When the capsule is ingested and reaches the gastrointestinal tract, the nanoscintillators will exhibit heightened luminescence in the presence of increased X-ray radiation. A sensor within the capsule measures the glow from the nanoscintillators to determine the radiation delivered to the targeted area.

At the same time, the fluidic module allows gastric fluid to be collected for pH detection by a film which changes colour according to pH. This change in colour is captured by a second sensor within the capsule. In addition, the two sensors are able to detect temperature which could give an indication of any negative reactions to radiotherapy treatment, such as allergies.

The photoelectric signals from the two sensors are processed by a microcontroller circuit board which sends information via Bluetooth technology and an antenna to a mobile phone app. Using a neural network-based regression model, the mobile app processes the raw data to display information such as the radiotherapy dose as well as the temperature and pH of the tissues undergoing radiotherapy.

“Our novel capsule is a game-changer in providing affordable and effective monitoring of the effectiveness of radiotherapy treatment. It has the potential to provide quality assurance that the right dose of radiation will reach patients,” said Prof Liu. 

The capsule dosimeter measures 18mm in length and 7mm in width, a common size used for supplements and medicines, and costs S$50 to produce. Currently designed to monitor radiotherapy dose for gastric cancer, it could also be used to monitor treatment in different malignancies with further customisations to the capsule’s size. For example, making the capsule smaller could allow it to be placed in the rectum for prostate cancer brachytherapy or in the upper nasal cavity for real-time measurement of the absorbed dose in nasopharyngeal or brain tumours, minimising radiation damage to surrounding structures.

Next steps

The research team is working to bring their innovation towards clinical application. Further research includes identifying the capsule's position and posture after ingestion, developing a robust positioning system to anchor the capsule at the intended target site, and further calibrating the accuracy of the ingestible dosimeters for safe and effective clinical use.