Evaluation of radiation dose reduction during CT scans by using bismuth oxide and nano-barium sulfate shields

Abstract

The purpose of the present study was to evaluate radiation dose reduction and image quality during CT scanning by using a new dose reduction fiber sheet (DRFS) with commercially available bismuth shields. These DRFS were composed of nano-barium sulfate (BaSO 4 ), filling the gaps left by the large oxide bismuth (Bi 2 O 3 ) particle sizes. The radiation dose was measured five times at directions of 12 o'clock from the center of the polymethyl methacrylate (PMMA) head phantom to calculate an average value using a CT ionization chamber. The image quality measured CT transverse images of the PMMA head phantom depending on X-ray tube voltages and the type of shielding. Two regions of interest in CT transverse images were chosen from the right and left areas under the surface of the PMMA head phantom and from ion chamber holes located at directions of 12 o'clock from the center of the PMMA head phantom. The results of this study showed that the new DRFS shields could reduce dosages to 15.61%, 23.05%, and 22.71% more in 90 kVp, 120 kVp, and 140 kVp, respectively, than with a conventional bismuth shield of the same thickness, while maintaining image quality. In addition, the DRFS were produced to about 25% more thinness than conventional bismuth. We concluded, therefore, that DRFS can replace the conventional bismuth and may be utilized as a new shield.

The Current Use and Effectiveness of Bismuth Shielding in Computed Tomography: A Systematic Review

“…[17][18][19][20][21][22][23][24][25] Where as all studies report a reduction in dose to the eye, the dose savings vary from 20 to 50% depending on the scanner, technique and shield design. Mendes et al 23 conducted a study using an acrylic head phantom to evaluate the dose reduction achieved with and without the application of a bismuth shield covering the eyes.…”

“…Several studies have shown a drift in CT numbers between 50 and 65%. 25,26,28 There are also many studies that support the use of bismuth, suggesting no significant impact on image quality. 19,20,28 Where as these studies agree that streak artifacts disrupt image quality, the majority suggest that by creating a small gap between the eye lens and the shield, artifacts can be reduced to an acceptable diagnostic level.…”

Effects of bismuth breast shielding on iodine quantification in dual-energy computed tomography: an experimental phantom study

“…We were also to confirm that there was significantly less radiation exposure to the breast with a reduction rate of 14.8% in absorbed radiation dose ( P = 0.005) However, the reduction rate in our study was relatively lower than the results of previous reports with single-energy CT, which showed values in the range of 29–59% for the reduction rate in either effective or absorbed radiation dose (11–17). One study reported that the radiation dose reduction rate by the bismuth breast shield decreased at higher tube voltage settings (23). Less radiation dose reduction might be observed in DECT with breast shielding than in single-energy CT because higher tube voltage setting is inevitably used in DECT.…”

Polyurethane compositions of Bismuth used for breast shields during chest CT

“…Recently, some shields were designed and constructed that included composites of Barium sulfate (BaSO4) with filler particles of bismuth oxide (Bi2O3) in different thicknesses (0.5 to 2 mm). These shields were applied in chest CT and showed dose reduction from 13.56% to 66.64% depending on kV and shield thickness (10) . In the som articles, structure and details of the materials combiend and used in the shields are presented without further explainations about their; some only point to changing of foam thickness to reduce distortion or artifacts on the chest images (11,12) .…”