High-resolution endoluminal sonography in gastroenterology

Ultrasound capsule endoscopy: sounding out the future

Video capsule endoscopy (VCE) has been of immense benefit in the diagnosis and management of gastrointestinal (GI) disorders since its introduction in 2001. However, it suffers from a number of well recognized deficiencies. Amongst these is the limited capability of white light imaging, which is restricted to analysis of the mucosal surface. Current capsule endoscopes are dependent on visual manifestation of disease and limited in regards to transmural imaging and detection of deeper pathology. Ultrasound capsule endoscopy (USCE) has the potential to overcome surface only imaging and provide transmural scans of the GI tract. The integration of high frequency microultrasound (µUS) into capsule endoscopy would allow high resolution transmural images and provide a means of both qualitative and quantitative assessment of the bowel wall. Quantitative ultrasound (QUS) can provide data in an objective and measurable manner, potentially reducing lengthy interpretation times by incorporation into an automated diagnostic process. The research described here is focused on the development of USCE and other complementary diagnostic and therapeutic modalities. Presently investigations have entered a preclinical phase with laboratory investigations running concurrently.

IRM et exploration du tube digestif — Aspects techniques et perspectives d’évolution

Barium enema remains the reference method for the detection of morphological intraluminal alterations of the bowel. Optimal filling of intestinal loops allows high diagnostic sensitivity and specificity. US, CT and MRI are useful diagnostic procedures in the evaluation of mural and extramural alterations. In recent years, MR-enteroclysis and MR colonography have been developed, both enable the evaluation of luminal, extraluminal and mural alterations of the bowel. While these modalities provide good imaging evaluation of the bowel, visualization of the different layers, as seen on US, is still not available. Use of high resolution endoluminal coil on MR could improve mural evaluation of bowel to differentiate inflammatory diseases and provide accurate TNM classification of tumoral lesion with minimally invasive procedure.

In vitro rat colonic wall imaging with MR endoluminal coil: feasibility study and histologic correlations

RATIONALE AND OBJECTIVES

Despite improvements, spatial resolution and image quality with routine surface coils are too limited when detailed information about the gastrointestinal layers is requested. The objective of our feasibility study was to evaluate the potential of a dedicated endoluminal coil to depict different layers of the colonic wall in an in vitro small animal model.

MATERIALS AND METHODS

A single-loop coil (40 mm length, 5 mm width) was built using IC (printed circuit) technology. The coil was tuned to a frequency of 63.7 MHz and matched at 50 Omega for this frequency. The coil was housed in a biocompatible tube with an outer diameter of 18 F (6 mm). Ten segments of rat colon, surgically excised 5 hours earlier, were completely immersed in an isotonic solution. The coil was introduced through the lumen of colonic specimens. MRI experiments were performed on a 1.5 T MR Symphony system (Siemens, Erlangen, Germany) using imaging protocol combining high-resolution 2D Flash, fast imaging employing steady-state acquisition (TrueFISP), turbo spin echo (TSE), and 3D FastLow-Angle Shot (FLASH) sequences. After a 24-hour period of fixation in 10% formalin, colonic specimens were excised along the longitudinal axis for histologic analysis.

RESULTS

The endoluminal coil provided high SNR allowing for the visualization of different layers of rat colonic walls. All the performed sequences made it possible to identify at least two different layers. On T1-weighted gradient-echo sequences, the mucosa was of high signal intensity, whereas the muscle layers had an intermediate to low signal intensity. The signal intensity of different wall layers was similar in different sequences. Histologic analysis identified three main layers.

CONCLUSION

These results are well correlated with histologic findings and suggest that endoluminal MR imaging may have potential for accurate staging of colonic tumor or inflammatory process.

The role of endoluminal ultrasonography in urology: current perspectives

Endoluminal ultrasonography (ELUS) is a noninvasive diagnostic technique used in urology to image tubular structures of the urinary tract. Through advancements in technology, modern ELUS is able to create three-dimensional images, which provide valuable clinical information for the diagnosis and treatment of urologic disorders. The efficiency and accuracy of this technology is confirmed through validation studies using human and animal models. Although a relatively new method, the clinical application of this technique holds great promise in the field of endourology. The technology, advantages, limitations, validation studies, clinical applications, and future of ELUS are explored through this comprehensive review of current urologic literature.

ENDOSCOPIC ULTRASOUND INSTRUMENTATION, APPLICATIONS IN HUMANS, AND POTENTIAL VETERINARY APPLICATIONS

Endoluminal scanning under endoscopic guidance, or endoscopic ultrasonography (EUS), has become the most significant advance for imaging the gastrointestinal (GI) tract wall and contiguous organs in the past 20 years. It was originally designed to overcome the limitations in humans to imaging the abdominal organs transabdominally, such as large penetration depths and GI air. This imaging modality provides detailed images of pathological processes both within and outside of the GI wall since a high-frequency transducer can be brought into close proximity with the target regions. It has found most success in humans for the staging of lung, gastric, and esophageal cancer, the detection of both lymphatic and hepatic metastases, and diagnosis of pancreatitis and pancreatic cancer, as well as achieving an important role in interventional and therapeutic procedures. The EUS examination can be performed to examine both the thorax and abdomen in animals when both conventional transthoracic or transabdominal ultrasound are inadequate due to intervening air, bone, large penetration depths, or obesity. The echoendoscope is similar to a conventional endoscope but has an ultrasound transducer at its tip. Both radial and linear multifrequency scanners are available. Linear scanners allow fine-needle aspiration (FNA) of the bowel wall or extraluminal structures. Transducer coupling is either by direct mucosal contact or by inflation of a water-filled balloon surrounding the transducer. Current thoracic applications for EUS in veterinary medicine include examination of the mediastinum, bronchial lymph nodes, esophagus, and pulmonary lesions as well as FNA of pulmonary masses. Abdominal applications include examination of both pancreatic limbs and the liver, including portosystemic shunts, detection of lymphadenomegaly, and examination of the gastric wall, duodenum, and jejunum. Other potential applications in dogs and cats include tumor staging and intrapelvic ultrasound.

Food allergy and intolerance: response to intestinal provocation monitored by endosonography

OBJECTIVE

Objective assessment of adverse reactions to food is a long-felt want. We report our preliminary experience with a new endosonographic allergen provocation test.

METHODS

Twenty patients were examined, seven patients having food allergy and 13 having food intolerance. The duodenal mucosa was challenged with allergen extracts via a nasoduodenal tube. The responses were recorded using a miniprobe for endosonography through the tube. Thereafter, intestinal lavage was performed by giving 2 l PEG solution containing micro Ci (51)CrEDTA. The gut lavage fluid and urine for 5 h were collected.

RESULTS

Increased mucosal thickness in response to provocation was recorded in 11 patients, but not more often or pronounced in the allergic than in the intolerance group. Interestingly, increased mucosal thickness associated with a new echogenic layer was seen in two patients and a sustained duodenal contraction, lasting 15-20 min associated with pain, in another two. Intestinal permeability and inflammatory mediators were not significantly different in the two groups.

CONCLUSION

In patients with self-reported adverse reactions to food abnormal responses to duodenal provocation may be recognised by endosonography. However, neither endosonography nor intestinal permeability or faecal calprotectin responses were able to distinguish between food allergy and intolerance. Sustained duodenal contractions in response to food might be a cause of abdominal pain.