The acoustic pressure field or heat deposition from the passage of an ultrasonic wave can produce a perceptible alteration in the medium’s optical refractive index. With proper placement of the light source and imaging camera, the optical effect can be recorded. This talk describes an optical temperature measurement methodology dubbed laser-ray-bundle (LRB) of the heat deposition from a high intensity focused ultrasound (HIFU) transducer in a transparent tissue phantom. The method does not require calibration, and directly converts the thermo-optic signal to temperature without recourse to any iterative computations. LRB boasts of excellent temporal and spatial resolutions and high temperature sensitivity better than any fine wire thermocouple. Furthermore, it is completely non-invasive. The LRB method is demonstrated with the heat deposition from single millisecond long HIFU pulses in a PDMS tissue phantom or from a train of single pulses with very good performance. The method represents a new capability for quickly assess a HIFU transducer output, and for laboratory and preclinical studies of heating near tissue interfaces including bone, air, or fat. A preliminary experimental setup for measuring the acoustic pressure field is presented.

This study introduces a predictive model based on artificial neural networks (ANNs) for estimating the dynamic performance of commercially available sensible thermal energy storage (STES) systems. The model was trained and validated using high-resolution experimental data measured from two vertical cylindrical tanks (0.3 m³ each) including internal heat exchangers and operating under both heating and cooling modes. A comprehensive sensitivity analysis was conducted on 28 ANN architectures by varying the number of hidden neurons and input delays. The optimal configuration, designated as ANN5 (12 neurons, delay = 1), demonstrated superior accuracy in predicting temperature profiles and energy exchange. Validation against an independent dataset confirmed the model’s robustness, achieving normalized root mean square errors (NRMSEs) between 0.0022 and 0.0061 for the hot tank and between 0.0057 and 0.0283 for the cold tank. Energy prediction errors were within −3.87% for charging and 0.09% for discharging in heating mode, and 7.08% for charging and 0.13% discharging in cooling mode, respectively. These results highlight the potential of ANN-based approaches for real-time control, forecasting, and digital twin applications in STES systems.

High-intensity focused ultrasound (HIFU) is a therapeutic modality that heats tissue by focusing a sound beam into a narrow, localized region. This paper is concerned with the thermo-optic lensing effect observed by Al-Qraini et al ( Ultrasound Med. Biol. 39 647–59) when visible light was shone at a transparent tissue-mimicking phantom heated by HIFU. Thermal lensing was caused by light refraction as it passed through the thermal gradient region. HIFU thermal lensing was reproduced experimentally and studied analytically using the geometric (eikonal) ray equation to devise a method for temperature measurement. Under the Gaussian thermal field assumption, explicit closed form solutions were found for the forward thermo-optic ray deflection problem, and for the inverse opto-thermal conversion problem that yielded the underlying temperature field from measured ray deflections. Neither temperature calibration nor iterative computations were needed. In the experimental setup, a bundle of thin laser rays illuminated the HIFU-heated spot in a clear tissue-mimicking phantom. The ray deflections were recorded and directly converted into temperature with very good temporal and spatial resolution. These compared reasonably well against the output of an embedded thermocouple (TC)—considering the absorptive and viscous heating artifacts which were also investigated. The TC metallic tip junction was carefully positioned to coincide with the axis of peak heating. It was found that the TC stem (wire) transferred heat by conduction from the tip into the tissue located off the HIFU heating axis. The proposed thermometry method can be useful in elucidating heating from focused ultrasound sources, or from other sources of localized heating such as lasers.