三维增强磁共振肺动脉血管造影诊断急性肺栓塞的实验研究

目的 探讨钆喷替酸葡甲胺（Ｇｄ－ＤＴＰＡ）三维增强共振肺动脉血管造影成像（３ＤＣＥＭＲＰＡ）在急性肺栓塞（ｐｕｌｍｏｎａｒｙ ｅｍｂｏｌｉｓｍ,ＰＥ）中的诊断价值。方法 对１７只自体血栓引发的犬急性肺栓塞模型,利用３Ｄ快速扰相梯度回波序列（ＦＳＰＧＲ）行３Ｄ ＣＥＭＲＰＡ检查和Ｘ线肺动脉血管造影（Ｘ－ｒａｙ ｐｕｌｍｏｎａｒｙ ａｎｇｉｏｇｒａｐｈｙ,ＸＰＡ）检查,并与病理解剖对照。     

Pulmonary embolism: comparison of gadolinium-enhanced MR angiography with contrast-enhanced spiral CT in a porcine model

RATIONALE AND OBJECTIVES: The purpose of this study was to compare gadolinium-enhanced magnetic resonance (MR) angiography with contrast material-enhanced computed tomography (CT) for the detection of small (4-5-mm) pulmonary emboli (PE), with a methacrylate cast of the porcine pulmonary vasculature used as the diagnostic standard. MATERIALS AND METHODS: In 15 anesthetized juvenile pigs, colored methacrylate beads (5.2 and 3.8 mm diameter-the size of segmental and subsegmental emboli in humans) were injected via the left external jugular vein. After embolization, MR angiographic and CT images were obtained. The pigs were killed, and the pulmonary arterial tree was cast in clear methacrylate, allowing direct visualization of emboli. Three readers reviewed CT and MR angiographic images independently and in random order. RESULTS: Forty-nine separate embolic sites were included in the statistical analysis. The mean sensitivity (and 95% confidence intervals) for CT and MR angiography, respectively, were 76% (68%-82%) and 82% (75%-88%) (P > .05); the mean positive predictive values, 92% (85%-96%) and 94% (88%-97%) (P > .05). In this porcine model, PE were usually seen as parenchymal perfusion defects (98%) with MR angiography and as occlusive emboli (100%) with CT. CONCLUSION: MR angiography is as sensitive as CT for the detection of small PE in a porcine model.     

Comparison of doses for pulmonary embolism detection with helical CT and pulmonary angiography

The objective of this study was to compare the radiation exposure delivered by helical CT and pulmonary angiography (PA) for the detection of pulmonary embolism (PE), with an anthropomorphic phantom. A preliminary survey defined a representative standard procedure for helical CT and PA (n=148) by choosing the exposure settings most frequently used. Then, radiation doses were measured with thermoluminescent dosimeters TLD 100 (Lif) introduced into the depth of an anthropomorphic phantom. Average doses were approximately five times smaller with helical CT than with PA (6.4±1.5 and 28±7.6 mGy, respectively). The most important doses were abreast the pulmonary apex for CT, and abreast the pulmonary arteries for PA. Compared with PA, helical CT dose distribution was relatively uniform (10–13 mGy). Finally, concerning abdomen and pelvis, doses were more important for PA than for CT scan (0.06–2.86 and 0.2–11.5 mGy, respectively). For the diagnostics of PE, radiation exposure is five times smaller with helical CT than with pulmonary angiography.     

肺栓塞MR增强肺灌注成像与核素肺灌注显像对比实验研究

目的:比较MR及SPECT核素肺灌注显像诊断肺栓塞的价值。方法:24只大白兔建立肺栓塞模型,栓塞后6h采用3D-FLASH序列,从耳缘静脉注入Gd-DTPA行肺灌注扫描,应用Evaluation自动生成肺灌注曲线,在冠状位原始图像上两侧对称性选取正常与病变区肺实质的ROI测量时间-信号强度曲线。从耳缘静脉注入99Tcm-MAA111-148MBq0·3ml8体位显像。病理学检查:分别于栓塞后分批处死实验动物,光学显微镜下观察栓塞肺组织及正常肺组织的表现。统计学采用t检验和χ2检验。结果:成功建立20只兔肺栓塞模型,栓塞后6hMR增强肺灌注成像正常和栓塞区肺实质增强率分别为317·5%和45·1%;正常肺组织灌注曲线峰值明显,栓塞区灌注曲线低平或峰值延迟(t=11·52,P<0·01)。MR增强肺灌注成像对肺栓塞模型检测的敏感性为95%,特异性为85%;SPECT肺灌注显像敏感性100%,特异性65%,统计学分析二者检查结果差异不具有统计学意义(χ2=2·06,P>0·05)。病理显示:梗死区可见大量的纤维素渗出,肺间质增厚,动脉腔内可见红细胞和血栓形成,其周围白细胞浸润伴肺淤血,部分可见点状出血及肺淤血。结论:Gd-DTPAMR增强肺灌注成像诊断肺栓塞是可行的;MR诊断肺栓塞与SPECT具有较好的一致性。     

Real-time MR with TrueFISP for the detection of acute pulmonary embolism: initial clinical experience

The feasibility and diagnostic value of real-time magnetic resonance imaging (RT-MRI) for the diagnosis of acute pulmonary embolism (PE) was evaluated by comparing RT-MRI and magnetic resonance angiography (MRA). In 39 consecutive patients with suspected PE real-time true fast imaging with steady-state precession (TrueFisp) was prospectively compared with contrast-enhanced MRA on a 1.5-T MR scanner. The TrueFisp sequence used allowed acquisition of T2-weighted images at 0.4 s per image so that the pulmonary vasculature could be visualized in three orientations in <3 min without the need for breath holding or contrast media application. Results of additional scintigraphic pulmonary perfusion examinations were available from 17 patients. All 39 primary RT examinations (100%) and 30 of 39 MRA examinations (77%) were of diagnostic quality. The reasons underlying failure to achieve diagnostic quality for MRA were breathing artifacts among dyspneic patients in all 9 cases. Compared with MRA, the sensitivities and specificities of RT sequences for PE were 93 and 100% (per examination), 96 and 100% (lobar artery PE), and 97 and 100% (segmental artery PE), respectively. Compared with scintigraphy, the sensitivity and specificity of RT-MRI were 83 and 100%, respectively. The MRA reached 100% sensitivity and specificity in this subgroup. The RT-MRI proved to be very robust and undisturbed by respiratory movements and patient cooperation. Its image quality assured fast diagnostic examinations, and its sensitivity and specificity, compared with MRA and scintigraphy, were sufficient to allow the diagnosis of acute central, lobar, and segmental PE; therefore, the emergency diagnosis of PE using RT-MRI is feasible and reliable.     

3D-CE-MRPA诊断周围性肺栓塞的研究

目的：探讨三维增强磁共振肺血管造影(3D-CE—MRPA)对周围性肺栓塞的诊断价值。方法：8只犬于DSA下经导管将直径2—4mm、长1cm左右的明胶海绵条注入单侧肺动脉后复制为周围性肺栓塞动物模型，然后进行3D-CE—MRPA检查，观察栓塞肺动脉的CEMRPA显示情况及表现形式，分析CEMRPA诊断肺栓塞的敏感性。结果：在DSA显示的26支肺段及其以下水平栓塞肺动脉中，CEMRPA显示了21支，敏感性为80．77％，特异性为100％。栓塞肺动脉主要表现为完全或不完全截断，远侧肺野可见低灌注区存在。多平面重建协助诊断了4支原始图像上显示不清的栓塞肺动脉。结论：3D-CE—MRPA对周围性肺栓塞有较高的诊断敏感性，是诊断周围性肺栓塞的理想方法。多平面重建有助于诊断原始图像上显示不清的栓塞肺动脉。     

MR灌注成像在肺栓塞诊断中的应用

目的探讨MR二维快速扰相梯度回波序列（2DFSPGR）显示肺实质灌注的可能性,以及在实验性肺栓塞中的应用价值。方法11只在体犬肺栓塞模型在平静呼吸下行肺MR灌注扫描,定性及定量评价图像质量,与病理解剖对照分析肺灌注扫描诊断肺栓塞的敏感性。结果10只犬的MR图像质量为优良,可显示肺实质灌注情况,平均信号/噪声比（SNR）为67.4±18.0,对比度/噪声比（CNR）为40.9±14.2。正常灌注区的信号强度平均值为39.7±5.1,灌注不良区域信号强度平均值为15.6±2.1,灌注不良区域时间-强度曲线表现为峰值下降或曲线平直。结论MR肺灌注成像是诊断肺栓塞的可行方法。     

钆增强双能量CT诊断肺栓塞的实验研究

目的 评价含钆的MR对比剂进行双源双能量CT肺动脉成像(CTPA)用于诊断肺栓塞的可行性.方法 (1)用不同稀释浓度的碘对比剂和钆对比剂进行体外双源双能量CT成像,测量不同管电压条件下各样本的CT值.(2)10只新西兰大白兔以3和5 ml/kg分2组注射含钆对比剂进行双能量CT扫描,测量不同管电压下肺动脉的强化值.6只家兔在次日经股静脉注射明胶海绵栓子制作急性肺栓塞模型,2h后行双能量CT扫描.分别于2次扫描前经耳缘静脉或股静脉抽血2～3 ml行肾功能检查.方差分析和独立样本t检验用于分析不同组别肺动脉强化值的差别.结果 (1)同含碘对比剂相似,80 kV管电压条件下含钆对比剂的CT值高于140 kV和平均加权120 kV.(2)在管电压分别为140、80、平均加权120 kV时,双能量CT定量测量显示5 ml/kg组家兔主肺动脉[CT值分别为(463.1±118.0)、(664.2±188.0)、(522.9 ±137.7) HU]和肺动脉1级分支[CT值分别为(445.1 ±82.3)、(606.7 ±207.2)、(493.4±117.3)HU] CT值均高于3 ml/kg组[主肺动脉CT值分别为(258.1±55.1)、(384.0±92.3)、(295.4±73.6) HU,肺动脉1级分支CT值分别为(245.0±73.2)、(309.1 ±94.2)、(263.8 ±78.5) HU;P值均＜0.05].80 kV图像肺动脉主干和1级分支的CT值明显高于140 kV和平均加权120 kV(肺动脉主干:F =6.004,P=0.005;1级分支:F=4.374,P =0.018).6只栓塞组家兔CTPA显示两下肺动脉强化突然截断,对应的钆图显示钆含量降低,表现为蓝色伪彩色,正常非栓塞肺组织表现为红黄色伪彩色.3和5 ml/kg组肌酐增加率分别为6.7％和20.6％.结论 含钆MR对比剂具有与含碘对比剂相似的X线衰减特征,可用于对比增强的双能量CT肺成像中,同时提取出的CTPA以及显示肺灌注信息的钆图能够用于肺栓塞的诊断.     

Evolution of pulmonary perfusion defects demonstrated with contrast-enhanced dynamic MR perfusion imaging

Pulmonary perfusion defects can be demonstrated with contrast-enhanced dynamic MR perfusion imaging. We present the case of a patient with a pulmonary artery sarcoma who presented with a post-operative pulmonary embolus and was followed in the post-operative period with dynamic contrast-enhanced MR perfusion imaging. This technique allows rapid imaging of the first passage of contrast material through the lung after bolus injection in a peripheral vein. To our knowledge, this case report is the first to describe the use of this MR technique in showing the evolution of peripheral pulmonary perfusion defects associated with pulmonary emboli. Received: 27 July 1998; Revision received: 28 October 1998; Accepted: 20 January 1999     

The value of pulmonary angiography for the differential diagnosis of pulmonary embolism

The aim this study was to evaluate potential additional information of pulmonary angiography in patients with suspected pulmonary embolism and non-diagnostic lung scan findings. In a series of 150 patients who underwent pulmonary angiography for suspected venous thromboembolism, the images for potential alternative diagnoses other than pulmonary embolism were evaluated. All patients had non-diagnostic lung scan findings. Angiography was performed both by conventional and by digital subtraction angiography techniques. Images were evaluated by at least two experienced readers. Angiograms were scored for both presence or absence of pulmonary embolism, as well as other diagnoses. Pulmonary embolism was proven in 40 patients (27 %) and excluded in 105 patients (70 %), whereas non-interpretable images were obtained in 5 patients (3 %). A range of alternative diagnoses were detected by angiography: atelectasis (n = 24), pleural effusion (n = 15), pneumonia (n = 11), emphysematous bullae (n = 8), neoplasm (n = 3), atrial septum defect (n = 2), chronic thromboembolism (n = 1), and other diagnoses (n = 3). Overall, only 54 patients (36 %) had completely normal angiograms. Although pulmonary angiography remains the reference method for the diagnosis of pulmonary embolism, one has to be aware of other, often unexpected, but equally important findings which could influence the management of the patient. This aspect of pulmonary angiography has been insufficiently emphasized in the literature. Received: 2 April 1998; Revision received: 22 July 1998; Accepted: 4 November 1998     

肺灌注/通气显像与螺旋CT肺动脉造影诊断肺栓塞的对比研究

目的评价肺灌注/通气显像与螺旋CT肺动脉造影诊断肺栓塞各自的敏感性。方法以肺动脉造影为金标准,并按不同栓塞部位分为叶及段肺动脉、亚段肺动脉两组;按肺动脉狭窄程度分为严重狭窄(超过50%)和轻度狭窄(少于50%)两组。对40例疑肺栓塞患者先后行肺核素显像和螺旋CT肺动脉造影检查,根据分组分别比较两种方法的敏感性。结果①肺动脉造影共确定叶及段肺动脉栓塞102支。其中,肺灌注/通气显像显示86处叶及段性肺灌注/通气不匹配,敏感性为84.3%;螺旋CT肺动脉造影示98支,敏感性为96.1%;②肺动脉造影共确定140支亚段肺动脉栓塞,其中肺灌注/通气显示120处,敏感性为85.7%;螺旋CT肺动脉造影显示115支,敏感性为82.1%;③肺动脉狭窄程度>50%时,通气/灌注显示109处,螺旋CT肺动脉造影显示97支;肺动脉狭窄程度<50%时,通气/灌注显示91处,螺旋CT肺动脉造影显示121支。结论对叶及段肺动脉栓塞,两种方法敏感性基本相同;对亚段肺动脉栓塞,肺灌注/通气显像略高;肺血管轻度栓塞时,螺旋CT肺动脉造影略高。     

CT和MR血管成像诊断急性肺栓塞的Meta分析

目的：应用 Meta 分析法,以 DSA 为金标准,探讨 CT 肺动脉成像（CTPA）和磁共振肺血管成像（MRPA）对肺动脉栓塞（PE）的诊断价值。方法：检索 Cochrane 图书馆、Medline 数据库、Springerlink 数据库及 Ovid 循证医学数据库中1994～2013年发表的英文文献以及知网数据库和万方医学数据库中1994～2013年发表的中文文献,按照 Cochrane 协作网推荐的诊断性实验的纳入标准,严格筛选与“CTPA 和／或 MRPA 诊断急性 PE”相关的文献。在符合条件的文献中提取诊断信息（包括真阳性值、假阳性值、真阴性值、假阴性值）和其它相关数据。采用 Stata 12软件和 Meta-disc 1．4软件对纳入文献行统计学处理,包括异质性检验,计算敏感度和特异度及其95％可信区间,选择相应的效应模型予以加权定量合并,绘制汇总的工作特征曲线（SROC）,最后进行敏感性分析。结果：按照纳入标准共获取有效文献17篇,其中与 CTPA相关的文献10篇,与 MRPA 相关的文献7篇。17篇文献均满足诊断性研究质量评价工具（QUADAS）中提出的14项标准中的10项以上。CTPA 及 MRPA 两组中的相关研究均有异质性,按照随机效应模型对纳入文献进行汇总分析。结果显示,CTPA 诊断肺栓塞的敏感度、特异度及各自的95％可信区间分别为0．78（0．74～0．82）和0．90（0．87～0．92）,MR-PA 为0．86（0．79～0．92）和0．97（0．94～0．99）,SROC 下面积分别为94％和98％。结论：CTPA 和 MRPA 对急性肺栓塞的诊断均具有很高的价值,两种方法的诊断特异度均很高,作为诊断肺栓塞的无创性检查方法可基本替代 DSA 检查。     

猪肺动脉MR增强血管造影和肺灌注成像的对比剂最佳剂量研究及与DSA对照

目的　通过动物实验探讨胸部动态增强MR血管造影 (CEMRA)以及肺灌注成像 (PPI)的对比剂最佳成像剂量 ,并与DSA对照 ,评价CEMRA和PPI对肺动脉栓塞的诊断价值。方法　应用5、10、15、2 0和 2 5ml的钆喷替酸葡甲胺 (Gd DTPA)溶液 (0 5mmol/ml)以 3ml/s的流率对 6头中华黑毛猪进行肺动脉 3DCEMRA及PPI;之后 ,用明胶海绵颗粒制备猪肺动脉栓塞模型 ,再以 2 0ml剂量和3ml/s的流率进行CEMRA和PPI,通过与DSA和病理对照 ,评价其诊断急性肺动脉栓塞的能力。结果猪肺动脉的信号强度、信噪比随着对比剂的剂量增加而升高 ,肺动脉与肺组织对比度在 10～ 15ml之间 (0 2 5 0～ 0 375mmol/kg)最好。猪肺灌注的满意剂量在 15～ 2 0ml(0 375～ 0 5 0 0mmol/kg)左右。肺动脉CEMRA显示栓塞率低于DSA ,但结合肺灌注图像所显示的肺动脉栓塞数量 (10 / 10 )高于单纯DSA(8/ 10 ) ,表现为楔形低信号灌注缺损区 ,平均信号强度值为 137 86± 4 5 32 ,而正常灌注区为330 14± 4 6 5 2 ,两者差异有非常显著性意义 (t =8 4 0 ,P <0 0 0 1) ,易于辨认。结论　猪肺动脉 3DCEMRA的最佳剂量为 0 2 5 0～ 0 375mmol/kg之间 ,猪肺灌注的满意剂量在 0 375mmol/kg以上 ,兼顾血管造影和肺灌注成像的最佳剂量为 0 375mmol/kg。肺动脉C     

Comparison of perfusion lung scanning and angiography in the estimation of vascular obstruction in acute pulmonary embolism

To determine the relationships between perfusion scan defect and angiographic severity (Miller index) in acute pulmonary embolism, we analysed examinations obtained before and after thrombolytic therapy in 34 consecutive patients free from underlying cardiopulmonary disease. The overall agreement between the two techniques was excellent (r=0.82; mean absolute difference=2.8%), although when embolic involvement was extensive (greater than 50% angiographic obstruction), the perfusion scan moderately underestimated (4%) the defect seen angiographically. These findings suggest that the pulmonary lung scan is a reliable method of assessing the initial pulmonary vascular obstruction as well as of quantifying any changes induced by or associated with the treatment.French exchange travelling fellow     

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.     

CT肺血管成像对急性大面积肺栓塞患者的动态分析价值

目的 探讨CT肺血管成像(CTPA)对大面积肺栓塞患者的动脉栓塞程度及右心功能的动态分析价值.方法 回顾性分析23例大面积肺栓塞患者的CTPA资料,分析治疗前、治疗后24 h及14 d时的CTPA肺动脉栓塞指数及右心功能参数,采用单因素方差分析、LSD检验和X2检验分析治疗前后的变化,并采用Pearson法分析肺动脉栓寨指数与右心功能参数之间的相关性.结果 CTPA肺动脉栓塞指数在溶栓治疗后逐渐减小,Qanadli和Mastora评分在治疗前(分别为50.0、46.5分)与治疗后24 h(分别为42.5、12.1分)比较差异有统计学意义(t值分别为2.830、6.493,P值均<0.01);治疗后24 h与治疗后14 d(分别为25.0、8.4分)比较差异有统计学意义(t值分别为4.640、4.299,P值均<0.01).治疗后24 h,右心室最大短轴直径(4.58 cm)及横截面积(23.10 cm2)明显减小,左心室最大短轴直径(4.41 cm)及横截面积(26.37 cm2)明显增大,双侧心室最大直径比(1.07)和面积比(0.94)明显减小,与上述各指标治疗前相比(分别为5.07 cm、25.42 cm2、3.57 cm、20.17 cm2、1.59,1.38)差异有统计学意义(t=2.081～4.959,P值均<0.05);治疗后24 h,肺动脉收缩压(40.92 mm Hg)明显变小,与治疗前(58.61 mm Hg)相比差异有统计学意义(t=2.824,P<0.01);治疗前与治疗后24 h,CTPA肺动脉栓塞指数与右心功能参数间均有不同程度的相关性(r=0.034～0.598,P值均<0.01).结论 CTPA可以动态观察急性肺栓塞的肺动脉阻塞程度及右心功能的变化,为临床治疗提供重要的信息.     

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     

螺旋CT肺动脉造影诊断肺小动脉血栓的实验研究

目的：评价螺旋CT肺动脉造影（spiral CT pulmonary angiography，CTPA）诊断犬肺小动脉血栓栓子（直径2.5-3.5mm）的应用价值。方法：23条实验犬行CTPA空白对照后，制成犬自体血块肺动脉栓塞模型，先后行CTPA与X线肺动脉造影（X-ray pulmonary angiography，XPA）检查，由2名医生在工作站上分析所获图像，并与犬肺病理解剖结果对照，评价CTPA与XPA对肺动脉血栓栓塞的诊断价值。结果：22条犬完成实验全过程，病理解剖发现肺动脉内栓子110个，与人工注入栓子数目相符，均位于肺动脉的段或亚段水平，其中107个位于扫描野内。CTPA发现栓子90个，诊断肺动脉内小血栓栓子的敏感度为84.1％，阳性预测值为93.8％；XPA发现栓子82个，敏感度为76.6％，阳性预测值为94.3％。结论：CTPA对实验性肺小动脉血栓栓子有较高的诊断价值。     

3D pulmonary perfusion MRI and MR angiography of pulmonary embolism in pigs after a single injection of a blood pool MR contrast agent

The purpose of this study was to assess the feasibility of contrast-enhanced 3D perfusion MRI and MR angiography (MRA) of pulmonary embolism (PE) in pigs using a single injection of the blood pool contrast Gadomer. PE was induced in five domestic pigs by injection of autologous blood thrombi. Contrast-enhanced first-pass 3D perfusion MRI (TE/TR/FA: 1.0 ms/2.2 ms/40°; voxel size: 1.3×2.5×4.0 mm³; TA: 1.8 s per data set) and high-resolution 3D MRA (TE/TR/FA: 1.4 ms/3.4 ms/40°; voxel size: 0.8×1.0×1.6 mm³) was performed during and after a single injection of 0.1 mmol/kg body weight of Gadomer. Image data were compared to pre-embolism Gd-DTPA-enhanced MRI and post-embolism thin-section multislice CT (n=2). SNR measurements were performed in the pulmonary arteries and lung. One animal died after induction of PE. In all other animals, perfusion MRI and MRA could be acquired after a single injection of Gadomer. At perfusion MRI, PE could be detected by typical wedge-shaped perfusion defects. While the visualization of central PE at MRA correlated well with the CT, peripheral PE were only visualized by CT. Gadomer achieved a higher peak SNR of the lungs compared to Gd-DTPA (21±8 vs. 13±3). Contrast-enhanced 3D perfusion MRI and MRA of PE can be combined using a single injection of the blood pool contrast agent Gadomer.     

Single-photon emission tomography of a computerised model of pulmonary embolism

Planar pulmonary scintigraphy is currently the standard investigation for the diagnosis of pulmonary embolism. There are a number of problems with the technique, particularly in patients with an intermediate scan report under the PIOPED criteria. The technique is also under threat from the increasing use of spiral CT angiography. A putative improvement may be gained by use of tomography. The incremental value of tomography over planar studies was therefore evaluated in a virtual model of pulmonary scintigraphy. A model of the segmental anatomy of the lungs was developed from computed tomography, cadaveric human lungs and available anatomical texts. Counts were generated within the phantom by Monte Carlo simulation of photon emission. Eighteen single segmental lesions were interspersed with 47 subsegmental defects and displayed on an Icon reporting station. These were presented in the transaxial, sagittal and coronal planes to four experienced reporters to obtain assessment of defect size. Planar studies of the same defects were displayed to the same observers in the standard eight views with a normal study for comparison. With planar studies, the accuracy of estimation of defect size was 51% compared with 97% using tomographic studies. Defects in the medial basal segment of the right lower lobe were not identified in planar studies but were easily seen by all observers in the tomographic study. It is concluded that there is marked improvement in the accuracy of determination of defect size for tomographic studies over the planar equivalents. This is especially important in the lung bases, the most common reported site of pulmonary emboli. Tomography permits visualisation of defects in the medial basal segment of the right lung, which are not seen in planar studies. Received 5 March and in revised form 1 June 1999