CT angiography of pulmonary arteries to detect pulmonary embolism: improvement of vascular enhancement with low kilovoltage settings

PURPOSE: To retrospectively compare a low kilovoltage scanning protocol with a reduced radiation dose with a standard high kilovoltage, moderate-dose protocol for the depiction of central and peripheral pulmonary arteries at single-detector spiral computed tomography (CT). MATERIALS AND METHODS: This retrospective study had institutional review board approval; informed consent was waived. A 100-kVp protocol (volume CT dose index [CTDI(vol)], 3.4 mGy) was compared with a standard 140-kVp protocol (CTDI(vol), 10.4 mGy) in two groups that were each composed of 35 consecutive patients who were suspected of having pulmonary embolism (PE) and scanned with otherwise identical acquisition parameters and contrast material injection protocols. Mean main pulmonary artery enhancement and maximum enhancement in peripheral pulmonary arteries were compared. In a blinded evaluation, the percentages of segmental and subsegmental arteries that were considered analyzable for assessment of PE were determined. Overall image quality and delineation of various anatomic areas were subjectively assessed. Comparison of percentages of analyzable segmental and subsegmental arteries and subjective grading of image quality between the two different protocols were performed with the Mann-Whitney U test. RESULTS: There were 38 male and 24 female patients (mean age, 61 years; range, 17-86 years) in the final evaluation. There was a significantly higher average CT number in the main pulmonary artery (379 HU +/- 95) for the 100-kVp protocol than for the 140-kVp protocol (268 HU +/- 63, P < .001, two-sided t test). Maximum CT numbers in peripheral pulmonary arteries at the level of the aortic arch and lung bases, respectively, were 290 HU +/- 91 and 279 HU +/- 100 for 100 kVp and 185 HU +/- 65 and 144 HU +/- 63 for 140 kVp (P < .001). Mean percentage of subsegmental arteries considered analyzable per patient was higher for 100 kVp than for 140 kVp (segmental arteries, 92% vs 88%, P = .13; subsegmental arteries, 71% vs 55%, P < .001). Subjective grading of overall image quality and of the delineation of structures in the lungs, mediastinum, and upper abdomen did not significantly differ between protocols. CONCLUSION: At reduced radiation exposure, low kilovoltage scanning increases the percentage of central and peripheral pulmonary arteries that can be evaluated with CT angiography without a substantial decrease in image quality.     

Multi-detector row CT angiography of pulmonary circulation with gadolinium-based contrast agents: prospective evaluation in 60 patients

PURPOSE: To prospectively evaluate gadolinium dose safety and effectiveness for 16-detector pulmonary computed tomographic (CT) angiography. MATERIALS AND METHODS: Ethics committee approval and informed consent were obtained. Sixty patients with contraindications to iodine underwent CT of the pulmonary circulation with 0.5 mmol/L gadolinium chelate given at either 0.3 (n = 29, group A) or 0.4 (n = 31, group B) mmol/kg; clinical and biologic tolerances were evaluated. Enhancement of central and segmental pulmonary arteries was measured (poor enhancement, <100 HU; good, 100-150 HU; excellent, >150 HU). Subsegmental artery enhancement was assessed as similar or inferior to that of segmental arteries. Confidence in analysis of the pulmonary arterial bed was graded according to arterial enhancement: Grades 1-3, diagnostic images; grade 4, nondiagnostic. The main effectiveness parameter for comparison between groups A and B was diagnostic value of CT angiograms. Nonparametric statistics were used to analyze results. RESULTS: The mean (+/- standard deviation) contrast material volume was 50.09 mL +/- 8.45 (all patients: range, 30-64 mL; group A: 46.54 mL +/- 8.59; group B: 53.42 mL +/- 6.92). Diagnostic images were obtained in 55 (92%) patients, and confident analysis of pulmonary arteries to the subsegmental level was achieved in 26 (grade 1, 44%) and to the segmental level, in 21 (grade 2, 35%). Mean attenuation was higher in group B than in group A in central (180.61 HU +/- 53.85 vs 148.14 HU +/- 52.61; P = .04) and segmental (201.59 HU +/- 54.70 vs 164.73 HU +/- 59.26; P = .03) arteries. Number of diagnostic CT angiograms was higher (P = .02) in group B (n = 31 [100%]) than in group A (n = 24 [83%]). In both groups, mean enhancement of pulmonary arteries was significantly higher at 80 or 100 kV than at 120 kV. Renal function was impaired in two group A patients. CONCLUSION: Gadolinium chelates may be used as an alternative CT contrast agent in patients who cannot receive iodine.     

Computed tomography densitometry of the lung: a method to assess perfusion defects in acute pulmonary embolism

OBJECTIVE: To evaluate the potential of spiral computed tomography (CT) densitometry of the lung to assess segmental perfusion defects in patients with acute pulmonary embolism. MATERIALS AND METHODS: Ten patients with known segmental or lobar perfusion defects on ventilation/perfusion scintigraphy and with normal findings in the contralateral lung segment underwent spiral CT of the thorax before and after the administration of contrast material. Regions of interest were defined in 14 segments with normal perfusion and in 14 segments with reduced perfusion. Three consecutive densitometry measurements were performed in each segment. RESULTS: Those segments with reduced perfusion showed a significantly lower mean CT value on the enhanced scans (-813.4 +/- 57.1 Hounsfield units (HU) vs -794.0 +/- 44.8 HU, P = 0.01) and a significantly decreased contrast enhancement (12.3 +/- 18.2 HU vs 29.8 +/- 16.6 HU, P <0.01) when compared to segments with normal perfusion. Measurements from the unenhanced CT scans were not statistically different between segments with reduced and normal perfusion. CONCLUSIONS: Spiral CT densitometry allows the assessment of at least segmental perfusion defects in patients with acute pulmonary embolism.     

Effects of window and threshold levels on the accuracy of three-dimensional rendering techniques in coronary artery electron-beam CT angiography

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the effect of window level and gray-scale threshold on the demonstration of coronary artery lumina at three-dimensional electron-beam computed tomographic (CT) angiography. MATERIALS AND METHODS: Forty-four coronary artery branches in postmortem pigs were evaluated with electron-beam CT angiography, and the findings were compared with those from conventional angiography. Images from electron-beam CT angiography were reconstructed with maximal intensity projection (MIP), multiplanar reformation (MPR), and shaded-surface display (SSD). Four categories of window level and gray-scale threshold were evaluated. RESULTS: Three-dimensional electron-beam CT angiography accurately depicted the luminal diameters of the coronary arteries compared with conventional angiography (r = 0.83-0.90, P < .0001). The length of lumina visualized at electron-beam CT angiography was significantly shorter than that visualized with conventional angiography (P < .001). The use of MPR enabled visualization of longer segments of coronary arteries than did the use of MIP or SSD (P < .05). The higher the window level and gray-scale threshold used, the smaller the coronary luminal diameters measured (P < .05). The most accurate window level and gray-scale threshold (82.6 HU +/- 29.8 and 89.5 HU +/- 29.7, respectively) were found to correspond to the attenuation of the lumina (275.8 HU +/- 58.8). Results of simple linear regression showed a strong correlation between luminal attenuation and window level (r = 0.89, P < .0001) or gray-scale threshold (r = 0.95, P < .0001). CONCLUSION: Electron-beam CT angiography shows promise in the visualization of coronary artery lumina. For accurate display of lumina, a proper window level and gray-scale threshold for three-dimensional rendering techniques should be determined and used on the basis of the attenuation of the target vessel.     

Peripheral pulmonary arteries: how far in the lung does multi-detector row spiral CT allow analysis?

PURPOSE: To analyze the influence of multi-detector row spiral computed tomography (CT) on identification of peripheral pulmonary arteries. MATERIALS AND METHODS: Peripheral pulmonary arteries were analyzed on optimally opacified contrast material-enhanced spiral CT angiograms in 30 patients devoid of pleuroparenchymal disease who underwent scanning with multi-detector row CT (collimation, 4 x 1 mm; pitch, 1.7-2.0; scanning time, 0.5 second). Two series of scans were systematically generated from each data set, 1.25-mm-thick (group 1) and 3-mm-thick (group 2) sections, leading to the analysis of 600 segmental (20 arteries per patient), 1,200 subsegmental (40 arteries per patient), 2,400 fifth-order (80 arteries per patient), and 4,800 sixth-order (160 arteries per patient) pulmonary arteries in each group. RESULTS: Multi-detector row CT with reconstructed scans of 1.25-mm-thick sections (group 1) allowed (a) analysis of a significantly higher percentage of subsegmental arteries (94% in group 1 vs 82% in group 2; P <.001) and (b) a significantly higher percentage of fifth- and sixth-order arteries, respectively, identified in 74% and 35% of cases in group 1 and 47% and 16% in group 2 (P <.001). The causes for inadequate depiction of subsegmental branches in group 1 were partial volume effect (43%), anatomic variants (39%), and cardiac (17%) and respiratory (1%) motion artifacts. CONCLUSION: Multi-detector row CT with reconstructed scans of 1.25-mm-thick sections enables accurate analysis of peripheral pulmonary arteries down to the fifth order on spiral CT angiograms.     

Cardiac electron-beam CT in children undergoing surgical repair for pulmonary atresia.

PURPOSE: To study whether electron-beam computed tomography (CT) is as accurate as conventional angiocardiography for the characterization of the true pulmonary arteries and the aortopulmonary collateral vessels in children undergoing surgical correction for pulmonary atresia. MATERIALS AND METHODS: Twenty-three children with pulmonary atresia underwent 48 cardiac-triggered dynamic contrast material-enhanced electron-beam CT studies. Correlation was made with surgical findings in all patients and with 34 cineangiocardiograms. Data from reconstructed electron-beam CT images and cineangiocardiograms were reviewed for the presence, caliber, and origin of true pulmonary arteries and aortopulmonary collateral vessels; for stenosis; for thrombosis; and for the patency of vascular conduits and shunts. RESULTS: Electron-beam CT was more sensitive than angiography in the identification of hypoplastic and/or nonconfluent branch pulmonary arteries, coronary anomalies, conduit and shunt thrombosis, and other postoperative complications, but it was less sensitive in the demonstration of stenoses at collateral vascular origins and anastomoses. Overall test parameters for electron-beam CT and angiography to characterize pulmonary vascularity were similar (sensitivity, 0.94 vs 0.90; specificity, 0.99 for both; accuracy, 0.97 vs 0.95). Three-dimensional reconstructions, although they were helpful in conveying electron-beam CT findings to referring cardiologists and surgeons, did not add diagnostic information to that displayed on images of the transverse sections. CONCLUSION: Electron-beam CT complements conventional diagnostic angiocardiography in preoperative evaluation, especially in the detection of hypoplastic pulmonary arteries. It is well suited for postoperative shunt surveillance.     

Carbon Dioxide Contrast Enhancement for C-Arm CT Utility for Treatment Planning during Hepatic Embolization Procedures

A pilot study was performed to evaluate the use of carbon dioxide (CO₂) as a contrast medium for C-arm computed tomography (CT). C-arm CT using CO₂ was performed during embolization procedures in12 patients with hepatic malignancies and severe iodine allergy or high risk for nephrotoxicity. C-arm CT using gadolinium or iodinated contrast medium was performed for comparison. Of segmental arteries identified by conventional contrast enhancement, 96% were also seen with CO₂ enhancement, but subsegmental arteries were not reliably depicted. CO₂ enhancement identified 60% of tumors. Small, hypovascular, and infiltrative tumors were difficult to detect. CO₂ is a promising alternative intraarterial contrast agent for C-arm CT.     

多层螺旋CT对周围肺动脉显示能力的研究

目的比较多层螺旋CT肺动脉造影不同层厚重建对周围肺动脉的显示能力. 资料与方法 21例无肺部疾患和血栓病史的患者行CT肺动脉造影检查,均用0.75 mm准直扫描,分别用0.75 mm/0.5 mm（层厚/层间距）（A组）、1.0 mm/0.6 mm（B组）、1.5 mm/1.0 mm（C组）重建,记录每例患者3种不同重建层厚对段肺动脉、亚段肺动脉、5级和6级肺动脉的显示情况及血管不能显示的原因. 结果 3组人均肺段动脉的显示率均为96.45%（19.29/20）;人均亚段动脉显示率分别为94.42%、93.44%、91.13%,3组间均无显著性差异;A、B、C组对第5级肺动脉的人均显示率分别为80.44%、73.47%、59.02%,A组与C组有显著性差异（P＜0.01）,B组与C组间有显著性差异（P＜0.05）;6级肺动脉3组人均显示率分别为33.75%、31.69%、23.56%,A组与C组有显著性差异（P＜0.01）.段肺动脉不能分析的主要原因是解剖变异（53.33%）和心脏搏动伪影（40%）;A、B组亚段肺动脉不能分析的主要原因是解剖变异和心脏搏动伪影,C组的主要原因是部分容积效应（43.84%）与A组比较有显著性差异（10.87%）（P=0.015）;3组对5级和6级肺动脉不能分析的主要原因均为部分容积效应. 结论多层螺旋CT肺动脉造影0.75 mm、1.0 mm、1.5 mm重建层厚对段肺动脉和亚段肺动脉均有很好的显示率,A、B组对5级肺动脉的显示率也较好.影响亚段肺动脉显示的主要原因是解剖变异和心脏搏动伪影.1.0 mm重建层厚可满足肺动脉的观察和图像处理的需要.     

Pulmonary embolism: optimization of small pulmonary artery visualization at multi-detector row CT

PURPOSE: To compare the frequency of well-visualized pulmonary arteries according to anatomic level by using different collimation with single- and multi-detector row computed tomography (CT) in patients suspected of having acute pulmonary embolism. MATERIALS AND METHODS: Sixty patients were examined with one of three techniques (20 patients each). Group 1 was examined with single-detector row CT with 3-mm collimation and 1.3-1.6 pitch; groups 2 and 3, with multi-detector row CT with 2.5- and 1.25-mm collimation, respectively. Three thoracic radiologists independently reviewed examination findings to determine if each main, lobar, segmental, and subsegmental artery was well visualized for presence of pulmonary embolism. chi2 tests were performed. For well-visualized vessels, the presence and/or absence of pulmonary embolism was recorded and kappa statistic was determined. RESULTS: Reader 1 scored 95% (114 of 120), 96% (115 of 120), and 99% (119 of 120) of lobar arteries (P >.05); 76% (304 of 400), 86% (346 of 400), and 91% (363 of 400) of segmental arteries (P <.001); and 37% (300 of 800), 56% (448 of 800), and 76% (608 of 800) of subsegmental arteries as well visualized (P <.001) using techniques 1, 2, and 3, respectively. Reader 2 scored 97% (116 of 120), 95% (114 of 120), and 99% (119 of 120) of lobar arteries (P >.05); 77% (308 of 400), 87% (349 of 400), and 93% (371 of 400) of segmental arteries (P <.001); and 39% (310 of 800), 53% (422 of 800), and 78% (621 of 800) of subsegmental arteries (P <.001) as well visualized using techniques 1, 2, and 3, respectively. Reader 3 scored 86% (103 of 120), 82% (98 of 120), and 91% (109 of 120) of lobar arteries (P >.05); 63% (252 of 400), 70% (280 of 400), and 85% (339 of 400) of segmental arteries (P <.001); and 39% (310 of 800), 56% (451 of 800), and 71% (572 of 800) of subsegmental arteries (P <.001) as well visualized using techniques 1, 2, and 3, respectively. Sixteen patients had pulmonary embolism. Interobserver agreement for detection of pulmonary embolism was significantly better for segmental and subsegmental arteries for all readers with technique 3 (segmental, kappa = 0.79-0.80; subsegmental, kappa = 0.71-0.76) than that with technique 1 (segmental, kappa = 0.47-0.75; subsegmental, kappa = 0.28-0.54). CONCLUSION: Multi-detector row CT at 1.25-mm collimation significantly improves visualization of segmental and subsegmental arteries and interobserver agreement in detection of pulmonary embolism.     

实验性急性肺栓塞的比较影像学研究

目的　探讨核素肺灌注显像、增强螺旋CT及数字减影肺动脉造影对猪急性肺栓塞实验模型 (相当于人类亚肺段水平肺栓塞 )的影像学特点。方法　 13头中国实验用小型猪 ,经颈静脉注射明胶海绵栓子 (直径 3 8～ 4 2mm) ,制作肺栓塞模型后进行核素肺灌注显像、增强螺旋CT和数字减影肺动脉造影 ,以病理检查为标准 ,比较 3种检查方法的灵敏度和特异性。结果　对 195个肺段(动脉段 )进行分析 ,病理诊断阳性肺段 4 6个 ,阴性肺段 14 9个。核素肺灌注显像阳性肺段 5 1个 (包括假阳性肺段 11个 ) ,灵敏度为 87% ,特异性为 93% ;增强螺旋CT阳性肺段 4 4个 (包括假阳性肺段15个 ) ,灵敏度为 6 3% ,特异性为 90 % ;数字减影肺动脉造影阳性肺段 4 7个 (包括假阳性肺段 2个 ) ,灵敏度为 98% ,特异性为 99%。核素肺灌注显像病变检出率比增强螺旋CT高 (P <0 0 5 ) ,但与数字减影肺动脉造影相比差异无显著性 (P >0 0 5 )。增强螺旋CT可对栓子进行准确定位。结论　核素肺灌注显像对猪肺段 (相当于人类亚肺段 )肺栓塞的探测优于增强螺旋CT ,而后者对栓子定位优于前者 ;数字减影肺动脉造影对猪肺段肺栓塞诊断能力最强 ,但有创 ,应用受限。     

Subsegmental pulmonary emboli: improved detection with thin-collimation multi-detector row spiral CT

PURPOSE: To compare different reconstruction thicknesses of thin-collimation multi-detector row spiral computed tomographic (CT) data sets of the chest for the detection of subsegmental pulmonary emboli. MATERIALS AND METHODS: A multi-detector row spiral CT protocol for the diagnosis of pulmonary embolism was used that consisted of scanning the entire chest with 1-mm collimation within one breath hold. In 17 patients with central pulmonary embolism, the raw data were used to perform reconstructions with 1-mm, 2-mm, and 3-mm section thicknesses. For each set of images, each subsegmental artery was independently graded by three radiologists as open, containing emboli, or indeterminate. RESULTS: For the rate of detection of emboli in subsegmental pulmonary arteries, use of the 1-mm section width yielded an average increase of 40% when compared with the use of 3-mm-thick sections (P <.001) and of 14% when compared with the use of 2-mm-thick sections (P =.001). With the use of 1-mm sections versus 3-mm sections, the number of indeterminate cases decreased by 70% (P =.001). Interrater agreement was substantially better with the use of 1-mm and 2-mm sections than with the use of 3-mm sections. CONCLUSION: For the diagnosis of subsegmental pulmonary emboli at multi-detector row CT, the use of 1-mm section widths results in substantially higher detection rates and greater agreement between different readers than the use of thicker sections.     

Suspected pulmonary embolism: enhancement of pulmonary arteries at deep-inspiration CT angiography--influence of patent foramen ovale and atrial-septal defect

PURPOSE: To investigate if abnormal early contrast enhancement of the aorta and decreased attenuation of pulmonary arteries at deep-inspiration spiral computed tomographic (CT) angiography might be caused by a patent foramen ovale (PFO). MATERIALS AND METHODS: Two hundred forty-four spiral CT angiographic images of the pulmonary arteries obtained during deep inspiration in patients suspected of having pulmonary embolism (PE) were reviewed for evidence of abnormal early enhancement of the aorta. In 45 patients, enhancement of the ascending aorta was equal to or more than that of the pulmonary arteries. Nonenhanced or contrast material-enhanced echocardiography was performed in 39 of these cases. All CT images with abnormal enhancement patterns were graded for contrast quality with respect to sufficient enhancement of pulmonary arteries (four grades) at three anatomic levels: right and left main and lobar and segmental branches. In addition, all spiral CT angiographic images were evaluated concerning the diagnosis of PE and the grouping of central (main pulmonary artery to proximal lobar arteries) and peripheral (beyond proximal lobar branches) locations of emboli. Mean attenuation values of ascending aortas and main pulmonary arteries in group 1 (n = 244) were compared with those in groups 2 and 3 (n = 45) by means of the two-tailed Student t test for unpaired data (P <.05). RESULTS: Attenuation values for ascending aortas in group 1 were significantly lower than those in groups 2 and 3 (P <.001). Attenuation values in main pulmonary arteries were significantly higher in group 1 than in groups 2 and 3 (P <.001). Echocardiographic images showed an intracardiac right-to-left shunt in all 39 cases with abnormal contrast dynamics in the CT study (16% of the whole study population). Three patients had an atrial-septal defect, and 36 had a PFO. Images with a shunt had good (9%), intermediate (37%), fair (33%), and poor (23%) contrast of the pulmonary arteries. Sufficient vessel contrast for the diagnosis of PE could not be achieved in 27 of 45 patients with a shunt, but severe central PE could be ruled out. PE could be diagnosed in 31% of the 244 images, 58% were negative, and 11% were indeterminate. CONCLUSION: A PFO may frequently lead to insufficient attenuation of the pulmonary arteries, which potentially limits the diagnosis of PE if the examination is performed during deep inspiration.     

螺旋CT在肺动脉栓塞诊断中的价值

目的:评价螺旋CT在诊断肺动脉栓塞中的作用。方法:16例肺动脉栓塞患者行螺旋CT肺动脉造影 (SCTA)检查,层厚3mm,扫描时间0.8s,对比剂注射速度3.5ml/s,总量100ml,扫描延迟时间15s。结果:16例 共644支,其中134支肺动脉及分支显示了栓塞,占20.8%。228支肺段肺动脉中,有56支显示肺动脉栓塞,占分 析肺动脉支的24.5%。204支亚段肺动脉中37支显示肺动脉栓塞,占分析肺动脉支15.4%。肺动脉栓塞的CT形 态:①直接征象为不同程度的肺动脉分支内充盈缺损。中心型充盈缺损17支,偏心型充盈缺损44支,附壁血栓型 34支,完全阻塞型39支。②间接征象胸膜下肺梗死灶,内乳动脉一侧增粗,肺纹理稀少,胸水,肺动脉高压。结论: 螺旋CT肺动脉造影是诊断肺动脉栓塞的快速、有效、无创伤的诊断方法。     

Aortoiliac gadolinium-enhanced CT angiography: improved results with a 16-detector row scanner compared with a four-detector row scanner

PURPOSE: To assess the level of vascular enhancement of gadolinium-enhanced aortoiliac computed tomographic (CT) angiography with a 16-detector row CT scanner and to compare it with the results of previous similar studies that used four-detector row CT units. MATERIALS AND METHODS: Eleven gadolinium-enhanced CT angiograms were obtained in 10 consecutive patients with contraindication to iodinated contrast medium with use of a 16-detector row CT scanner. In the region of interest, attenuation measurements (in HU) were obtained from the proximal abdominal aorta to the common femoral arteries during unenhanced, gadolinium-enhanced, and delayed acquisitions. The results were compared to those in the 15 consecutive patients who most recently had similar examinations performed on a four-detector row CT unit. Phantom studies with diluted gadolinium were conducted to compare attenuation between CT units. RESULTS: On four-detector row CT, throughout the scan length, mean enhancement values were 53.8 HU +/- 5.3 and 15.0 HU +/- 2.6 for gadolinium-enhanced and delayed series, respectively. For the 16-detector row CT unit, they were 76.1 HU +/- 3.4 and 21.3 HU +/- 1.3, respectively. As a result of a shorter scan time and a more optimal start time, the 16-detector row CT unit provided significantly greater and more consistent enhancement throughout the scan length compared with the four-detector row CT unit (P =.0106). Similar structures had significantly greater enhancement when 120 kV was applied instead of 140 kV (P =.0495) CONCLUSION: The 16-detector row CT scanner improved gadolinium-enhanced CT angiography results compared with the four-detector row CT unit.     

平静呼吸轻屏气在改善肺动脉CT强化效果中的应用研究

目的:探讨"深吸气后屏气"肺动脉CTA(CTPA)扫描发生短暂性对比剂中断(TIC)后,"平静呼吸轻屏气"在改善肺动脉强化效果中的应用价值.方法:回顾分析2774例"深吸气后屏气"状态下完成CTPA检查的患者,筛选因发生TIC导致肺动脉强化不佳并立即行"平静呼吸轻屏气"CTPA重复扫描者.对两次扫描的肺动脉段级及以上分...     

右房密度监测触发 CT 肺动脉成像

目的：通过对右房(RA)CT 值的监测,寻找其达峰时间,优化 CT 肺动脉成像(CTPA)显像。方法采集拟行 CTPA 的患者60例,随机分成2组,肺动脉触发(PT)组(n=30)：注射70 mL 对比剂(CA)并屏气,采用肺动脉干 CT 值监测触发方式获取CTPA 图像;RA 组(n=30)：注射40 mLCA,自由呼吸,并采用 RA 监测触发方式。对图像质量、肺动脉及肺静脉 CT 值、肺动脉-肺静脉密度差值等进行对比。结果RA 组图像质量、肺动脉平均值及肺动脉-肺静脉密度差明显高于 PT 组(P <0.05),而 RA 组肺静脉 CT 值更低(P <0.05)。肺动脉6级分支显示比例2组无统计学差异(P >0.05)。结论自由呼吸状态下基于 RA 密度监测触发的 CTPA 能在肺静脉 CT 值最低时使肺动脉得到最大强化,且 CA 使用量减少。     

16层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用

目的　研究 16层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用价值。方法　使用 16层螺旋CT扫描机 (SiemensSensation 16 )对临床拟诊肺栓塞的 4 9例患者进行前瞻性研究。采用层厚 3mm行胸部增强扫描。利用原始数据行层厚 1mm的轴面及多平面重建 (MPR)。比较层厚 3mm、1mm的轴面图像及MPR图像。结果　CT诊断肺栓塞 4 2例。病变共累及肺动脉 35 2支。对于主肺动脉及肺叶动脉栓塞 ,三种图像检出结果一致。但对于肺段及亚段动脉栓塞 ,层厚 1mm较 3mm显示率高 ,差异有显著意义 (P <0 0 1) ,1mm的MPR较轴面图像显示率高 ,但差异无显著性意义 (P >0 0 5 )。结论　 16层螺旋CT肺血管造影无创、快速、敏感性高 ,应当作为肺栓塞的首选检查方法。     

Pulmonary embolism: comprehensive diagnosis by using electron-beam CT for detection of emboli and assessment of pulmonary blood flow

P:URPOSE: To comprehensively assess thoracic anatomy and pulmonary microcirculation in pulmonary embolism by using computed tomographic (CT) angiography of the pulmonary arteries combined with functional CT imaging of blood flow. MATERIALS AND METHODS: Twenty-two patients suspected of having acute pulmonary embolism underwent contrast material-enhanced thin-section electron-beam CT angiography of the pulmonary arteries. In addition, in each patient, a dynamic multisection blood flow CT study was performed on a 7.6-cm lung volume with electrocardiographic gating. Pulmonary blood flow was calculated, and perfusion parameters were visualized on color-coded maps. The color-coded maps and CT angiograms were independently evaluated, segment by segment, by two readers for perfusion deficits and the presence of clots, respectively. The results were compared. RESULTS: Mean pulmonary blood flow was 0.63 mL/min/mL in the occluded segments versus 2.27 mL/min/mL in the nonoccluded segments (P: =.001). The sensitivity and specificity of perfusion maps for the presence of segmental pulmonary embolism compared with those of CT angiography were 75.4% and 82.3%, respectively, with positive and negative predictive values of 79.6% and 84.7%, respectively. The false-negative findings were caused mainly by partial occlusion of vessels. In eight patients, a substantial alternative or additional pathologic entity was diagnosed. CONCLUSION: By combining CT angiography and dynamic CT imaging, a comprehensive and noninvasive diagnosis of thoracic structure and function is feasible with a single modality.     

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.     

64层螺旋CT肺动脉造影在肺动脉栓塞诊断中的应用

目的 探讨64层螺旋CT肺动脉造影(CT pulmonary angiography,CTPA)对肺动脉栓塞(pulmonary embolism,PE)的诊断价值.方法 回顾分析24例肺动脉栓塞患者的64层螺旋CT增强图像,将原始图像复制到EBW4.0工作站,对肺动脉主干及分支进行多平面重建(MPR),最大密度投影(MIP)及容积重建(VR)分析.结果 24例患者中,共检出了76处肺动脉及其分支的栓子.其中,左、右肺动脉主干14处(右主干10处、左主干4处),肺叶动脉24处,肺段动脉26处,亚肺段动脉12处.CT表现为肺动脉主干或分支内混合性、附壁性、中心性充盈缺损,可分为完全性或部分性.结论 64层CTPA具有准确、高效、无创等优点,可直观、立体地观察到肺动脉血栓的大小、分布、范围及类型,是临床诊断及观察疗效的首选方法,有望成为肺动脉栓塞检查的“金标准”.