RESUMEN
Objective To explore the application of adaptive statistical iterative reconstruction (ASIR)scanning technique in low dose pediatric cervical CT, especially in reducing the radiation dose for thyroid. Methods We retrospectivly analyzed 140 pediatric cervical CT. 70 cases of group A scaned with ASIR technology and preseting noise index 12 HU in Discovery CT 750 HD (GE Healthcare), and 70 cases of group B scaned with filtered back projection (FBP) technology and preseting noise index 14 HU in VCT 64 (64 Lightspeed VCT, GE Healthcare). The other scan parameters were same in 2 groups. The distribution characteristics of gender and age were completely consistent between groups. The minimum current, the maximum current, the current of thyroid on CT images and CT dose volume index (CTDIvol), scanning length and dose length product (DLP) on dose reports were all recorded for each child. The noise values of CT images were measured. 4 scores standard was used to evaluate the subjective image quality. The data were analyzed with SPSS 13, Kappa method for the test of consistency and t test for the differences of the measured data. Excel was used for mapping. Results The minimum current, the maximum current, the average current, the current for thyroid of the two groups were respectively (26.8 ± 4.2), (43.2 ± 15.4)mA;(35.8±9.6),(41.8±13.6)mA;(34.6±8.6), (41.0±13.2)mA;(36.8±12.3), (44.7±21.0)mA. The CTDIvol, DLP and the scanning length of the two groups were respectively(1.3 ± 0.3), (1.8 ± 0.6)mGy;(29.0 ± 8.3), (40.3 ± 15.6) mGy·cm and(157.5±20.2), (157.6±21.8)cm. The average current, the thyroid current, CTDI and DLP in group A were 15.8%, 17.9%, 27.3%and 28.4%lower than those in group B (t=-5.50—-0.02, P<0.01). The subjective image quality scores of the two doctors were respectively 3.4 ± 0.9, 3.3 ± 1.0, they were highly consistent (Kappa=0.834, P<0.01). The objective image noise of cancellous bone and neck muscles were respectively (32.5 ± 5.3),(32.9 ± 5.1)HU and (9.2 ± 2.3), (9.1 ± 2.0)HU, there were not statistically difference between the two groups (t=-0.47—0.24, P<0.05). Conclusion Compared with FBP, low dose pediatric cervical CT with 30%ASIR could provide dose reduction for thyroid and the whole neck while maintaining diagnostically acceptable images .