References
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3. Nandipati KC, Allamaneni S, Kakarla, et al. Extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax: experience at a community based level I trauma center. Injury. 2011;42(5):511-514.
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J Comput Assist Tomogr. 2008;32(3):386-391.
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Stuck or Not? Noninvasive Vascular Imaging in the Emergency Setting
Michael L. Loftus, MD
Dr Loftus is assistant professor of radiology at New York-Presbyterian Hospital/Weill Cornell Medical College, New York.
Conventional catheter-directed angiography has played an important role in the history of ED imaging, providing timely information about vessel integrity throughout the body and guiding potentially life-saving interventions. However, this imaging modality carries significant potential risks, including puncture-site hematoma or pseudoaneurysm, catheter-induced vasospasm, vascular occlusion or dissection, anesthesia-associated risks, and neurological deterioration or stroke.1 Moreover, emergent angiography is not universally available in all EDs.
Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) have opened new windows of opportunity for noninvasive vascular imaging to play a role in clinical decision-making in the ED. Cross-sectional angiography has virtually eliminated the need for acute catheter-directed angiography in several clinical settings, including pulmonary angiography, and the clinical applicability of CTA and MRA continues to expand as imaging techniques improve and achieve widespread acceptance and implementation. Multidetector CT is now widely available in most EDs, and the
accessibility of magnetic resonance imaging and MRA is expanding rapidly.
CTA allows evaluation of the vasculature on contrast-enhanced axial source images and also utilizes computer-generated maximum intensity projection reformations to create diagnostic images of the vascular region of interest. Similarly, MRA can be performed either with or without the administration of an intravenous gadolinium contrast agent, and provides additional information about directionality of flow, as well as detailed images of the surrounding soft tissues.
Figure 1. Computed tomography angiography curved multiplanar reformat of the left lower extremity in a patient who suffered leg trauma, multiple fractures, and probable dislocation shows intact main arterial vessels (white arrows) without evidence of pseudoaneurysm.
An emerging clinical situation in which contrast-enhanced cross-sectional imaging may supplant the need for arterial puncture and digital subtraction angiography is multiligament trauma to the knee. When significant kinetic force is applied to the knee, the joint is at risk for translocation and/or dislocation, with resultant injury to the surrounding soft-tissue envelope and potential trauma to the neurovascular structures around the knee. In this type of injury, cross-sectional imaging is routinely ordered to further evaluate and classify trauma, revealing potentially treatment-altering information concerning the integrity of the vascular structures with minimal risk to the patient (Figure 1).
The largest series of MRAs performed specifically in patients with knee dislocation reviewed 17 cases and found two cases of vascular pathology: one case of an intimal flap and one case of acute vasospasm. Digital subtraction angiography was performed on 6 of 17 cases and had 100% concordance with MRA findings.2 MRI is often performed in the setting of suspected multiligament knee injury to aid in preoperative planning, and the addition of MRA should be considered if trauma to the periarticular vasculature is suspected.
Figure 2. Volume-rendered three-dimensional computed tomography angiography of the head demonstrates the intracerebral arterial structures.
There is ample evidence that cross-sectional imaging performs well relative to conventional catheter angiography in the setting of peripheral vascular occlusion from atherosclerotic etiologies.3 Furthermore, there is precedence for utilizing contrast-enhanced CTA, as well as contrast-enhanced or three-dimensional time-of-flight MRA in other areas of the body—particularly the brain, head, and neck4 (Figure 2). Several MRA techniques are becoming available that will allow a high resolution angiographic without the use of contrast. Upcoming advances in CTA include dual-energy CT, which has the potential to allow angiography using very small amounts of contrast.