New Technology – Combined Use of 3D Contrast Enhanced Endoscopic Ultrasound Techniques

Introduction

While 3D sonography has become established in gynecology, abdominal applications have been mainly restricted to case reports and few studies. However, recent advances in computer technology have supported the development of new systems with motion detection methods and image registration algorithms – making it possible to acquire 3D data without position sensors, before and after administration of contrast enhancing agents. We reported on the first use of 3D imaging of the liver and spleen under real time conditions, using contrast enhanced phase inversion imaging with low mechanical index [1].

The advantages of 3D procedures are clearer visualization of anatomy and topography, visualization of the extension of changes into surrounding tissue with special emphasis on the reconstructed coronary plane, measurement of volumes (also non-symmetrical) or pathologic changes, improved diagnoses (quality of results) through analysis of the third plane, higher quality of results through imaging the surrounding structures with landmarks (quality management), improved examination quality through planning and performing an optimized image acquisition and image documentation, improved acceptance by the referring physician through clearer visualization and therefore fewer follow-up examinations, and demonstration of findings with reference to any desired scan plane (e.g. as part of the daily findings discussion).

Compared to other tomographical imaging methods (e.g. computed tomography, magnetic resonance imaging) ultrasound technology suffers from insufficiently clear documentation of the findings. The single images from real-time sonography resemble the pieces of a mosaic and are assembled into a complex three-dimensional representation of the anatomy in its environmental context, and then recognized in space, solely through the powers of imagination of the investigator. However, an observer not directly participating in the examination will have difficulty sharing in this subjective visualization. Surgeons want a realistic and detailed survey image, where the change in relation to the environment can be evaluated (e.g. segment localization of liver tumors through visualization of the connections to the portal vein branches and hepatic veins).

In recent years contrast enhanced endoscopic ultrasound has been introduced [2] and improved to push the boundries of conventional endoscopic ultrasound. Last year first systems of low mechanical index endoscopic ultrasound features became commercially available [3]. This was the starting point of the contrast enhanced low mechanical index endosonography (CELMI EUS) which allows to visualize contrast enhancing effects in microvessels.

The technique developed first in clinical medicine as a method to discriminate chronic pancreatitis from pancreatic cancer [4] also using the contrast enhancing effect for Doppler spectrum analysis [5]. The investigation proved useful and is still performed in colour Doppler mode with high mechanical index endosonography (CEHMI EUS). In this method, the contrast enhancer (usually Sonovue®) acts as a Doppler flow enhancer for analysis of macrovessels [6].

We report on the latest development in endoscopic ultrasound the combination of CEHMI EUS and CELMI EUS with a 3D reconstruction, which allows unique insights in the vessel structure of lesions.

Case Report

A 68 year old woman was sent to clarify an unusual pancreatic mass, detected by CT scan. The woman’s medical history revealed renal cancer operation of the left kidney 15 years ago and hypertensive nephropathia. Therefore, computed tomography (CT) scan was performed without contrast enhancer. The suspected lesion was localized in the pancreatic tail with a size of 3 x 2.5 cm - not visible 5 years ago.

Using endoscopic ultrasound, the lesion could be clearly shown with a sharp demarcation to the pancreatic tail ([Fig. 1]). Unenhanced color Doppler endosonography revealed a high vascularisation of the lesion. Using contrast enhanced low mechanical endoscopic ultrasound, a clear contrast enhancing effect of the neoplastic tissue could be observed ([Fig. 2]). The vessel structure of the unenhanced colour Doppler endosonography could be impressively shown in 3D endoscopic ultrasound ([Fig. 3]). Furthermore the whole tumor was visible using the combination of CELMI EUS with 3D reconstruction ([Fig. 4]). According to those results, the working diagnosis of a late onset of renal cancer metastasis in the pancreatic tail was made.

Fig. 1 Original unenhanced view of the lesion in the pancreatic tail using endoscopic Doppler ultrasound. The rich vascularisation of the tumour is not as impressive as in the 3D reconstruction due to longer scanning time in 3 D mode.

Fig. 2 Clearly hyperenhanced tumour after injection of contrast enhancer in low MI mode. The machine is already set up in 3D data acquiring mode.

Fig. 3 3D Color Doppler reconstruction of the rich vascularisation of a renal cancer metastasis in the pancreatic tail. The normal surrounding tissue is shown in gray colors.

Fig. 4 3D reconstruction of the metastatic lesion after demarcation with help of contrast enhanced low mechanical index endosonography. The normal surrounding pancreatic tissue does not take up the contrast enhancer and therefore remained not visible in the picture.

No further lesions could be shown in further CT and MRI scans and the woman could be successfully operated on a second time with confirmation of the diagnosis.

Conclusions

The combination of 3D reconstruction with enhanced and unenhancend endoscopic ultrasound seems to be a feasible method to give the investigator and the referring doctor new insights into the anatomy and outer borders of a neoplastic lesion.

The advantage of the new method is the small learning curve and the possible combination with any endoscopic ultrasound technique.

The disadvantage seems to be the interrupted investigation due to the data aquiring period (in total between 15 and 20 sec.). This means that the advantage of real time contrast enhanced ultrasound has to be compromised. So far using this tool we have to inject two contrast vials, the first time for the dynamic analysis of the lesion and the second time for requiring data for the 3D reconstruction.

Developing the low mechanical index endosonography into better scanning quality might outcast the disadvantages and lower the costs. Real time 3D scanner, as already in use in gynecological ultrasound, could improve the method even further.

References

1. Dietrich CF. [3D real time contrast enhanced ultrasonography,a new technique]. Rofo 2002; 174(2):160-163.

2. Dietrich CF, Ignee A, Frey H. Contrast-enhanced endoscopic ultrasound with low mechanical index: a new technique. Z Gastroenterol 2005; 43(11):1219-1223.

3. Dietrich CF. Contrast-enhanced low mechanical index endoscopic ultrasound (CELMI-EUS). Endoscopy 2009; 41 Suppl 2:E43-E44.

4. Hocke M, Schulze E, Gottschalk P, Topalidis T, Dietrich CF. Contrast-enhanced endoscopic ultrasound in discrimination between focal pancreatitis and pancreatic cancer. World J Gastroenterol 2006; 12(2):246-250.

5. Hocke M, Ignee A, Topalidis T, Stallmach A, Dietrich CF. Contrast-enhanced endosonographic Doppler spectrum analysis is helpful in discrimination between focal chronic pancreatitis and pancreatic cancer. Pancreas 2007; 35(3):286-288.

6. Hocke M, Schmidt C, Zimmer B, Topalidis T, Dietrich CF, Stallmach A. [Contrast enhanced endosonography for improving differential diagnosis between chronic pancreatitis and pancreatic cancer]. Dtsch Med Wochenschr 2008; 133(38):1888-1892.

Michael Hocke, Christoph F Dietrich [e-mail]