Does pregnancy affect vascular enhancement in patients undergoing CT pulmonary angiography?

The aim of this study was to evaluate whether pregnancy affects contrast enhancement within the pulmonary arteries during computed tomography pulmonary angiography (CTPA). This was a retrospective analysis of the CTPA examinations of 16 pregnant and 16 non-pregnant female patients, suspected of having an acute pulmonary embolus (PE), during the same time period. Pulmonary vascular enhancement was evaluated by measuring the CT density within the pulmonary arteries. In a blinded evaluation, subjective grading of contrast enhancement within the pulmonary arteries was also performed. There was a significant difference in arterial enhancement between the two groups, with pregnant patients having a mean pulmonary arterial density 112 HU less than patients in the control group [mean attenuation of 259.79 ± 59.31 HU in pregnant patients versus 371.88 ± 60.63 HU in non-pregnant patients (p < 0.001)]. The mean subjective pulmonary arterial enhancement score in the pregnant group was 8.19 ± 2.51 versus 13.69 ± 3.07 in the control group (p < 0.001). Pregnant women undergoing CTPA have significantly decreased pulmonary arterial enhancement compared to non-pregnant patients, probably due to the increase in cardiac output in pregnancy. We may need to reconsider how we perform CTPA in this group in order to ensure adequate opacification for diagnosis.     

Pulmonary perfusion: Qualitative assessment with dynamic contrast-enhanced MRI using ultra-short TE and inversion recovery turbo FLASH

The accurate assessment of pulmonary perfusion is especially important in the evaluation of patients with suspected pulmonary embolism, a common and potentially lethal disorder that can be treated by aggressive anticoagulation. In this study, we demonstrate for the first time the use of MR to image pulmonary perfusion in humans by using dynamic imaging after contrast administration. The technique, which uses an inversion recovery turbo FLASH sequence with ultrashort TE (1.4 ms) and 1-s temporal resolution, was tested in a series of eight healthy subjects and in a porcine model of pulmonary embolism. After the administration of gadopentetate dimeglumine in humans and animal models, there was serial enhancement of the systemic veins, right atrium, right ventricle, and pulmonary arteries. The pulmonary arterial tree was visualized beyond the segmental branches, followed by a gradual diffuse increase in signal intensity of the lung parenchyma over a period of 4.0–7.0 s. Pulmonary circulation times ranged from 3.0–3.4 s. Whereas a high dose (20 or 40 ml) of contrast agent tended to produce the most intense parenchymal enhancement, a low dose (5 ml) was best for showing recirculation. In the animal model, a perfusion defect due to a pulmonary embolus was clearly shown and confirmed by cine angiography. It is concluded that MRI of lung perfusion is feasible. With further development, perfusion MRI could eventually have a significant clinical role in the diagnostic evaluation of pulmonary embolism.     

Waiting to exhale: salvaging the nondiagnostic CT pulmonary angiogram by using expiratory imaging to improve contrast dynamics

We attempted to investigate whether computed tomography pulmonary angiography (CTPA) in the expiratory phase can improve contrast enhancement of the pulmonary arteries and mitigate the effect of inspiratory transient attenuation artifact, potentially salvaging nondiagnostic studies. Eighteen patients with indeterminate inspiratory CTPA, despite proper contrast bolus were studied. Patients were rescanned in expiration using the same contrast bolus and scanning parameters. The attenuation of each pulmonary arterial segment, superior and inferior vena cava, and atria and ventricles during the two phases of respiration was measured independently by three radiologists. All pulmonary segments were evaluated for filling defects during the two phases. In addition, the studies were graded for diagnostic quality of enhancement and probable impact on management. A statistically significant increase in pulmonary arterial enhancement was seen during expiration from the pulmonary trunk to the segmental pulmonary arteries (P < 0.001) and for the inferior vena cava, the right atrium, and the ventricle. The incidence of nondiagnostic inspiratory studies ranged from 89 to 100%, depending on the observer. All studies were upgraded to fully acceptable diagnostic quality with follow-up expiratory imaging (P < 0.0001). Expiratory phase imaging was observed to have diagnostic impact in 78 to 88% of cases, with overall good to moderate interobserver agreement. In one case, pulmonary embolism was detected on the expiratory scan, which was not seen on the inspiratory scan. Expiratory imaging for nondiagnostic CTPA improves pulmonary arterial enhancement and improves diagnostic quality of CTPA by eliminating transient attenuation artifact, thus facilitating more accurate diagnosis and providing earlier treatment of pulmonary embolism.     

室间隔缺损合并肺动脉高压的肺血管分级与血流动力学的关系

对30例室间隔缺损合并肺动脉高压的病例血流动力学指标进行了测定,并对肺血管的病理改变进行了分级。结果发现:肺血管病理改变的程度与肺血流量呈负相关(P<0.01);与肺动脉压呈正相关(P<0.05);与肺血管阻力也呈正相关(P<0.01)。术前应用硝普钠可使肺动脉压明显下降(P<0.01)。因此,依据血流动力学指标有利于选择病例,并可望对肺血管的病理改变及术后恢复情况作出估计。     

Diagnostik der akuten Lungenembolie

Pulmonary embolism is an acute and potentially life-threatening condition requiring a differentiated diagnostic algorithm. Assessment of the risk and clinical probability are of utmost importance in order to initiate early treatment or to reliably exclude a pulmonary embolism. Computed tomography of the pulmonary arteries (CTPA) has become the non-invasive gold standard for the diagnostic approach. Alternatively, scintigraphy can also be used. A negative CTPA excludes a pulmonary embolism with a high degree of probability. Furthermore, CTPA can supply additional information, such as estimation of the right ventricular strain (right ventricular dysfunction, RVD) or alternative diagnoses if pulmonary embolism has been ruled out as the primary cause of symptoms. An essential prerequisite is a high quality CTPA with sufficient contrast enhancement in the pulmonary arteries, avoidance of artifacts and optimization of both the radiation dosage as well as the amount of contrast medium, individually determined for each patient.     

Spiral CT of pulmonary embolism: diagnostic approach, interpretive pitfalls and current indications

The introduction of spiral CT has recently modified the diagnostic work-up of pulmonary embolism, because it is possible to depict noninvasively endoluminal clots in second- to-fourth-division pulmonary arteries. If this technique is currently considered a powerful imaging alternative for the detection of acute central emboli, it is mainly related to the possibility to obtain a uniform and high degree of arterial enhancement of pulmonary arteries down to 2–3 mm in diameter. Minimal experience in spiral CT angiography is necessary to achieve this goal and requires familiarity with both data acquisition and contrast medium injection. Numerous interpretive pitfalls exist in assessing spiral CT images, and certain caveats have to be heeded. However, their recognition becomes increasingly less problematic as the radiologist gains experience with spiral CT of the pulmonary vasculature. Therefore, the purpose of this article is to review the diagnostic approach to pulmonary embolism with spiral CT, with special emphasis on protocol parameters and scan interpretation. Received 21 January 1998; Accepted 4 February 1998     

Value of pulmonary vein wedge angiography in visualization of obstructed ipsilateral pulmonary artery

Left ventricular cineangiogram in a 2-year-old child with a large ventricular septal defect, pulmonary atresia and a previous Waterston anastomosis opacified clearly the right pulmonary artery but the left pulmonary artery could not be visualized. The later was thought to be due to obstruction or kinking of the right pulmonary artery proximal to the Waterston anastomotic site. A left pulmonary vein wedge angiogram performed via a No. 5 end-hole catheter with 4.0 cc of meglumine diatrizoate (75% Hypaque) injected under pressure (less than 100 PSI) visualized the left pulmonary artery in a retrograde fashion. The size of the left pulmonary artery at this study was comparable to its size measured at the time of a subsequent left Blalock-Taussig anastomosis. Pulmonary vein wedge angiography with 0.3 cc/kg body weight of contrast material injected over a two second period (less than 100 PSI) appears to be a useful technique in demonstrating the pulmonary arteries when these cannot be visualized by conventional antegrade techniques.     

Gadomer-17-enhanced 3D navigator-echo MR angiography of the pulmonary arteries in pigs

The goal of this study was visualisation and quality assessment of the pulmonary arteries in pigs with modified navigator-echo magnetic resonance angiography using an intravascular contrast agent. Five sedated pigs were examined in a clinical 1.5-T system with modified three-dimensional navigator-echo magnetic resonance angiography (slice thickness 3 mm, pixel size 2.4x1.8 mm2) to evaluate the pulmonary arteries. Using a phased-array four-element thorax coil the entire thorax was scanned before and after intravenous infusion of a gadolinium-based intravascular contrast agent. Assessment of image quality, enhancement-related contrast-to-noise ratio (CNR) measurements and improvement of visibility of peripheral pulmonary vessels was performed. Improvement of quality using Gadomer-17 was found for smaller vessels; pulmonary trunks and the main pulmonary arteries were sufficiently imaged without enhancement. Mean rise of CNR measured in the pulmonary trunks was 28.64% ( P=0.0002), mean rise of CNR in the main pulmonary arteries and the segmental arteries were 79.6% and 148.2%, respectively. Mean distance between the visible peripheral end of 60 sub-segmental arteries and the inner thoracic wall was 12.2 +/- 0.4 mm, and was significantly ( P=0.00002) reduced after contrast infusion to 8.0 +/- 0.4 mm. The combination of inherent flow sensitivity of navigator-echo angiography and Gadomer-17 proved effective for imaging of the pulmonary arteries. In contrast to standard contrast-enhanced pulmonary MRA studies, breath holding is not required. Further studies and the evaluation of findings of patients suffering from pulmonary embolism are needed to evaluate the possible benefits of a higher spatial resolution which is achievable using navigator-echo techniques in contrast to the higher temporal resolution of ultra-fast pulmonary MRA.     

MSCTA对肺周围病变侵犯段以下肺动脉的诊断价值

目的：探讨MSCTA对肺周围病变侵犯段以下肺动脉的诊断价值。方法：对362例肺周围病变行16层螺旋CT肺动脉造影,对其中段以下肺动脉受侵犯且经病理证实的35例进行分析。结果：段以下肺动脉可疑侵犯5例（良性2例,恶性3例）;轻度侵犯18例（良性1例,恶性17例）;重度侵犯12例（良性0例,恶性12例）。肺动脉轻重度侵犯对恶性病变的诊断准确率达96.7%,但肺动脉侵犯程度与良恶性结果间无显著性差异（P〉0.05）。结论：16层螺旋CT肺动脉造影能很好地显示周围病变侵犯段或亚段肺动脉的部位和程度,对诊断恶性病变具有重要参考价值。     

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。     

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。     

Intravenous contrast material administration at high-pitch dual-source CT pulmonary angiography: test bolus versus bolus-tracking technique

Purpose

To compare test bolus and bolus tracking for the determination of scan delay of high-pitch dual-source CT pulmonary angiography in patients with suspected pulmonary embolism using 50 ml of contrast material.

Materials and methods

Data of 80 consecutive patients referred for CT pulmonary angiography were evaluated. All scans were performed on a 128-channel dual-source CT scanner with a high-pitch protocol (pitch 3.0, 100 kV, 180 mA s). Contrast enhancement was achieved by injecting 50 ml of iomeprol followed by a saline chaser of 50 ml injected at a rate of 4 ml/s. The scan delay was determined using either the test bolus (n = 40) or bolus tracking (n = 40) technique. Test bolus required another 15 ml CM to determine time to peak enhancement of the contrast bolus within the pulmonary trunk. Attenuation profiles in the pulmonary trunk and on segmental level as well as in the ascending aorta were measured to evaluate the timing techniques. Additionally, overall image quality was evaluated.

Results

In all patients an adequate and homogeneous contrast enhancement of more than 250 HU was achieved in the pulmonary arteries. No statistically significant difference between test bolus and bolus tracking was found regarding attenuation of the pulmonary arteries or overall image quality. However, using bolus tracking 15 ml CM less was injected.

Conclusion

A homogeneous opacification of the pulmonary arteries and sufficient image quality can be achieved with both the bolus tracking and test bolus techniques with significant lower contrast doses compared to conventional contrast material injection protocols.     

MSCT增强扫描方式的优化对肺孤立小结节的诊断价值

目的:探讨MSCT肺部3期增强扫描方式对肺部孤立性小结节(SPN)的诊断价值。方法:收集30例应用改进的增强扫描方式(即3期扫描)检查的SPN患者的影像资料。3期扫描包括动脉期30 s,静脉期60 s,平衡期120 s,分析SPN的强化程度及增强方式,并绘制时间-密度曲线。结果:通过曲线首尾两点做直线,对照发现,代表慢性炎症的直线斜率要大于代表肺癌的直线斜率。肺癌和慢性炎症通过肺3期增强扫描,CT值增长幅度较大,肺癌增强扫描后最大增长值平均为25 HU,且一般会均匀强化,慢性炎症为35 HU,且一般为周边强化明显;结核增长幅度不大,平均为10.9 HU,且一般中央不强化。结论:通过3期增强扫描,结核比较容易区分,而肺癌和慢性炎症因为增长幅度都较大,增强CT值之间有交叉,所以通过时间-密度曲线首尾两点做直线,其斜率可对慢性炎症和肺癌进行鉴别诊断。     

Unilateral pulmonary vein atresia: Literature overview and case report

The unilateral absence of the pulmonary vein, known as pulmonary vein atresia, is a rare type of unilateral pulmonary venous hypoplasia caused by the congenital atrophy of the long pulmonary vein segments in one lung. The involved lung may be normal in size or present with hypoplasia and is often characterized by increased interstitial attenuation and interlobular septal thickening due to venous stasis, edema, and fibrosis. Pulmonary angiography often reveals a reduced size for the lateral pulmonary artery, peripherally sparse pulmonary vessels, contrast stasis, and the inability to visualize pulmonary veins. Symptoms include coughing up blood and infection. We present the clinical case of a patient who was initially diagnosed with recurrent hemoptysis due to pulmonary tuberculosis, followed by unsuccessful treatment. Imaging by 64-slice computed tomography with contrast injection using multiplanar reformation and volume rendering techniques allowed this case to be definitively diagnosed. This report emphasizes the epidemiological factors and clinical and imaging features of unilateral pulmonary vein atresia to prevent confusion and facilitate proper diagnosis in similar cases.     

16层螺旋CT肺血管造影对亚段肺栓塞诊断的成像技术探讨

目的:研究16层螺旋CT肺血管造影在急性肺动脉栓塞(PE)诊断中的应用价值。着重探讨亚段水平周围型肺栓塞的适宜扫描参数及显示方法。方法:应用16层螺旋CT扫描机(GE ligtspeed 16)对临床拟诊肺栓塞的42例患者进行前瞻性研究。依据患者屏气时间长短,设定3组扫描参数。结果:CT诊断肺栓塞31例。中央型22例,周围型9例。3组扫描参数均可清晰显示亚段水平肺动脉栓子。高质量扫描模式肺动脉CTA成像质量最高,常规扫描模式次之,高速扫描模式再次之。结论:16层螺旋CT肺血管造影快速、无创、敏感性、特异性高。选择适宜扫描参数及显示方法,急性肺栓塞诊断可以达到亚段水平。2组常规扫描模式更为适宜PE患者。     

三种心血管造影组合对肺动脉闭锁肺动脉发育情况的评价分析

目的评价分析三种心血管造影组合显示肺动脉闭锁合并室间隔缺损的肺动脉发育情况。资料与方法回顾性分析22例肺动脉闭锁合并室间隔缺损患者的临床资料,包括X线平片、心电图、超声心动图和心血管造影。重点分析三种造影组合对显示肺动脉发育情况的优缺点。结果（1）右心室造影＋楔入肺静脉造影共3例,均显示左右肺动脉融合,一侧肺动脉发育细小。（2）右心室造影＋弓降部主动脉和／或升主动脉造影共15例,其中11例主要由未闭动脉导管供血,均见左右肺动脉融合,融合部狭窄3例,一侧或双侧肺动脉发育不良或变细8例,2例可见主肺动脉及盲端;另4例左右不融合。（3）右心室造影＋弓降部主动脉或升主动脉造影＋体肺侧支血管造影共4例,其中1例由细小动脉导管供血,左右肺动脉融合并发育较好;3例均由小体肺侧支和网状细小血管供血,肺动脉发育细小。结论三种心血管造影组合均能有效显示肺动脉发育情况,主动脉造影能全面了解体肺侧支血管分布,选择性侧支血管造影是术前栓塞所必要的;楔入肺静脉造影可极好地显示纵隔内肺动脉的情况。     

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.     

Lymphomatoid Granulomatosis: CT and FDG-PET Findings

Objective

Lymphomatoid granulomatosis (LG) is a rare, aggressive extranodal Epstein-Barr virus (EBV)-positive B-cell lymphoproliferative disease. The purpose of our study was to analyze the CT and fluorodeoxyglucose positron emission tomography (FDG-PET) findings of pulmonary LG.

Materials and Methods

Between 2000 and 2009, four patients with pathologically proven pulmonary LG and chest CT were identified. Two of these patients also had FDG-PET. Imaging features of LG on CT and PET were reviewed.

Results

Pulmonary nodules or masses with peribronchovascular, subpleural, and lower lung zonal preponderance were present in all patients. Central low attenuation (4 of 4 patients), ground-glass halo (3 of 4 patients), and peripheral enhancement (4 of 4 patients) were observed in these nodules and masses. An air-bronchogram and cavitation were seen in three of four patients. FDG-PET scans demonstrated avid FDG uptake in the pulmonary nodules and masses.

Conclusion

Pulmonary LG presents with nodules and masses with a lymphatic distribution, as would be expected for a lymphoproliferative disease. However, central low attenuation, ground-glass halo and peripheral enhancement of the nodules/masses are likely related to the angioinvasive nature of this disease. Peripheral enhancement and ground-glass halo, in particular, are valuable characteristic not previously reported that can help radiologists suggest the diagnosis of pulmonary LG.     

CTPA for the diagnosis of acute pulmonary embolism during pregnancy

CT pulmonary angiography (CTPA) has been suggested by the Fleischner society as the first test following a negative leg ultrasound in pregnant patients with suspected pulmonary embolism. This editorial discusses the use of CTPA as a diagnostic tool in pregnant women and comments on the need for specifically adapting CT protocols during pregnancy in the light of new research describing a substantial number of non-diagnostic examinations in pregnant women if routine scanning protocols are used for CTA of the pulmonary arteries. Potential reasons for these high numbers of insufficient examinations are physiological changes occurring during pregnancy that lead to a hyperdynamic circulation, which reduces average enhancement of the pulmonary vasculature. In addition, there are possible breathing-related effects that include an increased risk for Valsalva manoeuvre with devastating effects for pulmonary vascular enhancement. Techniques to overcome these problems are discussed: bolus triggering with short start delays, high flow rates or high contrast medium concentration, preferential use of fast CT systems and the use of low kVp CT techniques. CT data acquisition during deep inspiration should be avoided and shallow respiration may be considered as an alternative to suspended breathing in this patient group. All these factors can contribute to optimization of the quality of pulmonary CTA in pregnant patients. It is time now to adapt our protocols and provide optimum care for this sensitive patient group.     

Pulmonary hemorrhage: Imaging with a new magnetic resonance blood pool agent in conjunction with breathheld three-dimensional magnetic resonance angiography

Purpose: To describe the three-dimensional magnetic resonance angiography (3D MRA) imaging appearance of the pulmonary arteries following administration of a superparamagnetic iron oxide blood pool agent to human volunteers, and to demonstrate in an animal model (pigs) how this technique can be used to detect pulmonary parenchymal hemorrhage. Methods: Two volunteers were examined following the intravenous administration of a superparamagnetic iron oxide blood pool agent (NC100150 Injection, Nycomed Amersham Imaging, Wayne, PA, USA). T1-weighted 3D gradient recalled echo (GRE) image sets (TR/TE 5.1/1.4 msec, flip angle 30°) were acquired breathheld over 24 sec. To assess the detectability of pulmonary bleeding with intravascular MR contrast, pulmonary parenchymal injuries were created in two animals under general anesthesia, and fast T1-weighted 3D GRE image sets collected before and after the injury. Results: Administration of the intravascular contrast in the two volunteers resulted in selective enhancement of the pulmonary vasculature permitting complete visualization and excellent delineation of central, segmental, and subsegmental arteries. Following iatrogenic injury in the two animals, pulmonary hemorrhage was readily detected on the 3D image sets. Conclusion: The data presented illustrate that ultrafast 3D GRE MR imaging in conjunction with an intravenously administered intravascular blood pool agent can be used to perform high-quality pulmonary MRA as well as to detect pulmonary hemorrhage.