Introduction

The fundamental designs of the echoendoscopes have not changed drastically since 2010. Differing feel of the scope, tip articulation, and the corresponding ultrasound image inherently distinguish the main scopes available. Current echoendoscopes have overcome the technical challenges from their predecessors that were saddled with limitations in maneuverability and endoscopic views. The console of each processor is designed slightly differently, yet they all achieve a common end result—detailed ultrasound images at varying frequencies. Knowledge of basic ultrasound terminology and physics is imperative regardless of the processor and scope manufacturing. However, since 2015, the burgeoning field of tissue acquisition via different needle designs, including the capabilities for core biopsies, has heralded a “dawn of a new era.” In fact, many have coined the phrase “optical biopsy” to describe imaging obtained from a needle-based probe via EUS. A corollary to the needle-based diagnostic capabilities is the emerging therapeutic options available with needle-based radiofrequency ablation (RFA) for cysts and small neuroendocrine tumors. Finally, this chapter will summarize the excitement surrounding tissue-apposing luminal stents for pseudocyst drainage, biliary drainage, and creating hepaticogastrostomy—all solely through the EUS scope.

Radial Scopes

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. 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. 2.1A ). The suction channel and the optical sensor are placed at the distal tip of the Pentax echoendoscope (see Fig. 2.1B ). 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. 2.1C ). All three scope designs incorporate a water-filled balloon around the transducer to achieve acoustic coupling. 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 submucosal lesions.

(A) GF-UE160-AL5 is a 360-degree radial array scanning endoscope. (B) Pentax EG-3670URK is a 360-degree radial array scanning endoscope. (C) Fujifilm EG-530UR2 Ultrasonic Radial Scanning Endoscope is a 360-degree radial array scanning endoscope.

[A] Image courtesy of Olympus America, Center Valley, Pennsylvania; [B] Image courtesy of Pentax Medical, Montvale, New Jersey; [C] Image courtesy of Fujifilm, Wayne, New Jersey.

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. Pentax linear echoendoscopes incorporate a Hi-Compound feature, which combines frequency and spatial compounding, allowing an image to be scanned from multiple angles. Fujifilm echoendoscopes combine easier maneuverability with similar therapeutic options; at present, there is only one linear echoendoscope option with a unique processor platform. An elevator is present on each of these scopes, allowing the operator to vary the angle at which the needle enters the tissue. Even without using the elevator, the angle of the needle puncture into the tissue/lesion differs. The therapeutic linear scopes (often designated with a “T”) have a larger working channel (3.8 mm with Fujifilm and Pentax), allowing for therapeutic interventions such as stent deployment for pseudocyst drainage and biliary decompression.

(A) Olympus GF-UCT curved linear array. (B) Pentax EG-3870UTK curved linear array. (C) Fujifilm EG-530UT2 Ultrasonic Convex Scanning Endoscope.

[A] Image courtesy of Olympus America, Center Valley, Pennsylvania; [B] Image courtesy of Pentax Medical, Montvale, New Jersey; [C] Image courtesy of Fujifilm, Wayne, New Jersey.

Pentax Medical has developed a newer slim linear echoendoscope (EG-3270UK), which has a smaller 2.8-mm instrument channel design and a new elevator design to allow for more needle control ( Fig. 2.3 ). The insertion tube is smaller in caliber as well (10.8 mm). This device recently received US Food and Drug Administration (FDA) approval for its use in the United States.

Pentax EG-3270UK slim curved linear array.

Image courtesy of Pentax Medical, Mississauga, Ontario, Canada.

Olympus has introduced a forward-viewing, curved linear array (TGF-UC 180J) with a zero-degree working channel designed to perform interventional procedures ( Fig. 2.4 ). 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.

TGF-UC180J forward-viewing curved linear array for interventional procedures with a zero degree working channel.

Image courtesy of Olympus America, Center Valley, Pennsylvania.

Processors

Each echoendoscope requires a distinct and unique ultrasound processor for imaging; the cost implications and the hindrance that this imposes is implicit. Table 2.1 summarizes the compatible processors with each scope. There are unique features and enhancements to the designs of the processors that worth highlighting. Fujifilm promotes its second-generation scopes that use small Super CCD chip technology which offer bright, vivid, high-resolution endoscopic images with the integration of ZONE Sonography and Sound Speed Correction technologies to deliver ultrasound images. The new compact Sonart Su-1 processor can be used for both its radial and linear echoendoscopes ( Fig. 2.5 ). Fundamental imaging is obtained at 5, 7.5, 10, and 12 MHz with tissue harmonic imaging at 8 and 10MHz. Compound harmonic imaging, sound speed imaging and elastography are added features.

Fujifilm SU-1 Ultrasonic Processor for both radial and linear echoendoscopes.

Image courtesy of Fujifilm, Wayne, New Jersey.

Pentax uses a Hitachi Ultrasound platform with fundamental imaging frequencies at 5, 6, 7.5, 9, and 10 MHz. Noblus serves as their compact processor, touted to be no larger than a laptop ( Fig. 2.6A ). The HI VISION Preirus ultrasound platform combines Hi-Compound imaging with Hi-Resolution (see Fig. 2.6B ). These technologies report enhanced organ boundary visualization and reduced angle-dependent artifacts.

(A) Noblus processor. (B) HI VISION Preirus ultrasound processor.

Images courtesy of Pentax Medical, Montvale, New Jersey.

Olympus offers two distinct ultrasound platforms, the Hitachi-Aloka ProSound F75 and EU-ME2 (and Premier Plus) ( Fig. 2.7A and B). The ProSound distinguishes itself by offering a sleek, ergonomically engineered console and screen that can be adjusted horizontally and vertically per the endosonographer’s wishes. Imaging frequencies are at 5, 6, 7.5, and 10 MHz with the ProSound and up to 12 MHz with the EU-ME2 and Premier Plus. A contrast echo feature with this device enables the display of microvascularization of blood vessels to the capillary level. Of the many enhanced ultrasound physics capabilities, the eFlow feature that enables increased sensitivity to flow at low velocities and in small vessels is attractive and useful, particularly when assessing for the ideal path of needle puncture. The EU-ME2 Premier Plus represents the world’s only ultrasound processor for endoscopic and bronchoscopic applications. The versatility and universal capabilities are attractive if the same processor needs to be shared between pulmonologists and gastroenterologists performing endobronchial and endoscopic ultrasound respectively. In addition, this processor is backward compatible, meaning that the processor can be used with older/current Olympus EUS scopes while being forward compatible as newer (future/forward) EUS scopes are introduced. This processor provides image quality equal to a larger radiology processor while maintaining its compact design.

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