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Year :2016
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Month :
July-August
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Volume :
5
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Issue :
3
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Page :
-
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Role of MR Spectroscopy in Differentiating Tumor Recurrence and Post Radiation Changes in Treated Brain Tumors with Radiotherapy
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Correspondence Address :
Madhu SD, Jaipal R. Beerappa, Pr ashanth Kumar Sinha, Raguram P.,
Dr. Madhu SD,
No 20/A, 6th A Main, 11th Cross, 3rd Phase JP Nagar,
Bangalore-560078, India.
E-mail: sdmadhudoc@gmail.com
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Introduction: Introduction: Among the space occupying lesions of brain, gliomas are the most common primary malignant brain tumor and metastases are overall most common intracranial tumors in adults. Assessing the treatment response is routinely done by contrast magnetic resonance imaging (MRI), but MRI being an anatomic imaging technique cannot be accurate in predicting the response to treatment and presents a diagnostic dilemma in assessing the changes due to tumor progression or treatment effects specifically radiation induced changes.
Aim: To evaluate the significance of MR Spectroscopy in differentiation between recurrent tumor and radiation necrosis in patients previously treated for brain tumor using alterations in the ratios of standard brain metabolites— Choline (Cho), Creatinine (Cr), and N-acetyl aspartate (NAA).
Materials and Methods: Total 37 patients with brain tumor (primary/secondary) who were treated with radiotherapy were included in this study. Plain and contrast MRI with multi-voxel MRS was performed at Kidwai Memorial Institute of Oncology, Bangalore. For MRS the volume of interest was placed over the area of signal alteration / abnormal enhancement. The spectra were analyzed for the signal intensity of Choline (Cho), Creatine (Cr), NAA, lipids and lactate and metabolic ratios for Cho/Cr, Cho/ NAA, and NAA/Cr were recorded. Categorization of the lesions into tumor recurrence and radiation necrosis was done on the basis of corresponding findings on SPECT images and clinical follow-up.
Results: On qualitative analysis, both tumor recurrence and radiation necrosis showed area of enhancement on post contrast T1WI. On quantitative analysis of Cho/Cr, Cho/NAA and NAA/Cr ratios, tumor recurrence showed high mean values of Cho/Cr and Cho/NAA and low mean values of NAA/Cr and vice versa. Of the three metabolic ratios Cho/NAA has proved to be the most useful ratio in discrimination between tumor recurrence and radiation necrosis. Cho/NAA of 1.87 or more was found to have a sensitivity and specificity of 95.2 % and 93.8% respectively for presence of tumor (p-value <0.05). Cho/Cr of 1.93 or more was found to have a sensitivity and specificity of 90.5 % and 87.5% respectively for presence of tumor (p value <0.05). NAA/Cr of 1.24 or less was found to have a sensitivity and specificity of 66.7 % and 67.5% respectively for presence of tumor (p-value <0.05).
Conclusion: Metabolic information provided by MR Spectroscopy is useful for the differentiation of tumor recurrence and radiation necrosis in post treated brain tumors after radiotherapy.
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