Pulmonary arterial hypertension: diagnosis with fast perfusion MR imaging and high-spatial-resolution MR angiography--preliminary experience

PURPOSE: To determine prospectively the accuracy of a magnetic resonance (MR) perfusion imaging and MR angiography protocol for differentiation of chronic thromboembolic pulmonary arterial hypertension (CTEPH) and primary pulmonary hypertension (PPH) by using parallel acquisition techniques. MATERIALS AND METHODS: The study was approved by the institution's internal review board, and all patients gave written consent prior to participation. A total of 29 patients (16 women; mean age, 54 years +/- 17 [+/- standard deviation]; 13 men; mean age, 57 years +/- 15) with known pulmonary hypertension were examined with a 1.5-T MR imager. MR perfusion imaging (temporal resolution, 1.1 seconds per phase) and MR angiography (matrix, 512; voxel size, 1.0 x 0.7 x 1.6 mm) were performed with parallel acquisition techniques. Dynamic perfusion images and reformatted three-dimensional MR angiograms were analyzed for occlusive and nonocclusive changes of the pulmonary arteries, including perfusion defects, caliber irregularities, and intravascular thrombi. MR perfusion imaging results were compared with those of radionuclide perfusion scintigraphy, and MR angiography results were compared with those of digital subtraction angiography (DSA) and/or contrast material-enhanced multi-detector row computed tomography (CT). Sensitivity, specificity, and diagnostic accuracy of MR perfusion imaging and MR angiography were calculated. Receiver operator characteristic analyses were performed to compare the diagnostic value of MR angiography, MR perfusion imaging, and both modalities combined. For MR angiography and MR perfusion imaging, kappa values were used to assess interobserver agreement. RESULTS: A correct diagnosis was made in 26 (90%) of 29 patients by using this comprehensive MR imaging protocol. Results of MR perfusion imaging demonstrated 79% agreement (ie, identical diagnosis on a per-patient basis) with those of perfusion scintigraphy, and results of MR angiography demonstrated 86% agreement with those of DSA and/or CT angiography. Interobserver agreement was good for both MR perfusion imaging and MR angiography (kappa = 0.63 and 0.70, respectively). CONCLUSION: The combination of fast MR perfusion imaging and high-spatial-resolution MR angiography with parallel acquisition techniques enables the differentiation of PPH from CTEPH with high accuracy.     

Prospective comparison of MR lung perfusion and lung scintigraphy

This study attempted to assess the accuracy and potential of lung magnetic resonance (MR) perfusion imaging compared with perfusion scintigraphy in the evaluation of patients with suspected lung perfusion defects. The technique, which uses an inversion recovery turbo-FLASH sequence with ultra-short TE (1.4 msec), was tested in 24 patients suspected clinically of having acute pulmonary embolism (n = 19) and in patients with severe pulmonary emphysema (n = 5). Perfusion lung scintigraphy was performed within 48 hours prior to the MRI examination in both groups of patients. The dynamic study was acquired in the coronal plane and consisted of 10 images of 6 slices (a total of 60 images per series). Gadopentetate dimeglumine (0.1 mmol/kg) was manually injected as a compact bolus during the acquisition of the first image. Three senior radiologists reviewed all unprocessed two-dimensional coronal sections. They were blinded to clinical data and other imaging modalities. For the three observers, the average sensitivity and specificity of MR were 69% and 91%, respectively. The overall agreement between MR and scintigraphy appears to be good, with a good correlation between the two modalities (kappa = 0.63). However, the data showed variability depending on the location of the perfusion defect, with higher accuracy in the upper lobes. The agreement between MR perfusion and scintigraphy appears to be moderate in the left inferior lobe (kappa = 0.48). The data showed an overall good interobserver agreement (kappa = 0.66). MR perfusion of the lung is a promising technique in detecting lung perfusion defects.     

Accuracy and feasibility of dynamic contrast-enhanced 3D MR imaging in the assessment of lung perfusion: comparison with Tc-99 MAA perfusion scintigraphy

AIM: The aim of this study was to correlate findings of perfusion magnetic resonance imaging (MRI) and perfusion scintigraphy in cases where there was a suspicion of abnormal pulmonary vasculature, and to evaluate the usefulness of MRI in the detection of perfusion deficits of the lung. METHODS: In all, 17 patients with suspected abnormality of the pulmonary vasculature underwent dynamic contrast-enhanced MRI. T1-weighted 3D fast-field echo pulse sequences were obtained (TR/TE 3.3/1.58 ms; flip angle 30 degrees; slice thickness 12 to 15 mm). The dynamic study was acquired in the coronal plane following administration of 0.1 mmol/kg gadopentetate dimeglumine. A total of 8 to 10 sections repeated 20 to 25 times at intervals of 1s were performed. Perfusion lung scintigraphy was carried out a maximum of 48 h before the MR examination in all cases. Two radiologists, who were blinded to the clinical data and results of other imaging methods, reviewed all coronal sections. MR perfusion images were independently assessed in terms of segmental or lobar perfusion defects in the 85 lobes of the 17 individuals, and the findings were compared with the results of scintigraphy. RESULTS: Of the 17 patients, 8 were found to have pulmonary emboli, 2 chronic obstructive pulmonary disease with emphysema, 2 bullous emphysema, 2 Takayasu arteritis and 1 had a hypoplastic pulmonary artery. Pulmonary perfusion was completely normal in 2 cases. In 35 lobes, perfusion defects were detected using both methods, in 4 with MR alone and in 9 only with scintigraphy. There was good agreement between MRI and scintigraphy findings (kappa=0.695). CONCLUSION: Pulmonary perfusion MRI is a new alternative to scintigraphy in the evaluation of pulmonary perfusion for various lung disorders. In addition, this technique allows measurement and quantification of pulmonary perfusion abnormalities.     

Detectability of pulmonary perfusion defect and influence of breath holding on contrast-enhanced thick-slice 2D and on 3D MR pulmonary perfusion images.

The present study assesses the detectability of perfusion defect and the influence of breathhold on pulmonary magnetic resonance (MR) perfusion imaging using contrast-enhanced thick-slice two-dimensional (2D) fast gradient-echo sequence compared with three-dimensional (3D) fast spoiled gradient-recalled sequence. Dynamic studies were performed in 16 patients. MR perfusion images were interpreted by two independent observers using perfusion scintigraphy as the reference standard. The patients were divided into two groups according to the duration of holding the breath measured during MR imaging. The sensitivity and specificity of 2D MR perfusion imaging in detecting perfusion defects were 93% and 94%, respectively, while those of 3D MR perfusion imaging were 89% and 85%, respectively. The diagnostic accuracy of 2D MR perfusion imaging was significantly higher than that of 3D MR perfusion imaging (P < 0.05) among those who could not hold their breath. Therefore, 2D MR perfusion imaging offers promise for evaluating pulmonary perfusion even among patients who cannot hold their breath.     

Perfusion abnormalities in pulmonary embolism studied with perfusion MRI and ventilation-perfusion scintigraphy: an intra-modality and inter-modality agreement study

PURPOSE: To compare perfusion magnetic resonance imaging (MRI) and ventilation-perfusion scintigraphy (V-P scan) in the study of perfusion abnormalities in pulmonary embolism (PE) and to compare the PE results to the findings previously reported for pneumonia and chronic obstructive pulmonary disease (COPD), in terms of perfusion abnormalities. MATERIALS AND METHODS: Dynamic contrast-enhanced MR images and V-P scans of 20 patients with PE, 11 patients with acute pneumonia, and 13 patients with exacerbation of COPD were studied. Five categories of perfusion abnormalities within each imaging modality were defined. Intra- and inter-modality agreement (kappa values) in the evaluation of perfusion abnormalities were calculated, based on the two observers of each imaging modality (all blinded to each other and true diagnosis). Finally, three categories of perfusion MRI diagnosis (PE, pneumonia, and COPD) were also defined and the inter-observer agreement (kappa value) was calculated. RESULTS: For PE, the intra-modality agreement (kappa value) in the evaluation of perfusion abnormalities was 0.77 for MRI and 0.65 for V-P scan. The inter-modality agreement varied from 0.52 to 0.57, respectively, and was observer-dependent. For the pooled group of PE, pneumonia, and COPD, the intra-modality agreement of perfusion abnormalities was 0.76 for MRI and 0.65 for V-P scan, and the inter-modality agreement varied from 0.51 to 0.56. The kappa value for inter-observer agreement for MRI diagnosis was 0.92. CONCLUSION: Evaluation of perfusion abnormalities in PE, pneumonia, and COPD using perfusion MRI and V-P scan showed a high intra-modality agreement that was higher than the inter-modality agreement. Further studies are now needed in patients presenting with possible PE to evaluate the sensitivity and specificity of the method.     

Coronary artery imaging with real-time navigator three-dimensional turbo-field-echo MR coronary angiography: initial experience

PURPOSE: To examine the value of a commercially available three-dimensional (3D) real-time navigator magnetic resonance (MR) coronary angiographic examination for detection of significant coronary artery stenoses, with conventional coronary angiography as the standard of reference. MATERIALS AND METHODS: Twenty-one patients underwent 3D navigator MR coronary angiography immediately before catheterization. Two observers independently graded image quality on a scale from 1 (unreadable) to 5 (excellent), quantified coronary artery visualization, and evaluated the presence of significant (ie, >50% narrowing) stenoses. kappa statistics were used to assess interobserver agreement, and receiver operating characteristic (ROC) analysis was used to assess stenosis detection. RESULTS: For two of 21 patients, MR coronary angiogram quality was insufficient for analysis (mean score < 2). For the remaining 19 patients, the mean image quality scores assigned by observers 1 and 2 were 3.3 +/- 1.0 (SD) and 3.2 +/- 0.9, respectively. A mean of 71% of all coronary artery segments were visible at MR coronary angiography, and there was 91% agreement between the observers (kappa = 0.78). Observers 1 and 2 detected significant stenoses (n = 29) at MR coronary angiography with sensitivities of 44.4% and 55.5%, respectively; specificities of 95.1% and 83.7%, respectively; and 80% agreement (kappa = 0.35). Areas under the ROC curve were 0.817 and 0.795 for observers 1 and 2, respectively. CONCLUSION: Large portions of the coronary arteries can be visualized with MR coronary angiography. Imaging results are not consistently reliable, however. The examination is premature for routine clinical assessment of significant coronary artery stenosis owing to low sensitivity and large observer variability.     

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.     

Interobserver agreement for the interpretation of contrast-enhanced 3D MR angiography and MDCT angiography in peripheral arterial disease

OBJECTIVE: The objective of our study was to compare interobserver agreement for interpretations of contrast-enhanced 3D MR angiography and MDCT angiography in patients with peripheral arterial disease. SUBJECTS AND METHODS: Of 226 eligible patients, 69 were excluded. The remaining 157 consecutive patients were prospectively randomized to either MR angiography (n = 78) or MDCT angiography (n = 79). Two observers independently evaluated for arterial stenosis or occlusion on MR angiography (2,157 segments) and MDCT angiography (2,419 segments) using a 5-point ordinal scale. Vessel wall calcifications were noted. Interobserver agreement for each technique was evaluated with a weighted kappa (kappa(w)) statistic. RESULTS: Although interobserver agreement for both was excellent, the interobserver agreement for MR angiography (kappa(w) = 0.90; 95% confidence interval [CI], 0.89-0.92) was higher than that for MDCT angiography (kappa(w) = 0.85; 95% CI, 0.83-0.86) for reporting the degree of arterial stenosis or occlusion in all segments. For the different anatomic locations, the interobserver agreement for MR angiography versus MDCT angiography was as follows: aortoiliac (kappa(w) =0.91 vs 0.84, respectively), femoropopliteal (kappa(w) = 0.91 vs 0.87), and crural (kappa(w) = 0.90 vs 0.83) segments. The interobserver agreement of MDCT angiography significantly decreased in the presence of calcifications but was still good for all anatomic locations. The lowest agreement was found for crural segments in the presence of calcifications (kappa(w) = 0.67). With MR angiography, there were 12 times more nondiagnostic segments than with MDCT angiography (81 vs 7, respectively). CONCLUSION: Interpretations of MR angiography and MDCT angiography for peripheral arterial disease have an excellent interobserver agreement. MR angiography has a higher interobserver agreement than MDCT angiography, and the presence of calcified segments significantly decreases interobserver agreement for MDCT angiography.     

Feasibility of combining MR perfusion, angiography, and 3He ventilation imaging for evaluation of lung function in a porcine model

RATIONALE AND OBJECTIVE: To assess the feasibility of combining magnetic resonance (MR) perfusion, angiography, and 3He ventilation imaging for the evaluation of lung function in a porcine model. MATERIALS AND METHODS: Fourteen consecutive porcine models with externally delivered pulmonary emboli and/or airway occlusions were examined with MR perfusion, angiography, and 3He ventilation imaging. Ultrafast gradient-echo sequences were used for 3D perfusion and angiographic imaging, in conjunction with the use of contrast-agent injections. 2D multiple-section 3He imaging was performed subsequently via the inhalation of hyperpolarized 3He gas. The diagnostic accuracy of MR angiography for detecting pulmonary emboli was determined by two reviewers. The diagnostic confidence for different combinations of MR techniques was rated on the basis of a 5-point grading scale (5 = definite). RESULTS: The sensitivity, specificity, and accuracy of MR angiography for detecting pulmonary emboli were approximately 85.7%, 90.5%, and 88.1%, respectively. The interobserver agreement was very strong (k = 0.82). There was a clear tendency for confidence to increase when first perfusion and then ventilation imaging were added to the angiographic image (Wilcoxon signed ranks test, P = 0.03). CONCLUSION: The combination of the three methods of MR perfusion, angiography, and 3H ventilation imaging may provide complementary information on abnormal lung anatomy and function.     

Evaluation of patients undergoing lung volume reduction surgery: ancillary information available from computed tomography

AIM: A number of imaging techniques have been used for the pre-operative assessment of patients for lung volume reduction surgery (LVRS). We evaluated whether data currently acquired from perfusion scintigrams and cine MR of the diaphragm are obtainable from high resolution CT (HRCT) of the thorax. MATERIALS AND METHODS: Thirty patients taking part in a randomized controlled trial of LVRS against maximal medical therapy were evaluated. HRCT examinations (n= 30) were scored for (i) the extent and distribution of emphysema; (ii) the extent of normal pulmonary vasculature; and (iii) diaphragmatic contour, apparent defects and herniation. On scintigraphy, (n= 28), perfusion of the lower thirds of both lungs, as a proportion of total lung perfusion (LZ/T(PERF)), was expressed as a percentage of predicted values (derived from 10 normal control subjects). On cine MR (n= 25) hemidiaphragmatic excursion and coordination were recorded. RESULTS: Extensive emphysema was present on HRCT (60% +/- 13.2%). There was strong correlation between the extent of normal pulmonary vasculature on HRCT and on perfusion scanning (r(s)= 0.85, P< 0.00005). Hemidiaphragmatic incoordination on MR was weakly associated with hemidiaphragmatic eventration on HRCT (P= 0.04). CONCLUSION: The strong correlation between lung perfusion assessed by HRCT and lung perfusion on scintigraphy suggests that perfusion scintigraphy is superfluous in the pre-operative evaluation of patients with emphysema for LVRS.     

Regional lung perfusion: assessment with partially parallel three-dimensional MR imaging

PURPOSE: To evaluate partially parallel three-dimensional (3D) magnetic resonance (MR) imaging for assessment of regional lung perfusion in healthy volunteers and patients suspected of having lung cancer or metastasis. MATERIALS AND METHODS: Seven healthy volunteers and 20 patients suspected of having lung cancer or metastasis were examined with 3D gradient-echo MR imaging with partially parallel image acquisitions (fast low-angle shot 3D imaging; repetition time msec/echo time msec, 1.9/0.8; flip angle, 40 degrees; acceleration factor, two; number of reference k-space lines for calibration, 24; field of view, 500 x 440 mm; matrix, 256 x 123; slab thickness, 160 mm; number of partitions, 32; voxel size, 3.6 x 2.0 x 5.0 mm(3); acquisition time, 1.5 seconds) after administration of 0.1 mmol/kg of gadobenate dimeglumine. In volunteers, 3D MR perfusion data sets were assessed for topographic and temporal distribution of regional lung perfusion. Sensitivity, specificity, accuracy, and positive and negative predictive values for perfusion MR imaging for detecting perfusion abnormalities in patients were calculated, with conventional radionuclide perfusion scintigraphy as the standard of reference. Interobserver and intermodality agreement was determined by using kappa statistics. RESULTS: Topographic analysis of lung perfusion in volunteers revealed a significantly higher signal-to-noise ratio (SNR) of up to 327% in gravity-dependent lung areas. Temporal analysis similarly revealed much shorter lag time to peak enhancement in gravity-dependent lung areas. In patients, perfusion MR imaging achieved high sensitivity (88%-94%), specificity (100%), and accuracy (90%-95%) for detection of perfusion abnormalities. Interobserver agreement (kappa = 0.86) was very good and intermodality agreement (kappa = 0.69-0.83) was good to very good for detection of perfusion defects. A significant difference (P <.0001) in SNR was observed between normally perfused lung (14 +/- 7 [SD]) and perfusion defects (7 +/- 4) in patients. CONCLUSION: Partially parallel MR imaging with high spatial and temporal resolution allows assessment of regional lung perfusion and has high diagnostic accuracy for detecting perfusion abnormalities.     

Dual energy CT for the assessment of lung perfusion—Correlation to scintigraphy

Purpose of this study was to determine the diagnostic value of dual energy CT in the assessment of pulmonary perfusion with reference to pulmonary perfusion scintigraphy.Thirteen patients received both dual energy CT (DECT) angiography (Somatom Definition, Siemens) and ventilation/perfusion scintigraphy. Median time between scans was 3 days (range, 0–90). DECT perfusion maps were generated based on the spectral properties of iodine. Two blinded observes assessed DECT angiograms, perfusion maps and scintigrams for presence and location of perfusion defects. The results were compared by patient and by segment, and diagnostic accuracy of DECT perfusion imaging was calculated regarding scintigraphy as standard of reference.Diagnostic accuracy per patient showed 75% sensitivity, 80% specificity and a negative predictive value of 66%. Sensitivity per segment amounted to 83% with 99% specificity, with 93% negative predictive value. Peripheral parts of the lungs were not completely covered by the 80 kVp detector in 85% of patients. CTA identified corresponding emboli in 66% of patients with concordant perfusion defects in DECT and scintigraphy.Dual energy CT perfusion imaging is able to display pulmonary perfusion defects with good agreement to scintigraphic findings. DECT can provide a pulmonary CT angiogram, high-resolution morphology of the lung parenchyma and perfusion information in one single exam.     

MR肺通气联合灌注成像的动物模型研究

目的 探讨氧增强MR肺通气成像联合肺灌注成像诊断气道阻塞和肺栓塞(PE)病变的可行性和价值。方法 对8只犬通过肺段动脉水平注入凝胶海绵颗粒复制周围型PE模型，其中5只经自制球囊导管插入二级气道又建立气道阻塞模型。通过吸纯氧前后的图像减影可获得氧增强MR肺通气图像。利用对比剂首次通过法可进行MR肺灌注成像。观察MR肺通气和灌注成像的表现，并与大体病理解剖、核素肺通气-灌注成像和肺血管造影进行对照。结果 MR肺通气和灌注成像在气道阻塞区的表现相匹配，但在肺栓塞区不匹配。气道阻塞区在MR肺通气成像中的缺损区域小于核素肺通气成像。根据信号强度随时间变化曲线，肺灌注异常区可分为灌注缺损和减低区。MR肺通气联合灌注成像诊断肺栓塞的敏感度和特异度分别为75．0％和98．1％；其诊断结果与核素肺通气一灌注成像和肺血管造影的一致性较好(K=0．743、0．899)。结论 氧增强MR肺通气成像联合肺灌注成像可用来诊断肺内气道和血管异常，该方法与核素肺通气-灌注成像类似，并能提供量化的功能信息和更高的时间、空间分辨率，具有临床应用价值。     

MR angiography as a screening tool for intracranial aneurysms: feasibility, test characteristics, and interobserver agreement

OBJECTIVE: MR angiography may be an appropriate tool to screen for unruptured intracranial aneurysms. Feasibility, test characteristics, and interobserver agreement in evaluation of MR angiograms were assessed by members of the MARS (Magnetic resonance Angiography in Relatives of patients with Subarachnoid hemorrhage) Study Group. SUBJECTS AND METHODS: We screened 626 first-degree relatives of a consecutive series of 193 patients with subarachnoid hemorrhage examined at two institutions. We used MR imaging and MR angiography (three-dimensional time-of-flight imaging at both institutions and additional three-dimensional phase-contrast imaging at one institution). Three observers independently assessed the MR angiograms. Conventional angiography was performed in relatives with possible or definite aneurysms on MR angiography and was considered the standard of reference. RESULTS: Thirty-three aneurysms were found in 25 (4%; 95% confidence interval [CI], 3-6%) of 626 relatives. Thirteen (8%) of 169 relatives who refused screening had MR-related reasons; an additional six persons could not be screened because of contraindications for MR imaging (pregnancy, n = 1; claustrophobia, n = 5). The positive predictive value of MR angiography was 100% (95% CI, 79-100%) for "definite" aneurysms and 58% (95% CI, 28-85%) for "possible" aneurysms. Sensitivity of MR angiography was estimated at 83% (95% CI, 65-94%) and specificity at 97% (95% CI, 94-98%). Interobserver agreement in the evaluation of MR angiograms was poor (kappa < .30), probably because different diagnostic strategies used by individual observers resulted in different use of the assessment category "possible aneurysm." CONCLUSION: MR angiography is a feasible screening tool for detection of intracranial aneurysms. Positive predictive value, sensitivity, and specificity are acceptable when at least two neuroradiologists independently assess MR angiograms.     

Dual energy CT for the assessment of lung perfusion--correlation to scintigraphy

Purpose of this study was to determine the diagnostic value of dual energy CT in the assessment of pulmonary perfusion with reference to pulmonary perfusion scintigraphy. Thirteen patients received both dual energy CT (DECT) angiography (Somatom Definition, Siemens) and ventilation/perfusion scintigraphy. Median time between scans was 3 days (range, 0-90). DECT perfusion maps were generated based on the spectral properties of iodine. Two blinded observes assessed DECT angiograms, perfusion maps and scintigrams for presence and location of perfusion defects. The results were compared by patient and by segment, and diagnostic accuracy of DECT perfusion imaging was calculated regarding scintigraphy as standard of reference. Diagnostic accuracy per patient showed 75% sensitivity, 80% specificity and a negative predictive value of 66%. Sensitivity per segment amounted to 83% with 99% specificity, with 93% negative predictive value. Peripheral parts of the lungs were not completely covered by the 80 kVp detector in 85% of patients. CTA identified corresponding emboli in 66% of patients with concordant perfusion defects in DECT and scintigraphy. Dual energy CT perfusion imaging is able to display pulmonary perfusion defects with good agreement to scintigraphic findings. DECT can provide a pulmonary CT angiogram, high-resolution morphology of the lung parenchyma and perfusion information in one single exam.     

Using gadolinium-enhanced three-dimensional MR angiography to assess arterial inflow stenosis after kidney transplantation

OBJECTIVE: Our objective was to evaluate use of gadolinium-enhanced three-dimensional (3D) MR angiography in the assessment of suspected arterial inflow stenosis after kidney transplantation. SUBJECTS AND METHODS: Twenty-eight consecutive patients receiving kidney transplants (26 single-kidney transplants and two en block transplants) with suspected arterial inflow stenosis were examined with two MR angiography sequences: gadolinium-enhanced 3D fast spoiled gradient-recalled (SPGR) imaging and 3D phase-contrast imaging. Twenty-four of these patients then were examined using the gold standards: either digital subtraction angiography (DSA) (n = 23) or surgery (n = 1). MR angiography and DSA studies were independently and prospectively analyzed for the presence of arterial stenoses (mild [<50%], severe [50-90%], or critical [>90%]) in the iliac, anastomotic, and renal artery segments. Two independent observers retrospectively evaluated the MR angiography sequences for ability to detect or exclude significant (> or = 50%) arterial stenoses. RESULTS: In 22 single-kidney transplants, DSA showed eight significant stenoses in 66 arterial segments. MR angiograms adequately showed 66 of 66 segments (prospective observers) and 64 of 66 segments (each retrospective observer), which were subsequently evaluated. The sensitivity and specificity of MR angiography in revealing significant stenoses were 100% and 98% (prospective analysis), 88% and 98% (retrospective observer 1), and 86% and 100% (retrospective observer 2). Concordance between observers showed kappa values exceeding .85 for all comparisons except the analysis of phase-contrast series (kappa = .62). In one en block transplant, DSA showed that stenosis was greater than 90%, although it had been graded at less than 50% with MR angiography. CONCLUSION: Gadolinium-enhanced 3D MR angiography accurately evaluated arterial inflow in single-kidney transplants.     

Cine-gradient-refocused MR imaging of central pulmonary emboli

We studied the use of MR imaging with a limited-flip-angle, gradient-refocused pulse sequence to show central pulmonary emboli in 11 patients and to distinguish acute from chronic emboli. The central pulmonary vasculature was imaged by using a cine-limited-flip-angle (cine-MR) pulse sequence with 63/13 (TR/TE) and a 30 degrees flip angle (theta), as well as standard spin-echo sequences. Patients were selected on the basis of suspicion of central pulmonary embolism and correlative studies done within 24 hr of the MR examination. Correlations with other studies were based on the original MR report and blinded review of the MR images by two observers in consensus. Emboli were shown in all cases by cine-MR, and they corresponded to the locations of angiographic abnormalities and mismatched perfusion defects on scintigraphy. In three patients considered to have acute pulmonary embolus on the basis of angiography, the cine-MR studies were consistent with acute pulmonary embolus in two patients and chronic pulmonary embolus in one patient (however, in that patient pathologic examination showed chronic embolism). In one case in which angiography led to the diagnosis of acute and chronic pulmonary embolism, the cine-MR study showed acute embolism. In three patients thought to have chronic pulmonary embolus on the basis of angiography, the cine-MR study was interpreted as representing acute embolus in one patient and chronic embolus in two patients. In this highly selected, small group of patients, cine-MR imaging was accurate in showing central pulmonary embolism.     

Quantitatively assessed dynamic contrast-enhanced magnetic resonance imaging in patients with chronic obstructive pulmonary disease: correlation of perfusion parameters with pulmonary function test and quantitative computed tomography

OBJECTIVES: The purpose of this study is to evaluate the correlation of the perfusion parameters of 3-dimensional, contrast-enhanced magnetic resonance (MR) imaging (3D CEMRI) with pulmonary function test (PFT) and quantitative computed tomography (CT) parameters in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: In 14 patients with COPD, 3D CEMRI was performed. From the signal intensity-time curves, pulmonary blood flow (PBF), pulmonary blood volume (PBV), and mean transit time of each pixel was calculated. From the volumetric CT data, the quantitative parameters including the volume fraction of the lung below -950 Housefield Units (V(-950)) and mean lung density were assessed. The correlation between the MR perfusion parameters and the parameters from quantitative CT and PFT was assessed using Spearman correlation analysis. The correspondence of the regional impairment of perfusion on MR perfusion maps to the areas of emphysema on quantitative CT maps in each patient was assessed qualitatively using a 4-class visual scoring method by 2 readers. RESULTS: All 3D CEMRI examinations were successfully completed and MR perfusion parameters were obtained in all patients. The Spearman correlation test showed that PBF positively correlated with forced expiratory volume in 1 second (FEV(1))/forced vital capacity (FVC) (R = 0.49, P = 0.044), PBV positively correlated with FEV(1)/FVC (R = 0.69, P = 0.006) and negatively correlated with V-950 (R = -0.61, P = 0.020), and mean transit time positively correlated with FEV(1) (R = 0.63, P = 0.017) and FEV(1)/FVC (R = 0.76, P = 0.002). The areas of perfusion impairment on PBF and PBV maps were relatively well correlated with the areas of emphysema on CT maps [very good or good: PBF 71.5% (reader 1) and 64.3% (reader 2) of the patients, kappa = 0.47 (P < 0.001); PBV 78.6% (reader 1) and 78.6% (reader 2) of the patients, kappa = 0.89 (P < 0.001)]. CONCLUSIONS: This study shows that the deterioration of perfusion parameters measured on MR in patients with COPD, correlates with worsening of airflow limitation on PFT and emphysema index on CT. Regional heterogeneity of emphysema on CT matches with the decreased perfusion on MR.     

Gadolinium-enhanced MR angiography of the breast: Is breast cancer associated with ipsilateral higher vascularity?

The aim of this study was to assess a possible association between breast malignancy and ipsilateral higher vascularity on gadolinium-enhanced MR angiography. One hundred six patients were examined by dynamic gadolinium-enhanced 3D MR imaging. Magnetic resonance angiographic views were generated by image subtraction and maximum intensity projection. The study included 85 patients with unilateral malignant breast neoplasms and 21 with unilateral benign lesions. Three blinded readers independently reviewed the MR angiograms after masking the lesions and the corresponding contralateral sites. The readers were asked to determine whether vascularity was higher on the right side, higher on the left side, or equal on both sides. The results were analyzed by the Kappa statistic and Pearson's chi-square test. The blood vessels of the breasts were clearly seen in all cases. There was good agreement among the observers (kappa > 0.54 ) in assessing vascularity on both sides. Breasts harboring malignant neoplasms were found to have a higher vascularity than the contralateral breasts (p < 0.005). This sign of malignancy had a sensitivity of 76.5 %, a specificity of 57 %, and an accuracy of 72.6 %. Blood vessels of the breast can be depicted by MR angiography. Unilateral malignant neoplasms are associated with a higher ipsilateral vascularity. In conjunction with other indications of malignancy on gadolinium-enhanced MR images, a higher ipsilateral vascularity may serve as an additional sign of malignancy. Received: 4 April 2000 Revised: 14 August 2000 Accepted: 18 August 2000     

Prospective comparison of helical CT and MR imaging in clinically suspected acute pulmonary embolism

The purpose of this study is to compare sensitivity and specificity of helical CT and MR imaging for detecting acute pulmonary embolism (PE). Patients who were suspected clinically of having PE were randomly assigned to undergo either helical contrast-enhanced CT or gradient-echo MR (if one modality was contraindicated, the patient was assigned to the other). Patients were considered to have PE if they had: (1) high-probability V-Q scan and high clinical probability of PE; or (2) pulmonary angiogram positive for PE. Patients were considered not to have PE if they had either: (1) normal V-Q scan; (2) low probability V-Q scan and low clinical probability of PE; or (3) pulmonary angiogram negative for PE. The CT and MR images were read randomly and independently by five radiologists with varying levels of CT and MR experience. Twenty eight patients underwent CT and 25 MR. A total of 21 patients underwent pulmonary angiography (6 had PE, 15 did not have PE). Of the other 32 patients, 15 had high probability scan/high clinical probability and 17 had low probability scan/low clinical probability. For the five observers, the average sensitivity of CT was 75% and of MR 46%; the average specificity of CT was 89% and of MR 90%. Experience with vascular MR and enhanced CT influenced diagnostic accuracy. For the two vascular MR experts, average sensitivity and specificity of MR were 71% and 97%, and of CT 73% and 97%. In this pilot study, when CT and MR were interpreted with comparable expertise, they had similar accuracy for detecting pulmonary embolism.