Perfusion-weighted Imaging Data Research Articles

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.

Fluid-Attenuated Inversion Recovery Vascular Hyperintensities-Diffusion-Weighted Imaging Mismatch Identifies Acute Stroke Patients Most Likely to Benefit From Recanalization.

Fluid-attenuated inversion recovery vascular hyperintensities (FVH) beyond the boundaries of diffusion-weighted imaging (DWI) lesion (FVH-DWI mismatch) have been proposed as an alternative to perfusion-weighted imaging (PWI)-DWI mismatch. We aimed to establish whether FVH-DWI mismatch can identify patients most likely to benefit from recanalization. FVH-DWI mismatch was assessed in 164 patients with proximal middle cerebral artery occlusion before intravenous thrombolysis. PWI-DWI mismatch (PWITmax>6sec/DWI>1.8) was assessed in the 104 patients with available PWI data. We tested the associations between 24-hours complete recanalization on magnetic resonance angiography and 3-month favorable outcome (modified Rankin Scale score ≤2), stratified on FVH-DWI (or PWI-DWI) status. FVH-DWI mismatch was present in 121/164 (74%) patients and recanalization in 50/164 (30%) patients. The odds ratio for favorable outcome with recanalization was 16.2 (95% confidence interval, 5.7-46.5; P<0.0001) in patients with FVH-DWI mismatch and 2.6 (95% confidence interval, 0.6-12.1; P=0.22) in those without FVH-DWI mismatch (P=0.048 for interaction). Recanalization was associated with favorable outcome in patients with PWI-DWI mismatch (odds ratios, 9.9; 95% confidence interval, 3.1-31.3; P=0.0001) and in patients without PWI-DWI mismatch (odds ratios, 7.0; 95% confidence interval, 1.1-44.1; P=0.047), P=0.76 for interaction. The FVH-DWI mismatch may rapidly identify patients with proximal occlusion most likely to benefit from recanalization.

Predictive value of PWI for blood supply and T1-spin echo MRI for consistency of pituitary adenoma.

It is a common view that consistency and blood supply of pituitary adenoma (PA) can influence the surgical effect. The aim of this study was to determine whether MRI signal intensity (SI) was correlated to the consistency or blood supply of pituitary macroadenoma. Forty eight pituitary macroadenoma patients were underwent preoperative MRI, including precontrast and contrast-enhanced (CE) T1-spin echo (T1-SE) imaging, CE-sampling perfection with application-optimized contrasts by using different flip angle evolutions (SPACE) imaging, and perfusion-weighted imaging (PWI). The tumor consistency and blood supply were determined by neurosurgeons. The expression of collagen IV and MIB-1 was detected with immunohistology. The correlation of the relative SI (rSI) values (tumor to normal frontal white matter SI) and PWI data to the tumor consistency, blood supply, and the expression level of collagen IV and MIB-1 was statistically studied by Kruskal-Wallis rank test (K-W test). A significant correlation was observed between the tumor consistency and the rSI on precontrast T1-SE imaging (P = 0.004) but not on CE T1-SE and CE SPACE imaging. The expression of collagen IV was also significantly associated with rSI on T1-SE imaging (P = 0.010). The blood supply was correlated with the relative CBV (rCBV) (P = 0.030). In addition, the expression of MIB-1 was correlated with rSI of CE T1-SE imaging (P = 0.007). Our results suggest that T1-SE imaging may be a simple and useful method for predicting consistency of PA. CBV value can provide helpful information for assessing the blood supply of pituitary macroadenoma.

Influence of selecting EPI readout-encoding bandwidths on arterial spin labeling perfusion MRI

The objective of this study was to investigate effects of varying readout bandwidths on the arterial spin labeling (ASL)-perfusion MRI measurements at a high magnetic field MRI system. Brain perfusion studies were performed on nine volunteers (four males, five females) using flow sensitive alternating inversion recovery (FAIR) ASL single-shot echo-planar imaging (EPI)-MRI. To investigate EPI bandwidth effects on the time-series perfusion-weighted imaging (PWI) data, two regions-of-interest (ROI) were placed outside the brain to determine the level of noise and another ROI inside the brain to determine the level of signal. Coefficients of variations (CoV) were calculated for the time-series PWI data. One-way analysis of variance (ANOVA) was used to investigate voxel-wise differences in the time-series PWI data between two different bandwidth values. At the level of ROI, there was no significant effect of changing EPI bandwidths on the time-series PWI data in any of the volunteers (P > 0.031). In contrast, CoV values over the dynamic PWI data varied with depending on selecting EPI bandwidths and voxel-based tests showed that N2 ghosting, modulated by EPI bandwidth, can appear in some brain regions, especially in areas that overlap with the spatial distribution of N2 ghosting artifacts. Although N2 ghosting can be reduced by adjusting the bandwidth of EPI on the time-series of PWI data, the effects cannot be entirely eliminated. In particular, N2 ghosting can bias CBF quantification if EPI control scans to determine the equilibrium-state signal are confounded by N2 ghosting. Therefore, careful tuning of the bandwidth of EPI is necessary to avoid artifacts in the ASL signal from N2-ghosting.

The comparative study of MR diffusion-weighted imaging and MR perfusion-weighted imaging in diagnosing soft tissue tumors

Objective To evaluate MR diffusion-weighted imaging (DWI)and MR perfusion-weighted imaging(PWI) in differentiating benign from malignant soft tissue tumors by comparing the related parameters. Methods Fifty patients with soft tissue tumors verified by pathology( benign 24, malignant 26) underwent DWI and dynamic contrast-enhanced T2 * -weighted PWI. DWI and PWI data of benign and malignant soft tissue tumors were acquired at the workstation and their difference was analyzed with t-test. The diagnostic accordance rate was verified with x2-test. Subjective overall performance of two techniques were evaluated with receiver operating characteristic (ROC) analysis. Results ADC values of benign and malignant tumors were (2. 03±0. 36) × 10-3 mm2/s, ( 1.52±0. 39) × 10-3 mm2/s,respectively. The signal intensity decrease of them during the first-pass perfusion (SIdecrease ) were ( 13.54 ± 3.37 )%, (47. 57 ± 5. 21 ) % ,respectively. The maximum linearity slope rate of TIC ( SSmax ) of them were ( 5.51 ± 2. 54 ) %, (7.94 ± 3. 33) %, respectively. There were significant differences between benign and malignant tumors of ADC value and SIdecrease ( t = 2. 515,2. 938 ;P 0. 05). When the threshold of ADC value was 1. 866 × mm2/s, sensitivity and specificity for determining malignant tumors were 84. 6% (22/26)and 83.3% (20/24). When the threshold of SIdecrease was 40. 33% ,sensitivity and specificity for determining malignant tumors were 88. 5% (23/26)and 75.0% (18/24). In type Ⅰa of TIC,the proportion of benign soft tissue tumor was 3/24 and malignant tumor was 20/26. In type Ⅰb , benign tumor was 14/24 and malignant tumor was 3/26. In type Ⅰc, malignant tumor was 3/26. In type Ⅱ ,benign tumor was 7/24. The diagnostic accordance rate of DWI and PWI were 84. 0% (42/50) and 82. 0% (41/50), respectively. There was no significant difference between them ( x2 = 0. 8, P >0. 05). The accuracies of them were 81.7% , 83. 6% respectively by the area under the ROC curve (AUC). The sensitivity of PWI in diagnosing malignant soft tissue tumors was higher. Conclusions ADC value and SIdecrease are Valllable diagnostic parameters in differentiating benign and malignant soft tissue tumors. The threshold of these parameters for diagnosing malignant soft tissue tumors are 1. 866 × 10-3 mm2/s and 40. 33%, respectively. The type of TIC can help to distinguish malignant tumors from benign tumors, while the SSmax can not. The accuracies of DWI and PWI in the diagnosis of malignant soft tissue tumors are moderate. Compared with DWI, PWI should be selected firstly because of its higher sensitivity in diagnosing malignant tumors. Key words: Soft tissue neoplasm; Magnetic resonance imaging

Patients with Acute Stroke Treated with Intravenous tPA 3–6 Hours after Stroke Onset: Correlations between MR Angiography Findings and Perfusion- and Diffusion-weighted Imaging in the DEFUSE Study

To study magnetic resonance (MR) angiography findings in patients with acute stroke treated with intravenous tissue plasminogen activator (tPA) in relationship to perfusion- and diffusion-weighted imaging changes and clinical outcome. Patients treated with intravenous tPA 3-6 hours after stroke onset (with informed consent) were evaluated in a HIPAA-compliant multicenter prospective study approved by all institutional review boards. MR imaging and MR angiography studies were performed before and 3-6 hours after treatment. MR angiography studies that were technically adequate at both time points were evaluated for occlusion, decreased flow, any early recanalization, and degree of recanalization. These results were compared with favorable clinical response (an improvement in National Institutes of Health Stroke Scale score of >or=8 points at 30 days or a modified Rankin scale score of 0 or 1 at 30 days) in patients with and those without mismatch between perfusion- and diffusion-weighted imaging at baseline. Seventy-four patients were enrolled in the initial investigation; pre- and posttreatment MR angiography studies were both technically adequate in 62 patients. MR angiography demonstrated occlusion or decreased flow in 46 patients. Patients with isolated middle cerebral artery (MCA) occlusion and early recanalization at MR angiography had higher rates of favorable clinical response than those with tandem internal carotid artery-MCA occlusion and early recanalization (P = .05). Any early recanalization was not associated with favorable clinical response, but degree of recanalization did correlate with favorable clinical response (P = .048). Favorable clinical response was more frequently seen in patients with mismatch between perfusion- and diffusion-weighted imaging findings at baseline who experienced early recanalization than in those who did not have early recanalization (odds ratio = 6.2; 95% confidence interval: 1.3, 30.2; P = .021). No relationship between early recanalization and favorable clinical response was seen in patients without mismatch. Early recanalization seen at MR angiography before and after treatment coupled with diffusion- and perfusion-weighted imaging data may predict clinical outcome in patients with stroke treated with tPA 3-6 hours after symptom onset.