Molecular radiotherapy (MRT) specifically targets cancerous cells through the use of radioactive treatments that attach themselves to tumours in specific parts of the body, such as the liver. Currently, molecular radiotherapy is used in palliative care but it has the potential to become a first line treatment for cancer. Tailoring MRT for individual patients relies on accurately measuring the radioactivity of the drug and determining the therapeutic dose delivered to the tumour.
The EMRP project HLT11 Metrology for molecular radiotherapy successfully divided the radiation treatment process into a series of steps that could be related to primary standards, and developed methods for verifying the accuracy of each step. The project investigated the use of imaging techniques, to determine the dose delivered to the target tumour site.
- Developed the world’s first primary standard for molecular radiotherapy that enables measurement of the absorbed radiation dose to water from a radioactive solution.
- Developed measurement methods to accurately determine the activity of the radioactive drugs used in MRT, and extended an existing activity measurement method to highly radioactive MRT radiotherapylevels.
- Developed methods for calibrating and validating quantitative imaging techniques using body models with traceability to the SI.
- Established best practice measurement procedures and traceability to existing absorbed dose standards for a range of radionuclides used in MRT.
- Constructed mathematical models that link the radioactivity of the drug, the fraction of it that accumulates in the organ and its biological half-life. This enabled an accurate determination of the amount of radiation absorbed by the tumour and the therapeutic dose delivered to the tumour.
The project team worked closely with the nuclear medicine community, including academics, clinicians and manufacturers of MRT instrumentation and materials. Project outcomes will be incorporated into a chapter of the MRT dosimetry handbook and protocols within the IAEA Human Health Series, providing a single highly regarded reference document for nuclear medicine physicists and clinicians. Commercial imaging software developers are interested in using the project’s step-wise approach for determining the absorbed radiation dose, and offering it as a commercial product for the nuclear medicine community. For example, highly accurate radioactivity measurement of Yttirum-90 microspheres has been achieved as a result of this project. This is the first step towards individualised patient treatment plans.