Clinical dosimetry in molecular radiotherapy
Clinical dosimetry in molecular radiotherapy is reaching a mature stage. Patient-specific dosimetry allow a major paradigm shift in the administration of molecular radiotherapy, from a “one size fits all” approach, where all patient receive the same activity, to real personalized medicine where administered activity is assessed specifically for each patient.
Radiopharmaceutical dosimetry basically comprises two steps:
- First, the determination of the spatial distribution of the radiopharmaceutical in the patient as a function of time needs to be determined, usually from quantitative scintigraphic imaging.
- Second, absorbed dose calculation must be performed using this distribution, with regards to propagating media, emitted radiation and their interactions within the patient.
Global clinical dosimetry accuracy relies on the accuracy of each of these steps. So far, procedures developed and used in the clinics differ in approach and sophistication, resulting in a large heterogeneity of implemented dosimetric approaches.
The main issue of current clinical dosimetry is that no standard operating procedures do yet exist.
One of the difficulties is how to evaluate the accuracy of the complete chain that leads from scintigraphic imaging to absorbed dose calculation. The absorbed dose within the patient’s tissues cannot be experimentally evaluated in situ. Therefore, in 2008 the project DosiTest (www.dositest.com) was initiated by INSERM (Centre de Recherches en Cancérologie de Toulouse) and IRIT (Institut de Recherche en Informatique de Toulouse) with the aim to evaluate the impact of the various steps that contribute to the realization of a dosimetric study, by means of a virtual multicentric intercomparison based on Monte Carlo modelling.
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