MR, particularly True FISP, adds value to imaging small bowel

True FISP sequences improve the delineation of bowel wall thickening and peri-intestinal inflammation, compared with conventional sequences, according to German researchers.

Dr. Christian Hohl and colleagues from the RWTH Aachen University Hospital prospectively studied 30 patients with suspected inflammatory small bowel disease. Sequence protocols included 2D balanced FFE (True FISP), as well as the more conventional T1-weighted GE, T2-weighted TSE with fat suppression, and HASTE.

Three radiologists evaluated how well intestinal abnormalities were detected, as well as the degree of delineation of small-bowel wall thickening and the ileocecal valve. Image quality was assessed in terms of tissue contrast and susceptibility to artifacts.

The True FISP sequence had a 96% sensitivity in detecting small bowel abnormalities, compared with 88% to 95% with the other sequences. True FISP images revealed the best soft-tissue differentiation compared with all other performed MR sequences, Hohl said.

Delineation of bowel wall thickening, the ileocecal valve, and extraintestinal inflammatory reaction was significantly improved with True FISP. The difference between pre- and post-IV-contrast-enhanced True FISP sequences was not significant, he said.

"True FISP is a quick and robust sequence with high sensitivity in detecting inflammatory bowel disease," Hohl concluded.

In another study, Dr. Francesca Maccioni and colleagues at the University of Rome "La Sapienza" found good correlation with MR findings obtained with T1- and T2-weighted sequences and the corresponding pathologic specimens in patients with Crohn's disease of different severity.

Pathologic specimens were obtained in all 27 patients who underwent MRI and endoscopy or surgery. Patients received oral administration of superparamagnetic contrast, using T2-weighted plain and fat-suppressed sequences and gadolinium-enhanced T1-weighted sequences in the axial plane.

The researchers evaluated degree and pattern of wall signal, wall thickness, and abnormalities of perivisceral fat. T2 wall signal strongly related to wall gadolinium-enhancement (r: 0.84) and diffuse transmural inflammation at surgery in 14 patients, Maccioni said. Either layered or homogeneous patterns of gadolinium enhancement were observed in 11 patients with active disease, associated with submucosal edema or fibrosis at surgery.

Diffuse fibrosis with poor gadolinium enhancement and low T2 wall signal were found in five patients with inactive disease and diffuse fibrosis at surgery. In eight of 27 patients, active inflammation and fibrosis coexisted within the same loop at MR or surgery.

The group found strong correlation between gadolinium enhancement (r: 082), T2 wall signal (r: 0.85), and active or inactive disease, Maccioni said.

She concluded that MR offers reliable information on the wall affected by Crohn's disease, characterizing different pathologic conditions of the disease, including submucosal edema versus fibrosis and diffuse fibrosis or inflammation.