Comparative Analysis of Radiation Dose and Image Quality Between Thyroid Shielding and Unshielding During CT Examination of the Neck

Lee, Young Hen; Park, Eun Tae; Cho, Pyong Kon; Seo, Hyung Suk; Je, Bo Kyung; Suh, Sangil; Yang, Kyung Sook

doi:10.2214/ajr.10.4955

Cited by 22 publications

(24 citation statements)

References 16 publications

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“…Generally, the bismuth shield application would lead to a beam hardening effect and starvation of information-carrying photons, resulting in an incorrect CT number being calculated during acquisition (Lee et al, 2011;Kim et al, 2013). The mean of the CT number and the SD of the CT numbers collected from the Setup A (no bismuth shield or bolus applied) can thus be used as the reference value of the CT number and image noise level in the present study.…”

Section: Discussionmentioning

confidence: 98%

Reducing the radiation dose to the eye lens region during CT brain examination: the potential beneficial effect of the combined use of bolus and a bismuth shield

et al. 2015

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-Objective:Computed Tomography (CT) is the leading contributor to medical exposure to ionizing radiation. Although the use of CT brain scans for patients with head injuries and convulsions has shown a tremendous growth, it has raised substantial concerns in the general public because of the risk of radiation-induced cataracts: the current available strategies to reduce the radiation dose to the eye lens region are limited. Therefore, the present research project was initiated with the aim of evaluating the potential benefit of the combined use of bolus and a bismuth shield on reducing the radiation dose to the eye lens region during CT brain examination. Materials and methods: We conducted a series of phantom studies to measure the entrance surface dose (ESD) that is delivered to the eye lens region during CT brain examination under the effect of different scanning and shielding setups. Results: Our results indicated, during CT brain examination: (1) a drastic reduction of 92.5% in the ESD to the eye lens region was found when the CT gantry was tilted from 0• (overall ESD = 30.7 mGy) to 30• cranially (overall ESD = 2.4 mGy), and (2) when the CT gantry was positioned at 0• (the common practice in the clinical setting), the setups with the application of a) a bismuth shield, b) a bismuth shield with a face shield (air gap), c) a bismuth shield with bolus, and d) a bismuth shield with bolus and an air gap can result in an acceptable level of image quality with a smaller overall ESD delivered to the eye lens region (overall ESD = 23.2 mGy, 24 mGy, 21 mGy and 19.9 mGy, respectively) than the setup without the bismuth shield applied (overall ESD = 30.7 mGy). Conclusion: When the primary beam scanning through the eye lens region is unavoidable during CT brain examination, the combined use of a bismuth shield with bolus and a face shield is an easyto-use and inexpensive shielding setup to reduce the radiation dose delivered to the eye lens region while maintaining the correct CT number and a low degree of image noise in the resultant image.

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Section: Discussionmentioning

confidence: 98%

Reducing the radiation dose to the eye lens region during CT brain examination: the potential beneficial effect of the combined use of bolus and a bismuth shield

et al. 2015

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“…Some investigators have argued that when noise and image quality were analysed objectively and in a robust manner, studies appear to suggest that there is increase in image noise and deterioration of image quality (Geleijns et al, 2006, Vollmarr et al, 2008, Karla et al, 2009. Although, it must be noted that a more recent study by Lee et al (2011) looking at bismuth thyroid shield did not show significant differences in mean noise values. In general, there needs to be more evidence that robustly assess image quality prior to the routine use of shielding to be universally accepted.…”

Section: Displacement and Shielding Methodsmentioning

confidence: 70%

“…This was the case for both Geleijns et al (2006) and Vollmar et al (2008). When a spacer or plastic shields are used the streak artefacts are noticeably eliminated (Hohl et al 2006, Karla et al, 2009and Lee et al, 2011. However, the increase in attenuation appears to be a real issue (Karla et al, 2009, Lee et al, 2011).…”

Section: Displacement and Shielding Methodsmentioning

confidence: 99%

“…Their findings were supported by Kalra et al (2009) indicating that as well as increasing noise, there is artifactually increased in attenuation values in the region immediately behind the shields. More recently, Lee et al (2011) showed that the use of thyroid shielding with cotton wool spacer reduces the dose to thyroid by up to 27% without affecting image noise although it was noted that there was noticeably increase in the attenuation values of the superficial neck structures such as the neck muscles. It was thought that this was likely related to a metal artefact caused by bismuth implanted within the shield itself.…”

Section: Displacement and Shielding Methodsmentioning

confidence: 99%

“…When a spacer or plastic shields are used the streak artefacts are noticeably eliminated (Hohl et al 2006, Karla et al, 2009and Lee et al, 2011. However, the increase in attenuation appears to be a real issue (Karla et al, 2009, Lee et al, 2011). This could have implications when looking at coronary artery calcifications, renal cyst and adrenal mass characterisation, for example, where increase in attenuation is used specifically to characterise disease entities.…”

Section: Displacement and Shielding Methodsmentioning

confidence: 99%

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