Objective. There is a need for patient-specific dose quantification (dosimetry) in Molecular

Radiation Therapy (MRT). Cherenkov light generated in the tissue by charged particles

produced by the radioactive decay of radiopharmaceuticals offers an unprecedented

opportunity for MRT dosimetry. While the intensity of the emitted Cherenkov light is

proportional to the dose, the intensity of light emerging and measured at the patient

surface depends on patient anatomy and tissue optical characteristics. This results in an

inter-patient variability of the linear relationship between Cherenkov light intensity at the

patient surface and the dose delivered to the tumour that hinders the implementation of

Cherenkov light-based dosimetry. A multi-patient study of Cherenkov light emission in

MRT of thyroid cancer is performed and a correction technique for the surface light

intensity is introduced to reduce this inter-patient variability.

Approach. Numerical experiments using clinical patient Computed Tomography data and

Monte Carlo simulations are performed for a set of patient anatomies and a range of

values of tissue optical parameters and tumour radioisotope uptakes, resulting in 135

treatment realisations. The impact of anatomy and tissue optical characteristics on the

characteristics of Cherenkov light is investigated. A patient-specific factor defined as the

product between the fraction of the light emitted in the tumour that emerges on the

patient surface and tumour volume and mass density is introduced to correct the intensity

of light emerging at the patient surface for the dependence on patient anatomy and tissue

optical characteristics.

Main results. There is a large inter-patient variability in the relationship between the

surface light intensity and dose delivered to the tumour. The correction technique greatly

reduces this variability and enables the derivation of a dosimetry calibration curve.

Significance. This study provides an important step towards quantitative MRT dosimetry

based on Cherenkov light emitted during treatment.