Subtraction CT Improves Detection of Bleeding in Pelvic Fractures
Enhanced CT technique improves visualization of hemorrhage in trauma
A novel type of subtraction CT combined with dynamic contrast-enhanced CT improves diagnostic accuracy in detecting extravasation in pelvic fractures, according to new research published in Radiology. The method has the potential to speed lifesaving interventions for victims of trauma.
Imaging is crucial for clinicians trying to identify and control life-threatening hemorrhages in patients with severe traumatic injuries.
Active contrast extravasation can indicate ongoing hemorrhage requiring urgent treatment, but accurately identifying the bleeding site can be challenging. Fracture fragments, hematomas and enhancing vessels may obscure the bleeding site.
Researchers in Japan developed a new technique that subtracts the arterial-phase image from the venous-phase image to improve visualization of bleeding.
“Our method suppresses bone, soft tissue and normal arteries while selectively highlighting contrast material that newly appears or accumulates between the two phases, as occurs with ongoing contrast extravasation,” said study lead author Takaki Hirano, MD, from the Department of Radiology at Teikyo University School of Medicine in Tokyo.
For the study, Dr. Hirano and colleagues compared the diagnostic accuracy and reading times of dynamic contrast-enhanced CT with and without subtraction images for detecting extravasation in pelvic fractures. The study group included 66 patients with pelvic fractures admitted at a Level 1 trauma center over an eight-year period.
Subtraction CT increased the sensitivity for extravasation detection from 63% to 81%, with no compromise in positive predictive value. It also reduced the reading time by an average of more than eight seconds. The results suggest that subtraction CT could serve as a rapid screening aid for active bleeding. It may help readers identify subtle contrast extravasation, particularly near complex pelvic fractures.
“This could support faster communication among radiologists, emergency physicians, trauma surgeons and interventional radiologists, allowing patients to proceed more quickly to surgery or transcatheter arterial embolization when needed,” Dr. Hirano said.
Axial dynamic contrast-enhanced CT images and a subtraction image in a 68-year-old male patient with a pelvic fracture are presented: (A) plain, (B) arterial phase, (C) venous phase, and (D) subtraction image. The subtraction image enhances the visibility of the extravasation from the adjacent bone (arrow).
https://doi.org/10.1148/radiol.250119 ©RSNA 2026
From Clinical Challenge to Imaging Solution
The new method has advantages over dual-energy CT, a technique commonly used to help detect extravasation by using two different X-ray energy spectra to create iodine maps.
“Although these maps help distinguish iodine from bone and other high-attenuation materials, normal contrast-enhanced vessels remain visible, so the reader must still determine whether an iodine-containing focus represents a vessel or contrast extravasation,” Dr. Hirano said.
In developing the subtraction method, Dr. Hirano drew on his experience as an interventional radiologist at a Level 1 trauma center and his prior tenure as an emergency physician. Through this work, he observed firsthand the difficulties in recognizing contrast extravasation in patients with complex pelvic fractures.
“This clinical challenge inspired us to investigate a practical imaging tool that could make contrast extravasation easier to detect and localize,” he said. “Our goal was to help radiologists and emergency physicians identify and localize contrast extravasation more quickly and confidently, support timely treatment decisions, and ultimately improve the care of patients with severe trauma.”
The novel technique offers a compelling glimpse into how subtraction techniques, developed to improve vessel conspicuity during conventional angiography, can be leveraged across phases of enhancement to isolate active hemorrhage, according to David Dreizin, MD, from the Department of Radiology at the University of Maryland School of Medicine in Baltimore.
In a commentary accompanying the study, Dr. Dreizin noted that Dr. Hirano’s approach leverages information already present in the trauma CT exam.
“By suppressing competing visual signals, the subtraction technique makes active hemorrhage substantially more conspicuous,” Dr. Dreizin said. “The observed improvement in sensitivity without reducing precision or increasing interpretation time suggests it could become a valuable adjunct in pelvic trauma imaging.”
Because the principle of this approach is not specific to the pelvis, it also has potential for imaging trauma in other areas of the body, according to Dr. Hirano.
“It could be useful for detecting active bleeding in abdominal solid-organ injuries, mesenteric or retroperitoneal hemorrhage, and potentially other areas where subtle contrast extravasation is difficult to distinguish from surrounding structures,” Dr. Hirano said. “With improved registration and automated image processing, I believe subtraction CT could ultimately become a broader adjunct to trauma imaging.”
The method is not yet ready to replace conventional images or become a universal standard, Dr. Hirano cautioned. Larger multicenter studies and greater automation will be needed before widespread clinical adoption. Additional studies are also needed to validate the technique for specific organs and injury patterns.
An important next step is to determine whether subtraction CT is helpful for emergency physicians, trauma surgeons, and other clinicians who do not specialize in diagnostic imaging.
“Because these physicians often need to make rapid treatment decisions before a formal radiology report is available, images that make active bleeding more conspicuous could be particularly valuable,” Dr. Hirano said.
For More Information
Access the Radiology study, “Diagnostic Accuracy and Reading Times of Subtraction CT for Detecting Extravasation in Pelvic Fractures,” and the related editorial, “Signal Over Noise: A Novel Use of Subtraction CT for Pelvic Active Bleeding.”
Read previous RSNA News stories on trauma imaging: