Comparison of T2-weighted imaging, diffusion-weighted imaging and contrast-enhanced T1-weighted MR imaging for evaluating perianal fistulas.Clin Imaging. 2017;44:16-21. [PMID: 28395191 DOI: 10.1016/j.clinimag.2017.03.019]

Imaging of Ulcerative Colitis: The Role of Diffusion-Weighted Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has emerged as a promising and appealing alternative to endoscopy in the objective assessment of patients with inflammatory bowel disease (IBD). Diffusion-weighted imaging (DWI) is a specialized imaging technique that enables the mapping of water molecule diffusion within biological tissues, eliminating the need for intravenous gadolinium contrast injection. It is expanding the capability of traditional MRI sequences in Ulcerative Colitis (UC). Recently, there has been growing interest in the application of intravoxel incoherent motion (IVIM) imaging in the field of IBD. This technique combines diffusion and perfusion information, making it a valuable tool for assessing IBD treatment response. Previous studies have extensively studied the use of DWI techniques for evaluating the severity of activity in IBD. However, the majority of these studies have primarily focused on Crohn's disease (CD), with only a limited number of reports specifically examining UC. Therefore, this review briefly introduces the basics of DWI and IVIM imaging and conducts a review of relevant studies that have investigated its application in UC to show whether these techniques are useful techniques for evaluating patients with UC in terms of detection, characterization, and quantification of disease activity. Through the extensive literature survey, most of these studies indicate that DWI proves valuable in the differential diagnosis of UC and could be used as an effective modality for staging UC.

An applicability study of rapid artificial intelligence-assisted compressed sensing (ACS) in anal fistula magnetic resonance imaging

Objective

To evaluate the applicability of artificial intelligence-assisted compressed sensing (ACS) to anal fistula magnetic resonance imaging (MRI).

Methods

51 patients were included in this study and underwent T2-weighted sequence of MRI examinations both with ACS and without ACS technology in a 3.0 T MR scanner. Subjective image quality scores, and objective image quality-related metrics including scanning time, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR), were evaluated and statistically compared between the images collected with and without ACS.

Results

No significant difference in the subjective image quality of lesion conspicuity was observed between the two groups. However, ACS MRI decreased the acquisition time with regard to control group (74.00 s vs. 156.00 s). Besides, SNR of perianal and muscle in the ACS group was significantly higher than that of the control group (164.07 ± 33.35 vs 130.81 ± 29.10, p < 0.001; 109.87 ± 22.01 vs 87.61 ± 17.95, p < 0.001; respectively). The CNR was significantly higher in the ACS group than in the control group (54.02 ± 23.98 vs 43.20 ± 21.00; p < 0.001). Moreover, the accuracy rate of the ACS groups in evaluating the direction and internal opening of the fistula was 88.89 %, exactly the same as that of the control group.

Conclusion

We demonstrated the applicability of using ACS to accelerate MR of anal fistulas with improved SNR and CNR. Meanwhile, the accuracy rates of the ACS group and the control were equivalent in evaluating the direction and internal opening of the fistula, based on the results of surgical exploration.

Comparison of Contrast-Enhanced 3D Imaging with 2D Imaging in the Evaluation of Perianal Fistula at 3T: A Prospective Observational Study

Introduction  Perianal fistula and its recurrence is a challenging entity for surgeons. It is a well-establi1shed fact that magnetic resonance imaging (MRI) findings influence surgical procedures and reduce the rate of recurrence. In this study, we assessed the contrast-enhanced (CE) three dimensional T1 sequences [sampling perfection with application optimized contrast using different flip angle evolution (SPACE) and volumetric interpolated breath-hold examination (VIBE)] in a 3T MRI system to evaluate perianal fistulas and compared them with two-dimensional (2D) sequences. Materials and Methods  Forty-four patients (mean age, 38.8 ± 15.3 [standard deviation]; 32 males, 12 females) with perianal fistula were included in this prospective study. The patients underwent conventional noncontrast, 2D sequences, diffusion-weighted imaging, followed by postcontrast, 2D T1 images in both axial and coronal planes, and 3D sequences at 3T. Acquisition times were recorded for each sequence. Each postcontrast sequence was evaluated in terms of image quality, presence of artifacts, fistula type, presence of an abscess, visibility, and number of internal orifices. The surgical findings were considered the gold standard. The imaging findings were compared with the surgical findings. Results  In all three sequences, the fistula type and abscess were identified correctly in all patients. The sensitivity value for identification of ramifications utilizing CE 3D T1 VIBE sequence, CE 3D T1 SPACE, and CE 2D T1 images was 100, 86, and 36%, respectively. The number of internal orifices was identified by the CE 3D T1 VIBE and CE 3D T1 SPACE sequences in 100 and 92% of patients, respectively. CE 2D T1 images correctly identified internal orifices in 80% of patients. The overall scan time for each 3D sequence was shorter than for the combined postcontrast 2D sequences. Conclusion  CE 3D T1 SPACE and CE 3D T1 VIBE sequences outperformed conventional CE 2D sequences in the evaluation of perianal fistulas in terms of visibility and the number of internal orifices with a shorter scanning time. Among the 3D sequences, CE 3D T1 VIBE is slightly superior to CE 3D T1 SPACE sequence.

Role of transperineal ultrasound in evaluation of patients with perianal inflammatory disorders

Background

The aim of this study was to study the degree of accuracy of transperineal ultrasound (TPUS) in pre-operative evaluation and follow-up of cases with perianal inflammatory disorders in relation to MRI findings. Thirty patients with symptoms and signs of perianal inflammatory disorders underwent TPUS and pelvic MRI examinations. The radiologist who performed the TPUS was blinded to MR findings and was asked to comment on the site of the internal opening and extension of the tract, any related side branches or collections.

Results

The overall accuracy of TPUS in detection of the site of internal opening of perianal tracts was 83.33%, with sensitivity of 91.30%. TPUS showed sensitivity, specificity and accuracy of 100% in detection of horseshoe collections. The overall accuracy of TPUS in detection of perianal abscesses was 93.33% with specificity of 100%. TPUS showed sensitivity of 50.00%, specificity of 92.31% and accuracy of 86.67% in visualization of side branches. TPUS showed sensitivity of 33.33%, specificity of 88.89% and overall accuracy of 83.33% in detection of supralevator extension of perianal tracts. TPUS correctly classified (23/30) perianal tracts with accuracy of 76.7%.

Conclusions

TPUS can be used as a first diagnostic tool in patients with perianal inflammatory disorders and related pathologies, particularly horseshoe collections which can change the operative decision made by the surgeon. TPUS can be used in repeated follow-up during the course of management of perianal inflammatory disorders or when other imaging modalities are unavailable or contra-indicated.

Role of MRI special diffusion weighted imaging/diffusion tensor imaging techniques in the assessment of perianal fistula activity

Background

Pre-operative MRI examination is currently considered as an evolving tool for assessment of perianal fistula types, extensions, and complications to achieve proper treatment plan. Proper assessment of fistula activity can also have a major contributing role to the treatment plan, through deciding the type of prescribed medications, proper surgical approach as well as the proper operative intervention timing. Reviewing literature, only few studies have mentioned the importance of diffusion tensor imaging (DTI) sequences in diagnosing perianal fistula activity, yet many studies have discussed the perianal fistula activity assessment using other diffusion weighted imaging (DWI) sequences. In the present study, the main objective was to prove the MRI quantitative DTI sequences’ ability of diagnosing perianal fistulae inflammatory activity.

Results

This study was a prospective analysis in which fistular activity was confirmed by intra-operative findings (considered as the standard reference). The cases included in the study were divided into two groups, based on their surgical findings, positive inflammatory and negative inflammatory groups. Both groups were pre-operatively assessed using MRI imaging and additionally used diffusion weighted and tensor imaging (DWI and DTI) sequences by special post-processing quantitative assessment of DTI FA and ADC values. There was significant statistical difference between the mean ADC value of the PIA and NIA groups in the track, edema, ipsilateral and contralateral sphincter areas with P values (P = 0.000, 0.000, 0.002 and 0.000 respectively). There was also significant difference between the mean FA value of the PIA and NIA groups in the track, edema, ipsilateral and contralateral sphincter areas with P values (P = 0.000, 0.000, 0.000 and 0.008 respectively).

Conclusion

This study results revealed that FA are relatively lower in positive inflammatory activity lesions than in negative inflammatory activity lesions while the ADC values were relatively higher in positive inflammatory activity lesions than in negative inflammatory activity lesions and the differences were statistically significant having a fundamental role in the assessment of perianal fistula activity especially at the track area being of highest sensitivity and specificity. Unlike conventional MRI sequences which revealed only high specificity being a good negative modality.

Comparison of contrast-enhanced fat-suppressed T1-3D-VIBE and T1-TSE MRI in evaluating anal fistula

OBJECTIVE

To evaluate the accuracy of contrast-enhanced (CE) fat-suppressed three-dimensional (3D) T1-weighted imaging with volumetric interpolated breath-hold examination (FS-T1-3D-VIBE) and fat-suppressed T1-weighted turbo spin echo (FS-T1-TSE) sequence in characteristics of anal fistula.

METHODS

One hundred and two patients underwent perianal CE-MRI examination on a 3T scanner including FS-T1-3D-VIBE and FS-T1-TSE sequences before surgery. The performance of each sequence was evaluated in terms of fistula classification, clarity of internal opening, number and position of internal openings including the distance between internal opening and anal verge, presence of secondary tracts and blind-ending sinus tracts. MRI findings were compared with surgical findings. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of fistula, gluteus maximus, and subcutaneous fat were compared between CE FS-T1-TSE and CE FS-T1-3D-VIBE.

RESULTS

Compared with CE FS-T1-TSE, CE FS-T1-3D-VIBE displayed more accurate in secondary tract, lithotomy position of the internal opening and the distance between internal opening and anal verge (P < 0.05). CE FS-T1-3D-VIBE was found superior to CE FS-T1-TSE in the clarity of the internal openings and in the diagnostic accuracy of blind-ending sinus tracts and complex fistulas in Standard Practice Task Force classification (P < 0.05). CE FS-T1-3D-VIBE achieved higher SNRs and CNRs in fistula and gluteus maximus than CE FS-T1-TSE (P ≤ 0.001).

CONCLUSION

CE-MRI of FS-T1-3D-VIBE might be a more valuable noninvasive technique than FS-T1-TSE to evaluate the anal fistula on evaluating the lithotomy position of internal opening, distance between internal opening and anal verge, clarity of internal opening, secondary tract, blind-ending sinus tract and classification of the complex fistula. The trial registration number for this prospective trial was Chi-TR1800020206 and the trial registration date was December 20, 2018.

Quantitative Magnetic Resonance Imaging in Perianal Crohn's Disease at 1.5 and 3.0 T: A Feasibility Study

Perianal Crohn's Disease (pCD) is a common manifestation of Crohn's Disease. Absence of reliable disease measures makes disease monitoring unreliable. Qualitative MRI has been increasingly used for diagnosing and monitoring pCD and has shown potential for assessing response to treatment. Quantitative MRI sequences, such as diffusion-weighted imaging (DWI), dynamic contrast enhancement (DCE) and magnetisation transfer (MT), along with T2 relaxometry, offer opportunities to improve diagnostic capability. Quantitative MRI sequences (DWI, DCE, MT and T2) were used in a cohort of 25 pCD patients before and 12 weeks after biological therapy at two different field strengths (1.5 and 3 T). Disease activity was measured with the Perianal Crohn's Disease Activity index (PDAI) and serum C-reactive protein (CRP). Diseased tissue areas on MRI were defined by a radiologist. A baseline model to predict outcome at 12 weeks was developed. No differences were seen in the quantitative MR measured in the diseased tissue regions from baseline to 12 weeks; however, PDAI and CRP decreased. Baseline PDAI, CRP, T2 relaxometry and surgical history were found to have a moderate ability to predict response after 12 weeks of biological treatment. Validation in larger cohorts with MRI and clinical measures are needed in order to further develop the model.

Guidelines on postoperative magnetic resonance imaging in patients operated for cryptoglandular anal fistula: Experience from 2404 scans

Magnetic resonance imaging (MRI) is considered the gold standard for the evaluation of anal fistulas. There is sufficient literature available outlining the interpretation of fistula MRI before performing surgery. However, the interpretation of MRI becomes quite challenging in the postoperative period after the surgery of fistula has been undertaken. Incidentally, there are scarce data and no set guidelines regarding analysis of fistula MRI in the postoperative period. In this article, we discuss the challenges faced while interpreting the postoperative MRI, the timing of the postoperative MRI, the utility of MRI in the postoperative period for the management of anal fistulas, the importance of the active involvement and experience of the treating clinician in interpreting MRI scans, and the latest advancements in the field.

Evaluating postoperative anal fistula prognosis by diffusion-weighted MRI

PURPOSE

The purpose of this study was to explore whether preoperative diffusion-weighted magnetic resonance imaging (DW-MRI) can be used to evaluate the prognosis of anal fistula and identify the influence factors of postoperative recurrence.

METHODS

This is a retrospective study of 117 patients with anal fistula who have undergone preoperative DW-MRI and surgery. All patients were followed up by telephone or reexamination within 2 years after surgery. Of the 117 patients, 35 were excluded due to loss of follow-up and only 82 were included in this study. MRI fistula imaging-related data were analyzed, and fistula severity was scored using criteria of both local extension of fistulas and active inflammation for a total maximum score of 22. The apparent diffusion coefficient (ADC) value of the fistula in patients with anal fistula during preoperative MRI examination was measured. According to whether anal fistula patients are accompanied by perianal abscess, they are divided into two groups, namely anal fistula group and anal fistula with abscess group. Based on whether patients with anal fistula recur after surgery, they were further divided into recurrent group and non-recurrent group.

RESULTS

82 patients with anal fistula were included in this analysis, 23 of them recurred and 59 were cured. Among patients with perianal abscess, the mean ADC value of the recurrent group was (1.19 ± 0.21)×10^-3 mm²/s, which is significantly lower than that of the non-recurrent group (1.36 ± 0.19)×10^-3 mm²/s. There were significant statistical differences in ADC values between the two groups (p = 0.03). Among patients with anal fistulas without abscesses, 15 patients recurred after surgery, with a mean ADC value of (1.45 ± 0.27) ×10^-3 mm²/s, and 33 patients didn't occur, with a mean ADC value of (1.44 ± 0.31)×10^-3 mm²/s. The ADC value of preoperative fistula in patients was negative significant correlation with MRI findings score (r= -0.332, P = 0.002). Risk factors for the recurrence after anal fistula surgery include the time interval between MRI and operation, multiple fistula tracks. Fatigue, excessive intake of spicy or greasy food and diarrhea may also be external risk factors for postoperative recurrence of patients with anal fistula.

CONCLUSIONS

DW-MRI has important application value for the prognosis evaluation of anal fistula. Complex type of anal fistula and improper lifestyle are the main risk factors affecting the recurrence after anal fistula surgery.

Use of Cross-Sectional Imaging for Tight Monitoring of Inflammatory Bowel Diseases

A treat-to-target strategy with close monitoring of intestinal inflammation is recommended in inflammatory bowel disease (IBD). Ileocolonoscopy remains the gold standard for assessing disease activity in IBD but is a relatively invasive procedure and is impossible to repeat in the context of tight monitoring strategies. In addition to biomarkers, cross-sectional imaging increasingly is used in these patients. Computed tomography is limited by the use of radiation, while the use of magnetic resonance enterography (MRE) is limited by its cost and access. There is growing interest in bowel ultrasound that represents a cost-effective, noninvasive, and well-tolerated modality in clinical practice, but it is operator dependent. Compared with ileocolonoscopy and MRE, bowel US has been shown to have the same level of accuracy in assessing and monitoring disease activity for both CD and UC and thus can be considered a point-of-care test. Diffusion-weighted imaging (DWI) is a MR imaging technique that increasingly is used in both IBD and non-IBD conditions and has been shown to be a valuable and accurate tool for assessing and monitoring IBD activity. Compared with conventional MRE, DWI is quicker, less time consuming, may not require intravenous contrast agent, fasting, bowel cleansing, oral preparation, or rectal preparation. This review discusses the role of these cross-sectional imaging techniques for the management of patients with IBD. In the near future, the value of DWI and ultrasound in assessing IBD will require further investigation in the era of transmural healing in CD and complete mucosal healing, including histologic remission, in ulcerative colitis.

Perianal fistula mapping at 3 T: volumetric versus conventional MRI sequences

AIM

To evaluate volumetric contrast-enhanced three-dimensional T1-weighted (CE 3D T1) turbo spin-echo (TSE) with variable flip angle (SPACE), CE 3D T1 volumetric interpolated breath-hold examination (VIBE) sequences with conventional CE-two-dimensional (2D)-T1 and 2D-T2-weighted imaging (WI) sequences in assessing perianal fistulas.

METHODS AND MATERIALS

Twenty-three patients with perianal fistula were included in this prospective study and underwent pelvic magnetic resonance imaging (MRI) at 3 T including fat-supressed CE 3D T1 SPACE, CE 3D T1 VIBE, axial and coronal 2D-T1WI together with 2D-T2WI sequences in the axial and coronal planes. Acquisition times were recorded. Performance of each sequence was evaluated in terms of image quality, presence of artefacts, lesion conspicuity, fistula type, presence of abscess, visibility of internal orifice, and number of internal orifices. Results were compared with post-surgical findings defined as the reference standard.

RESULTS

Both CE 3D T1 VIBE and CE 3D T1 SPACE were the best sequences to determine fistula type and in terms of image quality, artefacts, and determining locations of internal orifices. The number of internal orifices was detected correctly in 23 (100%) patients for CE 3D T1 SPACE and CE 3D T1 VIBE sequences, in 17 (73.9%) patients on CE-T1WI, and in seven (30.4%) patients on 2D-T2WI. Lesion conspicuity was higher for CE 3D T1 SPACE and CE 3D T1 VIBE sequences compared to the 2D sequences (p<0.05). The overall acquisition time for each 3D sequence was shorter compared to the 2D sequences combined.

CONCLUSION

CE 3D T1 SPACE and CE 3D T1 VIBE sequences may outperform conventional 2D sequences in the evaluation of perianal fistulas in terms of visibility and number of internal orifices with a shorter scanning time.

Perianal fistula imaging: a comparison between two-channel superficial Flex coil and eight-channel body coil

Purpose

Perianal fistula is an important health problem with devastating morbidity. For diagnosis and prevention of recurrence, perianal fistula imaging (PFI) is crucial. The aim of this study was to investigate if a Flex-M superficial coil images would provide more information than images obtained with a phased-array body coil in PFI.

Material and methods

Thirty-one fistulas of 29 patients were prospectively evaluated with magnetic resonance imaging. A phased-array body coil was used in all patients as in routine practice, and sequences with Flex-M coil were also obtained. Afterwards, images were evaluated by two experienced radiologists who were blinded to the patients, coil and also to each other. The site of internal and external openings, and presence or absence of abscess and secondary tracts were recorded.

Results

The conspicuity of images was better with the Flex-M coil. Both radiologists saw more internal openings with the Flex-M coil. Cohen’s κ value was 0.100 (p = 0.201) for Reader 1 and 0.110 (p = 0.361) for Reader 2 between these two coils. Additionally, numerically more internal/external openings and secondary tracts were seen by both readers. Interobserver variability was not statistically significant, and Cohen’s κ values signifyied good concordance between readers.

Conclusions

In our study we showed that multichannel superficial phased-array coils improved imaging quality in PFI. We think that Flex-M coil can easily be used in routine clinical practice to gather better images of perianal fistulas.

Preoperative MRI of perianal fistula evaluation and its impact on surgical outcome

Background

Perianal fistula (PAF) is an abnormal tract communicating an external cutaneous opening in the perianal region to the anal canal. PAF is one of the common anorectal disorders in surgical practice with high prevalence. The current study aimed to determine the ability of preoperative MRI for preoperative evaluation of perianal fistula.

Results

This is a retrospective evaluation of 65 patients with perianal fistula. MRI fistula imaging-related data were revised, and fistula severity was scored using criteria of both local extension of fistulas and active inflammation for a total maximum score of 22. Preoperative MRI could predict the severity of perianal disease with sensitivity, specificity, and accuracy rates of 75%, 92%, and 84.6%, respectively. Surgical findings concerning PAF severity correlated significantly with MRI findings. Diffusion-weighted magnetic resonance imaging (DW-MRI) provided high sensitivity and accuracy with 100% specificity for fistula visualization and highest sensitivity, specificity, and accuracy for detection of cavities > 3 mm in diameter. DW-MRI provided the highest specificity rate on ROC curve analysis among the three MRI pulse sequences (DW-MRI, short tau inversion recovery (STIR), and T1 post-contrast).

Conclusion

MRI is valuable and accurate for preoperative investigation for PAF evaluation and abscess localization. MRI allowed accurate detection of internal fistula opening and its relation to sphincters. DW-MRI is a valuable sequence with highest diagnostic yield, and its addition to STIR WI improves sensitivity and specificity for determination of fistula activity and extension.

The role of magnetic resonance imaging in the preoperative evaluation of anal fistulas

This study aimed to determine the role of magnetic resonance imaging (MRI) in diagnosing and describing the characteristics of fistula-in-ano, and the agreement between MRI and operative findings. We conducted a retrospective study in 367 patients with fistula-in-ano who were diagnosed and had an operation at the University Medical Center between January 2016 and January 2018. MRI findings were evaluated and compared with surgical findings using the kappa coefficient (k) method. 367 patients (327 male and 40 female, mean age 39.3 ± 12.4 years). A total of 411 primary fistulas were found during surgery. There was a strong agreement between MRI and surgery for classifying primary tracts (k = 0.89) and detecting secondary tracts (k = 0.94). While the sensitivity and specificity of MRI for detecting internal openings were 99% and 85.2% respectively; these rates were 100% for abscesses. Both T2-weighted turbo spin-echo (T2W TSE) and postcontrast fat-saturated T1-weighted turbo spin-echo (FS T1W TSE) sequences showed high sensitivity (96.6% and 98.4% respectively) and specificity (92.6% and 81.5% respectively) for depicting internal openings and secondary tracts. Post-contrast FS T1W TSE sequence was very effective in detecting abscesses with an accuracy of 100%. In conclusion, MRI can be considered an accurate tool for the preoperative evaluation of fistula-in-ano, which is a major determinant of the surgical outcome. Both T2W TSE and post-contrast FS T1W TSE sequences are highly accurate in depicting the features of fistula-in-ano. If there are no contraindications, contrast administration is recommended to differentiate abscesses from active inflammation.

A comparable method to Gd-contrast enhancement in the preoperative evaluation of anal fistula

To explore a comparable method to Gd-contrast enhancement in the preoperative evaluation of anal fistula to evaluate its morphology changes.Forty-six patients with anal fistula were enrolled. Each patient acquired a 3.0T magnetic resonance imaging (MRI) routine sequence, diffusion-weighted imaging (DWI) sequence and fat suppression T1 weighted imaging (FS T1WI) contrast enhancement (CE) scanning. To record the morphology performances of the internal orifice and the fistulas on the transverse images of fat suppression T2 weighted imaging (FS T2WI), DWI, FS T2WI combined with DWI, FS T1WI Gd-CE, with the standard of the surgical pathology results. Two observers evaluated images in consensus. The conspicuity and the diagnostic performance rate were compared between the 4 imaging data sets.The consistencies of interobservers about the conspicuity scores and the diagnostic performance rates of the internal orifice and the fistula were good. The conspicuity of the internal orifice was higher for the set of FS T2WI, FS T2WI+DWI, and FS T1WI+CE than DWI. The diagnostic performance rate of the internal orifice was higher for the set of FS T2WI, FS T2WI+DWI, and FS T1WI+CE than DWI. The conspicuity of the fistula was higher for the set of FS T2WI+DWI and FS T1WI+CE than FS T2WI or DWI. There were no significantly differences between the 4 sets of FS T2WI, DWI, FS T2WI+DWI, and FS T1WI+CE in the diagnostic performance rate of the fistula.The set of FS T2WI combined with DWI was comparable to FS T1WI CE in evaluation of anal fistula morphology changes.

Contrast- vs. non-contrast enhanced MR data sets for characterization of perianal fistulas

PURPOSE

To evaluate the diagnostic efficacy between pre- and post-contrast MRI sequences in perianal fistulas using intra-operative findings as the gold standard.

MATERIALS AND METHODS

Retrospective analysis of 50 patients with a history of perianal fistula and MRI performed between January 2006 and January 2018 was performed. The inclusion criteria were patients who underwent MRI prior to surgery and had a detailed surgical report available. Pre- and post-contrast MR data sets were evaluated by two radiologists at two-week-intervals, assessed fistula type, internal/external opening, presence of abscess/secondary tracts, and confidence scores. The area under the curve (AUC) was used for comparison the diagnostic ability. The sensitivity and specificity were compared using the McNemar's test.

RESULTS

The confidence scores in detecting perianal fistulas were significantly higher in the post-contrast MR data set (p < 0.003). The post-contrast MR data set had similar ability to classify perianal fistulas as combined T2-DWI and isolated T2 data sets in 49/50 cases. For internal/external opening, the post-contrast MR, combined T2-DWI, and isolated T2 data sets had 100% concordance with intra-operative reports. For perianal abscess, there was no significant difference in sensitivity or AUC value between the isolated T2 or combined T2-DWI data sets and post-contrast MR data set (p > 0.05). All MR data sets correctly identified secondary tracts in all 50 cases.

CONCLUSIONS

Although contrast-enhanced MR studies can improve a radiologist's confidence, non-contrast MR studies had similar diagnostic efficacy in identifying perianal fistulas and their complications. Therefore, a non-contrast study may suffice in selected patients such as those with renal impairment.

New cross-sectional imaging in IBD

PURPOSE OF REVIEW

Cross-sectional imaging, namely ultrasound, CT and MR enterography, complements clinical and endoscopic monitoring of activity and complications in IBD, and emerging new radiological technologies may have clinical applications in the near future. This review offers an update on the potential role of these new imaging methods in the management of IBD.

RECENT FINDINGS

Specific MR techniques [diffusion-weighted imaging (DWI), diffusion kurtosis imaging (DKI) and magnetization transfer] allow accurate detection of inflammation (DWI and maybe DKI) and fibrosis (magnetization transfer) in Crohn's disease, without the need of intravenous gadolinium administration. ultrasonography developments (elastography, contrast-enhanced ultrasonography, small intestine contrast ultrasonography and multispectral optoacoustic tomography) are promising techniques for evaluation of fibrosis (elastography) and inflammation (contrast ultrasonography). Dose-reduction techniques in CT allow similar quality imaging and diagnostic accuracy with lower radiation exposure. Hybrid imaging (PET/MR and PET/CT) hold promise for grading inflammation in Crohn's disease.

SUMMARY

The potential benefits of new cross-sectional imaging techniques in IBD include better inflammation grading, such as identification of mild degree of activity, which may be relevant whenever assessing response to treatment and, of uttermost importance, accurate preoperative detection and grading of fibrosis in stricturing Crohn's disease, facilitating surgical vs. medical therapeutic decisions.