Radiation dose to lens in different CT scanning protocols of temporal bone / 中华放射医学与防护杂志

ABSTRACT

Objective To investigate the radiation dose to the lens of patients in temporal bone CT scanning with different protocols. Methods With the same values of kV and effective mAs, the tranaxial and coronal scans of exsomatize cadaveric head was performed with conventional sequential scan mode,routine multi-slice helical scan and modified multi-slice helical scan, respectively. The values of CT volume dose index (CTDIvol) and dose length product (DLP) at various scanning mode were anylyzed, and effective doses of subject were calculated. Organ doses of the lens were measured with thermoluminescence dosimetry (TLD). Results When sequential scan mode was selected, gross effective dose was 1.21 mSv,while organ doses to lens were 50.96 and 1.73 mGy separately in axial and coronal slice scan,respectively. Effective dose was 0. 803mSv at helical scanning, while dose to lens was 40. 17 mGy. With modified helical scan mode, the effective dose was similar to routine helical scan, but dose to lens was 10.33 mGy which was significant lower than that of routine helical scan (40.17 mGy). Conclusions With the same values of kV and effective mAs, the effective doses and lens dose obtained in sequential axial and coronal scan were 1.51 times and 1.31 times higher than helical scan, respectively. With modified helical scan mode thinner slice images could be used to reformat axial, coronal and sagittal plane images, and lens dose was reduced by 74.3%. The modified helical CT scan mode of temporal bone could be selected in the clinical application.