ARFI
is an elastographyc method for liver fibrosis assessment, very used
in clinical practice, but there are no data about the ideal depth
into the liver parenchyma where the measurements to be made.
The
aim
of our study was to compare liver stiffness measurements evaluated by
ARFI at several different depths into the liver parenchyma, using as
reference method Transient Elastography-TE.
Methods:
the study included 34 consecutive subjects with or without liver
diseases, in which liver stiffness was evaluated by ARFI (using
Siemens Acuson S2000TM)
and TE.
73.5%(25)
were women and 26.5%(9) men, with a mean age of 27+/-10 years old.
70.6%(24) were healthy volunteers without known hepatic injury and
29.4%(10) had different liver diseases: 4 patients with HBV
infection, 3 with HCV and 3 with liver cirrhosis.In
each subject we performed TE assessment (classic methodology) and 10
valid ARFI measurements at 1cm, 2cm, 3cm, 4cm, 5cm and 6cm from the
liver capsule. The
median value of 10 measurements was calculated and expressed in m/s.
We considered valid only the measurements with IQR<30%, SR>60%,
similar to TE.
Results:
valid
ARFI measurements were obtained in all depths in 27/34 patients
(79.4%). ARFI values at 1cm under the liver capsule were
significantly higher (p<0.001) as compared to those at 2cm, 3cm,
4cm, 5cm and 6cm respectively and also at 2cm vs 6cm (p<0.01)
(paired t test). There were no significant differences between ARFI
values measured at the other depths into the hepatic parenchyma.
There was a direct, strong correlation between TE values and ARFI
values in 1cm (r=0.491,
p= 0.003),
2cm (r=0.636,
p= 0.00005),
3cm (r=0.667,
p= 0.00002),
4cm (r=0.671,
p= 0.00002)
and 5cm (r=0.486,
p= 0.004),
but not with ARFI values in 6cm (r=0.256,
p= 0.198). The strongest correlations with TE were observed for ARFI
measurements performed at 2, 3 and 4 cm under the capsule.
Conclusion:
the
most accurate measurements obtained by ARFI seem to be those
performed between 2-4 cm under the liver capsule.
