Pulmonary circulation

Evaluation of the pulmonary vasculature is mainly indicated in patients with suspected pulmonary thromboembolism. The routine procedure so far is ventilation-perfusion scintigraphy alone or in combination with diagnostic assessment of the legs to rule out deep venous thrombosis. The results are still not reliable for the majority of patients. In the case of equivocal diagnosis, invasive conventional angiography is considered the gold standard. With steady improvements in tomographic imaging techniques, such as computed tomography (CT) or magnetic resonance imaging (MRI), non-invasive alternatives to the routine diagnostic work-up are given. Helical CT and CTA techniques are already in clinical use and estimated to sufficiently serve the demands for detection/exclusion of pulmonary thromboembolism. The disadvantages mainly concern peripheral disease and reconstruction artifacts. MRI and MR angiography have been implemented in the diagnosis of pulmonary vascular disease since the introduction of contrast-enhanced MRA. In breath-hold techniques, the entire lung vascularization can be delineated and thromboemboli can be detected. The clinical experience in this field is limited, but MRI has the potential to demonstrate its superiority over CT due to its improved delineation of the vascular periphery and the more comprehensive three-dimensional reconstruction. Received: 20 January 1998; Accepted: 10 February 1998     

Venous thromboembolism: additional diagnostic value and radiation dose of pelvic CT venography in patients with suspected pulmonary embolism

Purpose

To assess the additional diagnostic value of indirect CT venography (CTV) of the pelvis and upper thighs performed after pulmonary CT angiography (CTA) for the diagnosis of venous thromboembolism (VTE).

Materials and methods

In a retrospective analysis, the radiology information system entries between January 2003 and December 2007 were searched for patients who received pulmonary CTA and additional CTV of the pelvis and upper thighs. Of those patients, the radiology reports were reviewed for the diagnosis of pulmonary embolism (PE) and deep venous thrombosis (DVT) in the pelvic veins and veins of the upper thighs. In cases with an isolated pelvic thrombosis at CTV (i.e. which only had a thrombosis in the pelvic veins but not in the veins of the upper thigh) ultrasound reports were reviewed for the presence of DVT of the legs. The estimated radiation dose was calculated for pulmonary CTA and for CTV of the pelvis.

Results

In the defined period 3670 patients were referred to our institution for exclusion of PE. Of those, 642 patients (353 men, 289 women; mean age, 65 ± 15 years, age range 18–98 years) underwent combined pulmonary CTA and CTV. Among them, PE was found in 227 patients (35.4%). In patients without PE CTV was negative in all cases. In patients with PE, CTV demonstrated pelvic thrombosis in 24 patients (3.7%) and thrombosis of the upper thighs in 43 patients (6.6%). Of those patients 14 (2.1%) had DVT in the pelvis and upper thighs. In 10 patients (1.5%) CTV showed an isolated pelvic thrombosis. Of those patients ultrasound reports were available in 7 patients, which revealed DVT of the leg veins in 5 cases (1%). Thus, the estimated prevalence of isolated pelvic thrombosis detected only by pelvic CTV ranges between 1–5/642 patients (0.1–0.7%). Radiation dose ranges between 4.8 and 9.7 mSv for additional CTV of the pelvis.

Conclusion

CTV of the pelvis performed after pulmonary CTA is of neglectable additional diagnostic value for the detection of VTE, because the additional radiation dose is high and isolated pelvic DVT is very rare. Venous imaging of the legs (preferably by radiation-free ultrasound) is sufficient for the diagnosis of underlying DVT in patients with suspected PE.     

Equipment availability and diagnostic strategies for suspected pulmonary embolism in Austria

The aim of this study was to investigate equipment availability and current diagnostic strategies for suspected pulmonary embolism (PE) in Austrian hospitals. A questionnaire was sent to the medical directors of all Austrian hospitals with emergency and/or surgical, orthopedic, and medical departments. The questionnaire contained questions regarding the available equipment suitable for the imaging diagnosis of PE, the first-line and second-line imaging tests for patients with suspected PE, and additional lower extremity venous imaging and laboratory tests that complement the diagnostic armamentarium. The return rate for questionnaires was 81% (127 of 157 hospitals). There were 97% of hospitals that had the equipment to perform sonography, 59% could perform pulmonary angiography, 54% spiral CT, 19% ventilation/perfusion (V/P) scintigraphy, and 4% perfusion scintigraphy alone. Spiral-CT angiography (SCTA) was the first-line imaging study for suspected PE in 56% of hospitals, followed by echocardiography and V/P scintigraphy. Lower extremity venous imaging (47%) and, interestingly, V/P scintigraphy (43%), served as second-line imaging tests. D-dimer tests were included in the diagnostic strategy in 74% of hospitals. Spiral-CT angiography is the most commonly used primary method for suspected PE in Austrian hospitals. The V/P scintigraphy is available only in a minority of hospitals to investigate patients with suspected PE. When V/P scintigraphy is available, however, it is employed in a large number of patients per annum.     

Clinically suspected pulmonary embolism: is it safe to withhold anticoagulation after a negative spiral CT?

The goal of this study was 3-month clinical outcome in non-anticoagulated patients with clinically suspected acute pulmonary embolism (PE) following a negative spiral CT. During a 6-month period 305 patients underwent spiral CT, of whom only 8 also had a lung scintigraphy. In patients with a final CT report read as not positive for acute PE, all hospital records and answers to a patient questionnaire were analyzed for episodes of venous thrombembolism (VTE). Acute PE was diagnosed at spiral CT in 61 patients (20 %). Twenty-six of the remaining 244 patients were excluded from further analysis because of (a) long-term anticoagulation due to symptomatic acute deep venous thrombosis (n = 5), clinically diagnosed acute PE (n = 2), chronic recurrent VTE (n = 4), and cardiac disorders (n = 5); and (b) a normal perfusion scintigram (n = 4) or a negative pulmonary arteriogram (n = 6). Three patients were lost to follow-up. Among the remaining 215 patients only 10 had undergone a negative lower extremity venous study. Sixteen patients (7 %) died during the follow-up period, 6 of whom underwent autopsy. Venous thrombembolism was diagnosed in three of the 215 patients (1.4 %, 95 % confidence limits: 0.5–4.0 %), one causing the patient's death. Two patients had advanced thoracic malignancies and the third severe chronic obstructive pulmonary disease (84 years old). A negative spiral CT may be able to exclude clinically significant acute PE with the same accuracy as a normal lung scintigraphy or a negative pulmonary arteriography. Received: 8 February 2000 Revised: 18 May 2000 Accepted: 22 May 2000     

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.     

Noninvasive assessment of portomesenteric venous thrombosis: current concepts and imaging strategies

Rapid, noninvasive imaging strategies, especially multidetector spiral CT and CT angiography (CTA) as well as gadolinium-enhanced MR angiography (MRA), have facilitated early diagnosis of splanchnic venous thrombosis, a potentially lethal cause of intestinal ischemia. Single breath-hold volumetric acquisitions permit superior temporal and contrast resolution while eliminating motion artifact and suppressing respiratory misregistration. Increased spatial resolution is aided by thinner slice collimation. These cross-sectional imaging techniques are becoming a preferred noninvasive alternative to conventional selective mesenteric angiography with delayed imaging for venous evaluation and should be considered the primary diagnostic modalities for evaluating patients with high clinical suspicion of nonsurgical mesenteric ischemia.     

Negative spiral CT in acute pulmonary embolism

PURPOSE: To retrospectively evaluate the clinical outcome of non-anticoagulated patients with clinically suspected acute pulmonary embolism (PE) and no symptoms or signs of deep venous thrombosis (DVT) following a negative contrast medium-enhanced spiral CT of the pulmonary arteries (s-CTPA). MATERIAL AND METHODS: During a 24-month period, 739 of 751 patients underwent s-CTPA with acceptable diagnostic quality for clinically suspected acute PE. All patients who had a CT study not positive for PE were followed up with a questionnaire, a telephone interview and review of all medical reports, including autopsies and death certificates for any episodes of venous thromboembolism (VTE) during a 3-month period. RESULTS: PE was diagnosed in 158 patients. Of the remaining 581 patients with a negative s-CTPA, 45 patients were lost to follow-up. 88 patients were excluded because of anticoagulation treatment (cardiac disorder n=32, chronic VTE or acute symptomatic DVT n=31, PE diagnosed at pulmonary angiography n=1, thrombus prophylaxis during diagnostic work-up or other reasons than VTE n=24) and 7 patients undergoing lower extremity venous studies because of symptoms of DVT (all negative). Thus, 441 patients with a negative s-CTPA and no DVT symptoms, venous studies or anticoagulant treatment constituted the follow-up cohort. Four of these patients had proven VTE (all PE) during the 3-month follow-up period. Two of the PE episodes contributed to the patient's death. CONCLUSION: Patients with clinically suspected acute PE, no symptoms or signs of DVT and a negative single slice s-CTPA using 3-5 mm collimation, may safely be left without anticoagulation treatment unless they are critically ill, have a limited cardiopulmonary reserve and/or if a high clinical suspicion remains.     

64层螺旋CT血管造影对肺动脉栓塞的临床诊断价值

目的探讨64层螺旋CT血管造影对肺动脉栓塞的临床诊断价值。方法 30例患者行肺动脉CTA检查,并采用多平面重建（MPR）对原始数据进行后处理。结果 30例均能显示肺栓塞的部位、范围及局部管腔狭窄程度,CT表现为肺动脉内不规则斑块状、附壁样缺损,周围有或无高密度对比剂包绕。结论 64层螺旋CT血管造影是临床诊断肺动脉栓塞最有效的无创性方法之一。     

Non-traumatic neurological emergencies: imaging of cerebral ischemia

Cardiovascular disease is the leading cause of death worldwide with almost one-third of all cardiovascular deaths ascribed to stroke. Imaging modalities, such as CT, MRI, positron emission tomography (PET), and single photon emission CT (SPECT) provide tremendous insight into the pathophysiology of acute stroke. Computed tomography is considered the most important initial diagnostic study in patients with acute stroke, because underlying structural lesions, such as tumor, vascular malformation, or subdural hematoma, can mimic stroke clinically. Diffusion-weighted imaging (DWI) has the ability to visualize changes in diffusion within minutes after the onset of ischemia and has become a powerful tool in the evaluation of patients with stroke syndrome. Territories with diffusion and perfusion mismatch may define tissues at risk, but with potential recovery. An alternative strategy with CT technology uses rapid CT for dynamic perfusion imaging, with similar goals in mind. Angiography can be performed in the hyperacute stage if thrombolytic therapy is being considered. Indications for diagnostic angiography include transient ischemic attacks in a carotid distribution, amaurosis fugax, prior stroke in a carotid distribution, a high-grade stenotic lesion in a carotid artery, acquiring an angiographic correlation of magnetic resonance angiography (MRA) or computed tomographic angiography (CTA) concerning stenotic findings. In 50% of all angiograms performed in the hyperacute stage, occlusion of a vessel is observed; however, the need for angiography has been made less necessary due to the improvements of MRA, duplex ultrasound, and CTA. Numerous etiologies can lead to infarction. In children, pediatric stroke is very uncommon. The most common cause is an embolus from congenital heart disease with right-to-left shunts. Also a dissection of large extracranial vessels may result in cerebral infarction, and although the brain is equipped with numerous venous drainage routes, the occlusion of a large sinus or a widespread vein obstruction will eventually lead to venous infarction. Thus, optimal stroke care requires not only early and exact identification of ischemia, but also a close collaboration between the clinician and radiologist.     

MRA for diagnosis of venous thromboembolism.

Direct imaging of pulmonary embolism (PE) and deep vein thrombosis (DVT) with CT, and potentially with MR, will continue to replace V/Q scintigraphy. Venous imaging with MR far detecting DVT is used in a few centers, and their published accuracy figures are impressive. Recent studies of MR pulmonary angiography for PE reported that sensitivity of MRA was 85-100%, specificity 95-96%, but this data must be confirmed in other centers and patient populations. MR has advantages compared with CT, which make it worthwhile to continue MR development. Ionizing radiation and iodinated contrast material are not used. Imaging the pulmonary arteries and then imaging whichever venous region is of clinical interest is practical in a single examination. Repeated examinations can be performed safely. New contrast materials will facilitate the practicality and accuracy of the MR technique and perfusion imaging may increase sensitivity. MR also has disadvantages compared with CT. It does not image effectively the non-vascular compartment of the lungs. It is more expensive, patient monitoring is more cumbersome, and a routine technique, which embodies all of MR's potential advantages, has not been packaged and tested. Accordingly, helical CT is a realistic option in clinical management of patients with suspected PE in most centers, while clinical application of MR is limited to centers with appropriate MR expertise and technology. However, MR has a number of fundamental characteristics that make it a potentially ideal modality for evaluating patients with suspected acute venous thromboembolic disease and further clinical research with MRA is warranted.     

Update on diagnostic strategies of pulmonary embolism

Acute pulmonary embolism is a frequent disease with non-specific findings, high mortality, and multiple therapeutic options. A definitive diagnosis must be established by accurate, non-invasive, easily performed, cost-effective, and widely available imaging modalities. Conventional diagnostic strategies have relied on ventilation-perfusion scintigraphy complemented by venous imaging. If the results are inconclusive, pulmonary angiography, which is regarded as the gold standard, is to be performed. Recently, marked improvements in CT and MRI and shortcomings of scintigraphy led to an update of the diagnostic strategy. Spiral CT is successfully employed as a second-line procedure to clarify indeterminate scintigraphic results avoiding pulmonary angiography. It can also be used as a first-line screening tool if service and expertise is provided. Venous imaging is indicated if CT is inconclusive. The MRI technique can be applied as an alternative second-line test if spiral CT is not available or is contraindicated. It has the greatest potential for further developments and refinements. Echocardiography should be used as a first-line bedside examination in critical patients. If inconclusive stabilized patients undergo spiral CT, unstable patients should be referred for pulmonary angiography. Chronic thromboembolic pulmonary hypertension is a rare sequela of acute pulmonary embolism which can be cured surgically. Morphology, complications, and differential diagnoses are better illustrated by spiral CT and MRA, whereas invasive acquisition of hemodynamic data is the sole advantage of angiography. Received: 25 February 1998; Revision received: 8 June 1998; Accepted: 10 June 1998     

16层螺旋CT双期脑血管成像诊断脑静脉血管瘤的价值

目的：探讨16层螺旋CT双期脑血管成像对脑静脉血管瘤的临床诊断价值。方法：回顾性分析15例脑静脉血管瘤的16层螺旋CTA及CTV表现。结果：动脉期CT血管造影5例未发现明显异常，10例病灶仅部分显示，且密度淡。静脉期脑CT血管造影15例均清晰显示放射状排列的髓静脉及中央静脉，整个形态似海蛇头。结论：16层螺旋CT双期血管造影能清晰显示脑静脉血管瘤的影像特征，是诊断本病的可靠方法。     

螺旋CT肺动脉造影对肺栓塞的诊断

目的：评价螺旋CT及其肺动脉造影诊断肺动脉栓塞（PE）的价值。方法：回顾性分析12例PE患,均行螺旋CT容积扫描,并在工作站进行图像后处理,获得肺动脉多平面重建图像及三维立体图像。结果：对12例196支肺动脉分支进行分析,受累率为46.4%;栓子发生在主肺动脉、左右肺动脉干及叶段肺动脉。多平面重建图像上表现为充盈对比剂血管内有充盈缺损区,或其远侧方无对比剂充填区。肺动脉成像示,主干血管内可见充盈缺损影,或呈截断状影;叶栓塞或段栓塞亦呈突然“截断状”,其远侧方肺动脉分支不显影或呈纤维状。结论：螺旋CT肺动脉造影不仅可以获得轴位图像,而且可以获得立体图像,可多轴向旋转观察PE部位,是诊断叶或段以上PE可靠而直观的检查方法。     

螺旋CT血管造影在心肌桥-壁冠状动脉血管形态学诊断中的应用价值

目的分析螺旋CT血管造影(CTA)在心肌桥-壁冠状动脉(MB-MCA)血管形态学诊断中的应用效果。方法选取本院2019年6月至2020年6月诊治的95例冠状动脉造影(CAG)诊断确诊MB-MCA患者开展本次试验研究,95例患者住院后均给予CTA,分析CTA诊断结果。结果 CTA检查浅在型MB-MCA和深在型MB-MCA的狭窄程度与CAG检查均基本一致(P>0.05),CTA检查浅在型MB-MCA和深在型MB-MCA的MB长度均明显高于CAG检查(P<0.05);CTA检查浅在型与深化型MB-MCA的诊断结果与CAG诊断结果具有一致性(P>0.05)。结论给予MB-MCA患者螺旋CTA能够获取到准确且详细的诊断结果,能够为患者后续临床治疗工作打下良好基础,具有推广价值。     

Diagnosis of pulmonary embolism with spiral CT as a second procedure following scintigraphy

Our objective was to evaluate, in a routine clinical setting, the role of spiral CT as a second procedure in patients with clinically suspected pulmonary embolism (PE) and abnormal perfusion scan. We prospectively studied the role of spiral CT in 279 patients suspected of PE. All patients started their diagnostic algorithm with chest radiographs and perfusion scintigraphy. Depending on the results of perfusion scintigraphy, patients proceeded to subsequent levels in the algorithm: stop if perfusion scintigraphy was normal; CT and pulmonary angiography if subsegmental perfusion defects were seen; ventilation scintigraphy followed by CT when segmental perfusion defects were seen; and pulmonary angiography in this last group when results of ventilation/perfusion scintigraphy and CT were incongruent. Reference diagnosis was based on normal perfusion scintigraphy, high probability perfusion/ventilation scintigraphy in combination with abnormal CT, or pulmonary angiography. If PE was present, the largest involved branch was noted on pulmonary angiography, or on spiral CT scan in case of a high-probability ventilation/perfusion scan and a positive CT scan. A distinction was made between embolism in a segmental branch or larger, or subsegmental embolism. Two hundred seventy-nine patients had abnormal scintigraphy. In 27 patients spiral CT and/or pulmonary angiography were non-diagnostic and these were excluded for image analysis. Using spiral CT we correctly identified 117 of 135 patients with PE, and 106 of 117 patients without PE. Sensitivity and specificity was therefore 87 and 91%, respectively. Prevalence of PE was 53%. Positive and negative predictive values were, respectively, 91 and 86%. In the high-probability group, sensitivity and specificity increased to 97 and 100%, respectively, with a prevalence of 90%. In the non-high probability-group sensitivity and specificity decreased to 61 and 89%, respectively, with a prevalence of 25%. In a routine clinical setting single-detector spiral CT technology has limited value as a second diagnostic test because of low added value in patients with a high-probability lung scan and low sensitivity in patients with non-high-probability lung scan result.     

碘对比剂在下肢深静脉CT成像中的应用和技术要点

目前,CT扫描技术已成为诊断下肢深静脉血栓的重要影像手段。由于下肢静脉独特的解剖学特点,获得高质量静脉CT血管影像尚有一定难度,目前临床应用的间接静脉法、直接静脉法及双向法等多种CT检查技术亦均有其各自的局限性。因此,如何安全、合理使用碘对比剂,以提高下肢深静脉管腔内对比剂浓度的同时减少伪影,并通过降低碘对比剂的用量防止对比剂急性肾损害的发生,一直是临床上关注的热点问题。现就不同CT检查方法的技术要点以及碘对比剂用量、注射流率、浓度及温度等参数的应用策略予以综述。     

CT pulmonary angiography and suspected acute pulmonary embolism

PURPOSE: To evaluate the use and quality of CT pulmonary angiography in our department, and to relate the findings to clinical parameters and diagnoses. MATERIAL AND METHODS: A retrospective study of 324 consecutive patients referred to CT pulmonary angiography with clinically suspected pulmonary embolism (PE). From the medical records we registered clinical parameters, blood gases, D-dimer, risk factors and the results of other relevant imaging studies. RESULTS: 55 patients (17%) had PE detected on CT. 39 had bilateral PE, and 8 patients had isolated peripheral PE. 87% of the examinations showing PE had satisfactory filling of contrast material including the segmental pulmonary arteries, and 60% of the subsegmental arteries. D-dimer test was performed in 209 patients, 85% were positive. A negative D-dimer ruled out PE detected at CT. Dyspnea and concurrent symptoms or detection of deep vein thrombosis (DVT), contraceptive pills and former venous thromboembolism (VTE) were associated with PE. The presence of only one clinical parameter indicated a negative PE diagnosis (p < 0.017), whereas two or more suggested a positive PE diagnosis (p < 0.002). CT also detected various ancillary findings such as consolidation, pleural effusion, nodule or tumor in nearly half of the patients; however, there was no association with the PE diagnosis. CONCLUSION: The quality of CT pulmonary angiography was satisfactory as a first-line imaging of PE. CT also showed additional pathology of importance in the chest. Our study confirmed that a negative D-dimer ruled out clinically suspected VTE.     

Demonstration of pulmonary embolism with gadolinium-enhanced spiral CT

The authors report a case of successful detection of pulmonary embolism using gadolinium-enhanced spiral CT (Gadodiamide, 0.4 mmol/kg, 2 ml/s, delay 18 s) in a 77-year-old woman, with previous allergy to iodinated contrast medium, and renal failure, who presented with pulmonary arterial hypertension. Doppler ultrasound of the lower limbs was first performed and revealed a deep venous thrombosis of the right lower limb. To establish if venous thrombosis was the cause of pulmonary hypertension and to confirm that pulmonary endarterectomy was not indicated in this situation, several imaging modalities were performed. Lung scintigraphy and MRI were non-diagnostic. Gadolinium-enhanced spiral CT demonstrated a large thrombus located proximally and in a segmental artery of the right lower lobe. This case illustrates the potential usefulness of gadolinium as alternative contrast agent with spiral CT to diagnose pulmonary embolism and elucidate the cause of pulmonary arterial hypertension in a patient with some contraindications for iodinated contrast medium injection.     

Non-traumatic thoracic emergencies: CT venography in an integrated diagnostic strategy of acute pulmonary embolism and venous thrombosis

Deep venous thrombosis and pulmonary embolism are the two aspects of venous thrombo-embolism. Investigation of lower limb veins has been part of various diagnostic algorithms in the past 15 years. Recently, the combination of CT venography (CTV) of lower limbs and abdominal veins together with CT angiography of the pulmonary arteries has allowed a complete examination of venous thrombo-embolism in one session. The technical aspects, imaging findings, venous anatomy on CT, interpretative pitfalls, results and advantages of CT venography are reviewed.     

多层螺旋CT三维重建技术对下肢深静脉血栓的诊断价值

目的：探讨多层螺旋CT三维重建（3D）技术对下肢深静脉血栓的诊断价值。方法：对62例临床怀疑下肢深静脉血栓的患者行16层螺旋CT直接深静脉造影,并在后处理工作站进行3D成像。结果：多层螺旋CT 3D成像可准确、立体、直观的显示下肢深静脉血栓的部位、范围、侧支循环的情况及周围毗邻关系。结论：多层螺旋CT直接静脉造影术技术方法成熟完善,三维重建图像清晰,该技术对下肢深静脉血栓诊断明确,对治疗具有重要的临床指导价值。