DOI: 10.1148/rg.283075050
RadioGraphics 2008;28:653-665
© RSNA, 2008
Multidetector CT and Three-dimensional CT Angiography for Suspected Vascular Trauma of the Extremities1
Elliot K. Fishman, MD,
Karen M. Horton, MD, and
Pamela T. Johnson, MD
1 From the Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N Caroline St, Room 3251, Baltimore, MD 21287. Presented as an education exhibit at the 2006 RSNA Annual Meeting. Received March 19, 2007; revision requested July 2 and received August 31; accepted September 12. E.K.F. receives research support from and is on the advisory boards of Siemens and GE Healthcare and is a cofounder of HipGraphics; both remaining authors have no financial relationships to disclose.
Address correspondence to E.K.F. (e-mail: efishman{at}jhmi.edu).
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Abstract
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The evolution of computed tomography (CT) from four to 16 to 64 sections since its inception in the late 1970s has led to more widespread use of this imaging modality in the emergent setting. CT angiography has become a crucial diagnostic technique for identifying vascular injury in the trauma patient. Regardless of the nature of the traumatic injury (eg, stab wound, gunshot wound, injury from a motor vehicle accident), use of multidetector CT with two-dimensional (2D) reformation and three-dimensional (3D) rendering allows visualization of injury to bone, muscle, and vasculature. The radiologist should be familiar with the indications for CT angiography, optimization of current multidetector CT acquisition protocols, utility of 2D and 3D displays, and CT findings in the presence of vascular injury to ensure prompt diagnosis and treatment.
© RSNA, 2008
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Introduction
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One of the classic applications of computed tomography (CT) since it was introduced in the late 1970s has been the evaluation of trauma patients. Initial articles focused on the noninvasive nature of CT and how it could replace more invasive procedures like peritoneal lavage or surgical exploration. In addition to this advantage, CT allowed new concepts in trauma imaging, resulting in a change in philosophy that has led to more conservative case management. Whether the topic is hepatic trauma, splenic trauma, or renal trauma, CT has been instrumental in the devising of innovative grading scales that facilitate a more uniform management plan in these patients. The role of CT in trauma to the brain and spine, as well as to the musculoskeletal system in general, has inaugurated an era in which nearly every emergency department has at least one CT scanner available at all times.
As CT has evolved from one section being obtained every 10–60 seconds to an entire examination being performed in less than 10 seconds, we have seen the role of CT in the trauma center expand. The introduction of ever-faster scanners, no longer restricted by scanning distance or limited tube-heating capacities, has led to more widespread use of CT in the emergent setting. Certain applications such as cervical spine trauma have become "CT only" studies, thereby obviating conventional radiography followed by CT. The introduction of 16- and now 64-section CT scanners into the emergency department has expanded the potential applications to include cardiac CT (coronary CT angiography) and a wider range of CT angiographic applications.
A PubMed review of the published literature on CT angiography in the setting of trauma from 2000 to the present identifies more than 400 articles, most of which discuss imaging of the neck and cervical region or the brain. Only a limited number of articles address CT angiography following trauma to the extremities and, for the most part, describe preliminary experience. Accordingly, we decided to describe our experience with CT angiography of the extremities in the emergency department over the past year, following installation of our 64-section CT scanner. 
For many applications of CT angiography, 16-section CT will be adequate; however, 64-section CT provides significant advantages. These include improved spatial (<0.4 mm) and temporal (150–180 msec) resolution (1) and increased speed of data reconstruction (up to 40 sections per second), coupled with current postprocessing capabilities, which are critical in these patients.
In this article, we discuss the current role of multidetector CT with two-dimensional (2D) reformation and three-dimensional (3D) rendering in the evaluation of extremity vascular injury following trauma, in terms of 64-section CT protocol design, data analysis, potential pitfalls, and imaging findings, in conjunction with pertinent information from published studies.
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Scanning Protocol Design
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The 64-section CT scanner (Somatom Sensation 64; Siemens Medical Solutions, Malvern, Pa) in our emergency department is operational 24 hours a day, 7 days a week. All patients referred for emergency CT are selected by their referring doctors (emergency department attending physicians or surgical consultants) on the basis of clinical history, mode of injury, or physical examination findings. We try to minimize radiation exposure by scanning only those patients whose clinical history and findings warrant CT angiography and limiting the anatomic coverage to the region of interest. Scanning parameters include a detector thickness of 0.6 mm, a section thickness of 0.75 mm, a reconstruction interval of 0.5 mm, and, typically, 120 kVp and 120–200 mAs.
Unless it is contraindicated, studies are performed with intravenously administered contrast material, either Omnipaque 350 or Visipaque 320 (GE Healthcare, Princeton, NJ), depending on the patient’s renal status or clinical history. Between 100 and 120 mL of contrast material is injected at a rate of 4 mL/sec. Proper timing is critical to ensure that the arterial system is maximally enhanced. We time the delivery of contrast material with standard timing delays for optimal middle to late arterial phase imaging. A 25–30-second delay is typically used, depending on the anatomic region being imaged. For example, in cases of stab wounds to the neck, the delay will be shorter, whereas in cases of lower extremity injury a longer delay of around 40–45 seconds may be necessary. Bolus tracking or even a test bolus could be used as a satisfactory alternative, although in the trauma setting, time is often critical and a preset delay may be most expedient. Furthermore, as shown in the literature, these patients are usually young adults (2–7), in whom a fixed delay should be adequate. In fact, Soto et al (5,6) elected to use fixed scanning delays specific to each anatomic region in both of their prospective studies, after it was determined that timing delays varied only slightly among patients in whom a test bolus technique was used (6). In cases of suspected venous injury, dual phase scanning is ideally performed with the venous phase 25–35 seconds after the arterial phase (Fig 1). In selected cases, a single-phase acquisition can be performed with a 60–80-second delay, depending on the specific case. A single delayed acquisition is performed when there is concern for venous injury on the basis of clinical assessment.
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Figure 1. Suspected vascular injury in a 46-year-old woman with trauma to the right shoulder and suggestive symptoms. Delayed coronal color-coded VR image from multidetector CT data obtained 60 seconds after contrast material injection depicts the axillary artery and veins without any injury. Delayed scanning or dual phase acquisition is critical for venous enhancement.
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All images are reconstructed with a soft-tissue kernel to evaluate the soft tissues and vasculature; a high-resolution bone kernel is used in selected cases of suspected skeletal injury. Once the data sets were reconstructed, all images were sent to a workstation (Leonardo running InSpace [Siemens Medical Solutions]) for interactive 3D rendering by the radiologist.
In addition to careful review of axial sections, multiplanar review with 2D multiplanar reformation (MPR) and 3D rendering of these data sets is essential. Studies have compared axial sections, cross-sectional multiplanar reconstructed images, MPR images, and 3D volume-rendered (VR) images obtained in patients with suspected extremity arterial disease (2,8). Trauma patients were evaluated by Rieger et al (2), who compared interactive 2D (MPR) and 3D (VR) images. Results showed that MPR images were advantageous in a number of patients with arterial dissection; however, VR images were significantly more useful for facilitating the diagnosis overall, since they allowed a more comprehensive evaluation. Nonetheless, review of any 2D or 3D reformatted images in conjunction with the axial source images is essential in trauma patients, as Rieger et al (2) confirmed by showing that axial sections had significantly greater reliability compared with MPR and VR images. In a study of lower extremity arterial occlusive disease, Ota et al (8) created cross-sectional multiplanar reconstructed images tangential to a line drawn centrally on the vessel. These images were compared with axial sections (supplemented with both VR and maximum-intensity-projection [MIP] images for interpretation) in the evaluation of the iliac arteries. Results revealed a significantly higher rate of correct interpretation with the combined cross-sectional multiplanar reconstruction and 3D display technique, as well as higher 
values for interobserver agreement (8).
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Data Analysis: A Practical Approach
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Evaluation of the acquired data set is performed interactively with a combination of axial CT, MPR, and 3D postprocessing with VR or MIP techniques (Figs 2–4). At our institution, all data sets are evaluated by a radiologist, who is also responsible for performing the data postprocessing. An advantage of 3D mapping with VR is the ability to display the information in a format that not only simulates a classic catheter angiogram (digital subtraction), but also takes advantage of the unique capability of VR to display tissue in addition to the vasculature, including muscle, soft tissues, and bone (Figs 3–6) (9). The requirement for a rapid diagnosis favors the use of VR, since a detailed vascular map can be generated without having to segment the original data set (Figs 5–7) (9). MIP imaging typically requires segmentation with bone removal, especially when anatomic regions like the shoulder and axilla, pelvis, or extremities are involved (Fig 8).
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Figure 2a. Groin puncture wound in a 57-year-old man. (a, b) CT scan (a) and MPR image (b) show an intramuscular hematoma (white arrowheads in a, arrows in b) with an enhancing pseudoaneurysm (black arrowheads) anterolateral to the femoral artery. (c) MIP image shows the 3.6-cm pseudoaneurysm (arrows), which arises from a branch of the right superficial femoral artery (SFA).
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Figure 2b. Groin puncture wound in a 57-year-old man. (a, b) CT scan (a) and MPR image (b) show an intramuscular hematoma (white arrowheads in a, arrows in b) with an enhancing pseudoaneurysm (black arrowheads) anterolateral to the femoral artery. (c) MIP image shows the 3.6-cm pseudoaneurysm (arrows), which arises from a branch of the right superficial femoral artery (SFA).
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Figure 2c. Groin puncture wound in a 57-year-old man. (a, b) CT scan (a) and MPR image (b) show an intramuscular hematoma (white arrowheads in a, arrows in b) with an enhancing pseudoaneurysm (black arrowheads) anterolateral to the femoral artery. (c) MIP image shows the 3.6-cm pseudoaneurysm (arrows), which arises from a branch of the right superficial femoral artery (SFA).
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Figure 3a. Femoral fracture from a motorcycle accident in a 15-year-old boy. The patient had undergone open reduction internal fixation 1 month earlier and presented with severe, acute thigh pain. (a, b) Axial CT (a) and coronal MPR (b) images depict the femoral fracture (arrowheads in b), an intramedullary rod, and contrast material within a large pseudoaneurysm (arrows in a) posterior to the femur. (c) Sagittal VR image shows a large, bilobed pseudoaneurysm (white arrows) and active contrast material extravasation (black arrow) near the distal SFA and fracture. The patient underwent an emergency femoral-popliteal bypass procedure performed with a reverse saphenous vein graft.
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Figure 3b. Femoral fracture from a motorcycle accident in a 15-year-old boy. The patient had undergone open reduction internal fixation 1 month earlier and presented with severe, acute thigh pain. (a, b) Axial CT (a) and coronal MPR (b) images depict the femoral fracture (arrowheads in b), an intramedullary rod, and contrast material within a large pseudoaneurysm (arrows in a) posterior to the femur. (c) Sagittal VR image shows a large, bilobed pseudoaneurysm (white arrows) and active contrast material extravasation (black arrow) near the distal SFA and fracture. The patient underwent an emergency femoral-popliteal bypass procedure performed with a reverse saphenous vein graft.
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Figure 3c. Femoral fracture from a motorcycle accident in a 15-year-old boy. The patient had undergone open reduction internal fixation 1 month earlier and presented with severe, acute thigh pain. (a, b) Axial CT (a) and coronal MPR (b) images depict the femoral fracture (arrowheads in b), an intramedullary rod, and contrast material within a large pseudoaneurysm (arrows in a) posterior to the femur. (c) Sagittal VR image shows a large, bilobed pseudoaneurysm (white arrows) and active contrast material extravasation (black arrow) near the distal SFA and fracture. The patient underwent an emergency femoral-popliteal bypass procedure performed with a reverse saphenous vein graft.
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Figure 4a. Gunshot wound to the inner thigh in a 30-year-old man. (a–c) Axial contrast-enhanced multidetector CT scan (a), coronal MPR image (b), and sagittal oblique color-coded VR image (c) demonstrate muscular injury with hematoma (arrows in a and b) and an entry wound (arrow in c) in the medial left thigh. Extravasated contrast material (arrowheads in a and b) is also seen. (d) Coronal thin-slab VR image from CT angiographic data reveals an area of active extravasation (arrows) from a small branch of the SFA.
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Figure 4b. Gunshot wound to the inner thigh in a 30-year-old man. (a–c) Axial contrast-enhanced multidetector CT scan (a), coronal MPR image (b), and sagittal oblique color-coded VR image (c) demonstrate muscular injury with hematoma (arrows in a and b) and an entry wound (arrow in c) in the medial left thigh. Extravasated contrast material (arrowheads in a and b) is also seen. (d) Coronal thin-slab VR image from CT angiographic data reveals an area of active extravasation (arrows) from a small branch of the SFA.
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Figure 4c. Gunshot wound to the inner thigh in a 30-year-old man. (a–c) Axial contrast-enhanced multidetector CT scan (a), coronal MPR image (b), and sagittal oblique color-coded VR image (c) demonstrate muscular injury with hematoma (arrows in a and b) and an entry wound (arrow in c) in the medial left thigh. Extravasated contrast material (arrowheads in a and b) is also seen. (d) Coronal thin-slab VR image from CT angiographic data reveals an area of active extravasation (arrows) from a small branch of the SFA.
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Figure 4d. Gunshot wound to the inner thigh in a 30-year-old man. (a–c) Axial contrast-enhanced multidetector CT scan (a), coronal MPR image (b), and sagittal oblique color-coded VR image (c) demonstrate muscular injury with hematoma (arrows in a and b) and an entry wound (arrow in c) in the medial left thigh. Extravasated contrast material (arrowheads in a and b) is also seen. (d) Coronal thin-slab VR image from CT angiographic data reveals an area of active extravasation (arrows) from a small branch of the SFA.
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Figure 5a. Gunshot wound to the right thigh in a 16-year-old boy. (a) Sagittal oblique color-coded VR image shows the bullet entry site (arrow) with surrounding hematoma and edema (arrowheads). (b) VR image obtained with adjusted parameters reveals early filling of the femoral vein at the level of the SFA, a finding that is compatible with an arteriovenous fistula. The fistula was repaired with vein grafts after the patient developed acute ischemia of the right lower extremity.
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Figure 5b. Gunshot wound to the right thigh in a 16-year-old boy. (a) Sagittal oblique color-coded VR image shows the bullet entry site (arrow) with surrounding hematoma and edema (arrowheads). (b) VR image obtained with adjusted parameters reveals early filling of the femoral vein at the level of the SFA, a finding that is compatible with an arteriovenous fistula. The fistula was repaired with vein grafts after the patient developed acute ischemia of the right lower extremity.
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Figure 6a. Foreign object in a 39-year-old male construction worker who had fallen and accidentally fired a nail into his knee. (a) Sagittal VR image adjusted to depict bone and metal shows the path of the nail and its location in the distal femur, with extension posteriorly. (b) Sagittal color-coded VR image adjusted to depict the popliteal artery shows that the nail is within 2 cm of the artery. The nail was successfully removed surgically.
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Figure 6b. Foreign object in a 39-year-old male construction worker who had fallen and accidentally fired a nail into his knee. (a) Sagittal VR image adjusted to depict bone and metal shows the path of the nail and its location in the distal femur, with extension posteriorly. (b) Sagittal color-coded VR image adjusted to depict the popliteal artery shows that the nail is within 2 cm of the artery. The nail was successfully removed surgically.
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Figure 7a. Bicycle injury in an 11-year-old girl who presented with left thigh pain and a cold left leg. (a) Contrast-enhanced multidetector CT scan shows an unenhanced left femoral artery (arrow) and vein. (Reprinted, with permission, from reference 13.) (b, c) Sagittal MPR image (b) and coronal VR image from CT angiographic data (c) demonstrate occlusion of the left femoral artery (arrowheads in b, arrows in c) due to vessel laceration, which was surgically repaired with a venous graft.
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Figure 7b. Bicycle injury in an 11-year-old girl who presented with left thigh pain and a cold left leg. (a) Contrast-enhanced multidetector CT scan shows an unenhanced left femoral artery (arrow) and vein. (Reprinted, with permission, from reference 13.) (b, c) Sagittal MPR image (b) and coronal VR image from CT angiographic data (c) demonstrate occlusion of the left femoral artery (arrowheads in b, arrows in c) due to vessel laceration, which was surgically repaired with a venous graft.
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Figure 7c. Bicycle injury in an 11-year-old girl who presented with left thigh pain and a cold left leg. (a) Contrast-enhanced multidetector CT scan shows an unenhanced left femoral artery (arrow) and vein. (Reprinted, with permission, from reference 13.) (b, c) Sagittal MPR image (b) and coronal VR image from CT angiographic data (c) demonstrate occlusion of the left femoral artery (arrowheads in b, arrows in c) due to vessel laceration, which was surgically repaired with a venous graft.
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Figure 8a. Stab wound from an altercation in a 45-year-old man. (a) Axial contrast-enhanced multi-detector CT scan reveals a small area of contrast material extravasation in the lateral portion of the left thigh (arrowhead). (b) Coronal MIP image from CT angiographic data (image obtained after automated segmentation of bone [blue]) allows optimal evaluation of the vasculature, which would otherwise be obscured by the bones. (c) Coronal MIP image from CT angiographic data (image obtained following automated segmentation of bone) shows the area of contrast material extravasation in the lateral left thigh (arrow), arising from a small branch of the SFA.
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Figure 8b. Stab wound from an altercation in a 45-year-old man. (a) Axial contrast-enhanced multi-detector CT scan reveals a small area of contrast material extravasation in the lateral portion of the left thigh (arrowhead). (b) Coronal MIP image from CT angiographic data (image obtained after automated segmentation of bone [blue]) allows optimal evaluation of the vasculature, which would otherwise be obscured by the bones. (c) Coronal MIP image from CT angiographic data (image obtained following automated segmentation of bone) shows the area of contrast material extravasation in the lateral left thigh (arrow), arising from a small branch of the SFA.
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Figure 8c. Stab wound from an altercation in a 45-year-old man. (a) Axial contrast-enhanced multi-detector CT scan reveals a small area of contrast material extravasation in the lateral portion of the left thigh (arrowhead). (b) Coronal MIP image from CT angiographic data (image obtained after automated segmentation of bone [blue]) allows optimal evaluation of the vasculature, which would otherwise be obscured by the bones. (c) Coronal MIP image from CT angiographic data (image obtained following automated segmentation of bone) shows the area of contrast material extravasation in the lateral left thigh (arrow), arising from a small branch of the SFA.
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One of the potential pitfalls of CT angiography following trauma or surgery is artifact from high-attenuation structures like bullet fragments or other foreign matter, prosthetic joints, or orthopedic repair hardware. In a study of lower extremity arterial injury by Inaba et al (4), metallic bullet fragments were present in 19% of cases but precluded diagnostic assessment in only one of 63 cases. The use of multiple planes for visualization and of multiple renderings as well as segmentation to selectively visualize the arteries (Figs 9, 10) may facilitate evaluation. Despite these efforts, however, in selected cases, beam-hardening artifact can prevent evaluation of sections of a vessel (Fig 9).
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Figure 9a. Gunshot wound to the right upper extremity in a 30-year-old man. Coronal VR image (a), coronal MIP image (b), and sagittal VR image (c) from CT data demonstrate impacted bullet fragments in the fascial plane and muscle. The artifact from the bullet limits evaluation of a portion of the brachial artery, but no extravasated contrast material is seen.
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Figure 9b. Gunshot wound to the right upper extremity in a 30-year-old man. Coronal VR image (a), coronal MIP image (b), and sagittal VR image (c) from CT data demonstrate impacted bullet fragments in the fascial plane and muscle. The artifact from the bullet limits evaluation of a portion of the brachial artery, but no extravasated contrast material is seen.
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Figure 9c. Gunshot wound to the right upper extremity in a 30-year-old man. Coronal VR image (a), coronal MIP image (b), and sagittal VR image (c) from CT data demonstrate impacted bullet fragments in the fascial plane and muscle. The artifact from the bullet limits evaluation of a portion of the brachial artery, but no extravasated contrast material is seen.
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Figure 10a. Gunshot wound to the thigh in a 19-year-old man. (a, b) Coronal (a) and sagittal oblique (b) VR images from CT angiographic data show no femur fracture and no evidence of contrast material extravasation from the SFA. Mild arterial narrowing due to local edema (arrow in b) is noted. No complications were seen at clinical follow-up. (c–e) Coronal VR image (c) and vessel tracking images (d, e) show a streak artifact from the bullet, but segmentation of the arterial vasculature allows exclusion of an arterial tear or contrast material extravasation.
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Figure 10b. Gunshot wound to the thigh in a 19-year-old man. (a, b) Coronal (a) and sagittal oblique (b) VR images from CT angiographic data show no femur fracture and no evidence of contrast material extravasation from the SFA. Mild arterial narrowing due to local edema (arrow in b) is noted. No complications were seen at clinical follow-up. (c–e) Coronal VR image (c) and vessel tracking images (d, e) show a streak artifact from the bullet, but segmentation of the arterial vasculature allows exclusion of an arterial tear or contrast material extravasation.
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Figure 10c. Gunshot wound to the thigh in a 19-year-old man. (a, b) Coronal (a) and sagittal oblique (b) VR images from CT angiographic data show no femur fracture and no evidence of contrast material extravasation from the SFA. Mild arterial narrowing due to local edema (arrow in b) is noted. No complications were seen at clinical follow-up. (c–e) Coronal VR image (c) and vessel tracking images (d, e) show a streak artifact from the bullet, but segmentation of the arterial vasculature allows exclusion of an arterial tear or contrast material extravasation.
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Figure 10d. Gunshot wound to the thigh in a 19-year-old man. (a, b) Coronal (a) and sagittal oblique (b) VR images from CT angiographic data show no femur fracture and no evidence of contrast material extravasation from the SFA. Mild arterial narrowing due to local edema (arrow in b) is noted. No complications were seen at clinical follow-up. (c–e) Coronal VR image (c) and vessel tracking images (d, e) show a streak artifact from the bullet, but segmentation of the arterial vasculature allows exclusion of an arterial tear or contrast material extravasation.
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Figure 10e. Gunshot wound to the thigh in a 19-year-old man. (a, b) Coronal (a) and sagittal oblique (b) VR images from CT angiographic data show no femur fracture and no evidence of contrast material extravasation from the SFA. Mild arterial narrowing due to local edema (arrow in b) is noted. No complications were seen at clinical follow-up. (c–e) Coronal VR image (c) and vessel tracking images (d, e) show a streak artifact from the bullet, but segmentation of the arterial vasculature allows exclusion of an arterial tear or contrast material extravasation.
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As part of our work flow, we evaluate the skin, muscle, vasculature, and bone on all images by adjusting the VR look-up tables (Figs 11–13). This provides a comprehensive review of the extravascular components of the injury and helps determine the mechanism of injury. Editing of the data set with bone removal achieved with automated segmentation techniques is used for optimal vascular visualization (Figs 8, 13). We use an interactive watershed transform technique (Syngo Inspace4D visualization platform, Siemens Medical Solutions), which requires only minimal user interaction and allows the user to optimize the final result by editing the final image. Once the study is reviewed, images are sent from a free-standing workstation (Leonardo running InSpace [Siemens Medical Solutions]) to the picture archiving and communication system for system-wide availability. Most recently, we have begun using a client server model (WebSpace, Siemens Medical Solutions), which provides enhanced image analysis and display capabilities across the medical campus. This is especially useful in making images available quickly in the emergency department, operating room, or clinic. It also extends the use of 3D postprocessing from static images to interactive displays for our referring doctors. How this impacts the need for advanced imaging services remains to be seen.
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Figure 11a. Stab wound to the left shoulder in a 41-year-old man. Coronal VR images (a, b) and an MIP image oriented for optimal visualization of the region of interest (c) demonstrate a pseudoaneurysm (arrow in a and b, circled in c) that is separate from the main subclavian artery but probably arose from a side branch of this vessel. The patient was successfully treated with thrombin injection.
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Figure 11b. Stab wound to the left shoulder in a 41-year-old man. Coronal VR images (a, b) and an MIP image oriented for optimal visualization of the region of interest (c) demonstrate a pseudoaneurysm (arrow in a and b, circled in c) that is separate from the main subclavian artery but probably arose from a side branch of this vessel. The patient was successfully treated with thrombin injection.
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Figure 11c. Stab wound to the left shoulder in a 41-year-old man. Coronal VR images (a, b) and an MIP image oriented for optimal visualization of the region of interest (c) demonstrate a pseudoaneurysm (arrow in a and b, circled in c) that is separate from the main subclavian artery but probably arose from a side branch of this vessel. The patient was successfully treated with thrombin injection.
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Figure 12a. Multiple stab wounds to the proximal upper extremity and the wrist in a 22-year-old man. (a, b) Coronal color-coded VR images of the skin and soft tissue show bandages on the sites of injury (a) and patent upper extremity veins (b). (c) VR image optimized to display bone and vasculature shows no evidence of vascular injury.
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Figure 12b. Multiple stab wounds to the proximal upper extremity and the wrist in a 22-year-old man. (a, b) Coronal color-coded VR images of the skin and soft tissue show bandages on the sites of injury (a) and patent upper extremity veins (b). (c) VR image optimized to display bone and vasculature shows no evidence of vascular injury.
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Figure 12c. Multiple stab wounds to the proximal upper extremity and the wrist in a 22-year-old man. (a, b) Coronal color-coded VR images of the skin and soft tissue show bandages on the sites of injury (a) and patent upper extremity veins (b). (c) VR image optimized to display bone and vasculature shows no evidence of vascular injury.
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Figure 13a. Gunshot wound to the upper extremity in a 15-year-old boy. (a) VR image of the skin and muscle shows the bullet entry site (arrow). (b) VR image of the bone and vasculature reveals a humeral fracture but no arterial injury. (c, d) MPR image (c) and VR image obtained with automated segmentation of bone (blue) (d) show a comminuted midhumeral fracture. (e) MIP image obtained after automated segmentation to remove the bones allows selective visualization of the vasculature.
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Figure 13b. Gunshot wound to the upper extremity in a 15-year-old boy. (a) VR image of the skin and muscle shows the bullet entry site (arrow). (b) VR image of the bone and vasculature reveals a humeral fracture but no arterial injury. (c, d) MPR image (c) and VR image obtained with automated segmentation of bone (blue) (d) show a comminuted midhumeral fracture. (e) MIP image obtained after automated segmentation to remove the bones allows selective visualization of the vasculature.
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Figure 13c. Gunshot wound to the upper extremity in a 15-year-old boy. (a) VR image of the skin and muscle shows the bullet entry site (arrow). (b) VR image of the bone and vasculature reveals a humeral fracture but no arterial injury. (c, d) MPR image (c) and VR image obtained with automated segmentation of bone (blue) (d) show a comminuted midhumeral fracture. (e) MIP image obtained after automated segmentation to remove the bones allows selective visualization of the vasculature.
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Figure 13d. Gunshot wound to the upper extremity in a 15-year-old boy. (a) VR image of the skin and muscle shows the bullet entry site (arrow). (b) VR image of the bone and vasculature reveals a humeral fracture but no arterial injury. (c, d) MPR image (c) and VR image obtained with automated segmentation of bone (blue) (d) show a comminuted midhumeral fracture. (e) MIP image obtained after automated segmentation to remove the bones allows selective visualization of the vasculature.
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Figure 13e. Gunshot wound to the upper extremity in a 15-year-old boy. (a) VR image of the skin and muscle shows the bullet entry site (arrow). (b) VR image of the bone and vasculature reveals a humeral fracture but no arterial injury. (c, d) MPR image (c) and VR image obtained with automated segmentation of bone (blue) (d) show a comminuted midhumeral fracture. (e) MIP image obtained after automated segmentation to remove the bones allows selective visualization of the vasculature.
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Potential Pitfalls
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There are a number of specific pitfalls in the imaging of trauma patients with multidetector CT that must be addressed (7). Many of these pitfalls are common to other types of studies, whereas others are a bit more specific:
- Unless dual phase or late phase images are obtained, venous injuries may be missed. With venous phase imaging, the key is to avoid scanning too early, which results in "pseudothrombus."
- Use of a high-resolution kernel is optimal for evaluating the bones; however, the high-resolution algorithm is not optimal for vascular reconstruction or 3D mapping.
- Metal fragments can cause beam-hardening artifact and potentially "create" pseudolesions or hide subtle lesions.
- Use of MIP images alone may potentially result in failure to detect subtle injury, especially in cases of beam-hardening artifact, or in overlooking anatomic structures unless bone editing is satisfactorily completed.
- During interpretation, it can be challenging to identify vascular spasm and correctly distinguish spasm from both normal vessel and occlusion (2). Rieger et al (2) reported this difficulty as a primary source of misclassification of vessel injury in their study.
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Evidence from the Literature
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Studies of the use of CT angiography to evaluate the extremities have focused primarily on aortoiliac and run-off atherosclerotic disease. Some articles have discussed tumor imaging, whereas others have evaluated the utility of CT angiography in detecting and defining arteriovenous fistulas. Each of these articles has focused on the role of CT in the corresponding application and the demands and challenges specific to that application. Less has been written about the use of CT angiography following extremity trauma, but the articles that have been published have all been positive (2–7,10–12). The multidetector CT investigations identified to date have used four-detector CT and have revealed sensitivities of 95%–100% and specificities of 87%–100%:
- Rieger et al (2) studied a total of 87 patients over a 3-year period. Sixty-two arterial lesions were confirmed in 55 patients. The prospective sensitivity and specificity were 95% and 87%, respectively; the retrospective sensitivity and specificity were 99% and 87%, respectively.
- Inaba et al (4) reviewed 63 CT angiograms obtained for arterial injury in 59 patients and found CT to be diagnostic in 98.4% of cases. They concluded that CT angiography is "a sensitive and specific non-invasive imaging modality for arterial evaluation in the injured lower extremity that may replace catheter-based angiography in most patients" (4). Sensitivity and specificity were 100% for clinically significant arterial injury.
Results from 16- and 64-detector CT investigations should further improve diagnostic efficacy. In fact, triage protocols are evolving as technology advances. Following the installation of a 64-detector CT scanner in their level 1 trauma center, Anderson et al (12) reported (with respect to diagnostic conventional angiography) that "no patient has undergone a conventional extremity angiogram in the setting of trauma."
Both single- and multidetector CT studies provide valuable information concerning mechanism of injury, patient demographics, and clinical presentation of those patients who are referred for CT angiography, as well as the spectrum of extremity arterial disease identified at CT angiography in these patients. Interestingly, in a number of studies, the mechanism of injury that resulted in clinically suspected extremity vascular lesions requiring CT angiography was more commonly blunt trauma (motorcycle accident, automobile injury to pedestrian) (54%–92% of cases), with penetrating trauma causing 8%–46% of injuries (2–4). Gunshot wounds were the primary cause of penetrating trauma (74%–80% of patients), followed by stab wounds (3–6). Other potential causes of arterial injury include displaced fracture or dislocation, with 39% of patients having a fracture in the study of lower extremity trauma by Inaba et al (4) and 32%–46% having fracture or dislocation in the studies by Soto et al (5,6). The male-to-female ratio in CT studies has ranged from 5:1 to 7:1, and patients are typically young adults (mean age, 29–37 years) (2–6).
Patients with definitive clinical evidence of arterial injury may require emergent surgical intervention without imaging. Rieger et al (2) and Soto et al (5) reported these conclusive indicators of injury to include pulsatile bleeding, rapidly expanding hematoma, identification of a thrill or bruit over a wound, and loss of pulse with a definable trajectory from the penetration site. Other clinical findings that were indications for CT angiography listed in published studies are summarized in the Table.
In series that have included both upper and lower extremity injuries, the latter were more common (58%–81% of cases) (2,3,5,6). Upper and lower extremity vascular injuries identified with CT have included arterial spasm, stenosis, occlusion (Fig 7), dissection, pseudoaneurysm (Figs 2, 4, 11), and, rarely, rupture or transection (2–6). Arteriovenous fistulas have been detected in femoral (Fig 5), popliteal, and trifurcated vessels (4,5), with reports of arteriovenous fistula associated with pseudoaneurysm in axillary, superficial femoral, and tibial vessels (6). With use of single-detector CT, intimal flaps were seen in the SFA in two patients in each of two studies (3,5).
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Conclusions
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The excellent, although somewhat limited, results of CT angiography reported in the literature should come as no surprise considering the important role CT angiography plays in many extremity-related applications, especially peripheral vascular disease. The evolution from four- to 16- to 64-section CT is a boon for any vascular application, particularly one that is time sensitive. Another important consideration in the emergent setting is the ability to scan a patient with bone injury and simultaneously perform an extremity CT angiographic study to search for concurrent vessel injury. Whether the injury be a stab wound, a gunshot wound, or an injury from a motor vehicle accident, a CT study that allows visualization of injury to bone, muscle, and vasculature seems to be an ideal way of limiting radiation dose by decreasing the number of studies performed (eg, conventional radiography followed by CT and conventional angiography).
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Footnotes
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Abbreviations: MIP = maximum-intensity-projection, MPR = multiplanar reformation, SFA = superficial femoral artery, VR = volume-rendered, 3D = three-dimensional, 2D = two-dimensional
See the commentary by Covey following this article.
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References
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- Flohr T, Stierstorfer K, Raupach R, Ulzheimer S, Bruder H. Performance evaluation of a 64-slice CT system with z-flying focal spot. Rofo 2004;176: 1803–1810.[Medline]
- Rieger M, Mallouhi A, Tauscher T, Lutz M, Jaschke WR. Traumatic arterial injuries of the extremities: initial evaluation with MDCT angiography. AJR Am J Roentgenol 2006;186:656–664.[Abstract/Free Full Text]
- Busquets AR, Acosta JA, Colon E, Alejandro KV, Rodriguez P. Helical computed tomographic angiography for the diagnosis of traumatic arterial injuries of the extremities. J Trauma 2004;56: 625–628.[Medline]
- Inaba K, Potzman J, Munera F, et al. Multi-slice CT angiography for arterial evaluation in the injured lower extremity. J Trauma 2006;60:502–507.[Medline]
- Soto JA, Munera F, Morales C, et al. Focal arterial injuries of the proximal extremities: helical CT arteriography as the initial method of diagnosis. Radiology 2001;218:188–194.[Abstract/Free Full Text]
- Soto JA, Munera F, Cardoso N, Guarin O, Medina S. Diagnostic performance of helical CT angiography in trauma to large arteries of the extremities. J Comput Assist Tomogr 1999;23:188–196.[CrossRef][Medline]
- Miller-Thomas MM, West OC, Cohen AM. Diagnosing traumatic arterial injury in the extremities with CT angiography: pearls and pitfalls. RadioGraphics 2005;25(suppl 1):S133–S142.[Abstract/Free Full Text]
- Ota H, Takase K, Igarashi K, et al. MDCT compared with digital subtraction angiography for assessment of lower extremity arterial occlusive disease: importance of reviewing cross-sectional images. AJR Am J Roentgenol 2004;182:201–209.[Abstract/Free Full Text]
- Fishman EK, Ney DR, Heath DG, Corl FM, Horton KM, Johnson PT. Volume rendering versus maximum intensity projection in CT angiography: what works best, when, and why. RadioGraphics 2006;26:905–922.[Abstract/Free Full Text]
- Willmann JK, Wildermuth S. Multidetector-row CT angiography of upper- and lower-extremity peripheral arteries. Eur Radiol 2005;15(suppl 4): D3–D9.[CrossRef][Medline]
- Hiatt MD, Fleischmann D, Hellinger JC, Rubin GD. Angiographic imaging of the lower extremities with multidetector CT. Radiol Clin North Am 2005;43:1119–1127.[Medline]
- Anderson SW, Lucey BC, Varghese JC, Soto JA. Sixty-four multi-detector row computed tomography in multitrauma patient imaging: early experience. Curr Probl Diagn Radiol 2006;35:188–198.[CrossRef][Medline]
- Chen JK, Johnson PT, Fishman EK. Femoral artery occlusion after blunt trauma: diagnosis by multislice CT angiography. Emerg Radiol 2006; 12:244–245.[Medline]
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Abstract
Introduction
