Magnetic resonance enteroclysis compared with conventional enteroclysis and computed tomography enteroclysis: a critically appraised topic

Recent advances in CT and MR technology, particularly the advent of multidetector CT (MDCT), the advent of rapidly changing gradients in industry standard MRI scanners, enabling ultrafast sequences, have led to an expansion in the role of cross sectional imaging in the investigation of small bowel disorders. We conducted an evidence-based review of MR enteroclysis (MRE) and how it performs in comparison to CT enteroclysis (CTE) and the gold standard of conventional enteroclysis (CE) for diagnosis of small bowel Crohn’s disease and small bowel neoplasia. We used the standard 5 step evidence-based medicine method of ask, search, appraise, apply and evaluate. We found 3 relevant level 1B studies, and one level 3B study. No studies evaluating MRE in small bowel neoplasia were found. MRE does not perform as well as CE in evaluation of fine mucosal detail, but the additional extraluminal detail, and absence of ionising radiation enhances its overall performance. It was not possible to establish the relative diagnostic performances of MRE and CTE from existing literature. CTE does involve patient irradiation. For patients in whom jejunal intubation and enteroclysis is considered to evaluate the small bowel, MRE should be considered the first-line investigation, local resources and expertise permitting.     

Magnetic Resonance Enteroclysis

MR enteroclysis (MRE) is an emerging technique for the evaluation of small intestinal diseases. Administration of an iso-osmotic water solution through a nasojejunal catheter can guarantee adequate luminal distention, and in combination with ultrafast sequences, such as single shot TSE, true FISP, HASTE and 3D FLASH, results in excellent anatomic demonstration of the small intestine. MR fluoroscopy can be performed during MRE examination to monitor the filling process and might be useful in studying low-grade stenosis or motility related disorders. MRE is a very promising technique for the detection and characterization of involved small bowel segments in patients with Crohn's disease while its diagnostic performance in disclosing lumen narrowing and extramural manifestations and complications of the disease is outstanding. Initial experience shows that MRE is very efficient in the diagnosis of small bowel tumors and can be used in the evaluation of small bowel obstruction.     

Internal fistulas in Crohn disease: magnetic resonance enteroclysis

Internal fistulas (IFs) and abscesses are the most common complications of Crohn disease (CD). To reliably diagnose and clearly distinguish inflammatory or fibrostenotic manifestations of CD from its complications is of paramount importance to appropriately guide therapeutic decisions. Magnetic resonance enteroclysis (MRE), a recently introduced technique for small bowel imaging, has proved a high efficacy in the depiction of luminal and extraluminal manifestations of CD and holds great promise as a powerful diagnostic tool in the comprehensive diagnostic workup of this disease. As of yet, the characteristic imaging appearance of IFs on MRE has not been described in detail. This article reviews the performance of conventional imaging techniques and the current potential of MRE in the depiction of IFs in CD. Typical imaging morphology and characteristic imaging findings of IFs on MRE are described in detail and a newly defined and highly indicative imaging finding, the “star-sign,” is presented and discussed.     

Crohn disease of the small bowel: MR enteroclysis versus conventional enteroclysis

Enteroclysis has been suggested as the technique of choice for the evaluation of Crohn disease of the small intestine. Adequate distention of the entire small bowel with barium suspension allows the radiologic demonstration of mucosal abnormalities and provides functional information by defining distensibility or fixation of the small bowel loops. The principal disadvantage of conventional enteroclysis is the limited indirect information on the state of the bowel wall and extramural extension of Crohn disease, and its effectiveness may be hindered owing to overlapping bowel loops. Moreover, the radiation dose administered to patients, mostly at a young age, should be considered. Magnetic resonance (MR) enteroclysis is an emerging technique for small bowel imaging and was introduced to overcome the limitations of conventional enteroclysis and MR cross-sectional imaging by combining the advantages of both into one technique. MR enteroclysis has the potential to change how the small bowel is assessed because of the functional information, soft tissue contrast, direct multiplanar imaging capabilities, and lack of ionizing radiation.     

MRI of the abdomen with positive oral contrast agents for the diagnosis of inflammatory small bowel disease

Magnetic resonance imaging (MRI) is being used more often in the evaluation of inflammatory bowel diseases. A prerequisite for adequate image quality is the oral application of contrast medium, which can be administered with different modalities. Positive and negative oral contrast media can be used; in terms of diagnostic efficacy, there appears to be no relevant differences between them. Sequences usually are acquired using breath-hold or respiration-triggered protocols. The underlying principle is visualization of circumscribed thickening of the intestinal wall, which shows a pathologic pattern of contrast medium uptake. The available data suggest that MRI is equally as effective as enteroclysis in the primary diagnosis of Crohn's disease and actually more sensitive in the detection of extraintestinal manifestations such as fistulae or abscesses. Supporters of the method predict that MRI will replace enteroclysis in the long term.     

MRI for small bowel diseases

The role of radiologic studies has been well established in the diagnosis and management of patients with small bowel diseases. While small bowel follow-through examination or enteroclysis is widely accepted as the primary imaging method for small bowel investigation, additional cross-sectional imaging studies are often required for an accurate diagnosis and the precise evaluation of the extraluminal disease. Since fast magnetic resonance imaging (MRI) sequences have become available, there is increasing interest in the use of MRI for small bowel evaluation, attributed to its inherent advantages such as the lack of radiation exposure, excellent soft tissue contrast, and direct multiplanar capabilities. In this article, we review the current techniques, clinical applications, and limitations of MRI for the evaluation of patients with small bowel diseases.     

Imaging for spine tumors and new applications

OBJECTIVES: Discuss intramedullary, intradural/extramedullary, and extradural spinal tumors including imaging characteristics with emphasis on MR and advances in treatment. METHODS: Literature and institutional review. RESULTS: Spinal tumors: intramedullary, intradural/extramedullary, and extradural, comprise a wide range of histological tumors with an even wider range of clinical symptoms and prognostic features. They are relatively rare and if left untreated, can cause serious neurological deficits and disability. An accurate diagnosis is therefore crucial in determining prognosis and directing therapy. Magnetic resonance imaging (MRI) has revolutionized the diagnosis of intraspinal tumors, allowing for early detection and improved anatomical localization. Magnetic resonance has also become an integral part in staging of both primary and metastatic neoplasms of the spine for guiding therapy and is an excellent modality for follow-up. Advances in MRI (perfusion and molecular imaging) may help refine and describe these neoplasms for accurate treatment and prognosis in the future. Surveillance protocols and role of magnetic resonance are not well established. CONCLUSIONS: Magnetic resonance plays an integral role in evaluation of spinal tumors with increasing role in staging and treatment.     

Magnetic Resonance Imaging of Abdominal Masses in the Pediatric Patient

Magnetic resonance (MR) plays a unique role in the diagnosis and management of pediatric abdominal masses. The "as low as reasonably achievable" (ALARA) radiation dose of CT is zero when substituted by MR. Whole body MR may also compete with PET imaging to stage abdominal tumors. Specific advantages of MR include determination of resectability of hepatic tumors using MRI and MRA; staging of neuroblastoma in the bone marrow, lymph nodes, liver, and spinal canal; response of bilateral Wilms tumor and nephroblastomatosis; detection of pelvic tumors with sagittal sectioning, and peritoneal tumors with contrast enhancement.     

智能响应性磁共振纳米分子成像探针研究进展

智能响应性纳米分子探针可以实现肿瘤靶向定位、快速响应、灵敏诊断、精确治疗疾病,这需要精确的成像来监测探针的分布和肿瘤的位置。近年来,磁共振成像(MRI)由于其具有高灵敏度,低背景噪声等特点受到了广泛的关注。磁共振成像作为临床上最为广泛和安全诊断方法之一,为疾病诊断和肿瘤靶向治疗提供影像学指导。研究者对智能响应性MR纳米分子成像探针检测如pH变化、酶活性、还原环境和乏氧等方面进行了深入的研究。这篇文章将对智能响应性磁共振纳米分子成像探针的成像最新研究进展进行综述。     

Small bowel Crohn’s disease: MR enteroclysis and capsule endoscopy compared to balloon-assisted enteroscopy

New modalities are available to visualize the small bowel in patients with Crohn’s disease (CD). The aim of this study was to compare the diagnostic yield of magnetic resonance enteroclysis (MRE) and capsule endoscopy (CE) to balloon-assisted enteroscopy (BAE) in patients with suspected or established CD of the small bowel. Consecutive, consenting patients first underwent MRE followed by CE and BAE. Patients with high-grade stenosis at MRE did not undergo CE. Reference standard for small bowel CD activity was a combination of BAE and an expert panel consensus diagnosis. Analysis included 38 patients, 27 (71%) females, mean age 36 (20–74) years, with suspected (n = 20) or established (n = 18) small bowel CD: 16 (42%) were diagnosed with active CD, and 13 (34%) by MRE with suspected high-grade stenosis, who consequently did not undergo CE. The reference standard defined high-grade stenosis in 10 (26%) patients. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value of MRE and CE for small bowel CD activity were 73 and 57%, 90 and 89%, 88 and 67%, and 78 and 84%, respectively. CE was complicated by capsule retention in one patient. MRE has a higher sensitivity and PPV than CE in small bowel CD. The use of CE is considerably limited by the high prevalence of stenotic lesions in these patients.     

Magnetic resonance imaging of cystic pancreatic lesions in adults: an update in current diagnostic features and management

Magnetic resonance (MR) imaging has become a widespread diagnostic solving tool for the detection and characterization of a large range of pancreatic cystic lesions. Benign and malignant cystic lesions of the pancreas including serous microcystic adenoma, mucinous cystic tumor, intraductal papillary mucinous tumor, solid pseudopapillary tumor, and also the less common lesions such as cystic endocrine tumors, cystic metastases, and lymphangiomas have suggestive MR imaging presentation that allows them to be differentiated from each other. Knowledge of MR imaging findings of cystic pancreatic lesions is critical to help suggest the diagnosis and chose the best therapeutic approach. The purpose of this review is to discuss and illustrate MR imaging features that are helpful for pancreatic cystic lesion detection and characterization and to provide an update in current MR imaging diagnostic features and management.     

Magnetic resonance imaging in gastroenterology: time to say good-bye to all that endoscopy?

Magnetic resonance imaging (MRI) has been described as the most important development in medical diagnosis since the discovery of the roentgen ray more than 100 years ago. The effectiveness of MRI has been extended to make it applicable in a wide variety of gastrointestinal disorders. The attention of gastroenterologists is currently focusing on pancreaticobiliary and bowel diseases. Magnetic resonance cholangiopancreatography (MRCP) has become a competitive alternative to diagnostic endoscopic retrograde cholangiopancreatography in a variety of hepatobiliary and pancreatic diseases. Magnetic resonance enteroscopy has the potential to become the preferable method for evaluating the entire small bowel; virtual colonoscopy, on the other hand, is far from the stage at which it could be promoted as a tool for general screening purposes in suspected colonic diseases. Its drawbacks include problems with standardization, implementation of the techniques in generalized settings, and patient acceptance.     

Technical challenges and clinical applications of magnetic resonance enteroclysis

With the advent of gradient systems the image quality of ultrafast pulse sequences, i.e., half Fourier acquisition single shot turbo spin echo (HASTE), true fast imaging with steady-state processing and fast low angle shot (FLASH), improved substantially and clinical applications including small bowel imaging became feasible. Within this context, magnetic resonance enteroclysis was developed as a comprehensive examination of the small bowel, providing luminal, transmural, and exoenteric diagnostic information of small bowel abnormalities. Clinical applications of magnetic resonance enteroclysis include diagnostic evaluation and follow-up of patients with inflammatory or neoplastic diseases and small bowel obstruction.     

小肠MR造影

MR小肠造影以其完全没有辐射、良好的软组织分辨率、能够清楚显示小肠腔内外情况而在临床上应用越来越多。作者介绍2种MR小肠造影方法:口服法MR小肠造影检查(MR enterography)和插管法MR小肠造影检查(MR enteroclysis),其中尤以口服法MR小肠造影简单、易行、无痛苦。用对比剂填充小肠、使小肠充分扩张是保证小肠造影取得成功的关键。作者经验是2.5%(等渗)甘露醇溶液为较理想的对比剂。简要归纳了一些常见小肠病变的MRI诊断要点并图示。     

磁共振成像技术在垂体瘤检出、诊断及疗效评估中的研究进展

随着磁共振成像技术的发展,垂体瘤的检出率越来越高,尤其是微小垂体瘤。磁共振成像技术可以检出垂体瘤,并可对其性质和临床治疗的反应及预后进行评估。不同的磁共振检查方法也会提高垂体瘤诊断率或对垂体瘤不同性质进行更好的评估,比如人工智能及影像组学方法可以探测肿瘤的软硬度,表观扩散系数值与肿瘤软硬度一致性具有相关性,磁化转移成像能够鉴别泌乳素瘤与无功能腺瘤,3.0 T较1.5 T磁共振对垂体瘤的检出率更高,新的磁共振成像技术如磁共振弹性成像可以确定垂体瘤软硬度,为手术提供重要的指标。同时,不同的检查技术也可以作为治疗方法效果的预测及疾病的预后。     

Magnetic resonance imaging of soft-tissue tumors in children

Magnetic resonance imaging (MRI) has become an important diagnostic tool in the detection and characterization and local anatomic staging of soft-tissue tumors in children. This article outlines some of the procedural issues unique to the pediatric population.     

Inflammatory bowel disease

This review summarizes important publications that have appeared during the last year dealing with imaging techniques and endoscopy, as well as the management of low-grade dysplasia and stenosis in inflammatory bowel disease. Magnetic resonance enteroclysis and capsule endoscopy are currently emerging as new imaging techniques for the small bowel in Crohn's disease. While magnetic resonance enteroclysis is, at least in Europe, increasingly being used as a reference method, the value of capsule endoscopy for the management of inflammatory bowel disease is still being evaluated. Chromoendoscopy is being studied in patients with long-lasting ulcerative colitis and may be a promising and sensitive technique for the diagnosis of dysplasia. However, there are conflicting data regarding the appropriate management when low-grade dysplasia is diagnosed in patients with ulcerative colitis. Endoscopic dilation can often be successfully carried out in cases of intestinal stenosis. The results of long-term follow-up studies indicate that several dilation procedures are often necessary and that a relatively high percentage of patients still have to undergo surgery.     

Magnetic resonance elastography: Non-invasive mapping of tissue elasticity

Magnetic resonance elastography (MRE) is a phase-contrast-based MRI imaging technique that can directly visualize and quantitatively measure propagating acoustic strain waves in tissue-like materials subjected to harmonic mechanical excitation. The data acquired allows the calculation of local quantitative values of shear modulus and the generation of images that depict tissue elasticity or stiffness. This is significant because palpation, a physical examination that assesses the stiffness of tissue, can be an effective method of detecting tumors, but is restricted to parts of the body that are accessible to the physician's hand. MRE shows promise as a potential technique for 'palpation by imaging', with possible applications in tumor detection (particularly in breast, liver, kidney and prostate), characterization of disease, and assessment of rehabilitation (particularly in muscle). We describe MRE in the context of other recent techniques for imaging elasticity, discuss the processing algorithms for elasticity reconstruction and the issues and assumptions they involve, and present recent ex vivo and in vivo results.     

Prostate cancer detection: magnetic resonance (MR) spectroscopic imaging

Magnetic resonance spectroscopic imaging (MRSI) represents a noninvasive technique to extend the diagnostic evaluation of prostatic cancer, beyond the morphologic information provided by MR imaging throughout the detection of cellular metabolites (choline and citrate). MRSI combined with the anatomical information provided by MRI can improve the assessment cancer location and extent within the prostate, extracapsular spread and cancer aggressiveness; both before and after treatment. We review the performance of MRI with MRSI and the role in the detection, localization, staging and management of the patient pre- and posttherapy for prostate cancer.     

磁共振全身弥散成像对胃肠道恶性肿瘤的术后随访价值

目的探讨3.0 T全身磁共振成像的技术对于胃肠道恶性肿瘤性疾病的术后随访价值。材料与方法对19例术后随访的胃肠道恶性肿瘤患者行WBMRI(DWI+T2WI),后处理平台为GE ADW4.6工作站。Functool工具拼接横断面弥散图像,得到HD-MIP图像、黑白反转图像(类"PET"图像)及伪彩色图像;Pasting工具拼接冠状面T2加权图像,得到全身冠状面T2加权图像,再经图像融合得到类"PET-MR"图像。结果 19例患者(其中胃弥漫性大B细胞淋巴瘤2例,胃癌8例,结肠癌7例,直肠癌2例)均获得图像质量良好的全身磁共振图像。发现恶性转移性病例6例,阳性率约32%。结论使用头颈联合线圈及体线圈接收方法可以改善中心频率漂移现象,得到符合诊断需要的全身弥散图像。3.0T MR全身弥散成像可清晰显示胃肠道恶性肿瘤的转移灶,对胃肠道恶性肿瘤的术后随访和辅助诊断具有重要价值。