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Novel Ingestible Capsule X-Ray Dosimeter Enables Real-Time Radiotherapy Monitoring

By MedImaging International staff writers
Posted on 17 Apr 2023

Gastric cancer ranks among the most prevalent cancers worldwide. Precision is vital in modern radiotherapy, as it aims to target tumor cells while minimizing damage to healthy tissue. However, challenges such as diverse patient populations, treatment uncertainties, and varying delivery methods result in low efficacy and inconsistent outcomes. Real-time monitoring of radiation doses, particularly within the gastrointestinal tract, could enhance radiotherapy precision and effectiveness, but it remains a difficult task. Furthermore, current methods for tracking biochemical indicators like pH and temperature fall short in providing a comprehensive evaluation of radiotherapy. Now, a new invention may improve gastric cancer treatment by boosting the precision of radiotherapy, which is often combined with surgery, chemotherapy, or immunotherapy.

Conventional clinical dosimeters, such as metal-oxide-semiconductor field-effect transistors, thermoluminescence sensors, and optically stimulated films, are typically placed on or near a patient's skin to estimate the radiation dose absorbed in the targeted area. While electronic portal imaging devices have been investigated for treatment verification, these devices can be costly and absorb radiation, thereby reducing the patient's intended radiation dose. Ingestible sensors have been limited to monitoring pH and pressure, creating the need for an affordable swallowable sensor that can simultaneously track biochemical indicators and X-ray dose absorption during gastrointestinal radiotherapy. A research team at the National University of Singapore (NUS, Singapore) has created an ingestible X-ray dosimeter capable of real-time radiation dose detection. By integrating their innovative capsule design with a neural-network-based regression model that calculates radiation dose based on data captured by the capsule, the researchers achieved approximately five times more accurate dose monitoring compared to existing standard methods.

Image: The components of the dosimeter can fit into an 18mm by 7mm capsule (Photo courtesy of University of NUS)
Image: The components of the dosimeter can fit into an 18mm by 7mm capsule (Photo courtesy of University of NUS)

The novel ingestible X-ray dosimeter can measure radiation dose, pH changes, and temperature in real time during gastrointestinal radiotherapy. The capsule's main components consist of a flexible optical fiber wrapped in nanoscintillators that emit light in response to radiation, a pH-sensitive film, a fluidic module with multiple inlets for dynamic gastric fluid sampling, dual sensors for dose and pH measurement, a microcontroller circuit board that processes photoelectric signals for transmission to a mobile app, and a compact silver oxide battery to power the capsule.

Upon ingestion and reaching the gastrointestinal tract, the nanoscintillators emit a stronger luminescence when exposed to increased X-ray radiation. A sensor within the capsule measures this glow to determine the radiation dose delivered to the targeted area. Simultaneously, the fluidic module collects gastric fluid for pH detection by the color-changing film. This color shift is recorded by a second sensor inside the capsule. Additionally, both sensors can detect temperature, providing insight into potential adverse reactions to radiotherapy treatment, such as allergic responses.

The microcontroller circuit board processes photoelectric signals from the two sensors and transmits the information to a mobile app using Bluetooth technology and an antenna. The mobile app employs a neural network-based regression model to process the raw data, displaying information such as radiotherapy dose, temperature, and pH of the tissues undergoing treatment. The capsule dosimeter measures 18mm in length and 7mm in width, a standard size for supplements and medications, and has a production cost of S$50.

While currently designed for monitoring radiotherapy doses in gastric cancer, the capsule could also be adapted to track treatment for various malignancies with modifications to its size. For instance, a smaller capsule could be inserted into the rectum for prostate cancer brachytherapy or the upper nasal cavity for real-time measurement of absorbed doses in nasopharyngeal or brain tumors, minimizing radiation damage to adjacent structures. The research team is striving to advance their innovation toward clinical application. Future research includes determining the capsule's location and orientation after ingestion, devising a reliable positioning system to secure the capsule at the target site, and refining the accuracy of the ingestible dosimeters for safe and effective clinical use.

“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 Professor Liu Xiaogang from the Department of Chemistry under the NUS Faculty of Science, who led the research team.

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