Combined Modalities May Improve Diagnosis, Treatment of Crohn's Disease

By Mike Bassett

PET/MR enterography and elastosonography (USE) can be used to optimize the imaging of Crohn's disease, according to presentations by German and Italian investigators during a Monday session.

Combined Use of PET, MRI Presents Advantages, Challenges

In a study looking at the use of PET/MR enterography for the assessment of inflammation in Crohn's disease, Thomas Lauenstein, MD, of the Evangelischen Krankenhaus Düsseldorf, described how MRI and PET could be combined to take advantage of the best features of each modality.

Thomas Lauenstein, MD

"We know that MRI is a very good tool for the assessment of bowel morphology, with a very high specificity for the identification of inflammatory bowel disease (IBD)," Dr. Lauenstein said. "On the other hand, PET, using FDG, is a very sensitive tool for the assessment of inflammation in general."

Therefore, the idea of combining the two "seems to be very appealing," he said. But, he also pointed out that combining the two modalities could produce contradictory results.

In the study, 50 patients with Crohn's disease underwent PET/MR enterography with FDG using an integrated PET/MR scanner. Using different segment-based cutoff values for PET, the researchers found a cutoff for SULmax of >1 was associated with the highest accuracy and sensitivity for the detection of inflammation.

Using this cutoff, PET proved to have high sensitivity in detecting inflammation (88 percent), while MRI had high specificity (96 percent). "The combination of PET and MRI in PET/MR enterography, in terms of sensitivity and specificity, proved to be a good compromise," Dr. Karsten J. Beiderwellen. MD, a sudy author, said. "However, in this patient cohort and using the proposed reading mechanism, [there was no] increase in diagnostic accuracy."

PET/MR enterography "combines the advantages of MR and PET — the high specificity of MR and the high sensitivity of PET," Dr. Lauenstein concluded. "However, at some point it also creates some disadvantages. In some situations it will be difficult to interpret the images because of contradictory data, and this is still challenging."

Elastosonography Shows Promise for
Crohn's Disease Management

Giuseppe Lo Re, MD

In another study presented Monday, Giuseppe Lo Re, MD, University of Palermo, Italy, and colleagues evaluated how USE can be used to discriminate between edematous inflammation and fibrotic change of the mesentery and bowel wall in patients with Crohn's disease.

With Crohn's disease "the distinction between inflammation and fibrosis can be tricky," said Dario Picone, MD, a study co-author. "But this distinction is very important because it impacts the management of patients." He pointed out that unlike some imaging tests used to identify bowel wall thickening, hyperperfusion, and active inflammation, USE is a noninvasive method of evaluating tissue stiffness, and has also been used to evaluate liver, breast and thyroid.

"Also, recent clinical studies on animals and humans have reported promising results for distinguishing inflamed from fibrotic bowel by using USE," Dr. Picone said.

In this study, 35 patients underwent MR enterography and real-time USE at the same time. Apparent diffusion coefficient values were calculated in the mesentery and bowel wall of patients with pathological ileum (a section of the small intestine) compared to those with normal ileum (the control group) and they were compared with USE color images (red/light green-normal, dark green-edematous, blue-fibrotic) and T2 signal in the same location.

"The results demonstrated that in the study group, the USE color-scale coding showed a color variation from blue to red in the fibrotic pattern of mesentery and bowel wall in 15 patients, and blue to green in the edematous pattern in 20 patients," Dr. Picone said. "Moreover the signal of the bowel wall and mesenteric fat was iso/hypointense on T2-weighted sequence in the fibrotic pattern and hyperintense in the edematous pattern. There was a significant diffusion in 18 patients with Crohn's disease in the active phase.

"Not only is USE noninvasive," Dr. Picone said, "but it improves the diagnostic accuracy in the evaluation of Crohn's disease in both detection and characterization of pattern changes, as well as in the guidance and evaluation in response to therapy."

"Evaluation of Crohn's disease through USE, DWI and T2 is a growing field, and many tools are available," Dr. Lo Re concluded. "USE is a quick, safe and noninvasive technique to confirm the presence of alteration of mesenteric fat and bowel wall in Crohn's disease, and also it allows the identification of the types of change."