15.3 CT Trauma Protocols & Surgical Planning

Why Trauma and Surgical Planning Close Out Procedures

The ARRT "Additional Procedures" focus theme's final element — trauma and surgical planning — is the highest-acuity, most time-pressured content on the CT exam. A polytrauma patient may go from the ambulance bay to the CT gantry in minutes, and the protocol choices made there directly shape whether a surgeon or interventional radiologist can act in time. This section closes out the Procedures domain by tying together acquisition strategy (how to scan fast without sacrificing diagnostic quality) with the downstream use of that same volumetric data for pre-operative planning.

The Whole-Body Trauma "Pan-Scan"

A whole-body trauma CT, often called a pan-scan, is built to mirror the ATLS (Advanced Trauma Life Support) primary survey — rapidly ruling in or out life-threatening injury across every major body region in one visit rather than sequential, region-by-region imaging.

Split-Bolus Single-Pass: Dose Reduction Without Losing Phases

A conventional trauma protocol acquires two separate contrast phases — an arterial-phase pass (bolus-tracked, triggered around 100 HU in the descending aorta) followed by a separate venous-phase pass roughly 50-70 seconds later — which doubles the radiation dose for the torso. The split-bolus single-pass technique instead delivers two sequentially timed injections (for example, a slower initial injection to build portal-venous/solid-organ enhancement, followed roughly 10 seconds later by a faster bolus to build arterial enhancement) and acquires only one CT pass timed so both vascular and parenchymal enhancement are present simultaneously. Published comparisons show split-bolus single-pass protocols can nearly halve trauma CT radiation dose relative to the conventional two-phase approach while still providing both arterial and venous information — a major reason it has become the default at many trauma centers.

Delayed-Phase Imaging: Catching Active Bleeding

When the initial (arterial/portal-venous) images of the liver, spleen, or kidney show a hypodense, wedge-shaped or irregular area consistent with a laceration or contusion, the technologist should anticipate that the radiologist may need a delayed-phase acquisition — obtained roughly 70-90 seconds after injection, or as a dedicated 3-5 minute delayed series — specifically to distinguish:

• Active extravasation: An irregular, ill-defined contrast collection that increases in size and density between the arterial/portal-venous phase and the delayed phase, because contrast continues to leak from a torn vessel over time. This is a critical, time-sensitive finding that typically triggers immediate interventional radiology embolization or surgery.
• Pseudoaneurysm: A focal, well-circumscribed contrast collection that matches blood-pool attenuation on both phases without growing — it fills and stays roughly the same size because it is a contained outpouching of the vessel wall rather than active leakage.

Missing the delayed phase on a case with a visible laceration is one of the costliest protocol errors in trauma imaging, because active extravasation can be invisible or ambiguous on the initial pass alone.

From Trauma Data to Surgical Planning

The same thin-slice, isotropic CT datasets used for trauma diagnosis are routinely repurposed — or acquired electively — for surgical planning:

• Orthopedic fracture planning: 3D volume-rendered and MPR reconstructions let surgeons pre-plan reduction and hardware placement for complex intra-articular fractures (for example, acetabular or tibial plateau fractures) before entering the operating room.
• Vascular mapping for reconstructive surgery: CTA of donor and recipient vessels (for example, before a free-flap reconstruction) confirms vessel caliber, patency, and anatomic variants so the surgical team knows which vessels are usable before the incision.
• Craniomaxillofacial virtual surgical planning (VSP): High-resolution facial/mandibular CT data feeds software used to design 3D-printed surgical guides and models, letting surgeons rehearse osteotomies and hardware placement for complex facial reconstruction or orthognathic surgery.
• Stereotactic and neurosurgical planning: Thin-slice head CT (sometimes fused with MRI) supports frame-based or frameless stereotactic targeting for biopsy or lesion ablation.

Grading Solid-Organ Injury

Radiologists commonly communicate splenic, hepatic, and renal injuries using the American Association for the Surgery of Trauma (AAST) organ injury scale, which grades severity from I (a small subcapsular hematoma or superficial laceration under 1 cm) through V (shattered organ or devascularizing hilar injury). A CT technologist does not assign the grade, but recognizing that higher-grade lacerations are exactly the injuries most likely to need a delayed phase — because deeper, more extensive lacerations disrupt larger vessels and are more likely to actively bleed — helps you anticipate when the radiologist will ask for additional delayed images before the patient leaves the scanner.

Common Traps

• Reading only the initial acquisition on a case with a visible solid-organ laceration and never obtaining the delayed phase needed to detect active extravasation.
• Confusing a stable pseudoaneurysm with active extravasation (or vice versa) — the distinguishing feature is behavior between phases, not appearance on one image.
• Relying on axial cervical-spine images alone; many trauma fractures are identified only on the sagittal/coronal reformats.
• Treating split-bolus single-pass as a lower-quality shortcut rather than recognizing it as a deliberate, evidence-based dose-reduction technique that preserves both vascular and parenchymal information.