Corneal Dose Reduction Using a Bismuth-Coated Latex Shield over the Eyes During Brain SPECT/CT

Abstract

This study aimed to determine whether a bismuth-coated latex shield (B-shield) could protect the eyes during brain SPECT/CT. A shield containing the heavy metal bismuth (equivalent to a 0.15-mm-thick lead shield) was placed over a cylindric phantom and the eyes of a 3-dimensional brain phantom filled withTc solution. Subsequently, phantoms with and without the B-shield were compared using SPECT/CT. The CT parameters were 30-200 mA and 130 kV. The dose reduction achieved by the B-shield was measured using a pencil-shaped ionization chamber. The protective effects of the B-shield were determined by evaluating relative radioactivity concentration as well as artifacts (changes in CT number), linear attenuation coefficients, and coefficients of variation on SPECT images. The radiation doses with and without the B-shield were 0.14-0.77 and 0.36-1.93 mGy, respectively, and the B-shield decreased the average radiation dose by about 60%. The B-shield also increased the mean CT number, but only at locations just beneath the surface of the phantom. Streaks of higher density near the underside of the B-shield indicated beam hardening. Linear attenuation coefficients and the coefficients of variation did not significantly differ between phantoms with and without the B-shield, and the relativeTc radioactivity concentrations were not affected. The B-shield decreased the radiation dose without affecting estimated attenuation correction or radioactivity concentrations. Although surface artifacts increased with the B-shield, the quality of the SPECT images was acceptable. B-shields can help protect pediatric patients and patients with eye diseases who undergo SPECT imaging.

Bismuth Pelvic X-Ray Shielding Reduces Radiation Dose Exposure in Pediatric Radiography

“…A Slovakian study verified the effectiveness of bismuth shields for radiation protection of the eyes and thyroid in CT exams, which had increased markedly in the last decade in that country; radiation load was decreased in the majority of procedures in several clinical departments, although the authors emphasized that establishment of correct exposure settings was essential in supporting such reductions [ 13 ]. Matsutomo et al [ 14 ] found that bismuth-coated latex shields decreased radiation doses of brain SPECT/CT by about 60% without changing attenuation correction or radioactivity concentration. In a study that evaluated a series of phantoms using different thicknesses of shields with both Pb and bismuth demonstrated that a small thickness of bismuth (0.2 mm) or lead shield (0.4 mm) caused significant reduction in absorbed dose and concluded the presence of shield did not affect image quality if superficial organs are not the target of CT imaging and that bismuth or lead shielding technique is an useful and valuable tool in CT to reduce radiation risk in children [ 16 ].…”

Radiation-Induced Cerebro-Ophthalmic Effects in Humans

“…The results of the so-called "Pittsburgh Project and the Ukrainian-American Chernobyl Ocular Study" (UACOS) showed a significantly higher frequency of posterior subcapsular opacities of the lens following IR, especially in the children irradiated with doses higher than 400 mG [12][13][14]. Data from monitoring children undergoing long-term low-intensity IR exposure in Taiwan confirmed these findings [15].…”