Multipass wide-field phase imager

Advances in optical imaging always look for an increase in sensitivity and resolution among other practicability aspects. Within the same scope, in this work we report a versatile interference contrast imaging technique, with high phase sensitivity and a large field-of-view of several mm2. Sensitivity is increased through the use of a self-imaging non-resonant cavity, which causes photons to probe the sample in multiple rounds before being detected, where the configuration can be transmissive or reflective. Phase profiles can be resolved individually for each round thanks to a specially designed single-photon camera with time-of-flight capabilities and true pixels-off gating. Measurement noise is reduced by novel data processing combining the retrieved sample profiles from multiple rounds. Our protocol is especially useful under extremely low light conditions as required by biological or photo-sensitive samples. Results demonstrate more than a four-fold reduction in phase measurement noise, compared to single round imaging, and values close to the predicted sensitivity in case of the best possible cavity configuration, where all photons are maintained until n rounds. We also find good agreement with the theoretical predictions for low number of rounds, where experimental imperfections would play a minor role. The absence of a laser or cavity lock-in mechanism makes the technique an easy to use inspection tool

Spatially Resolved Event-Driven 24 × 24 Pixels SPAD Imager with 100% Duty Cycle for Low Optical Power Quantum Entanglement Detection

Quantum microscopy requires efficient detectors able to identify temporal correlations among photons. Photon coincidences are usually detected by postprocessing their timestamps measured by means of time-To-digital converters (TDCs), through a time and power-consuming procedure, which impairs the overall system performance. In this article, we propose an innovative single-photon sensitive imager based on single-photon avalanche diodes (SPADs), able to signal coincident photon pairs along with their position through a TDC-free, event-driven architecture. The result is a highly efficient detector (25.8%) with a 100% duty cycle and minimized data throughput. The modular architecture and the 330 ns readout time, independent of pixel number, pave the way to large format imagers based on the same paradigm. The detector enabled quantum imaging at extremely low, microwatt-level optical pump powers, four orders of magnitude lower than previous experiments with similar optical setups

Observation of near-infrared sub-Poissonian photon emission in hexagonal boron nitride at room temperature

© 2020 Author(s). The generation of non-classical light states in the near-infrared (NIR) is important for a number of photonic quantum technologies. Here, we report the first experimental observation of sub-Poissonian NIR (1.24 eV) light emission from defects in a 2D hexagonal boron nitride (hBN) sheet at room temperature. Photoluminescence statistics shows g(2)(0) = 0.6, which is a signature of the quantum nature of the emission. Density functional-theory calculations, at the level of the generalized gradient approximation, for the negatively charged nitrogen anti-site lattice defects are consistent with the observed emission energy. This work demonstrates that the defects in hBN could be a promising platform for single-photon generation in the NIR

Transrectal Prostate Biopsy and Fiducial Marker Placement in a Standart 1.5T Magnetic Resonance Imaging Scanner

Cataloged from PDF version of article.Purpose: We investigated the accuracy and feasibility of a system that provides transrectal needle access to the prostate concurrent with 1.5 Tesla MRI which previously has not been possible. Materials and Methods: In 5 patients with previously diagnosed prostate cancer, MRI guided intraprostatic placement of gold fiducial markers (4 procedures) and/or prostate biopsy (3 procedures) was performed using local anesthesia. Results: Mean procedure duration was 76 minutes and all patients tolerated the intervention well. Procedure related adverse events included self-limited hematuria and hematochezia following 3 of 8 procedures (all resolved in less than 1 week). Mean needle placement accuracy was 1.9 mm for the fiducial marker placement studies and 1.8 mm for the biopsy procedures. Mean fiducial marker placement accuracy was 4.8 mm and the mean fiducial marker placement accuracy transverse to the needle direction was 2.6 mm. All patients who underwent the procedure were able to complete their course of radiotherapy without delay or complication. Conclusions: While studies of clinical usefulness are warranted, transrectal 1.5 T MRI guided prostate biopsy and fiducial marker placement is feasible using this system, providing new opportunities for image guided diagnostic and therapeutic prostate interventions

Quantum light transport in phase-separated Anderson localization fiber

Anderson localization, a strong localization effect that prevents wave diffusion, is fundamentally important in manipulating wave propagation in a disordered medium. This work uses a phase separated glass Anderson localization optical fiber and demonstrates quantum light transport, which shows the potential for transmission of high dimensional quantum information, thereby enabling quantum imaging and quantum communication applications.Propagation of light by Anderson localization has been demonstrated in micro-nano-structured fibers. In this work, we introduce a phase separated glass Anderson localization optical fiber for quantum applications. By using a spontaneous parametric down-conversion source, multi-photon detection with a single-photon avalanche diode array camera, and signal post-processing techniques, we demonstrate quantum light transport, where spatial correlations between photon pairs are preserved after propagation. In order to better understand and improve light transport, we study light localization, observing a dependence on wavelength. Our results indicate that the proposed phase separated fiber may become an effective platform for quantum imaging and communication

Early observed transient prostate-specific antigen elevations on a pilot study of external beam radiation therapy and fractionated MRI guided High Dose Rate brachytherapy boost

PURPOSE: To report early observation of transient PSA elevations on this pilot study of external beam radiation therapy and magnetic resonance imaging (MRI) guided high dose rate (HDR) brachytherapy boost. MATERIALS AND METHODS: Eleven patients with intermediate-risk and high-risk localized prostate cancer received MRI guided HDR brachytherapy (10.5 Gy each fraction) before and after a course of external beam radiotherapy (46 Gy). Two patients continued on hormones during follow-up and were censored for this analysis. Four patients discontinued hormone therapy after RT. Five patients did not receive hormones. PSA bounce is defined as a rise in PSA values with a subsequent fall below the nadir value or to below 20% of the maximum PSA level. Six previously published definitions of biochemical failure to distinguish true failure from were tested: definition 1, rise >0.2 ng/mL; definition 2, rise >0.4 ng/mL; definition 3, rise >35% of previous value; definition 4, ASTRO defined guidelines, definition 5 nadir + 2 ng/ml, and definition 6, nadir + 3 ng/ml. RESULTS: Median follow-up was 24 months (range 18–36 mo). During follow-up, the incidence of transient PSA elevation was: 55% for definition 1, 44% for definition 2, 55% for definition 3, 33% for definition 4, 11% for definition 5, and 11% for definition 6. CONCLUSION: We observed a substantial incidence of transient elevations in PSA following combined external beam radiation and HDR brachytherapy for prostate cancer. Such elevations seem to be self-limited and should not trigger initiation of salvage therapies. No definition of failure was completely predictive

DNMT (DNA methyltransferase) inhibitors radiosensitize human cancer cells by suppressing DNA repair activity

<p>Abstract</p> <p>Background</p> <p>Histone modifications and DNA methylation are two major factors in epigenetic phenomenon. Unlike the histone deacetylase inhibitors, which are known to exert radiosensitizing effects, there have only been a few studies thus far concerning the role of DNA methyltransferase (DNMT) inhibitors as radiosensitizers. The principal objective of this study was to evaluate the effects of DNMT inhibitors on the radiosensitivity of human cancer cell lines, and to elucidate the mechanisms relevant to that process.</p> <p>Methods</p> <p>A549 (lung cancer) and U373MG (glioblastoma) cells were exposed to radiation with or without six DNMT inhibitors (5-azacytidine, 5-aza-2'-deoxycytidine, zebularine, hydralazine, epigallocatechin gallate, and psammaplin A) for 18 hours prior to radiation, after which cell survival was evaluated via clonogenic assays. Cell cycle and apoptosis were analyzed via flow cytometry. Expressions of DNMT1, 3A/3B, and cleaved caspase-3 were detected via Western blotting. Expression of γH2AX, a marker of radiation-induced DNA double-strand break, was examined by immunocytochemistry.</p> <p>Results</p> <p>Pretreatment with psammaplin A, 5-aza-2'-deoxycytidine, and zebularine radiosensitized both A549 and U373MG cells. Pretreatment with psammaplin A increased the sub-G1 fraction of A549 cells, as compared to cells exposed to radiation alone. Prolongation of γH2AX expression was observed in the cells treated with DNMT inhibitors prior to radiation as compared with those treated by radiation alone.</p> <p>Conclusions</p> <p>Psammaplin A, 5-aza-2'-deoxycytidine, and zebularine induce radiosensitivity in both A549 and U373MG cell lines, and suggest that this effect might be associated with the inhibition of DNA repair.</p

Downregulation of Homologous Recombination DNA Repair Genes by HDAC Inhibition in Prostate Cancer Is Mediated through the E2F1 Transcription Factor

Histone deacetylase inhibitors (HDACis) re-express silenced tumor suppressor genes and are currently undergoing clinical trials. Although HDACis have been known to induce gene expression, an equal number of genes are downregulated upon HDAC inhibition. The mechanism behind this downregulation remains unclear. Here we provide evidence that several DNA repair genes are downregulated by HDAC inhibition and provide a mechanism involving the E2F1 transcription factor in the process.Applying Analysis of Functional Annotation (AFA) on microarray data of prostate cancer cells treated with HDACis, we found a number of genes of the DNA damage response and repair pathways are downregulated by HDACis. AFA revealed enrichment of homologous recombination (HR) DNA repair genes of the BRCA1 pathway, as well as genes regulated by the E2F1 transcription factor. Prostate cancer cells demonstrated a decreased DNA repair capacity and an increased sensitization to chemical- and radio-DNA damaging agents upon HDAC inhibition. Recruitment of key HR repair proteins to the site of DNA damage, as well as HR repair capacity was compromised upon HDACi treatment. Based on our AFA data, we hypothesized that the E2F transcription factors may play a role in the downregulation of key repair genes upon HDAC inhibition in prostate cancer cells. ChIP analysis and luciferase assays reveal that the downregulation of key repair genes is mediated through decreased recruitment of the E2F1 transcription factor and not through active repression by repressive E2Fs.Our study indicates that several genes in the DNA repair pathway are affected upon HDAC inhibition. Downregulation of the repair genes is on account of a decrease in amount and promoter recruitment of the E2F1 transcription factor. Since HDAC inhibition affects several pathways that could potentially have an impact on DNA repair, compromised DNA repair upon HDAC inhibition could also be attributed to several other pathways besides the ones investigated in this study. However, our study does provide insights into the mechanism that governs downregulation of HR DNA repair genes upon HDAC inhibition, which can lead to rationale usage of HDACis in the clinics

Targeting the epigenome: effects of epigenetic treatment strategies on genomic stability in healthy human cells

Epigenetic treatment concepts have long been ascribed as being tumour-selective. Over the last decade, it has become evident that epigenetic mechanisms are essential for a wide range of intracellular functions in healthy cells as well. Evaluation of possible side-effects and their underlying mechanisms in healthy human cells is necessary in order to improve not only patient safety, but also to support future drug development. Since epigenetic regulation directly interacts with genomic and chromosomal packaging density, increasing genomic instability may be a result subsequent to drug-induced epigenetic modifications. This review highlights past and current research efforts on the influence of epigenetic modification on genomic stability in healthy human cells