Ventilation-perfusion lung scintigraphy as a guide for pulmonary angiography in the localization of pulmonary emboli.

PURPOSE: To assess the appropriateness of ventilation-perfusion (V-P) scintigraphic abnormalities as a guide to pulmonary angiography for the diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: V-P scintigrams and pulmonary angiograms of 104 patients with angiographically proved PE were reviewed by two nuclear medicine physicians and two interventional radiologists. For V-P scintigrams, the lung with the larger amount of perfusion abnormality was determined followed by identification of specific lobes. Pulmonary angiograms were similarly evaluated for lateralization and lobar distribution of PE. Conclusions were initially reached independently and subsequently by consensus. RESULTS: Interobserver agreement for lateralization was 88% (kappa = 0.75) for V-P scintigraphy and 98% (kappa = 0.96) for pulmonary angiography. In 72 patients, V-P scintigrams predicted unilateral embolus; 64 patients underwent pulmonary angiography of the suspected side. Eight patients underwent contralateral angiography only. Of the 64 patients, 61 (95%) had PE on the predicted side at angiography. V-P scintigrams predicted lobar distribution in 55 patients. Of these, PE was found in the predicted lobe in 42 (76%). CONCLUSION: Localization of perfusion abnormalities at V-P scintigraphy provides useful information for the interventional radiologist and serves as an accurate guide for determining the initial approach for pulmonary angiography.     

Detection of pulmonary emboli in dogs using digital subtraction angiography

Digital subtraction angiography (DSA) was performed in six dogs to define the limits of detection of pulmonary emboli. Three angiograms were initially obtained in three normal control animals, two of which were subsequently embolized. A total of ten pulmonary angiograms were then obtained in five dogs that had experimentally produced emboli of Ivalon cubes (2, 3, and 10 mm). The intravenous angiograms were followed by selective arterial angiograms to confirm the presence and location of the emboli. The intravenous angiograms were independently reviewed by two radiologists. The criterion for detection was identification of a vessel cutoff. Perfusion defects were also seen. No intraluminal filling defects were seen. This study indicates that pulmonary emboli greater than 2 mm in diameter may be detected in dogs by DSA.     

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.     

Combined MR proton lung perfusion/angiography and helium ventilation: potential for detecting pulmonary emboli and ventilation defects.

Three-dimensional (3D) perfusion imaging allows the assessment of pulmonary blood flow in parenchyma and main pulmonary arteries simultaneously. MRI using laser-polarized (3)He gas clearly shows the ventilation distribution with high signal-to-noise ratio (SNR). In this report, the feasibility of combined lung MR angiography, perfusion, and ventilation imaging is demonstrated in a porcine model. Ultrafast gradient-echo sequences have been used for 3D perfusion and angiographic imaging, in conjunction with the use of contrast agent injections. 2D multiple-section (3)He imaging was performed subsequently by inhalation of 450 ml of hyperpolarized (3)He gas. The MR techniques were examined in a series of porcine models with externally delivered pulmonary emboli and/or airway occlusions. With emboli, perfusion deficits without ventilation defects were observed; airway occlusion resulted in matched deficits in perfusion and ventilation. High-resolution MR angiography can unambiguously reveal the location and size of the blood emboli. The combination of the three imaging methods may provide complementary information on abnormal lung anatomy and function.     

三维增强磁共振肺动脉血管造影诊断肺动脉血栓栓塞

目的 探讨三维增强ＭＲ肺动脉血管造影（３Ｄ ｃｏｎｔｒａｓｔ－ｅｎｈａｎｃｅｄ ＭＲ ｐｕｌｍｏｎａｒｙ ａｎｇｉｏｇｒａｐｈｙ,３Ｄ ＣＥＭＲＰＡ）诊断肺动脉血栓栓塞的价值。方法 肺动脉栓塞患者１２例,共行１７次３Ｄ ＣＥＭＲＰＡ,其中４例５次于３Ｄ ＣＥＭＲＰＡ当天进行了选择性肺动脉ＤＳＡ。静脉注射钆喷替酸葡甲胺０．２ｍｍｏｌ／ｋｇ后,屏气获得２４层肺血管连续冠状面像,以最大强度投影法（ＭＩＰ     

Diagnosis of pulmonary emboli and image quality at CT pulmonary angiography: influence of imaging direction with multidetector CT

AIM: To determine whether there was a significant difference in the prevalence of emboli detected when patients underwent computed tomography pulmonary angiography (CTPA) in a craniocaudal direction versus a caudocranial direction. MATERIALS AND METHODS: This was a prospective study of 203 consecutive patients attending for CTPA for suspected pulmonary embolus. Imaging was performed on a multisection Siemens Volume Zoom CT machine, with bolus tracking centred on the main pulmonary artery after intravenous administration of contrast at 3 ml/s. Patients were examined in a single breath-hold, from the top of the aortic arch to the highest point of the diaphragm, in a randomly assigned cranio-caudal (group A), or caudo-cranial (group B) direction. Images were reviewed on a workstation in a cranio-caudal direction jointly by two radiologists unaware of the original imaging direction. The presence, number and position of arterial emboli were noted, and a subjective assessment of overall image quality and opacification of upper and lower lobe vessels (grade 1, 2, 3, or 4) was made. RESULTS: Emboli were detected in 46 patients. There was no significant difference in the prevalence of emboli detected in the two groups [group A craniocaudal direction n=22, group B caudocranial direction n=24 (p=0.76)]. Imaging direction did not significantly influence overall image quality (p=0.07), however, there was a significantly greater proportion of patients in group A with grade 1 opacification of the upper lobe arteries (p=0.02). CONCLUSION: Imaging direction does not significantly influence the diagnosis of pulmonary emboli but it does significantly improve the upper lobe pulmonary arterial enhancement with fewer non-diagnostic images, and on that basis we recommend that craniocaudal direction be used for CTPA studies.     

Incidence of pulmonary emboli on chest computed tomography angiography based upon referral patterns

Pulmonary embolism (PE) is a potentially lethal condition, and the diagnosis of PE can be difficult. The purpose of this study is to evaluate the incidence of PE on chest computed tomography angiography (CTA) studies ordered in the inpatient, outpatient, and emergency department (ED) settings and further segregated based on the adult and pediatric populations, and by the ordering clinician (attending physicians, resident physicians, or physician extenders). A retrospective review of chest CTA examinations performed between July 1,2009 and June 30, 2010 was performed. Of 5848 adult CTA studies, PE was diagnosed in 594 (10.1 %). Of these positive studies, 315 (53 %) were inpatient, 234 (39.4 %) were ED patients, and 45 (7.6 %) were outpatient. Four hundred sixty-four of 4445 (10.4 %) CTA examinations ordered by attending physicians were positive for PE. Seventy-four of the 801 (9.2 %) CTA examinations ordered by resident physicians were positive for PE. Fifty-six of the 608 CTA examinations ordered by physician extenders were positive for PE. Thirty-three pediatric CTA studies for PE met criteria and none of them indicated PE. There is no significant difference in the incidence of PE in chest CTA based on setting or ordering clinician.