[Evaluation of intestinal hyperaemia in inflamed bowel by high resolution Contrast Harmonic Imaging (CHI)]

Intestinal hyperaemia is a sign of active disease in the inflamed intestine which can be detected by Doppler sonography. This technique, however, can be jeopardized by tissue motion artefacts (peristalsis), and intramural enteric vessel perfusion may be below the detection threshold. Visualisation of vessels by Contrast Harmonic Imaging (CHI) at a low Mechanical Index (low MI) is not restricted by the limitations mentioned above. Contrast Harmonic Imaging at low MI of the intestinal wall has not yet been described with high frequency probes. We therefore evaluated the validity of this method for detecting hyperaemia of the intestinal wall.

CHI at low MI was performed with a 7.5 MHz ultrasound probe in 12 patients with signs of an inflamed intestine. The contrast agent BR 1 (4.8 ml) was injected intravenously. Contrast enhancement was quantified by analysing gray scale values before and after injection of BR 1 in regions of interest within the submucosal layer.

At about 15 sec. after injection of BR 1, arterial inflow of the contrast agent with visualisation of the feeding mesenteric vessels and intense contrast of the submucosal lamina could be observed. An increase of the gray scale values within the ROI after contrast enhancement was detected in all patients.

We have shown that CHI at low MI is technically feasible for the demonstration of increased intestinal perfusion in inflammatory bowel disease by using a high resolution ultrasound probe. One possible method of quantifying the contrast enhancement is the gray scale analysis of pixels in defined regions of interest within the submucosal layer.