Abstract

Alexander R. Margulis
S/M Radiology, University of California, USA

Conventional barium and most fluoroscopic studies have almost disappeared in the industrial world in spite of their high quality in expert hands.

Few fluoroscopic studies persist. These are: studies involving assessment of motility, gastro-esophageal reflux,. aspiration, exclusion of anastomotic leaks etc. Small bowel barium examinations are still being performed, some before ingestion of disposable endoscopic camera capsules to exclude partial small bowel obstruction.

Enteroclysis, a most precise and elegant examination, although often performed at some specialized centers, is disappearing. This is most likely due to the lack of skilled examiners and problems associated with conscious sedation in outpatient settings. CT and MR enteroclysis have many advantages but share the drawbacks of the conventional approach. They also present logistical problems.

Cross sectional modalities
Multi-row detector CT (MDCT) offers 3D studies with an enormous amount of data, rapidly replacing most conventional imaging studies of the alimentary tube.

Although MR can provide studies of equal quality to the best CT, and does not involve ionizing radiation, it is rarely used for alimentary tube examinations because it is more costly and studies last longer.

CT colonoscopy (CTC) offers many advantages, but present cleansing approaches are too onerous. Although MR virtual colonoscopy is an excellent approach, it is rarely used.

Computer aided detection (CAD) is advancing to become routine and thus facilitating interpretation.

Virtual gastroscopy (VG) with MDCT equipment, is an examination in use in several centers in the US and Europe. CTC and VG are not sensitive in the diagnosing flat lesions.

Virtual enterography is being developed mostly in Europe.

Future approaches
PET/CT appears to be the best approach for distinguishing benign from malignant masses in the alimentary tube. It also promises to be able to predict which colonic adenomatous polyps have the potential of becoming malignant. It can also identify metastatic lymph nodes whether enlarged or of normal size, which neither CT nor MRI can do.

PET/MRI will be available shortly as large imaging equipment companies are racing to bring it to market. It will have advantages and drawbacks when compared to PET/CT.

Optical Coherence Tomography, OCT, an approach based on computer interferometry of reflected laser infrared rays, promises virtual biopsy with images offering histologic resolution. It is of particular value in the diagnosis of dysplasia in Barrett’s esophagus.

Other optical approaches have advanced to the point that it is possible to obtain CT of cell nuclei identifying the earliest changes of cancer. It shows as a disarray of the chromatin material, actin.

Molecular imaging of the alimentary tube presently performed mostly on animals, promises to reveal basic biological processes leading to the pre-clinical discovery of disease. New PET/CT specific tracers for abnormal metabolism, and new specific contrast media for MR are the future. High cost is the greatest obstacle in bringing these materials to clinical use.

The future of imaging the gastrointestinal tube is spectacular.