Pediatric chest CT at 70 kVp: a feasibility study in 129 children.

BACKGROUND

Before introducing 70-kVp settings in the low-kilovoltage strategies for pediatric examinations, it was mandatory to demonstrate, at similar dose levels, an equivalence of image quality at 70 kVp and 80 kVp.

OBJECTIVE

To assess image quality of chest CT examinations acquired at 70 kVp in comparison with standard scanning at 80 kVp.

MATERIALS AND METHODS

We prospectively evaluated 129 children with a 70-kVp scanning protocol (group 1). All scanning parameters were kept similar to those usually selected for pediatric standard 80-kVp protocols, except the milliamperage increased by a factor of 1.6 to maintain comparable radiation dose. Image quality of group 1 examinations was compared to that of a paired population scanned at 80 kVp (group 2). The noninferiority hypothesis was fixed at 10% of the mean level of image noise.

RESULTS

There was no significant difference in the mean dose length product (DLP) and the volume computed tomography dose index (CTDIvol) between the groups (DLP: 20.5 ± 5.8 mGy.cm [group 1] vs. 19.7 ± 7.6 mGy.cm [group 2]; P = 0.06) (CTDIvol: 0.8 ± 0.1 mGy [group 1] vs. 0.8 ± 0.18 mGy [group 2]; P = 0.94). The mean of differences in image noise between group 1 and group 2 examinations was -1.38 (-2.59; -0.18), verifying the noninferiority hypothesis. Subjective image quality did not significantly differ between group 1 and group 2 examinations (P = 0.18).

CONCLUSION

At equivalent radiation dose levels, 70-kVp protocols provide similar image quality to that achievable at 80 kVp.