To determine and compare the accuracy of contrast-enhanced magnetic resonance imaging (MRI) and Technetium 99m glucohepatonic acid single photon emission computed tomography (99mTc-GHA SPECT) in grading of gliomas, compared with neuropathologic findings.
Materials and Methods:
The study included 20 adult patients (13 men and 7 women) with clinical/radiological suspicion of brain tumor (glial tumor) who were subjected to magnetic resonance examination and 99mTc-GHA brain SPECT.
The lesions were evaluated by using MRI imaging score, based on 9 MRI criteria. Based on the discrimination threshold of 0.9 for mean MRI score, the gliomas were graded as low- or high-grade glioma. The 99mTc-GHA SPECT retention index was calculated as the ratio between delayed and early uptake ratios. Based on the discrimination threshold of 1 for 99mTc-GHA SPECT retention index, the gliomas were graded as low- or high-grade glioma.
The diagnosis was verified by means of histopathologic examination in all patients (open surgery in 19 patients and stereotactic biopsy in 1 patient). Correlation between MRI findings/scores, SPECT scores, and histopathologic grades was done in all the patients, and comparison between MRI and 99mTc-GHA SPECT was made using paired Student t test and correlation coefficient.
The study revealed significant difference between the mean MRI scores and early uptake ratio, delayed uptake ratio, and retention index of low-grade (grades I-II) and high-grade (grades III-IV) gliomas. No statistically significant difference could be demonstrated between the abilities of contrast-enhanced MRI and 99mTc-GHA SPECT to allow differentiation between high- and low-grade gliomas. The accuracy of MRI (78.4%), however, was slightly higher than that of 99mTc-GHA SPECT (73.68%). However, 99mTc-GHA SPECT allowed differentiation between high-grade gliomas (between grades III and IV gliomas).
The accuracy of contrast-enhanced MRI in the distinction of high- and low-grade malignancy was higher than that of 99mTc-GHA SPECT. The performance of 99mTc-GHA SPECT adds little in determining tumor grade when MRI is performed. However, it may act as a useful adjunct to differentiate between grades III and IV gliomas.