Double pulse transmission - signal-to-noise ratio improvement in ultrasound imaging

This study investigates a new composing method of double
transmission of short coded sequences based on well-known Golay complementary
codes, which allow to obtain the higher signal-to-noise ratio (SNR) and increase
penetration depth. The proposed method can potentially find application in small
parts ultrasonography and play important role in examination of superficial
structures, e.g. in dermatology, ophthalmology, etc., where using longer coded
sequences leads to increase of a dead zone and single pulse transmission of
short sequences does not assure sufficient SNR. This paper discusses the
comparison of results obtained during the examination of four different lengths
pairs of Golay coded sequences excited at 3.7 MHz: the single 64-bits pair of
Golay sequences and combined sequences consisting of two 8-, 16-, and 32-bits
Golay codes separated in time. The experimental results have shown that using
the double pulse transmission allows to suppress considerably the noise level,
the SNR increases by 5.7 dB in comparison with the single pulse transmission of
Golay sequences of the same length. The results of this work indicate that
double pulse transmission enhances SNR while maintaining the dead zone short.