SUBTRACTION CT improved diagnostic accuracy for extravasation in patients with pelvic fractures while also shortening radiologist reading times, according to a retrospective study at a trauma centre. The findings suggest the technique could support faster assessment of trauma patients with suspected internal bleeding.
Extravasation, seen on contrast-enhanced CT as leakage from injured blood vessels, is an important imaging marker in pelvic trauma because it may indicate active bleeding requiring urgent intervention. However, distinguishing extravasation from adjacent bone fragments on conventional CT can be difficult.
Improved Accuracy for Extravasation Detection
Researchers evaluated whether adding subtraction images to dynamic contrast-enhanced CT could improve diagnostic performance.
Subtraction CT images were created by subtracting arterial-phase images from venous-phase images, helping highlight areas of contrast leakage more clearly.
The study included 66 patients with pelvic fractures admitted between April 2015 and July 2023. The median age was 65 years, and 34 patients were male.
Three radiologists first reviewed standard datasets containing plain, arterial-phase and venous-phase CT images. One month later, they reassessed the same cases with the addition of subtraction CT images. For each review, readers recorded the presence and location of extravasation and assigned confidence scores.
Two independent radiologists established the reference standard through consensus.
Overall diagnostic accuracy improved with subtraction CT, with statistical analysis showing better detection performance than standard imaging alone. Sensitivity increased from 63% without subtraction images to 81% with subtraction CT.
Importantly, the higher sensitivity did not reduce positive predictive value, indicating that the improved detection rate was not accompanied by more false-positive findings.
Faster Interpretation in Pelvic Trauma Imaging
The addition of subtraction CT also reduced interpretation time. Mean reading time fell by 8.7 seconds when subtraction images were included.
Although the time difference may appear modest, the reduction could be meaningful in emergency radiology settings where rapid decision-making is critical, particularly in haemodynamically unstable trauma patients.
Potential Role in Emergency Radiology Workflows
The authors concluded that subtraction CT improved diagnostic accuracy for detecting extravasation and reduced reading time in patients with pelvic fractures.
For clinicians working in emergency and trauma radiology, the findings may be particularly relevant in time-sensitive cases where rapid identification of active bleeding can influence decisions around embolisation, surgery or ongoing haemodynamic management.
However, the researchers also relied on specialised statistical measures, including figure of merit values, which are less intuitive for routine clinical interpretation than metrics such as sensitivity or positive predictive value. While the improvement in overall detection performance was statistically significant, further studies may be needed to determine how consistently these gains translate into day-to-day trauma workflows and patient outcomes.
The retrospective single-centre design and relatively small cohort also limit how widely the findings can be generalised. Additional prospective research could help clarify whether subtraction CT should become a standard component of pelvic trauma imaging protocols.
Reference
Hirano T et al. Diagnostic accuracy and reading times of subtraction CT for detecting extravasation in pelvic fractures. Radiology. 2026;DOI:10.1148/radiol.250119.
Featured image: Sved Oliver on Adobe Stock
