Application of spiral computerized tomography in the study of traumatic lesions of the thoracic aorta

PURPOSE: Acute thoracic aortic injuries account for up to 10-20% of fatalities in high-speed deceleration road accidents and have an estimated immediate fatality rate of 80-90%. Untreated survivors to acute trauma (10-20%) have a dismal prognosis: 30% of them die within 6 hours, 40-50% die within 24 hours, and 90% within 4 months. We investigated the diagnostic accuracy of Helical Computed Tomography (Helical CT) in acute traumatic injuries of the thoracic aorta, and the role of this technique in the diagnostic management of trauma patients with a strong suspicion of aortic rupture. MATERIAL AND METHODS: We compared retrospectively the chest Helical CT findings of 256 trauma patients examined June 1995 through August 1999. All patients underwent a plain chest radiograph in supine recumbency when admitted to the Emergency Room. Chest Helical CT examinations were performed according to trauma score, to associated traumatic lesions and to plain chest radiographic findings. All the examinations were performed with no intravenous contrast agent administration and the pitch 2 technique. After a previous baseline study, contrast-enhanced scans were acquired with pitch 1 in 87 patients. All examinations were assessed for the presence of mediastinal hematoma, periaortic hematoma, traumatic pseudodiverticulum, irregular aortic wall or contour and intimal flap as signs of aortic rupture. RESULTS: Helical CT showed thoracic aortic lesions in 9 of 256 patients examined. In all the 9 cases we found a mediastinal hematoma and all of them had positive plain chest radiographic findings of mediastinal enlargement. Moreover, in 6 cases aortic knob blurring was also evident on plain chest film and in 5 cases depressed left mainstem bronchus and trachea deviation rightwards were observed. All aortic lesions were identified on axial scans and located at the isthmus of level. Aortic rupture was always depicted as pseudodiverticulum of the proximal descending tract and intimal flap. We also found periaortic hematoma in 6 cases and intramural hematoma in 1 case. There were no false positive results in our series: 7 patients with Helical CT diagnosis of aortic rupture were submitted to conventional aortography that confirmed both type and extension of the lesions as detected by Helical CT, and all findings were confirmed by gross inspection at surgery. No false negative results have been recorded so far: untreated aortic ruptures are fatal within 4 months in 90% of patients, or they may evolve into chronic pseudoaneurysm in about 5% of survivors. CONCLUSIONS: In our experience Helical CT had much higher diagnostic sensitivity and specificity than plain chest radiography. In agreement with larger published series, in our small one the diagnostic accuracy of Helical CT was 100% in the evaluation of traumatic aortic ruptures. Moreover, Helical CT is faster and less invasive than conventional aortography, which makes this diagnostic modality increasingly used and markedly improves the management of the serious trauma patient. The more widespread use of this diagnostic tool has permitted to standardize the technique and now Helical CT can be used not only as a screening modality for patients that undergo digital aortography, but also as a reliable diagnostic method for surgical planning.     

Unenhanced dynamic mediastinal computed tomography in the selection of patients requiring thoracic aortography for the detection of acute traumatic aortic injury

In our institution, the selection of patients who require thoracic aortography to evaluate for acute traumatic aortic injury (ATAI) is based upon an appropriate mechanism of injury and radiologic demonstration of a mediastinal hematoma. When plain chest or chest and/or mediastinal radiographs demonstrate a mediastinal hematoma, the patient undergoes thoracic aortography as promptly as is clinically feasible. If the plain film studies are negative for mediastinal hematoma, thoracic aortography is not performed because the patient is presumed not to have an ATAI. When the plain film studies are equivocal and the patient is stable, unenhanced computed tomography (CT) of the mediastinum is used to evaluate for a mediastinal hematoma. CT signs of a mediastinal hematoma include a soft tissue density, representing the hematoma admixed with mediastinal fat, which obscures or obliterates the normal aortic-mediastinal fat interface; hematoma admixed with fat of the right paratracheal stripe causing increased width and density of the stripe; and hematoma surrounding, and frequently displacing, the esophagus to the right of its normal position. Six of 36 patients (17%) with mediastinal hematoma demonstrated by unenhanced mediastinal CT had ATAI by thoracic aortography and confirmed surgically. The thoracic aortograms of the remaining 30 of 36 patients (83%) were negative. Sixty-three of 100 patients (63%) with equivocal plain chest or mediastinal radiographs had negative mediastinum by unenhanced CT. All 63 patients (100%) with normal mediastinal CT and who did not have thoracic aortography were discharged from the hospital 1–42 days (mean, 9.3 days) post-injury without clinical or radiographic signs of aortic rupture. Supported in part by the John S. Dunn Research Foundation.     

Superior mediastinal widening from spine fractures mimicking aortic rupture on chest radiographs

Mediastinal widening on chest radiographs associated with lower cervical and upper thoracic spine fractures can mimic the radiographic findings of aortic rupture. Frontal chest radiographs from 54 patients with traumatic fractures of at least one vertebral body from C6 to T8 were examined for signs suggestive of aortic rupture. These signs included (1) mediastinal width equal to or greater than 8 cm; (2) presence of a left apical cap; (3) a right paratracheal stripe of 5 mm or more; and (4) deviation of the nasogastric tube, when present, to the right of the T4 spinous process. Thirty-seven patients (69%) had radiographic signs suggestive of aortic rupture on the initial anteroposterior chest film. The single patient in this group who actually had an aortic rupture died in the emergency department shortly after admission. The spine fracture could be identified on the initial chest radiograph in 19 (51%) of the 37 patients. These results show that a widened mediastinum on chest radiographs after trauma is not a specific finding of aortic rupture. In these cases, the upper thoracic spine should be examined closely on the initial frontal chest radiograph for evidence of fracture. If a fracture of the upper thoracic spine is identified, an aortic rupture is unlikely in the absence of clinical signs and symptoms supporting this diagnosis.     

Value of chest radiography in excluding traumatic aortic rupture

A retrospective review of chest radiographs from 205 patients with blunt chest trauma who also underwent aortography was performed. Forty-one of the 205 had aortographically proved aortic rupture. Discriminant analysis of 16 radiographic signs indicated that the most discriminating signs were loss of the aorticopulmonary window, abnormality of the aortic arch, rightward tracheal shift, and widening of the left paraspinal line without associated fracture. No single or combination of radiographic signs demonstrated sufficient sensitivity to indicate all cases of traumatic aortic rupture on plain chest radiographs without the performance of a large number of aortographically negative studies. The bedside anteroposterior "erect" view of the chest proved far more valuable than the supine view in detecting true-negative studies. Despite significant reader variability in the interpretation of the various radiographic signs, in general the analysis confirmed the role of chest radiography in this clinical situation, but suggests that its most beneficial use is in excluding the diagnosis and eliminating unwarranted aortography rather than in predicting aortic rupture.     

Sudden death due to rupture of major aortopulmonary collateral arteries in a patient with tetralogy of Fallot and pulmonary atresia

We report a case of fatal mediastinal hemorrhage in a 20-year-old man caused by rupture of the major aortopulmonary collateral arteries (MAPCAs). The patient had an unoperated tetralogy of Fallot with pulmonary atresia. Plain chest radiograph and computed tomography showed a large hematoma in the upper mediastinum. Previous cardiac angiography, performed 6 years previously, demonstrated markedly tortuous vascular structures arising from the inferior aspect of the aortic arch. In this case, the mediastinal hemorrhage was thought to be due to rupture of the MAPCAs. If a patient presents with sudden cardiac arrest and mediastinal dilatation, and unoperated congenital heart disease is suggested by a plain chest film, the radiologist should consider the possibility, although rare, of mediastinal hemorrhage resulting from rupture of the MAPCAs.     

Thoracic aortic rupture: advantages of intraarterial digital subtraction angiography

Sixty-one consecutive patients with blunt thoracic trauma underwent intraarterial digital subtraction angiography (IA-DSA) of the thoracic aorta because of obscuration of the aortic knob or mediastinal widening on chest radiographs. Ten of these patients had aortic ruptures diagnosed by IA-DSA. Digital subtraction aortography proved 100% accurate as indicated by results of surgery, conventional arteriography, serial chest radiography, and clinical follow-up. The method was 50% faster compared with conventional aortography and saved significantly on film costs. The potential for use of smaller caliber catheters and a decrease in contrast requirements also make this method safer than conventional arteriography. We recommend IA-DSA as the procedure of choice when emergency aortography is warranted.     

主动脉弓离断三联征的放射诊断

目的：分析与评价主动咏弓离断(IAA)三联征的影像学表现及其诊断价值。方法：回顾性分析20例患者的X线平片、心导管检查和心血管造影资料,其中7例行电子束CT检查,11例行手术治疗,逐个分析其X线平片征象并与心血管造影及手术结果对照。结果：X线胸片显示肺血多,肺动脉段明显凸出和心脏增大(n=20);右上纵隔大血管影变窄(n=16);主动脉结观察不清(n=16);侧位或左前斜位见低位主动脉弓(n=12);降主动脉的顶端与主肺动脉处同一水平(n=8)。心导管检查均提示肺动脉高压、主动脉弓畸形、动脉导管未闭。心血管造影诊断IAA(A型)13例,IAA(B型)5例,其中合并主肺间隔缺损4例,合并右室双出口2例,右肺动脉起源异常1例。结论：X线平片对该畸形的诊断有一定的价值,多数病例可作诊断,心血管造影是诊断该病的最可靠方法。     

Plain-film criteria for excluding aortic rupture in blunt chest trauma

Emergency room supine chest films of 86 consecutive patients with blunt chest trauma and possible aortic rupture were reviewed. Sixteen radiographic signs were analyzed independently and in combination. Only two signs associated with aortic rupture were statistically significant: deviation of the nasogastric tube to the right at the T4 level and depression of the left main-stem bronchus below 40 degrees from the horizontal. False positives and false negatives occurred with each individual radiographic sign. However, if the aortic knob and contour appeared normal and the trachea and nasogastric tube were not deviated, no case was found of aortic rupture in 4 consecutive years of experience. These four signs can be used to exclude the diagnosis of aortic rupture in patients with blunt chest trauma.     

Acute posttraumatic rupture of the thoracic aorta: The role of angiography in a 7-year review

Between 1983 and 1989, 15 patients with acute rupture of the thoracic aorta by blunt trauma were seen. Superior mediastinal widening and obscuration of the aortic arch were the most important findings on chest radiograph. Computed tomography examinations in 7 patients showed mediastinal hematomas but did not reveal aortic lesions. Definitive diagnosis of traumatic aortic rupture was established by aortography in all 15 patients. Intraarterial digital substraction angiography proved to be as accurate as conventional film aortography and saved time.     

Evaluation of the role of chest computed tomography in the management of trauma patients

The role of chest computed tomography (CT) in the management of trauma patients is evolving. The present study reviews the chest radiographic and chest CT findings in a group of trauma patients to determine the clinical impact of findings noted exclusively on chest CT.Fifty-five trauma patients examined with chest radiography and chest CT and whose clinical charts were available for review were retrospectively identified. There were 46 men and 9 women, with a mean age of 39 years. The presence (and size) of pneumothorax, hemothorax, pulmonary contusion, and fractures was tabulated for the chest radiographs and CT scans. The presence of mediastinal widening on chest radiographs and all mediastinal findings on CT were noted. The results of aortography, when applicable, were correlated. The clinical charts were reviewed to assess the impact of CT findings on patient management.Pneumothorax (P<0.05), hemothorax (P<0.05), pulmonary contusions, and fractures were noted more frequently on chest CT than on chest radiography. However, clinical management was affected in only three (5%) of these patients. Chest CT findings related to the mediastinum affected patient management in 13 (24%) patients. CT obviated the need for aortography in 7 of 10 patients with mediastinal widening on chest radiographs. Six other patients had aortography, four for mediastinal hematoma with a normal-appearing aorta on contrast medium-enhanced CT, and two for mediastinal hematoma and aortic injury on CT.Despite detection of significantly more pneumothoraces and hemothoraces on chest CT, clinical management was affected in only a small minority (5%) of cases. CT did prove useful in evaluating the mediastinum, obviating the need for aortography in 7 of 10 patients with a widened mediastinum on chest radiography and accurately diagnosing the presence and site of aortic injury in the two patients with that diagnosis.     

Blunt thoracic aortic injury in children

Thoracic aortic injury (TAI) in children secondary to blunt chest trauma is rare and less well documented than TAI in adults. To further establishe the incidence and radiographic manifestations of this severe injury, we reviewed our experimence with TAI in children over an 8-year period. We performed a computer search from the Trauma Registry at our level I trauma center for all cases of TAI among patients 16 years of age or younger who were admitted after sustaining blunt chest trauma between August 1984 and September 1992. We reviewed our records of all thoracic aortograms performed on children for blunt trauma during this same time period. Indication for angiography was determined by review of chest radiographs and medical records of all patients who underwent thoracic aortography. We reviewed medical records and all available chest radiographs, computed tomography (CT) examinations, and thoracic aortograms of children diagnosed with TAI. Of 308 children admitted with blunt chest trauma, 26 (8.4%) underwent angiography to exclude aortic or great vessel injury. Of these 26 patients, three (11.5%) were diagnosed with TAI, and one patient demonstrated a traumatic pseudoaneurysm of the proximal left subclavian artery. The incidence of TAI among children who sustained blunt chest trauma was 1.0% in our series. All three patients with TAI in our series were male, ages 10–12 (mean: 11 years). Chest radiographs on two of the patients with TAI revealed mediastinal widening, ill-defined aortic outline, shift of the trachea and nasogastric tube, and depression of the left main stem bronchus. The chest radiograph in one patient with TAI was technically inadequate. CT demonstrated abnormalities in two patients. Angiographic findings were similar to those seen in adults. TAI in children is rare, occurring in 1% of children sustaining blunt chest trauma in our series. Our findings support previous reports that the plain film, CT, and angiographic findings with this injury resemble those found in adults.     

46例肺栓塞的胸部螺旋CT及X线平片影像学比较

提高胸部Ｘ线平片和螺旋ＣＴ对肺栓塞诊断的认识。材料与方法,经临床确诊４６例肺栓塞的影像学表现进行回顾性分析。结果胸部Ｘ线平片中７０％病例肺血管纹理改变为肺少血“缺血区”,呈肺叶、段分布;４６％病例有肺动脉、肺门动脉增粗;３０％病例贝肺周的浸润灶、纤维索条影及太肺不张;     

纵隔型肺癌的影像学表现

目的:探讨纵隔型肺癌的影像学表现,为临床制定合理的手术方案提供更准确的信息。方法:回顾性分析15例经手术和病理证实的纵隔型肺癌的X线和CT资料。所有病人均行胸部正侧位片和CT平扫检查,13例病人还行CT增强扫描。结果:15例病人中有8例位于右肺门,3例位于左肺门,右上肺和左上肺各2例。平片显示纵隔增宽,气管受压移位,4例可见胸腔积液。CT显示肿块位于纵隔胸膜下,与纵隔呈宽基底相贴,边缘不规则,增强后不均匀强化。结论:结合临床症状和体征,仔细分析影像学表现,大部分纵隔型肺癌都可以作出准确诊断。     

Epidural abscess resulting from traumatic esophageal rupture secondary to a flexion-extension injury

An epidural abscess developed several weeks after a traumatic esophageal rupture secondary to a reported flexion-extension injury in a restrained back seat passenger in a motor vehicle accident. Chest radiograph and an Indium study suggested the possibility of a posterior mediastinal abscess. Chest computed tomography (CT) also noted epidural abscess and osteomyelitis, which were confirmed by magnetic resonance imaging (MRI). Diagnosis was delayed significantly by underinterpretation of both chest and CT findings. Obvious positive findings (lower lobe infiltrate on chest radiograph and posterior mediastinal abscess on CT) were noted, but more subtle and very important findings of superior mediastinal widening and extra pulmonary gas bubbles on the chest radiograph and extradural disease displacing the spinal cord on CT were not described. We can find no previously reported case of esophageal rupture associated with flexion-extension injury of the neck. It is also extremely rare for esophageal rupture to remain asymptomatic for more than several hours.     

Aortic dissection: a statistical analysis of the usefulness of plain chest radiographic findings

Findings on plain chest radiographs of patients with aortic dissection are variable and often overlap those of patients without dissection. To determine which findings were most useful in predicting aortic dissection, plain chest radiographs from 36 patients with aortographically proven aortic dissection and 36 patients from a control population were randomized and analyzed independently by five radiologists for the presence of various radiographic features associated with this condition. A widened aortic knob, widened descending aorta, and widened mediastinum showed the greatest interobserver agreement (p less than .001) although the overall interobserver agreement was poor. The final conclusion of the radiologists was a better predictor of dissection than any of the individual radiographic features alone. Widening of the mediastinum (p less than .001) and widening of the aortic knob (p less than .012) were the only two radiographic features of significance in predicting dissection. In a stepwise multiple logistic regression model, the radiologists achieved an overall accuracy of 85%, a sensitivity of 81%, and a specificity of 89%. Although this illustrates the usefulness of plain chest radiographs in diagnosing aortic dissection, poor interobserver agreement dictates that further definitive investigation be undertaken.     

Radiographic signs of acute traumatic rupture of the thoracic aorta

The initial chest radiographs of 54 trauma patients who were referred for angiography of the thoracic aorta were reviewed. Retrospective evaluation used eight radiographic signs that have been described in possible aortic injury. This review was undertaken to establish the occurrence and validity of these signs in the diagnosis of aortic tear. Results indicated that loss of the aortic arch contour and mediastinal widening were the most reliable signs of disruption of the aorta. In patients with at least one of these two signs, there was a high percentage of positive angiograms.     

Correlation between chest film and angiographic assessment of left ventricular size.

In 76 adult males quantitative angiographic measurements of left ventricular size were compared to 12 plain chest film measurements of heart size and shape. Of the 18 normal cases, only Rigler's B measurement correlated with left ventricular volume (r = .64). However, this correlation was not statistically significant. Of the 58 patients with isolated aortic valve disease, 19 had increased left ventricular mass (hypertrophy) and 39 had both increased left ventricular end-diastolic volume and mass (hypertrophy and dilatation). In the hypertrophy group, plain film heart volume was the most sensitive detector of an enlarged left ventricle (21% false negative rate) and correlated with left ventricular end-diastolic volume (r = .62). Using stepwise discriminant analysis, the combination of heart volume, leftness of the heart, apex position, and roundness of the left ventricle decreased the false negative rate to 5%. In the hypertrophy and dilatation group, plain film heart volume had the highest correlation with left ventricular volume and mass (r = .66) and a false negative rate of 8%. No single variable or combination of variables could usefully discriminate between the hypertrophy and hypertrophy and dilatation groups. These data support the conclusion that plain film heart volume is the best single measurement for detecting left ventricular enlargement.     

右室异常肌束X线平片诊断的评价

评价Ｘ线平片对右室异常肌束的诊断价值及限度。材料与方法：分析经手术证实的右室异常肌束７３例的Ｘ线平片表现，根据血液动力学改变，将此病分为３型：无分流型；左向右分流型；右向左分流型。结果；在Ｘ线平自上，右室异常肌束可表现下列征象；（１）右室增大与心腰凸出不相称；（２）左室增大与肺血增多不相称；（３）右室流出道入呈局限性缺陷。     

Chronic posttraumatic aneurysm of the thoracic aorta: surgically correctable occult threat

The clinical and radiographic findings of 11 patients with a chronic traumatic aneurysm were reviewed. Each patient had been under medical care at the time of injury but acute aortic rupture was not recognized in any, although several signs of mediastinal hemorrhage were present on the immediate posttraumatic radiographs. The average time between the initial trauma and the detection of the aneurysm was 5.3 years. Seven patients showed no or minimal specific complaints. Four patients showed more or less severe complaints of dysphagia, severe thoracic pain, hoarseness, and dyspnea. In all patients the chest radiograph was abnormal: Four patients showed a mass lesion at the level of the aortic knob. The other seven patients showed contour deformities of the descending aorta, sometimes subtle, with (five) or without (two) calcification. Esophagography and CT were useful in several patients. In the light of the unpredictable course of a chronic traumatic aneurysm and the low operative mortality, early operation after detection is recommended. Preoperative angiography is usually desirable.     

Traumatic injuries: imaging of thoracic injuries

Chest trauma is one of the most important causes of death, in particular in individuals under the age of 40 years. The mortality rate for chest trauma, often related to motor vehicle accidents, is approximately 15.5%; it increases dramatically to 77% with associated shock and head injury (Glasgow scores of 3-4). The accurate diagnosis of pathologies consequent to blunt chest trauma depends on a complete knowledge of the different clinical and radiological manifestations. The first diagnostic approach is classically based on chest X-ray often carried out on supine position at the hospital admission. A CT study must then be performed in all chest trauma patients in whom there is even the smallest diagnostic doubt on plain film. In particular, spiral CT (SCT) assumes a fundamental role in the demonstration of mediastinal hemorrhage and direct signs of aortic lesions. At present, SCT is routinely part of a diagnostic evaluation which also includes scans of the brain and the abdomen in polytraumatized patients. Magnetic resonance is the ideal method for visualizing diaphragmatic lesions. Furthermore, recent reports have demonstrated the high diagnostic value of MR in evaluating aortic injuries. The purpose of this article is to review the most common radiological patterns related to chest trauma.