Real-time in vivo optoacoustic monitoring of tumor ablation with a 1064 nm laser source

Laser ablation (LA) is gaining acceptance for the treatment of tumors as a viable alternative to surgical resection. In parallel, optoacoustic tomography (OAT) has enabled defining new regimes for diagnosis and characterization of malignant neoplastic lesions with high sensitivity and specificity. Even though pulsed nanosecond lasers are commonly used for both imaging and therapeutic purposes, real-time thermal treatment monitoring with a single laser source has not been previously attempted. Herein, we demonstrate the feasibility of combined OAT and LA by percutaneous irradiation of subcutaneous tumors with a 100 mJ short-pulsed (~5 ns) laser operating at 1064 nm and 100 Hz pulse repetition frequency. The OAT images rendered with a spherical ultrasound transducer array enabled real-time monitoring of the LA lesion progression, which is essential for determining the optimal treatment end-point. Local changes in the optoacoustic signal intensity associated with the induced temperature changes as well as structural alterations in the tumor vasculature could clearly be observed. The optoacoustic volumetric projections further correlated with crosssections extracted from the excised tumors. This newly enabled capability anticipates new theranostic approaches in cancer research and treatment with potential applicability in a clinical setting