High-frequency catheter endoscopic ultrasonography
- Maurits J Wiersema, MD
Maurits J Wiersema, MD
- Clinical Assistant Professor of Medicine
- Indiana University School of Medicine
Endoscopic ultrasound (EUS) has an important role in the evaluation of benign and malignant gastrointestinal diseases [1-8]. Echoendoscopes operate from 5 to 20 MHz, permitting a spectrum of depth of penetration and image resolution. Higher frequencies provide higher resolution but less penetration, while lower frequencies provide higher penetration but lower resolution.
Advancements in ultrasound technology have led to the development of small caliber ultrasound catheters (maximum diameter 2.6 mm) that can be passed through the biopsy channel of a standard endoscope . These miniprobes operate across a range of frequencies (12 to 30 MHz), providing a greater image resolution (0.07 to 0.18 mm) than standard EUS scopes as well as improved accuracy for studying small or superficial lesions of the gastrointestinal tract [9,10].
This topic review describes the technical characteristics of the commercially available high-frequency ultrasound (HFUS) catheters and the experience with their use in a variety of conditions.
HFUS catheters can be broadly classified by their working mechanism into mechanical and electronic catheters.
Mechanical catheters — Mechanical catheters have a single ultrasound transducer located at the tip of the catheter, which is rotated by a cable and transmits the signal from the transducer to the ultrasound processor. A flexible housing protects the cable and the transducer from damage. When rotating, the ultrasound transducer produces a 360-degree image, perpendicular to the longitudinal axis of the HFUS catheter. Certain models of HFUS mechanical catheters can be inserted over a guidewire, facilitating examination of the bile and pancreas ducts. These probes have been modified so that linear imaging is also possible with subsequent three-dimensional reconstruction.
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- Mechanical catheters
- Electronic catheters
- EXAMINATION TECHNIQUES
- Condom technique
- Balloon technique
- Immersion technique
- NORMAL GASTROINTESTINAL WALL ANATOMY
- CLINICAL INDICATIONS
- Esophageal carcinoma
- - Barrett's esophagus
- Gastric cancer
- Colorectal cancer
- Pancreatic and biliary diseases
- Submucosal lesions
- SUMMARY AND RECOMMENDATIONS