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Background Current guidelines recommend repeat computed tomography (CT) imaging in high-grade blunt renal injury within 48–96 h, yet diagnostic value and clinical significance remain controversial. The aim of this work was to determine the possible gain of CT re-imaging in uncomplicated patients with blunt renal trauma at 48 h after injury, presenting one of the largest case series. Methods A retrospective database of patients admitted to our centre with isolated blunt renal trauma due to sporting injuries was analysed for a period of 20 years (2000–2020). We included only patients who underwent repeat imaging at 48 h after trauma irrespective of AAST renal injury grading (grade 1–5) and initial management. The primary outcome was intervention rates after CT imaging at 48 h in uncomplicated patients versus CT scan at the time of clinical symptoms. Results A total of 280 patients (mean age: 37.8 years; 244 (87.1%) male) with repeat CT after 48 h were included. 150 (53.6%) patients were classified as low-grade (grade 1–3) and 130 (46.4%) as high-grade (grade 4–5) trauma. Immediate intervention at trauma was necessary in 59 (21.1%) patients with high-grade injuries: minimally invasive therapy in 48 (81.4%) and open surgery in 11 (18.6%) patients, respectively. In only 16 (5.7%) cases, intervention was performed based on CT re-imaging at 48 h (low-grade vs. high-grade: 3.3% vs. 8.5%; p  = 0.075). On the contrary, intervention rate due to clinical symptoms was 12.5% (n = 35). Onset of clinical progress was on average (range) 5.3 (1–17) days post trauma. High-grade trauma (odds ratio [OR] grade 4 vs. grade 3 , 14.62;  p  < 0.001; OR grade 5 vs. grade 3 , 22.88, p  = 0.004) and intervention performed at the day of trauma (OR 3.22;  p  = 0.014) were powerful predictors of occurrence of clinical progress. Conclusion Our data suggest that routine CT imaging 48 h post trauma can be safely omitted for patients with low- and high-grade blunt renal injury as long as they remain clinically stable. Patients with high-grade renal injury have the highest risk for clinical progress; thus, close surveillance should be considered especially in this group.

Significance: Fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to distinguish the unique molecular environment of fluorophores. FLIM measures the time a fluorophore remains in an excited state before emitting a photon, and detects molecular variations of fluorophores that are not apparent with spectral techniques alone. FLIM is sensitive to multiple biomedical processes including disease progression and drug efficacy. Aim: We provide an overview of FLIM principles, instrumentation, and analysis while highlighting the latest developments and biological applications. Approach: This review covers FLIM principles and theory, including advantages over intensity-based fluorescence measurements. Fundamentals of FLIM instrumentation in time- and frequency-domains are summarized, along with recent developments. Image segmentation and analysis strategies that quantify spatial and molecular features of cellular heterogeneity are reviewed. Finally, representative applications are provided including high-resolution FLIM of cell- and organelle-level molecular changes, use of exogenous and endogenous fluorophores, and imaging protein-protein interactions with Förster resonance energy transfer (FRET). Advantages and limitations of FLIM are also discussed. Conclusions: FLIM is advantageous for probing molecular environments of fluorophores to inform on fluorophore behavior that cannot be elucidated with intensity measurements alone. Development of FLIM technologies, analysis, and applications will further advance biological research and clinical assessments.

In the present work, a wavelength-selected plasma imaging analysis system is presented and used to track photons emitted from single-trapped nanoparticles in air at atmospheric pressure. The isolated nanoentities were atomized and excited into plasma state using single nanosecond laser pulses. The use of appropriate wavelength filters alongside time-optimized acquisition settings enabled the detection of molecular and atomic emissions in the plasma. The photon detection efficiency of the imaging line resulted in a signal > 400 times larger than the simultaneously-acquired dispersive spectroscopy data. The increase in sensitivity outlined the evolution of diverse physicochemical processes at the single particle scale which included heat and momentum transfer from the plasma into the particle as wells as chemical reactions. The imaging detection of excited fragments evidenced different diffusion kinetics and time frames for atoms and molecules and their influence upon both the spectroscopic emission readout and fabrication processes using the plasma as a reactor. Moreover, the origin of molecular species, whether naturally-occurring or derived from a chemical reaction in the plasma, could also be studied on the basis of compositional gradients found on the images. Limits of detection for the inspected species ranged from tens to hundreds attograms, thus leading to an exceptional sensing principle for single nanoentities that may impact several areas of science and technology.

Significance: 5-Aminolevulinic acid (5-ALA)-based fluorescence guidance in conventional neurosurgical microscopes is limited to strongly fluorescent tumor tissue. Therefore, more sensitive, intrasurgical 5-ALA fluorescence visualization is needed. Aim: Macroscopic fluorescence lifetime imaging (FLIM) was performed ex vivo on 5-ALA-labeled human glioma tissue through a surgical microscope to evaluate its feasibility and to compare it to fluorescence intensity imaging. Approach: Frequency-domain FLIM was integrated into a surgical microscope, which enabled parallel wide-field white-light and fluorescence imaging. We first characterized our system and performed imaging of two samples of suspected low-grade glioma, which were compared to histopathology. Results: Our imaging system enabled macroscopic FLIM of a 6.5  ×  6.5  mm2 field of view at spatial resolutions <20  μm. A frame of 512  ×  512  pixels with a lifetime accuracy <1  ns was obtained in 65 s. Compared to conventional fluorescence imaging, FLIM considerably highlighted areas with weak 5-ALA fluorescence, which was in good agreement with histopathology. Conclusions: Integration of macroscopic FLIM into a surgical microscope is feasible and a promising method for improved tumor delineation.

Significance: In multiphoton microscopy, two-photon excited fluorescence (TPEF) spectra carry valuable information on morphological and functional biological features. For measuring these biomarkers, separation of different parts of the fluorescence spectrum into channels is typically achieved by the use of optical band pass filters. However, spectra from different biomarkers can be unknown or overlapping, creating a crosstalk in between the channels. Previously, establishing these channels relied on prior knowledge or heuristic testing. Aim: The presented method aims to provide spectral bands with optimal separation between groups of specimens expressing different biomarkers. Approach: We have developed a system capable of resolving TPEF with high spectral resolution for the characterization of biomarkers. In addition, an algorithm is created to simulate and optimize optical band pass filters for fluorescence detection channels. To demonstrate the potential improvements in cell and tissue classification using these optimized channels, we recorded spectrally resolved images of cancerous (HT29) and normal epithelial colon cells (FHC), cultivated in 2D layers and in 3D to form spheroids. To provide an example of an application, we relate the results with the widely used redox ratio. Results: We show that in the case of two detection channels, our system and algorithm enable the selection of optimized band pass filters without the need of knowing involved fluorophores. An improvement of 31,5% in separating different 2D cell cultures is achieved, compared to using established spectral bands that assume NAD(P)H and FAD as main contributors of autofluorescence. The compromise is a reduced SNR in the images. Conclusions: We show that the presented method has the ability to improve imaging contrast and can be used to tailor a given label-free optical imaging system using optical band pass filters targeting a specific biomarker or application.

Significance: Research in tissue engineering and in vitro organ formation has recently intensified. To assess tissue morphology, the method of choice today is restricted primarily to histology. Thus novel tools are required to enable noninvasive, and preferably label-free, three-dimensional imaging that is more compatible with futuristic organ-on-a-chip models. Aim: We investigate the potential for using multiphoton microscopy (MPM) as a label-free in vitro approach to monitor calcium-induced epidermal differentiation. Approach: In vitro epidermis was cultured at the air–liquid interface in varying calcium concentrations. Morphology and tissue architecture were investigated using MPM based on visualizing cellular autofluorescence. Results: Distinct morphologies corresponding to epidermal differentiation were observed. In addition, Ca2  +  -induced effects could be distinguished based on the architectural differences in stratification in the tissue cultures. Conclusions: Our study shows that MPM based on cellular autofluorescence enables visualization of Ca2  +  -induced differentiation in epidermal skin models in vitro. The technique has potential to be further adapted as a noninvasive, label-free, and real-time tool to monitor tissue regeneration and organ formation in vitro.

Significance: Sentinel lymph node (SLN) biopsy is an important method for metastasis staging in, e.g., patients with malignant melanoma. Tools enabling prompt histopathological analysis are expected to facilitate diagnostics; optical technologies are explored for this purpose. Aim: The objective of this exploratory study was to investigate the potential of adopting multiphoton laser scanning microscopy (MPM) together with fluorescence lifetime analysis (FLIM) for the examination of lymph node (LN) tissue ex vivo. Approach: Five LN tissue samples (three metastasis positive and two negative) were acquired from a biobank comprising tissues from melanoma patients. Tissues were deparaffinized and subjected to MPM-FLIM using an experimental MPM set-up equipped with a time correlated single photon counting module enabling FLIM. Results: The data confirm that morphological features similar to conventional histology were observed. In addition, FLIM analysis revealed elevated morphological contrast, particularly for discriminating between metastatic cells, lymphocytes, and erythrocytes. Conclusions: Taken together, the results from this investigation show promise for adopting MPM-FLIM in the context of SLN diagnostics and encourage further translational studies on fresh tissue samples.

The editorial introduces the Journal of Biomedical Optics Special Section on Selected Topics in Biophotonics: Fluorescence Lifetime Imaging and Optical Micromechanics.The editorial introduces the Journal of Biomedical Optics Special Section on Selected Topics in Biophotonics: Fluorescence Lifetime Imaging and Optical Micromechanics.

Technological developments in radiation therapy and other cancer therapies have led to a progressive increase in five-year survival rates over the last few decades. Although acute effects have been largely minimized by both technical advances and medical interventions, late effects remain a concern. Indeed, the need to identify those individuals who will develop radiation-induced late effects, and to develop interventions to prevent or ameliorate these late effects is a critical area of radiobiology research. In the last two decades, preclinical studies have clearly established that late radiation injury can be prevented/ameliorated by pharmacological therapies aimed at modulating the cascade of events leading to the clinical expression of radiation-induced late effects. These insights have been accompanied by significant technological advances in imaging that are moving radiation oncology and normal tissue radiobiology from disciplines driven by anatomy and macrostructure to ones in which important quantitative functional, microstructural, and metabolic data can be noninvasively and serially determined. In the current article, we review use of positron emission tomography (PET), single photon emission tomography (SPECT), magnetic resonance (MR) imaging and MR spectroscopy to generate pathophysiological and functional data in the central nervous system, lung, and heart that offer the promise of, (1) identifying individuals who are at risk of developing radiation-induced late effects, and (2) monitoring the efficacy of interventions to prevent/ameliorate them.

Abstract Objective To evaluate the feasibility of recruitment, preliminary efficacy, and acceptability of auricular percutaneous electrical nerve field stimulation (PENFS) for the treatment of fibromyalgia in veterans, using neuroimaging as an outcome measure and a biomarker of treatment response. Design Randomized, controlled, single-blind. Setting Government hospital. Subjects Twenty-one veterans with fibromyalgia were randomized to standard therapy (ST) control or ST with auricular PENFS treatment. Methods Participants received weekly visits with a pain practitioner over 4 weeks. The PENFS group received reapplication of PENFS at each weekly visit. Resting-state functional connectivity magnetic resonance imaging (rs-fcMRI) data were collected within 2 weeks prior to initiating treatment and 2 weeks following the final treatment. Analysis of rs-fcMRI used a right posterior insula seed. Pain and function were assessed at baseline and at 2, 6, and 12 weeks post-treatment. Results At 12 weeks post-treatment, there was a nonsignificant trend toward improved pain scores and significant improvements in pain interference with sleep among the PENFS treatment group as compared with the ST controls. Neuroimaging data displayed increased connectivity to areas of the cerebellum and executive control networks in the PENFS group as compared with the ST control group following treatment. Conclusions There was a trend toward improved pain and function among veterans with fibromyalgia in the ST + PENFS group as compared with the ST control group. Pain and functional outcomes correlated with altered rs-fcMRI network connectivity. Neuroimaging results differed between groups, suggesting an alternative underlying mechanism for PENFS analgesia.