A team led by researchers at Tokyo Metropolitan University, in collaboration with Tohoku University and Aubray, has used a heteroepitaxial diamond material developed by Aubray to show that lab-grown diamonds have the potential to create radiation dosimeters for both medical diagnostics and radiotherapy. They demonstrated that diamond-based dosimeters have much better sensitivity per volume than conventional detectors and can accurately measure doses in the same energy range as diagnostic X-rays. Using the same device for dosimetry for both diagnosis and treatment may improve consistency.
Accurately measuring radiation dose is extremely important in clinical practice. The standard option for dosimetry (dosimetry) is an air-based ionization chamber, in which radiation passing through a large volume of air produces a measurable electrical current. However, a major challenge lies in the range of doses that dosimeters need to handle. For example, the dose for diagnostic X-rays is much lower than for radiation therapy. The former, air-based ionization chambers, can require significant amounts of air, making the detector unwieldy and leaving little room for mapping how the dose varies with detector position. In practice, the sensitivity is prohibitively low at very low dose levels.
Now, a research team led by Professor Kiyomitsu Shinjo of Tokyo Metropolitan University has challenged this paradigm by using an entirely new material for the ionization chamber. Instead of air, they turned to diamonds grown in the lab using a method known as heteroepitaxy. They used cutting-edge technology to grow lab-grown diamonds on electrodes, arranging atoms layer by layer. Using this new detector, the team performed systematic experiments on how diamond could be used as an ionization chamber at the types of doses seen in diagnostic X-rays. With dimensions of 4 x 4 x 0.5 mm, this chamber has approximately 1250 times less volume than a typical air ionization chamber, but is 13,500 times more sensitive per volume when a relatively low voltage of -100V is applied. They demonstrated excellent linearity of the response to dose with little dependence on X-ray energy. Importantly, the success with the low energies used in diagnostic equipment suggests that the high doses seen in treatments may also be easily addressed. This paves the way for the development of dosimeters that can be used in both diagnostics and radiotherapy. Diamonds are also made of carbon, which makes them a good analogue of human tissue.
This is a major step forward for dosimetry for many reasons. The compactness of the device allows it to be applied virtually anywhere, from personal dosimetry and real-time measurements during treatment to environmental monitoring. This is compact enough to create arrays, like a camera’s sensor array, that can map changes in dose over an area. Sensitivity to low doses also has the potential to revolutionize our understanding of the effects of low-dose exposure on the human body, an important component of radiation research. Most importantly, it opens the door to achieving much-needed consistency in radiation dose measurements. The possibility that the same device could be used in completely different situations would make dose comparisons scientifically sound and fair. The team’s success promises to lead to major advances both in medical practice and in our understanding of radiation in the environment.
sauce:
Tokyo Metropolitan University
Reference magazines:
Shinsho, K., others. (2026). Initial evaluation of a heteroepitaxial diamond ionization chamber operating at low voltages for diagnostic X-ray dosimetry. medical physics. DOI: 10.1002/sq.70363. https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.70363
