Equipment

Introduction

Over the past 5 years, the basic designs of the echoendoscope have not changed drastically—an attempt to create a “sleeker” look and feel while maintaining the same fundamental designs has been the overarching goal. Tremendous efforts in the ERCP arena have been made to mitigate infections linked to the elevator working channel. Similarly, and in due time, single-use disposable EUS accessories/scopes may infiltrate the market. Feel of the scope, tip articulation, and the corresponding ultrasound image will continue to differentiate the existing scope designs. However, there has been an attempt to consolidate the different processors in hopes of a “uniform” console. Elastography and strain measurements can be obtained with a “switch” button. Despite some differences, all consoles achieve a common end result—detailed ultrasound images at varying frequencies. Tissue acquisition has largely remained unchanged over the past 5 years—obtaining core biopsies from solid tissue has become the standard and norm. Needle-based probes via endoscopic ultrasound (EUS) have allowed detailed imaging of pancreatic cysts in hopes of distinguishing cyst morphology without the need for a biopsy. Radiofrequency ablation can be achieved using needle-based probes for cystic pancreatic neoplasms and small pancreatic neuroendocrine tumors. Although early in its infancy, EUS is building on the “endohepatology” platform with an opportunity to obtain portal pressures in addition to performing a liver biopsy at the same setting. As EUS-guided interventions have exponentially increased over the past 5 years, so have accessories including stents. Specific stents are now available allowing for EUS-guided gallbladder drainage, EUS-guided bile duct drainage, and EUS-guided hepaticogastrostomy and jejunostomies.

Radial scopes

At the inception of EUS technology, most endosonographers used a radial echoendoscope first, followed by a linear, when a fine-needle aspiration (FNA) was deemed necessary. With time, this practice has become mostly obsolete such that most endosonographers now proceed directly with the linear echoendoscope in virtually every case. The exceptions to this modus operandi would be for primary staging of esophageal, gastric, or rectal cancer and for further visualization and characterization of subepithelial lesions. All three manufacturers (Olympus, Center Valley, Pennsylvania; Pentax, Montvale, New Jersey; and Fujifilm, Wayne, New Jersey) offer forward-viewing gastroscopes with 360-degree, electronic, radial-array ultrasound transducers that generate high-resolution ultrasound images. The scope designs and processor capabilities are outlined in Table 2.1 . Current-generation electronic radial echoendoscopes use high-resolution videochip technology for high-resolution imaging. Virtually all current-generation radial scopes are electronic, in which the piezoelectric crystals are arranged in a band around the shaft of the endoscope perpendicular to the long axis of instrument, generating a 360-degree cross-sectional image. All three scopes are small diameter with a wide angulation range with a short distal end and allow for excellent maneuverability. There are subtle differences in the scope designs of these three instruments. The suction channel and optical sensor is displaced proximal to the transducer in the Olympus design ( Fig. 2.1 A). The suction channel and the optical sensor are placed at the distal tip of the Pentax echoendoscope (see Fig. 2.1 B). Fujifilm’s echoendoscope has a similar suction and optical sensor design while being equipped with the ultrasmall Super CCD (charged-couple device) chip images (see Fig. 2.1 C). All three scope designs incorporate a water-filled balloon around the transducer to achieve acoustic coupling. The most recent refinements in the design of the scopes by all three manufacturers have focused on ergonomics and enhanced maneuverability. The Olympus GF Type UE 160-AL5 is highly maneuverable, made possible by a wide angulation range to facilitate the approach to the duodenal bulb. The lens-clearing function keeps the endoscopic field of view clear at all times. The Pentax EG36-J10UR radial echoendoscope allows for 3-mm near-field endoscopic view with improved resolution due to new sensor image. Besides a more powerful tip angulation/deflection, the greatest reconfiguration with the J-series of scope has been the adoption to a single umbilical cable to reduce stress injury and keep better balance. The Fuji EG-580UR scope is ergonomically designed to enhance comfort with a rounded handle surface and a direct forward view for insertion into narrow lumens. The 190-degree bending capability of the EG-580 UR scope combined with a short rigid section supports manipulation in the duodenum and stomach.

Linear scopes

The same three manufacturers (Olympus, Pentax, and Fujifilm) offer linear echoendoscopes with slight differences in the “feel” of the echoendoscope, tip maneuverability, and the shape of the transducers, all of which impact the ultrasound image produced (see Table 2.1 ). For most endosonographers, these scopes represent the “workhorse” scopes in that they offer both diagnostic and therapeutic capabilities. The choice of scope is a matter of personal preference, but technically there are distinct differences in the scope design and the ensuing images ( Fig. 2.2 ). In general, the Olympus transducer has a more contoured, rounded tip, allowing for increased imaging of tissue anterior to the echoendoscope. Olympus continues to offer a forward-viewing, curved linear array (TGF-UC 180J) with a zero-degree working channel designed to perform interventional procedures ( Fig. 2.3 ). Features of this scope design include a short distal tip, straight working channel, extensive angulation, and an auxiliary water channel, obviating the need for a balloon. The therapeutic linear scopes (often designated with a “T”) have a larger working channel (3.7 mm with Olympus, 3.8 mm with Fuji, and 4.0 mm with Pentax), allowing for therapeutic interventions such as stent deployment for pseudocyst drainage and biliary decompression.

Pentax linear echoendoscopes incorporate a Hi-Compound feature, which combines frequency and spatial compounding, allowing an image to be scanned from multiple angles. The new J-series of linear echoendoscopes has several design modifications from its prior iteration, most notable of which is the single umbilical cable which reduces hand fatigue and ensures stability. The distal tip also has a smaller bending radius and a shorter rigid distal section length. A slim linear echoendoscope (EG34-J10U) has a smaller 2.8-mm instrument channel design and a new elevator design to allow for more needle control ( Fig. 2.4 ). The insertion tube is smaller in caliber as well (11.6 mm).

The Fujifilm EG-580UT curved linear echoendoscope has also undergone design modifications from its predecessor. The new G7 scope grip is ergonomically designed to provide pressure relief, helping minimize metacarpal fatigue. The scope has a smaller bending radius and short rigid section to enable easy access to target areas. This scope also is equipped with an elevator locking assist which enables flexible and subtle endoscopic operations, allowing for a stable puncture trajectory.

The newest technology in linear platform is an exciting development that builds upon a patented, disposable design that eliminates the infection safety concerns inherent in the legacy systems while attempting to broaden the market with reduced costs currently encumbering EUSs widespread adoption (EndoSound, Portland, Oregon). The EndoSound Vision System has received an FDA breakthrough technology designation—the merits of this system are that it can convert any standard endoscope into a fully functional EUS system (see Fig. 2.5 ). The transducer position can range from oblique to forward viewing by adjusting the orientation of the transducer such that interventional procedures can be performed.