Spiral CT findings in a case of pulmonary sequestration

Pulmonary sequestration has always been diagnosed by direct demonstration of the vessels tributary to the lesion, usually by angiography. Conventional CT can identify the arterial supply in only two thirds of cases. We report a case of pulmonary sequestration diagnosed using Spiral CT, based on the demonstration of both arterial supply and venous drainage. The capabilities of Spiral CT to detect subtle vessel abnormalities and to yield reliable multiplanar imaging enabled us to show the whole course of both the artery and the vein tributary to the lesion. Axial images were the most useful ones to diagnose pulmonary sequestration; 2D and 3D reconstructions were useful for a detailed and immediate spatial depiction of the parenchymal abnormality and of its vascular pedicle.     

多层螺旋CT及三维重组技术对肺隔离症的诊断价值

目的:探讨螺旋CT三维血管成像(3D SCTA)对显示肺隔离症异常血管的价值.方法:回顾性分析15例经手术和病理证实的肺隔离症患者的胸部CT平扫、增强及病灶区最大密度投影(MIP)和多平面重组(MPR)的影像资料.结果:12例为肺叶内型,3例为肺叶外型;10例位于左下肺,5例位于右下肺;增强CT显示13例有异常供血动脉自胸主动脉进入两下肺病灶;MIP或MPR显示了经手术证实的16条异常供血动脉中的15条,并清楚显示了其分支和行程,与术中所见基本一致.结论:螺旋CT血管成像(SCTA)及其重组技术能很好地显示肺隔离症的异常血管,对肺隔离症的诊断具有重要的临床应用价值,可以取代血管造影.     

螺旋CT三维重建在肺隔离症诊断中的应用

目的 评价螺旋CT三维重建在肺隔离症诊断中的作用。方法 对10例肺隔离症进行回顾性分析。2例行肺血管造影、2例手术、6例CT血管成像显示病变由异常体动脉供血。所有检查采用Philips Tomoscan SR 7000或GE LighhtSpeed Plus多层面CT扫描机，将图像传输至工作站进行三维重建。图像经2位(或2位以上)放射科医师阅片分析。结果 10例肺隔离症病灶1例位于右下叶，9例位于左下叶，异常体动脉供血8例来自胸主动脉，2例来自腹腔干。CT平扫表现为斑片状阴影4例，肺门肿块并邻近肺血管影增多迂曲3例，肺气肿区内条状高密度影2例，多囊融合肿块影1例。10例增强扫描有9例显示异常体动脉供血，其平均直径9．7mm，7例显示引流静脉。采用最大密度投影及曲面重建可显示异常体动脉、引流静脉及其与病变结构的关系，表面阴影成像及容积重现可显示异常血管。结论 螺旋CT增强扫描三维重建可显示异常供血动脉及引流静脉，是诊断肺隔离症的首选检查方法。     

Pulmonary sequestration: demonstration of blood supply with 2D and 3D MR angiography

Pulmonary sequestration is a relatively rare but clinically significant congenital anomaly. This disease is a spectrum of disorders involving the pulmonary airways, the arterial supply to the lungs, the lung parenchyma and its venous drainage. Traditionally, the diagnosis of pulmonary sequestration has been made definitively with arterial angiography. It is imperative for the preoperative evaluation that the arterial supply and venous drainage of the sequestered segment is identified. Several cases of MR diagnosis and preoperative evaluation of pulmonary sequestration and blood supply have been reported. In this case, MR imaging was able to provide important information about systemic blood supply via intercostal arteries and regular venous drainage. Furthermore this imaging technique revealed a second pulmonary sequestration in the dorsal phrenicocostal sinus that was not diagnosed before.     

CT扫描对肺隔离症的诊断价值

目的 :探讨CT扫描对肺隔离症的诊断价值。方法 :搜集经手术病理、主动脉造影证实的 2 1例肺隔离症。所有病例均行CT平扫及增强扫描 ,其中 5例行螺旋CT动态增强扫描。结果 :16例CT表现为含气体或液体的囊肿和 /或软组织肿块 ,5例肿块周围可见肺气肿。 16例非含气囊肿平扫密度均匀 ,增强扫描 7例无明显强化、5例为薄壁环形强化、4例为厚壁周围性强化。无强化区的病理成分为粘液、脓液或胶样液体。CT显示出 14支异常供血血管 ( 14 / 2 1) ,螺旋CT显示率 ( 4 / 5 )高于普通CT( 10 / 16)。结论 :肺隔离症的主要CT表现是囊肿、结节或肿块 ,增强CT扫描、螺旋CT动态增强扫描能发现平扫所不易显示的结节和肿块内部的囊性成分 ,有助于隔离肺异常供血血管的显示 ,后者对发现细小的异常供血血管有较大价值     

螺旋CT在叶内型肺隔离症诊断中的价值

目的 探讨螺旋CT在叶内型肺隔离症诊断中对异常供血动脉显示的作用和方法。方法 将14例肺隔离症患者的螺旋CT扫描方案分为2组，第1组8例，单层螺旋扫描；层厚3mm，床进4.5mm/s，重建间隔1.5mm者5例，多层螺旋扫描；实际层厚2.5mm，有效层厚3.2mm者3例。对比剂流率2.5ml/s；启动智能扫描探测到腹主动脉上段强化最佳时开始扫描，扫描资料交工作站行三维图像后处理。第2组6例为单层螺旋扫描，其中5例扫描层厚5mm，床进5mm/s；1例扫描层厚10mm，床进10mm/s。结果 病灶位于右下肺2例，左下肺12例，表现肿块者11例，边缘清楚的结节者3例。14例均见异常供血动脉，发自腹主动脉11例，胸主动脉2例，脾动脉1例；其中多层螺旋CT三维图像后处理显示异常供血动脉最佳。上述异常供血动脉均经外科手术证实。引流静脉均未显示。结论 在肺隔离症定性诊断中，多层螺旋CT横断面结合三维图像后处理利于显示异常供血动脉，有可能替代传统的血管造影。     

Pulmonary sequestration in the adult. Diagnostic contribution of angiography

PURPOSE: The diagnosis of pulmonary sequestration is based on demonstration of mal-developed lung tissue, feeding on abnormal systemic level. We investigate the role of angiography in the diagnosis of pulmonary sequestration in adult patients. MATERIAL AND METHODS: 1987 to 1998 we examined 9 patients with suspected pulmonary sequestration who were subsequently submitted to surgery. The patients were 3 women and men; 6 of them were symptomatic and 3 asymptomatic. Six patients were examined with CT of chest and upper abdomen, thoracoabdominal aortography and selective arteriography of the abnormal vessel; one patient also submitted to left angiopneumography. One patient underwent bronchography and another one MRI. RESULTS: An unquestionable diagnosis was made in 8 cases, namely 6 of intralobar and 2 of extralobar sequestration, and confirmed surgically. The only questionable case was diagnosed at histology as extralobar pulmonary sequestration atypically fed by thin branches from the left diaphragmatic artery. CONCLUSIONS: Angiography demonstrated the abnormal arterial feeding typical of pulmonary sequestration in all cases but one. The evidence of venous drainage was the key sign to diagnose extra-versus intralobar sequestration. Therefore we conclude that angiography remains an essential tool in the diagnosis of pulmonary sequestration, notwithstanding the great potentials of Helical CT of MR angiography.     

Predictors of patient response to pulmonary thromboendarterectomy

OBJECTIVE: We sought to identify imaging features that help predict surgical success in patients undergoing thromboendarterectomy. MATERIALS AND METHODS: Thirty-nine consecutive patients who underwent pulmonary angiography and thromboendarterectomy during 1995 and 1996 were included. Thirty-four underwent helical CT angiography. Measurements of postoperative pulmonary vascular resistance were compared with preoperative imaging features and preoperative pulmonary vascular resistance. RESULTS: The best imaging indicators of a relatively high postoperative pulmonary vascular resistance were the extent of small vessel disease identified on CT angiograms as segments with abnormal perfusion but normal segmental arteries (p = 0.005) and the extent of central disease (p = 0.015). Combined with preoperative pulmonary vascular resistance, these features had a strong correlation with postoperative outcome (p = 0.0005). Segmental arterial disease seen on both conventional angiography and CT angiography correlated poorly with surgical outcome. CONCLUSION: In patients with chronic thromboembolic pulmonary hypertension, CT angiographic evidence of extensive central vessel disease and limited small vessel involvement indicates a favorable surgical outcome.     

多层螺旋CT在诊断肺隔离症中的应用

目的 评价多层螺旋CT血管成像对肺隔离症的诊断能力。方法 15例经病理（14例）和血管造影（1例）证实的叶内型肺隔离症患者均经多层螺旋CT平扫与增强扫描，并采用容积再现技术，最大密度投影及多平面重建显示异常血管与病灶的关系。结果 15例肺隔离症患者中，14例的病灶位于左下叶，1例的病灶位于右下叶，异常体动脉供血全部来自胸主动脉，其平均直径1．6cm。CT平扫表现为肿块形7例，圆形或卵圆形5例，不规则形3例。增强后15例均显示异常体动脉供血。结论 多层螺旋CT血管成像技术能准确诊断肺隔离症，并可取代其他有创性检查，如数字减影血管造影等。     

Diagnosis of arterial sequestration using multidetector CT angiography

Background

Arterial sequestration is a rare congenital disorder. The diagnostic evaluation of this condition using multidetector computerized tomography (MDCT) has not been described previously. The purpose of this study was to describe the characteristic features of this disorder and to assess the use of MDCT in visualizing the characteristic anatomic features.

Methods

We retrospectively reviewed the records of seven patients with anomalous systemic blood supply to left lower lobe of the lung. All the patients had undergone MDCT angiography. To evaluate the lung parenchyma, bronchial branching pattern, and vascular anatomy, four series of images were systematically reconstructed as follows: contiguous transverse CT scans viewed at mediastinal and pulmonary window settings, oblique coronal and sagittal maximum intensity projections (MIP), multiplanar reconstruction (MPR), and three-dimensional volume-rendered images (VR) of airway and thoracic vascular structures.

Results

All 7 cases had isolated and tortuous arterial anatomy from the descending thoracic aorta to the basal segment of the left lower lobe; however, variable distribution of branches was observed. Characteristic findings of anomalous systemic arterial (ASA) supply were distinct from those seen in other pulmonary sequestration syndromes and were well visualized by the use of noninvasive MDCT.

Conclusion

Complex CT findings allow clear imaging of arterial sequestration and the ASA blood supply; MDCT angiography has demonstrated its value and accuracy in diagnosing this condition, obviating the use of digital subtraction angiography and magnetic resonance angiography for the diagnosis of arterial sequestration.     

Multidetector-row computed tomography angiography for planning intra-arterial chemotherapy pump placement in patients with colorectal metastases to the liver

PURPOSE: The purpose of this study was to evaluate the use of multidetector computed tomography (MDCT) in the preoperative arterial evaluation of patients scheduled to undergo intra-arterial chemotherapy pump placement. METHODS: Computed tomography scans of 30 patients with hepatic malignancies who were imaged with multiphase MDCT angiography for intra-arterial chemotherapy pump placement were retrospectively analyzed. Dual-phase helical CT was performed, and the arterial phase images were processed to depict the arterial anatomy and to identify pertinent anomalies. All findings were compared and correlated with surgical findings or catheter angiography if surgery was contraindicated. RESULTS: Arterial anomalies identified on CT angiography in 20 of 30 patients included a replaced right hepatic artery (RHA; n = 6) or left hepatic artery (LHA; n = 8), a replaced common hepatic artery (n = 1), an accessory RHA (n = 2) or LHA (n = 6), a replaced gastroduodenal artery (GDA; n = 2), an extrahepatic connection between the accessory RHA and the replaced RHA (n = 1), and a common origin composed of the GDA and RHA and LHA (n = 2). There were no additional arteries or anomalies identified by catheter angiography, when available, or during surgery. Only 1 variant, an accessory hepatic artery, was not located during surgery. In 2 patients, the surgical team decided that pump placement was not feasible because of overly complex anatomy as determined by CT angiography. Computed tomography angiography showed an overall sensitivity of 100% and specificity of 97%. CONCLUSIONS: Multidetector computed tomography angiography is accurate for the preoperative evaluation of normal and aberrant hepatic vasculature in patients under consideration for intra-arterial chemotherapy pump placement. Axial images alone permit recognition of vascular anomalies, including complex anatomy. Nevertheless, 3-dimensional rendering is useful to evaluate complex vascular anatomy and does not require catheter angiographic confirmation. In addition to aiding in selecting patients ideal for pump placement, MDCT permits noninvasive planning of their surgical approach.     

Siebzehnjährige Schülerin mit therapieresistenter Pneumonie

If empiric antibiotic treatment is not successful in a case of suspected pneumonia further investigations are required. We present a case where originally an intralobar, bronchopulmonary sequestration could clearly be diagnosed by a thoracic CT scan. A 3D reconstruction revealed the pathognomonic arterial supply from the thoracic aorta and the venous drainage via pulmonary vein to the left atrium. Therefore, elective resection of the sequestration was indicated.     

螺旋CT三维重建血管成像对肺隔离症的诊断价值

目的探讨螺旋CT三维重建血管成像(3D SCTA)诊断肺隔离症的价值. 资料与方法使用Siemens Somatom Plus 4 CT机对12例肺隔离症患者行胸部CT平扫、增强扫描及病灶区最大密度投影(MIP)和多平面重建(MPR).全部病例均经手术证实. 结果 10例为肺叶内型,2例为肺叶外型;8例位于左下肺,4例位于右下肺;增强CT显示11例有血管样条索影自主动脉向病灶内延伸;MIP-SCTA显示了经手术证实的14条异常血管中的13条,且清楚地显示了异常血管的起源、走行和形状. 结论 MIP-SCTA对肺隔离症的诊断具有重要的临床应用价值,可以取代血管造影.     

Preoperative evaluation of intracranial aneurysms: usefulness of intraarterial 3D CT angiography and conventional angiography with a combined unit--initial experience

PURPOSE: To assess the usefulness of intraarterial computed tomographic (CT) angiography in conjunction with digital subtraction angiography (DSA) by using a combined CT and angiographic unit in the preoperative evaluation of intracranial aneurysms. MATERIALS AND METHODS: Prospectively, 22 patients with or without subarachnoid hemorrhage underwent CT angiography in conjunction with DSA. Two radiologists independently evaluated DSA and CT angiographic images. Referring neurosurgeons were questioned as to how the additional information provided by CT angiography changed patient treatment. RESULTS: Intraarterial CT angiography was superior to DSA for use in aneurysm detection in three (12%) of 26 aneurysms and for delineation of aneurysm shape, neck, and location in more than half. In 14 (64%) of 22 patients, CT angiography demonstrated 18 additional findings: a very small aneurysm (n = 2), aneurysm shape and neck (n = 6), relationship of the aneurysm to adjacent arteries or bone structure (n = 8), and branches deriving from the aneurysm (n = 2). In four (27%) of 15 patients who underwent surgery or embolization, additional information obtained at CT angiography affected the treatment. CT angiography failed to clearly demonstrate an aneurysm adjacent to bone structures and small perforators, which were derived from the parent artery. CONCLUSION: Intraarterial CT angiography is useful for preoperative evaluation of intracranial aneurysms as a supplement to DSA.     

Assessment of vasculature using combined MRI and MR angiography

OBJECTIVE: The purpose of this study was to compare combined cine gradient-recalled echo MRI and MR angiography with conventional angiography in the evaluation of the pulmonary vascular supply in patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries. MATERIALS AND METHODS: Eleven patients who underwent both MRI and conventional angiography were retrospectively reviewed. Contiguous 2D cine gradient-recalled echo images (TR range/TE, 30-80/4.8; flip angle, 20 degrees or 30 degrees ) and 3D MR angiographic images (TR range/TE range, 3.8-5.0/1.3-2.0; acquisition time, 13-32 sec) using gadopentetate meglumine (0.1-0.2 mmol/kg) were obtained. The presence, size, and course of the pulmonary arteries (main, right, left) and major aortopulmonary collateral arteries (>/= 5 mm) were determined. Presence of minor collateral arteries (< 5 mm) was also noted. Results were compared with findings at conventional angiography. RESULTS: MRI showed all main (n = 4) and branch (n = 17) pulmonary arteries found at conventional angiography and showed the pulmonary confluence in five of six cases. MRI showed all major aortic collaterals (n = 22) with a highly significant correlation between MRI and conventional angiography measurements (r = 0.84, p < 0.001 [95% confidence interval, -0.35 to 0.40]). One coronary artery collateral was not shown on MRI examination. At MRI, 12 of 14 major and four of seven minor brachiocephalic artery collaterals were shown. MRI showed more minor aortic collaterals than angiography (22 vs 18 vessels, respectively). CONCLUSION: Combined cine gradient-recalled echo MRI and MR angiography is a reliable method for imaging pulmonary vascular supply in patients with these disorders. Additional prospective studies comparing MRI and conventional angiography may determine whether routine preoperative conventional angiography is required.     

肺部疾病的支气管动脉与肺外体循环动脉CTA分析

目的:利用CT血管造影对支气管动脉与肺外体循环动脉进行肺供血研究。材料和方法:回顾性分析16层CT胸部增强发现肺外体循环动脉参与供血的不同肺疾病患者39例(男性24例,女性15例,平均年龄63.4岁;范围,20-82岁),采用容积显示(VR)、多平面重建(MPR)、最大强度投影(MIP)进行支气管动脉与肺外体循环动脉进行重建,分析其供血特征。结果:39例病人中共显示支气管动脉128支,肺外体循环动脉42支,其中内乳动脉19支,锁骨下动脉8支,膈下动脉8支,肋间动脉5支,甲状颈干与腹腔干各1支。35支肺外体循环动脉扩张迂曲进入肺内。5例支气管扩张和1例肺癌中扩张迂曲的支气管动脉与肺外体循环动脉形成明显的交通吻合成网状,7例支气管扩张中支气管动脉、肺外体循环动脉与肺动脉间形成吻合。除1例肺隔离症没有伴明显胸膜增厚外,其余肺外体循环动脉穿过胸壁进入肺内均伴有明显的胸膜增厚。结论:CTA并三维重建技术能清晰显示支气管动脉肺外体循环动脉的起源、分布等解剖特征,为介入术提供明确路径,有利于疾病的诊断与治疗。     

Systemic collateral supply in patients with chronic thromboembolic and primary pulmonary hypertension: assessment with multi-detector row helical CT angiography

PURPOSE: To compare retrospectively the frequency of systemic collateral supply in patients who have chronic thromboembolic pulmonary hypertension with the frequency of systemic collateral supply in patients who have primary pulmonary hypertension by using multi-detector row helical computed tomographic (CT) angiography. MATERIALS AND METHODS: For this review, neither institutional board approval nor informed consent was required. Thirty-six consecutive patients, including 22 patients (four men, 18 women; mean age, 46.0 years) with chronic thromboembolic pulmonary hypertension (group 1) and 14 patients (five men, nine women; mean age, 63.0 years) with primary pulmonary hypertension (group 2), underwent multisection spiral CT angiography of the pulmonary and systemic circulations with a four- (n = 17) or 16- (n = 19) detector row scanner. CT angiograms were assessed for the presence of abnormal bronchial and/or nonbronchial systemic arteries, CT features of pulmonary hypertension, and right ventricular dysfunction. Vascular and parenchymal signs of chronic pulmonary embolism were specifically analyzed on CT angiograms of group 1 patients. Comparative analyses were performed by using the chi(2) or the Fisher exact test for categoric data. An unpaired bilateral Wilcoxon rank sum test was used for continuous data. A chi(2) goodness-of-fit test was used to compare observed proportions with equal proportions. RESULTS: The degree of pulmonary hypertension was comparable in groups 1 and 2. Abnormally enlarged systemic arteries were identified in 16 (73%) of 22 patients from group 1 and in two (14%) of 14 patients from group 2 (P = .002). The systemic collateral supply in group 1 comprised enlargement of both bronchial and nonbronchial systemic arteries in nine (56%) of the 16 patients; the remaining seven patients had an exclusive enlargement of bronchial systemic arteries (n = 6, 38%) or nonbronchial (n = 1, 6%) systemic arteries. A total of 31 enlarged nonbronchial systemic arteries were depicted, including 13 inferior phrenic arteries, 10 intercostal arteries, seven internal mammary arteries, and one lateral thoracic artery. The mean +/- standard deviation of abnormal nonbronchial systemic arteries per patient was 1.4 +/- 1.9. No relationship was found between the mean number of abnormally enlarged nonbronchial systemic arteries and the CT angiographic features of chronic pulmonary embolism. CONCLUSION: These results demonstrate the higher frequency of abnormally enlarged bronchial and nonbronchial systemic arteries in patients who have chronic thromboembolic pulmonary hypertension compared with patients who have primary pulmonary hypertension; this finding could help distinguish these two entities on CT angiograms.     

Revealing hepatic metastases from colorectal cancer: value of combined helical CT during arterial portography and CT hepatic arteriography with a unified CT and angiography system

OBJECTIVE: The purpose of our study was to evaluate the use of combined helical CT during arterial portography and CT hepatic arteriography in the preoperative assessment of hepatic metastases from colorectal cancer using a unified CT and angiography system. MATERIALS AND METHODS: Fifty-four patients with hepatic metastases from colorectal cancer preoperatively underwent combined CT during arterial portography and CT hepatic arteriography using the unified CT and angiography system. Three radiologists independently and retrospectively reviewed the images of CT during arterial portography alone, CT hepatic arteriography alone, and combined CT during arterial portography and CT hepatic arteriography. Image review was conducted on a segment-by-segment basis; a total of 432 hepatic segments with (n = 103) 118 metastatic tumors ranging in size from 2 to 160 mm (mean, 25.8 mm) and without (n = 329) tumor were reviewed. RESULTS: Relative sensitivity of combined CT during arterial portography and CT hepatic arteriography (87%) was higher than that of CT during arterial portography alone (80%, p < 0.0005) and CT hepatic arteriography alone (83%, p < 0.005). Relative specificity of CT hepatic arteriography alone (95%, p < 0.0005) and combined CT during arterial portography and CT hepatic arteriography (96%, p < 0.0001) was higher than that of CT during arterial portography alone (91%). Diagnostic accuracy, determined by a receiver operating characteristic curve analysis, was greater with combined CT during arterial portography and CT hepatic arteriography than with CT during arterial portography alone (p < 0.05) or CT hepatic arteriography alone (p < 0.01). CONCLUSION: Using a unified CT and angiography system, we found that combined CT during arterial portography and CT hepatic arteriography significantly raised the detectability of hepatic metastases from colorectal cancer.     

Anomalous systemic arterial supply to normal basal segments of left lower lobe: characteristic imaging findings

PURPOSE: The purpose of this study was to describe the characteristic findings in each imaging modality of anomalous systemic arterial supply to normal basal segments of the left lower lobe of the lung. METHOD: Five patients with anomalous systemic arterial supply to normal basal segments of the left lower lobe were retrospectively reviewed. Chest radiography, contrast-enhanced CT scan, angiography, and other imaging modalities were analyzed. RESULTS: The imaging findings of this anomaly were characterized by three issues as follows: an anomalous systemic artery arising from the thoracic aorta, absence of pulmonary arterial supply, and normal bronchial system as well as normal pulmonary parenchyma in the affected segments. The anomalous systemic artery was demonstrated on chest radiography, contrast-enhanced CT scan, MRI, and thoracic aortography. Absence of pulmonary arterial supply was revealed by pulmonary angiography, radiolabeled perfusion scan, and CT scan. Normal bronchial system was confirmed by radiolabeled ventilation scan, bronchography, and CT scan. CONCLUSION: CT is useful in making the correct diagnosis of this anomaly because it is the only diagnostic method that can demonstrate the anomalous systemic artery, absence of pulmonary arterial supply, and normal bronchial system in the affected segments.     

Central pulmonary thromboembolism: diagnosis with spiral volumetric CT with the single-breath-hold technique--comparison with pulmonary angiography.

Forty-two patients were prospectively evaluated with spiral volumetric computed tomography (CT) and selective pulmonary angiography of each lung to detect central pulmonary thromboembolism. Spiral volumetric CT images obtained with either 90 mL of 30% contrast material or 120 mL of 12% contrast material were graded as excellent or good in 98% of the examinations (41 patients). Diagnosis of pulmonary embolism with spiral volumetric CT was based on the direct visualization of intraluminal clots: partial filling defects (n = 41; 37%), complete filling defects (n = 51; 46%), "railway track" signs (n = 6; 5%), and mural defects (n = 14; 12%). All 23 patients with normal findings of spiral volumetric CT had normal findings of pulmonary angiography. With spiral volumetric CT, the finding of 112 central emboli (eight main, 28 lobar, and 76 segmental) corresponded exactly to the angiographic findings, but nine intersegmental lymph nodes were erroneously interpreted as filling defects. In one case of normal pulmonary angiographic findings, asymmetry in pulmonary arterial perfusion was misinterpreted as pulmonary embolism with spiral volumetric CT. Spiral volumetric CT can reliably depict thromboemboli in second- to fourth-division pulmonary vessels.