Single-Pulse X-ray Acoustic Computed Tomographic Imaging for Precision Radiation Therapy.

Purpose: High-precision radiation therapy is crucial for cancer treatment. Currently, the delivered dose can only be verified via simulations with phantoms, and an in-tumor, online dose verification is still unavailable. An innovative detection method called x-ray-induced acoustic computed tomography (XACT) has recently shown the potential for imaging the delivered radiation dose within the tumor. Prior XACT imaging systems have required tens to hundreds of signal averages to achieve high-quality dose images within the patient, which reduces its real-time capability. Here, we demonstrate that XACT dose images can be reproduced from a single x-ray pulse (4 µs) with sub-mGy sensitivity from a clinical linear accelerator. Methods and Materials: By immersing an acoustic transducer in a homogeneous medium, it is possible to detect pressure waves generated by the pulsed radiation from a clinical linear accelerator. After rotating the collimator, signals of different angles are obtained to perform a tomographic reconstruction of the dose field. Using 2-stage amplification with further bandpass filtering increases the signal-to-noise ratio (SNR). Results: Acoustic peak SNR and voltage values were recorded for singular and dual-amplifying stages. The SNR for single-pulse mode was able to satisfy the Rose criterion, and the collected signals were able to reconstruct 2-dimensional images from the 2 homogeneous media. Conclusions: By overcoming the low SNR and requirement of signal averaging, single-pulse XACT imaging holds great potential for personalized dose monitoring from each individual pulse during radiation therapy.

Single pulse protoacoustic range verification using a clinical synchrocyclotron.

Objective.Proton therapy as the next generation radiation-based cancer therapy offers dominant advantages over conventional radiation therapy due to the utilization of the Bragg peak; however, range uncertainty in beam delivery substantially mitigates the advantages of proton therapy. This work reports using protoacoustic measurements to determine the location of proton Bragg peak deposition within a water phantom in real time during beam delivery.Approach.In protoacoustics, proton beams have a definitive range, depositing a majority of the dose at the Bragg peak; this dose is then converted to heat. The resulting thermoelastic expansion generates a 3D acoustic wave, which can be detected by acoustic detectors to localize the Bragg peak.Main results.Protoacoustic measurements were performed with a synchrocyclotron proton machine over the exhaustive energy range from 45.5 to 227.15 MeV in clinic. It was found that the amplitude of the acoustic waves is proportional to proton dose deposition, and therefore encodes dosimetric information. With the guidance of protoacoustics, each individual proton beam (7 pC/pulse) can be directly visualized with sub-millimeter (<0.7 mm) resolution using single beam pulse for the first time.Significance.The ability to localize the Bragg peak in real-time and obtain acoustic signals proportional to dose within tumors could enable precision proton therapy and hope to progress towardsin vivomeasurements.

A General Method for High-Performance Li-Ion Battery Electrodes from Colloidal Nanoparticles without the Introduction of Binders or Conductive-Carbon Additives: The Cases of MnS, Cu(2-x)S, and Ge.

In this work, we demonstrate a general lithium-ion battery electrode fabrication method for colloidal nanoparticles (NPs) using electrophoretic deposition (EPD). Our process is capable of forming robust electrodes from copper sulfide, manganese sulfide, and germanium NPs without the use of additives such as polymeric binders and conductive agents. After EPD, we show two postprocessing treatments ((NH4)2S and inert atmosphere heating) to effectively remove surfactant ligands and create a linked network of particles. The NP films fabricated by this simple process exhibit excellent electrochemical performance as lithium-ion battery electrodes. Additive-free Cu(2-x)S and MnS NP films show well-defined plateaus at ∼1.7 V, demonstrating potential for use as cathode electrodes. Because of the absence of additives in the NP film, this additive-free NP film is an ideal template for ex situ analyses of the particles to track particle morphology changes and deterioration as a result of Li ion cycling. To this end, we perform a size-dependent investigation of Cu(2-x)S NPs and demonstrate that there is no significant relationship between size and capacity when comparing small (3.8 nm), medium (22 nm), and large (75 nm) diameter Cu(2-x)S NPs up to 50 cycles; however, the 75 nm NPs show higher Coulombic efficiency. Ex situ TEM analysis suggests that Cu(2-x)S NPs eventually break into smaller particles (<10 nm), explaining a weak correlation between size and performance. We also report for the first time on additive-free Ge NP films, which show stable capacities for up to 50 cycles at 750 mAh/g.