Relative Cerebral Blood Volume Values Research Articles

Predicting glioblastoma recurrence using multiparametric MR imaging of non-enhancing peritumoral regions at baseline

BackgroundTo assess the feasibility of multiparametric magnetic resonance imaging in predicting tumor recurrence in nonenhancing peritumoral regions in patients with glioblastoma at baseline. MethodsFifty-eight patients with recurrent glioblastoma underwent multiparametric magnetic resonance imaging, including T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging. Nonenhancing peritumoral regions with glioblastoma recurrence were identified by coregistering preoperative and post-recurrent magnetic resonance images. Regions of interest were placed in nonenhancing peritumoral regions with and without tumor recurrence to calculate the apparent diffusion coefficient value, and relative ratios of T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and cerebral blood volume values. ResultsSignificant lower relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative apparent diffusion coefficient but higher relative cerebral blood volume values were found in the nonenhancing peritumoral regions with tumor recurrence than without recurrence (all P < 0.05). The threshold values ≥ 0.89 for relative cerebral blood volume provide the optimal performance for predicting the nonenhancing peritumoral regions with future tumor recurrence, with the sensitivity, specificity, and accuracy of 84.7%, 83.6%, and 85.8%, respectively. The combination of relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative cerebral blood volume can provide better predictive performance than relative cerebral blood volume (P = 0.015). ConclusionThe combined use of T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging can effectively estimate the risk of future tumor recurrence at baseline.

Radiogenomic biomarkers for immunotherapy in glioblastoma: A systematic review of magnetic resonance imaging studies.

Immunotherapy is an effective "precision medicine" treatment for several cancers. Imaging signatures of the underlying genome (radiogenomics) in glioblastoma patients may serve as preoperative biomarkers of the tumor-host immune apparatus. Validated biomarkers would have the potential to stratify patients during immunotherapy clinical trials, and if trials are beneficial, facilitate personalized neo-adjuvant treatment. The increased use of whole genome sequencing data, and the advances in bioinformatics and machine learning make such developments plausible. We performed a systematic review to determine the extent of development and validation of immune-related radiogenomic biomarkers for glioblastoma. A systematic review was performed following PRISMA guidelines using the PubMed, Medline, and Embase databases. Qualitative analysis was performed by incorporating the QUADAS 2 tool and CLAIM checklist. PROSPERO registered: CRD42022340968. Extracted data were insufficiently homogenous to perform a meta-analysis. Nine studies, all retrospective, were included. Biomarkers extracted from magnetic resonance imaging volumes of interest included apparent diffusion coefficient values, relative cerebral blood volume values, and image-derived features. These biomarkers correlated with genomic markers from tumor cells or immune cells or with patient survival. The majority of studies had a high risk of bias and applicability concerns regarding the index test performed. Radiogenomic immune biomarkers have the potential to provide early treatment options to patients with glioblastoma. Targeted immunotherapy, stratified by these biomarkers, has the potential to allow individualized neo-adjuvant precision treatment options in clinical trials. However, there are no prospective studies validating these biomarkers, and interpretation is limited due to study bias with little evidence of generalizability.

Correlation between Perfusion-Weighted Magnetic Resonance Imaging (MRI) Features with Histopathological Grading of Glioma

Background: Gliomas are the most common primary neoplasm of the brain. It histopathologically grades I to IV. I and II are low grade while III, IV are high grade. Low-grade gliomas are usually subject to either strict follow-up or surgery. The treatment for high grade gliomas is typically surgery, followed by concomitant radiation therapy and chemotherapy. Conventional MRI has limitations for the grading of gliomas. In addition to conventional MRI techniques, a variety of new techniques such as perfusion-weighted MRI which noninvasively measures cerebral perfusion that can be used for better assessment of glioma. This will be helpful for therapeutic approach and counseling about prognosis of the patient. Methods: This cross sectional observational study was conducted in the Department of Neurosurgery, Bangabandhu Sheikh Mujib Medical University from IRB clearance to 18 months. The patients who fulfill the selection criteria were enrolled in this study. Written informed consent was taken from the patients and/or the legal guardian/ responsible family members after completely explaining to them the procedure and the purpose of the study. Patient’s data was collected in questionnaire/data collection sheet. The privacy of the patient was strictly maintained and the patient’s information will not be disclosed to any source. The study data will only be used for the purpose of this scientific study. This study was not causing any additional harm to the patients. All the patients were evaluated by a standard conventional contrast-enhanced study with perfusion-weighted image on Siemens 3 Tesla MRI. The histopathological grading of the tumor was done as per the WHO classification of 2007. Then correlation was done between PWI finding and WHO histopathological grading. Results: Measurement of relative cerebral blood volume in glioma patients was done in PW-MRI preoperatively. Out of the 35 tumors evaluated, 17 were found as low rCBV and 18 as high. Histopathological examination of glioma was done postoperatively. Among 35 tumors, 19 are low grade gliomas and 16 are high grade gliomas. For the correlation between relative cerebral blood volume in preoperative PW MRI and histopathological grading of glioma, Spearman’s Rank Correlation Coefficient Test was done. We found a significant positive coefficient value of r = 0.572 with a significant p-value of p = &lt;0.001. A single cutoff relative cerebral blood volume value of 1.7 for low versus high grade glioma was found to be 77.8% sensitive and 88.2% specific. Conclusion: The present study ascertains that histopathological grading of glioma is positively correlated with relative cerebral blood volume in PW MRI. Bang. J Neurosurgery 2022; 12(1): 12-19

DIFFUSION AND PERFUSION WEIGHTED MR IMAGING IN EVALUATION AND CHARACTERIZATION OF BRAIN TUMOURS

DWI and PWI give sufcient non-invasive functional and structural information at the cellular level, emphasising features of the underlying brain pathophysiology. Radiological evaluation of brain tumours done with DWI and PWI parameters using ADC and rCBV values in intra tumoral and peri tumoral region of different brain tumours. Histopathological data was collected and taken as a standard reference for correlation with the diffusion and perfusion parameters of brain tumours. 73 lesions are primary and 17 lesions are secondary out of 90 cases which were diagnosed histo-pathologically. Majority of the high-grade tumours show high relative cerebral blood volume value compared to lower grade tumours and lower ADC values in high grade tumours which is in strong correlation with the HPE analysis. So with DWI and PWI parameters we can conclude on the fact that these imaging techniques are strong and efcient imaging tools to evaluate and characterize brain tumours.

Longitudinal study on MRI and neuropathological findings: Neither DSC-perfusion derived rCBVmax nor vessel densities correlate between newly diagnosed and progressive glioblastoma.

When evaluating MRIs for glioblastoma progression, previous scans are usually included into the review. Nowadays dynamic susceptibility contrast (DSC)-perfusion is an essential component in MR-diagnostics of gliomas, since the extent of hyperperfusion upon first diagnosis correlates with gene expression and survival. We aimed to investigate if this initial perfusion signature also characterizes the glioblastoma at time of progression. If so, DSC-perfusion data from the initial diagnosis could be of diagnostic benefit in follow-up assessments. We retrospectively identified 65 patients with isocitrate dehydrogenase wildtype glioblastoma who had received technically identical DSC-perfusion measurements at initial diagnosis and at time of first progression. We determined maximum relative cerebral blood volume values (rCBVmax) by standardized re-evaluation of the data including leakage correction. In addition, the corresponding tissue samples from 24 patients were examined histologically for the maximum vessel density within the tumor. Differences (paired t-test/ Wilcoxon matched pairs test) and correlations (Spearman) between the measurements at both timepoints were calculated. The rCBVmax was consistently lower at time of progression compared to rCBVmax at time of first diagnosis (p < .001). There was no correlation between the rCBVmax values at both timepoints (r = .12). These findings were reflected in the histological examination, with a lower vessel density in progressive glioblastoma (p = .01) and no correlation between the two timepoints (r = -.07). Our results suggest that the extent of hyperperfusion in glioblastoma at first diagnosis is not a sustaining tumor characteristic. Hence, the rCBVmax at initial diagnosis should be disregarded when reviewing MRIs for glioblastoma progression.

Pseudoprogression in GBM versus true progression in patients with glioblastoma: A multiapproach analysis

Background and purposeTo investigate the feasibility of using a multiapproach analysis combining clinical data, diffusion- and perfusion-weighted imaging, and 3D magnetic resonance spectroscopic imaging to distinguish true tumor progression (TP) from pseudoprogression (PSP) in patients with glioblastoma. Materials and methodsProgression was suspected within 6 months of radiotherapy in 46 of the 180 patients included in the Phase-III SpectroGlio trial (NCT01507506). Choline/creatine (Cho/Cr), choline/N-acetyl aspartate (Cho/NAA) and lactate/N-acetyl aspartate (Lac/NAA) ratios were extracted. Apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) maps were calculated. ADC, relative CBV values and tumor volume (TV) were collected at relapse. Differences between TP and PSP were evaluated using Mann–Whitney tests, and p values were adjusted with Bonferroni correction. ResultsPatients with suspected progression underwent a new MRI scan 1 month after the first one. Of these, 28 were classified as PSP, and 18 as TP. After a median follow-up of 41 months, median overall survival was higher in PSP than in TP (25.2 vs 20.3 months; p = 0.0092). Lac/NAA and Cho/Cr ratios were higher in TP than in PSP (1.2 vs 0.5; p = 0.006; and 3 vs 2.2; p = 0.021). After multivariate regression analysis, TV was the most significant predictor of TP vs PSP, and the only one retained in the model (p = 0.028). ConclusionThree spectroscopic ratios could be used to differentiate PSP from TP. TV at relapse was the most predictive factor in the multivariate analysis, and overall survival was higher in PSP than in TP.

Diagnostic Performance of Dynamic Susceptibility Contrast-Enhanced Perfusion-Weighted Imaging in Differentiating Recurrence From Radiation Injury in Postoperative Glioma: A Meta-analysis.

It is important to differentiate between radiation injury (RI) and tumor recurrence (TR) in patients with glioma after surgery and radiotherapy. Our objective was to evaluate the use of dynamic susceptibility contrast-enhanced perfusion-weighted imaging to distinguish between TR and RI in patients with glioma. Relevant studies published until October 2021 were identified in the PubMed, Embase, and Cochrane Library databases. Stata v12.0 and RevMan 5.3 were used for meta-analysis. In total, the meta-analysis incorporated 13 retrospective studies that included 513 patients with 522 lesions. Among the 522 lesions, 329 lesions were TRs and 193 lesions were RIs. The pooled relative cerebral blood volume value was significantly greater in the TR group ( P < 0.00001) with significant heterogeneity ( I2 = 88%). The pooled sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were 83% (95 confidence interval [CI], 77%-88%), 85% (95 CI, 77%-91%), 5.60 (95 CI, 3.61-8.70), and 0.20 (95% CI, 0.14-0.27), respectively. The heterogeneity of sensitivity ( I2 = 33.18%), specificity ( I2 = 24.01%), PLR ( I2 = 0.00%), and NLR ( I2 = 6.68%) is not significant. The area under the receiver operating characteristic curve was 0.91 (95% CI, 0.88-0.93). The 3.0 T magnetic resonance imaging, high-grade glioma, and Europe/America patient subgroups showed PLR greater than 5 and NLR less than 0.2. There was no significant indication of publication bias in the analysis ( P = 0.496). It is concluded that dynamic susceptibility contrast-enhanced perfusion-weighted imaging is effective for the diagnostic differentiation between TR and RI in patients with glioma.

Apparent Diffusion Coefficient as a Predictive Biomarker for Survival in Patients with Treatment-Naive Glioblastoma Using Quantitative Multiparametric Magnetic Resonance Profiling

The purpose of the present study was to investigate whether quantitative radiomic profiles extracted from multiparametric magnetic resonance (MR) profiles can predict the clinical outcomes for patients with newly diagnosed glioblastoma (GBM) before therapy. MR images from 93 treatment-naive patients with newly diagnosed GBM were analyzed. Through tumor segmentation, we selected 36 radiomic features. Using the unsupervised clustering method, we classified our patients into 2 groups and investigated their overall survival (OS) using Kaplan-Meier analyses. Among the 36 radiomic features, the apparent diffusion coefficient (ADC) histogram parameters demonstrated a significant association with OS (P < 0.05). To validate this finding, unsupervised clustering analysis revealed 3 clusters with similar radiomic expression patterns. Clusters 1 and 2 showed a significant correlation with the radiomic features representing the tumor volume, and cluster 2 also showed a significant correlation with relative cerebral blood volume values. In contrast, cluster 3 showed an inverse relationship with cluster 2, mainly representing the radiomic features indicating the ADC and mean transit time. Although no statistically significant difference was found in OS between cluster 1 plus 2 and cluster 3, cluster 3 showed a trend toward longer OS compared with cluster 1 plus 2 (P= 0.067). After stratification by methylation status and radiomic feature clustering, patients with methylated O6-methylguanine DNA methyltransferase and those included in cluster 3 had significantly longer OS (P= 0.029). ADC histogram parameters are feasible prognostic biomarkers to predict the survival of patients with treatment-naive GBM. Quantitative MR profiles can predict the clinical outcomes of patients with GBM before therapy.

Differentiation of High-grade Gliomas from Brain Metastases Using Tissue Similarity Maps (TSMs) Based Relative Cerebral Blood Volume Values

Background: Perfusion Weighted Imaging (PWI) has been used to differentiate the solitary metastases from high-grade glioma. However, the CBV value obtained from classical algorithm can be affected by a number of factors. Tissue Similarity Map (TSM) is a new algorithm depending solely on the signal intensity time course but does not require the use of Concentration Time Curve (CTC), which is different from the classical rCBV algorithm. Objective: The purpose of this study is to investigate the diagnostic utility of TSM based rCBV values in differentiating between high-grade gliomas and solitary metastases. Methods: The preoperative MR PWI studies of 30 patients with a solitary cerebral neoplasm were retrospectively analyzed. All PWI data were calculated for TSM algorithm with MATLAB 7.6 (Math Works, Natick, MA). The TSM based rCBV (rCBVTSM) were measured in the parenchyma of tumor and peritumoral regions. All specimens were histopathologically categorized as high-grade gliomas or metastases and were correlated with corresponding rCBVTSM values. Results: All PWI data could be post-processed by using the TSM post-processing software. The differences in the rCBVTSM-T between high-grade gliomas and metastases were not statistically significant (p=0.299). While the rCBVTSM-P of high-grade gliomas was higher than that of metastases (p=0.040). ROC curve analysis showed significant AUC of rCBVTSM-P for differentiating highgrade gliomas from metastases (p=0.020). The rCBVTSM-P threshold of 1.725 was found to be a significant cutoff value for high-grade glioma/metastases prediction with 0.619 sensitivity and 0.889 specificity. Conclusion: The rCBVTSM-P derived from MR PWI may be helpful in differentiating high-grade gliomas from solitary metastases. Keywords: TSM, perfusion imaging, cerebral blood volume, glioma, neoplasms metastasis, differentiation diagnosis.

Effects of Pretreatment Cerebral Blood Volume and Time to Recanalization on Clinical Outcomes in Endovascular Thrombectomy for Acute Ischemic Stroke

Faster time to recanalization leads to better clinical outcomes in patients treated with endovascular thrombectomy. Whether the association between time to recanalization and clinical outcomes depends on cerebral blood volume (CBV) obtained from pretreatment computed tomography (CT) perfusion (CTP) imaging was investigated. In consecutive patients with acute ischemic stroke who achieved recanalization by endovascular thrombectomy for intracranial internal carotid artery or M1 occlusion, the effects on clinical outcome of time to recanalization and the relative CBV value (rCBV) assessed by pretreatment CTP were evaluated. The patient population was divided into 2 groups according to rCBV: normal rCBV group (rCBV ≥ .9) and low rCBV group (rCBV < .9). In each group, time to recanalization was compared between the good and the poor clinical outcome groups. Sixty-four patients were eligible for this study. Twenty-six patients (40.6%) achieved good clinical outcomes. In the normal rCBV group, no association was found between clinical outcome and time to recanalization. In the low rCBV group, time to recanalization from CTP (101 minutes versus 136 minutes, P = .040) was significantly shorter in the good clinical outcome group. On binary logistic regression modeling, CTP to recanalization time (odds ratio 1.035 [1.004-1.067], P = .025) was an independent predictor of good clinical outcome only in the low rCBV group. The association between time to recanalization and clinical outcomes depends on rCBV obtained from pretreatment CTP. Time to recanalization is more important for good clinical outcomes in patients with low rCBV than in patients with normal rCBV.

Large decompressive craniectomy combined with vascular reconstruction in patients with severe craniocerebral injury

Aim: This study aims to compare the effect of large decompressive craniectomy combined with vascular reconstruction and traditional decompressive craniectomy in the treatment of severe craniocerebral injury. Methods: Forty-eight cases of severe craniocerebral injury were collected from March 2012 to March 2015 in Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology. Patients undergoing large decompressive craniectomy combined with vascular reconstruction or traditional decompressive craniectomy were randomly divided into two groups: the experimental group and the control group. The hemodynamic changes were observed by computed tomography perfusion, and the postoperative Glasgow Outcome Score (GOS) was analyzed. Results: The cerebral blood flow (CBF) and cerebral blood volume (CBV) scores in experimental group were higher than that in the control group at 1 week and 1 month after the operation (P < 0.05). The mean transit time (MTT) and time to peak (TTP) scores in experimental group were lower than that in the control group at 1 week and 1 month after the operation (P < 0.05). The relative CBF and relative CBV values of the control group in 1 week were higher than that in 1 month, while the relative MTT and relative TTP values in 1 week were lower than that in 1 month. The rate of good recovery (including good and residual cases) in experimental group was higher than that in the control group whereas the rate of poor recovery (including severe disability, vegetative state, and death) in experimental group was lower than that in the control group (P < 0.05). Conclusion: The large decompressive craniectomy combined with vascular reconstruction can not only decrease intracranial pressure but also recover the blood supply of the brain. It deserves the clinical promotion.

Usefulness of quantitative peritumoural perfusion and proton spectroscopic magnetic resonance imaging evaluation in differentiating brain gliomas from solitary brain metastases.

The purpose of our study was to evaluate whether peritumoural perfusion weighted and proton spectroscopic magnetic resonance imaging can be used in differentiating between primary gliomas and solitary metastases. Ten low-grade gliomas, eight high-grade gliomas and 10 metastases were prospectively evaluated with magnetic resonance imaging, dynamic susceptibility contrast enhanced perfusion imaging and single-voxel proton magnetic resonance spectroscopy before surgical resection or stereotactic biopsy. Maximal relative cerebral blood volume values were calculated drawing three regions of interest of 2 cm(2) in the non-enhancing peritumoural areas. Maximal relative cerebral blood volume values were normalised to that of contralateral normal-appearing white matter. Maximal choline/creatine ratios were calculated from three voxels of 10 cm(3) placed in the peritumoural areas defined as non-enhancing peritumoural white matter surrounding the tumour. The tumour grade presumed with these values was compared to histopathological grading. Differences in the study parameters between groups were assessed using the Mann-Whitney test. A receiver operating characteristic analysis was performed to determine cut-off values. A clear relative cerebral blood volume cut-off value of 1.88 was detected for differentiating low-grade gliomas from high-grade gliomas. A clear relative cerebral blood volume cut-off value of 1.20 was detected for differentiation of metastases from gliomas. The differences in the choline/creatine ratios in the peritumoural regions of high-grade gliomas and of solitary metastasis were statistically significant (P < 0.001) but a clear cut-off value was not found. Our preliminary data support the hypothesis that peritumoural perfusion-weighted imaging can assist in preoperative differentiation between a glioma and a solitary metastasis.

Integrative Analysis of mRNA, microRNA, and Protein Correlates of Relative Cerebral Blood Volume Values in GBM Reveals the Role for Modulators of Angiogenesis and Tumor Proliferation.

Dynamic susceptibility contrast-enhanced magnetic resonance imaging is routinely used to provide hemodynamic assessment of brain tumors as a diagnostic as well as a prognostic tool. Recently, it was shown that the relative cerebral blood volume (rCBV), obtained from the contrast-enhancing as well as -nonenhancing portion of glioblastoma (GBM), is strongly associated with overall survival. In this study, we aim to characterize the genomic correlates (microRNA, messenger RNA, and protein) of this vascular parameter. This study aims to provide a comprehensive radiogenomic and radioproteomic characterization of the hemodynamic phenotype of GBM using publicly available imaging and genomic data from the Cancer Genome Atlas GBM cohort. Based on this analysis, we identified pathways associated with angiogenesis and tumor proliferation underlying this hemodynamic parameter in GBM.

Prognostic Value of Dynamic Susceptibility Contrast-Enhanced and Diffusion-Weighted MR Imaging in Patients with Glioblastomas.

Prediction of survival in patients with glioblastomas is important for individualized treatment planning. This study aimed to assess the prognostic utility of presurgical dynamic susceptibility contrast and diffusion-weighted imaging for overall survival in patients with glioblastoma. MR imaging data from pathologically proved glioblastomas between June 2006 to December 2013 in 58 patients (mean age, 62.7 years; age range, 22-89 years) were included in this retrospective study. Patients were divided into long survival (≥15 months) and short survival (<15 months) groups, depending on overall survival time. Patients underwent dynamic susceptibility contrast perfusion and DWI before surgery and were treated with chemotherapy and radiation therapy. The maximum relative cerebral blood volume and minimum mean diffusivity values were measured from the enhancing part of the tumor. Maximum relative cerebral blood volume values in patients with short survival were significantly higher compared with those who demonstrated long survival (P < .05). No significant difference was observed in the minimum mean diffusivity between short and long survivors. Receiver operator curve analysis demonstrated that a maximum relative cerebral blood volume cutoff value of 5.79 differentiated patients with low and high survival with an area under the curve of 0.93, sensitivity of 0.89, and specificity of 0.90 (P < .001), while a minimum mean diffusivity cutoff value of 8.35 × 10(-4)mm(2)/s had an area under the curve of 0.55, sensitivity of 0.71, and specificity of 0.47 (P > .05) in separating the 2 groups. Maximum relative cerebral blood volume may be used as a prognostic marker of overall survival in patients with glioblastomas.

Abstract T P13: Effect of Pre-treatment Cerebral Blood Volume and Time to Recanalization on Good Clinical Outcomes in Endovascular Thrombectomy

Introduction: Previous studies suggested that faster times to recanalization led to better clinical outcomes in patients after endovascular thrombectomy. Hypothesis: We assessed the hypothesis that an association between time to recanalization and clinical outcomes depends on cerebral blood volume (CBV) obtained from pre-treatment CT perfusion (CTP). Methods: In consecutive patients with acute ischemic stroke who were obtained successful recanalization (TICI 2A-3) by endovascular thrombectomy for internal carotid artery or middle cerebral artery M1 occlusion, we retrospectively analyzed the influence on clinical outcome of time to recanalization and relative CBV value (rCBV) evaluated by pre-treatment CTP. The patient population was divided into 3 groups according to rCBV: severe decreased rCBV group (rCBV &lt;0.6), mild decreased rCBV group (rCBV 0.6 to 0.9) and normal rCBV group (rCBV &gt;0.9). In each group, we compared time to recanalization from onset and CTP between good clinical outcome group (modified Rankin Scale score ≤2 at day 90) and poor clinical outcome group (modified Rankin Scale score ≥3). Results: Fifty-seven patients were eligible for this study. The mean age was 75.3 years and median baseline NIHSS was 17. Nineteen patients (33.3 %) achieved good clinical outcome. In the severe decreased rCBV group, mean time to recanalization from onset and CTP were 192 and 115 minutes, respectively, but no patient had a good clinical outcome. In the mild decreased rCBV group, mean time to recanalization from onset (180 versus 311 minutes, p=0.034) and CTP (102 versus 169 minutes, p=0.007) were significantly shorter in the good clinical outcome group. In the normal rCBV group, no association was found between clinical outcome and time to recanalization from onset (311 versus 313 minutes) and CTP (177 versus 184 minutes). Conclusions: Early successful recanalization resulted in better clinical outcome in patients with mild decreased rCBV. Severe decreased rCBV did not provide good outcome regardless of early successful recanalization.

Added value of advanced over conventional magnetic resonance imaging in grading gliomas and other primary brain tumors.

BackgroundAlthough conventional MR imaging (MRI) is the most widely used non-invasive technique for brain tumor grading, its accuracy has been reported to be relatively low. Advanced MR techniques, such as perfusion-weighted imaging (PWI), diffusion-weighted imaging (DWI), and magnetic resonance spectroscopy (MRS), could predict neoplastic histology, but their added value over conventional MRI is still open to debate.MethodsWe prospectively analyzed 129 patients diagnosed with primary brain tumors (118 gliomas) classified as low-grade in 30 cases and high-grade in 99 cases.ResultsSignificant differences were obtained in high-grade tumors for conventional MRI variables (necrosis, enhancement, edema, hemorrhage, and neovascularization); high relative cerebral blood volume values (rCBV), low relative apparent diffusion coefficients (rADC), high ratio of N-acetyl-aspartate/creatine at short echo time (TE) and high choline/creatine at long TE. Among conventional MRI variables, the presence of enhancement and necrosis were demonstrated to be the best predictors of high grade in primary brain tumors (sensitivity 95.9%; specificity 70%). The best results in primary brain tumors were obtained for enhancement, necrosis, and rADC (sensitivity 98.9%; specificity 75.9%). Necrosis and enhancement were the only predictors of high grade in gliomas (sensitivity 97.6%; specificity 76%) when all the magnetic resonance variables were combined.ConclusionsMRI is highly accurate in the assessment of tumor grade. The combination of conventional MRI features with advanced MR variables showed only improved tumor grading by adding rADC to conventional MRI variables in primary brain tumors.

Comparison of Perfusion, Diffusion, and MR Spectroscopy between Low-Grade Enhancing Pilocytic Astrocytomas and High-Grade Astrocytomas

The differentiation of pilocytic astrocytomas and high-grade astrocytomas is sometimes difficult. There are limited comparisons in the literature of the advanced MR imaging findings of pilocytic astrocytomas versus high-grade astrocytomas. The purpose of this study was to assess the MR imaging, PWI, DWI, and MR spectroscopy characteristics of pilocytic astrocytomas compared with high-grade astrocytomas. Sixteen patients with pilocytic astrocytomas and 22 patients with high-grade astrocytomas (8-66 years of age; mean, 36 ± 17 years) were evaluated by using a 1.5T MR imaging unit. MR imaging, PWI, DWI, and MR spectroscopy were used to determine the differences between pilocytic astrocytomas and high-grade astrocytomas. The sensitivity, specificity, and the area under the receiver operating characteristic curve of all analyzed parameters at respective cutoff values were determined. The relative cerebral blood volume values were significantly lower in pilocytic astrocytomas compared with the high-grade astrocytomas (1.4 ± 0.9 versus 3.3 ± 1.4; P = .0008). The ADC values were significantly higher in pilocytic astrocytomas compared with high-grade astrocytomas (1.5 × 10(-3) ± 0.4 versus 1.2 × 10(-3) ± 0.3; P = .01). The lipid-lactate in tumor/creatine in tumor ratios were significantly lower in pilocytic astrocytomas compared with high-grade astrocytomas (8.3 ± 11.2 versus 43.3 ± 59.2; P = .03). The threshold values ≥1.33 for relative cerebral blood volume provide sensitivity, specificity, positive predictive values, and negative predictive values of 100%, 67%, 87%, and 100%, respectively, for differentiating high-grade astrocytomas from pilocytic astrocytomas. The optimal threshold values were ≤1.60 for ADC, ≥7.06 for lipid-lactate in tumor/creatine in tumor, and ≥2.11 for lipid-lactate in tumor/lipid-lactate in normal contralateral tissue. Lower relative cerebral blood volume and higher ADC values favor a diagnosis of pilocytic astrocytoma, while higher lipid-lactate in tumor/creatine in tumor ratios plus necrosis favor a diagnosis of high-grade astrocytomas.

Contribution of perfusion-weighted magnetic resonance imaging in the differentiation of meningiomas and other extra-axial tumors: case reports and literature review

We present six cases of extra-axial lesions: three meningiomas [including one intraventricular and one cerebellopontine angle (CPA) meningioma], one dural metastasis, one CPA schwannoma and one choroid plexus papilloma which were chosen from a larger cohort of extra-axial tumors evaluated in our institution. Apart from conventional MR examinations, all the patients also underwent perfusion-weighted imaging (PWI) using dynamic susceptibility contrast method on a 1.5 T MR unit (contrast: 0.3 mmol/kg, rate 5 ml/s). Though the presented tumors showed very similar appearance on conventional MR images, they differed significantly in perfusion examinations. The article draws special attention to the usefulness of PWI in the differentiation of various extra-axial tumors and its contribution in reaching final correct diagnoses. Finding a dural lesion with low perfusion parameters strongly argues against the diagnosis of meningioma and should raise a suspicion of a dural metastasis. In cases of CPA tumors, a lesion with low relative cerebral blood volume values should be suspected to be schwannoma, allowing exclusion of meningioma to be made. In intraventricular tumors arising from choroid plexus, low perfusion parameters can exclude a diagnosis of meningioma. In our opinion, PWI as an easy and quick to perform functional technique should be incorporated into the MR protocol of all intracranial tumors including extra-axial neoplasms.

Distinction between pyogenic brain abscess and necrotic brain tumour using 3-tesla MR spectroscopy, diffusion and perfusion imaging

The purpose of this study is to compare the effectiveness of relative cerebral blood volume, apparent diffusion coefficient and spectroscopic imaging in differentiating between cerebral abscesses and necrotic tumours. In the prospective study, a 3-tesla MR unit was used to perform proton MR spectroscopy, diffusion and perfusion imaging in 20 patients with cerebral abscesses and 26 patients who had solitary brain tumours (14 high-grade gliomas and 12 metastases). We found the mean apparent diffusion coefficient value at the central cavities of the cerebral abscesses to be significantly lower than in necrotic tumours. The mean relative cerebral blood volume values of the necrotic tumour wall were statistically significantly higher than the mean relative cerebral blood volume values of the cerebral abscess wall by the Student's t-test. The proton spectra obtained revealed amino acids only in the cerebral abscesses. Although the conventional MRI characteristics of cerebral abscesses and necrotic tumours may sometimes be similar, diffusion, perfusion-weighted and spectroscopic MRI enables distinction between the two.

Relative Cerebral Blood Volume Values to Differentiate High-Grade Glioma Recurrence from Posttreatment Radiation Effect: Direct Correlation between Image-Guided Tissue Histopathology and Localized Dynamic Susceptibility-Weighted Contrast-Enhanced Perfusion MR Imaging Measurements

Differentiating tumor growth from posttreatment radiation effect (PTRE) remains a common problem in neuro-oncology practice. To our knowledge, useful threshold relative cerebral blood volume (rCBV) values that accurately distinguish the 2 entities do not exist. Our prospective study uses image-guided neuronavigation during surgical resection of MR imaging lesions to correlate directly specimen histopathology with localized dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging (DSC) measurements and to establish accurate rCBV threshold values, which differentiate PTRE from tumor recurrence. Preoperative 3T gradient-echo DSC and contrast-enhanced stereotactic T1-weighted images were obtained in patients with high-grade glioma (HGG) previously treated with multimodality therapy. Intraoperative neuronavigation documented the stereotactic location of multiple tissue specimens taken randomly from the periphery of enhancing MR imaging lesions. Coregistration of DSC and stereotactic images enabled calculation of localized rCBV within the previously recorded specimen locations. All tissue specimens were histopathologically categorized as tumor or PTRE and were correlated with corresponding rCBV values. All rCBV values were T1-weighted leakage-corrected with preload contrast-bolus administration and T2/T2*-weighted leakage-corrected with baseline subtraction integration. Forty tissue specimens were collected from 13 subjects. The PTRE group (n = 16) rCBV values ranged from 0.21 to 0.71, tumor (n = 24) values ranged from 0.55 to 4.64, and 8.3% of tumor rCBV values fell within the PTRE group range. A threshold value of 0.71 optimized differentiation of the histopathologic groups with a sensitivity of 91.7% and a specificity of 100%. rCBV measurements obtained by using DSC and the protocol we have described can differentiate HGG recurrence from PTRE with a high degree of accuracy.