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Comparing the volume of gliomas in the brain in FLAIR and post-contrast T1-weighted MRI sequences.

INTRODUCTION

Primary brain tumors are among the top 10 causes of cancer-related deaths with 14/100,000 people in the United States being diagnosed every year. Glial tumors are the most common type of primary brain tumor with the majority being malignant, and they are derived from a variety of cells including astrocytes, oligodendrocytes, and ependymal cells. The pathogenesis of glial tumors has been linked to a variety of genetic abnormalities including genes that regulate cell-cycle control and growth-factor signaling pathways. (1) The imaging modality of choice used for diagnosing and monitoring brain tumors, including glial tumors, is magnetic resonance imaging (MRI) with intravenous contrast. Standard MR imaging protocols for brain tumors include contrast-enhanced T1-weighted and fluid-attenuated inversion recovery (FLAIR) imaging. Contrast-enhanced T1-weighted images display hyperintense areas where there is disruption of the blood brain barrier and increased angiogenesis. (2,3) FLAIR imaging, on the other hand, is a type of T2-weighted imaging in which the surrounding reactive and infiltrative changes of the primary tumor are also visualized, and therefore, the primary tumor is more completely characterized (Figure 1). (3,4) Currently, many clinical trials are using contrast-enhanced T1-weighted images to evaluate tumor response to chemoradiation treatment. It is our hypothesis that the FLAIR sequences will detect higher tumor volumes when compared with the post-contrast T1-weighted sequences and should, therefore, be the preferred MR sequence used to monitor tumor response to treatment.

MATERIALS AND METHODS

We selected 38 patients with the pathological diagnosis of glioma from cases presented at random at our neuropathology/neuroradiology conferences. Those patients were imaged on a 1.5T MR scanner. Axial FLAIR and post-contrast T1-weighted MR images in Digital Imaging and Communications in Medicine (DICOM) format of each patient's brain were obtained from the Louisiana State University (LSU) picture archiving and communication system (PACS) and transferred to a personal computer. Using the Medical Image Processing, Analysis and Visualization (MIPAV) software program, a volumetric analysis of the tumors was conducted by two researchers. The average of these volumes was subsequently calculated. The average tumor volumes from FLAIR and T1-weighted post-contrast MR images were correlated using the EZAnalyze software program embedded into Microsoft Excel 2007. The ratio of the tumor volume in the FLAIR MR image sequences to the tumor volume in the post-contrast T1-weighted MR image sequences was also calculated.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

RESULTS

Tumoral volumes were greater in the FLAIR MR sequences than in the post-contrast T1-weighted MR sequences in all 38 patients, with an average FLAIR/post-contrast T1 ratio of approximately 2.83 and a range of 1.13-10.93. A statistically significant positive correlation was found to exist between the FLAIR and post-contrast T1-weighted volumes, with a Pearson correlation coefficient of 0.798 and a p-value of 2.05 x [10.sup.-9] (Figure 2).

CONCLUSION

It can be concluded that in magnetic resonance imaging, larger tumor volumes are obtained using the FLAIR image sequence when compared to post-contrast T1-weighted images. The FLAIR image sequence displays a larger volume due to the inclusion of the surrounding reactive and infiltrative changes of the tumor. (3,4) As a result, FLAIR image sequences provide a more complete characterization of gliomas and the surrounding changes and may be more beneficial when observing tumor response after treatment. These conclusions are of paramount importance when tracking changes in tumor volumes in FLAIR and post-contrast T1-weighted images in glioma patients undergoing treatment.

REFERENCES

(1.) Butowski NA, Chang SM. Glial tumors: the current state of scientific knowledge. Clin Neurosurg 2006;53:106-113.

(2.) Debnam JM, Ketonen L, Hamberg LM, et al. Current techniques used for the radiologic assessment of intracranial neoplasms. Arch Pathol Lab Med 2007;131:252-260.

(3.) Cha S. Update on brain tumor imaging. Curr Neurol Neurosci Rep 2005;5:169-177.

(4.) Kates R, Atkinson D, Brant-Zawadzki M. Fluid-attenuated inversion recovery (FLAIR): clinical prospectus of current and future applications. Top Magn Reson Imaging 1996;8:389-396.

Sheena Gurwara, MD; Ahmad Azzawe; Shaunesse Jacobs; Ajay Ravi, MD; Mardjohan Hardjasudarma, MD; and Eduardo Gonzalez Toledo, MD, PhD

Dr. Gurwara recently graduated from the Louisiana State University Health Sciences Center (LSUHSC-S) School of Medicine in Shreveport, Louisiana, and is pursing a residency in radiology. Mr. Azzawe is an undergraduate student at Centenary College in Shreveport, Louisiana. Ms. Jacobs is a student at Captain Shreve High School in Shreveport, Louisiana. Dr. Ravi is a fourth year radiology resident at LSUHSC-S in Shreveport, Louisiana. Dr. Hardjasudarma is professor of radiology at LSUHSC-S in Shreveport, Louisiana. Dr. Gonzalez Toledo is professor of radiology at LSUHSC-S in Shreveport, Louisiana.
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Author:Gurwara, Sheena; Azzawe, Ahmad; Jacobs, Shaunesse; Ravi, Ajay; Hardjasudarma, Mardjohan; Toledo, Edu
Publication:The Journal of the Louisiana State Medical Society
Article Type:Clinical report
Geographic Code:1U7LA
Date:Sep 1, 2010
Words:757
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