Dosimetria acustoelástica da dose absorvida em phantoms de gel equivalentes a tecido mole

Abstract

Cancer remains one of the major challenges to global public health, ranking among the leading causes of death and imposing increasing demands on healthcare systems. In this context, radiotherapy plays a central role in cancer treatment, being used for both curative and palliative purposes. The success of this technique depends on the accurate determination of the absorbed dose, which is essential to ensure therapeutic effectiveness and patient safety. The need for three-dimensional verification of dose distribution has driven the development of polymer gel dosimeters, which allow volumetric recording of radiation. Traditionally, these dosimeters are read using magnetic resonance imaging, a high-cost technique with limited accessibility in clinical practice. This work investigates the feasibility of using ultrasonic techniques as an alternative method for reading MAGIC-F polymer gel dosimeters. Acoustic and mechanical properties were evaluated as a function of material concentration and absorbed dose. The system was calibrated using homogeneous bovine gelatin samples at different concentrations in order to characterize the acoustic response and assess measurement reproducibility. Three experimental configurations were tested: contact method in pulse-echo mode, immersion method in the same mode, and transmission mode using immersion transducers. The methodology was then applied to MAGIC-F gel samples irradiated with doses ranging from 0 to 40 Gy, whose responses were qualitatively compared using magnetic resonance imaging. The results indicated the sensitivity of acoustic parameters to variations in concentration and dose, showing behavior consistent with radiation-induced polymerization. An increase in sound velocity, attenuation coefficient, and elastic moduli was observed with increasing dose. The comparison between experimental setups indicated differences in performance among the methods, with immersion systems associated with greater stability and measurement reproducibility. Overall, the results demonstrate the potential of ultrasound as a complementary tool for reading polymer gel dosimeters, based on acoustic and mechanical parameters as indirect indicators of absorbed dose. With further methodological improvements and the development of a practical protocol, the investigated approach may become a viable alternative for three-dimensional dosimetry in radiotherapy.