CT Topogram as a Screening Tool for Shrapnel Detection Following Blast Injury

Background: Whole-body computed tomography (WBCT) is widely used for the initial assessment of blast injuries but entails substantial radiation exposure and resource utilization. We evaluated whether the CT topogram could identify patients at low risk for clinically significant shrapnel and potentially support selective WBCT.

Methods: This retrospective single-center study included hemodynamically stable patients presenting after blast injury or explosion exposure between 2022 and 2024 who underwent WBCT. Patients were categorized according to the presence or absence of shrapnel on the topogram. WBCT examinations were reviewed for shrapnel presence, location, number, and clinical significance. Clinical and imaging characteristics were compared, and topogram diagnostic performance was calculated.

Results: Seventy-six patients were included: 39 had a negative and 37 a positive topogram. Clinical parameters did not differ significantly between groups. Shrapnel was detected on WBCT in 46.2% of patients with a negative topogram versus 100% with a positive topogram (p<0.001). Shrapnel detection differed significantly in the chest (0% vs 37.8%, p<0.001), abdomen/pelvis (10.3% vs 37.8%, p=0.011), and extremities (15.8% vs 59.5%, p<0.001). Topogram sensitivity and specificity for detecting shrapnel were 67.3% and 100%, respectively, with a positive predictive value of 100% and negative predictive value (NPV) of 53.8%. For clinically significant deep shrapnel or shrapnel requiring treatment, NPV increased to 79.5%.

Conclusions: A negative topogram alone cannot safely exclude retained shrapnel and does not currently justify omission of WBCT. However, its improved performance for clinically significant shrapnel supports further investigation of selective imaging algorithms combining topographic and clinical criteria to reduce unnecessary radiation exposure.