A supervised learning approach for Crohn's disease detection using higher-order image statistics and a novel shape asymmetry measure

Increasing incidence of Crohn's disease (CD) in the Western world has made its accurate diagnosis an important medical challenge. The current reference standard for diagnosis, colonoscopy, is time-consuming and invasive while magnetic resonance imaging (MRI) has emerged as the preferred noninvasive procedure over colonoscopy. Current MRI approaches assess rate of contrast enhancement and bowel wall thickness, and rely on extensive manual segmentation for accurate analysis. We propose a supervised learning method for the identification and localization of regions in abdominal magnetic resonance images that have been affected by CD. Low-level features like intensity and texture are used with shape asymmetry information to distinguish between diseased and normal regions. Particular emphasis is laid on a novel entropy-based shape asymmetry method and higher-order statistics like skewness and kurtosis. Multi-scale feature extraction renders the method robust. Experiments on real patient data show that our features achieve a high level of accuracy and perform better than two competing method

Training readers to improve their accuracy in grading Crohn's disease activity on MRI

To prospectively evaluate if training with direct feedback improves grading accuracy of inexperienced readers for Crohn's disease activity on magnetic resonance imaging (MRI). Thirty-one inexperienced readers assessed 25 cases as a baseline set. Subsequently, all readers received training and assessed 100 cases with direct feedback per case, randomly assigned to four sets of 25 cases. The cases in set 4 were identical to the baseline set. Grading accuracy, understaging, overstaging, mean reading times and confidence scores (scale 0-10) were compared between baseline and set 4, and between the four consecutive sets with feedback. Proportions of grading accuracy, understaging and overstaging per set were compared using logistic regression analyses. Mean reading times and confidence scores were compared by t-tests. Grading accuracy increased from 66 % (95 % CI, 56-74 %) at baseline to 75 % (95 % CI, 66-81 %) in set 4 (P = 0.003). Understaging decreased from 15 % (95 % CI, 9-23 %) to 7 % (95 % CI, 3-14 %) (P < 0.001). Overstaging did not change significantly (20 % vs 19 %). Mean reading time decreased from 6 min 37 s to 4 min 35 s (P < 0.001). Mean confidence increased from 6.90 to 7.65 (P < 0.001). During training, overall grading accuracy, understaging, mean reading times and confidence scores improved gradually. Inexperienced readers need training with at least 100 cases to achieve the literature reported grading accuracy of 75 %. • Most radiologists have limited experience of grading Crohn's disease activity on MRI. • Inexperienced readers need training in the MRI assessment of Crohn's disease. • Grading accuracy, understaging, reading time and confidence scores improved during training. • Radiologists and residents show similar accuracy in grading Crohn's disease. • After 100 cases, grading accuracy can be reached as reported in the literatur

Long-Term Performance of Readers Trained in Grading Crohn Disease Activity Using MRI

We aim to evaluate the long-term performance of readers who had participated in previous magnetic resonance imaging (MRI) reader training in grading Crohn disease activity. Fourteen readers (8 women; 12 radiologists, 2 residents; mean age 40; range 31-59), who had participated in a previous MRI reader training, participated in a follow-up evaluation after a mean interval of 29 months (range 25-34 months). Follow-up evaluation comprised 25 MRI cases of suspected or known Crohn disease patients with direct feedback; cases were identical to the evaluation set used in the initial reader training (of which readers were unaware). Grading accuracy, overstaging, and understaging were compared between training and follow-up using a consensus score by two experienced abdominal radiologists as the reference standard. In the follow-up evaluation, overall grading accuracy was 73% (95% confidence interval [CI]: 62%-81%), which was comparable to reader training grading accuracy (72%, 95% CI: 61%-80%) (P = .66). Overstaging decreased significantly from 19% (95% CI: 12%-27%) to 13% (95% CI: 8%-21%) between training and follow-up (P = .03), whereas understaging increased significantly from 9% (95% CI: 4%-21%) to 14% (95% CI: 7%-26%) (P  < .01). Readers have consistent long-term accuracy for grading Crohn disease activity after case-based reader training with direct feedbac

Serial magnetic resonance imaging for monitoring medical therapy effects in Crohn's disease

Tumor necrosis factor (TNF) antagonists can induce mucosal healing in patients with Crohn's disease (CD), but the effects on transmural inflammation and stenotic lesions are largely unknown. We performed a retrospective study in 50 patients (54% female, median age 37 yr) with CD who had undergone serial magnetic resonance imaging (MRI) examinations while receiving infliximab or adalimumab. Patients were grouped as clinical responders or nonresponders based on physician's assessment, laboratory, and endoscopic appearance. MRI scoring was performed by 2 radiologists in consensus blinded to clinical data using a validated MRI scoring system. In total, 64 lesions on MRI were identified for analysis. Analyses were performed using paired t test and Wilcoxon rank test. During anti-TNF treatment, MRI inflammation scores improved in 29 of 64 lesions (45.3%), remained unchanged in 18 of 64 lesions (28.1%), or deteriorated in 17 of 64 lesions (26.6%) over time. In the anti-TNF responder group, the mean intestinal inflammation score of all lesions improved from 5.19 to 3.12 (P < 0.0001). The mean inflammation scores in stenotic lesions in anti-TNF responders also improved significantly, from 6.33 to 4.58 (P = 0.01). In contrast, the mean inflammation scores did not change significantly (5.55-5.92, P = 0.49) in nonresponders. Diagnostic accuracy of anti-TNF response on MRI was 68%. Improved inflammatory activity on serial MRI scans was observed in patients with clinical response to medical therapy with anti-TNF agents in luminal CD. MRI can be used as a complementary approach to measure transmural inflammation in patients with CD and guide the optimal use of TNF antagonists in daily clinical practic

A prospective study comparing water only with positive oral contrast in patients undergoing abdominal CT scan

Consecutive adults scheduled to undergo abdominal CT with oral contrast were asked to choose between 1000 ml water only or positive oral contrast (50 ml Télébrix-Gastro diluted in 950 ml water). Two abdominal radiologists independently reviewed each scan for image quality of the abdomen, the diagnostic confidence per system (gastrointestinalsystem/organs/peritoneum/retroperitoneum/lymph nodes) and overall diagnostic confidence to address the clinical question (not able/partial able/fully able). Radiation exposure was extracted from dose reports. Differences between both groups were evaluated by Student’s t-test, Mann-Whitney-U-test or chi-square-test. Of the 320participants, 233chose water only. All baseline characteristics, image quality of the abdomen and the diagnostic confidence of the organs were comparable between groups and both observers. Diagnostic confidence in the water only group was more commonly scored as less than good by observer1. The results were as follows: the gastrointestinal system(18/233vs1/87; p = 0.031), peritoneum (21/233vs1/87; p = 0.012), retroperitoneum (11/233vs0/87; p = 0.040) and lymph nodes (11/233vs0/87; p = 0.040). These structures were scored as comparable between both groups by observer2. The diagnostic confidence to address the clinical question could be partially addressed in 6/233 vs 0/87 patients (p = 0.259). The water only group showed a tendency towards less radiation exposure. In summary, most scan ratings were comparable between positive contrast and water only, but slightly favored positive oral contrast for one reader for some abdominal structures. Therefore, water only can replace positive oral contrast in the majority of the outpatients scheduled to undergo an abdominal CT

Grading Crohn disease activity with MRI: interobserver variability of MRI features, MRI scoring of severity, and correlation with Crohn disease endoscopic index of severity

The purpose of this article is to assess the interobserver variability for scoring MRI features of Crohn disease activity and to correlate two MRI scoring systems to the Crohn disease endoscopic index of severity (CDEIS). Thirty-three consecutive patients with Crohn disease undergoing 3-T MRI examinations (T1-weighted with IV contrast medium administration and T2-weighted sequences) and ileocolonoscopy within 1 month were independently evaluated by four readers. Seventeen MRI features were recorded in 143 bowel segments and were used to calculate the MR index of activity and the Crohn disease MRI index (CDMI) score. Multirater analysis was performed for all features and scoring systems using intraclass correlation coefficient (icc) and kappa statistic. Scoring systems were compared with ileocolonoscopy with CDEIS using Spearman rank correlation. Thirty patients (median age, 32 years; 21 women and nine men) were included. MRI features showed fair-to-good interobserver variability (intraclass correlation coefficient or kappa varied from 0.30 to 0.69). Wall thickness in millimeters, presence of edema, enhancement pattern, and length of the disease in each segment showed a good interobserver variability between all readers (icc = 0.69, κ = 0.66, κ = 0.62, and κ = 0.62, respectively). The MR index of activity and CDMI scores showed good reproducibility (icc = 0.74 and icc = 0.78, respectively) and moderate CDEIS correlation (r = 0.51 and r = 0.59, respectively). The reproducibility of individual MRI features overall is fair to good, with good reproducibility for the most commonly used features. When combined into the MR index of activity and CDMI score, overall reproducibility is good. Both scores show moderate agreement with CDEI

Evaluation of the modified Van Assche index for assessing response to anti-TNF therapy with MRI in perianal fistulizing Crohn's disease

Background: Structured evaluation of magnetic resonance imaging (MRI) is important to guide clinical decisions of perianal fistulas in Crohn's disease (CD) patients. Purpose: To evaluate the recently developed modified Van Assche index to assess clinical responses to anti-tumor necrosis factor (TNF) therapy in patients with perianal fistulizing CD. Methods: A search of medical records identified patients with fistulizing perianal CD who underwent baseline and follow-up MRI while receiving anti-TNF treatment. Patients were divided into clinical responders and non-responders based on physician's assessment. MRI-scans were scored using the original and modified Van Assche index and scores between baseline and follow-up were compared within clinical responders and non-responders. Results: Thirty cases were included (48% female, median age 27 years). Clinical responders (n = 16) had a median modified Van Assche score of 9.6 (IQR 5.8–12.7) at baseline and 5.8 (IQR 3.5–8.5) at follow-up (p = 0.008). In non-responders (n = 14), corresponding scores were 7.7 (IQR 5.8–13.5) and 8.2 (IQR 5.8–11.5) (p = 0.624). In clinical responders, 6/16 showed no drop in modified Van Assche score at follow-up. Scores obtained with the original Van Assche index dropped between baseline and follow-up in clinical responders (13.0 vs. 9.6, p = 0.011), whereas no decrease was observed in non-responders (11.5 vs. 11.5, p = 0.324). Conclusions: While the modified Van Assche index overall decreases significantly in patients with perianal fistulas responding to anti-TNF treatment, one third of responders had unaltered scores at follow-up. Also, outcomes were comparable to the original Van Assche index. Further optimization of the modified Van Assche index is needed before application in larger studies

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 Crohn's 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(Observer 1) = 0.29, p = 0.2; r(Observer 2) = 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 Crohn's diseas

Evaluation of conventional, dynamic contrast enhanced and diffusion weighted MRI for quantitative Crohn's disease assessment with histopathology of surgical specimens

To prospectively compare conventional MRI sequences, dynamic contrast enhanced (DCE) MRI and diffusion weighted imaging (DWI) with histopathology of surgical specimens in Crohn's disease. 3-T MR enterography was performed in consecutive Crohn's disease patients scheduled for surgery within 4 weeks. One to four sections of interest per patient were chosen for analysis. Evaluated parameters included mural thickness, T1 ratio, T2 ratio; on DCE-MRI maximum enhancement (ME), initial slope of increase (ISI), time-to-peak (TTP); and on DWI apparent diffusion coefficient (ADC). These were compared with location-matched histopathological grading of inflammation (AIS) and fibrosis (FS) using Spearman correlation, Kruskal-Wallis and Chi-squared tests. Twenty patients (mean age 38 years, 12 female) were included and 50 sections (35 terminal ileum, 11 ascending colon, 2 transverse colon, 2 descending colon) were matched to AIS and FS. Mural thickness, T1 ratio, T2 ratio, ME and ISI correlated significantly with AIS, with moderate correlation (r = 0.634, 0.392, 0.485, 0.509, 0.525, respectively; all P  < 0.05). Mural thickness, T1 ratio, T2 ratio, ME, ISI and ADC correlated significantly with FS (all P  < 0.05). Quantitative parameters from conventional, DCE-MRI and DWI sequences correlate with histopathological scores of surgical specimens. DCE-MRI and DWI parameters provide additional information. • Conventional MR enterography can be used to assess Crohn's disease activity. • Several MRI parameters correlate with inflammation and fibrosis scores from histopathology. • Dynamic contrast enhanced imaging and diffusion weighted imaging give additional information. • Quantitative MRI parameters can be used as biomarkers to evaluate Crohn's disease activit

Semi-automatic bowel wall thickness measurements on MR enterography in patients with Crohn's disease

To evaluate a semi-automatic method for delineation of the bowel wall and measurement of the wall thickness in patients with Crohn's disease. 53 patients with suspected or proven Crohn's disease were selected. Two radiologists independently supervised the delineation of regions with active Crohn's disease on MRI, yielding manual annotations (Ano1, Ano2). Three observers manually measured the maximal bowel wall thickness of each annotated segment. An active contour segmentation approach semi-automatically delineated the bowel wall. For each active region, two segmentations (Seg1, Seg2) were obtained by independent observers, in which the maximum wall thickness was automatically determined. The overlap between (Seg1, Seg2) was compared with the overlap of (Ano1, Ano2) using Wilcoxon's signed rank test. The corresponding variances were compared using the Brown-Forsythe test. The variance of the semi-automatic thickness measurements was compared with the overall variance of manual measurements through an F-test. Furthermore, the intraclass correlation coefficient (ICC) of semi-automatic thickness measurements was compared with the ICC of manual measurements through a likelihood-ratio test. Patient demographics: median age, 30 years; interquartile range, 25-38 years; 33 females. The median overlap of the semi-automatic segmentations (Seg1 vs Seg2: 0.89) was significantly larger than the median overlap of the manual annotations (Ano1 vs Ano2: 0.72); p = 1.4 × 10(-5). The variance in overlap of the semi-automatic segmentations was significantly smaller than the variance in overlap of the manual annotations (p = 1.1 × 10(-9)). The variance of the semi-automated measurements (0.46 mm(2)) was significantly smaller than the variance of the manual measurements (2.90 mm(2), p = 1.1 × 10(-7)). The ICC of semi-automatic measurement (0.88) was significantly higher than the ICC of manual measurement (0.45); p = 0.005. The semi-automatic technique facilitates reproducible delineation of regions with active Crohn's disease. The semi-automatic thickness measurement sustains significantly improved interobserver agreement. Advances in knowledge: Automation of bowel wall thickness measurements strongly increases reproducibility of these measurements, which are commonly used in MRI scoring systems of Crohn's disease activit