Percentage Of Signal Intensity Recovery Research Articles

Evaluation of the Value of Perfusion-Weighted Magnetic Resonance Imaging in the Differential Diagnosis of Sellar and Parasellar Tumors.

The purpose of this study was to assess the value of perfusion-weighted imaging (PWI) in the differential diagnosis of sellar and parasellar tumors, as an additional sequence in the magnetic resonance imaging (MRI) protocol. Analysis was based on a substantial group of subjects and included 124 brain and pituitary MRI examinations with a dynamic susceptibility contrast (DSC) PWI sequence. The following perfusion parameters were determined for the tumors: relative cerebral blood volume (rCBV), relative peak height (rPH) and relative percentage of signal intensity recovery (rPSR). To ensure greater repeatability, each of the aforementioned parameters was calculated as: arithmetic mean of the values of the whole tumor, arithmetic mean of the maximum values on each axial slice within the tumor and maximum values derived from the whole tumor. In our study, we established that meningiomas compared to both non-functional and hormone-secreting pituitary adenomas (pituitary neuroendocrine tumors-PitNET) had significantly higher values of rCBV with cut-off points set at 3.45 and 3.54, respectively (mean rCBV). Additionally, meningiomas presented significantly higher maximum and mean maximum rPH values compared to adenomas. DSC PWI imaging adds significant value to conventional MRI examinations and can be helpful in differentiating equivocal pituitary tumors.

Added Value of Spectroscopy to Perfusion MRI in the Differential Diagnostic Performance of Common Malignant Brain Tumors.

Perfusion and spectroscopic MR imaging provide noninvasive physiologic and metabolic characterization of tissues, which can help in differentiating brain tumors. We investigated the diagnostic role of perfusion and spectroscopic MR imaging using individual and combined classifiers of these modalities and assessed the added performance value that spectroscopy can provide to perfusion using optimal combined classifiers that have the highest differential diagnostic performance to discriminate lymphomas, glioblastomas, and metastases. From January 2013 to January 2016, fifty-five consecutive patients with histopathologically proved lymphomas, glioblastomas, and metastases were included after undergoing MR imaging. The perfusion parameters (maximum relative CBV, maximum percentage of signal intensity recovery) and spectroscopic concentration ratios (lactate/Cr, Cho/NAA, Cho/Cr, and lipids/Cr) were analyzed individually and in optimal combinations. Differences among tumor groups, differential diagnostic performance, and differences in discriminatory performance of models with quantification of the added performance value of spectroscopy to perfusion were tested using 1-way ANOVA models, receiver operating characteristic analysis, and comparisons between receiver operating characteristic analysis curves using a bivariate χ2, respectively. The highest differential diagnostic performance was obtained with the following combined classifiers: maximum percentage of signal intensity recovery-Cho/NAA to discriminate lymphomas from glioblastomas and metastases, significantly increasing the sensitivity from 82.1% to 95.7%; relative CBV-Cho/NAA to discriminate glioblastomas from lymphomas and metastases, significantly increasing the specificity from 92.7% to 100%; and maximum percentage of signal intensity recovery-lactate/Cr and maximum percentage of signal intensity recovery-Cho/Cr to discriminate metastases from lymphomas and glioblastomas, significantly increasing the specificity from 83.3% to 97.0% and 100%, respectively. Spectroscopy yielded an added performance value to perfusion using optimal combined classifiers of these modalities, significantly increasing the differential diagnostic performances for these common brain tumors.

Accuracy of percentage of signal intensity recovery and relative cerebral blood volume derived from dynamic susceptibility-weighted, contrast-enhanced MRI in the preoperative diagnosis of cerebral tumours.

Conventional magnetic resonance imaging (MRI) is the technique of choice for diagnosis of cerebral tumours, and has become an increasingly powerful tool for their evaluation; however, the diagnosis of common contrast-enhancing lesions can be challenging, as it is sometimes impossible to differentiate them using conventional imaging. Histopathological analysis of biopsy specimens is the gold standard for diagnosis; however, there are significant risks associated with the invasive procedure and definitive diagnosis is not always achieved. Early accurate diagnosis is important, as management differs accordingly. Advanced MRI techniques have increasing utility for aiding diagnosis in a variety of clinical scenarios. Dynamic susceptibility-weighted contrast-enhanced (DSC) MRI is a perfusion imaging technique and a potentially important tool for the characterisation of cerebral tumours. The percentage of signal intensity recovery (PSR) and relative cerebral blood volume (rCBV) derived from DSC MRI provide information about tumour capillary permeability and neoangiogenesis, which can be used to characterise tumour type and grade, and distinguish tumour recurrence from treatment-related effects. Therefore, PSR and rCBV potentially represent a non-invasive means of diagnosis; however, the clinical utility of these parameters has yet to be established. We present a review of the literature to date.

Differentiation of hemangioblastomas from pilocytic astrocytomas using 3-T magnetic resonance perfusion-weighted imaging and MR spectroscopy.

Hemangioblastomas and pilocytic astrocytomas (PAs) present similar imaging features on conventional MR imaging, making differential diagnosis a challenge. The purpose of this study was to evaluate the usefulness of dynamic susceptibility-weighted contrast-enhanced perfusion-weighted imaging (DSC-PWI) and proton MR spectroscopic imaging in the differentiation of hemangioblastomas and PAs. A 3.0-T MR imaging unit was used to perform DSC-PWI and conventional MR imaging on 14 patients with hemangioblastomas and 22 patients with PAs. Four patients with hemangioblastomas and 10 PA patients also underwent proton MR spectroscopy. Parameters of relative peak height (rPH) and relative percentage of signal intensity recovery (rPSR) were acquired by DSC-PWI and variables of N-acetylaspasrtate (NAA)/creatine (Cr), choline (Cho)/Cr, and lactate-lipid (Lac-Lip)/Cr by MR spectroscopy. The sensitivity, specificity, and the area under the receiver operating characteristic curve of all analyzed parameters at respective cutoff values were determined. Higher rPH but lower rPSR values were detected in hemangioblastomas compared to PAs. The NAA/Cr ratio was significantly lower in hemangioblastomas compared with PAs. The threshold values ≥3.2 for rPH provide sensitivity, specificity, positive predictive values, and negative predictive values of 85.7, 95.5, 92.3, and 91.3%, respectively, for differentiating hemangioblastomas from PAs. The optimal threshold values were ≤0.9 for rPSR and ≤1.5 for NAA/Cr ratios in tumor. Significantly higher rPH and lower NAA/Cr were seen in patients with hemangioblastomas when compared with PA patients, suggesting that DSC-PWI and proton MR spectroscopy are helpful in the characterization and differentiation of these two types of tumors.

Perfusion magnetic resonance imaging for high grade astrocytomas: Can cerebral blood volume, peak height, and percentage of signal intensity recovery distinguish between progression and pseudoprogression?

ObjectivesTo study the usefulness of common MRI perfusion parameters for identifying pseudoprogression in high grade astrocytomas. Materials and methodsThis retrospective case–control study compared the relative cerebral blood volume (rCBV), the relative percentage of signal intensity recovery (rPSR), and the relative peak height (rPH) recorded in a sample of 17 cases of anaplastic astrocytomas and gliomas considered to be undergoing pseudoprogression by biopsy or follow-up with those recorded in a sample of histologically similar tumors that were treated and considered to be undergoing progression by histologic study or follow-up. We evaluated the accuracy of these parameters and the correlations among them. Statistical significance was set at p<.05. ResultsThe rCBV, rPSR, and rPH were significantly different between the two groups (p=.001). The cutoff values rPH=1.37, rCBV=0.9, and rPSR=99% yielded sensitivity (S)=88% and specificity (Sp)=82.2% for rPH, S=100% and Sp=100% for rCBV, and S=100% and Sp=70.6% for rPSR, respectively. We found negative correlations between rPRS and rPH (−0.76) and between rPRS and rCBV (−0.81) and a high positive correlation between rPH and rCBV (0.87). ConclusionThe variables rPH and rCBV were useful for differentiating between pseudoprogression and true progression in our sample. The variable rPRS was also very sensitive, although the overlap in the values between samples makes it less useful a priori.

Differentiation of Primary Central Nervous System Lymphomas from High-Grade Gliomas by rCBV and Percentage of Signal Intensity Recovery Derived from Dynamic Susceptibility-Weighted Contrast-Enhanced Perfusion MR Imaging

Primary central nervous system lymphoma (PCNSL) and high-grade glioma (HGG) may have similar enhancement patterns on magnetic resonance imaging (MRI), making the differential diagnosis difficult or even impractical. Relative cerebral blood volume (rCBV) and percentage of signal intensity recovery derived from dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion MR imaging may help distinguish PCNSL from HGG. The purpose of this study was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of these two imaging parameters used alone or in combination for differentiating PCNSL from HGG. A total of 12 patients with PCNSL and 26 patients with HGG were examined using a 3T scanner. rCBV and percentage of signal intensity recovery were obtained and receiver operating characteristic (ROC) analysis was performed to determine optimum thresholds for tumor differentiation. Sensitivity, specificity, PPV, NPV, and accuracy for identifying the tumor types were also calculated. The optimum threshold of 2.56 for rCBV provided sensitivity, specificity, PPV, NPV, and accuracy of 96.2, 90, 92.6, 94.7, and 93.5%, respectively, for determining PCNSL. A threshold value of 0.89 for percentage of signal intensity recovery optimized differentiation of PCNSL and HGG with a sensitivity, specificity, PPV, NPV, and accuracy of 100, 88.5, 87, 100, and 93.5%, respectively. Combining rCBV with the percentage of signal intensity recovery further improved the differentiation of PCNSL and HGG with a specificity of 98.5% and an accuracy of 95.7%. The combination of rCBV measurement with percentage of signal intensity recovery can help in more accurate differentiation of PCNSL from HGG.

Resonancia magnética de perfusión en astrocitomas de alto grado: el volumen sanguíneo cerebral, la altura del pico y el porcentaje de recuperación de intensidad de señal ¿pueden discriminar entre progresión y seudoprogresión?

To study the usefulness of common MRI perfusion parameters for identifying pseudoprogression in high grade astrocytomas.This retrospective case-control study compared the relative cerebral blood volume (rCBV), the relative percentage of signal intensity recovery (rPSR), and the relative peak height (rPH) recorded in a sample of 17 cases of anaplastic astrocytomas and gliomas considered to be undergoing pseudoprogression by biopsy or follow-up with those recorded in a sample of histologically similar tumors that were treated and considered to be undergoing progression by histologic study or follow-up. We evaluated the accuracy of these parameters and the correlations among them. Statistical significance was set at P<.05.The rCBV, rPSR, and rPH were significantly different between the two groups (P=.001). The cutoff values rPH=1.37, rCBV=0.9, and rPSR=99% yielded sensitivity (S)=88% and specificity (Sp)=82.2% for rPH, S=100% and Sp=100% for rCBV, and S=100% and Sp=70.6% for rPSR, respectively. We found negative correlations between rPRS and rPH (-0.76) and between rPRS and rCBV (-0.81) and a high positive correlation between rPH and rCBV (0.87).The variables rPH and rCBV were useful for differentiating between pseudoprogression and true progression in our sample. The variable rPRS was also very sensitive, although the overlap in the values between samples make it less useful a priori.

Usefulness of perfusion weighted magnetic resonance imaging with signal-intensity curves analysis in the differential diagnosis of sellar and parasellar tumors: Preliminary report

PurposeThe most common pituitary tumors are adenomas, which however may be mimicked by other tumors that can show a very similar appearance in plain MRI. The aim of our study was to evaluate the usefulness of perfusion weighted MR imaging (PWI), including signal-intensity curves analysis in the differential diagnosis of sellar/parasellar tumors. MethodsForty-one patients with sellar/parasellar tumors (23 macroadenomas, 10 meningiomas, 5 craniopharyngiomas, 1 intrasellar hemangioblastoma, 1 intrasellar prostate cancer metastasis, 1 suprasellar glioma), underwent plain MRI followed by PWI using a 1.5T unit. In each tumor, the mean and maximum values of relative cerebral blood volume (rCBV), as well as the relative peak height (rPH) and the relative percentage of signal intensity recovery (rPSR) were calculated. ResultsThe high perfusion tumors were: macroadenomas, meningiomas, squamous-papillary type of craniopharyngiomas, hemangioblastoma, glioma and metastasis. The low perfusion neoplasms included adamantinomatous type of craniopharyngiomas. By comparing adenomas and meningiomas, we found statistically significant differences in the mean and maximum rCBV values (p=0.026 and p=0.019, respectively), but not in rPH and rPSR. The maximum rCBV values >7.14 and the mean rCBV values >5.74 with the typical perfusion curve were very suggestive of the diagnosis of meningioma. There were differences between adenomas and other high perfusion tumors in rPH and rPSR values. ConclusionsPWI can provide additional information helpful in differential diagnosis of sellar/parasellar tumors. In our opinion PWI, as an easy to perform and fast technique should be incorporated into the MR protocol of all intracranial neoplasms including sellar/parasellar tumors.

Comparison of the effectiveness of MRI perfusion and fluorine-18 FDG PET-CT for differentiating radiation injury from viable brain tumor: a preliminary retrospective analysis with pathologic correlation in all patients

ObjectivesDifferentiating radiation injury from viable tumor is important for optimizing patient care. Our aim was to directly compare the effectiveness of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) and dynamic susceptibility-weighted contrast-enhanced (DSC) magnetic resonance (MR) perfusion in differentiating radiation effects from tumor growth in patients with increased enhancement following radiotherapy for primary or secondary brain tumors. Materials and methodsWe retrospectively identified 12 consecutive patients with primary and secondary brain tumors over a 1-year period that demonstrated indeterminate enhancing lesions after radiotherapy and that had undergone DSC MR perfusion, FDG PET-CT, and subsequent histopathologic diagnosis. The maximum standardized uptake value (SUV) of the lesion (SUVlesion max), SUVratio (SUVlesion max/SUVnormal brain), maximum relative cerebral blood volume, percentage of signal intensity recovery, and relative peak height were calculated from the positron emission tomography and MR perfusion studies. A prediction of tumor or radiation injury was made based on these variables while being blinded to the results of the surgical pathology. ResultsSUVratio had the highest predictive value (area under the curve=0.943) for tumor progression, although this was not statistically better than any MR perfusion metric (area under the curve=0.757–0.829). ConclusionsThis preliminary study suggests that FDG PET-CT and DSC MR perfusion may demonstrate similar effectiveness for distinguishing tumor growth from radiation injury. Assessment of the SUVratio may increase the sensitivity and specificity of FDG PET-CT for differentiating tumor and radiation injury. Further analysis is needed to help define which modality has greater predictive capabilities.

Magnetic resonance imaging of solitary brain metastases: main findings of nonmorphological sequences

This study was done to investigate the usefulness of diffusion-weighted (DWI), perfusion-weighted (PWI) and proton magnetic resonance (MR) spectroscopy imaging in characterising solitary brain metastases. Fifty-nine solitary brain metastases were evaluated with conventional and nonmorphological MR imaging: DWI, PWI and MR spectroscopy. We evaluated size, signal intensity and contrast enhancement and calculated apparent diffusion coefficient (ADC), relative cerebral blood volume (rCBV), percentage of signal intensity recovery (PSR) and maximum values of N-acetylaspartate (NAA), choline (Cho), creatine (Cr), lipids (Lip), NAA/Cr and Cho/Cr. The nonmorphological parameters were compared with those from the literature for brain lesions that frequently enter the differential diagnosis with metastases. Signal intensity and contrast enhancement patterns were variable. There was a wide range of ADC values: min:max 0.59×10(-3):1.88×10(-3). Compared with normal white matter, rCBV was higher in lesions (3.30±1.59) and lower in perilesional oedema (0.42±0.15). Mean and minimum PSR were 57% and 48%, respectively; lip and Cho were elevated and NAA reduced. Conventional MR findings of solitary metastases are heterogeneous, and some values of nonmorphological sequences are similar to those of other brain lesions. PWI seems to be the nonmorphological MR technique that may best contribute to the diagnosis of brain metastases.

Regional variation in histopathologic features of tumor specimens from treatment-naive glioblastoma correlates with anatomic and physiologic MR Imaging

Histopathologic evaluation of glioblastoma multiforme (GBM) at initial diagnosis is typically performed on tissue obtained from regions of contrast enhancement (CE) as depicted on gadolinium-enhanced, T1-weighted images. The non-enhancing (NE) portion of the lesion, which contains both reactive edema and infiltrative tumor, is only partially removed due to concerns about damaging functioning brain. The purpose of this study was to evaluate histopathologic and physiologic MRI features of image-guided tissue specimens from CE and NE regions to investigate correlations between imaging and histopathologic parameters. One hundred nineteen tissue specimens (93 CE and 26 NE regions) were acquired from 51 patients with newly diagnosed GBM by utilizing stereotactic image-guided sampling. Variables of anatomic, diffusion-weighted imaging (DWI), and dynamic susceptibility-weighted, contrast-enhanced perfusion imaging (DSC) from each tissue sample location were obtained and compared with histopathologic features such as tumor score, cell density, proliferation, architectural disruption, hypoxia, and microvascular hyperplasia. Tissue samples from CE regions had increased tumor score, cellular density, proliferation, and architectural disruption compared with NE regions. DSC variables such as relative cerebral blood volume, peak height, and recovery factor were significantly higher, and the percentage of signal intensity recovery was significantly lower in the CE compared with the NE regions. DWI variables were correlated with histopathologic features of GBM within NE regions. Image-guided tissue acquisition and assessment of residual tumor from treatment-naive GBM should be guided by DSC in CE regions and by DWI in NE regions.

Multiparametric magnetic resonance imaging to differentiate high-grade gliomas and brain metastases

To assess the performance of parameters used in conventional magnetic resonance imaging (MRI), perfusion-weighted MR imaging (PWI) and visual texture analysis, alone and in combination, to differentiate a single brain metastasis (MET) from glioblastoma multiforme (GBM). In a retrospective study of 50 patients (41 GBM and 14 MET) who underwent T2/FLAIR/T1(post-contrast) imaging and PWI, morphological (circularity, surface area), perfusion (rCBV in the ring-like tumor area, rCBV in the peritumoral area, percentage of signal intensity recovery at the end of first pass) and texture parameters in the peritumoral area were estimated. Statistical differences and performances were assessed using Wilcoxon's test and receiver operating characteristic curves, respectively. Multiparametric classification of tumors was performed using k-means clustering. Significant statistical differences in circularity, surface area, rCBVs, percentage of signal intensity recovery and texture parameters (energy, entropy, homogeneity, correlation, inverse differential moment, sum average) were observed between MET and GBM (P<0.05). Moderate-to-good classification performances were found with these parameters. Clustering based on rCBV and texture parameters (contrast, sum average) differentiated MET from GBM with a sensitivity of 92% and a specificity of 71%. Combining perfusion and visual texture parameters within a statistical classifier significantly improved the differentiation of a single brain MET and GBM.

MR perfusion-weighted imaging may help in differentiating between nonenhancing gliomas and nonneoplastic lesions in the cervicomedullary junction

To evaluate the ability of dynamic susceptibility-weighted contrast-enhanced magnetic resonance (MR) perfusion imaging (DSC-PWI) in distinguishing between nonenhancing gliomas and nonenhancing, nonneoplastic lesions in the cervicomedullary junction region. This retrospective study involved eight patients with nonenhancing gliomas in the medulla oblongata and eight patients with nonenhancing nonneoplastic lesions. The relative cerebral blood volume (rCBV) ratios, peak heights, and percentage of signal intensity recovery derived from time-signal intensity curves of these nonenhancing lesions were compared. The mean peak height of nonenhancing gliomas was significantly higher than the value of their reference regions of interest (ROIs). In contrast, mean peak height of nonneoplastic lesions was significantly lower than their reference ROIs. The mean peak height and mean maximal rCBV ratio of nonenhancing gliomas were significantly higher than those of nonenhancing, nonneoplastic lesions (P<0.05). There was no significant difference with regard to percentage of signal intensity recovery between the two groups. DSC-PWI could be a useful adjuvant tool to differentiate between nonenhancing gliomas and nonenhancing, nonneoplastic lesions in the cervicomedullary junction region.

Differentiation between intra-axial metastatic tumor progression and radiation injury following fractionated radiation therapy or stereotactic radiosurgery using MR spectroscopy, perfusion MR imaging or volume progression modeling

Objective To determine the accuracy of magnetic resonance spectroscopy (MRS), perfusion MR imaging (MRP), or volume modeling in distinguishing tumor progression from radiation injury following radiotherapy for brain metastasis. Methods Twenty-six patients with 33 intra-axial metastatic lesions who underwent MRS ( n=41) with or without MRP ( n=32) after cranial irradiation were retrospectively studied. The final diagnosis was based on histopathology ( n=4) or magnetic resonance imaging (MRI) follow-up with clinical correlation ( n=29). Cho/Cr (choline/creatinine), Cho/NAA (choline/ N-acetylaspartate), Cho/nCho (choline/contralateral normal brain choline) ratios were retrospectively calculated for the multi-voxel MRS. Relative cerebral blood volume (rCBV), relative peak height (rPH) and percentage of signal-intensity recovery (PSR) were also retrospectively derived for the MRPs. Tumor volumes were determined using manual segmentation method and analyzed using different volume progression modeling. Different ratios or models were tested and plotted on the receiver operating characteristic curve (ROC), with their performances quantified as area under the ROC curve (AUC). MRI follow-up time was calculated from the date of initial radiotherapy until the last MRI or the last MRI before surgical diagnosis. Results Median MRI follow-up was 16 months (range: 2–33). Thirty percent of lesions ( n=10) were determined to be radiation injury; 70% ( n=23) were determined to be tumor progression. For the MRS, Cho/nCho had the best performance (AUC of 0.612), and Cho/nCho >1.2 had 33% sensitivity and 100% specificity in predicting tumor progression. For the MRP, rCBV had the best performance (AUC of 0.802), and rCBV >2 had 56% sensitivity and 100% specificity. The best volume model was percent increase (AUC of 0.891); 65% tumor volume increase had 100% sensitivity and 80% specificity. Conclusion Cho/nCho of MRS, rCBV of MRP, and percent increase of MRI volume modeling provide the best discrimination of intra-axial metastatic tumor progression from radiation injury for their respective modalities. Cho/nCho and rCBV appear to have high specificities but low sensitivities. In contrast, percent volume increase of 65% can be a highly sensitive and moderately specific predictor for tumor progression after radiotherapy. Future incorporation of 65% volume increase as a pretest selection criterion may compensate for the low sensitivities of MRS and MRP.

Differentiation of Recurrent Glioblastoma Multiforme from Radiation Necrosis after External Beam Radiation Therapy with Dynamic Susceptibility-weighted Contrast-enhanced Perfusion MR Imaging

To investigate whether cerebral blood volume (CBV), peak height (PH), and percentage of signal intensity recovery (PSR) measurements derived from the results of T2-weighted dynamic susceptibility-weighted contrast material-enhanced (DSC) magnetic resonance (MR) imaging performed after external beam radiation therapy (EBRT) can be used to distinguish recurrent glioblastoma multiforme (GBM) from radiation necrosis. Fifty-seven patients were enrolled in this HIPAA-compliant institutional review board-approved retrospective study after they received a diagnosis of GBM, underwent EBRT, and were examined with DSC MR imaging, which revealed progressive contrast enhancement within the radiation field. A definitive diagnosis was established at subsequent surgical resection or clinicoradiologic follow-up. Regions of interest were retrospectively drawn around the entire contrast-enhanced region. This created T2-weighted signal intensity-time curves that produced three cerebral hemodynamic MR imaging measurements: CBV, PH, and PSR. Welch t tests were used to compare measurements between groups. Mean, maximum, and minimum relative PH and relative CBV were significantly higher (P < .01) in patients with recurrent GBM than in patients with radiation necrosis. Mean, maximum, and minimum relative PSR values were significantly lower (P < .05) in patients with recurrent GBM than in patients with radiation necrosis. These findings suggest that DSC perfusion MR imaging may be used to differentiate recurrent GBM from EBRT-induced radiation necrosis.

Differentiation of primary central nervous system lymphoma and high-grade glioma with dynamic susceptibility contrast-enhanced perfusion magnetic resonance imaging

Preoperative differentiation of primary central nervous system lymphomas (PCNSLs) from other tumors is important for presurgical staging, intraoperative management, and postoperative treatment. Dynamic susceptibility contrast-enhanced perfusion magnetic resonance imaging (DSC perfusion MRI) can provide in vivo assessment of the microvasculature in intracranial mass lesions. To determine the utility of DSC perfusion MRI in the differentiation of PCNSLs and high-grade gliomas, as well as their pathological and physiological differences. Nine patients with pathologically proven PCNSLs and 11 patients with high-grade gliomas were examined using a 1.5 T MRI scanner. DSC perfusion MRI was performed by gradient-echo echo-planar imaging (GE-EPI). The maximum rCBV ratio, the signal intensity-time curves, and the percentage of signal intensity recovery were obtained. The maximum relative cerebral blood volume (rCBV) ratio and the percentage of signal intensity recovery of PCNSLs were compared with those of high-grade gliomas by using Student's t test. Microvessel density (MVD) was evaluated using immunohistochemical staining of surgical specimens with anti-CD34, and MVDs of the two tumor groups were compared by using Student's t test. The maximum rCBV ratio of primary intracranial lymphomas was 1.72+/-0.59, while that of high-grade gliomas was 4.86+/-2.18. PCNSLs tended to have relatively low perfusion compared to high-grade gliomas (P=0.001), and the MVD labeled by anti-CD34 of PCNSLs was much lower than that of gliomas (P<0.001). The signal intensity-time curve of primary intracranial lymphomas was different from that of high-grade gliomas. The percentage of signal intensity recovery was significantly greater in PCNSLs compared with that of high-grade gliomas (P<0.001). The difference in DSC perfusion MRI characteristics between PCNSLs and high-grade gliomas is determined by their different vascularities and different patterns of contrast agent leakage. This difference may be helpful in the diagnosis and preoperative differentiation between PCNSLs and high-grade gliomas, which sometimes may have similar conventional MR imaging appearance.

Distinguishing Recurrent Intra-Axial Metastatic Tumor from Radiation Necrosis Following Gamma Knife Radiosurgery Using Dynamic Susceptibility-Weighted Contrast-Enhanced Perfusion MR Imaging

MR image-guided gamma knife radiosurgery is often used to treat intra-axial metastatic neoplasms. Following treatment, it is often difficult to determine whether a progressively enhancing lesion is due to metastatic tumor recurrence or radiation necrosis. The purpose of our study was to determine whether relative cerebral blood volume (rCBV), relative peak height (rPH), and percentage of signal-intensity recovery (PSR) derived from dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging can distinguish recurrent metastatic tumor from radiation necrosis. Twenty-seven patients with systemic cancer underwent gamma knife radiosurgery for metastatic lesions of the brain and subsequently developed enlarging regions of enhancement within the radiation field. Subsequent surgical resection or clinicoradiologic follow-up established a diagnosis of recurrent metastatic tumor or radiation necrosis. Perfusion MR imaging datasets were retrospectively reprocessed, and regions of interest were drawn around the entire contrast-enhancing region. The resulting T2* signal-intensity time curves produced rCBV, rPH, and PSR values for each examination. A Welch t test was used to compare imaging values between groups. The mean, minimum, and maximum PSR values were significantly lower (P < .01) in cases of recurrent metastatic tumor. The mean and maximum rCBV and rPH values were significantly higher (P < .02) in the recurrent metastatic tumor group. The findings of our study suggest that perfusion MR imaging may be used to differentiate recurrent intra-axial metastatic tumor from gamma knife-induced radiation necrosis.

Differentiation of Glioblastoma Multiforme and Single Brain Metastasis by Peak Height and Percentage of Signal Intensity Recovery Derived from Dynamic Susceptibility-Weighted Contrast-Enhanced Perfusion MR Imaging

Glioblastoma multiforme (GBM) and single brain metastasis (MET) are the 2 most common malignant brain tumors that can appear similar on anatomic imaging but require vastly different treatment strategy. The purpose of our study was to determine whether the peak height and the percentage of signal intensity recovery derived from dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion MR imaging could differentiate GBM and MET. Forty-three patients with histopathologic diagnosis of GBM (n=27) or MET (n=16) underwent DSC perfusion MR imaging in addition to anatomic MR imaging before surgery. Regions of interest were drawn around the nonenhancing peritumoral T2 lesion (PTL) and the contrast-enhancing lesion (CEL). T2* signal intensity-time curves acquired during the first pass of gadolinium contrast material were converted to the changes in relaxation rate to yield T2* relaxivity (Delta R2*) curve. The peak height of maximal signal intensity drop and the percentage of signal intensity recovery at the end of first pass were measured for each voxel in the PTL and CEL regions of the tumor. The average peak height for the PTL was significantly higher (P=.04) in GBM than in MET. The average percentage of signal intensity recovery was significantly reduced in PTL (78.4% versus 82.8%; P=.02) and in CEL (62.5% versus 80.9%, P<.01) regions of MET compared with those regions in the GBM group. The findings of our study show that the peak height and the percentage of signal intensity recovery derived from the Delta R2* curve of DSC perfusion MR imaging can differentiate GBM and MET.