Acute pulmonary embolism: imaging in the emergency department

Acute pulmonary embolism (PE) is a life-threatening condition that requires accurate diagnostic imaging. Morbidity and mortality that result from PE can be reduced significantly if appropriate treatment is initiated early; this makes timely diagnosis imperative. Historically, the gold standard for the imaging of PE has been pulmonary angiography. Rapid advances in radiology and nuclear medicine have led to this modality largely being replaced by noninvasive techniques, most frequently multidetector helical CT pulmonary angiography (CTPA). In cases in which CTPA is contraindicated, other modalities for diagnosis of PE include nuclear ventilation perfusion scanning, magnetic resonance pulmonary angiography, duplex Doppler ultrasonography for deep venous thrombosis, and echocardiography. This article reviews the literature on the role of these imaging modalities in the diagnosis of PE.     

Acute and subacute dual energy CT findings of pulmonary embolism in rabbits: correlation with histopathology

Objective

The purpose of this study was to describe quantitative dual energy CT (DECT) findings and their accuracy in the detection of acute and subacute pulmonary embolism (PE) in rabbits.

Methods

Pulmonary emboli were created in 24 rabbits by gelatin sponge femoral vein injection. Conventional CT pulmonary angiography (CTPA) and DECT were obtained at either 2 h, 1 day, 3 days or 7 days after embolisation (n=6 rabbits for each time point). The location and number of PEs in the different stages were recorded at CTPA and iodine maps from DECT on a per-lobe basis. With histopathology as the reference standard, sensitivity and specificity of CTPA and DECT were calculated. CT and iodine map overlay values of the embolic and non-embolic areas were measured for each scan.

Results

With histopathology as the reference standard, the overall sensitivity and specificity of CTPA were 98% and 100% and those of iodine maps were 100% and 95%, respectively. Conventional CT and iodine map values of the embolised and non-embolised areas were significantly different between 2 h and 1 day (p<0.001), but not between 3 days and 7 days (p>0.05). A statistical difference was found for overlay values measured in the embolic and non-embolic regions for four groups.

Conclusion

Iodine maps derived from DECT show alterations in lung perfusion for acute and subacute PE in an experimental rabbit model and show comparable sensitivity for PE detection and conventional CTPAIn the USA, more than 650 000 cases of pulmonary embolism (PE) occur each year, resulting in as many as 300 000 annual fatalities [1,2]. Despite the high morbidity, the diagnosis of PE may be delayed in the absence of typical clinical symptoms or when emboli are subsegmental and such scenarios may delay the treatment and increase the mortality of PE. Imaging plays an important role in the diagnosis and follow-up of PE. With improvements in multidetector row CT, CT pulmonary angiography (CTPA) has largely replaced digital subtraction angiography (DSA) for the diagnosis and follow-up of PE and has been recommended as the reference of standard for diagnosis of acute PE [3]. However, CTPA has shortcomings, such as a limited sensitivity to detect peripheral or subsubsegmental emboli of the pulmonary artery and an inability to show lung perfusion impairment resulting from acute or chronic PE.With the development of dual source CT (DSCT), in which two orthogonally mounted detectors and tubes arrays operate simultaneously and can be set to different tube potentials to allow for dual energy CT (DECT) acquisitions with minimal patient motion registration artefact, DECT imaging has been used to investigate iodine distribution maps in clinical and pre-clinical studies [4-13]. Such iodine maps, which have been termed blood flow imaging (BFI), have been shown to be valuable supplements to conventional anatomic CTPA for the evaluation of distal pulmonary artery emboli [4-13]. Many studies have focused on the feasibility or diagnostic accuracy of DECT iodine maps to improve the detection of PE, with CTPA, scintigraphy or histopathology as a reference standard in the clinical and experimental studies [5-13], or the evaluation of image quality of dual energy CTPA [14,15]. However, to the best of our knowledge, there are no reports that describe the evolution of CT and DECT imaging findings of PE over time after an embolic event with histopathological correlation. Histopathology correlation is most ethically obtained using an animal model. Therefore, we evaluated DECT findings with histopathology correlation in a rabbit model of PE with different time delays after embolisation and assessed the diagnostic accuracy of DECT in the detection of PE at these different time points.     

CT pulmonary angiography in the detection of pulmonary emboli: a meta-analysis of sensitivities and specificities

OBJECTIVE: To determine the overall sensitivity and specificity for CT pulmonary angiography (CTPA) in the diagnosis of pulmonary emboli (PE) using a meta-analysis of the published literature. MATERIALS AND METHODS: A Medline search was constructed to include all English language publications indexed in the Index Medicus from 1990 to 2000, which included the terms CT, PE and pulmonary angiography. Studies selected were designed principally to compare CTPA in the overall detection of PE as confirmed by an abnormal fluoroscopic pulmonary angiogram or a high probability V:Q scan. Results were corrected for the patient sample size in the respective studies prior to pooling the data. In the absence of an accepted technique for calculating a ROC curve in the meta-analysis of imaging studies, a previously untested theoretical technique was used to obtain a composite ROC curve. RESULTS: Twelve studies of CTPA comprising a total of 1250 patients were analyzed. The overall sensitivity and specificity for CTPA after correction for study size was 74.1% and 89.5% with a range of 57-100% and 68-100%, respectively, for the detection of PE. No trend was detected with respect to the year of publication or sample size. CONCLUSIONS: CTPA has acceptable sensitivity and specificity with a strong ROC curve making it a good first line investigation for PE.     

低剂量对比剂双能量肺灌注成像评估肺动脉内血栓与灌注缺损间的关系

目的:应用双源CT低剂量对比剂双能量肺灌注成像评估急性肺动脉栓塞患者血管内血栓与肺灌注缺损间的关系,以提高对肺动脉栓塞诊断的准确性。方法:随机选择无肺动脉栓塞患者的低剂量与常规剂量双能量肺灌注成像各15例,对比分析其图像质量;收集20例疑肺动脉栓塞患者行低剂量双能量肺灌注成像;同时获得肺动脉CTA及肺灌注图像。分析肺动脉内有无血栓,以及血栓的部位、数量及形态特征。用双能量肺灌注分析软件判断有无灌注缺损及缺损的部位、形态及范围。对比分析并统计肺动脉内血栓与肺灌注缺损间的关系。结果:肺动脉栓塞患者的低剂量与常规剂量双能量肺灌注成像质量无明显差异(P>0.05)。20例疑似病例中,15例诊断为肺动脉栓塞,其中13例患者肺灌注图像中出现102个肺叶、肺段、或亚段灌注缺损,4例共6个灌注缺损CTA无明确血栓;11例肺动脉CTA显示43个血栓,其中9例血栓与灌注缺损同时存在,2例CTA共5个血栓肺内无灌注缺损。75个灌注缺损与栓塞肺动脉供血范围一致,21个灌注缺损(8段、13亚段)与肺动脉供血范围无关。结论:综合分析双源CT低剂量双能量肺灌注图与CTPA,可以提高肺动脉栓塞诊断的准确性。     

Dual Energy CT lung perfusion imaging--correlation with SPECT/CT

Objective

Aims were (1) to determine the diagnostic accuracy of Dual Energy CT (DECT) in the detection of perfusion defects and (2) to evaluate the potential of DECT to improve the sensitivity for PE.

Methods

15 patients underwent Dual Energy pulmonary CT angiography (DE CTPA) and a combination of lung perfusion SPECT/CT and ventilation scintigraphy. CTPA and DE iodine distribution maps as well as perfusion SPECT/CT and inhalation scintigrams were reviewed for pulmonary embolism (PE) diagnosis. DECT and SPECT perfusion images were assessed regarding localization and extent of perfusion defects. Diagnostic accuracy of DE iodine (perfusion) maps was determined with reference to SPECT/CT. Diagnostic accuracies for PE detection of DECT and of SPECT/CT with ventilation scintigraphy were calculated with reference to the consensus reading of all modalities.

Results

DE CTPA had a sensitivity/specificity of 100%/100% for acute PE, while the combination of SPECT/CT and ventilation scintigraphy had a sensitivity/specificity of 85.7%/87.5%. For perfusion defects, DECT iodine maps had a sensitivity/specificity of 76.7% and 98.2%.

Conclusion

DECT is able to identify pulmonary perfusion defects with good accuracy. This technique may potentially enhance the diagnostic accuracy in the assessment of PE.     

CT pulmonary angiography is the first-line imaging test for acute pulmonary embolism: a survey of US clinicians

RATIONALE AND OBJECTIVES: Our aim is to document current imaging practices for diagnosing acute pulmonary embolism (PE) among physicians practicing in the United States and explore factors associated with these practices. MATERIALS AND METHODS: Between September 2004 and February 2005, we surveyed by mail 855 physicians selected at random from membership lists of three professional organizations. Physicians reported their imaging practices and experiences in managing patients with suspected acute PE during the preceding 12 months. RESULTS: Completed questionnaires were received from 240 of 806 eligible participants (29.8%) practicing in 44 states: 86.7% of respondents believed that computed tomographic pulmonary angiography (CTPA) was the most useful imaging procedure for patients with acute PE compared with 8.3% for ventilation-perfusion (V-P) scintigraphy and 2.5% for conventional pulminary angiography (PA). After chest radiography, CTPA was the first imaging test requested 71.4% of the time compared with V-P scintigraphy (19.7%) and lower-limb venous ultrasound (5.8%). Participants received indeterminate or inconclusive results 46.4% of the time for V-P scintigraphy, 10.6% of the time for CTPA, and 2.2% of the time for PA. CTPA was available around the clock to 88.3% of participants compared with 53.8% for V-P scintigraphy and 42.5% for PA. A total of 68.6% of respondents received CTPA results in 2 hours or less (vs 37.5% for V-P scintigraphy and 22.9% for PA). CTPA also provided an alternative diagnosis to PE or showed other significant abnormalities 28.5% of the time, and these findings frequently altered management. CONCLUSION: US clinicians unequivocally prefer CTPA in patients with suspected acute PE. Reasons for this preference include availability and timely reporting, a lower rate of inconclusive results, and the additional diagnostic capabilities that CTPA can provide.     

CTPA对肺动脉栓塞的诊断及临床应用价值

目的:探讨多层螺旋CTPA及后处理技术对肺动脉栓塞的诊断及临床应用价值。方法:回顾性分析40例经多层螺旋CTPA确诊为肺动脉栓塞的影像资料,并应用MPR、MIP、VR等后处理方法不同角度显示肺动脉及其栓子情况,观察肺动脉栓塞的征象,10例经临床治疗后行CTPA复查并与临床结果对照指导治疗。结果:40例肺动脉栓塞(PE)病例中,中央型PE32例,周围型PE8例。肺动脉内栓子表现为中心型、偏心型及闭塞型的充盈缺损。经治疗复查CTPA显示栓子变小或消失。结论:MSCTPA已成为诊断肺动脉栓塞的可靠方法,并为肺动脉栓塞的治疗提供必要的指导。     

双源CT双能量肺灌注成像诊断急性肺栓塞的实验研究

目的 评价双源CT(DSCT)双能量肺灌注成像(DEPI)的可行件及其诊断急性实验性肺栓塞的价值.方法 对8只新两兰白兔制备成急性肺栓塞模型的前、后行DSCT平妇及双能量增强扣描,并进行数据后处理,分别得到CT解剖图像(CTPA)、DEPI及两者融合图像,观察肺动脉内有无栓子,分析栓塞前、后的肺灌注影像表现;进行家兔肺大体病理解剖和镜下观察.计算CTPA、DEPI及融合图像的诊断敏感度、特异度、阳性预测值(PPV)、阴性预测值(NPV).应用Kappa系数评价两种检查结果的一致性.结果 7只兔模型制作成功,1只因肺内导管头影响图像评价而排除;6只兔30个肺时数据可用于分析.病理共发现18个肺叶栓塞阳件,12个阴性.与正常肺组织相比,肺柃塞区域DEPI表现为灌注不良或缺损,CTPA表现为相应肺动脉中断或充盈缺损.CTPA诊断的敏感度、特异度、PPV、NPV分别为66.7%(12/18)、100.0%(12/12)、100.0%(12/12)、66.7%(12/18),与病理结果吻合度一般(Kappa=0.651);DEPI诊断的敏感度、特异度、PPV、NPV分别为88.9%(16/18)、91.7%(11/12)、94.1%(16/17)、84.6%(11/13),与病理结果吻合度较强(Kappa=0.795).融合图像结果与DEPI一致.结论 DSCT的DEPI能够反映兔肺部『『fL流分布情况,对肺栓塞的诊断有较高的敏感度,并与病理结果有较强的一致性.     

CT肺动脉造影与MR肺动脉成像在肺栓塞评估中的准确性比较

目的 探讨CT肺动脉造影与磁共振肺动脉成像在肺栓塞(pulmonary embolism,PE)临床评估中的准确性.方法 选取28只成年健康长毛兔制作PE模型,均行磁共振肺动脉成像(magnetic resonancepulmon aryangiography,MR-PA)及CT肺动脉造影(computed tomog...     

V/Q SPECT and computed tomographic pulmonary angiography

Planar ventilation and perfusion (V/Q) scintigraphy has been largely displaced by computed tomography pulmonary angiography (CTPA) in recent years for the diagnosis of pulmonary embolism (PE). This change can be attributed to multiple studies that demonstrate CTPA has a reasonable sensitivity and good prognostic value in negative cases, associated with the ability to deliver few indeterminate results and provide an alternate diagnosis in a significant number of patients. However, the technique has significant limitations. The Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) study has shown a sensitivity of 83%, which is not optimal. However, CT technology has greatly progressed since this time, and therefore it is likely that this number has improved. The PIOPED II study has also shown that there may be a problem in positive or negative predictive value when the imaging results are discordant with the clinical probability. Additional concerns include allergies, contrast nephropathy associated with the use of intravenous contrast in patients with impaired creatinine clearance, suboptimal results in pregnant women, and high radiation exposure. In recent years, V/Q single-photon emission computed tomography has emerged as a mature technique for the diagnosis of PE and has been shown to be clearly superior to planar V/Q. The technique has excellent sensitivity for PE and is not associated with most of the limitations of CTPA, although it has its own set of limitations in patients with very severe chronic obstructive pulmonary disease or with a severely abnormal chest x-ray. V/Q single-photon emission computed tomography can be used as the initial modality for PE diagnosis in a wide variety of situations although CTPA remains invaluable in specific scenarios.     

双源 CT 肺栓塞探测软件及能量灌注成像对外周型肺栓塞的诊断价值

目的：探索双源 CT 后处理软件在外周型肺栓塞诊断中的价值。方法对150例可疑肺栓塞患者进行扫描,20例患者符合标准。扫描数据采用肺栓塞分析软件(PED)、双能量肺灌注成像(DEPI)及肺动脉成像(CTPA)对图像重建,分别由2名高年资血管专业诊断医师对 PED 图、DEPI 图及 CTPA 图进行分析,根据诊断标准,分别记录由 PED 图、CTPA 图诊断的肺段及亚段动脉肺栓子位置、数目,计算显示率并评价其统计学差异;同时评价 PED 图与 DEPI 图对肺段动脉肺栓塞诊断一致性。结果 CTPA图共发现30处段动脉及40处亚段动脉内存在血栓,其检出率为7.50%及5.00%,PED 图共发现48处段动脉及62处亚段动脉内存在血栓,其检出率为12.00%及7.75%,CTPA 图与 PED 图存在显著的统计学差异(χ2=4.60、5.06,P <0.05)。以 PED 图诊断结果为参考标准,Kappa 系数=0.94,一致性极好。在 PED 图发现48处段动脉肺栓塞中,13处完全性栓塞,DEPI 图显示10例出现灌注缺损,3例出现灌注稀疏;35处不完全性肺栓塞,2例灌注缺损,29例出现灌注稀疏,4例无明显灌注改变。结论双源 CT肺栓塞探测软件联合能量灌注成像能够明显提高外周型肺栓塞的诊断率,具有较高的实用性及临床价值。     

Low yield of ventilation and perfusion imaging for the evaluation of pulmonary embolism after indeterminate CT pulmonary angiography

Purpose

Ventilation and perfusion (VQ) imaging is common following suboptimal CT pulmonary angiogram (CTPA) for pulmonary embolism (PE) evaluation; however, the results of this diagnostic pathway are unclear. The purpose of our study is to determine the incidence of PE diagnosed on VQ scans performed in patients with suboptimal CTPAs.

Methods

One hundred twenty-two suboptimal CTPAs with subsequent VQ scans within 1 week were retrospectively identified. VQ reports utilizing modified ?prospective investigation of pulmonary embolism diagnosis (PIOPED) and prospective investigative study of acute pulmonary embolism diagnosis (PISAPED) criteria were evaluated for presence of PE; intermediate probability, high probability, and PE present were considered PE positive. Three hundred consecutive reports of each diagnostic CTPA and diagnostic VQ studies were reviewed to estimate baseline PE positive rates at our institution. These were compared to the positive VQ scan rate after suboptimal CTPA by Fisher’s exact test. Reported reason for suboptimal CTPA was noted. When contrast bolus timing was suboptimal, we measured main pulmonary artery (mPA) Hounsfield units (HU). Potential alternative diagnoses in CTPA reports were noted.

Results

97.5% (119/122) of VQ scans following suboptimal CTPA were negative for PE, and 2.5% (3/122) were positive for PE. This was significantly lower than baseline PE positive rate of 10.7% (32/300, p < 0.01) for VQ imaging, and 10.3% (31/300, p < 0.01) for CTPA at our institution. Most (79.5%) CTPAs were suboptimal due to contrast timing. Average mPA density in these cases was 164 ± 61 HU. Most of these studies ruled out central PE. Potential alternative diagnosis was reported in 34/122 (28%) of suboptimal CTPAs, for which pneumonia accounted 59%.

Conclusion

There is very low incidence of PE diagnosed on VQ imaging performed after suboptimal CTPA. This may be attributed to the ability of most suboptimal CTPAs to rule out central PE.

     

64层CT肺动脉造影对肺栓塞诊断及治疗后复查的应用研究

目的:探讨64层CT肺动脉造影(CTPA)对肺栓塞的诊断效果及治疗后复查的价值。方法:对32例肺动脉栓塞的患者采用64层CT行CTPA检查,并进行多平面重建(MPR)、最大密度投影及容积重建处理。患者复查采用相同CT检查及后处理重建。结果:32例患者中15例有下肢静脉栓塞、4例有恶性肿瘤、3例有近期手术病史,2例有近期外伤史。CTPA对肺动脉主干、左右肺动脉及叶、段、亚段动脉显示良好,32例患者中显示受累肺动脉221支,其直接征象为肺动脉血管内充盈缺损,间接征象包括肺梗死实变、肺野少血征、胸腔积液等。肺栓塞治疗后复查有24例患者1月内肺动脉栓子消失或明显吸收缩小(占75%);6例患者吸收不明显(占18.7%);2例死亡。结论:64层CT能清楚地显示肺栓塞的形态、部位及其它间接征象,并能有效监测治疗效果,为临床提供有益帮助。     

The use of a D-dimer assay in patients undergoing CT pulmonary angiography for suspected pulmonary embolus.

PURPOSE: To assess the ability of a semi-quantitative latex agglutination D-dimer test Accuclot with bedside measurements of arterial oxygen saturation, respiratory and cardiac rates to exclude pulmonary embolism (PE) on computed tomographic pulmonary angiography (CTPA). MATERIALS AND METHODS: All patients referred to our CT unit for investigation of suspected acute pulmonary embolism were enrolled. Pulse oximetery, respiratory rate, heart rate and blood sampling for D-dimer testing were carried out just before CT. A high resolution CT (HRCT) of the chest was followed by a CT pulmonary angiogram (CTPA). The images were independently interpreted at a workstation with cine-paging and 2D reformation facilities by three consultant radiologists blinded to the clinical and laboratory data. If positive, the level of the most proximal embolus was recorded. Discordant imaging results were re-read collectively and consensus achieved. RESULTS: A total of 101 patients were enrolled. The CTPA was positive for PE in 28/101 (28%). The D-dimer was positive in 65/101 (65%). Twenty-six patients had a positive CT and positive D-dimer, two a positive CT but negative D-dimer, 39 a negative CT and positive D-dimer, and 34 a negative CT and negative D-dimer. The negative predictive value of the Accuclot D-dimer test for excluding a pulmonary embolus on spiral CT was 0.94. Combining the D-dimer result with pulse oximetry (normal SaO2 > or = 90%) improved the negative predictive value to 0.97. CONCLUSION: A negative Accuclot D-dimer assay proved highly predictive for a negative CT pulmonary angiogram in suspected acute pulmonary embolus. If this D-dimer assay were included in the diagnostic algorithm of these patients a negative D-dimer would have unnecessary CTPA rendered in 36% of patients.     

Fetal radiation dose from CT pulmonary angiography in late pregnancy: a phantom study

Pulmonary embolism (PE) is the leading direct cause of maternal mortality in the UK. Accurate diagnosis is important but, even though CT pulmonary angiography (CTPA) is the recommended imaging modality for PE in the general population, there is limited guidance for pregnant patients. Knowledge of the radiation doses to both the mother and the fetus is therefore important in the justification of CTPA in this situation. Dose measurements were made on three helical CT scanners, with an anthropomorphic phantom representing the chest and abdomen in late gestation. Estimated fetal doses from CT scans of the maternal chest were in the range of 60-230 microGy. Fetal dose reduction strategies (mA modulation, shielding with a lead coat, and a 5 cm shorter scan length) were investigated. These reduced the fetal dose by 10%, 35% and 56%, respectively. Fetal doses from a scan projection radiograph (SPR) of the maternal chest were insignificant when compared with the dose from a CT scan. However, if the SPR was not stopped before the "fetus" was directly irradiated, the dose measured on one scanner was 20 microGy.     

Imaging of acute pulmonary embolism using a dual energy CT system with rapid kVp switching: Initial results

Purpose

Computed tomography pulmonary angiography (CTPA) is considered as clinical gold standard for diagnosing pulmonary embolism (PE). Whereas conventional CTPA only offers anatomic information, dual energy CT (DECT) provides functional information on blood volume as surrogate of perfusion by assessing the pulmonary iodine distribution. The purpose of this study was to evaluate the feasibility of lung perfusion imaging using a single-tube DECT scanner with rapid kVp switching.

Materials and methods

Fourteen patients with suspicion of acute PE underwent DECT. Two experienced radiologists assessed the CTPA images and lung perfusion maps regarding the presence of PE. The image quality was rated using a semi-quantitative 5-point scale: 1 (=excellent) to 5 (=non-diagnostic). Iodine concentrations were quantified by a ROI analysis.

Results

Seventy perfusion defects were identified in 266 lung segments: 13 (19%) were rated as consistent with PE. Five patients had signs of PE at CTPA. All patients with occlusive clots were correctly identified by DECT perfusion maps. On a per patient basis the sensitivity and specificity were 80.0% and 88.9%, respectively, while on a per segment basis it was 40.0% and 97.6%, respectively. None of the patients with a homogeneous perfusion map had an abnormal CTPA. The overall image quality of the perfusion maps was rated with a mean score of 2.6 ± 0.6. There was a significant ventrodorsal gradient of the median iodine concentrations (1.1 mg/cm³ vs. 1.7 mg/cm³).

Conclusion

Lung perfusion imaging on a DE CT-system with fast kVp-switching is feasible. DECT might be a helpful adjunct to assess the clinical severity of PE.     

Pulmonary artery CTA

The latest with the introduction of multidetector row computed tomography (MDCT), CT has been firmly established as the modality of choice for imaging the pulmonary arteries, particularly as the de facto first line test for imaging patients with suspected acute pulmonary embolism (PE). Before the introduction of MDCT, remaining concerns regarding CTs accuracy for diagnosis of isolated peripheral emboli had prevented the unanimous acceptance of this test as the reference standard for imaging PE. After a decade of uncertainty, there is now conclusive evidence that CT, if positive, provides reliable confirmation of the presence of PE and, more importantly, if negative effectively rules out clinically significant PE. Current endeavors to streamline and facilitate workflow for CT diagnosis of PE will further improve the acceptance, utility, and importance of this test. Examples include improvements in workflow, CT derivation of right ventricular function parameters for triage and prognostication of patients with acute PE and the comprehensive assessment of patients with acute chest pain for PE, coronary disease, aortic disease, and pulmonary disease by means of a single, contrast enhanced, ECG-synchronized CT scan. Although the diagnosis or exclusion of acute PE is the most common and important application of CT pulmonary angiography, the ease of scan acquisition and the high spatial resolution of modern CT techniques make this test ideally suited for the greatest majority of congenital and acquired, acute and chronic disorders of the pulmonary arteries.     

闭塞性与非闭塞性肺栓塞双源CT双能量肺灌注成像的初步研究

目的:探讨急性肺栓塞(PE)患者双源CT肺动脉成像(CTPA)显示的闭塞性与非闭塞性栓子在双源CT双能量肺灌注成像(DEPI)的视觉分析法及半定量分析的初步研究.方法:搜集本院2015年6月-2017年1月经CTPA及DEPI扫描确诊的31例急性PE患者的病例资料.分析CTPA,记录PE栓子的数量、分布部位及栓塞类型.分析DEPI,分别计算每个栓子栓塞区与对照区肺组织灌注CT值的差值(△CT值).结果:将CTPA所示栓子按其分布部位及栓塞程度分为四型:中央型闭塞型、中央型非闭塞型、周围型闭塞型、周围型非闭塞型.DEPI视觉分析法:闭塞型组中,表现为灌注减低、灌注轻度减低、灌注不变的比例为78.57％(99/126)、21.43％(27/126)、0.00％(0/126).非闭塞组中,其比例分别为19.70％(26/132)、34.09％(45/132)、46.21％(61/132).中央型闭塞型、中央型非闭塞型、周围型闭塞型、周围型非闭塞型视觉阳性率分别为100.00％(85/85)、66.11％(66/108)、100.00％(41/41)、20.83％(5/24).DEPI半定量分析:闭塞型与非闭塞型间差异具有统计学意义[(64.59±12.10)HUvs (33.12±9.72)HU,t=22.968,P＜0.01];中央型闭塞型与中央型非闭塞型、周围型闭塞型与周围型非闭塞型间差异均具有统计学意义[分别为(70.12±13.55)HU vs(36.23±7.87)HU,t=20.506,P＜0.01;(53.12±14.64)HUvs(19.12±5.77)HU,t=13.220,P＜0.01].结论:闭塞型栓子往往引起灌注异常,而非闭塞型栓予,受多种因素影响,DEPI呈现多样化.双源CTPA联合DEPI视觉分析及半定量分析能够对PE治疗前评估提供更加全面、客观的依据.     

Utilization patterns and diagnostic yield of 3421 consecutive multidetector row computed tomography pulmonary angiograms in a busy emergency department

OBJECTIVE: To compare examination volume and diagnostic yield of computed tomography (CT) pulmonary angiography (CTPA) and ventilation-perfusion (V/Q) scintigraphy for detection of suspected pulmonary embolism (PE) in emergency department patients. METHODS: Every CTPA and V/Q scan result for emergency department patients between October 2001 and September 2005 were reviewed. Patients with prior PE and follow-up examinations were excluded. RESULTS: A total of 3421 CTPA examinations and 198 V/Q scans met inclusion criteria. Average CTPA examinations completed per month increased 227%, from 33.4 to 109.2 for the first and last 24-month periods, respectively. Ventilation-perfusion scintigraphy volume decreased 80% (from 6.9 to 1.4 per month). Total diagnoses of PE per month increased 89% from 4.0 to 7.5, whereas the percentage of positive CTPA examinations dropped from 9.8% to 6.8%. CONCLUSIONS: Availability of CT in the emergency department and lower physician thresholds for test utilization have increased the use of CT pulmonary angiography and increased detection of PE.     

Computed tomography pulmonary angiogram diagnosis of pulmonary embolism

Over the last decade, contrast-enhanced spiral CT has been established as a non-invasive alternative to catheter angiography and is now regarded as the first-line imaging investigation for the diagnosis of pulmonary embolism (PE). The reported sensitivities for the diagnosis of PE of spiral CT vary from 45 to 100% and the specificities vary from 78 to 100%. Prospective outcome studies have shown a high negative predictive value for a single-detector spiral CT for PE. Patients' outcomes were not adversely affected in these studies when anticoagulation was withheld after a negative CT pulmonary angiogram. The main limitation of single-detector spiral CT has been its limited ability to detect isolated subsegmental PE. However, multidetector spiral CT allows evaluation of pulmonary vessels down to sixth-order branches and significantly increases the rate of detection of PE in segmental and subsegmental levels. The interobserver correlations for diagnosis of subsegmental PE with multidetector spiral CT exceed the reproducibility of selective pulmonary angiography. If appropriate equipment is available (multidetector CT), then CT pulmonary angiogram is safe to be used as the first-line imaging investigation for the diagnosis of PE.