Computed Tomography Enterography vs Magnetic Resonance Enterography - Article Example

Comparison between CTE and MRE Objective To conduct a comparison of the overall diagnostic accuracy of computed tomography enterography with magnetic resonance enterography in the evaluation of disease activity in small bowel Crohn’s disease. Background Techniques that include CTE and MRE are increasingly being utilized for assessment of Crohn’s disease (CD). Methods Identification of relevant publications by literature search and their selection was based on some predefined parameters of quality, including: sample size, a prospective design, and a reference standard. 30 publications in total were chosen for the purpose of this search. Discussion MRE has a greater diagnostic for the prediction of suspected CD and the assessment of disease activity and extension (specificity 0.90; sensitivity 0.93). CTE is also similar in accuracy to the MRE. Both techniques are highly accurate in identity of abscesses and fistulas (sensitivities and specificities are greater than 0.80). However, MRE should be preferred over CT in young patients because of the absence of radiation. Conclusion Both CTE and MRE have high accuracy in the assessment of suspected, as well as, established CD and are reliable in measuring complications and disease severity and give the probability of monitoring disease progress. Key words a) Crohn disease (CD) b) Computed tomography enterography (CTE) c) Magnetic resonance imaging (MRI) d) magnetic resonance enterography (MRE) 2) Introduction (epidemiology) Studies describe Crohn disease as a chronic inflammatory disease associated with the gastrointestinal tract and characterized by segmental and transmural swelling of the walls of the intestines. Its prevalence is increasing while its etiology is not known, though evidence suggests that genetic predisposition in combination with the abnormal interaction of the gut and enteric microbes is likely to play a role in its pathogenesis.1, 3,9,11 Studies investigating the pathology of CD have established that Crohn’s disease present with insidious or abrupt onset of diarrhoea and abdominal pain; this is accompanied by weight loss and fever. Bowel ulceration may cause fistulas and extramural abscesses. Pathologic findings of Crohn disease in the alimentary canal encompass deep ulcers, transmural granulomatous inflammation. 2, 3, 5 This may progress to fistulae and sinus tracts, discontinuous involvement with areas between diseased segments and structures that can result in intestinal obstruction. Extra-intestinal manifestations include: cholelithiasis, arthritis, dermatologic abnormalities, growth retardation in children and ocular manifestations. Evaluation of inflammatory lesions in the intestines is crucial for managing CD patients, identification of disease extension and location during diagnosis is required in establishing a good management plan. These techniques are also accepted for the detection of all complications and strictures related to CD. 4, 12, 24 Some patients with an established CD diagnosis have no evidence of active CD through endoscopic, laboratory or radiologic means. In two clinical trials, 20% of CD patients with moderate-to severe symptoms do not have evidence of ulcer during ileocolonoscopy. Another proportion of patients with CD can have severe and persistent lesions, which is associated with a need for more hospitalization and surgeries. 4, 12 Objective evaluations of inflammatory lesions are thus required to guide and assess therapeutic interventions. To achieve this, a systematic review of recent literature is needed on the overall diagnostic accuracy of CTE versus MRE in assessing disease activity in ileocolonic Crohn’s disease. 1, 5 Research in this area will aid in identifying which technique is suitable for identifying strictures, fistulas, abdominal nodes e.t.c. Ileocolonoscopy is the standard for assessing colon and terminal ileum lesions, but there are many drawbacks that are related to discomfort procedure and invasiveness, the risk of poor patient performance and bowel perforation. 3, 10, 11 CTE and MRE have been used extensively in the evaluation of CD patients. The determination of choice between these techniques depends on expertise and local availability, and the details of such examinations are subject to variation and may affect accuracy. 3, 5, 9 The purpose of this present review is to give an objective comparison of the overall diagnostic accuracy of CTE and MRE in assessing disease activity in ileocolonic CD. The recommendations for using imaging techniques as given in this review are on the basis of analysis of selected evidence, according to quality, done by seven gastroenterologists with inflammatory experience in inflammatory bowel disease as well as the six radiologists, who are experienced in using MRE and CTE. 3) Methods A comprehensive search of the literature was done to identify all the relevant citations. The search strategy encompassed searches of Medline, PubMed and Sci Direct. This electronic search was supplemented through manual review of reference lists of those studies included as well as review articles that are relevant. 3, 11, 17, 24 The search comprised of review articles from year 2006 onwards and those including 30 subjects or more. The following criteria of searching were used: MRE, CTE, Crohn disease imaging, inflammatory bowel disease and magnetic resonance imaging (MRI). 3, 11 References for the selected articles were examined in the search of studies that meet the inclusion criteria. A total of 5 reviewers (TR, SQ, BM, JR and RB) assessed the eligibility of articles independently for inclusion. The search has given a total of 1300 articles, of which 31 were eligible and were retrieved as fully for conspicuous analysis.1, 11, 14, 21 The selection of final articles was done following the criteria whereby: i) Were primary articles ii) published after 2006, in English and more than 30 patients were included; iii) CTE and MRE were used to diagnose CD iv) adequacy of reference standard inclusive of capsule endoscopy, ileocolonoscopy v) prospective design vi) all data that enable specificity and sensitivity calculation. Disagreements among reviewers in regard to the inclusion criteria were resolved by the consensus of all the authors. In following such criteria, 31 articles that fulfil all the criteria of inclusion were included in the final analysis. 10,11,24,26 The mean specificity and sensitivity were expressed as a weighted mean with correspondence to the 95% intervals of confidence in order to allow for the varying number of patients that were included in each study. Specificity and sensitivity were later calculated on per-bowel segment or per-patient. 5, 12, 14 Segmental data provides information that determines disease extent and the capability of localized disease. Per-patient basis may overestimate sensitivity values. 4) Discussion Comparison of the diagnostic accuracy of CTE vs. MRE The 10 Studies that were considered were inclusive of patients suspected with CD. These studies were selected only if the results of accuracy were available for those suspected with the CD alone. 1-7, 11, 13, 26 An exclusion of those studies that included patients with CD was also considered. CTE diagnostic accuracy Two studies suggest that CTE examination of the small bowel, use a comparison of the multi-detector row temporal resolution and improved spatial resolution together with high volumes of material of neutral enteric contrast that have been ingested. 12,13 This is in order to enable visualization of the wall and lumen of the small bowel. Researchers suggest that CTE has several advantages when compared with traditional SBFT examinations. These include: allowing for evaluation of ileal loops that are deep into the pelvis without superimposition, moreover, it displays the entire bowel thickness. 1-3, 5-10 Another merit is that it allows for the assessment of the surrounding mesentry and the perienteric fat. Additionally, CTE allows for evaluation of solid organs as well as provide for an overview of the abdomen. According to Wold et al, Given that patients do accept the oral administration of the contrast material more readily, and that it results in levels of luminal distension that are acceptable, CTE is now becoming the preferred diagnostic mode for Crohn disease and other disorders. 5, 9, 11 It is excellent in its depiction of intramural, intra-luminal and extra-enteric abnormalities associated with the small bowel and thus CTE performs well diagnostically. MRE diagnostic accuracy Magnetic resonance imaging has recently emerged as a non-ionising modality that may benefit these patients. 10, 15, 25 Many studies have established that MRI is advantageous due to its high resolution of tissue contrast and lack of ionizing radiation. 8,13 Additionally, MRI provides accuracy of anatomical detail, prediction and identity of extra-intestinal abnormalities as well as enhanced distinction between abscesses, phlegmon and mesenteric lymphadenopathy . 11, 28, 29 It is not evident enough that MI can depict early ulceration of the mucosa reliably. However, a recent review has shown the value of great resolution MRI in the detection of early ulcerations. 28 Researchers suggest that MRE examinations combine the temporal and spatial resolution or MRI with high amounts of oral contrast material that has been ingested in order to achieve luminal distension. 1, 11, 25 The oral uptake of contrast material enables for nasojejunal intubation. The enterographic technique can deem to be less discomfiting to the patient and may not give a similar distension of the bowel such as that can be obtained through MR enteroclysis examination. Studies have however shown that MRE can give a diagnostic accuracy that is same to that obtained by MR enteroclysis examination. 10, 15, 17, 25 However, MRE is associated with acceptability and higher patient tolerance than examinations of enteroclysis. It also has the ability of becoming an essential technique of imaging in the process of the diagnostic work up in suspected patients of small-bowel disease. 6, 11 Reports from researchers encompass patient tolerance of MRE as well as high specificity and sensitivity in Crohn disease patients. 1, 6, 11, 15 Discuss CTE and MRE techniques CTE techniques Four studies investigating how CTE works on the detection of CD have found that patients undergoing CTE are required not to drink or eat in the last 4 hours before scanning. Agents that aid in the improvement of luminal distension are used in CTE. Polyethylene glycol (PEG) solution has thus replaced solutions of water-methylcellulose. 5,13,18-19 According to Wold et-al, another suitable alternative to this solution, is barium of low concentration which has been mixed with sorbitol, which promotes distension of the lumen as well as limits the water resorption across the entire small bowel. The attenuation level of barium solution is low at 20HU, allowing for adequate assessment of normal as well as improved mural enhancement of the small bowel. 5, 17 Barium solutions have also proven to distend the small bowel better as well as with less side effects than PEG, water or solutions of water-methylcellulose. 29 An analysis of the four studies described CTE technique as follows: The regimen comprised ingestion of 1350ml low-concentration barium while sticking to the schedule that follows: 225 ml some 10-20 mins before scanning or 450ml within 40-60 mins before scanning. 5, 29 While utilizing PEG electrolyte for scanning, the schedule of administration was as follows: 200ml of the solution was given within 60 mins before scanning by starting with the first 1500ml over 15mins and two aliquots of 250ml;administered between 25 and 15 mins prior to scanning respectively 4,11,17 IV administration of iohexol at the rate of 4ml/sec was then done, after which scanning was conducted on 8-64 multi-detector row channels of CT scanners and commencing 45 sec after the start of injection of the contrast material. 8 Images were achieved with a thickness of 2.0-2.5mm as well as a reconstruction interval of between 1-1.5. Some of these images were also generated from axial images at the workstation for some other scanners 2,19-20 To allow for coronal imaging, 3mm-thick sections were created every 2mm thus generating images that overlap starting with the anterior abdominal skin upto the posterior gluteal skin. This ensured that any forms of fistulous tracts were displayed. MRE techniques According to 6 studies, MRE uses a combination of ultrafast MRI sequences and good bowel distension to obtain diagnostic images of the small bowel. 1, 6, 11, 28-30 Many contrast agents have been explained that include: methylcellulose and solutions containing polythene glycol, mannitol and locust bean gum. These agents do work by slowing the water resorption in the intestine. 4,6,29 Continued slow uptake of the material of oral contrast over some minutes is able to give a display of homogenous opacification within the entire lumen of the small-bowel. Ippolito et al argues that the specific protocol for MRE gives a requirement that the patient should fast for about 6 hours prior to the procedure. 29 Fasting is essential as it reduces the amounts of debris and food residue within the intestinal lumen which can be mistaken for polyps or mass lesions. Patients should also follow a diet of low residue for the next 5 days. 15 This diet enhances the decrease of fecal matter within the colon, which thus facilitates the transit of the contrast agent in the small bowel. This is because fecal material is able to delay the times of transit within the small bowel. 11,28- 29 In accordance with the 6 studies, diagnosis was started on the patient by a series of steps. He or she ingested between 1200-1300 litres of an iso-osmotic solution of polyethylene mixed with water and electrolytes, or water mixed with mannitol to give a 3% solution. 1,6, 11, 28-30 The oral solution was then divided into two portions of 600-650ml each and the patient took one of the aliquots within 25-30 mins. 1, 6, 29 A suspension containing 10mg metoclopramide was administered together with the first aliquot in order to facilitate gastric emptying and just before imaging could be performed, patients were required to ingest another 200ml of the contrast material to aid to opacify the duodenum and the stomach. 6,11 After completing the oral phase, imaging of the patients was done using a thick slab of HASTE sequence. This gave single-shot images that showed an opacified small bowel which assisted to determine if the contrast material had arrived at the ileocecal junction. 1 mg of glucagon was then administered intravenously to decrease bowel peristalsis. 6, 29 HASTE images were observed on a slab for bowel obstruction, MR fluoroscopy of the lumen, mesentery and the bowel wall. Compare sensitivity and specificity values for CTE and MRE A vast majority of studies have shown the superiority in performance of CTE as compared to standard techniques such as SBFT. 5-7,11,28 For instance, the specificity and sensitivity values of CTE in a study comprising 35 patients conducted by Neegard et al were 90% and 85%, respectively, while that of SBFT, specificity and sensitivity values were 95% and 67% respectively. 6 Although the difference was not statistically significant, CTE deemed more sensitive in detecting of fistulas and abscesses. Results of varying nature, have emanated from several studies that compare CTE with capsule endoscopy. For example, in a study by Hara et al comprising of 37 patients, the yield upon diagnosis was greater at 81% for capsule endoscopy as compared to ileoscopy which stood at 67%, CTE at 63% and SBFT at 34%.7 Another prospective comparison of similar tests for 41 patients utilizing a clinical consensus approach as opposed to diagnostic yield and the results found that CTE and capsule endoscopy had the same sensitivities at 82-83%. However, the specificity of CTE was higher at 89% as compared to capsule endoscopy at 53%. 5 A prospective study of 40 patients with proven histological IBD using MRE or MR enteroclysis showed that the latter was much superior than MRE in achieving distension of the bowel as well as detection of abnormalities within the bowel lumen.28 Many studies have compared the utilization of CTE and MRE. These studies have shown similar sensitivities upon diagnosis of CD.CTE however gives better images. According to Lee et al, MRE and CTE have depicted similar accuracy levels in identification of active CD, with sensitivity values of 83% and 89%, respectively, while the specificity values were at 100% and 80% respectively 11. Prospective comparisons of CTE and MRE by Siddiki et al depicted same sensitivities of 90.2 and 95.2% respectively. 2 Studies comparing MRI and CTE have, however, depicted the superiority of MRI in the detection of strictures and fistula. 1,2,11 One more study by Jensen et al 1 comprising of 44 patients showed similar sensitivity, accuracy and specificity for MRE and CTE in the following order: 0.88 (0.78-0.99, 95% 95% CI), 0.88 (0.68–1.0, 95% CI) and 0.88, respectively (P= 1.0). These techniques showed a similar level of specificity of 0.91 (0.76–1.0, 95% CI) sensitivity 0.90 (0.80–1.0, 95% CI and accuracy of 0.90 (P = 1.0).similar depiction of sensitivity and specificity values for both MRE and CTE across different parameters is summarised in the table 1 below. Discuss the facets that will influence the findings for sensitivity and specificity Sensitivity and specificity of CTE and MRE techniques rely on disease location and activity. According to Hara et al in order to achieve diagnostic accuracy, following the right procedure in both techniques is essential. 7 Use of oral contrast agents is also paramount to enhance bowel distension and nasojejunal intubation. Polyethylene glycol or barium solutions should be preferred to water and solutions of water-methylcellulose. 5, 13 Several other studies recognize per-oral hyper-hydration of patients prior to scanning as well as sticking to the time period of uptake of oral contrast material prior to scanning as crucial. 5,13,18 30 Lee et al argues that the suggested period of time for ingestion is of paramount importance and should be adhered to, lack of which, causes delays ingestion which results in a great portion of the solution filling the colon. 11 Reduced uptake of the contrast material may lead to less than optimal distension of the small bowel. However, the uptake of the oral solution over a prolonged period of time such as between 50-60 mins enhances consistent and uniform filling of the distal and proximal small bowel. Researchers agree to the fact that fasting of patients should be encouraged for about 4 hours prior to scanning. 5, 13, 18 Moreover, the thickness of the slab is an important consideration in achieving accuracy of either CTE or MRE. In order to allow for coronal imaging, 3mm-thick sections are created every 2mm, thus generating images that overlap starting with the anterior abdominal skin up to the posterior gluteal skin. This ensures that any forms of fistulous tracts are displayed. 5, 18, 30 The differences in sensitivity and specificity levels were dependent on; the type of contrast agent used, for example, barium solution and polyethylene glycol, give a good mural hyperenhancement of the mucosa compared to water and solutions of water-methylcellulose; disease location and severity, for instance CTE was more sensitive in identifying fistulas and strictures than MRE because of the formation of clear images. Moreover, the thickness of the slab and the type of sequence upon which the image is observed is another facet that gives the differences. 10, 28-30 5) Conclusion Most researchers agree that Crohn disease found in the small bowel can be efficiently and effectively assessed using MRE and CTE because through these modes, greater accuracy is achieved than in the conventional barium studies. Observed studies on Comparison of diagnostic accuracy of CTE and MRE in the evaluation of disease activity have shown that both techniques are accurate. These techniques showed a similar level of specificity of 0.91 (0.76–1.0, 95% CI) sensitivity 0.90 (0.80–1.0, 95% CI and accuracy of 0.90 (P = 1.0). However, CTE has become a preferred mode for performing initial diagnosis of Crohn Disease due to its superior resolution and its potential to delineate segments of bowel involvement. This technique can accurately identify fistulas and strictures because of the clear formation of images. It is, however, essential to minimise the radiation dose in CTE for younger patients since they tend to undergo repeated scans due to the remitting and the chronic nature of the condition. MRE is also accurate and can be used as well with the advantage over CTE of not emitting radiation. From the review, it is now clear that both techniques can be used depending on local availability and disease location and severity, but MRE should be preferred especially in younger patients, because it is radiation free, due to the remitting nature of Crohn’s disease and therefore the need to perform repeat scans. Recommendation Further research should be conducted to identify a technique that can help radiologists identify crohn disease from other diseases. This is because, hyperenhancement of the segmental mucosa can also be present for other diseases other than Crohn disease including: backwash ileilitis, short gut syndrome luminal collapse, and mesenteric or portal vein clot. Thickening of the mural wall is also non-specific when it is seen in isolation and should thus be viewed in conjunction with mural hyperenhancement of the segments, just before the real diagnosis is made. A spasm that causes the collapse of loops of the bowel can be problematic because it is found early in CD and is associated with increased attenuation and thickening. Under these auspices, repeat scanning through the region of interest can be helpful. It is now recommended that a majority of examinations be done on 64 channel CT systems that give isotropic spatial resolution that permit reformatting of images in various planes, which improves visualization and thus diagnostic accuracy of CD. 6) References 1. Jensen M, Kjeldsen J, Rafaelsen S, Nathan, T. Diagnostic accuracies of MR enterography and CT enterography in symptomatic Crohns disease. Scandinavian Journal of Gastroenterology. 2011; 46:1449-1457. 2. Schmidt S, Guibal A, Meuwly J, Michetti P, Felly C, Meuli R. Acute complications of Crohns disease: comparison of multidetector-row computed tomographic enterography with magnetic resonance enterography. Digestion. 2010; 82: 229-238. 3. Siddiki HF, Fletcher J, Burton S, Huprich J, Hough D, Johnson C. Prospective comparison of state-of-the-art MR enterography and CT Enterography in small-bowel Crohns disease. American Journal of Roentgenology. 2009; 193: 113-121. 4. Fallis S, Murphy P, Sinha RH, Gladman L, Busby K, Sanders S . Magnetic resonance enterography in Crohns disease: a comparison with the findings at surgery. Colorectal Disease 2013; 15: 1273-1280. 5. Wold PB, Fletcher JG, Johnson CD, Sandborn WJ. Assessment of small bowel Crohn disease: noninvasive peroral CT enterography compared with other imaging methods and endoscopy-- feasibility study. Radiology 2003; 229:275-281. 6. Negaard A, Sandvik L, Berstad AE, et al. MRI of the small bowel with oral contrast or nasojejunal intubation in Crohn’s disease: randomized comparison of patient acceptance. Scand J Gastroenterol 2008 ;43:44-51 7. Hara AK, Leighton JA, Heigh RI, et al. Crohn disease of the small bowel: preliminary comparison among CT enterography, capsule endoscopy, small-bowel follow-through, and ileoscopy. Radiology 2006; 238:128-134. 8. Huprich JE, Fletcher JG, Alexander JA, Fidler JL, Burton SS, Mc- Cullough CH. Obscure gastrointestinal bleeding: evaluation with 64-section multiphase CT enterography--initial experience. Radiology 2008; 246:562-571. 9. Hakim FA, Alexander JA, Huprich JE, Grover M, Enders FT. CTenterography may identify small bowel tumors not detected by capsule endoscopy: eight years experience at Mayo Clinic Rochester. Dig Dis Sci. 2011; 56:2914-2919. 10. Hammer MR, Podberesky DJ, Dillman JR. Multidetector computed tomographic and magnetic resonance enterography in children: state of the art. Radiol Clin North Am 2013; 51:615-636. 11. Lee SS, Kim AY, Yang SK, et al. Crohn disease of the small bowel: comparison of CT enterography, MR enterography, and small-bowel follow-through as diagnostic techniques. Radiology 2009; 251:751-761. 12. Hara AK, Swartz PG. CT enterography of Crohn’s disease. Abdom Imaging 2009;34: 289-295. 13. Bodily KD, Fletcher JG, Solem CA, et al. Crohn Disease: mural attenuation and thickness at contrast-enhanced CT Enterography-- correlation with endoscopic and histologic findings of inflammation. Radiology 2006; 238:505-516. 14. Vogel J, da Luz Moreira A, Baker M, et al. CT enterography for Crohn’s disease: accurate preoperative diagnostic imaging. Dis Colon Rectum 2007; 50:1761-1769. 15. Gee MS, Nimkin K, Hsu M, et al. Prospective evaluation of MR enterography as the primary imaging modality for pediatric Crohn disease assessment. AJR Am J Roentgenol 2011; 197:224- 231. 16. Fletcher JG. CT enterography technique: theme and variations. Abdom Imaging 2009; 34:283-288. 17. Minordi LM, Vecchioli A, Mirk P, Bonomo L. CT enterography with polyethylene glycol solution vs CT enteroclysis in small bowel disease. Br J Radiol 2011; 84:112-119. 18. Berther R, Patak MA, Eckhardt B, Erturk SM, Zollikofer CL. Comparison of neutral oral contrast versus positive oral contrast medium in abdominal multidetector CT. Eur Radiol 2008; 18:1902-1909. 19. Megibow AJ, Babb JS, Hecht EM, et al. Evaluation of bowel distention and bowel wall appearance by using neutral oral contrast agent for multi-detector row CT. Radiology 2006; 238:87- 95. 20. Maglinte DD, Sandrasegaran K, Lappas JC, Chiorean M. CT Enteroclysis. Radiology 2007; 245:661-671. 21. Vandenbroucke F, Mortele KJ, Tatli S, et al. Noninvasive multidetector computed tomography enterography in patients with small-bowel Crohn’s disease: is a 40-second delay better than 70 seconds? Acta Radiol 2007; 48:1052-1060. 22. Kambadakone AR, Prakash P, Hahn PF, Sahani DV. Low-dose CT examinations in Crohn’s disease: impact on image quality, diagnostic performance, and radiation dose. AJR Am J Roentgenol 2010; 195:78-88. 23. Hara AK, Paden RG, Silva AC, Kujak JL, Lawder HJ, Pavlicek W. Iterative reconstruction technique for reducing body radiation dose at CT: feasibility study. AJR Am J Roentgenol 2009; 193: 764-771. 24. Ghetti C, Ortenzia O, Serreli G. CT iterative reconstruction in image space: a phantom study. Phys Med 2012; 28:161-165. 25. Lee SJ, Park SH, Kim AY, et al. A prospective comparison of standard-dose CT enterography and 50% reduced-dose CT enterography with and without noise reduction for evaluating Crohn disease. AJR Am J Roentgenol 2011; 197:50-57. 26. Craig O, O’Neill S, O’Neill F, et al. Diagnostic accuracy of computed tomography using lower doses of radiation for patients with Crohn’s disease. Clin Gastroenterol Hepatol 2012; 10:886- 892. 27. Kaza RK, Platt JF, Al-Hawary MM, Wasnik A, Liu PS, Pandya A. CT enterography at 80 kVp with adaptive statistical iterative reconstruction versus at 120 kVp with standard reconstruction: image quality, diagnostic adequacy, and dose reduction. AJR Am J Roentgenol 2012; 198:1084-1092. 28. Gee MS, Harisinghani MG. MRI in patients with inflammatory bowel disease. J Magn Reson Imaging 2011; 33:527-534. 29. Ippolito D, Invernizzi F, Galimberti S, Panelli MR, Sironi S. MR enterography with polyethylene glycol as oral contrast medium in the follow-up of patients with Crohn disease: comparison with CT enterography. Abdom Imaging 2010; 35:563-570. 30. G Fiorino, MD Bonafacio...S Danese. Prospective comparison of CT Enterography and MR Enterography for assessment of disease activity and complications in ileocolonic Crohn disease. 7) Tables Table 1: comparison between MR and CT (95 CI) at the patient level Author Parameters Technique Sensitivity Specificity Accuracy p-value Jensen et al Localization CTE 0.88(0.78-0.99) 0.88(0.68-1.0) 0.88 1.0 MRE 0.88(0.68-0.99) 0.88(0.68-1.0) 0.88 Hara et al Bowel wall thickening CTE 0.90(0.86-1.0) 0.91(0.76-1.0) 0.90 1.0 MRE 0.90(0.86-1.0) 0.91(0.76-1.0) 0.90 Bodily et al Bowel wall enhancement CTE 0.86(0.72—1.0) 1.00 0.93 1.0 MRE 0.81(0.65-0.97) 0.95(0.86-1.0) 0.86 Fiorino et al Enteroenteric fistulas CTE 0.20(0-0.55) 1.0 0.90 0.08 MRE 0.40(0-0.82) 0.94(0.87-1.0) 0.88 Hammer et a Strictures CTE 0.85(0.67-1.0) 1.0 0.91 0.04 MRE 0.92(0.79-1.0) 0.90(0.79-1.0) 0.95 Ippolito et al Abdominal nodes CTE 0.90(0.71-1.0) 1.0 0.97 1.0 MRE 0.80(0.55-1.0) 0.97(0.91-1.0) 0.93 Lee et al Perivisceral fat CTE 0.72(0.46-0.99) 1.0 0.93 0.31 MRE 0.90(0.73-1.0) 1.0 0.97 Table 2: scan parameters for CTE PARAMETER ENTERIC PHASE Scan delay 70sec Beam collimation 16x1.5 Gantry rotation time 0.75sec Table feed per gantry rotation 27mm Field of view 400mm Tube current(mA) 400mm Tube voltage(Kv) 140 Image plane Axial Section thickness(mm) 2mm Reconstruction interval(mm) 1mm Effective dose equivalent(mSv) 694mGy/cm Table 3: parameters of pulse sequences for MR enterography Parameters T2-weighted sequence axial planes T2-weighted sequence coronal planes T1-weighted fat sat before and after gadolinium T1 VIBE After contrast Slices 70 36 36 80 Thickness(mm) 5 5 5 4 FOV 450 500 500 450 TR 900 1000 6.86 5.16 TE 84 73 2.44 2.57 Flip angle 150 150 10 10 Matrix 256 256 256 256 8) Figures Fig. 1. Coronal CT enterography images using different types of neutral enteric contrast agents. CT enterography using polyethylene glycol (middle) and sorbitol (right) distends the small bowel effectively, while CT enterography using water (left) distends the small -bowel loops sub-optimally. Fig. 2. Axial CT enterography image in a 30-year-old woman with malabsorption and weight loss. (A, B) Axial and coronal reformatted CT images demonstrate a large ileocecal fistula (black arrow) arising from an ileal loop with Crohn involvement (white arrowheads; wall thickening, segmental hyperenhancement). The cecum (black arrowheads) is also inflamed and demonstrates wall thickening and stranding the pericolic fat. (C) A second coronal reformatted image shows an inflamed and decompressed terminal ileum (white arrow) superior to the often treated surgically, and this patient underwent distal ileal resection and right hemicolectomy. The patient’s fistula was confirmed by ileocolonoscopy and further surgery. Fig 3, left)27 year old man with suspected CD, middle)35 year old man with suspected CD and right), HASTE image of a 35-year old man. Read More