Susceptibility-weighted Imaging In Grading Brain Astrocytoma

Objectiv:To evaluate the value of the small vessels,microbleeds and periturnoral edema in Susceptibility-weighted imaging(SWI) in grating brain gliomas and difference between SWI and Conventional imaging techniques.Methods:A series of 22 patients(10 males and 12 females,21-79years old,mean age 49.1 years) with a diagnosis of glioma were included in the study.There were 16 patients who reported symptoms of dizziness and headache for 5 days to 2 years.5 patients had Limb asthenia:2 patients appeared nausea and vomiting;one had hemi-anesthesia.Tumor was divided into tow groups,high-grade and low-grade.Both of the two groups didn't carry out radiotherapy and chemotherapy before MR examination.All examinations were performed on GE 3.0 MRI scanner(General Electric medical systems,USA) with 8-channel array coil.The scanning sequences included the conventional MR sequences and SWI sequence.The conventional MR sequences used were as follows:(SE) T1-Weighted images FLAIR(TR 2580ms,TE 23ms,TI 860ms),(FSE)T2-Weighted images(TR 4600ms TE 110ms),FLAIR(TR 9602ms TE 117ms TI 2400ms) and enhanced T1WI.The slice thickness =5.0mm,FOV=240mm×240mm,and slice interval was 1.5mm.The contrast injection was a normal dose(0.1mmol/kg) of gadolinium chelate after plain scan.All patients undergone pre-and post-contrast SWI scanning.The parameters were following:TR 32ms;TE 22ms;FA 15;slice thickness=2mm;matrix size= 320×384; FOV 230mm×173mm.Scanning range should keep clear of parts containing air such as bilateral petrous pyramid.frontal sinus and sphenoidal sinus,if not,we could use presaturation slab were used to cover it.we got a minimum intensity projection(MIP) of the pre-enhanced SWI images(SWI-MinP) by the adw4.3 workstation software. And minimum and maximum density projection(CE-SWI-MinP and CE-SWI-MaxIP )of the enhanced SWI with the same method.Correlated parameters were:slice interval=1.5mm,slice thickness=5.0mm,which can matched the slice thickness of the relevant sequences.All cases were confirmed by operation or biopsy, grading was according to the World Health Organization(WHO)2000 classification of astrocytomas,intratumor hemorrhage shew up in the MR sequences Corresponded to pathology.Two radiologists independently diagnosed image data of 22 patients without knowledge of the surgical or pathological results.By the post-processing function of adw4.3 workstation,they counted of the number of small vessels and measured the volume of hemorrhage and peritumoral edema.Low-signal structures that could be followed on contiguous images and had cylindrical structure were condidered to represent small vessels.Irregular low-signal region on SWI were assumed to represent hemorrhage when the signal correlated with corresponding T1- and T2-weighted signals.High-signal region around tumor were assumed to represent peritumoral edema.By the method of statistical analysis software SPSS13.0,differences between routine sequences(T1WI,T2WI,FLAIR,CE-T1WI) and SWI sequences (SWI-MinIP,CE-SWI-MinP和CE-SWI-MaxIP) in venules,microhemorrhages and peritumoral edema were analyzed by Kruskal-Wallis test.Then advanced comparison were carried out among those sequences by Mann-Whitney test.At last Wilcoxon test for independent two samples was used to analyze the difference between high-and low-grade astrocytomas in the terms of venules and microbleeding displayed in the SWI.if p＜0.05,it had difference,and if p＜0.01,it had significant differences. Results:Intratumorally small vessels and microhemorrhages were demonstrated both in Conventional imaging sequences and SWI sequences with different degree in 22 patients with astrocytoma,of which 9 were gradeⅠ-Ⅱ,and 13 were gradeⅢ-Ⅳ.With Kruskal-Wallis test,p＜0.01 accept accepted that there were difference in the number of small vessels and microbleeding volume which were showed in every sequence.About the demonstration of intratumoral small vessels and microbleeding volume,interclass analysis showed that T1WI and CE-T1WI did not show small vessels and microbleeding very well,while T2WI and FLAIR better,SWI best,p＜0.01.Comparing SWI-MinIP image with CE-SWI-MinIP image,p=0.724 in small vessels,p=0.869 in microbleeding,both of them obviously exceed to 0.05.And there was difference in demonstration of CE-SWI-MinIP image and CE-SWI-MaxIP image,p=0.038 in small vessels,p=0.019 in microbleeding.For the demonstration of intratumoal architecture include small vessels and microbleeding of 22 patients, CE-SWI-MaxI was better than PCE-T1WI(P＜0.01).As result shows,the demonstration of intratumoral small vessels has significant difference between the two groups,the demonstration of microbleeding and peritumoral edema has statistical difference.Low grade tumor has less haemorrhage, small vessels and peritumoral edema.Conclusion:SWI is useful in showing characteristics of brain astrocytoma,and it is valuable in grading the tumors.The vessels vasculature,blood products and peritumoral edema in SWI is useful in estimating the degree of angiogenesis of brain astroeytoma.