Liquid Dosimetry via Electron Paramagnetic Resonance Spectroscopy

The problem: Lack of water-equivalent dosimeters for radiotherapyCancer is a global public health problem. Radiotherapy is generally used as an essential method of cancer treatment.

Measuring the absorbed dose of radiation to ensure that the radiation delivered to the patient is accurate, is paramount and critical to patient safety, since tumor control and side-effects are highly sensitive to the applied dose.

For this purpose, in-vivo dosimetry (IVD) can be performed as a patient-specific measure of quality control and safety during radiotherapy. Clinical experience and dose prescriptions in radiotherapy have historically been based on the absorbed dose to water.

However, when a calibrated dosimeter as for today, which is not water equivalent, is used under non-reference conditions, direct determination of the correct absorbed dose to water is not possible and many detectors show an over-response. Water equivalent dosimeters are not available but particularly desirable in clinical applications.

The solution: A small, water-equivalent, non-toxic and liquid dosimeter with electron paramagnetic resonance spectroscopy readoutThis idea presents an innovative strategy for dose determination using a novel type of liquid, water-equivalent and non-toxic dosimeter with readout via electron paramagnetic resonance (EPR) spectroscopy.

This novel liquid EPR dosimeter consists of a small (mm-dimensions) capsuled water-based liquid detector material that can be placed on the patient's skin or in body cavities to measure the delivered dose at relevant locations in clinical situations.

The principle presented here is based on a dose-dependent EPR signal loss: Stable paramagnetic species dissolved in aqueous solution are transformed into diamagnetic products upon irradiation.

The proposed solution is not an incremental improvement of an existing procedure but an innovative approach making IVD easier to use, cheaper, more accurate and: water equivalent.