Abstract:
Purpose
To evaluate the role of magnetic resonance spectroscopy & diffusion weighted imaging (DWI) in differentiating between primary and secondary brain tumors.
Patients & methods
This prospective study was performed for 40 patients. Diffusion weighted image (DWI) and apparent diffusion co-efficient (ADC) maps were acquired by using b-values of 0 and 1000 mm2/s. Standard mean ADC values were calculated automatically and expressed in 10−3 mm2/s in both intra-lesional and peri-lesional regions. Multi voxel MR spectroscopy was performed using a spin-echo mode sequence.
The metabolites were identified including the following: N-acetylaspartate (NAA) at 2.0 ppm, creatine (Cr) at 3.0 ppm, choline (Cho) at 3.2 ppm, lipid at the range of 0.7–1.3 ppm, lactate at 1.33 ppm and myoinositol at 3.56 ppm. The ratios that were calculated include the following: Cho/NAA and Cho/Cr in both intralesional and perilesional regions.
Results
Intralesional ADC values showed no difference between the metastases (0.6: 1 × 10−3 mm2/s with mean 0.86) and high grade primary tumors (0.6: 1.1 × 10−3 mm2/s with mean 0.73). Perilesional ADC value Findings in the study revealed that primary tumors have low ADC values (0.9: 1.1 × 10−3 mm2/s with mean 0.95) in their peri-lesional voxels denoting peri-lesional infiltration, while higher ADC values in metastasis (1.3–1.6 × 10−3 mm2/s mean 1.41) due to the absence of peri-lesional infiltration increase in CHO/Cr ratios (>1) in primary high grade tumors (indicating perilesional infiltration) while there was no increase in CHO/Cr ratio in cases of metastases. Low grade primary tumors showed low lactate and lipid, with increasing malignancy, and tumors showed increasing levels of lactate and lipid peaks (indicating necrosis) with remarkable difference in lipid peaks between low and high grade tumors. There was no significant difference between primary & metastatic brain tumors as regards lactate peak.
Keywords
Magnetic resonance imaging; Brain tumor; MRS; DWI.
Citation: Abdel Monem Nooman Darwiesh, Noha Mohamed Abd-El Maboud, Alaa Mohamed Reda Khalil, Ahmed Mostafa ElSharkawy Role Of Magnetic Resonance Spectroscopy & Diffusion Weighted Imaging In Differentiation Of Supratentorial Brain Tumors http://dx.doi.org/10.1016/j.ejrnm.2016.05.005
Received: 14 March 2016, Accepted: 10 May 2016, Available online: 4 June 2016
Copyright: © 2016 The Egyptian Society of Radiology and Nuclear Medicine.Production and hosting by Elsevier. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Conclusion
From the current study it can be concluded that the combination of MR spectroscopy and DWI with ADC values calculation could improve the diagnostic efficacy of MR imaging in the diagnosis and grading of malignant brain tumors. Intra-lesional ADC values are not useful in the differentiation between primary and metastatic tumors with no valuable changes. Perilesional ADC values can differentiate between primary & metastatic brain tumors.
MRS may enable differentiation between lesions showing similar aspects on conventional MRI. Choline is considered the most specific marker of intracranial neoplasm. Increase in Choline levels and Choline/NAA ratios are very suggestive of the malignant nature of the neoplasm, its grading and its follow-up to evaluate the response of the treatment.
Conflict of interest
The authors declare that they have no conflict of interest.
