Since the first demonstration of laser action in 1960, lasers have found applications in several fields of medicine. The achievements to date are impressive, however they are not always brought to the awareness of the public. “Dermatological laser interventions are spreading, as the cosmetics and beauty industries also advocate this technique. Eye surgeries, including lens corrections, also benefit a lot of people. But little is known about the other uses. For example, laser-assisted surgeries are not widely heard of, although patients undergoing such procedures heal much faster because the surgical wound is smaller,” says Katalin Hideghéty, head of the Biomedical Applications Group. She believes that there is room for improvement in the PR of laser-based medical procedures.
One of these techniques is the so-called laser interstitial thermal therapy (LiTT), in which tumours or tumour metastases are destroyed (using light-conducting fibres) by laser pulses. Lasers also have a wide range of applications in urology: they can be used for coagulation, vaporization and enucleation, depending on the wavelength of the laser and how deep it penetrates the tissue. Many urologists use lasers to treat patients with benign prostatic hyperplasia after they have exhausted the medication-based treatment options. The use of lasers has made the treatment of kidney stones, ureteral strictures and bladder tumours safer, which is particularly important for elderly patients with comorbidities.
Laser pulses can also be used to induce ionizing radiation for radiotherapy. The huge advantage of this novel radiation technique is that it offers high spatial resolution and the possibility to increase the dose rate by orders of magnitude. It is an exciting and interesting field of research. However, until recently, we only talked about irradiating biological samples with laser-driven particle beams,” said Katalin Hideghéty, adding that it was a huge breakthrough to make this feasible.
She considers it an incredible scientific achievement that using the laser available at ELI ALPS, the working group of the National Laser-Initiated Transmutation Laboratory of the University of Szeged could produce a stable neutron beam that was operational for a longer period (5 to 6 hours). “This was beyond all dreams,” said the professor, referring to a defining professional experience. “Thanks to these promising experiments, we hope that in the foreseeable future – meaning decades – laser-driven electron and neutron sources will be able to help the work of doctors. To this end, a laser-driven particle source at least as stable as the currently used linear accelerators must be developed in the coming years.”
To bring the hoped-for therapeutic possibilities closer to clinical applications, plenty of experiments, including radiobiological experiments, must be conducted. One of the classical approaches is to study cell cultures, another is to analyze living systems. Cell cultures can be healthy cells or tumour cells, monolayers or spheroids, i.e. different types of cells aggregating into small spheres. Traditional living systems include the drosophila melanogaster, mice and rats, but researchers sometimes also experiment with pigs and monkeys too. Another important experimental model is the zebrafish.
This vertebrate is used in a wide range of medical research. Our team has established its use in radiobiological testing due to the interesting fact that zebrafish share 70% of the genetic makeup of humans. The common set includes genes involved in the recovery from stress and other damaging effects. Zebrafish embryos are also excellent for the study of radiobiological effects. Even though the embryos are only one millimetre in size, properties important for researchers can be analyzed at this scale too.
In addition to the morphological changes and survival rates, we can study the effects on organs such as the alimentary canal, kidney, heart, etc., as well as the extent of brain function loss after intervention. The effect of the particles on different tissues can also be tested. “In contrast with cell cultures, fish embryos are less sensitive to environmental changes and do not require an overly sterile environment. Compared to other living models, they can be maintained more cost-efficiently, and can be easily transported. The latter factor is important because we also experiment with them at our sister institution in Prague,” the professor said.
Our researchers are investigating how neutron pulses can affect tumour and healthy tissues. Experiments with cell cultures and zebrafish embryos are also conducted to this end. To receive the appropriate dosage of neutron irradiation, biological samples need to be placed very close to the source at this early stage of technological development. Our colleagues solved this problem by putting a hermetically sealed cylinder containing the samples in the vacuum chamber.
After a few hours of irradiation, our researchers analyze the effects of the intervention on the embryos and their cells. The developmental abnormalities and hatching rates of embryos irradiated 24 hours post-fertilization are assessed, and the radiation-induced apoptosis (cell death) is quantified. Our colleagues look for signs of obvious differences compared to the control group.
The start looks promising, but there are still many questions to be answered. Nevertheless, Prof. Katalin Hideghéty hopes that we will not have to wait decades for the safe use of laser-based radiotherapy. Her dream is that human clinical research on laser-induced particles will commence within a few years.
Photos: Gábor Balázs