| Background:Anorectal fistula is an infectious tract between anorectal and skin around anus.Although anal fistula is not life-threatening,it seriously affects the quality of life of patients’,because the course of the disease is repeatedly prolonged and difficult to cure,and it occurs in the private parts of the body,and even causes psychological problems in some young patients.Surgery is the main treatment of anal fistula,but many cases contain branches,hidden secondary fistula or smaller abscess,these lesions with low naked eye resolution are easy to be ignored,resulting in a high recurrence rate after anal fistula operation.Accurate preoperative diagnosis of anal fistula is the key to its complete cure.MRI technology is recognized as the best preoperative examination method.3D-SPACE sequence has significant advantages of omni-directional imaging and high resolution,so it tends to replace the traditional sequence scanning.In order to achieve the effective use of this technology to maximize its advantages,and inspired by image fusion technology,the author team took the lead in trying to reconstruct a single sequence of three-dimensional images and use multi-modal fusion images to diagnose anal fistula.This study is a retrospective analysis.Based on the 3D-SPACE sequence,the author first evaluates the diagnosis of anal fistula by image fusion technology to study whether the imaging effect and diagnosis rate are different from the surgical standard diagnosis.In the further study,through the comparison of fusion images and contrast-enhanced images,the characteristics of anal fistula imaging were identified,and the diagnostic consistency was analyzed deeply with the standard reference of surgical diagnosis.Objects:1.Based on the fusion of specific sequence(3D-SPACE-T2WI to 3D-SPACE-STIR),the imaging effect and diagnostic rate of anal fistula were analyzed,and the value of image fusion in the diagnosis of anal fistula was explored.2.Through the comparative analysis of fusion images and contrast-enhanced T1WI-FS images,the imaging quality and diagnostic consistency of anal fistula were studied,and an alternative examination scheme was provided for patients with renal insufficiency or contrast medium allergy.Methods:1.The patients with anal fistula confirmed by operation and pathology in our hospital were retrospectively analyzed and selected into the group.All patients were examined by 3D-SPACE-T2WI and 3D-SPACE-STIR sequence within 1 week before operation.The image quality of 3D-SPACE-T2WI,3D-SPACE-STIR sequence and the image fusion of 3D-SPACE-T2WI to 3D-SPACE-STIR were quantitatively scored by 2 experienced doctors.The scores of fistula and sphincter were calculated and added to the total score.Pairwise t-test analysis was used to analyze the scores of each group.The display rate of internal opening and fistula/branch in each group was calculated and the difference of diagnosis rate among the three groups was compared(P<0.05).2.The patients with anal fistula confirmed by operation and pathology in our hospital were analyzed retrospectively and selected into the group.all patients were scanned by 3D-SPACE-T2WI,3D-SPACE-STIR and contrast-enhanced T1WI-FS sequence within one week before operation.The numbers and location of internal opening,fistula/branch numbers and shape,and anal fistula classification of each case were counted and diagnosed in fusion images and contrast-enhanced images.With reference to the surgical and pathological diagnosis,the imaging diagnosis is considered to be consistent with the diagnosis.The positive rate of fusion images and contrast-enhanced T1WI-FS images in the diagnosis of anal fistula was statistically analyzed,and the consistency of kappa was analyzed.The number of cases of Parks typing in the two sequences was counted,and the kappa consistency analysis was compared with the surgical diagnosis.Results:1.A total of 68 patients were included,including 73 internal opening and 84 fistulas and branches.The scores of fistula and sphincter in 3D-SPACE-T2WI,3D-SPACE-STIR and fusion images were 2.97,4.25,4.32 and 4.38,2.62,4.43 respectively,and the total scores were 7.35,6.86,8.74.There was no significant difference in the image quality of sphincter between the fusion images and the 3D-SPACE-T2WI group.In the scores of other groups,the quality of fusion images was better than that of individual sequence groups.The internal opening count(detection rate)of anal fistula in the three groups was 64(87.7%),67(91.8%)and 70(95.9%)respectively,and the fistula/branch count(detection rate)was 76(90.5%),78(92.9%)and 82(97.6%),respectively.The comparison of the diagnostic rate of internal opening was x2=3.269,P=0.195 for fistula and x2=3.737,P=0.154 for fistula,and there was no significant difference among the groups(P>0.05).2.Among the 46 patients,52 internal opening and 61 fistula-branches were confirmed by operation.Parks classification included intersphincteric fistulas:26 cases,transsphincteric fistulas:15 cases,suprasphincteric fistulas:3 cases and extrasphincteric fistulas:2 cases.The sensitivity of fusion images to the diagnosis of internal opening of anal fistula was 82.6%,and the contrast-enhanced T1WI-FS was 84.8%.The comparison of the diagnostic rate of internal opening was χ2=0.08,P=0.778,the difference was not statistically significant,and the consistency was good(Kappa=0.761).The sensitivity of fusion images to fistula diagnosis was 80.4%.and the contrast-enhanced T1WI-FS was 82.6%.The comparison of the diagnostic rate of internal opening was x2=0.072,P=0.788,,the difference was not statistically significant,and the consistency was good(Kappa=0.784).In the fusion images,the number of cases of Parks classification:intersphincteric fistulas:23 cases,transsphincteric fistulas:14 cases,suprasphincteric fistulas:2 cases,extrasphincteric fistulas:2 cases,Kappa=0.812.The number of cases classified in contrast-enhanced T1WI-FS sequence was intersphincteric fistulas(n=24),transsphincteric fistulas(n=13),suprasphincteric fistulas(n=2),extrasphincteric fistulas(n=2)and Kappa=0.809.The two methods are highly consistent with surgical diagnosis.Conclusion:1.The fusion images have the advantages of a single sequence,and the image quality is better.2.In the diagnosis of anal fistula,the diagnostic rate of fusion image is not different from that of single 3D-SPACE-T2WI or 3D-SPACE-STIR sequence,so it can be used in the diagnosis and evaluation of anal fistula,which is a more efficient and direct imaging method.3.The fusion images and the contrast-enhanced T1WI-FS images are consistent with surgical and pathological diagnosis,and The fusion images can be used as an alternative for patients with enhanced MRI taboos. |
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