Feasiblity of Low-dose Neck Enhancement MDCT Based on Lower Neck Transverse Diameter

Objective: To explore the feasibility of low-dose neck enhancement MDCT based on the lower neck transverse diameter. Methods: One hundred and twenty-six consecutive patients with suspected of cervical disease undergoing 64-MDCT were prospectively selected and divided into 2 groups at random: conventional group and low dose group. According to the lower neck transverse diameter the low dose group were divided into 3 subgroups at large diameter (group A, diameter ≥ 40cm, n = 21) or medium diameter (group B, 35cm 〈 diameter 〈40cm, n = 35) or small diameter (group C, diameter〈35cm, n = 28). The tube voltage/tube current of conventional group was 120kV/350mA. And that of low dose were 120kV/300mA, 100kV/300mA, 80 kV/300 mA in A, B, C group, respectively. The dose-length product (DLP) and CT dose index volume (CTDIvol) of each group were recorded, and then the effective radiation dose (ED) were calculated. The image quality and radiation dose were evaluated and compared among 4 groups. Results: The radiation dose of 4 groups were respectively 1.34 mSv ±0.13 mSv, 1.17 mSv ±0.10 mSv, 0.74 mSv ±0.08 mSv, 0.34 mSv ±0.04mSv, the difference was statistically significant (F= 606.13, P < 0.01), the effective radiation dose of A, B, C group was significantly lower than that in the conventional group. There was significant difference between arbitrary two of the four groups, respective (all P < 0.01). Kappa conformance test showed that the image quality scores determined by two physicians were highly consistent with each other (all Kappa value 〉 0.70). No significant difference in image quality (Z = -0.258, P > 0.05) and contrast to noise of 4 groups (F = 0.750, P > 0.05). Conclusion: Based on patient's lower neck transverse diameter, neck enhancement MDCT with different suitable tube voltage can effectively reduce the radiation dose, while high quality image of neck structure can still be ensured.