1. Lead versus bismuth-antimony shield for fetal dose reduction at different gestational ages at CT pulmonary angiography.
- Author
-
Chatterson LC, Leswick DA, Fladeland DA, Hunt MM, and Webster ST
- Subjects
- Antimony, Bismuth, Female, Gestational Age, Humans, Imaging, Three-Dimensional, Lead, Phantoms, Imaging, Pregnancy, Radiation Dosage, Statistics, Nonparametric, Thermoluminescent Dosimetry, Angiography methods, Fetus radiation effects, Radiation Protection instrumentation, Tomography, X-Ray Computed
- Abstract
Purpose: To compare the effective fetal dose reduction at different stages of gestation during maternal computed tomographic (CT) pulmonary angiography by using traditional lead apron and bismuth-antimony shields combined with limited z-axis and tube current., Materials and Methods: Phantom with gravid prosthesis, 0.5-mm lead, and two grades of bismuth-antimony shield was used. Thermoluminescent dosimeters (TLDs) measured radiation in the first- to third-trimester uterus. Fetal dose was determined for each gestation by using 100 kVp to the costophrenic angles (CPAs) with and without shielding for a total of 12 scans. Eight third-trimester scans were used to compare shields using 120 kVp to CPAs versus those using 100 kVp to the diaphragm., Results: Average fetal dose increased with gestation with use of 100 kVp to CPAs, from 0.11 mGy in first trimester to 0.50 mGy in third trimester. Average third-trimester unshielded fetal dose was reduced from 0.82 mGy by using 120 kVp to CPAs to 0.17 mGy (79%, P < .001) by using 100 kVp to the diaphragm. Lead apron reduced dose more than either of the bismuth-antimony shields (72%-79% vs 57%-81%) with use of 100 kVp to CPAs. Shields reduced the dose by 73% (lead), 62% (90% attenuation bismuth-antimony), and 72% (95% attenuation bismuth-antimony) (P < .01) at 120 kVp to CPAs. No significant difference between shields was demonstrated with 100 kVp to the diaphragm (P < .01). Maternal dose was 8.13 mSv at 120 kVp to CPAs, 4.90 mSv at 100 kVp to CPAs, and 4.02 mSv at 100 kVp to the diaphragm., Conclusion: Reducing voltage and limiting z-axis is more effective than shields at reducing fetal dose. Shielding improves reduction with no significant difference between lead and bismuth-antimony shields when conservative scanning parameters are observed., (© RSNA, 2011.)
- Published
- 2011
- Full Text
- View/download PDF