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

Differentiation of recurrent glioblastoma multiforme from radiation necrosis after external beam radiation therapy with dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSION

These findings suggest that DSC perfusion MR imaging may be used to differentiate recurrent GBM from EBRT-induced radiation necrosis.

Integration of preoperative anatomic and metabolic physiologic imaging of newly diagnosed glioma

PURPOSE

To integrate standard anatomic magnetic resonance imaging in conjunction with uniformly acquired physiologic imaging biomarkers of untreated glioma with different histological grades with the goal of generating an algorithm that can be applied for patient management.

METHODS

A total of 143 patients with previously untreated glioma were scanned immediately before surgical resection using conventional anatomical MR imaging, and with uniform acquisition of perfusion-weighted imaging, diffusion-weighted imaging, and proton MR spectroscopic imaging. Regions of interest corresponding to anatomic and metabolic lesions were identified to assess tumor burden. MR parameters that had been found to be predictive of survival in patients with grade IV glioma were evaluated as a function of tumor grade and histological sub-type. Based on these finding both anatomic and physiologic imaging parameters were then integrated to generate an algorithm for management of patients with newly diagnosed presumed glioma.

RESULTS

Histological analysis indicated that the population comprised 56 patients with grade II, 31 with grade III, and 56 with grade IV glioma. Based on standard anatomic imaging, the presence of hypointense necrotic regions in post-Gadolinium T1-weighted images and the percentage of the T2 hyperintense lesion that was either enhancing or necrotic were effective in identifying patients with grade IV glioma. The individual parameters of diffusion and perfusion parameters were significantly different for patients with grade II astrocytoma versus oligodendroglioma sub-types. All tumors had regions with elevated choline to N-acetylasparate index (CNI). Lactate was higher for grade III and grade IV glioma and lipid was significantly elevated for grade IV glioma. These results were integrated into a proposed management algorithm for newly diagnosed glioma that will need to be prospectively tested in future studies.

CONCLUSION

Metabolic and physiologic imaging characteristics provide information about tumor heterogeneity that may be important for assisting the surgeon to ensure acquisition of representative histology. Correlation of these integrated MR parameters with clinical features will need to be assessed with respect to their role in predicting outcome and stratifying patients into risk groups for clinical trials. Future studies will use image directed tissue sampling to confirm the biological interpretation of these parameters and to assess how they change in response to therapy.

Radiological progression of cerebral metastases after radiosurgery: assessment of perfusion MRI for differentiating between necrosis and recurrence

To assess the capability of perfusion MRI to differentiate between necrosis and tumor recurrence in patients showing radiological progression of cerebral metastases treated with stereotactic radiosurgery (SRS). From 2004 to 2006 dynamic susceptibility-weighted contrast-enhanced perfusion MRI scans were performed on patients with cerebral metastasis showing radiological progression after SRS during follow-up. Several perfusion MRI characteristics were examined: a subjective visual score of the relative cerebral blood volume (rCBV) map and quantitative rCBV measurements of the contrast-enhanced areas of maximal perfusion. For a total of 34 lesions in 31 patients a perfusion MRI was performed. Diagnoses were based on histology, definite radiological decrease or a combination of radiological and clinical follow-up. The diagnosis of tumor recurrence was obtained in 20 of 34 lesions, and tumor necrosis in 14 of 34. Regression analyses for all measures proved statistically significant (χ² = 11.6–21.6, P < 0.001–0.0001). Visual inspection of the rCBV map yielded a sensitivity and specificity of 70.0 respectively 92.9%. The optimal cutoff point for maximal tumor rCBV relative to white matter was 2.00 (improving the sensibility to 85.0%) and 1.85 relative to grey matter (GM), improving the specificity to 100%, with a corresponding sensitivity of 70.0%. Perfusion MRI seems to be a useful tool in the differentiation of necrosis and tumor recurrence after SRS. For the patients displaying a rCBV-GM greater than 1.85, the diagnosis of necrosis was excluded. Salvage treatment can be initiated for these patients in an attempt to prolong survival.

Differentiation between glioblastomas and solitary brain metastases using diffusion tensor imaging

The purpose of this study is to determine whether diffusion tensor imaging (DTI) metrics including tensor shape measures such as linear and planar anisotropy coefficients (CL and CP) can help differentiate glioblastomas from solitary brain metastases. Sixty-three patients with histopathologic diagnosis of glioblastomas (22 men, 16 women, mean age 58.4 years) and brain metastases (13 men, 12 women, mean age 56.3 years) were included in this study. Contrast-enhanced T1-weighted, fluid-attenuated inversion recovery (FLAIR) images, fractional anisotropy (FA), apparent diffusion coefficient (ADC), CL and CP maps were co-registered and each lesion was semi-automatically subdivided into four regions: central, enhancing, immediate peritumoral and distant peritumoral. DTI metrics as well as the normalized signal intensity from the contrast-enhanced T1-weighted images were measured from each region. Univariate and multivariate logistic regression analyses were employed to determine the best model for classification. The results demonstrated that FA, CL and CP from glioblastomas were significantly higher than those of brain metastases from all segmented regions (p<0.05), and the differences from the enhancing regions were most significant (p<0.001). FA and CL from the enhancing region had the highest prediction accuracy when used alone with an area under the curve of 0.90. The best logistic regression model included three parameters (ADC, FA and CP) from the enhancing part, resulting in 92% sensitivity, 100% specificity and area under the curve of 0.98. We conclude that DTI metrics, used individually or combined, have a potential as a non-invasive measure to differentiate glioblastomas from metastases.

Relationship of pre-surgery metabolic and physiological MR imaging parameters to survival for patients with untreated GBM

Glioblastoma Multiforme (GBM) are heterogeneous lesions, both in terms of their appearance on anatomic images and their response to therapy. The goal of this study was to evaluate the prognostic value of parameters derived from physiological and metabolic images of these lesions. Fifty-six patients with GBM were scanned immediately before surgical resection using conventional anatomical MR imaging and, where possible, perfusion-weighted imaging, diffusion-weighted imaging, and proton MR spectroscopic imaging. The median survival time was 517 days, with 15 patients censored. Absolute anatomic lesion volumes were not associated with survival but patients for whom the combined volume of contrast enhancement and necrosis was a large percentage of the T2 hyperintense lesion had relatively poor survival. Other volumetric parameters linked with less favorable survival were the volume of the region with elevated choline to N-acetylaspartate index (CNI) and the volume within the T2 lesion that had apparent diffusion coefficient (ADC) less than 1.5 times that in white matter. Intensity parameters associated with survival were the maximum and the sum of levels of lactate and of lipid within the CNI lesion, as well as the magnitude of the 10th percentile of the normalized ADC within the contrast-enhancing lesion. Patients whose imaging parameters indicating that lesions with a relatively large percentage with breakdown of the blood brain barrier or necrosis, large regions with abnormal metabolism or areas with restricted diffusion have relatively poor survival. These parameters may provide useful information for predicting outcome and for the stratification of patients into high or low risk groups for clinical trials.

Evaluation of MR markers that predict survival in patients with newly diagnosed GBM prior to adjuvant therapy

Purpose Glioblastoma Multiforme (GBM) is the most common and lethal primary brain tumor in adults. The goal of this study was to test the predictive value of MR parameters in relation to the survival of patients with newly diagnosed GBM who were scanned prior to receiving adjuvant radiation and chemotherapy. Methods The study population comprised 68 patients who had surgical resection and were to be treated with fractionated external beam radiation therapy and chemotherapy. Imaging scans included anatomical MRI, diffusion and perfusion weighted imaging and (1)H MRSI. The MR data were acquired 3-5 weeks after surgery and approximately 1 week before treatment with radiation therapy. The diffusion, perfusion and spectroscopic parameter values were quantified and subjected to proportional hazards analysis that was adjusted for age and scanner field strength. Results The patients with larger lesion burden based upon volumes of anatomic lesions, volume of CNI2 (number of voxels within the T2 lesion having choline to NAA index >2), volume of CBV3 (number of pixels within the T2 lesion having relative cerebral blood volume >3), and volume of nADC1.5 (number of pixels within the T2 lesion having normalized apparent diffusion coefficient <1.5) had a higher risk for poor outcome. High intensities of combined measures of lactate and lipid in the T2 and CNI2 regions were also associated with poor survival. Conclusions Our study indicated that several pre-treatment anatomic, physiological and metabolic MR parameters are predictive of survival. This information may be important for stratifying patients to specific treatment protocols and for planning focal therapy.

Distinguishing recurrent intra-axial metastatic tumor from radiation necrosis following gamma knife radiosurgery using dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging

BACKGROUND AND PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Magnetic resonance perfusion imaging in neuro-oncology

Recent advances in magnetic resonance imaging (MRI) have seen the development of techniques that allow quantitative imaging of a number of anatomical and physiological descriptors. These techniques have been increasingly applied to cancer imaging where they can provide some insight into tumour microvascular structure and physiology. This review details technical approaches and application of quantitative MRI, focusing particularly on perfusion imaging and its role in neuro-oncology.

MR Perfusion Imaging of Intracranial Tumors

This retrospective study evaluated magnetic resonance (MR) perfusion imaging in the study of intracranial tumors; 218 patients were studied with 509 MR examinations. The first aim was to establish the usefulness of perfusion imaging for the differential diagnosis between neoplastic tissue and other lesions both in the first MR examination and in the post therapeutic controls (differentiation of tumor recurrence from radionecrosis). Then we evaluated the presence of infiltrating neoplastic tissue in CBV maps outside the enhancement area to differentiate infiltrating gliomas from metastases. In addition, post surgical evaluation was performed to identify residual neoplastic tissue, mainly if bleeding or inflammatory post surgical cerebral damage did not allow a definitive diagnosis with conventional morphologic images. Lastly, it was assessed whether hypervascularization (evaluated in CBV maps) is a favourable prognostic factor for a positive outcome to radiotherapy. The diagnostic gain of perfusion imaging in all these cases was established evaluating our case records.