RC 101 - Assessing inflammation and fibrosis in Crohn's disease
Diagnostic imaging plays a major role in the decision-making process of patients affected by Crohn’s disease (CD), both at the time of diagnosis and throughout the course of the disease. One of the most relevant clinical problems in current management of patients affected by CD is represented by the assessment of inflammation and fibrosis. The two entities should not be considered separately, since they coexist in most of the patients. A correct quantification of the prevalent entity is extremely important, since the patient should be referred for medical therapy if inflammation predominates, whereas either endoscopic dilatation of the stricture or surgery becomes necessary if fibrosis is prevalent. Cross-sectional imaging (CSI) modalities, including ultrasound (US), multidetector-CT (MDCT) and MR imaging (MRI), can provide useful information, particularly for inflammation, less for fibrosis. Contrast-enhanced US (CEUS) has been shown to correlate with disease activity and severity, in comparison with endoscopic score of severity. Data about CEUS and fibrosis are controversial, although a quantitative data analysis seems the most valuable approach. Very promising results have been recently obtained with US elastography. Current data with MDCT highly correlate with disease activity and severity, but not with fibrosis. Dual-energy analysis might improve MDCT performances. MRI correlates not only with inflammation, but also with fibrosis, particularly if multiparametric analysis is performed. This analysis includes the evaluation of pattern of enhancement, late enhancement and the analysis of T2 signal. In the next future, other MR techniques are under evaluation, such as T1 mapping and magnetization transfer contrast.
1. To learn about CEUS technique, including imaging acquisition and data post-processing.
2. To become familiar with US elastography, particularly with those techniques useful in the assessment of the small bowel.
3. To understand potential advantages and possible limitations of CEUS and elastography in the assessment of inflammation and fibrosis in Crohn’s disease.
Crohn’s disease (CD) is a chronic transmural inflammatory disease of the gastrointestinal tract which can be assessed by ultrasound. Unenhanced ultrasound may evaluate the localization and the length of the affected intestinal segments and may suggest the presence of mural fibrosis based on the layered appearance of the bowel wall. Contrast-enhanced ultrasound of the bowel is performed by wide-band transducers including the microbubble resonance frequency. Contrast-enhanced ultrasound has become an important imaging modality in patients with CD for the grading of disease activity, the differentiation between small bowel stricture due to inflammation or mural fibrosis, and for the assessment of the response to specific pharmacologic therapy. New dedicated software packages allow the accurate quantification of the enhancement within the small bowel wall after microbubble contrast agent injection to obtain different kinetic parameters - percentage of the maximal enhancement, the time-to-the peak enhancement, and the area under the time-intensity curve - which may differentiate mural inflammation from fibrosis and responders from non-responders to the specific pharmacologic therapy. The main advantage of contrast-enhanced ultrasound in the real-time assessment of the perfusion of the bowel wall but the scan is necessarily limited to one single loop each time. US real-time elastography can be considered an additional tool to complete US assessment of the bowel wall in patients with CD. US real-time elastography allows to assess the bowel wall stiffness to distinguish acute inflammation from fibrosis in patients with CD and increases the diagnostic confidence if compared to contrast-enhanced US alone.
1. To understand basic principles of spectral imaging, including data post-processing.
2. To appreciate the strengths and limitations of spectral imaging in the abdomen.
3. To learn about advantages and possible limitations of spectral imaging in the assessment of inflammation and fibrosis in Crohn’s disease.
Many aspects of managing patients suffering from Crohn’s disease (CD) remain unclear. It is still unknown which factors trigger disease chronicity, and which promote the development of intestinal fibrosis. On the other hand, anti-inflammatory treatment such as steroids, immunosuppressants and anti-TNF-alpha have serious side effects; moreover, the decision for surgical treatment is also difficult. Because of many factors that influence the disease management, there is a strong need for a reliable tool of inflammatory activity and fibrosis assessment. Recently, apart from MR enterography (MRE), CT enterography (CTE) is being used to detect and monitor intestinal inflammation. Bowel wall and mesenteric changes such as mural thickening and hyperenhancement, increased attenuation of perienteric fat, and mesenteric hyperaemia have been reported to indicate CD activity. Recently introduced dual-energy CT modality allows creating monochromatic spectral images at energy levels ranging from 40 to 140 keV and water and iodine-based material decomposition with quantitative analysis. This method has already been applied in abdominal imaging, e.g. urinary stones, renal cell carcinoma and hepatocellular carcinoma. There are also preliminary reports about implementation of spectral imaging in CTE technique for an objective assessment of Crohn’s disease activity and coexistent fibrosis. The aim of this lecture is to give an overview of the CTE bowel inflammatory changes, and the possible advantages of spectral imaging for assessing activity and fibrosis in CD.
1. To understand basic principles of DWI applied to Crohn’s disease.
2. To learn about MR-perfusion protocols and data analysis.
3. To learn about advantages and possible limitations of MRI in the assessment of inflammation and fibrosis in Crohn’s disease.
Crohn's disease (CD) is a relapsing and remitting inflammatory condition of the GI tract. Clinical management essentially resolves around use of immunosuppressive medication and surgery. Crucial to clinical decision making is assessment of the underlying inflammatory activity, those with active inflammatory disease tend to undergo immunosuppressive therapy whereas those with fibrosis may benefit from surgical resection. In reality, however, inflammation and fibrosis tend to coexist. Both DWI and perfusion are abnormal in CD. However, the relationship between both DWI and contrast enhancement and the histopathological phenotype is complex. Whist data suggest active Crohn's disease tends to result in restricted DWI, the balance between increased inflammatory infiltrate and tissue oedema influences ADC values and recent data using surgical resection specimens suggest fibrosis also leads to restricted diffusion. Similarly, whilst perfusion tends to increase in active CD, tissue angiogenesis which increases in chronic disease also affects contrast uptake. Enhancement patterns may help radiologist grade activity. For example, a layered enhancement pattern is reported in active disease, but again overlap with fibrosis is seen. Recent data suggest delayed contrast-enhanced sequences at around 7 minutes can help quantify fibrosis. This presentation will describe clinical protocols used to acquire DWI and perfusion imaging in CD and present the data as to their utility in clinical practice.