Combining electrochemistry and metallurgy for new electrode designs in Li-ion batteries

To benefit from the large electrochemical capacity advantages offered by Li-driven conversion reactions and to overcome poor kinetics, a new electrode configuration concept is reported. The originality of this electrode design is nested in metallurgical aspects of stainless steel, namely, the appearance of temperature-driven surface microstructures that enable the growth of a nanostructured, electrochemically active, chromium-rich oxide surface layer in close contact with a current collector. The thickness of the oxide layer can reach hundreds of nanometers and is shown to be rooted in the preferential migration of Cr toward the sample surface. We further show that chemical etching of the stainless steel surface, prior to high-temperature annealing, enables reversible capacities as high as 750 mAh/g of chromium-rich oxide for at least 800 cycles. On the basis of modeling, several scenarios involving stainless steel/chromium-based oxides current collectors of various porosities show how this new electrode configuration could boost the electrode capacity beyond that of today's carbon negative electrodes used in Li-ion cells by a factor of 2 or 3. © 2005 American Chemical Society

Fabrication and characterization of a multimodal 3D printed mouse phantom for ionoacoustic quality assurance in image-guided pre-clinical proton radiation research

Objective. Image guidance and precise irradiation are fundamental to ensure the reliability of small animal oncology studies. Accurate positioning of the animal and the in-beam monitoring of the delivered radio-therapeutic treatment necessitate several imaging modalities. In the particular context of proton therapy with a pulsed beam, information on the delivered dose can be retrieved by monitoring the thermoacoustic waves resulting from the brief and local energy deposition induced by a proton beam (ionoacoustics). The objective of this work was to fabricate a multimodal phantom (x-ray, proton, ultrasound, and ionoacoustics) allowing for sufficient imaging contrast for all the modalities. Approach. The phantom anatomical parts were extracted from mouse computed tomography scans and printed using polylactic acid (organs) and a granite/polylactic acid composite (skeleton). The anatomical pieces were encapsulated in silicone rubber to ensure long term stability. The phantom was imaged using x-ray cone-beam computed tomography, proton radiography, ultrasound imaging, and monitoring of a 20 MeV pulsed proton beam using ionoacoustics. Main results. The anatomical parts could be visualized in all the imaging modalities validating the phantom capability to be used for multimodal imaging. Ultrasound images were simulated from the x-ray cone-beam computed tomography and co-registered with ultrasound images obtained before the phantom irradiation and low-resolution ultrasound images of the mouse phantom in the irradiation position, co-registered with ionoacoustic measurements. The latter confirmed the irradiation of a tumor surrogate for which the reconstructed range was found to be in reasonable agreement with the expectation. Significance. This study reports on a realistic small animal phantom which can be used to investigate ionoacoustic range (or dose) verification together with ultrasound, x-ray, and proton imaging. The co-registration between ionoacoustic reconstructions of the impinging proton beam and x-ray imaging is assessed for the first time in a pre-clinical scenario

Enhancement of the ionoacoustic effect through ultrasound and photoacoustic contrast agents

The characteristic depth dose deposition of ion beams, with a maximum at the end of their range (Bragg peak) allows for local treatment delivery, resulting in better sparing of the adjacent healthy tissues compared to other forms of external beam radiotherapy treatments. However, the optimal clinical exploitation of the favorable ion beam ballistic is hampered by uncertainties in the in vivo Bragg peak position. Ionoacoustics is based on the detection of thermoacoustic pressure waves induced by a properly pulsed ion beam (e.g., produced by modern compact accelerators) to image the irradiated volume. Co-registration between ionoacoustics and ultrasound imaging offers a promising opportunity to monitor the ion beam and patient anatomy during the treatment. Nevertheless, the detection of the ionoacoustic waves is challenging due to very low pressure amplitudes and frequencies (mPa/kHz) observed in clinical applications. We investigate contrast agents to enhance the acoustic emission. Ultrasound microbubbles are used to increase the ionoacoustic frequency around the microbubble resonance frequency. Moreover, India ink is investigated as a possible mean to enhance the signal amplitude by taking advantage of additional optical photon absorption along the ion beam and subsequent photoacoustic effect. We report amplitude increase of up to 200% of the ionoacoustic signal emission in the MHz frequency range by combining microbubbles and India ink contrast agents

Experimental demonstration of accurate Bragg peak localization with ionoacoustic tandem phase detection (iTPD).

Accurate knowledge of the exact stopping location of ions inside the patient would allow full exploitation of their ballistic properties for patient treatment. The localized energy deposition of a pulsed particle beam induces a rapid temperature increase of the irradiated volume and leads to the emission of ionoacoustic (IA) waves. Detecting the time-of-flight (ToF) of the IA wave allows inferring information on the Bragg peak location and can henceforth be used for in-vivo range verification. A challenge for IA is the poor signal-to-noise ratio at clinically relevant doses and viable machines. We present a frequency-based measurement technique, labeled as ionoacoustic tandem phase detection (iTPD) utilizing lock-in amplifiers. The phase shift of the IA signal to a reference signal is measured to derive the ToF. Experimental IA measurements with a 3.5 MHz lead zirconate titanate (PZT) transducer and lock-in amplifiers were performed in water using 22 MeV proton bursts. A digital iTPD was performed in-silico at clinical dose levels on experimental data obtained from a clinical facility and secondly, on simulations emulating a heterogeneous geometry. For the experimental setup using 22 MeV protons, a localization accuracy and precision obtained through iTPD deviates from a time-based reference analysis by less than 15 mu m. Several methodological aspects were investigated experimentally in systematic manner. Lastly, iTPD was evaluated in-silico for clinical beam energies indicating that iTPD is in reach of sub-mm accuracy for fractionated doses < 5 Gy. iTPD can be used to accurately measure the ToF of IA signals online via its phase shift in frequency domain. An application of iTPD to the clinical scenario using a single pulsed beam is feasible but requires further development to reach <1 Gy detection capabilities