This project has a specific target of providing a low-cost, open source technological kit to allow scientists, academics, hackers, makers or OSHW fans to hack their way to ultrasound imaging - below 500$ - at home, with no specific equipment required. This piece of hardware follows the murgen dev-kit and the echomods, previous iterations. Those were simpler, less robust and less cost-efficient than this kit.
This board builds in particular on the famouse ice40 FPGA family which is low-cost, … and open-sourced.
It can use the “Project IceStorm”, which aims at reverse engineering and documenting the bitstream format of Lattice iCE40 FPGAs and providing simple tools for analyzing and creating bitstream files.
There’s a bit of action around these FPGAs these days, be it for tools, extensions, DIP designs,… and I thought using those for a ultrasound imaging device would permit to mix both FPGA and OpenSource.
Compared to previous iteration, this setup is:
The aim of this project is to build a small ultrasound imaging hardware and software development kit, with the specific goal of:
Previous projects has shown the feasibility of the hardware, but was not simple enough. Let’s keep the momentum, and use this dev kit in interesting ways.
This board has been developped for pedagogical purposes, to understand how ultrasound imaging and non-desctrucive testing work. This structure can be used to develop:
Why are you doing this ? or besides pedagogical uses of your prototype, we want to know if you are thinking about other applications ? Where your prototype can be more useful? In Africa for example, can your prototype solve some problems?
Medical ultrasound is based on the use of high frequency sound to aid in the diagnosis and treatment of patients. Ultrasound frequencies range from 2 MHz to approximately 15 MHz, although even higher frequencies may be used in some situations.
The ultrasound beam originates from mechanical oscillations of numerous crystals in a transducer, which are excited by electrical pulses (piezoelectric effect). The transducer converts one type of energy into another (electrical <–> mechanical/sound).
The ultrasound waves (pulses of sound) are sent from the transducer, propagate through different tissues, and then return to the transducer as reflected echoes when crossing an interface. The returned echoes are converted back into electrical impulses by the transducer crystals and are further processed - mostly to extract the enveloppe of the signal, a process that transforms the electrical signal in an image - in order to form the ultrasound image presented on the screen.
Ultrasound waves are reflected at the surfaces between the tissues of different density, the reflection being proportional to the difference in impedance. If the difference in density is increased, the proportion of reflected sound is increased and the proportion of transmitted sound is proportionately decreased.
If the difference in tissue density is very different, then sound is completely reflected, resulting in total acoustic shadowing. Acoustic shadowing is present behind bones, calculi (stones in kidneys, gallbladder, etc.) and air (intestinal gas). Echoes are not produced on the other hand if there is no difference in a tissue or between tissues. Homogenous fluids like blood, bile, urine, contents of simple cysts, ascites and pleural effusion are seen as echo-free structures.
If the process is repeated with the probe sweeping the area to image, one can build a 2D image. In practice, in the setups we’ll be discussing, this sweep is done with a transducer coupled to a servo, or using a probe that has an built-in motor to create the sweep.
Below is represented the improvement in signal capture.
I’ll definitely need to use the on-board Time Gain Compensation, did the tests on the benchmark unit.. but haven’t been using it on this rig.
A summary of the contributors using this family of hardware is detailed below. Some continents are still to be represented!
Under CC-BY-4.0, main article here