204 AJR:188, January 2007 AJR 2007; 188:204–212 0361–803X/07/1881–204 © American Roentgen Ray Society 204.FM — 11/30/06 Spampinato et al. rCBV and MRS of Oligodendroglial Tumors Neuroradiology • Original Research Cerebral Blood Volume Measurements and Proton MR Spectroscopy in Grading of Oligodendroglial Tumors M. Vittoria Spampinato 1,2 J. Keith Smith 1 Lester Kwock 1 Matthew Ewend 3 John D. Grimme 1 Daniel L. A. Camacho 1 Mauricio Castillo 1 Spampinato MV, Smith JK, Kwock L, et al. Keywords: brain, MR technique, MRI, oncologic imaging, perfusion-weighted MRI DOI:10.2214/AJR.05.1177 Received July 8, 2005; accepted after revision January 19, 2006. J. K. Smith is a recipient of a Philips Medical Systems/RSNA seed grant. 1 Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599. 2 Present address: Department of Radiology, Medical University of South Carolina, 169 Ashley Ave., PO Box 250322, Charleston, SC 29425. Address correspondence to M. V. Spampinato. 3 Division of Neurosurgery, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599. OBJECTIVE. The purpose of this study was to determine whether perfusion-weighted im- aging (PWI) and proton MR spectroscopy (MRS) are useful in differentiating high- and low- grade oligodendroglial tumors. MATERIALS AND METHODS. PWI and MRS studies of 22 patients with histologi- cally proven oligodendroglioma or oligoastrocytoma (13 low-grade and nine anaplastic tumors) were retrospectively reviewed. PWI of 14 subjects was performed with a dynamic contrast-en- hanced susceptibility-weighted echo-planar technique. Intratumoral relative cerebral blood vol- ume ratio was calculated and normalized to the same value in contralateral normal-appearing white matter. Multivoxel MRS was performed with a point-resolved spectroscopy sequence at a TE of 135 milliseconds in 20 patients and with the addition of a TE of 30 seconds in 17 patients. MRS data were expressed as intratumoral metabolite ratios (choline to creatine [Cho/Cr], choline to N-acetyl aspartate, N-acetyl aspartate to creatine, and myoinositol to creatine). RESULTS. Relative cerebral blood volume ratios were significantly different (p = 0.004) between low-grade (1.61 ± 1.20) and high-grade tumors (5.45 ± 1.96). The optimal relative ce- rebral blood volume ratio cutoff value in identification of anaplastic oligodendroglial tumors was 2.14. Analysis of MRS data showed significantly higher Cho/Cr ratios (p = 0.002) in high- grade than in low-grade tumors. A Cho/Cr ratio cutoff value of 2.33 had the highest accuracy in identification of high-grade tumors. CONCLUSION. Relative cerebral blood volume measurement and MRS are helpful in differentiating low-grade from anaplastic oligodendroglial tumors. ligodendroglioma is among the most chemosensitive of brain tu- mors [1, 2]. Histologic features consistent with oligodendroglioma have positive implications for prognosis and survival. The World Health Organization (WHO) grading system has good correlation with prognosis: 9.8-year and 3.9-year median survival periods for low-grade oligodendro- glioma and anaplastic oligodendroglioma, re- spectively [3, 4]. Thus prospective establish- ment of tumor grade may be important. Neoplasms containing an oligodendroglial component often include a mixed population of cells, most commonly including astrocytes. No consensus exists on the proportion of oligoden- droglial to astrocytic cells required to classify a tumor as pure oligodendroglioma or oligoastro- cytoma. The suggested threshold fraction of as- troglial lineage ranges from 1% through 25% and 30% to approximately 50% in different studies [3]. Oligoastrocytoma has biologic be- havior similar to that of oligodendroglioma and better prognosis and response to chemotherapy than astrocytic tumors (6.3- and 2.8-year me- dian survival periods for low-grade oligoastro- cytoma and anaplastic oligoastrocytoma, re- spectively) [5–9]. Assessment of tumor grade from tissue obtained at stereotatic biopsy is prone to sampling error because oligodendro- glial tumors can contain regions of varied his- tologic characteristics. Conventional MRI shows contrast enhancement, which is consid- ered important in identification of high-grade oligodendroglial tumors [10]. In a study [11] of conventional MRI features of oligodendro- glioma, however, the presence of contrast en- hancement had a sensitivity of only 63% and a specificity of 50% in differentiation of anaplas- tic from low-grade tumors. Advanced MRI techniques, such as perfu- sion-weighted imaging (PWI), may be helpful in preoperative determination of tumor grade, which may affect surgical planning. Relative cerebral blood volume (rCBV) measurements may improve tumor grading [12]. In addition, O Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved