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Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases
Published on: July 28, 2013
Glial tumor grading and outcome prediction using dynamic spin-echo MR susceptibility mapping compared with
Michael H Lev1, Yelda Ozsunar, John W Henson
1Departments of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
Background And Purpose:
The MR imaging characteristics of oligodendrogliomas and astrocytomas on spin-echo (SE), echo-planar relative cerebral blood volume (rCBV) maps, to our knowledge, have not previously been emphasized. We compared the specificity of SE rCBV mapping with that of conventional, contrast material-enhanced MR imaging in differentiating high- from low-grade glial tumors and in predicting survival of patients with these lesions.
Methods:
Thirty consecutive adult patients with suspected gliomas underwent conventional and rCBV MR imaging. Representative maximal rCBV regions of interest were chosen from each lesion. Resultant values were normalized to those of corresponding, contralateral, uninvolved regions. These normalized CBV (nCBV) values were correlated with degree of contrast enhancement, histopathologic tumor grade, and survival.
Results:
Twenty-two patients had astroctyomas and eight had oligodendrogliomas. With an nCBV cutoff ratio of 1.5, 13 of 13 high-grade astrocytomas were correctly categorized, three of which did not enhance. Seven of nine low-grade astrocytomas were correctly classified by their nCBV values, including one enhancing lesion. Of eight oligodendrogliomas, four of four high-grade and two of four low-grade tumors had elevated nCBV values; two low-grade oligodendrogliomas enhanced, one with nCBV greater than 1.5 and one with nCBV less than 1.5. In 19 patients with astrocytoma for whom survival data were available, correlation with survival was better for nCBV (mean survival 91 +/- 14 months for nCBV < 1.5 versus 24 +/- 27 months for nCBV > 1.5, P <.0001) than for enhancement (mean survival 61 +/- 35 months without enhancement versus 22 +/- 29 months with enhancement, P =.03).
Conclusion:
Elevated SE rCBV was a sensitive, but not specific, marker for high-grade histopathology: all high-grade tumors had nCBV foci values greater than 1.5. No tumor with nCBV region of interest less than 1.5 was high grade (100% predictive value for excluding high grade). Degree of nCBV elevation was a stronger predictor of both tumor grade and survival than was degree of enhancement. A significant proportion of low-grade glial neoplasms, most notably oligodendrogliomas, may display high rCBV foci not reflective of high-grade histopathology.
Insights
Spin-echo echo-planar relative cerebral blood volume (rCBV) mapping is a sensitive marker for high-grade glial tumors, predicting survival better than contrast enhancement. However, elevated rCBV in some low-grade tumors, particularly oligodendrogliomas, may not reflect high-grade histopathology.
Area of Science:
- Neuroimaging
- Oncology
- Radiology
Background:
- Oligodendrogliomas and astrocytomas are common glial tumors.
- Differentiating high- from low-grade glial tumors is crucial for treatment and prognosis.
- Spin-echo echo-planar relative cerebral blood volume (SE rCBV) mapping has not been extensively studied for these tumors.
Purpose of the Study:
- To compare the specificity of SE rCBV mapping with conventional contrast-enhanced MRI.
- To evaluate the ability of SE rCBV to differentiate high-grade from low-grade glial tumors.
- To assess the predictive value of SE rCBV for patient survival.
Main Methods:
- 30 adult patients with suspected gliomas underwent conventional and rCBV MRI.
- Normalized CBV (nCBV) values were calculated and correlated with tumor grade and enhancement.
- Survival data were analyzed in relation to nCBV and enhancement.
Main Results:
- SE rCBV mapping showed high sensitivity for high-grade tumors (all had nCBV > 1.5).
- nCBV was a stronger predictor of tumor grade and survival than contrast enhancement.
- Some low-grade oligodendrogliomas exhibited elevated nCBV, not indicative of high-grade pathology.
Conclusions:
- Elevated SE rCBV is sensitive but not specific for high-grade glial tumors.
- nCBV < 1.5 reliably excluded high-grade tumors.
- SE rCBV mapping offers valuable prognostic information for glial tumors, complementing conventional MRI.