Broad Band ultrasound imaging using cMUT – BBMUT

The ultrasonic examination of the liver disease is frequently associated with the injection of a contrast agent. However, contrast imaging methods currently available are limited, mainly because of the large number of patients for whom harmonic imaging does not improve detection of tumors. It is then necessary to propose new techniques dedicated to the contrast agents and especially their nonlinear properties.
The BBMUT project involves the design of a cMUT probe whose specifications will be adapted to the examination of the liver. Existing techniques and innovative techniques based on Chirp or composite signal emission will be implemented and the results compared with those obtained using an equivalent piezoelectric probe.
The properties of cMUT probes will also be used to provide a native image that has improved contrast without degrading the resolution. The large bandwidth and high directivity of cMUT probes encourage the implementation of spatial and frequency compounding techniques.
Furthermore, we propose to develop an ultrasonic method for characterizing tissue structures adapted to liver, particularly by estimating the size of the scatterers to show that the estimated parameters related to the structures are correlated with liver histology. A quantitative measurement of the nonlinearity parameter is also proposed. A pre-clinical validation will quantify the diagnostic relevance of the proposed approaches.

CREANUIS is a software tool devoted to the simulation of non linear ultrasound images. It is caracterised by a fast calculation time. It is freely available from the Creatis web site.
It has been shown that the control of the frame rate can significantly improve the relevance of the contrast imaging techniques based on multi-pulse emission.

We have proposed an ultrasound method to estimate the scatterer size corresponding to liver structures and its evaluation from biological tissue phantom. It is based on the spectrum analysis of the ultrasound signals backscattered by the cells and allows to estimate the concentration and size of the cells. The technique has been evaluated from experimental measurements performed on biological tissue phantoms with a concentration in the range 1% to 25%. These experiments show a good correlation between the actual parameters and those estimated in the frequency range [10MHz – 20 MHz].

The implemented techniques in the frame of this project will be evaluated on data acquired with the cmut probe which will be available in a few months.

Publications
[Var-13-1] F. Varray, O. Basset, P. Tortoli, and C. Cachard, «CREANUIS: A Nonlinear Radio Frequency Ultrasound Image Simulator«, Ultrasound in Medicine and Biology, in press, 2013.
[Lin-13] F. Lin, C. Cachard, R. Mori, F. Varray, F. Guidi, and O. Basset, «Ultrasound Contrast Imaging: Influence of Scatterer Motion in Multi-pulse Techniques«, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, In Press, 2013.
[Fra 12-1] Franceschini E. and Guillermin R., Experimental assessment of four ultrasound scattering models for characterizing concentrated tissue-mimicking phantoms, J. Acoust. Soc. Amer. 132(6) 3735-3747, 2012

Communications
[Var-13-2] F. Varray, L. Demi, K. van Dongen, O. Basset, C. Cachard, and M. Verweij, «Nonlinear acoustic propagation simulation tools: Comparison of BBGASM and INCS up to the fifth harmonic components«, IEEE International Ultrasonics Symposium, Prague, 22-26 Juillet 2013.
[Tou-13] M. Toulemonde, O. Basset, P. Tortoli, and C. Cachard, «Thomson’s multitaper high frame rate compounding for speckle reduction«, IEEE International Ultrasonics Symposium, Prague, 22-26 Juillet 2013.
[Fra 12-2] Franceschini E. and Guillermin R., Quantitative ultrasound estimates from tissue-mimicking phantoms with high scatterer volume fraction, 8th International Conference on Ultrasonic Biomedical Microscanning}, Saint-Paulin, Canada, 24-27 Septembre 2012.
[Fra 13] Franceschini, E. Guillermin R., Tourniaire F., Lamy E., Landrier J.-F., On the use of the Structure Factor Model to understand the measured backscatter coefficient from concentrated cell pellet biophantoms, Proceedings of the 2013 IEEE International Ultrasonics Symposium, Prague, 22-26 Juillet

The early diagnosis of liver diseases and/or identification of any focal lesions are key issues to consider a favorable prognosis. These objectives require non-invasive dedicated diagnostic tools and justify the development of innovative techniques based on the use of new technologies.
The BBMUT project aims to exploit the properties of a promising new technology of ultrasound probes, called CMUT, to propose new techniques for imaging and characterization of liver tissue.

BACKGROUND AND ECONOMIC AND SOCIETAL ISSUES
Liver cancer and more generally liver diseases, represent a major public health problem in terms of frequency and severity. For the detection of disease, the radiologist may use different imaging modalities. Ultrasound remains the first imaging method used because of its simplicity and availability.
The BBMUT project complements the diagnostic tools currently available (harmonic imaging, elastography, ...) by offering on one hand the possibility to improve the quality of native and harmonic images and on the other hand parametric measurements related to tissue structure taking advantage of the properties of the CMUT probes compared with piezoelectric sensors.
The medical issue of BBMUT project is to facilitate the diagnosis of liver diseases through earlier and more complete detection of lesions. The immediate benefit to the patient is a better prognosis. Improving the quality of images and information provided to the radiologist will also reduce the number of biopsies performed.
The market for ultrasound imaging equipment is today the most important. An expertise on a new ultrasound sensor technology is a major economic issue.

OBJECTIVES
The ultrasonic examination of the liver disease is frequently associated with the injection of a contrast agent. However, contrast imaging methods currently available are limited, mainly because of the large number of patients for whom harmonic imaging does not improve detection of tumors. It is then necessary to propose new techniques dedicated to the contrast agents and especially their nonlinear properties.
The BBMUT project involves the design of a CMUT probe whose specifications will be adapted to the examination of the liver. Harmonic imaging techniques will be implemented. Existing techniques and innovative techniques based on Chirp or composite signal emission will be implemented and the results compared with those obtained using an equivalent piezoelectric probe.
The properties of CMUT probes will also be used to provide a native image that has improved contrast without degrading the resolution. The large bandwidth and high directivity pattern of CMUT probes encourage the implementation of spatial and frequency compounding techniques.
Furthermore, we propose to develop an ultrasonic method for characterizing tissue structures adapted to liver, particularly by estimating the size of the scatterers to show that the estimated parameters related to the structures are correlated with liver histology. A quantitative measurement of the nonlinearity parameter is also proposed. A pre-clinical validation will quantify the diagnostic relevance of the proposed approaches.
PARTNERSHIP
This project involves 5 partners with complementary expertise : Vermon for the manufacture of ultrasonic probes, Creatis and Unit U930 in the field of ultrasound imaging, the LMA in ultrasonic tissue characterization and Hospices Civils de Lyon for clinical expertise.