Radioprotection No 59-4 | Page 45

284 F . Poursoltani et al .: Radioprotection 2024 , 59 ( 4 ), 278 – 286

Table 3 . Comparison of dose reduction due to bismuth shielding between the current study and other relevant studies .

* Metal-oxide-semiconductor field-effect transistor . increased the CT number by 20 HU , but the noise reduced to 1.86 HU , which was attributed to the hardening of the beam . The late effect was due to the elimination of low energy rays by bismuth shield . Foley et al . ( Foley et al ., 2013 ) demonstrated that when using a Bi shield compared to standard protocols for thorax CT and down-tube flow , the average noise increased from 16.1 HU to 20.4 HU ( increase of 4.3 HU ). As a result , the use of 50 % Cu – 50 % BaSO 4 shield with a distance of 2.52 cm ( shield with a thickness of 0.52 cm and a foam pad with a width of 2 cm ) protected the breast tissue without degrading the image quality .

4.3 Patient study

By evaluation of the images of the patients in the intervention group and comparing them with the images of the patients in the control group , the effect of 50 % Cu – 50 % BaSO 4 shield on the image quality was qualitatively investigated . No artifacts were observed in the lung parenchyma , mediastinum , and breast in the manufactured radiation shields for the breast ( Tab . 2 ). This shield reduced the breast dose without affecting the image quality . Based on literature review , Tappouni et al . ( 2013 ) investigated the effect of Bi breast shield and partial CT technique in dose reduction , did not observe any artifacts on image in chest wall , heart and lung parenchyma . The results of the presented study are in agreement with the study by Tappouni et al . ( 2013 ).

The use of thorax phantom is the limitation of the present study , for which due to the fact that the thorax phantom and the breast tissue is integral , consisting of only a single piece , the surface dose was measured only on the breast surface . If an anthropomorphic phantom is available , the dose can be measured in different depths of the breast tissue in the presence and absence of shields . Another limitation of this study is the construction of radiation shields in a way that it was not possible to remove low-energy rays on the outer sides of the breast .

5 Conclusions

According to the obtained results , it can be concluded that by using 50 % Cu – 50 % BaSO 4 radiation shield for the breast , in addition to dose reduction , the image quality is good in terms of the absence of artifacts , noise and accuracy of the CT number . This shield causes the CT number shift of 0.95 HU and noise increase of 2.94 HU ( 9.3 %), therefore , it can be concluded that this radiation shield can be used for clinical application in thorax CT scanning .

Acknowledgments

The authors would like to thank Cancer Research Center , Semnan University of Medical Sciences , Iran for financial support of this study and also the radiology department of Kosar Hospital ( Semnan , Iran ) for providing the experimental measurement conditions . The authors would like to extend special thanks from Atomic Energy Organization of Iran ( AEOI ), Secondary Standard Dosimetry Laboratory ( SSDL ) for their TLD ’ s calibration and TLD ’ s reading services .

Funding

The project was financially supported by Cancer Research Center , Semnan University of Medical Sciences , Iran .

Conflicts of interest

The authors have no conflict of interest .

Data availability statement

The research data associated with this article are included within the article .

Author contribution statement

Marziyeh Behmadi and Mohammad Keshtkar contributed to the study conception and design . Experimental measurements were performed by Farideh Poursoltani , Marziyeh Behmadi , Mahdi Ghorbani and Peyman Hejazi . Data collection and analysis were performed by Farideh Poursoltani , Marziyeh Behmadi and Fatemeh Paknazar . The first draft of the manuscript was written by Farideh Poursoltani , Mohammad Keshtkar , Mahdi Ghorbani and Marziyeh Behmadi and all authors commented on previous versions of the manuscript . All authors read and approved the final manuscript .