| Purpose:To study the feature and time intensity curve(TIC) pattern of nasopharyngeal carcinoma(NPC) on dynamic contrast-enhanced(DCE) MRI at 3.0T,and compare the efficacy of DCE MRI with contrast-enhanced TIWI on evaluating T-staging of nasopharyngeal carcinoma,then optimize the multiphase DCE protocol.Material and methods:Seventy-six consecutive cases of NPC proved by pathology of nasopharyngeal biopsy were undergone MRI examinations at 3.0T device(SIGNA EXCITE HD,GE) including non-enhanced series,DCE-MRI and contrast-enhanced T1(axial FSE with fat-suppression).DCE-MRI performed by LAVA series(liver acquisition with volume acceleration)(axial,scan phases:phasel of pre-contrast and phase2 to 13 with 20s each phase scanning from 20 to 240s after contrast media administration).TIC pattern of tumor,skull base erosion(SBE) and muscle were divided into five types as type A (Tpeak=60s,washout rate=20%),type B(Tpeak=60s,washout rate=20%),type C(Tpeak=60s,washout rate=20%),type D(persistently ascending),type E(low and flat). The TIC of tumor,SBE,normal muscle and fat were obtained,and the phases with the maximal signal intensity ratio(SIR) of tumor/muscle(T/M) and tumor/fat(T/F) could be available.Statistical test were conducted to compare T/M SIR and T/F SIR on DCE phase2 to 4 with contrast-enhance FSE-T1-FS.McNemar way was used to analyze the demonstration of surrounding tissue invasion of NPC on LAVA DCE MRI and contrast enhanced FSE-T1-FS.The invasion of surrounding tissue and skull base at each phase of DCE and contrast-enhanced FSE-T1-FS were evaluated by the standard of score1=unable to or unclearly display,score2=disply clearly.The number of lymph nodes detected by phase2 to 13 of DCE and contrast enhanced FSE-T1-FS were caculated respectively.Results:TIC pattern of tumor,SBE and muscle showed type A:47%,8%,0%,typeB:34%,15%,0%,typeC:13%,13%,28%,typeD:5%,49%,87%,typeE :only seen in all fat.The maximal T/M SIR and T/F SIR occured at phase 2 to 4 were 50%,30%,9%and 18%,36%,14%respectively.The mean T/M SIR and T/F SIR at phase2 to 4 of DCE and contrast-enhanced FSE-T1-FS were 2.03±0.49,2.07±0.44,1.93±0.34,1.41±0.16 and 5.95±2.52,6.57±2.82,6.25±2.54,2.28±0.45 respectively.One-way ANOVA and multiple comparison showed statistical differences of T/M SIR and T/T SIR between anyone of DCE phase 2 to 4 and contrast-enhanced T1 respectively,but no differences were observed within these three DCE phases.To cases of SBE(n=39),the percentages of score3 at phase 2 to 13 of DCE and contrast-enhanced T1 were 0,33%,46%,67%,79%,100%,100%,100%,100%,100%,100%,100%,100%.On displaying local tumor extent,LAVA DCE-MRI were superior or equal to contrast-enhanced FSE-T1-FS in invasion of pterygopalatine fossa:58%Vs57%,parapharyngeal space:58%Vs57%,but no statistical differences were existed.On DCE-MRI,The soft tissue invasion cannot be fully displayed at phase2 to 4 of DCE,and the skull base erosion were unable to be fully showed at phase2 to 6,and lymph nodes failed to be detected completely at phase 2 to 3.On multiphase DCE-MRI,92%(70/76) soft tissue invasion and 33%(13/39) skull base erosion were demonstrated at phase3,and skull base erosion were displayed clearly among phase7 to 13.Conclusion:LAVA DCE-MRI at 3.0T could show definitely on evaluating T-staging of NPC compared with contrast-enhanced T1WI.After contrast administration,images acquired at 40s combined with another phase more than 120s were enough to show all the invasion of local tissue and skull base erosion,which can be helpful to evaluate the T-staging of NPC. |
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