September 2016
34
I
maging
& M
achine
V
ision
FPGA expertise for signal processing
in portable ultrasound devices
By Jürgen Kern,
NetModule
As a vital means of clinical imaging
diagnosis, ultrasound examination
plays a key role in veterinary medicine.
Anesthesia is not required so many
diseases of the internal organs can be
quickly detected, and the results of
professional animal breeding checked.
Portable analytical devices for
real-time image display are less
intrusive for both humans
and animals.
US company E.I. Medical Imaging is rapidly
taking a lead in this market with its Ibex ultra-
sound devices for vets and professional animal
breeders. These devices enable swift determi-
nation of the fertilization phase and can verify
pregnancy at an early stage. In developing the
Ibex devices, E.I. Medical relies on the FPGA
expertise of NetModule. The latest genera-
tion - Ibex EVO - had to overcome a particu-
lar challenge with the interaction between the
software, the Xilinx FPGA, the system CPU,
data transmission using SerDes technology as
well as the real-time processing of ultrasound
signals all the way to the presentation of the
imagery.
In addition to its system design expertise in
realizing circuitry logic, NetModule applied
its professional competence in the real-time
processing of rapid image signals such as
ultrasound using powerful FPGAs. At the
heart of the Ibex ultrasound imagery unit
is a signal processor realized in FPGA. This
high-performance FPGA core provides an
ideal platform for the exceptionally high sig-
nal-processing throughput required in order
to realize basic functional elements.
These include the beam former for calculating
the high-resolution ultrasound beams from
numerous parallel receiver channels, the sig-
nal processing chain for filtering, envelope
detection and signal enhancement, as well
as the scan converter for converting polar
or rectangular scan formats into a standard
video-compatible format.
This Ibex EVO device generation, too, uses
the largest chip from the most cost-effective
Xilinx product line. This is important as the
ultrasound scanners are destined for sale in a
price-sensitive market. Whereas a Spartan3A
DSP served as the core of the first generation,
the Ibex EVO uses an FPGA from the Artix7
family, which enables much more power-
ful signal processing that provides images of
unprecedented quality on a portable ultra-
sound device of this type.
Ultrasound technology calls for extensive
and CPU-intensive signal processing, which
means that the number of available DSP cells
in the FPGA is key. A DSP cell contains a
hardware multiplier and two adders. At the
cycle frequency of 160 MHz applied here, this
type of cell can perform 160 million multi-
plications and 320 million additions per sec-
ond. However, the FPGA chip contains a large
number of these cells: where the first gen-
eration consisting of the Ibex Lite and Ibex
Pro products with the Spartan3A DSP chip
(model 3400A) used 126 of these arithme-
tic units, the new 2nd generation Ibex EVO
with the Artix7 (model 200T) features no less
than 740 DSP arithmetic units. This enables
a higher number of additions per second,
accordingly. For the Ibex EVO ultrasound
devices, this allowed the number of chan-
nels for sending and receiving to be increased
from 16 to 64. As a result the display of ultra-
sound images benefits, while sharpness and
contrast increase in line with the number of
channels used. This, in turn, enables a larger
display format in SVGA image quality.
The second hurdle was to realize the con-
nection of the transducer to the FPGA. After
all, 64 signal channels also require 64 ana-
log-to-digital converters. In this case, Net-
Module opted for the relatively new SerDes
technology that is capable of transmitting data
at 3.2 GBit per connection. The system con-
sists of a serializer/deserializer - for the serial
transmission of parallel data. The parallel data
to be transmitted is converted in the serializer
into a serial data stream with a high bit rate.
It is then transferred serially, and reconverted
again in parallel in the deserializer for further
processing. (Source: Wikipedia)
The system also features a function that sets
it apart: the Ibex Evo scanners can be used
to show the flow of blood in the body. This
technology, known as Doppler Ultrasound
and Colour Doppler, is based on the physical
phenomenon of the Doppler effect: if sound
Figure 1. Ibex EVO ultrasound
device for vets and professional
animal breeders
