果冻传媒

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 果冻传媒, 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 .

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 porcine aortas in a setup that mimics the body and in ultrasounds of volunteer subjects at the Catharina hospital.

鈥淚 had to overcome some challenges for that,鈥� says Van Hal with a laugh. 鈥淏ecause 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.鈥�

Sending alternately, listening simultaneously

鈥淲ith 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.鈥�

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. 鈥淭his way, we have finally solved a big puzzle researchers had been working on for a while. That's really cool.鈥�

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.

鈥淭hat has everything to do with the fact that we can only pick up the echoes that are reflected back to the ultrasound probe,鈥� explains Van Hal. 鈥淏ut 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.鈥�

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: 鈥淎n 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.鈥�

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.

Vera van Hal, researcher

鈥淐urrent 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.鈥�

This is a major procedure for the patient, but is it always necessary? And will the procedure happen on time? 鈥淭his is increasingly subject for discussion these days,鈥� explains Van Hal. 鈥淚t 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.鈥�

Monitoring..., but what?

鈥淲ith 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.鈥�

鈥淭he second benefit, and perhaps even more important, is that with the extra information and better image quality, we can also determine the movement and expansion of the vessel wall more accurately.鈥�

鈥淣ot 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.鈥�

鈥淭he noise is visible in the image as large color variations - from strong dark blue to bright yellow, the extremes of the colormap. 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.鈥�

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.

鈥淲ith 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 鈥� the thrombus. Since we do not know the effect of the thrombus on the risk of aneurysm ruptures, this can provide a lot of important information.鈥�

鈥淲e 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.鈥�

鈥淭hat 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.鈥�

鈥淚t's almost as if I'm now stopping with this research when I鈥檓 at the pinnacle,鈥� says Van Hal, laughing. 鈥淣evertheless, I am very much looking forward to immersing myself in a new research subject.鈥�

The PhD research of Vera van Hal and Judith Fonken is part of the NWO Vidi research of Richard Lopata.