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Original Research |
1 Department of Radiology, Boston Medical Center, 88 East Newton St., Boston, MA 02118.
Received August 1, 2004;
accepted after revision November 8, 2004.
Address correspondence to J. W. Stuhlfaut
(joshua.stuhlfaut{at}bmc.org).
Abstract
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MATERIALS AND METHODS. From January 2001 to December 2003, 57 patients were referred for CT angiography or DSA of the neck after blunt or penetrating neck trauma. All CT angiograms were acquired with a 4-MDCT scanner. The patients were divided into three groups on the basis of consecutive 12-month periods (2001, 2002, and 2003), and the initial imaging technique was recorded. The results of CT and digital subtraction angiograms were compared with operative findings and with clinical course, when available.
RESULTS. In 2001, 12 patients were referred for imaging: nine patients were evaluated initially with DSA and three patients were evaluated with CT angiography and subsequently with DSA. In 2002 and 2003, 11 and 34 patients, respectively, underwent CT angiography as the initial imaging examination. During these 2 years, no patient underwent DSA as the initial diagnostic test, but five patients underwent DSA after CT angiography for the following indications: evaluation of nondiagnostic CT angiograms (n = 1), confirmation of findings when requested by the clinical service (n = 2), and catheter-guided therapy (n = 2).
CONCLUSION. CT angiography has essentially replaced DSA as the study of choice for the initial evaluation of the neck vessels in the setting of blunt or penetrating trauma at our institution. CT angiography is adequate for the initial evaluation, allows appropriate triage of patients to conventional angiography or surgery for appropriate treatment, and can guide conservative management when appropriate.
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CT is now the main technique used for the evaluation of the trauma patient with multiple injuries. In this setting, CT has been shown to be effective in the detection and characterization of solid abdominal organ injuries, bowel and mesenteric injuries, spine and pelvic fractures, and thoracic aortic injuries [14-21]. In recent years, CT angiography has also been reported to be useful in the detection of injuries to the major arteries [2, 10-12]. Prior studies using single-detector helical CT have shown high sensitivity and specificity for detecting injuries to major vessels of the neck—the common and internal carotid arteries, proximal branches of the external carotid arteries, vertebral arteries, and proximal extremity arteries—in the setting of both blunt and penetrating trauma [2, 10-13, 22-25].
At our institution, a level 1 trauma center, we introduced neck CT angiography as an alternative to DSA for evaluating blunt and penetrating trauma patients after acquisition of MDCT technology. In this study, we evaluated the impact of the increasing use of MDCT angiography in the setting of suspected traumatic cervical arterial injury from blunt or penetrating trauma on our use of DSA.
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For this study, we retrospectively searched the radiology information system at our institution to identify all patients who underwent DSA or MDCT angiography of the neck during a 36-month period (January 2001 through December 2003). From this group of patients, we reviewed the reports of each study to identify all cases referred to angiography for evaluation of suspected vascular injury in the setting of penetrating or blunt neck trauma. This study was approved by the investigational review board at our medical center.
A total of 57 patients (43 males, 14 females) were referred for either CT angiography or DSA of the neck. Of the 57 patients, 17 underwent both MDCT angiography and DSA during the study period. The mean age of our study population was 31 years with an age range of 14-90 years. The mechanism of injury in our study population included gunshot wound (n = 21), stab wound (n = 12), motor vehicle crash (n = 12), assault with a blunt object (n = 4), attempted hanging (n = 2), fall (n = 3), crush injury (n = 1), and twisting injury (n = 2). After identifying our study population, we divided the patients into the following groups for three consecutive 12-month periods: those who underwent CT angiography as the initial diagnostic study and those who underwent DSA as the initial diagnostic study. Table 1 lists the number of patients, the mechanism of injury, and the initial diagnostic test performed during the three 12-month periods.
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DSA
All DSA examinations were performed on a single-plane imaging system
(Integris, Philips Medical Systems) by an attending neuroradiologist using
selective catheterization and serial imaging with digital subtraction
technique. Each examination was performed by obtaining a minimum of two
imaging planes per vessel. The volume of contrast agent varied with each
patient depending of the total number of vessels studied during the
examination. The extent of imaging was confined in most cases to only the
vessels with suspected injury based on clinical and physical examination
findings.
CT Angiography
All CT scans were obtained on a 4-MDCT scanner (MX8000, Philips). The
scanning parameters were as follows: 120-140 kVp, 200-250 mAs, field of view
of 200 mm, table speed of 15 mm/sec, 1 gantry rotation per sec, collimation of
1.25 or 2.5 mm (1.3- or 3.2-mm effective collimation), and reconstruction
interval of 1-2 mm. All patients received an IV injection of 100-150 mL of
ioversol (Optiray-320, Mallinckrodt Imaging) through an antecubital vein at a
rate of 3.0-4.5 mL/sec, using a power injector.
All MDCT angiograms were interpreted by an attending radiologist at a PACS workstation (Aurora [software version 6.5], Merge eFilm) using axial source images, multiplanar reformations (multiplanar reconstructions), and 3D volume-rendered images created in real-time by the interpreting radiologist with software available on the PACS workstation (Voxar 3D, Voxar). In each case, multiplanar reconstruction and 3D images were available to the interpreting radiologist and referring clinician within minutes of study acquisition. All MDCT angiograms were assessed first for technical adequacy and were reported as interpretable by the radiologist when enhancement with contrast material was adequate and visualization of the major vessels of the neck (common carotid artery, internal carotid artery, and proximal external carotid artery branches) was adequate.
CT angiography examinations were reported as positive when one or more of the following findings were present: arterial dissection, arterial pseudoaneurysm, arterial transection, or arterial occlusion. Findings were reported as indeterminate if isolated IV contrast extravasation was present without an identifiable arterial injury on the CT images. CT angiography findings were interpreted as negative when none of the criteria described was present. For this study, each CT scan was also retrospectively reviewed by consensus by two radiologists when the initial results conflicted with subsequent imaging or surgical results. However, these radiologists were unaware of other imaging or surgical findings.
Clinical and Imaging Follow-Up
For each patient who underwent CT angiography as the initial imaging study,
follow-up was obtained by comparing results with those subsequently found on
DSA or at surgery. When no additional imaging examination was performed, the
clinical course was determined on the basis of a review of the discharge
summaries in the medical records. When DSA was performed as the initial
imaging evaluation, patient follow-up was determined on the basis of the
results at surgery or review of discharge summaries in each patient's medical
record.
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In 2001, CT angiography was performed as the initial diagnostic examination in three (25%) of 12 patients, and each patient subsequently underwent catheter angiography for further evaluation. In two of these three patients, CT angiograms showed no abnormality and this result was confirmed with catheter angiography. The third patient underwent DSA for suspected pseudoaneurysm of the superior thyroidal branch of the external carotid artery based on findings present on the initial CT angiography; DSA confirmed this finding, and the injury was treated by endovascular coil embolization of the superior thyroidal artery. In the nine patients who underwent catheter angiography as the initial diagnostic examination, one patient required endovascular embolization of a pseudoaneurysm that originated from the left internal maxillary artery. Angiography findings in the other eight patients were considered negative, and no further imaging or surgical exploration was required. These eight patients recovered uneventfully.
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Of the 33 diagnostic CT angiograms, five were reported as positive for arterial injury. Findings in this group of patients included pseudoaneurysm and dissection (n = 1), pseudoaneurysm and occlusion (n = 1), isolated pseudoaneurysm (n = 1), isolated occlusion (n = 1), and pseudoaneurysm with occlusion and active extravasation (n = 1). Isolated contrast extravasation was reported as indeterminate for arterial injury in three patients. In one patient, a right common carotid artery pseudoaneurysm was identified on initial CT angiography, and catheter angiography was requested. On confirmation of the findings, the patient underwent operative repair. A second patient required endovascular coil embolization of a dissecting pseudoaneurysm originating from the left internal carotid artery (Figs. 2A and 2B). This patient also had a traumatic occlusion of the left vertebral artery that was managed without further intervention. Another patient with a pseudoaneurysm of the distal left lingual artery was treated surgically, with ligation of the proximal artery (Figs. 3A and 3B). One patient with an isolated vertebral artery occlusion was managed conservatively except for treatment of coexisting injuries. Finally, one patient with extensive active contrast extravasation into the oropharynx, occlusion of the right internal carotid artery, and left internal carotid artery pseudoaneurysm died shortly after admission secondary to associated brain injury.
Among the three patients whose initial CT angiograms showed active contrast extravasation but no additional arterial abnormality, one with oropharyngeal extravasation was subsequently treated by surgical ligation of the left lingual artery. After surgery, the patient continued to bleed and endovascular coil embolization of the left lingual and left facial arteries was required. A second patient underwent catheter angiography to evaluate for the source of active contrast extravasation into the posterior cervical region near the right vertebral artery noted on CT angiography, and no vascular injury was detected. On retrospective review of the initial CT angiogram, the reported abnormality was considered a false-positive interpretation, with the false-positive contrast extravasation thought to represent normal enhancement of the vertebral venous plexus. The third patient was monitored clinically and did not require further imaging or surgical exploration. Retrospective review of this CT angiogram showed a small amount of contrast extravasation into the posterior cervical region of the neck. This contrast collection was considered to be caused by an injury to a small artery or vein.
In the remaining 25 patients in whom the initial CT angiography findings were considered negative, two patients were explored surgically despite negative CT angiography findings because of a high clinical suspicion for vascular injury based on the mechanism of injury; in both cases, no vascular injury was identified. Three other patients were subsequently imaged using MR angiography of the head and neck for evaluation of suspected intracerebral vascular pathology as a cause for persistent neurologic systems; all MR angiograms were interpreted as negative.
In summary, CT angiography was performed as the initial imaging examination in 48 patients and DSA as the initial imaging examination in nine patients (none after December 2001). During 2001, DSA was performed in each patient who underwent CT angiography (two for further diagnostic evaluation, one for therapeutic intervention). Starting January 2002, only five patients subsequently underwent DSA after CT angiography (two for further diagnostic evaluation, two for therapeutic intervention, and one after initial nondiagnostic CT angiography).
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Of the three reported noninvasive imaging techniques, CT angiography is perhaps the most reliable and most readily available examination and is available to emergency department physicians and trauma surgeons. The advent of MDCT offers improved spatial resolution and faster scanning times that are well suited for evaluation of the major vessels of the neck. At our institution, CT angiography is available 24 hr, and all data are readily accessible via teleradiology, which allows the attending radiologist to quickly review images when questions arise off-hours after the preliminary interpretation by the on-call radiology resident. CT angiography also saves time because it can be performed within minutes of patient arrival to the emergency department, whereas DSA is often delayed until the call team is assembled.
Unlike MR angiography, CT angiography is generally available in most emergency radiology departments and can be performed at the time of diagnostic imaging for other organ systems in the patient with multiple injuries from trauma. Even when MR angiography is available immediately, the time needed for the examination may be prohibitive even in hemodynamically stable patients. In addition, flow effects, artifacts, and limited spatial resolution compared with CT may limit the sensitivity of MR angiography for detecting clinically significant injuries. CT angiography offers advantages over color Doppler sonography including lack of operator dependence and ability to image patients with difficult anatomy or with neck hematomas that are not easily amenable to sonographic scanning [2].
CT angiography has additional advantages that are based in part on the improvement of 3D imaging techniques available to radiologists today. In the past, the use of 3D software has been limited by lack of immediate availability to the radiologist and referring surgeon at the time of initial interpretation because multiplanar reformation and 3D imaging have been typically performed at a separate workstation. With the integration of 3D software in the PACS workstation, 3D images are now readily available and can aid in the interpretation of CT angiography examinations by allowing rapid reconstruction in nonstandard coronal and sagittal oblique planes and in 3D volume-rendered or shaded-surface displays. The 3D and multiplanar images are often helpful to the referring surgeon because they offer images similar to conventional angiography and they can help to localize the exact site of vascular injury with respect to bone (e.g., mandible), solid organ, and skin surface landmarks. Although the specific utility of multiplanar reconstruction and 3D images was not addressed in our review, such reconstructions were available and were routinely performed by the interpreting radiologist at the time of initial interpretation.
In this study, we report our experience with the use of MDCT angiography as the initial imaging examination for suspected cervical arterial injury in the setting of both blunt and penetrating neck trauma and the effect of the increasing use of CT angiography on the role of catheter angiography at our institution. During the 3-year period of this retrospective study, eight (14%) of 57 patients in the study population had vascular injuries. When CT angiography was performed as the initial imaging examination, seven (15%) of 48 patients had cervical arterial injuries. This percentage of positive results is in accordance with the results reported by Munera et al. [2] in the largest CT angiography series reported in the literature to our knowledge.
Several results from our review are worth noting. During the first 2 years of the study, 12 and 11 patients, respectively, were referred for CT angiography of the neck. In 2003, 34 patients were referred for neck CT angiography. This increase in the number of examinations is likely related to the noninvasive nature of CT angiography, the increase in experience and confidence of radiologists in CT angiography interpretation, and the increase in experience and confidence of referring physicians in managing patients on the basis of CT angiography results. It is also likely that patients who in the past were either managed conservatively (without any imaging) or taken directly to the operating room without imaging are now being evaluated using CT angiography. This may account for the increased number of positive examinations seen in 2003 when compared with both 2001 and 2002. In addition, the ease in which the examination can be performed lends to potential overuse, and thus the increase in negative examinations may be related to studies that were performed when objective clinical findings were equivocal. The increased use of CT angiography was most notable in the evaluation of the blunt trauma patient. The number of examinations performed in the setting of blunt trauma increased five times from 2001 to 2003 (from 3 to 15, respectively), whereas the number of examinations performed in the setting of penetrating trauma doubled during the same time period (from 9 to 19, respectively).
A previous report suggested that CT angiography is limited when evaluating the proximal branches of the external carotid artery [2]. However, that study reported experience with single-detector technology. In our study, CT angiography identified two patients with pseudoaneurysms of the external carotid branch arteries and appropriately guided management in each case. The advent of MDCT allows improved spatial resolution, and the diagnostic potential of CT angiography in the acute trauma patient will undoubtedly increase with the introduction of CT scanners with more than 16 detector rows.
Limitations of this retrospective study include the lack of long-term follow-up for each patient in the study population. Because injuries to small vessels may become symptomatic later, some such injuries may have been missed by either DSA or CT angiography. In addition, we did not obtain confirmatory imaging in all patients who underwent CT angiography as the initial diagnostic test. Thus, we do not know what the true sensitivity or specificity of MDCT angiography is in our patient population. Finally, only one of three patients in our study population with isolated contrast extravasation into the soft tissues underwent DSA immediately after the initial CT angiography examination. Future studies should address the issue of isolated soft-tissue contrast extravasation without other evidence of arterial injury and should better define the role of DSA in the setting of isolated IV contrast extravasation.
Despite the limitations of this study, our results show the impact of the introduction of MDCT angiography on the use of DSA at our institution. After 2001, CT angiography was the sole imaging method for the initial evaluation of the cervical vessels. CT angiography has essentially replaced DSA as the study of choice for the initial evaluation of the neck vessels in the setting of blunt or penetrating trauma at our institution. Only a minority of patients will require DSA after CT angiography for therapeutic interventions or for further diagnostic investigation when initial results are equivocal or nondiagnostic. Furthermore, CT angiography allows appropriate triage of patients to conventional angiography or surgery for appropriate treatment and can guide conservative management when appropriate. On the basis of our experiences at our trauma center, we think that the current role of DSA should be limited to evaluating patients with nondiagnostic CT angiography, evaluating questionable CT angiography findings, and guiding catheter-directed endovascular therapy.
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