Photon-counting CT angiography in a multi-trauma patient with bilateral pulmonary embolism: combined vascular mapping and quantitative iodine-density assessment prior to scalp reconstruction: case report.

Background: Photon-counting detector CT (PCCT) combines high-resolution anatomical and spectral imaging by directly counting individual x-ray photons and discriminating their energies. Its role in surgical planning in complex multi-trauma with concurrent pulmonary embolism remains undefined. Case Presentation: A 58-year-old previously healthy woman was entrapped by a cement mixer, sustaining traumatic scalp avulsion (20 × 20 cm) with exposed skull, depressed right parietal fractures, subdural and epidural hematoma, right 3rd-9th rib fractures, mid-shaft radius and ulna fractures with tendon and radial-nerve injury, and a left maxillary frontal-process fracture. After emergent craniotomy, debridement, open reduction and internal fixation of the forearm, and prolonged immobilization, bilateral soleal vein thrombosis and bilateral segmental pulmonary embolism developed. Before scalp reconstruction, PCCT angiography (NAEOTOM Alpha, Siemens) was performed with cinematic rendering and iodine-density mapping. Mean pulmonary iodine density was 1.82 mg/mL on the right versus 0.74 mg/mL on the left (right-to-left ratio 2.46:1), suggesting relatively preserved iodine distribution on the right and reduced iodine distribution on the left despite bilateral emboli on CTPA. A pedicled fasciocutaneous flap from the right anterolateral thigh was performed under tiered enoxaparin anticoagulation with anti-activated factor X (anti-Xa)-guided dose escalation. The flap survived completely, the donor site healed, and the patient was discharged on day 14 with stable wound coverage. At three-month follow-up she had no recurrent thromboembolism and recovered near-normal right upper-extremity function. Conclusion: PCCT angiography provided an arterial map for reconstructive planning and quantitative iodine maps in a single acquisition, supplementing CTPA with a quantitative surrogate of pulmonary blood-volume distribution. The novelty of this case is the integrated use of a single PCCT examination for vascular mapping and spectral pulmonary iodine assessment in a complex multi-trauma setting, not the demonstration of PCCT superiority over dual-energy CT. Whether this integrated approach changes outcomes compared with dual-energy CT protocols requires prospective comparison.