PhD defence G. (Gonzalo) Collado Lara

Summary:

Ionizing radiation is used in radiotherapy to induce tumor cells death. However, radiation is not selective to cancerous cells, but also damages healthy tissues. Excessive damage to critical organs around the tumor may result in severe, undesired secondary effects. The goal of in vivo dosimetry is to independently measure the
dose delivered to the patient, aiming to lift the therapy uncertainties, and hence to further reduce the dose to healthy organs. However, up to date, no dosimetry technique has been widely adopted as a gold standard.

In this thesis, we have investigated the combination of Ultrasound Contrast Agents (UCAs) and Ultrasound Imaging (US) for radiation dosimetry. The UCAs investigated here are injectable particles, generally smaller than a red-blood-cell, with a gaseous (microbubbles, MBs) or a liquid (nanodroplets, NDs) core, and a coating layer that increases their stability. Here, we studied two different principles by which radiation interacts wit UCAs, as described on Chapter 1: On the one hand, radiation may modify the physicochemical properties of MBs, ultimately affecting their acoustic response. On the other hand, radiation may trigger the phase change of NDs (acoustically invisible) into  MBs (acoustically resonant), which is easily detectable with an US system. The chapters of this thesis elaborate
on experimental studies in well-controlled in vitro environment, aiming to assess the potential of this technique for dosimetry, and its feasibility for clinical translation.