Image Fusion Involving Real-Time Transabdominal or Endoscopic Ultrasound for Gastrointestinal Malignancies: Review of Current and Future Applications

Abstract

Image fusion of CT, MRI, and PET with endoscopic ultrasound and transabdominal ultrasound can be promising for GI malignancies as it has the potential to allow for a more precise lesion characterization with higher accuracy in tumor detection, staging, and interventional/image guidance. We conducted a literature review to identify the current possibilities of real-time image fusion involving US with a focus on clinical applications in the management of GI malignancies. Liver applications have been the most extensively investigated, either in experimental or commercially available systems. Real-time US fusion imaging of the liver is gaining more acceptance as it enables further diagnosis and interventional therapy of focal liver lesions that are difficult to visualize using conventional B-mode ultrasound. Clinical studies on EUS guided image fusion, to date, are limited. EUS-CT image fusion allowed for easier navigation and profiling of the target tumor and/or surrounding anatomical structure. Image fusion techniques encompassing multiple imaging modalities appear to be feasible and have been observed to increase visualization accuracy during interventional and diagnostic applications.

Keywords: GI malignancies; endoscopic ultrasound; image fusion; transabdominal ultrasound.

Figure 1

A typical FI procedure flow. The pre-procedure CT images are used to reconstruct a virtual 3D map of the patient. The FI software (Triger^TM) is used to superimpose the EM sensor locations onto the 3D model. The live EUS images are integrated with the 3D model to find the clinical target.

Figure 2

(a) Custom-made pig organ model. A custom-made pig organ model was used to test the image fusion software. The design of the model included: overtube; stomach; “pseudocyst”; “gallbladder” (filled with “stones”); liver; (b) Image fusion (EUS/CT) testing. EUS–CT fusion in real time showing the 3D reconstruction of the segmented CT with a phantom “gallbladder with stones inside”, “pseudocyst”, and liver (C). The oblique section shows the co-registered large-field CT, showing all 3 organs, and narrow EUS image, showing only the pseudocyst (A and B).