-
Radiotherapy and Oncology : Journal of... Jun 2024To investigate quality assurance (QA) techniques for in vivo dosimetry and establish its routine uses for proton FLASH small animal experiments with a saturated monitor...
PURPOSE
To investigate quality assurance (QA) techniques for in vivo dosimetry and establish its routine uses for proton FLASH small animal experiments with a saturated monitor chamber.
METHODS AND MATERIALS
227 mice were irradiated at FLASH or conventional (CONV) dose rates with a 250 MeV FLASH-capable proton beamline using pencil beam scanning to characterize the proton FLASH effect on abdominal irradiation and examining various endpoints. A 2D strip ionization chamber array (SICA) detector was positioned upstream of collimation and used for in vivo dose monitoring during irradiation. Before each irradiation series, SICA signal was correlated with the isocenter dose at each delivered dose rate. Dose, dose rate, and 2D dose distribution for each mouse were monitored with the SICA detector.
RESULTS
Calibration curves between the upstream SICA detector signal and the delivered dose at isocenter had good linearity with minimal R values of 0.991 (FLASH) and 0.985 (CONV), and slopes were consistent for each modality. After reassigning mice, standard deviations were less than 1.85 % (FLASH) and 0.83 % (CONV) for all dose levels, with no individual subject dose falling outside a ± 3.6 % range of the designated dose. FLASH fields had a field-averaged dose rate of 79.0 ± 0.8 Gy/s and mean local average dose rate of 160.6 ± 3.0 Gy/s. In vivo dosimetry allowed for the accurate detection of variation between the delivered and the planned dose.
CONCLUSION
In vivo dosimetry benefits FLASH experiments through enabling real-time dose and dose rate monitoring allowing mouse cohort regrouping when beam fluctuation causes delivered dose to vary from planned dose.
PubMed: 38942121
DOI: 10.1016/j.radonc.2024.110404 -
Nature Communications Jun 2024Understanding spin-lattice interactions in antiferromagnets is a critical element of the fields of antiferromagnetic spintronics and magnonics. Recently, coherent...
Understanding spin-lattice interactions in antiferromagnets is a critical element of the fields of antiferromagnetic spintronics and magnonics. Recently, coherent nonlinear phonon dynamics mediated by a magnon state were discovered in an antiferromagnet. Here, we suggest that a strongly coupled two-magnon-one phonon state in this prototypical system opens a novel pathway to coherently control magnon-phonon dynamics. Utilizing intense narrow-band terahertz (THz) pulses and tunable magnetic fields up to μH = 7 T, we experimentally realize the conditions of magnon-phonon Fermi resonance in antiferromagnetic CoF. These conditions imply that both the spin and the lattice anharmonicities harvest energy from the transfer between the subsystems if the magnon eigenfrequency f is half the frequency of the phonon 2f = f. Performing THz pump-infrared probe spectroscopy in conjunction with simulations, we explore the coupled magnon-phonon dynamics in the vicinity of the Fermi-resonance and reveal the corresponding fingerprints of nonlinear interaction facilitating energy exchange between these subsystems.
PubMed: 38942783
DOI: 10.1038/s41467-024-49716-w -
EJNMMI Physics Jun 2024For dosimetry, the demand for whole-body SPECT/CT imaging, which require long acquisition durations with dual-head Anger cameras, is increasing. Here we evaluated...
BACKGROUND
For dosimetry, the demand for whole-body SPECT/CT imaging, which require long acquisition durations with dual-head Anger cameras, is increasing. Here we evaluated sparsely acquired projections and assessed whether the addition of deep-learning-generated synthetic intermediate projections (SIPs) could improve the image quality while preserving dosimetric accuracy.
METHODS
This study included 16 patients treated with Lu-DOTATATE with SPECT/CT imaging (120 projections, 120P) at four time points. Deep neural networks (CUSIPs) were designed and trained to compile 90 SIPs from 30 acquired projections (30P). The 120P, 30P, and three different CUSIP sets (30P + 90 SIPs) were reconstructed using Monte Carlo-based OSEM reconstruction (yielding 120P_rec, 30P_rec, and CUSIP_recs). The noise levels were visually compared. Quantitative measures of normalised root mean square error, normalised mean absolute error, peak signal-to-noise ratio, and structural similarity were evaluated, and kidney and bone marrow absorbed doses were estimated for each reconstruction set.
RESULTS
The use of SIPs visually improved noise levels. All quantitative measures demonstrated high similarity between CUSIP sets and 120P. Linear regression showed nearly perfect concordance of the kidney and bone marrow absorbed doses for all reconstruction sets, compared to the doses of 120P_rec (R ≥ 0.97). Compared to 120P_rec, the mean relative difference in kidney absorbed dose, for all reconstruction sets, was within 3%. For bone marrow absorbed doses, there was a higher dissipation in relative differences, and CUSIP_recs outperformed 30P_rec in mean relative difference (within 4% compared to 9%). Kidney and bone marrow absorbed doses for 30P_rec were statistically significantly different from those of 120_rec, as opposed to the absorbed doses of the best performing CUSIP_rec, where no statistically significant difference was found.
CONCLUSION
When performing SPECT/CT reconstruction, the use of SIPs can substantially reduce acquisition durations in SPECT/CT imaging, enabling acquisition of multiple fields of view of high image quality with satisfactory dosimetric accuracy.
PubMed: 38941040
DOI: 10.1186/s40658-024-00655-x -
ACS Nano Jun 2024The optimization of nanoscale optical devices and structures will enable the exquisite control of planar optical fields. Polariton manipulation is the primary strategy...
The optimization of nanoscale optical devices and structures will enable the exquisite control of planar optical fields. Polariton manipulation is the primary strategy in play. In two-dimensional heterostructures, the ability to excite mixed optical modes offers an additional control in device design. Phonon polaritons in hexagonal boron nitride have been a common system explored for the control of near-infrared radiation. Their hybridization with graphene plasmons makes these mixed phonon polariton modes in hexagonal boron nitride more appealing in terms of enabling active control of electrodynamic properties with a reduction of propagation losses. Optical resonators can be added to confine these hybridized plasmon-phonon polaritons deeply into the subwavelength regime, with these structures featuring high quality factors. Here, we show a scalable approach for the design and fabrication of heterostructure nanodisc resonators patterned in chemical vapor deposition-grown monolayer graphene and -BN sheets. Real-space mid-infrared nanoimaging reveals the nature of hybridized polaritons in the heterostructures. We simulate and experimentally demonstrate localized hybridized polariton modes in heterostructure nanodisc resonators and demonstrate that those nanodiscs can collectively couple to the waveguide. High quality factors for the nanodiscs are measured with nanoscale Fourier transform infrared spectroscopy. Our results offer practical strategies to realize scalable nanophotonic devices utilizing low-loss hybridized polaritons for applications such as on-chip optical components.
PubMed: 38940269
DOI: 10.1021/acsnano.3c13047 -
Frontiers in Bioscience (Landmark... May 2024Circadian rhythms, the natural cycles of physical, mental, and behavioral changes that follow a roughly 24-hour cycle, are known to have a profound effect on the human... (Review)
Review
Circadian rhythms, the natural cycles of physical, mental, and behavioral changes that follow a roughly 24-hour cycle, are known to have a profound effect on the human body. Light plays an important role in the regulation of circadian rhythm in human body. When light from the outside enters the eyes, cones, rods, and specialized retinal ganglion cells receive the light signal and transmit it to the suprachiasmatic nucleus of the hypothalamus. The central rhythm oscillator of the suprachiasmatic nucleus regulates the rhythm oscillator of tissues all over the body. Circadian rhythms, the natural cycles of physical, mental, and behavioral changes that follow a roughly 24-hour cycle, are known to have a profound effect on the human body. As the largest organ in the human body, skin plays an important role in the peripheral circadian rhythm regulation system. Like photoreceptor cells in the retina, melanocytes express opsins. Studies show that melanocytes in the skin are also sensitive to light, allowing the skin to "see" light even without the eyes. Upon receiving light signals, melanocytes in the skin release hormones that maintain homeostasis. This process is called "photoneuroendocrinology", which supports the health effects of light exposure. However, inappropriate light exposure, such as prolonged work in dark environments or exposure to artificial light at night, can disrupt circadian rhythms. Such disruptions are linked to a variety of health issues, emphasizing the need for proper light management in daily life. Conversely, harnessing light's beneficial effects through phototherapy is gaining attention as an adjunctive treatment modality. Despite these advancements, the field of circadian rhythm research still faces several unresolved issues and emerging challenges. One of the most exciting prospects is the use of the skin's photosensitivity to treat diseases. This approach could revolutionize how we think about and manage various health conditions, leveraging the skin's unique ability to respond to light for therapeutic purposes. As research continues to unravel the complexities of circadian rhythms and their impact on health, the potential for innovative treatments and improved wellbeing is immense.
Topics: Humans; Circadian Rhythm; Animals; Light; Signal Transduction
PubMed: 38940028
DOI: 10.31083/j.fbl2906206 -
ACS Sustainable Chemistry & Engineering Jun 2024Understanding the properties of polymers, such as their crystallinity, is crucial for their material performance and predicting their behavior during and after use,...
Understanding the properties of polymers, such as their crystallinity, is crucial for their material performance and predicting their behavior during and after use, especially in the case of environmentally friendly (bio)degradable polymers, enabling optimized design. In this work, for the first time, a pressure-induced condis crystal-like mesophase of poly(butylene succinate--butylene adipate) (PBSA) is presented. The phase behavior of pressed films obtained from commercial PBSA with 25% butylene adipate units is investigated at various processing temperatures from room temperature to 100 °C, pressed at a pressure of the press jaws and at 2-5 t for 1-5 min. The characterization and quantification evaluation of the condis crystal-like mesophase of pressed PBSA formed at temperatures above the glass transition is investigated by X-ray diffraction, polarized optical microscopy (POM), and differential scanning calorimetry (DSC) methods. Our results demonstrate that pressed PBSA films at 60 °C show a condis crystal-like mesophase, characterized by the presence of reflections at wide angles, birefringence by POM, as well as a higher melting point (endotherm) by DSC. The resulting oriented mesomorphic green polymer can, in a sustainable manner, expand further technological applications of (bio)degradable polymers, especially in the medical field, and open up opportunities for further research that could provide such polymers with tailored persistence and degradation, thus changing the shelf life.
PubMed: 38939870
DOI: 10.1021/acssuschemeng.4c03285 -
JACC. Advances Apr 2024Exposure to ionizing radiation is an inherent occupational health hazard in clinical cardiology. Health risks have been reported previously, including predilection to... (Review)
Review
Exposure to ionizing radiation is an inherent occupational health hazard in clinical cardiology. Health risks have been reported previously, including predilection to cancer. In addition, orthopedic injury due to prolonged wearing of heavy protective lead aprons, which are mandatory to reduce radiation risk, have been extensively documented. Cardiology as a specialty has grown with rising volumes of increasingly complex procedures. This includes electrophysiological, coronary, and structural intervention, advanced heart failure/transplant management, and diagnostic imaging. Both the operator as well imaging specialists are exposed to radiation, particularly in structural interventions where interventional cardiologists and structural imagers work closely. Increasingly, women interested in cardiology may deselect the field due to radiation concerns. This expert document highlights the risks of radiation exposure in cardiology, including practical tips within various subspecialty fields such as interventional/structural cardiology, electrophysiology, imaging, advanced heart failure, and pediatric cardiology.
PubMed: 38939686
DOI: 10.1016/j.jacadv.2024.100863 -
Annals of Laparoscopic and Endoscopic... Jan 2024Flaps and grafts are used for filling dead space, ureteral substitution, and as mesh alternatives. The surgical robot is invaluable in urologic reconstructive surgery...
BACKGROUND AND OBJECTIVE
Flaps and grafts are used for filling dead space, ureteral substitution, and as mesh alternatives. The surgical robot is invaluable in urologic reconstructive surgery due to the ability of the robot to reach the deep pelvis, its minimally invasive access, the ability to use indocyanine green to identify structures and assess tissue perfusion and viability, and ergonomics for the surgeon. Robotic reconstruction can involve tissue transfer in the form of flaps and grafts to provide form and function to organs that have been damaged by iatrogenic injuries, trauma, infections, cancer, radiation injury, or congenital abnormalities. Common flaps and grafts can be readily adapted to the robotic approach. In this literature review, we examine the robotic use of flaps and grafts in reconstructive urology.
METHODS
A thorough literature review was conducted via a PubMed search for predefined terms.
KEY CONTENT AND FINDINGS
Flaps and grafts in reconstructive urology are used for interposition, ureteral substitution, and as mesh alternatives. Omental flaps are used for tissue interposition, or to provide structure and nutrients, and are easily employed with the robot. Various robotic applications of peritoneal flaps have been described. Vascular rectus abdominis musculocutaneous flaps are well-vascularized flaps that occupy dead space and provide structural support, which can be harvested readily with the robot. Sigmoid epiploica are an excellent flap for pelvic reconstruction. Gracilis flaps and fascia lata grafts are well-tolerated and provide space occupying tissue. Boari flaps aid in robotic ureteral reconstruction, especially in the setting of long defects. Oral mucosa is excellent for ureteral or bladder neck reconstruction. Rectal mucosa is well-tolerated and easy to harvest robotically for a variety of urinary tract reconstructive applications. The appendix or ileum can be interposed for repair of damaged ureters.
CONCLUSIONS
Various flaps and grafts have been adapted for robotic reconstructive urology. As the field develops, refinement of techniques and innovation in flaps and employment of the robot will propel this field forward. More studies, especially comparative studies, are needed to elucidate the flaps and grafts that are most likely to be successful with the least morbidity for each use case.
PubMed: 38938988
DOI: 10.21037/ales-23-36 -
Frontiers in Psychiatry 2024Aberrant fixation and scan paths in visual searches have been repeatedly reported in schizophrenia. The frontal eye fields (FEF) and thalamus may be responsible for...
INTRODUCTION
Aberrant fixation and scan paths in visual searches have been repeatedly reported in schizophrenia. The frontal eye fields (FEF) and thalamus may be responsible for fixation and scan paths. These two regions are connected by superior thalamic radiation (STR) in humans. Studies have reported reduced fixation numbers and shortened scan path lengths in individuals with attenuated psychosis syndrome (APS) and schizophrenia. In this study, we hypothesized that STRs in the white matter fiber bundles of impairments underlie abnormalities in fixation and scan path length in individuals with APS.
METHODS
Twenty-one individuals with APS and 30 healthy controls participated in this study. All participants underwent diffusion tensor imaging, and fractional anisotropy (FA) values of the left and right STR were analyzed using the novel method TractSeg. The number of eye fixations (NEF), total eye scanning length (TESL), and mean eye scanning length (MESL), derived using the exploratory eye movement (EEM) test, were adopted to evaluate the fixation and scan path length. We compared the FA values of the bilateral STR and EEM parameters between the APS and healthy control groups. We investigated the correlation between bilateral STR and EEM parameters in the APS and healthy control groups.
RESULTS
NEF, TESL, MESL, and the FA values of the left STR were significantly reduced in individuals with APS compared to healthy controls. The left STR FA value in the APS group was significantly positively correlated with the MESL ( = 0.567, = 0.007). In addition, the right STR FA value of the APS group was significantly correlated with the TESL ( = 0.587, = 0.005) and MESL ( = 0.756, = 0.7×10).
DISCUSSION
These results demonstrate that biological changes in the STR, which connects the thalamus and FEF, underlie abnormalities in fixation and scanning. Recently, aberrations in the thalamus-frontal connection have been shown to underlie the emergence of psychotic symptoms. STR impairment may be a part of the biological basis of APS in individuals with subthreshold psychotic symptoms.
PubMed: 38938465
DOI: 10.3389/fpsyt.2024.1323786 -
Advanced Science (Weinheim,... Jun 2024Nano air channel transistors (NACTs) provide numerous advantages over traditional silicon devices, including faster switching speeds, higher operating frequencies, and...
Nano air channel transistors (NACTs) provide numerous advantages over traditional silicon devices, including faster switching speeds, higher operating frequencies, and enhanced radiation hardness attributable to the ballistic transport of electrons. In the development of field-emission-based integrated circuits, low-power consumption rectifying nano air channel diodes (NACDs) play a crucial role. However, achieving rectification characteristics in NACDs is challenging due to their structural and material symmetry. This paper proposes a vertical GaN NACD with a consistent nano air channel fabricated using IC-compatible processes. The GaN NACD exhibits an exceptionally low turn-on voltage of 0.3 V while delivering a high output current of 5.02 mA at 3 V. Notably, it demonstrates a high rectification ratio of up to 2.2 × 10, attributing to significant work function disparities within the GaN-Au structure, coupled with the reduction of Au surface roughness to minimize reverse current. Furthermore, the junction-free structure and superior material properties of GaN enable the NACD to be suitable for use in radiation-rich environments. With its potential as a fundamental component of ultrafast and ultrahigh-frequency integrated circuits, this intriguing and cost-effective rectifying diode is anticipated to garner widespread interest within the electronics community.
PubMed: 38937997
DOI: 10.1002/advs.202310300