Abnormalities in the recirculation phase of contrast agent bolus passage in cerebral gliomas: comparison with relative blood volume and tumor grade

BACKGROUND AND PURPOSE: Abnormalities in the recirculation phase of the passage of a contrast agent bolus have been identified in tumors and have been suggested to represent vascular tortuosity and hypoperfusion in areas of angiogenic neovascularization. This study was performed to examine the hypothesis that these abnormalities provide information concerning the microcirculation related to tumor grade in patients with cerebral glioma. METHODS: Contrast-enhanced dynamic susceptibility MR imaging was performed in 27 patients with glioma. Residual relaxivity effects were minimized by injection of contrast agent before dynamic imaging. Maps of relative cerebral blood volume (rCBV) and relative recirculation (rR) were calculated, and values from enhancing tumor tissue were compared with tumor grade. RESULTS: Histologic grades were grade II, astrocytoma (n = 3); grade III, anaplastic astrocytoma (n = 10); and grade IV, glioblastoma multiforme (n = 14). rCBV values varied among tumor grades, with higher mean values in higher grade tumors (P <.001). Mean rR values in grade II tumors were not significantly different from those in normal gray and white matter. Mean rR values in grades III and IV tumors were similar and were significantly higher than those in grade II tumors (P <.01). The distribution of the pixel values of rR showed significant differences between grades III and IV tumors (P <.001), with low values of skewness in keeping with a normal distribution in grade III tumors and higher values in grade IV tumors. CONCLUSION: Variation in the recirculation characteristics of a contrast agent bolus is related to tumor grade in gliomas. This supports the hypothesis that abnormalities in contrast agent recirculation provide independent information concerning the microcirculation in imaging studies of angiogenesis and may be of value as surrogate markers in trials of antiangiogenic therapy.     

MR cerebral blood volume maps correlated with vascular endothelial growth factor expression and tumor grade in nonenhancing gliomas

BACKGROUND AND PURPOSE: Relative cerebral blood volume (rCBV) measurements derived from perfusion-weighted imaging (PWI) may be useful to evaluate angiogenesis and preoperatively estimate the grade of a glioma. We hypothesized that rCBV is correlated with vascular endothelial growth factor (VEGF) expression as marker of the angiogenic stimulus in presumed supratentorial low-grade gliomas (LGGs). METHODS: From February 2001 to February 2004, we examined 20 adults (16 men, four women; mean age 36 years; range, 23-60 years) with suspected (nonenhancing) supratentorial LGG on conventional MR imaging. Preoperative MR imaging used a dynamic first-pass gadolinium-enhanced, spin-echo echo-planar PWI. In heterogeneous tumors, we performed stereotactic biopsy in the high-perfusion areas before surgical resection. Semiquantitative grading of VEGF immunoreactivity was applied. RESULTS: Nine patients had diffuse astrocytomas (World Health Organization grade II), and 11 had other LGG and anaplastic gliomas. In patients with heterogeneous tumors on PWI, the high-rCBV focus had areas of oligodendroglioma or anaplastic astrocytoma on stereotactic biopsy, whereas the surgical specimens were predominantly astrocytomas. Anaplastic gliomas had high rCBV ratios and positive VEGF immunoreactivity. Diffuse astrocytomas had negative VEGF expression and mean rCBV values significantly lower than those of the other two groups. Three diffuse astrocytomas had positive VEGF immunoreactivity and high rCBV values. CONCLUSION: Our results confirmed the correlation among rCBV measurements, VEGF expression, and histopathologic grade in nonenhancing gliomas. PWI may add useful data to the preoperative assessment of nonenhancing gliomas. Its contribution in predicting tumor behavior and patient prognosis remains to be determined.     

胶质瘤CT灌注成像对脑血容量与血管表面通透性的相关性研究

目的应用CT灌注的定量方法对不同级别胶质瘤的脑血容量（CBV）和血管通透性（PS）进行相关性分析，探讨两者在评估胶质瘤术前分级中的作用。方法对19例经手术病理证实的胶质瘤患者进行CT血流灌注成像及常规MR增强扫描，并根据病理分级将患者分为低、高级别两组进行分析。CT原始图像经灌注软件处理获得时间-密度曲线及灌注参数。采用SPSS11．0软件对灌注参数进行Kruskal-Wallis检验及相关性统计学分析。结果低、高级别胶质瘤的CBV中位值分别为2．7、6．5ml／100g，PS中位值分别为0．389、12．810ml·100g^-1·min^-1，差异有统计学意义（t值分别为12．907、13．500，P值均〈0．05）。低、高级别胶质瘤的CBV与PS间Pearson相关系数（r）值分别为-0．058、0．648，仅在高级别组内CBV和PS才存在相关性（P〈0．05）。结论PS和CBV对胶质瘤分级均具明显的相关性，在低级别胶质瘤中CBV与PS无相关性。     

Comparison of cerebral blood volume and vascular permeability from dynamic susceptibility contrast-enhanced perfusion MR imaging with glioma grade

BACKGROUND AND PURPOSE: Relative cerebral blood volume (rCBV) and vascular permeability (K(trans)) permit in vivo assessment of glioma microvasculature. We assessed the associations between rCBV and K(trans) derived from dynamic, susceptibility-weighted, contrast-enhanced (DSC) MR imaging and tumor grade and between rCBV and K(trans). METHODS: Seventy-three patients with primary gliomas underwent conventional and DSC MR imaging. rCBVs were obtained from regions of maximal abnormality for each lesion on rCBV color maps. K(trans) was derived from a pharmacokinetic modeling algorithm. Histopathologic grade was compared with rCBV and K(trans) (Tukey honestly significant difference). Spearman and Pearson correlation factors were determined between rCBV, K(trans), and tumor grade. The diagnostic utility of rCBV and K(trans) in discriminating grade II or III tumors from grade I tumors was assessed by logistic regression. RESULTS: rCBV was significantly different for all three grades (P 相似文献   

Cerebral blood flow,blood volume,and vascular permeability of cerebral glioma assessed with dynamic CT perfusion imaging

We report dynamic CT perfusion imaging assessment of hemodynamics in a patient with a high-grade cerebral glioma and compare our results to those of previously published studies.     

Optimization of fast acquisition methods for whole-brain relative cerebral blood volume (rCBV) mapping with susceptibility contrast agents

Fast gradient-echo magnetic resonance scan techniques with spiral and rectilinear (echoplanar) k-space trajectories were optimized to perform bolus-tracking studies of human brain. Cerebral hemodynamics were studied with full brain coverage, a spatial resolution of 4 mm, and a temporal resolution of 2 seconds. The sensitivity of the techniques to detect image signal-intensity changes during the first pass of the contrast agent was studied at a range of TEs using dedicated experiments. For single-shot versions of spiral scanning and echoplanar imaging techniques with a 0.1-mmol/kg injection of gadolinium diethylenetriamine pentaacetic acid using a mechanical injector at 10 mL/sec under 1.5 T, the maximum sensitivity was obtained at TEs between 35 and 45 msec. At TEs less than 35 msec, signal-intensity artifacts were observed in the images. Analysis of the point-spread function revealed that susceptibility changes induced by the contrast agent can result in signal shifts to neighboring voxels. These artifacts are attributed to susceptibility-related signal changes during the acquisition window.     

Continuous assessment of perfusion by tagging including volume and water extraction (CAPTIVE): A steady-state contrast agent technique for measuring blood flow,relative blood volume fraction,and the water extraction fraction

A new technique, CAPTIVE, that is a synthesis of arterial spin labeling (ASL) blood flow and steady-state susceptibility con trast relative blood volume imaging is described. Using a single injection of a novel, long half-life intravascular magnetopharma-ceutical with a high tissue:blood susceptibility difference (Δ χ) to ΔR1 ratio, changes in tissue transverse relaxivity (ΔR2 or ΔR2*) that arise from changes in blood volume were measured, while preserving the ability to measure blood flow using traditional T₁ -based ASL techniques. This modification permits the contin uous measurement of both blood flow and blood volume. Also, because the contrast agent can be used to remove the signal from intravascular spins, it is possible to measure the first-pass water extraction fraction. Contrast-to-noise is easily traded off with repetition rate, allowing the use of non-EPI scanners and more flexible imaging paradigms. The basic theory of these measurements, several experimental scenarios, and validating results are presented. Specifically, the PaCO₂-reactivity of mi-crovascular and total relative cerebral blood volume (rCBV), ce rebral blood flow (CBF), and the water extraction-flow product (EF) in rats with the new contrast agent MPEG-PL-DyDTPA is measured, and the values are concordant with those of previous literature. As an example of one possible application, continuous flow and volume measurements during transient focal ischemia are presented. It is believed that CAPTIVE imaging will yield a more complete picture of the hemodynamic state of an organ, and has further application for understanding the origins of the BOLD effect.     

Contrast enhancement of manganese-hydroxypropyl-tetraacetic acid, an MR contrast agent with potential for detecting differences in myocardial blood flow

PURPOSE: To determine whether the contrast agent MnHPTA has potential for detecting differences in myocardial blood flow. MATERIALS AND METHODS: R1 in the myocardium was calculated from MR signal intensity measurements in 18 pigs after intravenous injection of 5, 15, or 25 micromol MnHPTA/kg body weight. Measurements were made in each animal after administration at rest and during dobutamine-induced stress. RESULTS: A difference of approximately 0.1 sec-1 in the R1 increase between rest and stress still remained 31 minutes after administration of 25 micromol MnHPTA/kg body weight. When two consecutive MnHPTA injections were performed, the second injection induced a lower R1 increase than the corresponding first injection. CONCLUSION: MnHPTA at a dose of 25 micromol/kg body weight (b.w.) has the potential to detect perfusion differences in myocardium. When two consecutive injections of MnHPTA were administered, the R1 change after the second injection was affected by the earlier administration. Therefore, a protocol including more than one administration is not ideal for this contrast agent.