Primary Motility  Disorders of the  Esophagus
 The Esophageal
 Mucosa
 The
 Esophagogastric  Junction
 Barrett's
 Esophagus

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OESO©2015
 
Volume: Barrett's Esophagus
Chapter: Dysplasia
 

What can be expected from three-dimensional reconstruction of endosonographic images?

R. Fried (Basel)

The "gold standard" and only accurate method for diagnosing Barrett's esophagus is by endoscopy with biopsy. Biopsies may miss small focuses of dysplasia and thus lead to underestimation of the degree of changes in Barrett's mucosa by sampling error. An additional method for diagnosing dysplasia would be very helpful. One possibility is the use of staining methods which can delineate Barrett's mucosa and help to identify areas of dysplasia to be biopsied.

High-resolution endoluminal ultrasound (HRES) employing high-frequency probes (20-30 MHz) to improve detection of intramucosal adenocarcinoma in Barrett's esophagus or in staging early cancer is currently under investigation, and its role remains to be determined. HRES might also be able to show thickening of the esophageal mucosa associated with Barrett's metaplasia itself. Furthermore, it can be speculated that threedimensional reconstruction of endosonographic images may improve diagnosis in some instances. The technique allows the assessment of local tumor spread in previously unattainable scan planes and 3D views. Promising preliminary experience should encourage further exploration of this method.

Three dimentional endosonography

3D ultrasonographic images are usually generated from a series of digitized twodimensional ultrasound pictures acquired in a manner that enables registration of their relative spatial position. Such acquisition can be accomplished with different ultrasound probes, but in most cases of endosonography, a controlled pullback of radial-scanning probes has been applied. Digital ultrasound images are obtained by frame grabbing of analogue video recordings or by direct transmission from digital scanners. Acquisition of images is fast and prolongs endoscopic examination no more than 1-5 min. Dedicated software programs have been developed for 3D reconstruction and visualization, allowing interactive display and measurements. Several groups have presented prototype equipment for reconstruction of threedimensional images based on 2D images acquired with conventional endoscopic ultrasound (EUS) probes [1-3]. These systems allow reliable 3D reconstruction of endosonographic images. 3D reconstruction and simultaneous display of linear and radial images may facilitate interpretation of EUS images. Additional information may be gained by slicing the 3D-block at different angles. The unique potential of 3D reconstruction and thus 3D EUS lies in its ability to measure volume of tumors. There is very limited published information on the value of EUS and 3D EUS in the evaluation of Barrett's esophagus. Some questions remain to be answered:
1. Can HRES identify Barrett's metaplasia reliably?
2. Can HRES identify areas of dysplasia within Barrett's mucosa?
3. What can be expected from three-dimensional reconstruction of endosonographic images?

Results

In a study from Philadelphia, seventeen patients with documented Barrett's esophagus and 12 normal controls underwent endoscopy with HRES examination using a 20 MHz ultrasound transducer to evaluate for mucosal changes. HRES examinations were videotaped and reviewed by an unblinded investigator to identify criteria possibly diagnostic of Barrett's and then by a blinded investigator to test the validity of these criteria. Barrett's was diagnosed by HRES if the second hypoechoic layer appeared thicker than the first hyperechoic layer of the mucosa. Normal mucosa was defined as having a pencil-thin second hypoechoic layer on HRES. In this study, all 17 patients with Barrett's were correctly identified by HRES (sensitivity 100%). Ten of 12 controls were correctly identified as normal (specificity 86%). There was good correlation between HRES and pathologic diagnoses (r 0.86). The second hypoechoic layer was significantly thicker in Barrett's patients than in normal controls (p < 0.001). The authors concluded that HRES is a sensitive method for identifying Barrett's esophagus. However, dysplasia could not be identified by HRES in this study [4].

Methylene blue staining and EUS have been compared to determine their value in directing biopsies in patients with a history of Barrett's esophagus with low-grade dysplasia (LGD). Patients underwent radial EUS scanning to measure esophageal wall thickness, followed by endoscopy with methylene blue staining and biopsies. Mean esophageal wall thickness for squamous mucosa (2.3 0.2 mm), nondysplastic Barrett's (2.6 0.2 mm), and Barrett's with dysplasia (2.9 0.3 mm) were similar. Barrett's with LGD stained blue less frequently (52%) than nondysplastic Barrett's (74%; p < 0.05), but the positive predictive value for poor staining indicating dysplasia was 41%. In this study, EUS was not helpful in directing biopsies in these patients. [5].

The Charleston group has presented preliminary data of their experience with 3-D EUS in imaging Barrett's esophagus. This group found imaging of and evaluation of Barrett's esophagus subjectively better and prospective trials are ongoing [6].

Summary and conclusions

Endosonography is already the method of choice for local staging of tumors in the esophagus and plays an important role in the early detection of invasive carcinoma. High resolution probes can differentiate Barrett's metaplasia from normal mucosa and may detect and acccurately stage superficial carcinoma in the esophagus. 3D endosonography provides new possibilities for clinical imaging, but the impact on therapeutic strategies and clinical outcome has yet to be established. Three-dimensional endosonography is an attractive extension of conventional EUS and one of its most useful applications may be its ability to measure tumor volume. This feature may be important for assessment of the efficacy on non-operative treatment strategies of dysplasia in Barrett's mucosa and esophageal tumors. The clinical validity of 3D EUS, however, remains to be proven in prospective trials. Also technical developments such as algorithms for automatic volume rendering and easy-to-use equipment have to be awaited before the usefulness of this potentially attractive method can be assessed in a clinical setting.

References

1. Fried R, Beglinger C, Fischer H. Three-dimensional endoscopic ultrasonography: evaluation of a new desktop-based system. Gastrointest Endosc 1997;45:A 590.

2. Hunerbein M, Gretschel S, Ghadimi BM, Schlag PM. Three-dimensional endoscopic ultrasound of the esophagus. Preliminary experience. Surg Endosc 1997;11:991-994.

3. Molin S, Nesje LB, Gilja OH, Hausken T, Martens D, Odegaard S. 3D-endosonography in gastroenterology: methodology and clinical applications. Eur J Ultrasound 1999, 10:171-177.

4. Adrain AL, Ter HC, Cassidy MJ, Schiano TD, Liu JB, Miller LS. High-resolution endoluminal sonography is a sensitive modality for the identification of Barrett's metaplasia. Gastrointest Endosc 1997;46:147-151.

5. Gangarosa LM, Halter S, Mertz H. Methylene blue staining and endoscopic ultrasound evaluation of Barrett's esophagus with low-grade dysplasia. Dig Dis Sci 2000;45:225-229.

6. Matsuda K, Kim C, Hadzijahic N, et al. Preliminary experiences of three-dimensional endoscopic ultrasonography in the United States. Gastrointest Endosc 2000;51:A 3491.


Publication date: August 2003 OESO©2015