Elsevier

NeuroImage

Volume 45, Issue 2, 1 April 2009, Pages 312-318
NeuroImage

Use of fractional anisotropy for determination of the cut-off value in 11C-methionine positron emission tomography for glioma

https://doi.org/10.1016/j.neuroimage.2008.11.034Get rights and content

Abstract

Multimodal imaging is one of the necessary steps in the treatment of malignant brain tumors, and use of magnetic resonance imaging (MRI) and positron emission tomography (PET) are the current gold standard technique for the morphological and biological assessment of malignant brain tumors. In addition, fractional anisotropy (FA) obtained from diffusion tensor imaging (DTI) and 11C-methionine PET are useful to determine the tumor border at the tumor and white matter interface. Although there is no question of their value, a universally accepted cut-off value to discriminate normal and abnormal tissue has not been established. In this study we attempted to calculate and determine the cut-off values in FA and 11C-methionine PET that will allow delineation of the tumor border at the tumor and white matter interface by combining these two modalities. We were able to determine individual cut-off values for 11 patients, and then found an average cut-off value in the T/N ratio of 11C-methionine PET of 1.27 and in FA of 0.26, values similar to those previously confirmed by histological study. Moreover, reconstructing images delineating the tumor border was possible combining these two imaging modalities. We propose that the combined analysis of DTI and 11C-methionine PET has the potential to improve tumor border imaging in glioma patients, providing important information for establishing neurosurgical strategies.

Introduction

Recent developments in magnetic resonance imaging (MRI) and positron emission tomography (PET) have enabled visualization of the biological and physiological characteristics of the brain in ways that have been impossible in the past. The development in functional MRI has enabled imaging of the anatomical location of the activated brain cortex under certain tasks (Price, 2007) and the development of diffusion tensor imaging (DTI) has allowed delineation of white matter neural fiber tracts in a non-invasive manner (Bello et al., 2008, Kamada et al., 2005a, Kamada et al., 2005b, Kinoshita et al., 2005, Mikuni et al., 2007, Nimsky et al., 2005, Nimsky et al., 2006a, Nimsky et al., 2006b). On the other hand, various radio-labeled tracers have been developed for visualization by PET of the metabolic status of both normal and pathological brain, including ischemic, neurodegenerative and neoplastic diseases (Chen, 2007, Herholz et al., 1998, Kato et al., 2008, Kracht et al., 2004, Pirotte et al., 2004, Stadlbauer et al., 2008).

Today, in the field of neuro-oncology, in order to achieve maximum tumor resection while preserving as much neural function as possible, multimodal radiological assessment is performed for surgical planning. DTI has been used with the combined use of neuro-navigation systems to visualize white matter fiber tracts adjacent to the tumor (Bello et al., 2008, Kamada et al., 2005a, Kamada et al., 2005b, Kinoshita et al., 2005, Mikuni et al., 2007, Nimsky et al., 2005, Nimsky et al., 2006a, Nimsky et al., 2006b) and 18F-fluorodeoxyglucose or 11C-methionine PET have been used for delineation of the extent of tumor cell invasion into the white matter (Pirotte et al., 2004). In addition, DTI has also been used to assess tumor cell invasion at the tumor border (Stadlbauer et al., 2007). A decrease of fractional anisotropy (FA) has been reported to be a useful marker for detecting tumor cell invasion into the white matter (Stadlbauer et al., 2007). However, both imaging techniques present difficulties in delineation of the tumor border, as universal agreement of the normal to abnormal cut-off values has not been established, although several authors have circumvented this issue by histological evaluation of the obtained images (Herholz et al., 1998, Kracht et al., 2004, Stadlbauer et al., 2006).

In the present study, we investigated the possibility of the combined use of DTI and PET images to “automatically” calculate the cut-off values in patients harboring malignant gliomas. As both FA and 11C-methionine PET can be useful modalities to detect the tumor border, we hypothesized that the combined use of these two modalities would allow each to compensate for the other's inadequacies, thereby allowing calculation of the cut-off values for detection of the tumor border.

Section snippets

Patient selection

We collected data from 11 patients harboring gliomas who underwent both DTI and 11C-methionine PET studies as presurgical examination at the Osaka University Hospital from 2007 to 2008. DTI was performed using 3.0- or1.5-T magnetic resonance imaging (MRI). Post-surgical histological examination revealed 1 grade II, 3 grade III and 7 grade IV glioma patients. Detailed information of all 11 patients is listed in Table 1.

Diffusion tensor imaging

All images were obtained using a 3.0-T or 1.5-T (Signa, GE Medical Systems,

Scatter plot of FA as a function of the SUV of 11C-methionine PET shows a peculiar pattern

As shown in the left bottom corner of Fig. 2, when the FA values of each voxel were plotted as a function of the standard uptake value (SUV) of 11C-methionine PET (MET-PET), the data plots showed a peculiar pattern. It is easily appreciated that the data plots can be sectioned into 3 groups, i.e. a high FA and low MET-PET, group, a low FA and low MET-PET group, and finally a low FA and high MET-PET group. When the biological implications of each study are taken into consideration, the high FA

Discussion

With the continuing development of technologies in neuroradiology, it is now possible to non-invasively visualize and understand the biological characteristics of malignant brain tumors and the conditions of the surrounding tissues in a way not possible in the past. As the primary goal in the treatment of malignant gliomas is to maximize tumor resection, it is crucial to presurgically obtain information on the extent of tumor cell invasion. In order to pursue this goal, multimodal imagining of

Acknowledgments

This investigation was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan (subject numbers; 18591589 and 19790997).

References (31)

  • TaniguchiM. et al.

    Movement-related desynchronization of the cerebral cortex studied with spatially filtered magnetoencephalography

    NeuroImage

    (2000)
  • BeppuT. et al.

    Measurement of fractional anisotropy using diffusion tensor MRI in supratentorial astrocytic tumors

    J. Neuro-oncol.

    (2003)
  • ChenW.

    Clinical applications of PET in brain tumors

    J. Nucl. Med.

    (2007)
  • GoebellE. et al.

    Low-grade and anaplastic gliomas: differences in architecture evaluated with diffusion-tensor MR imaging

    Radiology

    (2006)
  • HerholzK. et al.

    11C-methionine PET for differential diagnosis of low-grade gliomas

    Neurology

    (1998)
  • Cited by (0)

    View full text