Integration of delayed phase into whole body CT trauma imaging : utility and potential role as a selective acquisition

PURPOSE To retrospectively evaluate the utility of delayed computed (CT) tomography of the abdomen and pelvis and its potential role as a selective acquisition integrated into Whole-Body CT imaging. METHOD AND MATERIALS A total of 562 patients (397 men, 165 women; mean age 40.2 years, 18-91 years) who were evaluated as a part of Whole-Body CT (WBCT) acquisition protocol for trauma, were identified during a 2-year period. Delayed CT of the abdomen and pelvis scans were acquired 5 minutes after intravenous contrast material was injected, with a decreased tube current of 100mAs or with automatic modulation of the radiation dose (Dose Care). Criteria for the inclusion in the study included the presence of (a) solid organ injury; (b) bowel or mesenteric injury, (c) free fluid only; (d) active contrast material extravasation only; (e) pelvic fracture without solid organ, bowel or mesenteric injury. Injury was identified in 96 patients. Two radiologists blinded as to the initial CT scan interpretation reviewed these cases to determine the utility of delayed scans. Disagreement was settled by consensus. Delayed scans were considered useful when they aided in (a) characterizing initial CT findings, (b) identifying findings not present at initial CT, and (c)increasing reader confidence with regard to initial CT findings. We used the normal approximation of the binomial distribution to obtain the confidence interval for the overall utility of delayed scans. RESULTS Delayed scans were useful in 22 % (9 of 40) of patients with solid organ injury, 15% (2 of 13) of patients with bowel or mesentery injury, 13% (3 of 22) of patients with pelvic fractures, and in 14% (2of 14) of the patients with free fluid only. Overall, delayed CT was useful in 2.8% (16 of 562) of all patients (95% confidence interval 1.2-3.5) referred for evaluation following trauma as a part of WBCT acquisition protocol. Utility increased to 16.6 % (16 of 96) (95% confidence interval: 7.5-19) in the group of patients with injury or suspected of having injury after initial CT. CONCLUSION Although the integration of delayed phase into Whole-Body CT trauma imaging allows no additional "road trips", selective rather than routine acquisition is recommended CLINICAL RELEVANCE/APPLICATION Delayed CT scan should be acquired in patients with injury or suspected injury after initial CT, particularly when free abdominal fluid is detected.