For the diagnosis of disorders and the monitoring of patients, healthcare providers need to be able to look not only at a patient but also inside the body of a patient. Sending and receiving ultrasound waves is one of the most common methods used to do this. From a pregnancy consultation to the cardiologist - ultrasounds are widely used. By making ultrasound images with several transducers simultaneously and combining that information, the image quality of an ultrasound can be significantly improved.
Ultrasound is a well-known and widely used way in healthcare to look inside our body. To make the invisible visible. Making ultrasounds costs sixty to eighty euros each, while a CT or MRI scan costs nearly a thousand euros. However, ultrasounds also have disadvantages, which means that more expensive alternatives are often necessary.
One of them is the dependency on the quality of the sonographer to make exactly the right images. Another is the fact that the sound waves collide with various tissues in the body and then bounce back. Muscle and fat tissue, in particular, scatter the waves, which produces noise and low image quality.
At the mini-symposium Sound Solutions in honor of Richard Lopata's inaugural lecture , various researchers who want to improve the quality of ultrasound were interviewed. This research also takes place at several locations at TU/e, including in the PULS/e lab
See more with two transducers
PhD candidate Vera van Hal obtained her PhD on 1 April, no joke, on researching whether you can also make an ultrasound with two transducers simultaneously: so-called multi-aperture ultrasound. And preferably an ultrasound of an aneurysm of the aorta in the abdomen .
The positive answer is that yes, you can, and with amazing results. This is the first time that this has been achieved in the world. Both in the lab in experiments with pig aortas in a setup that mimics the body and in ultrasounds of volunteer subjects at the Catharina hospital.
"I had to overcome some challenges for that," says Van Hal with a laugh. "Because sending out sound waves twice also means picking up two echoes, doubling the noise and signals that can disrupt or cancel each other. Previous PhD students didn't quite figure that out yet."
Sending alternately
"With multi-aperture ultrasound, we use principles from radar technology, where we transmit alternately and then listen with two transducers simultaneously. Each transducer sends out one signal and picks up two: the echo of its own signal and that of the transducer next to it. Two transducers produce four signals. And then we combine all four returning signals with the help of smart software."
This way, we have finally solved a big puzzle that researchers have been working on for a while. That's really cool.
Vera van Hal, researcher
Van Hal managed to link these four signals in time and location and combine them into one ultrasound image on the screen, despite essential challenges such as disturbances and shifts of ultrasound images that can occur due to significant differences in the speed of sound of different tissues.
In doing so, she solved this problem for the first time. "This way, we have finally solved a big puzzle researchers had been working on for a while. That's really cool."
Smaller blind spot
With the four signals, the image becomes sharper, and details can be seen better. Yet the advantage is also in another aspect. Certain structures that were previously not visible on an ultrasound image can now be made visible by looking at them from a different direction.
"That has everything to do with the fact that we can only pick up the echoes that are reflected back to the ultrasound probe," explains Van Hal. "But if we combine the images, we see less noise, and we can fill the 'holes' in the image of one transducer with the image of the other transducer. This way, we see more information in the full ultrasound image."
Keeping an eye on the aneurysm
Ultrasound is used to monitor pregnancies and cardiovascular diseases. It shows nicely in real-time what is happening in the body. Additionally, it is painless and less time-consuming for patients and hospitals to make an ultrasound during a check-up.
Van Hal: "An aortic aneurysm is a dangerous dilation of the vascular wall of the largest artery in our body. Such an aneurysm is often discovered by chance and then closely monitored. Because when it ruptures, the internal bleeding is so severe that it is life-threatening."
"Current medical manuals assume that the risk of tearing increases at a diameter of 55 mm in men and 50 mm in women. These statistics are based on following large numbers of patients and give a reasonable indication of the risk. So, the dilation in the aorta is regularly measured and operated on when the diameter exceeds the limit."
This is a major procedure for the patient, but is it always necessary? And will the procedure happen on time? "This is increasingly subject for discussion these days," explains Van Hal. "It is suspected that large aneurysms can also be safe and that smaller ones sometimes rupture. We don't know exactly what causes these differences. And whether we can measure that cause is the second question."
Monitoring..., but what?
"With our dual-transducer ultrasound, the field of vision, contrast, and resolution are so much better that we can see the entire circumference of the aneurysm, but also the surrounding tissues."
"The second benefit, and perhaps even more importantly, is that with the extra information and better image quality, we can also determine the movement and elongation of the vessel wall more accurately."
"Not only can we measure that accurately, but we can also show it with colors over the moving images. When you then compare the images of one transducer with those of a double transducer, you immediately see that with the latter, the images are much more accurate and contain less noise."
"The noise is visible in the image as large color variations - from strong dark blue to bright yellow, the extremes of the color folder. With the help of two ultrasound probes, we can significantly reduce this noise and properly analyze the local strain differences in the material itself. This allows us to say something about the difference in material properties in the aneurysm."
Modelling strain in vessel wall
It has been known for some time that research is a team sport. The fact that two PhD students start a project together, which for both is a continuation of their master's thesis, is already pretty rare. And when they both obtain their PhDs with a cum laude review within one week of each other, that is unique.
Judith Fonken received her PhD cum laude from the Department of Biomedical Engineering on 25 March for the modeling of an abdominal aortic aneurysm. Her major focus was to be able to better predict how such a life-threatening aneurysm would develop in an individual patient based on reliable measurement data. Usability for the doctor was paramount to her model.
With her model, the improved images and the extra information about the strains in the vessel wall can be used to help the doctor make better decisions for each patient. In the long term, their research will not only improve healthcare and reduce costs but also improve the lives of every patient with this condition.
Read the Cursor Final Piece about the two PhD candidates
Judith Fonken makes an ultrasound. Photo: Bart van Overbeeke
High stress
Strain indicates strong forces in any material and, therefore, also stress. If stresses are too high, the material will break. This would also break a vessel wall.
"With our new ultrasound techniques, we can accurately determine this strain not only in the vessel wall but also in the material stuck to the vascular wall inside - the thrombus. Since we do not know what the influence of this is on the chance of the dilation tearing, this can provide a lot of important information."
"We are now very close to models that can predict when the aneurysm will become dangerous based on this type of image. Doctors will then determine per patient when surgery is necessary, instead of relying on statistics."
"That would save healthcare expenses and save patients from an unnecessary operation. It is also possible that people who need it are operated on sooner. Hopefully, our research will really improve everyone's situation in the future, this way: for patients, doctors, and society alike."
"It's almost as if I'm now stopping with this research when I'm at the pinnacle," says Van Hal, laughing. "Nevertheless, I am very much looking forward to immersing myself in a new research subject."
The PhD research of Vera van Hal and Judith Fonken is part of the NWO Vidi research of Richard Lopata .
