Comparison of breast-level surface dose between single-energy CT and fast kilovoltage-switching dual-energy CT under...

This phantom study compared breast-level surface dose and image noise between single-energy CT (SECT) and fast kilovoltage-switching dual-energy CT (DECT) under matched volume CT dose index (CTDIvol) conditions. A chest phantom was scanned using a 256-row CT scanner. Surface dose was measured with real-time dosimeters placed on the bilateral anterior chest wall at the breast level and corresponding bilateral posterior positions. Tube currents of 195 mA for SECT and 250 mA for DECT provided matched console-displayed CTDIvol values. Each protocol was repeated 20 times as technical replicates. Image noise was measured in five circular regions of interest at the bilateral anterior and posterior chest walls and heart. Mean surface dose was lower with DECT than SECT at the breast level (15.86 vs. 17.02 mGy; mean difference [DECT minus SECT], -1.16 mGy; 95% confidence interval [CI], -1.71 to -0.61; P < 0.001) and posterior surface (15.77 vs. 17.26 mGy; mean difference, -1.49 mGy; 95% CI, -2.21 to -0.77; P < 0.001). Mean image noise was 7.08 HU with DECT and 6.66 HU with SECT, with no statistically significant difference (mean difference, 0.42 HU; 95% CI, -0.17 to 1.01; P = 0.160). Under the tested conditions, DECT showed lower anterior and posterior surface doses than SECT performed without CT automatic exposure control. No statistically significant difference in image noise was observed, but this does not establish equivalent image quality. These findings should not be generalized to clinically optimized SECT protocols.