
Parameter estimation of the homodyned K
distribution based on neural networks and trainable
fractional-order moments
Michal Byra∗†, Ziemowit Klimonda†, Piotr Jarosik†
†Institute of Fundamental Technological Research,
Polish Academy of Sciences, Warsaw, Poland
∗Corresponding author, e-mail: mbyra@ippt.pan.pl
Abstract—Homodyned K (HK) distribution has been widely
used to describe the scattering phenomena arising in various re-
search fields, such as ultrasound imaging or optics. In this work,
we propose a machine learning based approach to the estimation
of the HK distribution parameters. We develop neural networks
that can estimate the HK distribution parameters based on
the signal-to-noise ratio, skewness and kurtosis calculated using
fractional-order moments. Compared to the previous approaches,
we consider the orders of the moments as trainable variables
that can be optimized along with the network weights using
the back-propagation algorithm. Networks are trained based on
samples generated from the HK distribution. Obtained results
demonstrate that the proposed method can be used to accurately
estimate the HK distribution parameters.
Index Terms—homodyned K distribution, neural networks,
parameter estimation, quantitative ultrasound.
I. INTRODUCTION
Homodyned K (HK) distribution has been widely used to
describe the scattering phenomena arising in various research
fields. In ultrasound (US) imaging, the HK distribution has
been utilized to model the backscattered echo amplitude and
quantitatively assess tissue structure [1]. For example, the
HK distribution was applied for ultrasound based temperature
monitoring and tissue characterization [2], [3], [4], [5].
Various methods have been developed for the estimation
of the HK distribution parameters. Hruska and Oelze pro-
posed a level-set estimation technique based on the signal-to-
noise ratio, skewness and kurtosis parameters calculated using
fractional-order moments [6]. Destrempes et al. proposed an
iterative estimation technique based on the first moment of the
intensity and two log-moments, namely the X- and U-statistics
[7]. Building on the previous works, Zhou et al. utilized an
artificial neural network (ANN) to estimate the parameters of
the HK distribution [8]. Authors utilized the signal-to-noise
ratio, skewness, kurtosis, X- and U- statistics as the input to
the feed-forward neural network.
In this work, we propose a machine learning based tech-
nique for the estimation of the HK distribution parameters.
Similar to Zhou et al., we train our neural network based on
the SNR, skewness and kurtosis statistics [8]. However, in
our case the orders of the moments used for the calculations
are not fixed. Hruska and Oelze presented that the choice of
the moments is important for the accurate estimation of the
HK distribution parameters [6]. To improve the estimation,
we treat the orders of the moments as trainable variables that
can be optimized along with the network weights using the
back-propagation algorithm.
II. METHODS
A. Homodyned K distribution
The probability density function of the HK distribution can
be expressed in the following way:
p(A) = A
∞
Z
0
hJ0(sh)J0(Ah)1 + h2σ2
2u−udh, (1)
where Astands for the amplitude, J0is the zero-th order
Bessel function of the first kind and variable his used for
the integration. Parameters s2and σ2stand for the coherent
and diffusive signal power. HK distribution has two param-
eters used for the quantitative assessment of the scattering
phenomena in US. The first parameter, u, is the scatterer
clustering parameter reflecting the number of the scatterers
in the resolution cell. The second quantitative parameter of
the HK distribution is expressed as the ratio k=s
σand is
related to the spatial periodicity of the scatterer distribution.
B. The RSK estimator
Hruska and Oelze proposed the level-set method for the
estimation of the HK distribution parameters based on the
signal-to-noise ratio (R), skewness (S) and kurtosis (K) of the
amplitude, denoted as the RSK estimator [6]. These three can
be calculated with the following equations:
R(v) = E[Av]
(E[A2v]−E2[Av])1/2,(2)
S(v) = E[A3v]−3E[Av]E[A2v]+2E3[Av]
(E[A2v]−E2[Av])3/2,(3)
arXiv:2210.05833v2 [cs.LG] 16 Dec 2022