The hepatogram: measuring liver rigidity

Sabine Ben­samoun is a research direc­tor at the CNRS and works in the CNRS/BMBI joint research unit at UTC. She is also a research asso­ciate at the Mayo Clin­ic (Rochester, USA) and a mem­ber of the CNRS Nation­al Com­mit­tee (CoNRS). With Dr Fab­rice Charleux of ACRIM, she took part in the inter­na­tion­al liv­er study that led to the hepatogram.

In prac­ti­cal terms? «Until now, to analyse the lev­el of rigid­i­ty of the liv­er, a doc­tor would pre­scribe an exam­i­na­tion of the organ using the mag­net­ic res­o­nance elas­tog­ra­phy (MRE) tech­nique. From 2024, as with an elec­tro­car­dio­gram, doc­tors will be able to pre­scribe a hepatogram, a name that will be approved in 2023, for a spe­cif­ic exam­i­na­tion of the liv­er. It’s a quick, non-inva­sive test that pro­vides a more accu­rate diag­no­sis. MRI gives a pure­ly anatom­i­cal image of the organ analysed, where­as MRE gives us an image that indi­cates the degree of rigid­i­ty of the tis­sue analysed,» explains Sabine Bensamoun.

The sto­ry of MRE began when she returned to France after her post-doc at the Mayo Clin­ic, a world ref­er­ence in med­ical research. She joined the CNRS and con­tin­ued her col­lab­o­ra­tion with the Mayo Clin­ic, where a mod­ule had been devel­oped which, cou­pled with MRI (mag­net­ic res­o­nance imag­ing), aims to bet­ter char­ac­terise the mechan­i­cal or func­tion­al prop­er­ties of soft organs, includ­ing the liv­er. This is known as mag­net­ic res­o­nance elas­tog­ra­phy (MRE). This was not avail­able in France when it was intro­duced in 2006. Accord­ing to Sabine Ben­samoun, what does this tech­nique offer com­pared with oth­er imag­ing tech­niques? In par­tic­u­lar, it enables us to obtain a bet­ter diag­no­sis of the sever­i­ty of patholo­gies, improve patient fol­low-up and, last­ly, per­son­alised treat­ments, etc.». All that remained was to val­i­date the MRE clinically..

The UTC is one of ten research cen­tres select­ed by the Mayo Clin­ic world­wide, and the only one in France, to ben­e­fit from this mod­ule. It was still to be cou­pled it to an MRI machine. «I got in touch with Dr Fab­rice Charleux, a radi­ol­o­gist at ACRIM and told him about my plans; he was inter­est­ed, par­tic­u­lar­ly by the research aspect. At the time, he was work­ing on Gen­er­al Elec­tric machines, which proved oppor­tune and use­ful because the mod­ule devel­oped by the Mayo Clin­ic, which was only a pro­to­type, only worked with this type of machine. For more than 10 years, I con­tin­ued to improve the pro­to­col I had first devel­oped at the Mayo Clin­ic on mus­cle tis­sues, in par­tic­u­lar for the dis­or­der known as Duchenne mus­cu­lar dys­tro­phy and mus­cle age­ing», she points out.

After years of research, the data col­lect­ed from all over the world was analysed at the Mayo Clin­ic. For all the par­ties involved, includ­ing UTC and ACRIM, the gam­ble paid off. The result is the MRE, a non-inva­sive diag­nos­tic tool for analysing the entire liv­er to estab­lish the stage of fibrosis.

And what is your inter­est in the human liv­er? «In fact, the Mayo Clin­ic con­tin­ued to improve the mod­ule for future com­mer­cial­i­sa­tion. At the time, they were work­ing exten­sive­ly on the liv­er organ and want­ed to have broad­er sources of data. To do this, sev­er­al research cen­tres had to be equipped with this new mod­ule. As far as we were con­cerned, we start­ed work­ing on the liv­er, but with the for­mer mod­ule,» she says.

How does an MRE work? «If we take the liv­er as an exam­ple, we can see that the more dis­eased it is, the more rigid it becomes. Thanks to MRE, we can quan­ti­fy the organ’s rigid­i­ty, with stages rang­ing from one to four, the high­est indi­cat­ing liv­er cir­rho­sis (4). The mod­ule takes the form of a box fit­ted with a speak­er that sends low-fre­quen­cy air pres­sure through a stim­u­la­tor that is placed on the tis­sue to be analysed. The move­ment of this low-fre­quen­cy vibra­tion is then mon­i­tored and, depend­ing on the speed at which the wave prop­a­gates through the organ con­cerned, the degree of sever­i­ty of the pathol­o­gy can be esti­mat­ed. It’s a real alter­na­tive to biop­sy,» describes Sabine Bensamoun.

Of all the soft tis­sues, the liv­er is cur­rent­ly the one where MRE is per­formed as a rou­tine clin­i­cal pro­ce­dure. In the Unit­ed States, more than 100 000 exam­i­na­tions, now known as hepatograms, were car­ried out in 2023, and more than 2,300 new­gen­er­a­tion MREs have been installed world­wide, includ­ing the one at ACRIM.

What’s next? «Our exper­tise in fibrous patho­log­i­cal tis­sues (mus­cle, liv­er) was invoked dur­ing the COVID-19 pan­dem­ic. We are already work­ing on a clin­i­cal pro­to­col applied to lung tis­sue,» she concludes.

Le magazine

Avril 2024 - N°62

Faire face aux enjeux environnementaux

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