Manon L. W. Ziech

Imaging of Perianal Fistulas

Perianal fistulas, cryptoglandular or Crohns disease-related, have a tendency to recur. Recurrence usually is owing to missed infection during surgery for cryptoglandular fistulas or insufficient response to medical treatment in Crohns disease. It is now recognized that preoperative imaging (endoanal ultrasound and magnetic resonance imaging) can help to identify extensions that otherwise would be missed during surgery and therefore prevent recurrence. For medical therapy, the extent of the disease and the presence of abscesses are identified with imaging and therapy response can be monitored. The purpose of this review is to give an up-to-date overview of the anal anatomy, classification of perianal fistulas, and the role of imaging modalities in the management of patients with perianal fistulas.

Dynamic contrast-enhanced MRI in patients with luminal Crohn's disease

OBJECTIVES To prospectively assess dynamic contrast-enhanced (DCE-)MRI as compared to conventional sequences in patients with luminal Crohns disease. METHODS Patients with Crohns disease undergoing MRI and ileocolonoscopy within 1 month had DCE-MRI (3T) during intravenous contrast injection of gadobutrol, single shot fast spin echo sequence and 3D T1-weighted spoiled gradient echo sequence, a dynamic coronal 3D T1-weighted fast spoiled gradient were performed before and after gadobutrol. Maximum enhancement (ME) and initial slope of increase (ISI) were calculated for four colon segments (ascending colon+coecum, transverse colon, descending colon+sigmoid, rectum) and (neo)terminal ileum. C-reactive protein (CRP), Crohns disease activity index (CDAI), per patient and per segment Crohns disease endoscopic index of severity (CDEIS) and disease duration were determined. Mean values of the (DCE-)MRI parameters in each segment from each patient were compared between four disease activity groups (normal mucosa, non-ulcerative lesions, mild ulcerative and severe ulcerative disease) with Mann-Whitney test with Bonferroni adjustment. Spearman correlation coefficients were calculated for continuous variables. RESULTS Thirty-three patients were included (mean age 37 years; 23 females, median CDEIS 4.4). ME and ISI correlated weakly with segmental CDEIS (r=0.485 and r=0.206) and ME per patient correlated moderately with CDEIS (r=0.551). ME was significantly higher in segments with mild (0.378) or severe (0.388) ulcerative disease compared to normal mucosa (0.304) (p<0.001). No ulcerations were identified at conventional sequences. ME correlated with disease duration in diseased segments (r=0.492), not with CDAI and CRP. CONCLUSIONS DCE-MRI can be used as a method for detecting Crohns disease ulcerative lesions.

Retrospective comparison of magnetic resonance imaging features and histopathology in Crohn's disease patients

PURPOSE To retrospectively compare histopathological findings of surgically resected bowel segments with magnetic resonance imaging (MRI) findings on Crohns disease activity. MATERIALS AND METHODS Patients who underwent a MR enterography or enteroclysis before surgery were included after informed consent. MRI features (T1-enhancement, T1 and T2 stratification, T2 signal intensity, bowel wall thickness, presence of ulcerations, comb sign, creeping fat, and disease activity) were assessed by three experienced abdominal radiologists. An acute inflammatory score based on histopathology (parameters: mucosal ulceration, edema, depth and degree of neutrophils) was calculated. Interobserver variability for subjective MRI features was also assessed. RESULTS Thirty-nine segments in 25 patients (mean age 38 years) were included. Of the MRI features, disease activity per segment and bowel wall thickness had a positive association with the acute inflammatory score (p<0.05). T1-enhancement had a positive correlation with disease chronicity. All other MRI features did not have an association with the acute inflammatory score. Interobserver agreement between the three observers was weak to moderate. CONCLUSION MR features bowel wall thickness and disease activity per-segment reflect disease activity in Crohns disease patients.

Grading luminal Crohn's disease: Which MRI features are considered as important?

OBJECTIVES Magnetic resonance imaging (MRI) is increasingly used for disease activity grading in small bowel Crohns disease. It is not known which imaging features are essential for grading. For further insight, we solicited the opinion of expert radiologists. METHODS A questionnaire about the grading of Crohns disease was sent to 36 radiologists who had published on MRI grading of Crohns disease between January 2006 and January 2010. Radiologists were asked which MRI protocol they used, how they graded luminal Crohns disease, which features they used, how important they considered those features for grading, and which reference standards they used. RESULTS Twenty-four radiologists responded (66%). They used different protocols and features; most frequently T2-weighted sequences (79%) and contrast enhanced fat saturated T1-weighted sequences (83%). MR-enterography was more often used than MR-enteroclysis (88% versus 33%). Features most frequently considered important for grading were bowel wall thickness (79% of radiologists), the presence of an abscess (75%), T1 enhancement (75%), and T1 stratification (46%). Reference standards differed; most commonly (ileo-) colonoscopy (88%) or surgery (75%) were used. CONCLUSIONS Bowel wall thickness, abscess, T1 enhancement and T1 stratification are most often used for grading. Because of difference in grading, there is need for an international consensus on MRI grading of Crohns disease.

Evaluation of an MRI-based score of disease activity in perianal fistulizing Crohn's disease

To evaluate a magnetic resonance imaging (MRI)-based score of disease severity for perianal fistulizing Crohns disease (CD), 16 patients with perianal fistulizing CD underwent 1.5-T MRI before and after infliximab therapy. MRI scores, Perianal Disease Activity Index (PDAI) and C-reactive protein (CRP) were calculated, and fistula drainage was assessed. These items were compared for responders and nonresponders. After therapy, PDAI values and CRP values decreased significantly in responders, but there were no significant differences in the MRI scores. In all responders, MRI findings were indicative of persisting active inflammation. In these patients, a relapse rate of 57% was seen.

Dynamic Contrast-Enhanced MRI in Determining Disease Activity in Perianal Fistulizing Crohn Disease: A Pilot Study

OBJECTIVE The objective of our study was to perform a semiquantitative analysis of dynamic contrast-enhanced MRI for the evaluation of disease activity and therapeutic response in patients with perianal fistulizing Crohn disease. SUBJECTS AND METHODS Sixteen consecutively registered patients with perianal Crohn disease underwent pelvic MRI. A dynamic contrast-enhanced sequence was performed at 3 T (temporal resolution, 4.2 seconds) during i.v. contrast injection. Maximum enhancement, initial slope of increase, volume transfer constant (K(trans)), and the extravascular space fractional volume (x028B;(e)) were calculated in a region of interest drawn around the fistula. Perianal disease activity index, C-reactive protein concentration, and an MRI-based activity score were calculated as reference standards. Six patients underwent a second MRI examination 6 weeks after starting treatment with anti-tumor necrosis factor α (anti-TNF-α). RESULTS Perianal disease activity index moderately correlated with maximum enhancement (r = 0.67, p = 0.005), initial slope of increase (r = 0.58, p = 0.018), and volume of enhancing pixels (r = 0.79, p < 0.001) but not with K(trans) or x028B;(e). Volume of enhancing pixels also correlated with C-reactive protein concentration and the MRI-based score (r = 0.52, p = 0.041; r = 0.79, p < 0.001). The K(trans) values had decreased significantly 6 weeks after the start of anti-TNF-α therapy. CONCLUSION Maximum enhancement and initial slope of increase correlate with disease activity in perianal Crohn disease. K(trans) may be an indicator of the effect of therapy on patients starting anti-TNF-α treatment.

Expiration-Phase Template-Based Motion Correction of Free-Breathing Abdominal Dynamic Contrast Enhanced MRI

This paper studies a novel method to compensate for respiratory and peristaltic motions in abdominal dynamic contrast enhanced magnetic resonance imaging. The method consists of two steps: 1) expiration-phase “template” construction and retrospective gating of the data to the template; and 2) nonrigid registration of the gated volumes. Landmarks annotated by three experts were used to directly assess the registration performance. A tri-exponential function fit to time intensity curves from regions of interest was used to indirectly assess the performance. One of the parameters of the tri-exponential fit was used to quantify the contrast enhancement. Our method achieved a mean target registration error (MTRE) of 2.12, 2.27, and 2.33 mm with respect to annotations by expert, which was close to the average interobserver variability (2.07 mm). A state-of-the-art registration method achieved an MTRE of 2.83-3.10 mm. The correlation coefficient of the contrast enhancement parameter to the Crohns disease endoscopic index of Severity (r = 0.60, p = 0.004) was higher than the correlation coefficient for the relative contrast enhancement measurements values of two observers (r(Observer1) = 0.29, p = 0.2; r(Observer2) = 0.45, p = 0.04). Direct and indirect assessments show that the expiration-based gating and a nonrigid registration approach effectively corrects for respiratory motion and peristalsis. The method facilitates improved enhancement measurement in the bowel wall in patients with Crohns disease.

MRI of the Small Bowel: Enterography

MR enterography has become an important technique for imaging of the small bowel. Technical advances, especially fast imaging techniques, were a major impetus for this development. Luminal distension is obtained by oral intake of a contrast agent; often a biphasic contrast agent is used. This has been shown to be sufficient to demonstrate pathologic findings. The major indication for MR enterography is follow-up of disease activity in Crohns disease. It can also be used as an alternative for endoscopy and MR enteroclysis for the work-up of patients with symptoms most likely related to small bowel diseases and for specific conditions such as lymphoma and small bowel polyps. Patient acceptance of MR enterography is high when compared to MR enteroclysis and colonoscopy, which is important for frequent application of the technique for monitoring treatment. Thereby, the technique has logistical advantages over MR enteroclysis.

3D non-rigid motion correction of free-breathing abdominal DCE-MRI data

Inflammatory bowel diseases (IBD) constitute one of the largest healthcare problems in the Western World. Grading of the disease severity is important to determine treatment strategy and to quantify the response to treatment. The Time Injection Curves (TICs) after injecting a contrast agent contain important information on the degree of inflammation of the bowel wall. However, respiratory and peristaltic motions complicate an easy analysis of such curves since spatial correspondence over time is lost. We propose a gated, 3D non-rigid motion correction method that robustly extracts time intensity curves from bowel segments in free-breathing abdominal DCE-MRI data. It is shown that the mean TICs in small bowel segments could be robustly computed and contained less fluctuations than prior to the registration.