Effect of 70-kVp chest CT on surface dose at the mammary gland level in a neonatal phantom under matched CTDIvol conditions.

To compare surface dose at the mammary gland level between 70- and 120-kVp non-contrast neonatal chest computed tomography (CT) under matched volume CT dose index (CTDIvol) conditions, a neonatal anthropomorphic phantom was scanned using a 256-row CT scanner. Real-time dosimeters were placed bilaterally on the anterior chest wall at the mammary gland level and on the posterior chest wall at the same axial level. For the 70-kVp protocol, the noise index was adjusted to match the console-displayed CTDIvol of the 120-kVp protocol. Each protocol was repeated 15 times, and image noise was measured on axial images. Anterior surface dose was significantly higher with 70 kVp than with 120 kVp (median [IQR], 5.67 [5.17-5.86] vs. 5.29 [4.84-5.43] mGy; p < 0.01). Posterior surface dose and image noise did not differ significantly. Under matched CTDIvol conditions, 70-kVp neonatal chest CT increased anterior mammary surface dose relative to 120-kVp CT in this phantom.