Endoscopy 1999; 31(4): 329-332
DOI: 10.1055/s-1999-21
Editorial
Georg Thieme Verlag Stuttgart · New York

How Far Have We Come With Ultrasound Miniprobes?

 A. Chak
  • Dept. of Medicine, University Hospitals of Cleveland, Cleveland, Ohio, USA
Weitere Informationen

Publikationsverlauf

Publikationsdatum:
31. Dezember 1999 (online)

Endoluminal ultrasonography incorporates the basic principles of physics, the technical accomplishments of modern engineering, the behavior of biological tissue, and the art of medicine. One of the inescapable physical properties of ultrasound is that while a higher frequency produces higher image resolution, it is at the cost of reduced tissue penetration. Correspondingly, medical applications depend on the frequency of the imaging instrument. Low frequencies are required for imaging large or distant lesions, whereas high frequencies are better suited for identifying subtle changes in small nearby lesions. The physical properties of the crystals used for transducers are such that small transducers can only produce high frequencies. Miniprobes are ultrasound catheters with diameters of approximately 2 - 3 mm, designed to pass through the accessory channel of a diagnostic endoscope. They generally incorporate transducers with frequencies of 12 MHz or higher. In contrast, echo endoscopes are usually operated at a frequency of 7.5 MHz. Not only is the imaging depth and resolution of these two types of endoluminal instrument different, but the focal length of miniprobes is typically in the 5 - 10 mm range, whereas the focal length of echo endoscopes is in the 20 - 30 mm range. Thus, although there is overlap, the medical applications of miniprobes differ from those of their counterpart, the echo endoscope.

Endoscopic ultrasonography (EUS) using echo endoscopes is a well-established part of gastrointestinal endoscopic practice. However, EUS is one of the most difficult and cumbersome endoscopic procedures, since the instruments are relatively heavy and their tip is long and rigid. When small lesions are scanned with echo endoscopes, it is difficult to ascertain whether the ultrasound transducer is in the plane of the lesion. Perhaps the most significant limitation of these instruments is the fact that the examination of stenotic malignancies is often incomplete. The performance of dilation in order to complete the examination is not without risk [[1]]. Miniprobes are an attractive and technically easy to use alternative to echo endoscopes. Miniprobes can be positioned near small lesions, and the lesions can be imaged with great confidence. The probes can also be used to traverse and image stenotic lesions.

Mechanical as well as phased-array scanning probes that scan in either the linear or the radial direction have been developed. Most reports have used rotational mechanical sector-scanning miniprobes. Applications of miniprobes can be placed in three categories: a) unique applications; b) applications in which miniprobes are preferable to echo endoscopes; and c) applications in which miniprobes are an alternative to echo endoscopes.

References

  • 1 Van Dam J, Rice TW, Catalano MF, et al. High-grade malignant stricture is predictive of esophageal tumor stage.  Cancer. 1993;  71 2910-7
  • 2 Tamada K, Ido K, Ueno N, et al. Assessment of the course and variations of the hepatic artery in bile duct cancer by intraductal ultrasonography.  Gastrointest Endosc. 1996;  44 249-56
  • 3 Tamada K, Ido K, Ueno N, et al. Assessment of hepatic artery invasion by bile duct cancer using intraductal ultrasonography.  Endoscopy. 1995;  27 579-83
  • 4 Tamada K, Ido K, Ueno N, et al. Assessment of portal vein invasion by bile duct cancer using intraductal ultrasonography.  Endoscopy. 1995;  27 573-8
  • 5 Itoh A, Goto H, Naitoh Y, et al. Intraductal ultrasonography in diagnosing tumor extension of cancer of the papilla of Vater.  Gastrointest Endosc. 1997;  45 251-60
  • 6 Hamada S, Kazuya A, Chijiiwa Y, et al. Preoperative staging of colorectal cancer by a 15 MHz ultrasound miniprobe.  Surgery. 1998;  123 264-9
  • 7 Yoshida M, Tsukamoto Y, Niwa Y, et al. Endoscopic assessment of invasion of colorectal tumors with a new high-frequency ultrasound probe.  Gastrointest Endosc. 1995;  41 587-92
  • 8 Saitoh Y, Obara T, Einami K, et al. Efficacy of high-frequency ultrasound probes for the preoperative staging of invasion depth in flat and depressed colorectal tumors.  Gastrointest Endosc. 1996;  44 34-9
  • 9 Shimizu S, Iso A, Tada M, Kawai K. Endoscopic ultrasonography in ulcerative colitis.  Dig Endosc. 1994;  6 3-6
  • 10 Tsuga K, Haruma K, Fujimura J, et al. Evaluation of the colorectal wall in normal subjects and patients with ulcerative colitis using an ultrasonic catheter probe.  Gastrointest Endosc. 1998;  48 477-84.
  • 11 Shimizu S, Tada M, Kawai K. Endoscopic ultrasonography in inflammatory bowel diseases.  Gastrointest Endosc Clin N Am. 1995;  5 851-9
  • 12 Adrain AL, Ter HC, Cassidy MJ, et al. High resolution endoluminal sonography is a sensitive modality for the identification of Barrett's metaplasia.  Gastrointest Endosc. 1997;  46 147-51
  • 13 Miller LS, Liu JB, Barbarevech CA, et al. High-resolution endoluminal sonography in achalasia.  Gastrointest Endosc. 1995;  42 545-9
  • 14 Miller LS, Liu JB, Klenn PJ, et al. Endoluminal ultrasonography of the distal esophagus in systemic sclerosis.  Gastroenterology. 1993;  105 31-9
  • 15 Schiano TD, Adrian AL, Cassidy MJ, et al. Use of high-resolution endoluminal ultrasonography to measure radius and wall thickness of esophageal varices.  Hepatology. 1996;  24 552-5
  • 16 Akahoshi K, Chijiiwa Y, Hamada S, et al. Pretreatment staging of endoscopically early gastric cancer with a 15 MHz ultrasound catheter probe.  Gastrointest Endosc. 1998;  48 470-6
  • 17 Akahoshi K, Chijiiwa Y, Tanaka M, et al. Endosonography probe-guided endoscopic mucosal resection of gastric neoplasms.  Gastrointest Endosc. 1995;  42 248-52
  • 18 Yanai H, Fujimura H, Suzumi M, et al. Delineation of the gastric muscularis mucosae and assessment of depth of invasion of early gastric cancer using a 20-megahertz endoscopic ultrasound probe.  Gastrointest Endosc. 1993;  39 505-12
  • 19 Yanai H, Yoshida T, Harada T, et al. Endoscopic ultrasonography of superficial esophageal cancers using a thin ultrasound probe system equipped with switchable radial and linear scanning modes.  Gastrointest Endosc. 1996;  44 578-82
  • 20 Yanai H, Tada M, Karita M, Okita K. Diagnostic utility of 20-megahertz linear endoscopic ultrasonography in early gastric cancer.  Gastrointest Endosc. 1996;  44 29-33
  • 21 Akahoshi K, Chijiiwa Y, Hamada S, et al. Endoscopic ultrasonography: a promising method for assessing the prospects of endoscopic mucosal resection in early gastric cancer.  Endoscopy. 1997;  29 614-9
  • 22 Yasuda K. Development and clinical use of ultrasonic probes.  Endoscopy. 1994;  26 816-7
  • 23 Saisho H, Sai K, Tsuyuguchi T, et al. A new small probe for ultrasound imaging via conventional endoscope.  Gastrointest Endosc. 1995;  41 141-5
  • 24 Maruta S, Tsukamoto Y, Niwa Y, et al. Evaluation of upper gastrointestinal tumors with a new endoscopic ultrasound probe.  Gastrointest Endosc. 1994;  40 603-8
  • 25 Chak A, Canto M, Stevens PD, et al. Clinical applications of a new through-the-scope ultrasound probe: prospective comparison with an ultrasound endoscope.  Gastrointest Endosc. 1997;  45 291-5
  • 26 Binmoeller KF, Seifert H, Seitz U, et al. Ultrasonic esophagoprobe for TNM staging of highly stenosing esophageal carcinoma.  Gastrointest Endosc. 1995;  41 547-52
  • 27 Grimm H. Endoscopic ultrasonography with the esophagoprobe.  Endoscopy. 1994;  26 818-21
  • 28 Chak A, Soweid A, Hoffman B, et al. Clinical implications of endoluminal ultrasonography using through-the-scope catheter probes.  Gastrointest Endosc. 1998;  48 485-90
  • 29 Menzel J, Hoepffner N, Nottberg H, et al. Preoperative staging of esophageal carcinoma - miniprobe sonography versus conventional endoscopic ultrasound: a prospective, histopathologically controlled study.  Endoscopy. 1999;  31 291-7

Amitabh ChakM.D. 

Dept. of Medicine

University Hospitals of Cleveland

Cleveland, Ohio

USA

Telefon: + 1-216-844-8011

eMail: axc22@po.cwru.edu