The Study On The Diagnostic Value With LAVA-FLEX Sequence For Diagnosing Anal Fistula

ObjectiveTo assess the application value of LAVA-FLEX plain and enhanced sequences in determining the type of anal fistula and the characteristics in dynamic inhancement phases.Methods31patients with surgically proved anal fistula underwent MRI examination. The following sequences were obtained:sagittal T2WI/FS、、T2WI/FS axial、T2WI/FS coronary、DWI、LAVA-FLEX, sagittal、axial and coronary LAVA-FLEX+C. Statistical analysis with surgical results was refered as standards. The value of MRI with various sequences in the diagnosis of various types of anal fistulas and their enternal openings was statistically analyzed according to surgical results. SPSS13.0software package was used to perform X2test、t test、analysis of variance and there was statistically significant (P<0.05).Results31patients was found to have10inter-sphincter fistula,26transsphincteric fistulas.5suprasphincteric fistulas,0extrasphincteric fistula. There were38internal openings and35fistula in total. Active anal fistula is full of pus and granulation tissue. It showed low signals in the LAVA plain sequence and high signals in the T2WI/FS sequence. It has low signal fibrous around active fistula Sometimes low signals were mixed with high signals, which represented the interstitial edema. It was showed more clearly in the fat suppression sequence. In LAVA-FLEX enhanced sequence granulation tissue contains rich blood vessels showing high sinals. The inlet was performing round strengthening and the pus in the fistula is charactered by low signal. On the display for internal openings,it showed highest rates reaching up to88.09%in the AX LAVA-FLEX+C. It displays lowest rates of47.62%in the AX LAVA scan. On the display for anal fistula, it shows highest rates reaching up to87.80%in the AX LAVA-FLEX+C. It displays lowest rates of43.90%in the AX LAVA scan. It showed8sequences as follows:AX LAVA+C、 CORLAVA+C、AXDWI、SAGLAVA+C、AXT2WI/FS、CORT2WI/FS、SAGT2WI/FS、AX LAVA in internal openings. It showed8sequences as follows:AX LAVA+C、COR LAVA+C、 SAG LAVA+C、AX DWI、AX T2WI/FS、COR T2WI/FS、SAG T2WI/FS、AX LAVA in anal fistula. It performed X2test, the results of interal openings:X2=28.886, P,=0.000, P,<0.001, the results of anal fistula: X2=42.352, P,=0.000, P1＜0.001, The difference was statistically significant. On the display for internal openings, the LAVA-FLEX inhanced sequence was superior to the LAVA-FLEX plain scan. It was displayde with T2WI/FS sequences combined with LAVA-FLEX inhanced sequence for internal openings and anal fistula, the show rates were AX、COR、SAG from high to low, it was97.62%、85.7%、81%for the endostoma and it was100%、90.2%、75%for the anal fistula.It showed in pairs, AX was better than COR、SAG (P=0.007、0.048resbectively). COR compared with SAG, P=0.393, There was no statistically significant difference. T2WI/FS compared with LAVA-FLEX inhanced sequence wether from internal openings or from anal fistula, LAVA-FLEX inhanced sequence was better than T2WI/FS(P=0.006、0.005), there was statistically significant difference.It was compared with6phases, contrast noise ratio showed from high to low equilibrium phase、venous phase、late arterial phase、coronal phase、 early arteral phase、sagittal phase、plain phase.Contrast inhancement ratio of anal fistula and muscular tissue was highest in the coronal phase. It was early arteral phase、sagittal phase、late arterial phase、venous phase、equilibrium phase for the anal fistula and sagittal phase、 early arteral phase、late arterial phase、venous phase、equilibrium phase for the muscular tissue.The signals were higher and higher from plain phase to equilibrium phase. And it was highest in the equilibrium phase. It rises fastest from venous phase to equilibrium phase. It declined faster form equilibrium phase to coronal phase and it declined slower from coronal phase to sagittal phase. It was the same for the muscular tissue. However, the peak of muscular tissue was lower than that of anal fistula.Conelusion It showed highest rate in AX LAVA+C and lowest rate in AX LAVA for kinds of sequences in MRI for anal fistula. It showed from high to low:AX、COR and SAG. LAVA-FLEX sequence was better than T2WI/FS for showings of internal openings and anal fistula.It showed highest for contrast noise ratio in the equilibrium phase and lowest in the plain phase. Its signal inhancement features were rising slowly and dropping fast. They reached peak in the equilibrium phase However, the peak of anal fistula was higher than that of muscular tissue.