Didier Bielen

Magnetic resonance imaging of the effects of infliximab on perianal fistulizing Crohn's disease.

OBJECTIVES:Although the clinical efficacy of infliximab as measured by closure of fistulas in Crohns disease has been demonstrated, its influence on the inflammatory changes in the fistula tracks is less clear. The aim of the present study was to assess the behavior of perianal fistulas before and after infliximab treatment.METHODS:Magnetic resonance imaging (MRI) and clinical evaluation were performed in a total of 18 patients before and after treatment with infliximab. An MRI-based score of perianal Crohns disease severity was developed using both criteria of local extension of fistulas (complexity, supralavetoric extension, relation to the sphincters and of active inflammation (T2 hyperintensity, presence of cavities/abscesses, and rectal wall involvement).RESULTS:The MRI score was reliable in assessing the fistula tracks, with a good interobserver concordance (p < 0.001). Fistula tracks with signs of active inflammation were found in all 18 patients at baseline and collections in seven. After short-term infliximab treatment, active tracks persisted in eight of 11 patients who had clinically responded to infliximab. After long-term (46 wk) infliximab therapy, MRI signs of active track inflammation had resolved in three of six patients.CONCLUSIONS:We have developed an MRI-based score of perianal Crohns disease severity to assess the anatomical evolution of Crohns fistulas. Our study demonstrates that despite closure of draining external orifices after infliximab therapy, fistula tracks persist with varying degrees of residual inflammation, which may cause recurrent fistulas and pelvic abscesses. Whether complete fistula fibrosis occurs over time with repeated infliximab infusions needs further study.

Respiration-induced movement of the upper abdominal organs: a pitfall for the three-dimensional conformal radiation treatment of pancreatic cancer.

Respiration-induced movement of the upper abdominal organs (pancreas, liver and kidneys) was assessed in 12 subjects using dynamic magnetic resonance imaging. The movement of each organ in the cranio-caudal, the lateral and the anterior-posterior direction was deduced from the movement of the center of gravity on two-dimensional images. This center of gravity was computed from the volume delineated on sequential 8-mm slices of both sagittal and coronal dynamic series. The largest movements were noticed in the cranio-caudal direction for pancreas and liver (23.7+/-15.9 mm and 24.4+/-16.4 mm). The kidneys showed smaller movements in the cranio-caudal direction (left kidney 16.9+/-6.7 mm and right kidney 16.1+/-7.9 mm). The movements of the different organs in the anterior-posterior and lateral directions were less pronounced. It is of the greatest importance to be aware of these movements in the planning of a conformal radiation treatment for pancreatic cancer.

Patient acceptance for CT colonography: what is the real issue?

Abstract. The aim of this study was to evaluate the discomfort associated with CT colonography compared with colonoscopy and bowel purgation cleansing, and to evaluate patient preference between CT colonography and colonoscopy. In a total of 124 patients, scheduled for multidetector virtual CT colonography and diagnostic colonoscopy, patient acceptance and future preference were assessed during the different steps of the procedure (colon preparation, CT examination, and conventional colonoscopy). Patients who described contradictory findings between the degree of discomfort and their preference regarding follow-up examinations were retrospectively reinterviewed regarding the reason for this discrepancy. Colonoscopy was graded slightly more uncomfortable than virtual CT colonography, but the preparation was clearly the most uncomfortable part of the procedure. Concerning their preference regarding follow-up examinations, 71% of the patients preferred virtual CT colonography, 24% preferred colonoscopy, and 5% had no preference. Twenty-eight percent of the patients preferred virtual CT colonography despite that they thought it was equally or even more uncomfortable than colonoscopy. This was mainly due to the faster procedure (17 patients), the lower physical challenge (14 patients), and the lack of sedation (12 patients) of virtual CT colonography. Factors other than the discomfort related to the examinations play an important role in the patients preference for virtual CT colonography, namely the faster procedure, the lower physical challenge, and the lack of sedation. Since the preparation plays a major decisive factor in the patient acceptance of virtual CT colonography, more attention should be given to fecal tagging.

Long-Term Monitoring of Infliximab Therapy for Perianal Fistulizing Crohn's Disease by Using Magnetic Resonance Imaging

BACKGROUND & AIMS Magnetic resonance imaging (MRI) is used to assess the outcome of infliximab (IFX) therapy in patients with perianal fistulizing Crohns disease (pfCD). However, few long-term data are available about its efficacy. METHODS We assessed 59 patients with pfCD by MRI and clinical evaluation at baseline. Treated patients then received paired clinical and MRI examinations for a median time period of 36 (11-53.3) weeks. Short-, mid-, and long-term effects of therapy, as well as the ability of MRI to predict treatment outcome and need for surgery, were evaluated. RESULTS Compared with the baseline MRI, the short-term follow-up MRI (n = 29) revealed a reduced number of fistula tracks in 13.8% and in the inflammatory activity in 55.2% of patients, respectively; mid-term MRI (n = 25) in 56% and in 52%, respectively; and long-term MRI (n = 13) in 15.4% and in 31%, respectively. Improvement of pfCD based on MRI results coincided with clinical improvement in 54.7% of the patients. Short-term and mid-term (but not long-term) MRI showed a significant decrease in the activity score. Therapy outcome was worse among patients with persisting fistulas (P = .01), collections (P = .009), and rectal wall involvement (P = .01) in the final MRI. Patients with single-branched fistulas (P < .0001) and collections (P = .006) in their baseline MRI were more likely to undergo surgery. CONCLUSIONS MRI is a useful technique for evaluation of pfCD during the first year of follow-up. In the long-term, the MRI improvement coincides with clinical and endoscopic response to IFX in 50% of the patients.

Stool tagging applied in thin-slice multidetector computed tomography colonography.

Objective To compare thin-slice multidetector computed tomography colonography (CTC) that uses stool tagging with colonoscopy. Method One hundred fifty patients scheduled for colonoscopy underwent high-resolution CTC. An iodinated contrast agent was added to the preparation to tag the residual colonic fluid and stool. The effect of fluid tagging was assessed first. Sensitivity and specificity were calculated for two independent readers. In addition, values were recalculated separately for the first and last 75 patients. Results Tagging was optimal in 95.3% of the cases, and reader confidence was high. Sensitivities were 64.1%–66.7% (for the 2 readers) for 5- to 9-mm polyps and 91.7% for larger polyps. The overall specificity was 94.2% and 95%. Sensitivity improved during the study for both 5- to 9-mm polyps (from 54.2%–58.3% to 80%) and polyps larger than 9 mm (from 50% to 100%). Specificity changed nonuniformly. Conclusion The combination of fluid tagging and high-resolution scanning in CTC showed high sensitivity and specificity, especially concerning sensitivity for polyps of 10 mm and larger.

Age Calculation Using X-ray Microfocus Computed Tomographical Scanning of Teeth: A Pilot Study

To correlate dental age with an individuals chronological age based on the calculated volume ratio of pulp versus tooth volume measured, an X-ray microfocus computed tomography unit (microCT) with 25 microm spatial resolution was used to non-destructively scan 43 extracted single root teeth of 25 individuals with well-known chronological age. Custom-made analysis software was used by two examiners to obtain numerical values for pulpal and tooth volume. The ratio of both was calculated and statistically processed. No significant intra- or inter-examiner differences were found. In fact, a very strong concordance correlation coefficient was found. Linear regression analysis showed a coefficient of determination (r) of 0.31 which suggests that there is a rather weak correlation between the volume ratio of pulp versus tooth and biological age. Although rather time consuming, this technique shows promising results for dental age estimation in a non-destructive manner using X-ray microfocus computed tomography.

Value of carbon dioxide wedged venography and transvenous liver biopsy in the definitive diagnosis of Abernethy malformation.

We report a 25-year-old man who presented with congenital absence of the portal vein, or Abernethy malformation, a rare congenital disorder in which the mesenteric and splenic venous drainages bypass the liver and directly drain into the inferior vena cava through an extrahepatic portosystemic shunt. Magnetic resonance imaging, which showed multiple nodular lesions in both liver lobes that were associated with an absence of intrahepatic portal venous branches, strongly suggested the diagnosis of the Abernethy malformation. Carbon dioxide wedged venography and transvenous liver biopsy, which were performed in the same session by a right jugular approach, confirmed these findings. This technique can be considered a valuable alternative diagnostic tool to catheter arteriography and percutaneous transhepatic liver biopsy.

Clinical validation of high‐resolution fast spin‐echo MR colonography after colon distention with air

To evaluate the feasibility of MR colonography (MRC) with air using two‐dimensional (2D) T1‐weighted fast spin‐echo (T1wFSE) in patients scheduled for conventional colonoscopy (CC) after classic bowel preparation, and assess the ability of the technique to detect colonic lesions. The distention was sufficient for diagnosis, and the technique provided adequate delineation of the wall in the majority of segments. Residual fluid obscured the wall in different segments, especially in the ascending and descending colon (supine position) and in the cecum, transverse, and sigmoid colon (prone position). These findings were consistent with CT colonography. MRC visualized three lesions, missed one lesion >10 mm, visualized none of four lesions <5 mm, and yielded one false‐positive lesion (5–10 mm). Missed lesions can be due to inconsistency in the slice positions between consecutive breath‐holds, which is inherent to the multishot technique. Residual fluid may have obscured the smaller lesions. The shortcomings of the technique are limited coverage and signal drop‐off at the borders of the field of view (FOV). Before multishot 2D T1wFSE colonography can become a valid screening method, improved patient preparation and a more practical technique are needed. J. Magn. Reson. Imaging 2005.

Computer aided detection for low-dose CT colonography

The paper describes a method for automatic detection of colonic polyps, robust enough to be directly applied to low-dose CT colonographic datasets. Polyps are modeled using gray level intensity profiles and extended Gaussian images. Spherical harmonic decompositions ensure an easy comparison between a polyp candidate and a set of polypoid models, found in a previously built database. The detection sensitivity and specificity values are evaluated at different dose levels. Starting from the original raw-data (acquired at 55mAs), 5 patient datasets (prone and supine scans) are reconstructed at different dose levels (down to 5mAs), using different kernel filters and slice increments. Although the image quality decreases when lowering the acquisition mAs, all polyps above 6mm are successfully detected even at 15 mAs. Accordingly the effective dose can be reduced from 4.93mSv to 1.61 mSv, without affecting detection capabilities, particularly important when thinking of population screening.

Ovarian torsion in a premenarcheal girl: MRI findings

Adnexal torsion is an uncommon cause of severe lower abdominal pain in women and is often difficult to distinguish from other acute abdominal conditions. However, adnexal torsion should be considered in premenarcheal girls admitted with acute abdominal pain and evidence of an ovarian mass. Accurate and early radiological diagnosis is mandatory immediately after onset of clinical symptoms in order to preserve the viability of the ovary. Ultrasound (US) is usually the first line examination performed in an emergency setting, but computed tomography (CT) and magnetic resonance imaging (MRI) can be useful in case of ambiguous US findings, especially in patients with sub-acute symptoms and a suspected adnexal mass. This case report describes the additional value of MRI in a premenarcheal girl with sub-acute right fossa pain.