Real-time 3D imaging may improve efficacy of cancer radiotherapy
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New 3D imaging technology developed at University of Michigan enables real-time measurement of radiation treatment, enhancing precision and potentially minimizing off-target effects.
“When patients with cancer receive radiotherapy, it’s typically a preplanned, offline process, with the presumption that what happens in the offline planning will be reproduced,” Issam M. El Naqa, PhD, adjunct professor of radiation oncology at University of Michigan Medical School, told Healio. “However, when patients are being treated, organs move, and movement of these organs can create all kinds of problems. Since X-ray treatment with radiation is precise, localized radiation, it can potentially cause more harm than the intended curative effects.”
El Naqa spoke with Healio about how his team has harnessed real-time 3D imaging and acoustic waves to more accurately guide radiation while sparing adjacent healthy tissues.
Healio: What inspired you to develop this technology?
El Naqa: We’ve been working on this topic since 2014, when it was a project of one of my graduate students at McGill University. Other institutions had been looking into what is called radiation acoustics. This is radiation’s interaction with other matter, generating different optical signals. We had a project related to that, and another related to ultrasound acoustics. The domain was very challenging, but the graduate student was outstanding. With her persistence and meticulous attitude, she was able to get that initial system working for us — not only what has been published in the literature, but also on equivalent soft tissue-like water. That was one of the first demonstrations that this could work.
When I moved to the University of Michigan, we were lucky to have a group that works on photoacoustic imaging, led by Xueding Wang, PhD. His group developed a technique for laser acoustic systems. So, we were working with the radiology group led by Paul L. Carson, PhD, as well as the radiation oncology group led by Kyle C. Cuneo, MD. Working together enabled us to develop this system. It was a collaboration between medical physics, which is something I represent, traditional oncology as practiced by Dr. Cuneo, and radiology and biomedical engineering with Drs. Carson and Wang.
Healio: How are acoustics and sound waves used to guide radiation treatment?
El Naqa: It’s twofold. When radiation interacts with matter, it generates heat, and that heat leads to an expansion of the tissue. This expansion generates sounds that are on the ultrasound range. So, it’s directly related to the radiation effect. We can show that there is a proportional relationship between them. The first person to recognize this phenomenon was Alexander Graham Bell, the inventor of the telephone. He invented something called the photophone in the 1890s. Fast-forwarding to the future, this allows us to visualize where the radiation is being deposited in real time so, if there are any errors, they can be corrected using a feedback-type system. That wasn’t possible in the past.
The design we had is a 2D matrix array. It enables us to not only see the radiation in one plan, but to see the whole volume of radiation at the same time. This is a prerequisite in order to ensure that the radiation is going directly to the cancer, not to the normal tissue. There is a good deal of work that still needs to be done to create a more accurate feedback system, so we can differentiate between what is cancer and what is not.
Healio: Where does this stand as far as validation?
El Naqa: For the initial validation we used phantoms, like any other new technology developed in the medical field. Then we used phantoms similar to human tissues. We initially had a liver from a pig, and then we did an animal study on rabbits here at Moffitt Cancer Center. It was an in vitro study using that system, and we started seeing that we were able, to a very decent level, to reconstruct where the radiation had gone, especially in the area of the cancer. It was very encouraging to do the first human study at University of Michigan, which is what this paper highlighted. We’d love to have more validation and studies to understand the extent to which the technology can help us. Some ideas we are currently working on include improving the image quality and image reconstruction using artificial intelligence techniques.
We are also looking to optimize the ultrasound transducer design. Currently, we have a prototype that is good for experimentation but not for mass production. So, we are looking for alternative ultrasound technologies that would give us more flexibility and also fit the clinical workflow much more easily than this one. That’s our second development. Our third development is an extension of the technology called ultra-high-dose treatment flash radiation. We want to see whether this technology can enable its safe implementation, because that technology generates a very strong signal in a very short time. Currently, we have an NIH grant to explore this in collaboration with the group at Massachusetts General Hospital, as well as our partners at University of Michigan.
Healio: Is there anything else you’d like to mention?
El Naqa: I want to emphasize the fact that this is still in its infancy. There have been a lot of exciting developments along the way, whether looking at anatomy, function or the combination with artificial intelligence, which may lead to mainstream applications sooner rather than later.
For more information:
Issam M. El Naqa, PhD, can be reached at Moffitt Cancer Center, 12902 USF Magnolia Drive, Tampa, FL 33612; email: issam.elnaqa@moffitt.org.
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