Outcome of acute ischemic lesions evaluated by diffusion and perfusion MR imaging.

BACKGROUND AND PURPOSE: Diffusion and perfusion MR imaging have been reported to be valuable in the diagnosis of acute ischemia. Our purpose was to ascertain the value of these techniques in the prediction of ischemic injury and estimation of infarction size, as determined on follow-up examinations. METHODS: We studied 18 patients with acute ischemic stroke who underwent echo-planar perfusion and diffusion imaging within 72 hours of symptom onset. Quantitative volume measurements of ischemic lesions were derived from relative mean transit time (rMTT) maps, relative cerebral blood volume (rCBV) maps, and/or apparent diffusion coefficient (ADC) maps. Follow-up examinations were performed to verify clinical suspicion of infarction and to calculate the true infarction size. RESULTS: Twenty-five ischemic lesions were detected during the acute phase, and 14 of these were confirmed as infarcts on follow-up images. Both ADC and rMTT maps had a higher sensitivity (86%) than the rCBV map (79%), and the rCBV map had the highest specificity (91%) for detection of infarction as judged on follow-up images. The rMTT and ADC maps tended to overestimate infarction size (by 282% and 182%, respectively), whereas the rCBV map appeared to be more precise (117%). Significant differences were found between ADC and rMTT maps, and between rCBV and rMTT maps. CONCLUSION: Our data indicate that all three techniques are sensitive in detecting early ischemic injury within 72 hours of symptom onset but tend to overestimate the true infarction size. The best methods for detecting ischemic injury and for estimating infarction size appear to be the ADC map and the rCBV map, respectively, and the diffusion abnormality may indicate early changes of both reversible and irreversible ischemia.     

Prebolus quantitative MR heart perfusion imaging.

The purpose of this study was to present the prebolus technique for quantitative multislice myocardial perfusion imaging. In quantitative MR perfusion studies the maximum contrast agent dose is limited by the requirement to determine the arterial input function (AIF). The prebolus technique consists of two consecutive contrast agent administrations. The AIF is determined from a first low-dose bolus, while a second, high-dose bolus allows the measurement of the myocardium with improved signal increase. The results of the prebolus technique using a multislice saturation recovery trueFISP sequence in healthy volunteers are presented. In comparison to a standard dose of 3 ml Gd-DTPA, perfusion values are maintained while the signal increase in the concentration time courses was considerably improved, accompanied by reduced standard deviations of the obtained perfusion values (0.72 +/- 0.13 ml/g/min for 1 ml/8 ml and 0.67 +/- 0.10 ml/g/min for 1 ml/12 ml Gd-DTPA, respectively).     

Malignant versus benign mediastinal lesions: quantitative assessment with diffusion weighted MR imaging

Objectives  

We aimed to evaluate the performance of diffusion-weighted magnetic resonance imaging in differentiating malignant from benign mediastinal lesions.     

MR扩散加权成像定量分析对纵隔良恶性病变的鉴别诊断

目的探讨MR扩散加权成像对纵隔良恶性病变的鉴别诊断价值。材料与方法对53例纵隔病变进行传统的T1WI和T2WI,并在b=0和b=1000s/mm2下行扩散加权成像,计算其表观扩散系数ADC值。用t检验对这两组ADC值     

Assessing tissue viability with MR diffusion and perfusion imaging

BACKGROUND AND PURPOSE: Diffusion- (DW) and perfusion-weighted (PW) MR imaging reflect neurophysiologic changes during stroke evolution. We sought to determine parameters that distinguish regions of brain destined for infarction from those that will survive despite hypoperfusion. METHODS: DW and PW images were obtained in 30 patients at 1-12 hours after symptom onset. Relative cerebral blood volume (rCBV), flow (rCBF), mean transit time (MTT), apparent diffusion coefficient (ADC), DW image signal intensity, and fractional anisotropy (FA) lesion-contralateral normal region ratios were obtained in the following regions: 1) infarct core with hyperintensity on DW image, abnormality on rCBF and MTT images, and follow-up abnormality; 2) infarcted penumbra with normal DW image, abnormal rCBF and MTT images, and follow-up abnormality; and 3) hypoperfused tissue that remained viable, with normal DW image, abnormal rCBF and MTT images, and normal follow-up. RESULTS: rCBF ratios for regions 1, 2, and 3 were 0.32 +/- 0.11, 0.46 +/- 0.13, and 0.58 +/- 0.12, respectively, and were significantly different. DW image intensity and ADC ratios were significantly different among all regions, but were more similar than rCBF ratios. rCBV and FA ratios were not significantly different between regions 2 and 3. No MTT ratios were significantly different. No region of interest with an rCBF ratio less than 0.36, an rCBV ratio less than 0.53, an ADC ratio less than 0.85, a DW image intensity ratio greater than 1.23, or an FA ratio greater than 1.10 remained viable. No region of interest with an rCBF ratio greater than 0.79 infarcted. CONCLUSIONS: Differences among mean ratios of three regions investigated were greatest for the rCBF ratio. The rCBF ratio may be the most useful parameter in differentiating viable tissue that is likely to infarct without intervention, from tissue that will survive despite hypoperfusion. ADC, DW intensity, FA, and rCBV ratios may provide adjunctive information.     

一站式能谱及灌注成像鉴别诊断孤立性肺结节

目的：探讨一站式能谱及灌注成像在孤立性肺结节(SPN)鉴别诊断中的应用价值。方法47例接受一站式能谱及灌注成像且经病理证实为 SPN 患者分为恶性组(28例)、良性组(19例),分别测量肺内病灶的血容量(BV)、血流量(BF)、平均通过时间(MTT)、表面通透性(PS)数值及动、静脉期的碘浓度(IC)、标准碘浓度(NIC)、能谱曲线斜率(40~100 keV)。采用独立样本 t 检验的方法,比较2组各参数间的差异。结果恶性结节的灌注参数 BF、BV、PS 值高于良性结节,有显著性差异(P <0.05),恶性结节 MTT 与良性结节无显著性差异(P>0.05);肺恶性结节动、静脉期 IC、NIC、能谱曲线斜率均高于良性结节,有显著性差异(P<0.05)。结论一站式能谱及灌注成像技术具有实现能谱及灌注成像同时完成的优势,可提供更多参数,在 SPN 鉴别诊断中具有一定应用价值。     

CT灌注成像对孤立性肺结节的定性诊断价值

目的：探讨多层螺旋CT灌注成像（CTPI）在孤立性肺结节良恶性鉴别诊断中的临床应用价值。方法：直径≤3 cm的SPN患者35例（其中恶性结节25例,良性结节10例）进行前瞻性CT灌注成像研究,先行全肺层厚为10 mm螺旋CT扫描,然后对病灶进行灌注扫描。选择同层面主动脉为灌注动脉,分别测得SPN的血流量（BF）、血容量（BV）、平均通过时间（MTT）和表面通透性（PS）并拟合时间-密度曲线（TDC）,结合增强前后SPN的形态学指标进行综合分析。结果：恶性结节的BF、BV、MTT和PS值分别为（146.17±58.77）ml/100 mg、（6.45±1.38）ml/（100g.min）、（5.09±3.19）s和（16.33±6.62）ml/（100g.min）,良性结节的BF、BV、MTT和PS值分别为（69.90±58.09）ml/100 mg、（3.88±1.81）ml/（100g.min）、（4.06±1.77）s、（6.18±3.55）ml/（100g.min）。良、恶性SPN的TDC类型不同,恶性SPN的TDC可见A、B、C三型,其中以A型和C型为主（21/25,84.0%）;良性SPN的TDC以D型（无明显强化型）为主。良、恶性SPN的增强峰值、增强净增值比较差异有统计学意义（P〈0.05）;而良、恶性结节的平扫CT值差异无统计学意义（P〉0.05）;以净增值≥25 HU为诊断恶性结节的阈值,其敏感度、特异度及符合率分别为88.9%、80.0%、84.2%。结论：CT-PI扫描可反映SPN内的血流动力学特征,结合SPN的形态学特征可提高SPN鉴别诊断的敏感性和准确性。     

Actinomycotic brain infection: registered diffusion, perfusion MR imaging and MR spectroscopy

Introduction: Actinomycotic brain infection is caused by an organism of the Actinomyces genus. We report here one such case. Methods: The methods used included coregistered diffusion, perfusion and spectroscopic magnetic resonance (MR) imaging. Results: Decreased apparent diffusion coefficient, markedly elevated fractional anisotropy (FA) and reduced cerebral blood flow were observed. MR spectroscopy demonstrated elevated amino acids, acetate and succinate. Conclusion: Elevated FA values may be due to the microstructure of this special brain infection.     

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。     

MR perfusion, diffusion and BOLD imaging of methotrexate-exposed swine brain

PURPOSE: To evaluate the methotrexate (MTX)-exposed swine brain, functional magnetic resonance imaging (MRI), including perfusion, diffusion, and blood-oxygen-level-dependent (BOLD) contrast imaging, was used. MATERIAL AND METHODS: Juvenile pigs received either 2 x 5 g/m(2), or 5 x 2 g/m(2) MTX intravenously within one month. MRI was performed (sedative: propofol) before (14-17 kg, N = 6) and after (21-27 kg, N = 4) the MTX exposure. Also, age-matched controls (22-27 kg, N = 4) were imaged. RESULTS: After the MTX exposure, reduced (from 2%-4% to 0%-1%) or negative (-2% to -3%) BOLD responses were detected; apparent diffusion coefficient (ADC) or relative perfusion values did not change. CONCLUSION: This study suggests that MTX-related changes in the brain may be detected as changes in flow-metabolism coupling as reduced or negative response (for somatosensory activation) in the BOLD contrast MRI. The contrast agent perfusion MRI, without absolute quantification, may not show global damage in brain perfusion related to the MTX exposure in the swine model used. ADC (in one direction) may not indicate MTX-related changes in the brain.     

Separation of diffusion and perfusion in intravoxel incoherent motion MR imaging

Intravoxel incoherent motion (IVIM) imaging is a method the authors developed to visualize microscopic motions of water. In biologic tissues, these motions include molecular diffusion and microcirculation of blood in the capillary network. IVIM images are quantified by an apparent diffusion coefficient (ADC), which integrates the effects of both diffusion and perfusion. The aim of this work was to demonstrate how much perfusion contributes to the ADC and to present a method for obtaining separate images of diffusion and perfusion. Images were obtained at 0.5 T with high-resolution multisection sequences and without the use of contrast material. Results in a phantom made of resin microspheres demonstrated the ability of the method to separately evaluate diffusion and perfusion. The method was then applied in patients with brain and bone tumors and brain ischemia. Clinical results showed significant promise of the method for tissue characterization by perfusion patterns and for functional studies in the evaluation of the microcirculation in physiologic and pathologic conditions, as, for instance, in brain ischemia.     

First-pass perfusion imaging of solitary pulmonary nodules with 64-detector row CT: comparison of perfusion parameters of malignant and benign lesions

The purpose of this study was to determine the usefulness of first-pass whole nodule perfusion imaging in the differentiation of benign and malignant solitary pulmonary nodules (SPNs). 77 patients with non-calcified SPNs (46 malignant, 22 benign and 9 active inflammatory) underwent first-pass perfusion imaging with a 64-detector row CT scanner. Perfusion, peak enhancement intensity (PEI), time to peak (TTP) and blood volume (BV) were measured and statistically compared among different groups. Mean perfusion, PEI and BV for benign SPNs were significantly lower than those for malignant nodules (p<0.05) and active infections (p<0.05), but the differences were not statistically significant between malignant tumours and active infections (p>0.05). Receiver operating characteristic (ROC) curve analysis showed that SPNs with perfusion greater than 30.6 ml min^–1 ml^–1, PEI higher than 23.3 HU or BV larger than 12.2 ml per 100 g were more likely to be malignant. In conclusion, first-pass perfusion imaging with 64-detector row CT is a feasible way of assessing whole nodule perfusion and helpful in differentiating benign from malignant SPNs.The differentiation of solitary pulmonary nodules (SPNs) as benign or malignant remains a diagnostic challenge for thoracic radiology. During the past decade, promising results for more specific differentiation of malignant and benign nodules using dynamic contrast material-enhanced CT have been reported [1–6]. Techniques in these studies rely on single-level acquisition with long time intervals, which were considered to be problematic for quantitative assessment of whole tumour perfusion because the blood flow within tumours is spatially and temporally heterogeneous [7, 8]. Nevertheless, current technological advances in multidetector row CT (MDCT), specifically sequential volume acquisition and data processing, allow for more accurate evaluation of tissue haemodynamics than that attainable with previous CT techniques. A recent study on MDCT perfusion techniques assessed whole tumour perfusion with the volume coverage of 40 mm in patients with non-small-cell lung carcinoma and achieved good measurement reproducibility [8]. To the best of our knowledge, no data exist on the application of first-pass perfusion CT for the differentiation of benign and malignant SPNs [1–6, 8]. The purpose of our study, therefore, was to determine the utility of first-pass whole nodule perfusion imaging in the differentiation of benign and malignant SPNs.     

肺部孤立性病变CT灌注参数与MVD相关性分析

【摘要】目的：探讨肺部孤立性病变多层螺旋CT（MSCT）灌注成像参数与肿瘤微血管密度（MVD）间的关系,评价MSCT灌注成像对肺部孤立性病变的鉴别诊断价值。方法：80例经病理证实的肺部孤立性病变患者行MSCT灌注成像检查,计算血流量（BF）、血容量（BV）、平均通过时间（MTT）、毛细血管通透性（PS）;采用CD34单抗标记测定MVD,分析良、恶性病变、炎性病变、不同分化程度肿瘤组织的CT灌注参数差异及各参数与MVD间的相关性。结果：良、恶性和炎性病变组的BV分别为(3.45±1.75)、（10.40±4.08）、（8.40±8.42）mL/100g;BF分别为(24.48±18.74)、（77.75±43.03）、（84.54±107.13）mL/(100g·min);PS分别为(4.33±2.90)、（21.70±10.86）、（14.67±10.29）mL/(100g·min);MTT分别为(15.54±7.01)、（15.23±13.35）、（12.55±8.39）s。良性组与恶性组、良性组与炎性组BF、BV、PS值差异均具有统计学意义（P＜0.05）;恶性组与炎性组间仅PS差异具有统计学意义（P＜0.05）,MTT均无相关性(P>0.05)。MVD在非小细胞肺癌不同分化程度鉴别方面具有统计学意义。BF、BV、PS与MVD呈正相关(P<0.05),MTT与MVD无相关性(P>0.05)。结论：MSCT灌注成像可间接反映活体肺部孤立性病变血管生成情况,为鉴别肺部孤立性病变良恶性和治疗、预后评估提供依据。     

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     

Predicting cerebral ischemic infarct volume with diffusion and perfusion MR imaging

BACKGROUND AND PURPOSE: Diffusion and perfusion MR imaging have proved useful in the assessment of acute stroke. We evaluated the utility of these techniques in detecting acute ischemic infarction and in predicting final infarct size. METHODS: Diffusion and hemodynamic images were obtained in 134 patients within a mean of 12.3 hours of onset of acute ischemic stroke symptoms. We retrospectively reviewed patient radiology reports to determine the presence or absence of lesion identification on initial diffusion- (DW) and perfusion-weighted (PW) images. Radiologists were not blinded to the initial clinical assessment. For determination of sensitivity and specificity, the final discharge diagnosis was used as the criterion standard. Neurologists were not blinded to the DW or PW imaging findings. In 81 patients, acute lesions were compared with final infarct volumes. RESULTS: Sensitivities of DW imaging and cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) perfusion parameters were 94%, 74%, 84%, and 84%, respectively. Specificities of DW imaging, CBV, CBF, and MTT were 96%, 100%, 96%, and 96%, respectively. Results were similar in 93 patients imaged within 12 hours. In 81 patients with follow-up, regression analysis yielded r(2) = 0.9, slope = 1.24 for DW imaging; r(2) = 0.84, slope = 1.22 for CBV; r(2) = 0.35, slope = 0.44 for CBF; and r(2) = 0.22, slope = 0.32 for MTT, versus follow-up volume. A DW-CBV mismatch predicted additional lesion growth, whereas DW-CBF and DW-MTT mismatches did not. Results were similar in 60 patients imaged within 12 hours. CONCLUSION: Diffusion and hemodynamic images are sensitive and specific for detecting acute infarction. DW imaging and CBV best predict final infarct volume. DW-CBV mismatch predicts lesion growth into the CBV abnormality. CBF and MTT help identify additional tissue with altered perfusion but have lower correlation with final volume.     

Bone marrow diffusion in osteoporosis: evaluation with quantitative MR diffusion imaging

PURPOSE: To determine the diffusion of vertebral body marrow with quantitative MR diffusion imaging and to examine whether differences exist between subjects with postmenopausal osteoporosis and premenopausal control subjects. MATERIALS AND METHODS: A total of 44 consecutive women (mean age, 70 years) with documented bone mineral density (BMD) measured by dual energy x-ray absorptiometry (T-score) and 20 normal subjects (mean age, 28 years) were examined with echo-planar diffusion imaging at 1.5 T using b values of 0, 20, 40, 60, 80, 100, 200, 300, 400, and 500 seconds/mm2. Extravascular diffusion (D) and apparent diffusion coefficient (ADC) were calculated and results from both groups compared. RESULTS: Both D and ADC values tended to decrease with decreasing BMD. Mean D values were significantly lower in postmenopausal women with reduced BMD (0.42 +/- 0.12 x 10(-3) mm2/second) than normal premenopausal women (0.50 +/- 0.09 x 10(-3) mm2/second). Mean ADC values were significantly lower both in subjects with reduced BMD (0.41 +/- 0.10 x 10(-3) mm2/second) and normal BMD (0.43 +/- 0.08 x 10(-3) mm2/second) compared to normal controls (0.49 +/- 0.07 x 10(-3) mm2/second). CONCLUSION: Accumulation of fatty bone marrow associated with osteoporosis is reflected by a decrease in D and ADC. Diffusion imaging may prove useful in the study of osteoporosis.     

孤立性肺结节CT灌注成像技术研究现状与进展

多层螺旋CT灌注成像技术(multi-slice spiral CT perfusion imaging,CTPI)对孤立性肺结节(solitary pulmonary noudules,SPN)的诊断及鉴别诊断已成为近年来研究的热点,CTPI既能提供结节的形态学信息又能提供结节内部血流参数及强化的时间-密度曲线等多种生理学信息,是一种功能成像,目前研究揭示其在SPN的诊断及鉴别诊断中有重要的应用价值.本文着重综述CTPI鉴别SPN的研究进展.     

Correlation of early dynamic CT perfusion imaging with whole-brain MR diffusion and perfusion imaging in acute hemispheric stroke

BACKGROUND AND PURPOSE: Compared with MR imaging, dynamic CT perfusion imaging covers only a fraction of the whole brain. An important assumption is that CT perfusion abnormalities correlate with total ischemic volume. The purpose of our study was to measure the degree of correlation between abnormalities seen on CT perfusion scans and the volumes of abnormality seen on MR diffusion and perfusion images in patients with acute large-vessel stroke. METHODS: Fourteen patients with acute hemispheric stroke symptoms less than 12 hours in duration were studied with single-slice CT perfusion imaging and multislice MR diffusion and perfusion imaging. CT and MR perfusion studies were completed within 2.5 hours of one another (mean, 77 minutes) and were reviewed independently by two neuroradiologists. Hemodynamic parameters included cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). Extents of abnormality on images were compared by using Kendall correlation. RESULTS: Statistically significant correlation was found between CT-CBF and MR-CBF abnormalities (tau = 0.60, P =.003) and CT-MTT and MR-MTT abnormalities (tau = 0.65, P =.001). Correlation of CT-CBV with MR-CBV approached significance (tau = 0.39, P =.06). Extent of initial hyperintensity on diffusion-weighted images correlated best with extent of MR-CBV abnormality (tau = 0.69, P =.001), extent of MR-MTT abnormality (tau = 0.67, P =.002), and extent of CT-CBV abnormality (tau = 0.47, P =.02). CONCLUSION: Good correlation was seen between CT and MR for CBF and MTT abnormalities. It remains uncertain whether CT perfusion CBV abnormalities correspond well to whole-brain abnormalities.