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Objective To evaluate the diagnostic value of MR diffusion-weighted imaging in intracranial cystic lesions for a reliable imaging basis of the correct diagnosis of disease and the best treatment programs.Methods Siemens Magantom Symphony 1.5 T Magnetic resonance scanner with quadrature head coil.69 cases of intracranial cystic lesions with pathologic confirmation or clinical follow-up underwent routine MRI and DWI and enhanced scanning. The Conventional MR scans including axial T1WI, T2WI and coronal T2-FLAIR, sagittal T1WI. The parameters (TR/ TE) are as follows:420ms/8.7 ms (SE-T1WI),4200 ms/100 ms (TSE-T2WI), and 9720 ms/ 100 ms (T2-FLAIR, TI= 2500 ms), FOV 240×198, slice thickness 5 mm, spacing 2 mm, matrix 256x224, NEX=2. The single-shot echo-planar sequence (SE-EPI)were used in DWI, parameters:TR/TE:3400 ms/108ms, the thickness, spacing and FOV in line with conventional scanning.In the vertical dimension of each option (S), phase coding (P) and the frequency codes (M) 3 is applied diffusion gradient directions, take two proliferation-sensitive factor b (value)= 0 s/mm2 and b=1000 s/mm2, scan time 39s. Gd-DTPA(0.1mmol/kg) was injected from the forearm vein for axial, sagittal and coronal T1WI enhanced scanning, the images were post-processed after all inspections have been completed.Use of the axial ADC image as a measurement plane and ADC value as indicators of the size of dispersion degree of, select the largest lesion diameter line level, and quantitative measurement the apparent diffusion coefficient (ADC) values of different types of cystic lesions. Pairwise comparison analysis of variance the average ADC value of various diseases, to discussion the differences between different groups and evaluation of the significance of DWI for differential diagnosising the intracranial cystic lesions.Results 69 cases of cystic brain lesions, including 38 cases of brain tumors (6 cases of astrocytoma, anaplastic astrocytoma in 5 cases,8 cases of glioblastoma, brain metastases in 12 cases,acoustic neuroma 7 cases),15 cases of brain abscess, arachnoid cyst in 8 cases and 8 cases of epidermal cyst. The DWI performance of the local of cystic degeneration of vrious types of diseases:In 38 cases of brain tumors in addition to 3 cases of patients with glioma showed high signal (1 astrocytoma,1 anaplastic astrocytoma,1 metastatic tumor case), the remaining 34 cases were low signal. High signal were observed on the cases of 15 cases of brain abscess. The 8 cases of arachnoid cysts were low signal,and 8 cases of epidermoid cysts showed high signal. The ADC values of necrotic areas of the various types cystic lesions:glioma (2.35±0.82)×10-3mm2/s, metastatic tumor (2.82±0.76)×10-3mm2/s, acoustic nerve tumor (2.70±0.38)×10 -3mm2/s, brain abscess (0.58±0.19)×10-3mm2/s, arachnoid cyst (2.92±0.40)×10-3mm2/s, epidermoid cyst (0.93±0.15)×10-3mm2/s.There was significant difference between the ADC valuers of brain tumors(glioma, metastatic tumor, acoustic neuroma)and brain abscess(P<0.01), and there was significant difference between the ADC valuers of arachnoid cyst and epidermoid cyst(P<0.01). However, there were no significant differences among the ADC valuers of glioma and metastatic tumors, acoustic neuroma (P> 0.05).Conclusion The values of DWI and ADC values have important contribution to the differentiation of cystic or necrotic tumors from brain abscesses, there are obvious advantages in differentiating epidermoid cysts and arachnoid cysts,and DWI is the preferred way to check.Intracranial cystic lesions showing hypointense signal on DWI can exclude the exception brain abscess and epidermoid cysts.However, it can not fully identify the nature of cystic lesions of the brain if rely solely on DWI signal level and ADC values, the conventional MRI and enhanced should be combined. In a word, it is helpful in the diagnosis and differential diagnosis of differential diagnosis of intracranial cystic lesions based on DWI and ADC values of high and low signals, but there are some certain limits. Further study of the value of DWI and ADC values in the identification of tumor grade are needed to continue.
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