| Background and Objective: Being the improvement of the hardware and software of magnetic resonance imaging (MRI), the new imaging technique and scanning sequence appearanced uninterruptedly, an original promising and first light of morning occurred for clinical diagnosis and differential diagnosis in cerebral diseases by application of the diffusion weighted imaging (DWI) and magnetic resonance spectroscopy (MRS). DWI was an unique method to present the changes of motion of the water molecule in the human body by performing the molecular diffusion measurement and imaging. DWI could reflect the microstructure of the tissue, the internal feature of the micromovement, and the unique information in functional status of the brain on molecular level. MRS was a method for the definite nucleus and chemical compound to carry out quantitative analysis with the effect of magnetic resonance and chemical shift(CS), and no invasive tool to detect the changes of the metabolism in vivo. The intracranial cystic diseases (ICD) is a serious and common disease for human being. The ICDS include necrotic-cystic intracranial tumor (NCIT), brain abscess (BA), cerebral cysticercosis (CC), epidermoid cyst (EC), arachnoid cyst (AC) and so on. Domestic and abroad researchers are trying to apply the DWI and MRS to investigate ICD, and become a hot spot. Although the majority of ICD could be diagnosed correctly by routine CT and routine MRI sequence, such as: T1WI,T2WI and fluid attenuated inversion recovery (FLAIR), but it is difficult for the part of ICD to diagnose exactly before preoperation. Because of this, the research is planning to compare with the routine plain scan of MRI, and estimate the value of DWI and 1H-MRS (proton magnetic resonance spectroscopy,1H-MRS) for diagnosis of ICD.Materials and methods: 76 patients with ICD have been collected from 2005.10 to 2007.3. The conventional T1flair, T2WI ,DWI and /or single voxel 1H-MRS (SV 1H-MRS) or multivoxel 1H-MRS (MV 1H-MRS) were performed with GE signa 1.5T supraconduction magnetic resonance. All patients were conformed by postoperative pathology or clinical follow-up. There were 37 necrotic-cystic intracranial tumor, 12 metastatic tumors, 4 acoustic nerve tumor, 3 meningiomas and 2 hemangioblastoma. 12 brain abscess, 5 cerebral cysticercosis, 10 epidermoid cyst and 12 arachnoid cyst in 76 patients with ICD. There are astrocytoma (AS) (16 cases grade I 1, grade II 3, gradeIII 5, gradeIV 7) in 37 patients with NCIT . DWI was performed using single short SE-EPI sequence with two different b values (0s/mm2 and 1000s/mm2). 1H-MRS was performed with PRESS(point-resolved spectroscopy, PRESS) sequence. The correlative date from DWI and 1H-MRS were processed.All experimental result were expressed by ( x±s ) , statistic analysis is carriedout by the SPSS 11.5 software for the two-sample-t-test and one-way ANOVA comparision among the three groups, with its significant levelα=0.05.Results: (1) The positive ratio of ICD on DWI (92.1%) is higher than that on conventional T2WI and T1flair (85.5%)(P>0.05), but the positive ratio of edema around nidus on DWI(10.5%) is lower than that on conventional T2WI and T1flair (64.5%) (P<0.01). There are 4 types of signal appearances in these cystic lesions on DWI : type I was high signal, ADC value was increased to compare with the contralateral corresponding brain tissue (n=19); type II was high signal, ADC value was decreased to compare with the contralateral corresponding brain tissue (n=4); type III was lower signal, ADC value was increased to compare with the contralateral corresponding brain tissue (n=44); type IV was mixed signal, ADC value was increased to compare with the contralateral corresponding brain tissue (n=9). (2) Mean ADC value of the necrotic-cystic zone of astrocytoma(n=16) (1.412±0.689)×10-3mm2/s, metastatic tumor(n=12) (1.313±0.750)×10-3mm2/s, acoustic nerve tumor(n=4) (1.316±0.351)×10-3mm2/s and cerebral cysticercosis(n=5) (1.250±0.680) ×10-3mm2/s, were not statistically significant (P>0.05). The differences of mean ADC value among astrocytoma (1.412±0.689)×10-3mm2/s, metastatic tumor (1.313±0.750)×10-3mm2/s and acoustic nerve tumor(n=4) (1.316±0.351)×10-3mm2/s, were not statistically significant between the three groups (P>0.05). (3) The differences of mean ADC value the necrotic-cystic zone between astrocytoma grade I～II (n=4) [(1.631±0.218)×10-3mm2/s] and astrocytoma grade III～IV(n=12)[ (1.157±0.162)×10-3mm2/s] were statistically significant (P<0.01); There was significant difference between the mean ADC value of different grade astrocytoma and that of the contralateral corresponding brain tissue (P<0.01). (4) 37 NCIT parenchyma mean ADC value [(1.32±0.109)×10-3mm2/s], edema ADC value [(1.80±0.115)×10-3mm2/s] and the necrotic-cystic zone ADC value [(2.48±0.156)×10-3mm2/s] existed significant difference (P<0.01). (5) Mean ADC value of brain abscess(liquor puris) (n=12) [(0.63±0.199)×10-3mm2/s] is lower than that of the zone of necrotic-cystic intracranial tumor[(2.50±0.162)×10-3mm2/s] (P<0.01), there was significant difference between brain abscess and contralateral corresponding brain tissue (P<0.01). (6) Epidermoid cyst ADC value was (1.21±0.993)×10-3mm2/s, arachnoid cyst ADC value was (2.98±0.232)×10-3mm2/s. Epidermoid cyst ADC value was higher than that of the contralateral corresponding brain tissue(0.94±0.049)×10-3mm2/s and there was significant difference between them(P<0.01). Arachnoid cyst ADC value was higher than the contralateral corresponding brain tissue and there was significant difference between them(P<0.01), epidermoid cyst ADC value was lower than arachnoid cyst ADC value and there was significant difference between them P<0.01). In 37 cases of NCIT, the necrotic-cystic zone showed NAA (N-acetylaspartate, NAA), Cho(choline, Cho) and Cr (creatine, Cr) in 37 cases, showed Lac (lactate, Lac) in 17 cases, showed Lip(lipids, Lip) in 12 cases. In 12 cases of brain abscess (liquor puris), 10 cases showed AA(valine, leucine, isoleucine) and Lac, 5 cases showed Ace(acetate, Ace), 6 cases showed Suc(succinate, Suc), 6 cases showed Ala(alanine, Ala), 4 cases showed Glu(glutamine, Glu). In 5 cases of cerebral cysticercosis, all 5 cases showed Lac, Suc, Ace and Ala. There was only Lac in 5 epidermoid cyst. In 6 cases of arachnoid cyst, only 3 cases showed little Lac. (8) NAA [(236.17±130.46) and (670.23±128.34)], Cho [(782.57±212.32) and (538.72±142.09)],NAA/Cr (N-acetylaspartate/creatine, NAA/Cr) (0.92±0.41) and Cho/Cr (choline/creatine, Cho/Cr) (1.52±0.38) between the parenchyma of necrotic-cystic intracranial tumor and contralateral corresponding brain tissue had significant difference (P<0.01). The metabolin value of NAA[(368.10±112.42) and (845.13±228.16)],Cho[(782.57±212.32) and (723.00±154.19)] between the paries of the brain abscess and contralateral corresponding brain tissue existed significant difference (P<0.01). NAA/Cr[(1.28±0.61) and (1.42±0.18)],Cho/Cr[(1.79±1.22) and (1.23±0.38)] between the paries of the brain abscess and contralateral corresponding brain tissue had no significant difference (P>0.05). (9) NAA[(236.17±130.46) and (368.10±112.42)], Cho[(782.57±212.32) and (368.10±112.42)], and Cho/Cr[(3.22±1.62) and (1.79±1.22)] between the parenchyma of necrotic-cystic intracranial tumor and the paries of the brain abscess existed significant difference (P<0.01). NAA/Cr NAA/Cr[(0.92±0.41) and (1.28±0.61)] between the parenchyma of necrotic-cystic intracranial tumor and the paries of the brain abscess had no significant difference (P>0.05).Conclusion: (1) Both DWI and 1H-MRS are the effective MR technology to diagnose and differentiate the intracranial cystic diseases. (2) DWI and 1H-MRS might distinguish the brain abscess from cyst-necrosis zone of necrotic-cystic intracranial tumor effectively. (3) DWI could distinguish the epidermoid cyst from the arachnoid cyst effectively. (4)1H-MRS examination is difficult to distinguish the epidermoid cyst from the arachnoid cyst effectively.
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