Time is money: ultrashort protocol of MRI fistulogram for perianal fistulae

Transcription

1 Time is money: ultrashort protocol of MRI fistulogram for perianal fistulae Poster No.: B-0376 Congress: ECR 2017 Type: Scientific Paper Authors: A. Balani, S. Shaikh, D. A. KUMAR, S. Alwala, S. Marda, C CHATUR ; Secunderabad/IN, Hyderabad/IN Keywords: Abdomen, Gastrointestinal tract, MR physics, MR, Image manipulation / Reconstruction, Experimental, Physics, Costeffectiveness, Imaging sequences, Fistula, Outcomes DOI: /ecr2017/B-0376 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 19

2 Purpose Perianal fistula is a chronic granulating track connecting perianal skin with anal mucosa. Quiet common and is associated with considerable discomfort and high morbidity. MRI is excellent in the diagnostic work-up of patients with perianal fistulae. However, a standard protocol for imaging is not available. AIMS and OBJECTIVES: To formulate state of art Ultra-short protocol of MRI fistulogram To evaluate the accuracy of ultra-short protocol in mapping of perianal fistulas by correlating MRI findings with intraoperative findings. Methods and materials Following ethical committee approval, 45 patients with suspicion of or having a past history of perianal fistula were included. Written informed consent was taken. Ultra-short protocol was done utilizing phased array coil on GE Signa HDxt 1.5T machine Workstation was Advantage Workstation (AW 4.3) Inclusion Criteria: Patients with suspicion of or having a past history of perianal fistula were included. Patients undergoing surgery in our institute. Exclusion Criteria: Patients refusing consent to be included in the study Contraindications for MRI (with or without contrast agents): Patients having - Brain Aneurysm Clip - Implanted neural stimulator - Implanted cardiac pacemaker or defibrillator - Cochlear implant Page 2 of 19

3 - Ferromagnetic Ocular foreign body - Other implanted medical devices: (eg Swan Ganz catheter) - Insulin pump - Metal shrapnel or bullet - Patients with surgery of uncertain type where the presence of metal clips or wires cannot be excluded. Ultrashort Protocol: Sequence Time (min:sec) TR / TE Thickness Slices (mm) / Gap (mm) Nex ETL (number (Echo of train excitations)length) Survey T2 3D fat 04:55 suppresed FSE (CUBE) 2000 / / T2 Axial FSE 2440 / 85 5/ :20 04:24 Total time of Ultrashort protocol : 9 mins 19 seconds Results The most common age group was 31 to 50 years ( Fig. 1 on page 5 ) with 82.2% pts being males ( Fig. 2 on page 6 ). Intersphincteric fistula was the most common type found in 25(55.5%) cases, followed by transsphincteric type in 17(37.7%) cases ( Fig. 3 on page 6 ). 1 patient(2.2%) had extrasphincteric fistula & two(4.4%) had no perianal fistula. In 23(51.1%) pts, MRI showed additional findings such as branching tract(22.2%) or inflammatory collection(8.8%) or both(20%) ( Fig. 4 on page 7 ). Of the 45 pts, MRI correctly identified the fistulous tract in 44 pts. In one patient, only one amongst the two fistulas was correctly identified. Of 21 pts having secondary tracts intraoperatively, MRI correctly identified them in 19 pts ( Fig. 5 on page 8 ). All inflammatory collections were correctly identified. Correlation between MRI and surgical findings: Page 3 of 19

4 Surgery positive Surgery negative MRI positive 40 (true positive) 0 (False positive) MRI negative 3 (false negative) 2 (true negative) Sensitivity = TP / TP + FN = 40/43 = 93 % Specificity = TN / TN + FP = 2/2 = 100 % Accuracy = TP + TN / Total = 42/45 = 93.3 % PPV = TP / TP + FP = 40/40 = 100% NPV = TN / TN + FN = 2/5 = 40% Thus the sensitivity was 93%, specificity was 100% & the accuracy was 93.3%. This is comparable to the previously reported sensitivity of 97 % by Sahni VA et al in their evidence based medicine methods study titled "Which method is best for imaging of perianal fistula?"; 91% by Buchanan et al in study titled "Clinical examination, endosonography, and MR imaging in preoperative assessment of fistula in ano: comparison with outcome-based reference standard" and 97% by Beckingham et al in study titled "Prospective evaluation of dynamic contrast enhanced magnetic resonance imaging in the evaluation of fistula in ano". Comparison with other studies: Study Year of study No. of sequences Sample size Sensitivity Ultrashort Protocol Balani et al % Sahni VA et al 2008 Evidence based method study - 97 % Buchanan GN et al % Beckingham IJ et al % Daabis N et al % Page 4 of 19

5 Singh K et al % Images for this section: Fig. 14: Time is money - Ultrashort protocol for MRI fistulogram - Advantages Page 5 of 19

6 Fig. 1: Bar diagram showing the age distribution of patients in this study with most common age group being 31 to 50 years Fig. 2: Pie chart showing gender distribution of patients in this study with 82.2 % patients being male. Page 6 of 19

7 Fig. 3: Pie chart showing types of fistula in patients in this study with intersphincteric fistula being the most common type (55.5 %) followed by transsphincteric type (37.7 %). Page 7 of 19

8 Fig. 4: Bar diagram showing distribution of pathologies in this study wherein 20 patients had simple non branching fistula track while remaining 23 patients had either branching tract or inflammatory collection or both. Page 8 of 19

9 Fig. 5: Hierarchy diagram showing correlation between MRI and surgical findings Page 9 of 19

10 Fig. 6: Table showing comparison of Ultrashort protocol with other studies done previously showing comparable sensitivity of this ultrashort protocol. Page 10 of 19

11 Fig. 8: Axial T2 weighted non fat saturated FSE image showing intersphinteric fistulous track between the internal and external sphincters - Grade I (red arrow). Non fat saturated images have high spatial resolution providing excellent anatomical details and thus help in correct classification of fistulous track. Page 11 of 19

12 Fig. 7: Sagittal T2 CUBE image showing linear non-branching fistulous track in intersphincteric plane - Grade I (yellow arrow). Fat saturated images provide excellent demonstration of fistulous track and its extensions. Page 12 of 19

13 Fig. 9: Axial T2 weighted non fat saturated FSE image showing intersphincteric fistulous track with internal opening at 6 o clock position (long arrow) and an inflammatory collection in intersphincteric plane (short arrows) - Grade II. Page 13 of 19

14 Fig. 10: Axial T2 weighted non fat saturated FSE image showing linear non branching transphincteric fistula (red arrow) (grade III) traversing through the external and internal sphincters with internal opening at 6 o clock position. Page 14 of 19

15 Fig. 11: Sagittal and coronal reformatted images of T2 CUBE showing a transphincteric fistula with an U shaped branching track and internal opening at 6 o clock position - Grade IV. Page 15 of 19

16 Fig. 12: Axial T2 FSE, Sagittal T2 CUBE and Axial reformatted T2 CUBE images demonstrating anterior transsphincteric fistulous track with right testicular abscess and testicular rupture with secondary extensions in the periprostatic region - Grade IV. The small secondary extensions were delineated only on thin reconstructions from 3D CUBE sequence and would have been missed if this sequence was not taken. Page 16 of 19

17 Fig. 13: Sagittal T2 CUBE, Axial T2 FSE and oblique maximum intensity projection images showing high transphincteric fistula with horseshoe shaped infralevator secondary track and a high supralevator secondary track - Grade V. Oblique MIP images depict the entire track in a single image which is easily communicated to surgeons and acts a surgical roadmap. Page 17 of 19

18 Conclusion Benifits of Ultrashort Protocol: Highly accurate in identifying the course and details of fistulous track with sensitivity and specificity comparable to studies done using detailed protocols Significantly reduces scan time improving patient cooperation and increasing patient throughput No contrast administration. Thus is safe in patients with deranged renal functions and in patients with previous allergic response to contrast medium Limitations of Protocol: Difficult to differentiate abscess from inflammatory changes (Granulation tissue) [Absence of post contrast T1 images] Difficult to differentiate hemorrhage from residual tracks in immediate postoperative period [Absence of fat sat T1 images] Periprostatic, periovarian veins may be confused with fistula (veins are thin walled, symmetric and tortuous) Limitations of Study: Difficulty in defining a true reference standard for fistula in ano - in our case we have considered surgical exploration guided by MR imaging as reference Follow-up of patients could minimize potential biases, which is lacking in our study. Sample size - more studies with larger number of patients are needed to evaluate this time-saving & efficient protocol. Personal information References Sahni VA, Ahmad R, Burling D. Which method is best for imaging of perianal fistula? Abdominal imaging. 2008;33(1): Buchanan GN, Halligan S, Bartram CI, Williams AB, Tarroni D, Cohen CR. Clinical examination, endosonography, and MR imaging in preoperative Page 18 of 19

19 assessment of fistula in ano: comparison with outcome-based reference standard. Radiology. 2004;233(3): Beckingham IJ, Spencer JA, Ward J, Dyke GW, Adams C, Ambrose NS. Prospective evaluation of dynamic contrast enhanced magnetic resonance imaging in the evaluation of fistula in ano. The British journal of surgery. 1996;83(10): Daabis N, El Shafey R, Zakaria Y, Elkhadrawy O. Magnetic resonance imaging evaluation of perianal fistula. The Egyptian Journal of Radiology and Nuclear Medicine. 2013;44(4): Singh K, Singh N, Thukral C, Singh KP, Bhalla V. Magnetic resonance imaging (MRI) evaluation of perianal fistulae with surgical correlation. Journal of clinical and diagnostic research : JCDR. 2014;8(6):RC01-4. Page 19 of 19