Application of automatic tube current modulation technology in PET/CT

Abstract

Objective To investigate the effects of automatic tube current modulation(ATCM) on CT image quality and effective dose(ED) of PET/CT of 90 patients. Methods PET/CT of 90 patients from October 2017 to July 2018 were randomly divided into three groups, A, B, and C by systematic sampling(30 cases in each group), and CT was scanned by ATCM. The tube current interval of group A and B was 60–240 mA, and the noise index(NI) was 10 and 15; the tube current interval of group C was 60 –180 mA, and the NI was 15. The CT volume dose index(CTDIvol) and dose length product(DLP) were recorded, and the ED was estimated according to the formula. The CT image quality of neck, chest, abdomen, and pelvis were evaluated blindly by two and above attending physicians in nuclear medicine to calculate signal-to-noise ratio(SNR) by measuring CT value and noise value of the CT image. Noise value and SNR were compared with variance analysis. CTDIvol,DLP, and ED were compared with Kruskal-Wallis and with Nemenyi in pairs. Results Differences in noise value[(11.90±2.83)–(26.03±3.74)] and SNR [(2.03±0.34)–(4.35±0.71)] among three groups were statistically significant (F=38.01–64.20, F=32.09–81.62, and all P<0.05), and the CT image quality met the clinical diagnostic requirements. CTDIvol were (12.44±0.53), (9.39±2.01), and (7.05±1.03) mGy, DLP were (998.45±96.04), (741.60±168.87), and (571.29±97.41) mGy·cm, and ED were (14.98±1.44), (11.12±2.53), and (8.57±1.46) mSv among three groups, with statistically significant differences(χ2=62.18, 57.19, 57.16, and all P<0.05). Group C was lower than group A(χ2=56.55, P<0.05) with statistically significant differences. Conclusion ATCM technology can ensure the image quality while reducing the ED effectively by modulating the current interval and NI reasonably. Key words: Positron emission tomography computed tomography; Radiation dosage; Automatic tube current modulation; Image quality