Indications and limitations of endoscopic ultrasound elastography for evaluation of focal pancreatic lesions

Background and study aim: Endoscopic-ultrasound-guided elastography (EUS-elastography) is a recently introduced imaging procedure that distinguishes tissues on the basis of their specific consistency. The aim of this prospective study was to investigate the role of this new technique in the characterization and differentiation of focal pancreatic lesions.

Patients and methods: This prospective study enrolled 70 patients with unclassified solid lesions of the pancreas and 10 controls with a healthy pancreas. In all patients elastography recordings were compared with cytology/histology findings as the gold standard.

Results: Adequate EUS-elastography of the pancreas was performed in all healthy controls but in only 56 % of patients with solid pancreatic lesions. The main limitation of elastographic image acquisition was incomplete delineation of the border of lesions greater than 35 mm in diameter (39 %) or of lesions at some distance from the transducer (10 %). Elastographic recordings were also hampered by the fact that the surrounding tissue, which is used as an internal reference standard for strain calculation, was insufficiently displayed in the case of larger lesions. The reduced ratio of target to surrounding tissue resulted in the formation of color artifacts and in impaired reproducibility. In contrast, the majority of lesions smaller than 35 mm in diameter were adequately and reproducibly evaluated by EUS-elastography (91 %). The clinical use for differential diagnosis, however, seems limited, since strain images from all kinds of pancreatic masses were found to be harder than the surrounding tissues, irrespective of the underlying nature of the lesion (i. e., malignant vs. benign). EUS-elastography predicted the nature of pancreatic lesions with poor diagnostic sensitivity (41 %), specificity (53 %), and accuracy (45 %).

Conclusion: EUS-elastography of the pancreas has the potential to obtain some complementary information that would improve tissue characterization. Its clinical utility, however, remains questionable, and it seems unlikely that the information provided will obviate the necessity of obtaining tissue samples for confirmation of a final pathologic diagnosis.

References

• 1 Caletti G, Fusaroli P, Bocus P. Endoscopic ultrasonography.  Digestion. 1998;  59 509-529
• 2 Tamerisa R, Irisawa A, Bhutani M S. Endoscopic ultrasound in the diagnosis, staging, and management of gastrointestinal and adjacent malignancies.  Med Clin North Am. 2005;  89 139-158
• 3 Noh K W, Pungpapong S, Raimondo M. Role of endosonography in non-malignant pancreatic diseases.  World J Gastroenterol. 2007;  13 165-169
• 4 Lachter J, Cooperman J J, Shiller M. et al . The impact of endoscopic ultrasonography on the management of suspected pancreatic cancer – a comprehensive longitudinal continuous evaluation.  Pancreas. 2007;  35 130-134
• 5 Dietrich C F, Ignee A, Braden B. et al . Improved differentiation of pancreatic tumors using contrast-enhanced endoscopic ultrasound.  Clin Gastroenterol Hepatol. 2008;  6 590-597
• 6 Saftoiu A, Vilman P. Endoscopic ultrasound elastography – a new imaging technique for the visualization of tissue elasticity distribution.  J Gastrointest Liver Dis. 2006;  15 161-165
• 7 Itoh A, Ueno E, Tohno E. et al . Breast disease: clinical application of US elastography for diagnosis.  Radiology. 2006;  239 341-350
• 8 Thomas A, Fischer T, Frey H. et al . Real-time elastography – an advanced method of ultrasound: first results in 108 patients with breast lesions.  Ultrasound Obstet Gynecol. 2006;  28 335-340
• 9 Lyshchik A, Higashi T, Asato R. et al . Thyroid gland tumor diagnosis at US elastography.  Radiology. 2005;  237 202-211
• 10 Thomas A, Kummel S, Gemeinhardt O, Fischer T. Real-time sonoelastography of the cervix: tissue elasticity of the normal and abnormal cervix.  Acad Radiol. 2007;  14 193-200
• 11 Cochlin D L, Ganatra R H, Griffiths D F. Elastography in the detection of prostatic cancer.  Clin Radiol. 2002;  57 1014-1020
• 12 Friedrich-Rust M, Ong M F, Herrmann E. et al . Real-time elastography for noninvasive assessment of liver fibrosis in chronic viral hepatitis.  AJR Am J Roentgenol. 2007;  188 758-764
• 13 Fritscher-Ravens A. Blue clouds and green clouds: virtual biopsy via EUS elastography?.  Endoscopy. 2006;  38 416-417
• 14 Micames C G, Gress F G. EUS elastography: a step ahead?.  Gastrointest Endosc. 2007;  65 979-981
• 15 Saftoiu A, Vilmann P, Hassan H, Gorunescu F. Analysis of endoscopic ultrasound elastography used for characterisation and differentiation of benign and malignant lymph nodes.  Ultraschall Med. 2006;  27 535-542
• 16 Saftoiu A, Vilmann P, Ciurea T. et al . Dynamic analysis of endoscopic ultrasound elastography used for differentiation of chronic pancreatitis and pancreatic cancer.  Gastrointest Endosc. 2007;  65 Abstract 194
• 17 Giovannini M, Hookey L C, Bories E. et al . Endoscopic ultrasound elastography: the first step towards virtual biopsy? Preliminary results in 49 patients.  Endoscopy. 2006;  38 344-348
• 18 Janssen J, Schlorer E, Greiner L. EUS elastography of the pancreas: feasibility and pattern description of the normal pancreas, chronic pancreatitis, and focal pancreatic lesions.  Gastrointest Endosc. 2007;  65 971-978
• 19 Frey H, Ignee A, Dietrich C F. Elastography, a new ultrasound based imaging modality.  Endosk Heute. 2006;  19 117-120. DOI: 10.1055/s-2006 – 933 534
• 20 Janssen J, Dietrich C F, Will U, Greiner L. Endosonographic elastography in the diagnosis of mediastinal lymph nodes.  Endoscopy. 2007;  39 952-957
• 21 Graham P, Bull B. Approximate standard errors and confidence intervals for indices of positive and negative agreement.  J Clin Epidemiol. 1998;  51 763-771
• 22 Hirooka Y, Itoh A, Kawashima H. et al . Preliminary results in the diagnosis of the early stage chronic pancreatitis using EUS-elastography.  Gastrointest Endosc. 2006;  63 Abstract 258
• 23 Deprez P H, Yeung C-P R, Weynand B. et al . Contrast EUS versus EUS sono-elastography in the differentiation of atypical pancreatic masses.  Gastrointest Endosc. 2007;  65 Abstract 103
• 24 Jacobson B C. Pressed for an answer: has elastography finally come to EUS?.  Gastrointest Endosc. 2007;  66 301-303
• 25 Hirooka Y, Itoh A, Hashimoto S. et al . Utility of EUS elastography in the diagnosis of pancreatic disease.  Gastrointest Endosc. 2005;  61 Abstract 282