Purpose To investigate the imaging characteristics and accuracy of diagnosing pilocytic astrocytoma (PA) with perfusion weighted imaging (PWI), diffusion weighted imaging (DWI), magnetic resonance sprectroscopy, susceptibility weighted imaging (SWI) and diffusion tensor imaging. Material and Methods MRI imaging of 11 patients with PA was retrospectively analyzed for functional imaging features. Results In 11 patients with PA, there were 9 mixed cystic and solid lesions, 1 case of cystic lesion and 1 case with solid lesion. Ten lesions showed mixed hypointensity on T1WI, and mixed hyperintensity on T2WI and FLAIR. One case was hypointense on T1WI, and hyperintense on T2WI and FLAIR. Prominent contrast enhancement was seen in the solid portion, capsular wall and mural nodules. On SWI 3 cases showed patchy low signal, 2 cases of dot-like low signal and 2 cases without low signal, with average intratumoral susceptibility signal intensity classification of 1.57. PWI findings were characterized by high perfusion with relative cerebral blood volume averaging 2.64±1.22. There was elevated choline component in the solid portion with significantly decreased NAA with average Cho/NAA ratio of 5.13±4.72 (1.46-15.26). Lactate peak was increased in 5 cases. On DWI there was limited diffusion in 1 case. 7 cases did not demonstrate limited diffusion with average relative apparent diffusion coefficient of 1.60±0.58. Conclusion Most MRI features of pilocystic astrocytoma are consistent with low grade glioma. There are characteristic functional imaging findings with higher perfusion than other gliomas. Functional MRI can evaluate tumor metabolism and prognosis.

Objective To investigate the value of vessel size index(VSI) in grading oligodendroglioma by vessel size imaging technique. Methods Twenty-four histologically confirmed oligodendroglioma cases were enrolled (13 gradeⅡand 11 gradeⅢ) . All patients underwent conventional MRI scanning, followed by multi gradient-echo spin-echo sequence from dynamic susceptibility contrast perfusion to generate VSI maps. Region of interests were contoured on VSI color maps to obtain hot-spot value of mean VSI of microvasculature (VSImean) and maximum VSI of microvasculature (VSImax). Paraffin sections of each case was stained with CD34 to acquire microvascular caliber (VShis). Pearson correlation analysis was used to evaluate the correlation between VSImean, VSImax and VShis respectively. Mann-Whitney U test was used to compare VSImean, VSImax and VShis between grade Ⅱ and Ⅲ oligodendrogliomas. ROC analysis was performed to assess the effectiveness of VSImean, VSImax and VShis in grading oligodendrogliomas. Results Both VSImean and VSImax were strongly correlated with VShis (r=0.738, 0.705,P<0.05). For gradeⅡand Ⅲ oligodendrogliomas, VSImean were 38.93(17.96 to 81.18)μm and 91.49(36.94 to 144.68)μm, VSImax were 45.12(22.30 to 89.65)μm and 121.19(57.29 to 164.00)μm, VShis were 8.51(5.25 to 12.76)μm and 11.03(7.59 to 21.96)μm respectively. VSImean, VSImax, and VShis showed significant difference (Z=-3.505,-3.911, -2.729,P<0.05) between grade Ⅱ and Ⅲ oligodendrogliomas. ROC analysis revealed that the optimal cutoff value, sensitivity, specificity and AUC of VSImean was 52.58 μm, 90.91%, 92.31%, 0.923 respectively, 81.18μm, 90.91%, 100.00%, 0.972 for VSImax, and 9.01μm, 90.00%, 84.62%, 0.838 for VShis respectively. Conclusions Vessel size imaging derived VSI correlated well with histopathology. It could provide valuable information in the pre-operative grading of oligodendroglioma.

Objective To assess the value of clinical applications of whole-body diffusion-weighted imaging (WB-DWI) in diagnosing patients with malignant tumors compared with positron emission tomography (PET). Methods A total of 22 patients with highly suspected malignant tumors underwent WB-DWI after PET. The differences between the two imaging methods were compared in displaying lesions, and the correlation between ADC and SUV value was analyzed. Results More lesions were showed with WB-DWI than PET. There was no significant difference between the two methods in detecting the lesions of lung, mediastinal septum or abdomen (P>0.05), but more lesions in skeleton were showed with WB-DWI (P<0.05). No significant correlation between ADC and SUV value was found. Conclusion Compared with PET, WB-DWI can detect more tumor lesions. The sensitivity of WB-DWI in detecting metastatic tumors of bone is higher than that of PET.