MSCT不同层厚的最大密度投影在肺动脉栓塞诊断中的价值

目的：比较16层螺旋CT图像后处理中不同层厚的MIP重组图像对于肺动脉栓子的检出率。方法：对于32例临床拟诊为肺动脉栓塞的患者,采用层厚5mm的胸部增强扫描,利用原始数据分别行0.75mm组,2.mm组,5mm组,10mm组MIP重建。显示清楚的叶、段、亚段肺动脉内有无栓子,并行χ^2检验。结果：CT诊断肺动脉栓塞23例,病变共累及肺动脉72支,对于肺动脉主干及各叶肺动脉栓塞,前4组图像检出率分别为100%、100%、95.2%、90.5%。对于肺段及亚段肺动脉栓塞的检出,0.75mm组及2.mm组（检出率分别为96.1%、90.2%）明显高于5mm组,10mm组（检出率分别为82.9%、60.8%）,0.75mm组及2.0mm组在统计学上没有显著差异（P值为0.433）。2.mm组与5.0mm组、10mm组在统计学上有显著差异。（P值分别为0.004,0.001）。结论：多层螺旋CT,2mm层厚MIP重建图像能明显提高段、亚段肺动脉栓子的显示率,又能减少图像数目,有重要的诊断价值,5.0mm组1、0mm层厚MIP重建图像定位准确,直观明了,为重要的补充,MIP后处理技术为检出肺动脉栓子的最佳技术。     

16层螺旋CT肺动脉造影图像质量的影响因素研究

目的:探讨16层螺旋CT肺动脉造影(CTPA)成像质量的影响因素,为进一步提高肺动脉栓塞(PE)诊断质量提供帮助。方法:对临床拟诊肺栓塞病例46例行CTPA。扫描准直为0.75mm×16,图像后处理包括5mm、0.75mm横断面图像,不同厚度MIP、MPR,不同窗位及颜色的VR。观察内容包括肺动脉、血栓及肺动脉伪影。结果:CTPA诊断PE病人37例均为双肺多发肺动脉栓子,累及动脉189支。2mm MIP、MPR清晰显示亚段及其1~2级分支动脉,并显示肺动脉内栓子的部位及形态;5mm MIP、20mm MIP对亚段及分支动脉的显示不如2mm MIP(P<0.05)。VR立体感强,调节窗位及颜色可观察肺动脉及血栓表现。16例(34.7%)出现肺动脉搏动伪影,心胸比例增大,则伪影加重。结论:CTPA的成像质量主要受扫描技术及图像后处理技术的影响,合理应用成像技术可进一步提高PE诊断准确率。     

不同扫描条件对CT肺动脉成像图像质量的影响

目的研究不同扫描条件对CT肺动脉成像(CTPA)图像质量的影响,从而探讨肺栓塞误诊的多种原因。资料与方法46名志愿者随机分为A、B两组。A组选用1.25mm×16i探测器,层厚1.25mm,间隔1.25mm。B组选用0.625mm×64i探测器,层厚1mm,间隔0.7mm。增强扫描A组选用300mgI/100ml对比剂50ml,注射流率4ml/s;B组选用相同对比剂20ml,注射流率5ml/s。延时时间均根据预试验结果确定。两名有经验的放射科医师采用盲法在同一工作站上阅读两组CTPA横断面图像。计数所能显示的肺动脉血管数目、测量左右心室最大层面和双肺下叶后基底段肺动静脉断面的CT值并计算其差值、观察图像产生的各种伪影(呼吸运动伪影;流动相关伪影;硬束假影、部分容积伪影等)。结果A组显示肺段动脉共425支,B组可计数432支。A组肺动脉主干与左房CT差值为(153.4±82)HU;B组为(165.6±64)HU,两者差异无统计学意义。A组双肺下叶后基底段肺动静脉CT差值为(64.1±31.2)HU;B组(118.7±42)HU,两者差异有统计学意义。A组及B组呼吸运动相关伪影均为0例。流动相关伪影A组2例(8.7%);B组7例(30.4%),差异有统计学意义。硬束假影A组21例(91.3%),B组4例(17.4%),差异有统计学意义。部分容积伪影A组13例(56.5%),B组6例(26.1%),差异有统计学意义。结论减小探测器厚度及扫描层厚,加快对比剂注射流率,降低注射量,可以提高CTPA的图像质量。     

MSCT肺血管成像对肺动脉栓塞的诊断价值

目的:探讨多层螺旋CT肺血管成像对肺动脉栓塞的诊断价值.方法:对24例肺动脉栓塞病例行多层螺旋CT肺动脉成像检查,图像采用1.0mm层厚、0.7mm层间距和0.75mm层厚、0.5mm层间距进行重建,CTPA后处理采用容积再现(VRT)、最大密度投影(MIP)和多平面重建(MPR),对重建的图像进行对照分析、比较优缺点.结果:24例病例中,病变共累及76支肺动脉,其中,主肺动脉6支、肺叶动脉36支、肺段动脉27支、亚段动脉7支.肺动脉栓塞病变显示,1.0mm及0.75mm层厚重建无显著性差异意义.结论:多层螺旋CT肺动脉成像具有安全、快速、无创优点,对肺动脉栓塞诊断特异性强、敏感性高,可作为肺动脉栓塞的首选检查方法.     

多层螺旋CT不同层厚重建方法在肺栓塞诊断中的价值

目的比较不同重建层厚多层螺旋CT(MSCT)对肺动脉栓子的显示率及其诊断价值。方法对38例MSCT检查的肺栓塞患者分别行2.5 mm(组1)和1.25 mm(组2)横断面重叠重建,记录显示清楚的叶、段、亚段及第5级肺动脉内有无栓子,并行2χ检验。判定不同水平肺动脉分支内有无栓子的一致程度,计算к值。结果在叶、段、亚段肺动脉水平,栓子显示数占显示清楚肺动脉的比率,观察者1的组1和组2分别为38%和40%(P>0.05)、17%和21%(P<0.05)、1.7%和4.6%(P<0.05),观察者2的组1和组2分别为35%和37%(P>0.05)、16%和21%(P<0.05)、1.6%和4.2%(P<0.05)。叶、段、亚段肺动脉水平,观察者间的к值,组1分别为0.70、0.69、0.63,组2分别为0.78、0.86、0.70。结论MSCT 1.25 mm层厚重建图像能明显提高段、亚段肺动脉栓子的显示率和不同观察者间的一致程度,有重要诊断价值。     

MSCT肺动脉成像不同准直宽度对周围肺动脉显示率的对比研究

目的 采用MSCT不同准直宽度评价周围肺动脉的显示.方法 搜集本院2011年9月至2011年12月行胸部增强扫描并符合纳入标准的病例80例,采用浓度300 mgI/ml对比剂50 ml,按照不同准直分为四组,64×0.6 mm(A:3 ml/s;B:5 ml/s),16×1.5 mm(C:3 ml/s;D:5ml/s)分组,每组20例.统计分析5、6级肺动脉的显示率.结果 A与C组、B与D组肺动脉干、左肺动脉、右肺动脉、4级肺动脉平均CT值、4级肺动脉显示率比较无统计学差异(P＞0.05)；A和C组比较5级肺动脉下叶区有统计学差异(P＜0.05)；B和D组比较6级肺动脉上叶区和中/舌叶区有统计学差异(P＜0.05).结论 0.6 mm与1.5 mm准直对于亚段动脉的显示均良好,差异无统计学意义,而对于强化程度良好的5、6级肺动脉的显示有重要的意义.     

肺动脉DSA产生呼吸伪影的原因分析

目的探讨肺动脉DSA影像产生呼吸伪影的原因,提高影像质量。方法95例肺动脉DSA检查患者分为两组,研究组采用被动屏气方法,对照组采用主动屏气方法;再依据血氧饱和度（SpO2）将研究组分为A、B两组,对照组分为C、D两组,通过主观评价法,分别分析各组呼吸伪影产生的数量,并经SPSS15．0软件对其进行统计学分析。结果研究组伪影显示率为20．83％,对照组伪影显示率为63．83％,P＝0．00002;A组伪影显示率为40．0O％,B组伪影显示率为7．14%,P＝0．016;C组伪影显示率为94．12％,D组伪影显示率为46．67％,P＝0．001。结论肺动脉DSA影像呼吸伪影的产生与屏气动作和SpO2关系密切。     

MSCT肺血管造影诊断肺栓塞的临床价值分析

目的探讨MSCT肺血管造影在肺栓塞中的诊断价值。方法随机选取我院45例疑似肺动脉栓塞患者作为观察对象,分为A、B两组,A组25例采用3. 2mm层厚、2. 5mm准直扫描;B组20例采用1. 3mm层厚,1. 0mm准直扫描,对B组中的10例患者进行下肢深静脉扫描。结果两组叶肺动脉、主肺动脉的差异无统计学意义(P 0. 05);5级分支及亚段、对段显示B组1. 0mm准直优于A组2. 5mm准直,差异有统计学意义(P 0. 05);MSCTPA显示468支肺动脉受累。结论 MSCT肺血管造影能够清楚呈现肺栓塞的间接象征和直接象征,1. 0mm准直薄层扫描在发现外围肺动脉栓塞方面优于2. 5mm准直扫描。     

低心率下第二代双源CT冠脉成像Flash扫描与序列扫描图像质量及伪影比较

目的:比较低心率下CT前瞻性心电触发Flash扫描与序列扫描的冠状动脉图像质量及伪影。方法:回顾性连续收集Flash扫描(A组)与序列扫描(B组)冠状动脉CT成像各80例患者,心率均≤70次/min。4级法评价2组图像质量,初步分析伪影特点及成因。结果:A、B 2组可评价冠状动脉节段为98.37%和99.29%,差异无统计学意义(χ2=3.56,P=0.094);可评价患者为85.00%和96.25%,差异有统计学意义(χ2=4.708,P=0.035);平均节段质量评分为(1.295±0.60)分和(1.21±0.59)分,差异有统计学意义(Z=-2.591,P=0.010)。A组的4级图像大部分分布于右冠中远段,多数出现在心率大于65次/min的患者中,均为心脏搏动伪影。B组4级图像散在分布于冠脉各段中,为呼吸及心脏搏动伪影。A组辐射剂量明显低于B组,差异有统计学意义。结论:低心率下Flash与序列扫描均可获得高质量冠状动脉图像,序列扫描略优于Flash扫描;Flash扫描右冠状动脉中远段出现心脏搏动伪影概率大,序列扫描易产生呼吸及心律不齐所致伪影。     

多层螺旋CT重建参数对头颈部肿瘤MPR图像质量的影响

目的　分析多层螺旋CT(MSCT)重建及重组参数对头颈部肿瘤MPR图像质量的影响 ,以便选择最佳的参数组合。资料与方法　使用GELightspeedUltra 8层螺旋CT扫描机对 6 7例头颈部肿瘤患者进行扫描。分为两部分 ,第一部分 2 8例 ,分别对原始数据进行 1.2 5mm、2 .5mm层厚的轴面重建 ,重叠率均为 5 0 %。图像重组时 ,分别采用层厚 1mm、2mm、3mm和 5mm。第二部分 39例 ,分别采用 0 %、2 5 %、5 0 %和 75 %的重叠率和 1.2 5mm层厚进行轴面重建 ,然后采用 1mm层厚进行图像重组。应用双盲法评价各组图像质量 ,并进行统计学处理。结果　第一部分 ,在软组织、骨质和伪影方面组内差异有极显著性 (P <0 .0 1) ,1.2 5mm层厚轴面重建的各组MPR图像中 ,1mm层厚组对软组织和骨质的显示好于其他各组 (P <0 .0 1)。第二部分 ,在软组织、病变、骨质和伪影方面组内差异有极显著性 (P <0 .0 1) ;在软组织和病变方面 ,5 0 %与 75 %重叠率图像质量最佳 ,两者差异无显著性 (P >0 .0 5 ) ;在骨质方面 75 %重叠率组图像质量高于 5 0 %组 (P <0 .0 5 ) ;在伪影方面 ,5 0 %重叠率组好于 75 %组 (P <0 .0 1)。结论　头颈部肿瘤MSCT图像后处理采用 1.2 5mm层厚、5 0 %重叠率进行轴面重建后 ,用 1mm层厚的MPR图像能很好地显示软组织、病变     

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.     

Thoracic helical CT: influence of subsecond scan time and thin collimation on evaluation of peripheral pulmonary arteries

The objective of this study was to analyze the influence of collimation on the identification of peripheral pulmonary arteries on helical CT scans. Three hundred sixty of 370 consecutive helical CT angiograms of the pulmonary circulation obtained during an 18-month investigation period were considered as technically acceptable for the detection of acute pulmonary embolism and were retrospectively analyzed. Patients in group A (n = 274) underwent CT with 2-mm collimation and pitch of 2; those in group B (n = 86) underwent CT with 3-mm collimation and pitch 1.7; a 0.75-s rotation time was systematically used. A total of 2160 segmental (six arterial zones per patient) and 2160 subsegmental (six arterial zones per patient) arterial zones were assessed. Whereas the percentage of segmental arteries was not significantly different between group A (86 %) and group B (89 %), the percentage of analyzable subsegmental arteries was greater in group A (65 %) than in group B (43 %) (P < 0.001). The causes of inadequately depicted subsegmental arterial zones were partial-volume effects (group A, n = 302; 52 %; group B, n = 197; 67 %; P < 0.001), suboptimal enhancement (group A, n = 145; 25 %; group B, n = 43; 15 %; P < 0.05), motion artifacts (group A, n = 113; 20 %; group B, n = 30; 10 %), and unincluded arteries (group A, n = 20; 3 %; group B, n = 25; 8 %). Helical CT with 2-mm collimation at 0.75 s per revolution enables marked improvement in the analysis of subsegmental arteries in routine clinical practice. Received: 25 January 2000; Revised: 28 March 2000; Accepted: 30 March 2000     

Segmental and subsegmental pulmonary arteries: evaluation with electron-beam versus spiral CT

PURPOSE: To compare contrast agent-enhanced spiral and electron-beam computed tomography (CT) for the analysis of segmental and subsegmental pulmonary arteries. MATERIALS AND METHODS: CT angiography of the pulmonary arteries was performed in 56 patients to rule out pulmonary embolism. Electron-beam CT was performed in 28 patients. The other 28 patients underwent spiral CT with comparable scanning protocols. The depiction of segmental and subsegmental arteries was analyzed by three independent readers. The contrast enhancement in the main pulmonary artery was measured in each patient. RESULTS: Analysis was performed in 1,120 segmental and 2, 240 subsegmental arteries. One segmental (RA7, P =.010) and two subsegmental (LA7b, P =.029; RA6a+b, P =.038) arteries in paracardiac and basal segments of the lung were depicted significantly better with electron-beam CT. There was no statistically significant difference between electron-beam and spiral CT in the total number of analyzable peripheral arteries depicted. The mean contrast enhancement in the main pulmonary artery was 362 HU in electron-beam CT studies versus 248 HU in spiral CT studies. CONCLUSION: Detailed visualization of peripheral pulmonary arteries is well within the scope of advanced CT techniques. Electron-beam CT has minor advantages in analyzing paracardiac arteries, probably because of reduction of motion artifacts and higher contrast enhancement. Further studies are needed to establish whether electron-beam CT allows a more confident diagnosis of emboli in these vessels.     

多层螺旋CT在肺动脉栓塞诊断中的应用价值

目的 研究多层螺旋CT在肺动脉栓塞诊断中的临床应用，着重研究亚段肺动脉栓塞的诊断价值。方法 共34例，下肢深静脉血栓16例，近期大手术史11例，肺癌1例，不明原因6例。34例均使用GE Light Speed Plus多层螺旋CT(MSCT)行平扫及造影增强扫描，1次采集4层图像。结果 分析34例共1824支肺动脉分支，其中507支肺动脉分支显示了栓塞，占27．8％。在680支肺段动脉中，246支显示了栓塞，占36．2％；而亚段肺动脉1041支中，141支显示了栓塞，占13．5％。平扫肺动脉栓塞的间接征象为肺纹理稀少19例，肺动脉高压2例，胸水16例，胸膜下梗死灶共41个，梗死灶多发11例，单发12例，双肺6例。1例慢性栓塞栓子钙化，极为少见。造影增强后肺动脉栓塞的直接征象为不同程度的肺动脉分支充盈缺损。充盈缺损有4种表现形式：中心型57支，偏心型160支，附壁血栓131支，完全阻塞型159支。结论 多层螺旋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，尤其对亚段肺动脉栓塞是一种先进的方法，可以代替肺动脉造影，可与电子束CT媲美，可能成为诊断肺动脉栓塞的首选方法。     

多层螺旋CT肺血管造影在肺动脉栓塞中的应用

目的：探讨多层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用。方法：使用6层螺旋CT对39位肺动脉栓塞患者进行血管成像检查。应用准直1．0mm,螺距1．25进行扫描,将得到的原始数据行层厚1．25mm、3．0mm轴面重建,MIP2mm、5mm多视角多平面重组及MRP重组。分析不同后处理技术的检出栓塞动脉支数进行比较。结果：39例肺动脉栓塞患者,共累及肺动脉血管326支,以上5种重建方法对肺动脉主干及叶动脉的栓塞,显示检出结果一致。对段及亚段动脉的栓塞MPR优于其它后处理方法（P〈0．05）。结论：多层螺旋CT血管造影是肺栓塞安全、敏感性且特异性高的无创性诊断方法,其图像后处理技术更为直观、全面的显示栓子的形态、部位、范围。     

Value of contrast-enhanced MR angiography and helical CT angiography in chronic thromboembolic pulmonary hypertension

The aim of this study was to evaluate the diagnostic value of contrast-enhanced MR angiography (ce MRA) and helical CT angiography (CTA) of the pulmonary arteries in the preoperative workup of patients with chronic thromboembolic pulmonary hypertension (CTEPH). The ce MRA and CTA studies of 32 patients were included in this retrospective evaluation. Image quality was scored by two independent blinded observers. Data sets were assessed for number of patent segmental, subsegmental arteries, and number of vascular segments with thrombotic wall thickening, intraluminal webs, and abnormal proximal to distal tapering. Image quality for MRA/CTA was scored excellent in 16 of 16, good in 11 of 14, moderate in 2 of 5, and poor in no examinations. The MRA/CTA showed 357 of 366 patent segmental and 627 of 834 patent subsegmental arteries. CTA was superior to MRA in visualization of thrombotic wall thickening (339 vs 164) and of intraluminal webs (257 vs 162). Abnormal proximal to distal tapering was better assessed by MRA than CTA (189 vs 16). In joint assessment of direct and indirect signs, MRA and CTA were equally effective (353 vs 355). MRA and CTA are equally effective in the detection of segmental occlusions of the pulmonary arteries in CTEPH. CTA is superior for the depiction of patent subsegmental arteries, of intraluminal webs, and for the direct demonstration of thrombotic wall thickening.     

Spatial domain image filtering in computed tomography: feasibility study in pulmonary embolism

Our objective was to evaluate the clinical feasibility of spatial domain filtering as an alternative to additional image reconstruction using different kernels in chest CT. Spatial domain filtering generates smooth images from sharp images and thus avoids the need for additional reconstructions when two sets of images are desired. Forty adult patients with clinical suspicion of pulmonary embolism were examined utilizing multi-slice CT (Somatom Volume Zoom, Siemens, Germany). Derived from thin collimated source images (100 mAs, collimation 4×1 mm, rotation time 0.5 s, table speed 7 mm/rotation), two sets of images [effective slice thickness (S_eff) 5 mm, reconstruction increment (RI) 5 mm) were generated using lung (Siemens B50) and soft tissue (Siemens B30) kernels. Additionally, B50 images were filtered in the spatial domain, producing images largely equivalent to B30 images. Firstly, diagnostic accuracy was assessed on spatial domain filtered images regarding central, segmental, and subsegmental pulmonary embolism. In a second step, diagnostic accuracy was assessed for the initially reconstructed B30 images. The results were compared with thin axial slices from the same data set, which were considered as the gold standard in this respect (S_eff 1.25 mm, RI 0.8 mm; B30). Initially reconstructed B30 slices and secondary filtered images were rated for subjective image quality, using a five-point scale (1=excellent, 2=good, 3=moderate, 4=poor, 5=non-diagnostic). Finally, quantitative measurements were assessed using the region of interest (ROI) methodology. In 20 patients pulmonary embolism was proven. Five-millimeter images revealed 10 of 10 central emboli, 18 of 19 segmental thrombi, and 18 of 20 emboli on the subsegmental level. Pulmonary embolism was excluded in 18 of 20 subjects, and in 2 patients a false-positive result was obtained in subsegmental arteries. These findings were concordant for reconstructed and filtered images. Quantitative density measurements provided comparable Hounsfield units in this respect. Subjective gradings of image quality, based on soft tissue settings, were 1.30 (±0.61) for reconstructed slices vs 1.35 (±0.62) for filtered images (weighted kappa coefficient 0.6117; 95% confidence intervals 0.3298–0.8935). Spatial domain filtering has proved to be feasible. Compared with conventional soft tissue reconstructions for central, segmental, and subsegmental pulmonary embolism, no significant difference in the diagnostic value of spatial domain filtered images was found. Online modifications of image sharpness and pixel noise in real time leads to a considerable reduction of processing time and cost saving for storage of CT images. Despite different data processing methods, thin effective slice thicknesses and overlapping reconstruction increments are mandatory for detailed CT analysis of pulmonary embolism on the segmental and subsegmental level. Electronic Publication     

40层螺旋CT在肺动脉栓塞诊断中的应用价值

目的:探讨40层螺旋CT在肺动脉栓塞中的应用价值.方法:使用40层螺旋CT扫描机(Siemens Defination AS 40)对临床初步诊断肺动脉栓塞的38例患者进行研究.采用层厚5 mm行胸部增强扫描.利用3D后处理工作站进行重建为0.75 mm的轴面及多平面重建(MPR).比较层厚5 mm和1mm的轴面图像及MPR图像.结果:CT诊断肺动脉栓塞31例.病变共累计肺动脉260支.对于主肺动脉及肺叶动脉栓塞,3种图像检出结果一致.但对于肺段及亚段肺动脉栓塞的显示,层厚0.75 mm优于5 mm,差异有显著性意义(P<0.01),0.75 mm的MPR与轴面图像间差异无显著性意义(P＞0.05).结论:40层螺旋CT在肺动脉栓塞诊断中具有无创、快速、敏感性高的优点,应当作为肺动脉栓塞的首选检查方法.     

Detection of pulmonary embolism using 16-slice multidetector-row computed tomography: evaluation of different image reconstruction parameters

OBJECTIVE: To compare different image reconstruction parameters for detecting emboli of the pulmonary arteries according to anatomic levels using 16-slice multidetector-row computed tomography in patients suspected of having an acute pulmonary embolism (PE). METHODS: Sixty-two patients (33 male and 29 female) with a clinically suspected acute PE were included in the present study. Multidetector-row computed tomography scans were performed using 16-mmx0.75-mm collimation. Based on the computed tomography data set, different image reconstruction parameters were used for each patient: axial slice thicknesses (STs) of 0.75, 2, 4, and 6 mm; axial maximum intensity projection (MIP) STs of 4 mm; and coronal STs of 2 and 4 mm. In joint reading fashion, 2 experienced radiologists reviewed examination findings regarding the presence and/or absence of a PE. The reference standard for visualization and detection of PEs was defined using the axial images with a 0.75-mm ST. RESULTS: In 23 of 62 patients, a PE was diagnosed. For main and lobar pulmonary arteries, the sensitivities and specificities were as follows: axial 2-mm images, 1.0/1.0; axial 4-mm images, 1.0/1.0; axial 6-mm images, 0.97/0.99; MIP 4-mm images, 0.95/0.99; coronal 2-mm images, 1.0/1.0; and coronal 4-mm images, 1.0/1.0. Regarding segmental and subsegmental pulmonary arteries, sensitivity and specificity varied: axial 2-mm images, 0.97/1.0; axial 4-mm images, 0.81/0.99; axial 6-mm images, 0.65/0.99; axial MIP 4-mm images, 0.63/0.99; coronal 2-mm images, 0.91/0.99; and coronal 4-mm images, 0.74/0.99. CONCLUSIONS: In detecting segmental and subsegmental PEs, only the axial images with an ST of 2 mm proved to have results comparable with the axial 0.75-mm images. Therefore, thin-slice collimation and ST are mandatory for visualization of segmental and subsegmental PEs in patients suspected of having an acute PE.     

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.