We developed a novel platform of self-powered radiation sensors based on high-energy electron currents in multi-layer thin-film geometry. A periodic structure of N elemental modules consisting of (high-Z electrode/nano-porous aerogel/low-Z electrode) layers was investigated. 10 and 50 μm thick high-Z (Cu, Ta) and low-Z (Al) electrodes were separated by 50 μm thick polyimide aerogel insulating films. Sensors were tested with 120 kV, 2.5 MV and 6 MV x-rays. The sensors’ characteristics were investigated by obtaining current-voltage (IV) curves for different low-Z/high-Z electrode combinations. Experimentally measured currents from each electrode were compared to radiation transport simulations using the CEPXS/ONEDANT computer model with nanometer-to-micrometer spatial resolution. The main features of the IV-curves are: (a) non-zero current at zero external voltage bias (b) S-like shape at small voltages, and (c) a linear increase of current dominant at large voltages. Signals scale with the total effective area of all electrodes, as well as the number of electrodes and their thicknesses. The yield of a multi-element sensor made with N = 10 elemental modules (10 μm-thick Ta) compared to a single N = 1 (double N = 2) elemental module (made with 50 μm-thick Ta layers) reveals an increase of the total signal of about 4.3 (2.9) times for 6 MV beam and 8.2 (5.8) times for 120kVp. Beam attenuation in the detector is about 0.5%, 3% and 46% respectively for 6 MV, 2,5 MV and 120kVp beams per single elemental structure with 50 μm Ta. We investigated the characteristics of aerogel-based high-energy current x-ray detectors in multi-layered configurations. We envision its implementation for real-time monitoring of radiation dose/flux in areas of homeland security, interventional radiology and radiotherapy.

Purpose We developed a new class of aerogel‐based thin‐film self‐powered radiation sensors employing high‐energy electron current (HEC) in periodic multilayer (high‐Z | polyimide aerogel (PA) | low‐Z) electrode microstructures. Materials Low‐Z (Al) and high‐Z (Ta) electrodes were deposited on 50 μm‐thick PA films to obtain sensors with Al‐PA‐Ta‐PA‐Al structures. Sensors were tested with x rays in the 40–120 kVp range and with 2.5 MV, 6 MV, and 6 MV‐FFF linac beams (TrueBeam, Varian). Performance of PA‐HEC sensors was compared to commercial A12 Farmer ionization chamber as well as to radiation transport simulations using CEPXS/ONEDANT with nanometer‐to‐micrometer spatial resolution. The computations included periodic and single‐element structures N x (Al‐PA‐Ta‐PA‐Al) with variable layer thicknesses. Results Signal from PA‐HEC sensors was proportional to the simulated net leakage electron current (averaged over the PA thickness). Experimental response was linear with dose and independent of dose rate. Detector responses to different x‐ray sources show higher signals for kVp photon energies, as expected, though a strong signal was obtained for MV energies as well. The signal scaled with total effective area inside the multielemental structures; for example, the yield of a multielement sensor made with 20 Ta layers compared to a single‐element structure with 1 Ta layer of the same total thickness of Ta was 10 times greater for 6 MV beam and 23 times greater for 120 kVp. Beam attenuation per element in the detector was 0.5%, 1%, 3%, and 46%, respectively for 6 MV, 6 MV FFF, 2.5 MV, and 120 kVp. Conclusion We demonstrated the feasibility of aerogel‐based multilayer HEC radiation detector and its application for flux/dose monitoring of kVp and radiotherapy MV beams with small beam attenuation.

Purpose: Demonstrate the advantages of two novel x‐ray tube‐insert designs to overcome tube output limitations for high‐resolution, small field‐of‐view (FOV) angiographic imaging. Methods: High‐spatial resolution with a small focal spot (sfs) is achievable with the microangiographic (MA) detector that we have developed. The two designs explored are a non‐offset design, and an offset design. Both tube‐insert designs include two filaments, L1 and L2, and two focal target tracks. L1 corresponds to an 8° anode region to produce a medium effective focal spot (mfs) to be used with the standard FOV flat‐panel detector (FPD). L2 corresponds to a 2° anode region to produce a small effective focal spot (sfs) to be used with the smaller FOV MA detector, while providing comparable x‐ray output. The non‐offset design has the sfs region closer to the anode rotation axis, and mfs region farther from the axis. The offset design has the mfs region closer to the rotation axis, and sfs region farther from the rotation axis. The sfs region of the offset design has a greater anode track diameter which may further increase output capability. However, in order to avoid limitations on the mfs FOV in this design, the sfs target region of the anode is offset in the anode cathode direction. The geometries of both designs are illustrated and compared. Results: It is shown that the new designs enable increased tube output for the sfs when used with a small FOV detector, while also allowing for increased FOV with the standard FPD and the mfs. Conclusion: A dual track, dual filament x‐ray tube‐insert design provides increased output capability over a small FOV, while enabling an mfs to be used with the lower resolution standard FPD. Toshiba Medical Systems Corp

Ischemic heart disease is a common pro-arrhythmic condition characterized by hypoxia, acidosis, hyperkalemia and impaired Ca(2þ) handling. Here we investigated the ischemia responses to acute hypoxia and acidification in developing cardiomyocytes derived from neonatal rat hearts (rN-CM) or human induced pluripotent stem cells. L-type Ca(2þ) current (I Ca ) was measured