Should radiologists care about kV? Phantom and clinical study of effects of kV on hemoperitoneum HU in the setting of splenic injuries

Purpose: Evaluate the potential effects of X-ray tube voltage (kV) changes on Hounsfield unit (HU) measurements of hemoperitoneum in patients with blunt splenic injuries. Methods: Eight different tissue equivalent electron density plugs in the Electron Density Phantom were scanned (muscle, adipose, breast, liver, lung (exhale), lung (inhale), trabecular bone, and dense bone). The phantom was scanned at different kV values (70, 80, 100, 120, and 140 kV). In the clinical study, the local trauma registry database was queried for splenic injuries between January 2015 and December 2016 with a final cohort of 110 patients. The average HU numbers of hemoperitoneum found in three different anatomic locations (pelvic, perisplenic, and perihepatic) were compared at different kV values (100 kV, 120 kV, and 140 kV). ANOVA and pairwise t tests were performed for statistical analysis. Results: In both studies, HU measurements generally decreased as kV increased, and vice versa. One hundred ten patients were reviewed: 29 for 100 kV, 66 for 120 kV, and 15 for 140 kV. For the perihepatic group, significant differences were observed in average HU in the following pairwise comparisons: 100/140 (13.7 (5.3), p < 0.05) and 120/140 (10.3 (4.5), p < 0.05). For the perisplenic group, significant differences were observed in 100/120 (7.0 (3.5), p < 0.05) and 100/140 (13.2 (4.9), p < 0.05). No significant difference was observed in the pelvic location (p = 0.5594). Conclusions: HU measurements of hemoperitoneum in patients with blunt splenic injuries significantly varied with the use of different kV values. Radiologists should be aware of the possible effects of altering kV on HU.