Editors: Ioan Sporea, Roxana Șirli

Hepatic Elastography Using Ultrasound Waves

Special Offer (PDF + Printed Copy): US $84
Printed Copy: US $84
ISBN: 978-1-60805-557-9 (Print)
ISBN: 978-1-60805-463-3 (Online)
Year of Publication: 2012
DOI: 10.2174/97816080546331120101

Introduction

Some time ago, Schiano raised the question "To B or not to B", which means "To Biopsy or not to Biopsy" the liver for the evaluation of chronic hepatopathies. For a long period, liver biopsy (LB) was considered the "gold standard" for the evaluation of liver morphology. A major disadvantage of LB is its invasiveness: the risk of post-biopsy discomfort for patients and sometimes, for serious complications; also the lack of sensitivity to detect fibrosis, due to its heterogeneity; and the inability to obtain good quality fragments, adequate for pathological examination. In these conditions, the question is whether LB can be regarded as the "gold standard" for staging and grading chronic hepatitis in daily activity.

But what alternative can we propose for the evaluation of liver fibrosis at this moment? The answer is: non-invasive methods and the ultrasound elastographic ones presented in this volume.

Transient Elastography (FibroScan, Echosens) is a recognized method in many countries. Published papers and meta-analyses showed the value of this method for the diagnosis of liver cirrhosis (AUROC - 94%); for staging chronic HCV hepatitis (a cut-off value of 7.5 kPa differentiates F0–1 from F2–4 with 67% sensitivity, 87% specificity, 86% positive predictive value (PPV) and 68% negative predictive value (NPV), with a diagnostic accuracy of 76%; but also in HBV chronic infection, NASH, PBC, PBS).

Acoustic Radiation Force Impulse (ARFI) Elastography (Siemens S2000) is another elastographic methods with promising results (a meta-analysis showed that the mean diagnostic accuracy of ARFI expressed as AUROC was 0.88 for the diagnosis of significant fibrosis (F≥2), 0.91 for the diagnosis of severe fibrosis (F≥3), and 0.93 for the diagnosis of liver cirrhosis. In the subgroup of patients who underwent both ARFI and TE, the diagnostic accuracy of ARFI was comparable to TE for the diagnosis of significant and severe fibrosis, with a trend to be inferior for the diagnosis of cirrhosis. The future of liver fibrosis evaluation points towards non-invasive methods, decreasing dramatically the number of liver biopsies.

Studies have been published regarding the value of Real Time Elastography, performed for the first time with Hitachi systems (EUB-8500 and EUB-900), which uses an extended combined autocorrelation method to produce a real-time elasticity image by using a freehand approach to compress the tissues with the ultrasound transducer. The relative tissues’ elasticity is calculated and displayed as a color overlay on the conventional B-mode image. HiRT-E could be a promising method for the evaluation of liver fibrosis in chronic hepatopathies, but new methods of color code interpretation are needed to improve the accuracy, as well as a reference acquisition methodology.

ShearWave™ Elastography, the new "kid on the block", produces an image where true local tissue elasticity is displayed in a color map in "real time". Elasticity is displayed using a color coded image superimposed on a B-mode image. Stiffer tissues are coded in red and softer tissues in blue, with an image resolution of approximately 1mm. The true elasticity is assessed based on Shear wave propagation speed into the tissue. It is a very new method and only small studies were presented at international meetings.

Thus, having the alternative of noninvasive elastographic methods for the evaluation of liver fibrosis (maybe together with serum tests such as FibroMax) and knowing the low real life yield of liver biopsy (and the risk of complications), we can safely conclude that, for daily medical activity, liver biopsy can be avoided in the vast majority of cases.

This ebook presents an interesting set of chapters on the subject and is of good value to hepatologists interested in non invasive diagnostic methods for liver diseases.

Foreword

Since the introduction of the grey scale B-mode scanners, the liver has been the organ with the most extensive and fruitful applications of ultrasonography in the abdomen. Starting from the 80’s focal liver lesions became detectable even when small in size, targeted interventions were made possible with real-time guidance even at the bed-side and, slightly later, duplex Doppler ultrasound provided functional and not only morphological assessment of the liver vasculature and new exciting diagnosis were made possible. It should be acknowledged that the introduction of ultrasonography significantly contributed to the recognition of hepatology as an independent discipline. In the next 15 years refinements in ultrasound equipments were introduced by the industries, but no sustantial change in the diagnostic capabilities did really appear. This remained true until the early years 2000, which witnessed two revolutionary new ultrasound based techniques. One is real-time low acoustic pressure contrast enhanced ultrasound (CEUS), introduced into the market in 2002. This technique developed very rapidly and is now fully mature and applied in the daily practice worldwide with well established guidelines, such as those released by EFSUMB (European Federation of Societies for Ultrasound in Medicine and Biology). The second one is ultrasound elastography, which was first presented in the medical literature in 2003. Ultrasound elastography provides a functional assessment of the liver, informing on tissue elasticity and thus on the disease stage. This information is obtained with greatest ease, non invasively and very rapidly at the bedside. Accordingly, transient elastography has been recently incorporated into international guidelines for the management of chronic viral hepatitis. It has also applications in other conditions involving the liver, beside chronic hepatitis. While contrast enhanced ultrasound underwent technical improvements, but is substantially one single modality, elastography is somehow different and various modalities are available, requiring different examination techniques and providing slightly different clinical information. Most of these modalities have been introduced only in the very last few years and their properties are still poorly known to clinical ultrasonographers. Therefore, the eBook by Prof. Ioan Sporea on liver elastography is very timely presented and greatly desired. In fact the ongoing spread of the technical possibility to perform liver elastography must be paralleled by adequate knowledge of the clinicals information that can be obtained by each of the different modalities. Worth to remind that beyond the self standing transient elastography equipment, nowadays several ultrasound scanners can be implemented with various elastographic techniques, either based on shear wave or strain imaging modalities.

Reading the eBook will be an exciting time, with immediate applicability of the information into the daily clinical practice for anyone involved in the management of liver disease and the authors are to be commended for their efforts, based on long standing clinical and research expertise in this field.

Fabio Piscaglia, MD PhD,
University of Bologna
Italy
President EFSUMB


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