Contrast-Enhanced Ultrasound to Detect Early Microvascular Changes in Skeletal Muscle after High-Dose Radiation Treatment

Effect of a Radiotherapeutic Megavoltage Beam on Ultrasound Contrast Agents

Collateral damage to healthy surrounding tissue during conventional radiotherapy increases when deviations from the treatment plan occur. Ultrasound contrast agents (UCAs) are a possible candidate for radiation dose monitoring. This study investigated the size distribution and acoustic response of two commercial formulations, SonoVue/Lumason and Definity/Luminity, as a function of dose on clinical megavoltage photon beam exposure (24 Gy). SonoVue samples exhibited a decrease in concentration of bubbles smaller than 7 µm, together with an increase in acoustic attenuation and a decrease in acoustic scattering. Definity samples did not exhibit a significant response to radiation, suggesting that the effect of megavoltage photons depends on the UCA formulation. For SonoVue, the influence of the megavoltage photon beam was especially apparent at the second harmonic frequency, and can be captured using pulse inversion and amplitude modulation (3.5-dB decrease for the maximum dose), which could eventually be used for dosimetry in a well-controlled environment.