Radioprotection No 59-4 | Seite 44

F . Poursoltani et al .: Radioprotection 2024 , 59 ( 4 ), 278 – 286 283 Fig . 4 . An example of axial thoracic CT images obtained with 50 % Cu-50 % BaSO 4 shield for shielding of Lung mediastinum ( a ), for parenchyma ( b ).

Table 2 . Data on artifact occurrence in patients with and without 50 % BaSO 4 -50 % Cu shield ( no artifact , artifact in the lung area , artifact in the mediastinum area , artifact in the breast area ).

Number of patients

constructed bismuth breast shields in this study in reducing the ESD is close to the results of Hopper et al . ( 2002 ), Mehnati et al . ( 2018 ), Yilmaz et al . ( 2007 ), Catuzzo et al . ( 2010 ), Huggett et al . ( 2013 ), Mendes et al . ( 2015 ), Vollmar et al . ( 2008 ). These small differences in the results of these studies may be due to differences in imaging techniques , breast sizes and dose measurement tools . The efficacy of the constructed shields in this study suggests that they can be used as dose reduction shields for clinical applications in CT examinations .

Tochaikul et al . ( 2024 ) conducted a study to investigate a lead-free radiation shielding material , BaSO 4 composite , and evaluated its effectiveness in providing radiation protection . The findings show that the composite containing 30 % BaSO 4 shows the most effective radiation absorption properties with percentages of 92.15 %, 89.26 %, and 86.04 % in X-ray energies of 40 , 60 , and 80 kVp , respectively . In addition , composites containing BaSO 4 are environmentally friendly and provide good protection against low-dose radiation . Moonkum et al . ( 2023 ) performed a study with the aim of investigating a nonlead radiation shield and evaluating its effectiveness in radiation protection . In that study , they studied the characteristics of primary and secondary radiation absorption of shields consisting of silicone rubber , BaSO 4 and Bi 2 O 3 in different ratios . The results showed that the protective material with 70 % BaSO 4 and Bi 2 O 3 has the ability to reduce the radiation dose from 120 kVp X-ray and has absorption properties of 90.19 %– 94.87 % for primary radiation and 92.72 %– 97.48 % for secondary radiation . In addition , silicone rubber shielding materials mixed with BaSO 4 and Bi 2 O 3 are environmentally friendly , flexible , and have excellent shielding performance in reducing diagnostic X-ray exposure . However , in the present study , the dose reduction of 100 % BaSO 4 shield was only 17.14 %, which was not statistically significant , and this shield was ultimately rejected in this study .

4.2 Effect on noise and CT number shift on the CTDI phantom

The shields were constructed in a rectangular cubic form with different weight percentages of BaSO 4 andCutofind which composition has the least effect on image quality . The shield construction was completely flexible but due to the 2 cm foam which was attached to the shield , the shape of shield seems inflexible ( Fig . 2a ). 90 % Cu – 10 % BaSO 4 , 50 % Cu – 50 % BaSO 4 , 100 % BaSO 4 , 100 % Bi shields increased image noise by 4.5 %, 9.3 %, 8.13 %, and 16.5 %, respectively and the corresponding CT number shift was 2.43 %, 0.77 %, 1.10 % and 4.00 %, respectively . According to the discussed cases , it can be mentioned that scan images with 50 % Cu – 50 % BaSO 4 shield , had less noise and CT number shift . The increase in image noise and CT number shift were 2.94 HU and 0.95 HU , respectively , for without and with 50 % Cu – 50 % BaSO 4 shield . 50 % Cu – 50 % BaSO 4 shield compared to the other compositions , had the lowest degrading effects on the image quality , therefore , this shield was used as the radiation shield material in the patient study for further evaluation . The amount of noise increase and CT number shift in the posterior region was less than the anterior region , and the reason for this is that the posterior region is far from the radiation shield .

In accordance with the literature review , Einstein et al . ( 2012 ) demonstrated that the use of commercial Bi shielding of breast during CT coronary angiography increased the noise in the location of the coronary arteries by 2.3 HU . Tappouni et al . ( 2013 ) indicated that the use of commercial Bi radiation shield