Brain metastases are the most common tumors in the human central nervous system (CNS), with an occurrence 10 times higher than primary brain tumors in adults. A radiologist usually diagnoses these tumors. Typically, magnetic resonance imaging (MRI) has been used to evaluate the status and number of metastases, the design of surgical treatment or radiotherapy, and the response to treatment. This study aimed to consider the origin of metastatic tumors of the brain using diffusionweighted imaging

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... equence. Methods: In this study, 95 lesions observed in 51 patients with different types of brain metastasis who analyzed with standard brain MRI protocols such as T2-weighted fast spin-echo in sagittal, coronal and axial planes and T1-weighted spin-echo sequences before and after injection of contrast enhancement and diffusion-weighted imaging. The diffusion-weighted imaging included an echoplanar spin-echo sequence with two b values (0,1000 s/mm) and calculated apparent diffusion coefficient (ADC) maps. We measured the ADC-value on normalized ADC maps and compared them with different methods. ANOVA was used to compare ADC among all groups as well as T-test for every two groups. Results: The results showed that patients with lung cancer (squamous cell carcinoma, SCC) had the lowest mean ADC (658.70*10-3 mm2 /s) and breast cancer patients with the highest mean ADC(935.52*10-3 mm2 /s). This study demonstrated that most Brain metastases had low and intermediate ADC values. The analysis showed no significant difference among all groups. However, ADC values in breast cancer and kidney and lung (adenocarcinoma) were statistically higher in comparison to other groups. There were no critical discrepancies between ADC values in brain metastases from Breast cancer and lung cancer (adenocarcinoma) and kidney. Conclusion: It seems that evaluating the origin of the brain metastatic tumors by using diffusion imaging (DWI) parameters could be helpful to prevent invasive methods like biopsies in some situations. Although it needs more studies to achieve this purpose.