implications of GS recommendations in DDH patients. METHODS: Pelvis radiographs of all DDH patients under the hip surveillance programme at a tertiary care hospital with a written protocol for GS usage were evaluated. Images were reviewed for gender, GS presence, adequate gonadal protection and obstruction of essential anatomical landmarks for pelvic indices. RESULTS: In all, 131 pelvis radiographs with DDH diagnoses (age: 1.25 to 6 years; 107 female, 24 male pelvises) were reviewed. Only 42.67% (56) of pelvis radiographs used GS despite the presence of a clear protocol. Useful anatomical landmarks were obstructed in 58.9% of radiographs with GS present. Lost diagnostic information was more common in female patients than male patients (68.1% versus 11.1%, p < 0.01). GS was ineffective at gonadal protection in 73.2% (41) of the pelvises with worse protection in female patients (78.7% vs 44.4%; p = 0.03). CONCLUSIONS: Ironically, essential anatomy was obstructed in all the adequately protected female pelvises. Routine GS usage results in substantial attrition of radiographic data in DDH patients. LEVEL OF EVIDENCE: III.

Female gonadal shielding with automatic exposure control increases radiation risks.

BACKGROUND: Gonadal shielding remains common, but current estimates of gonadal radiation risk are lower than estimated risks to colon and stomach. A female gonadal shield may attenuate active automatic exposure control (AEC) sensors, resulting in increased dose to colon and stomach as well as to ovaries outside the shielded area. OBJECTIVE: We assess changes in dose-area product (DAP) and absorbed organ dose when female gonadal shielding is used with AEC for pelvis radiography. MATERIALS AND METHODS: We imaged adult and 5-year-old equivalent dosimetry phantoms using pelvis radiograph technique with AEC in the presence and absence of a female gonadal shield. We recorded DAP and mAs and measured organ absorbed dose at six internal sites using film dosimetry. RESULTS: Female gonadal shielding with AEC increased DAP 63% for the 5-year-old phantom and 147% for the adult phantom. Absorbed organ dose at unshielded locations of colon, stomach and ovaries increased 21-51% in the 5-year-old phantom and 17-100% in the adult phantom. Absorbed organ dose sampled under the shield decreased 67% in the 5-year-old phantom and 16% in the adult phantom. CONCLUSION: Female gonadal shielding combined with AEC during pelvic radiography increases absorbed dose to organs with greater radiation sensitivity and to unshielded ovaries. Difficulty in proper use of gonadal shields has been well described, and use of female gonadal shielding may be inadvisable given the risks of increasing radiation.

Testicular shield for para-aortic radiotherapy and estimation of gonad doses.

For radiotherapy of para-aortic and abdominal regions in male patients, gonads are to be protected to receive less than 2% of the prescribed dose. A testicular shield was fabricated for abdominal radiotherapy with 15 MV X-rays ((Clinac 2300 CD, Varian AG) with low melting point alloy (Cerroband). The dimensions of the testicular shield were 6.5 cm diameter and 3.5 cm depth with 1.5 cm wall thickness. During treatment, this shield was held in position by a rectangular sponge and Styrofoam support. Phantom measurement was carried out with a humanoid phantom and a 0.6 cc ion chamber. The mean energy of the scattered photon was calculated for single scattering at selected distances from the beam edge and with different field dimensions. One patient received radiotherapy with an inverted Y field and gonad doses were estimated using calibrated thermo-luminescent detector (TLD) chips. Measured doses with the ion chamber were 7.1 and 3.5% of the mid-plane doses without a shield at 3 and 7.5 cm off-field respectively. These values decreased to 4.6 and 1.7% with the bottom shield alone, and to 1.7 and 0.8% with both bottom and top shields covering the ion chamber. The measured doses at the gonads during the patient's treatment were 0.5-0.92% for the AP field (0.74 +/- 0.17%, n = 5) and 0.5-1.2% for the PA field (0.88 +/- 0.24%, n = 5). The dose received by the testis for the full course of treatment was 32 cGy (0.8%) for a total mid-plane dose of 40 Gy. The first-scatter energy estimated at the gonads is around 1.14 MeV for a primary beam of 15 MV for a long axis dimension of 37 cm of primary field. During the patient's treatment, the estimated absorbed doses at the gonads were comparable with reported values in similar treatments. The testicular shield reported in this study is of light weight and could be used conveniently in treatments of abdominal fields.