Depth Scanning Research Articles

Technologies for depth scanning in miniature optical imaging systems [Invited

Biomedical optical imaging has found numerous clinical and research applications. For achieving 3D imaging, depth scanning presents the most significant challenge, particularly in miniature imaging devices. This paper reviews the state-of-art technologies for depth scanning in miniature optical imaging systems, which include two general approaches: 1) physically shifting part of or the entire imaging device to allow imaging at different depths and 2) optically changing the focus of the imaging optics. We mainly focus on the second group of methods, introducing a wide variety of tunable microlenses, covering the underlying physics, actuation mechanisms, and imaging performance. Representative applications in clinical and neuroscience research are briefly presented. Major challenges and future perspectives of depth/focus scanning technologies for biomedical optical imaging are also discussed.

Microstructural characterization of AlxGa1−xN/GaN high electron mobility transistor layers on 200 mm Si(111) substrates

Realization of high crystal quality GaN layers on silicon substrates requires a great control over epitaxy as well as detailed characterization of the buried defects and propagating dislocations within the epilayers. In this Letter, we present the microstructural characterization of AlxGa1−xN/GaN high electron mobility transistor (HEMT) structures epitaxially grown on 200 mm Si (111) substrates with superlattice (SL) buffers. The HEMT stack is also composed of an intermediate thick AlxGa1−xN layer sandwiched between the short-period and long-period AlxGa1−xN/AlN SLs. Structural and morphological characteristics of the GaN-based epilayers are studied to assess the quality of the HEMT stack grown on such 200 mm diameter substrates. The detailed microstructural uniformity of the epilayers is addressed by the transmission electron microscopy (TEM) technique. In depth scanning TEM with electron energy loss spectroscopy (EELS) investigations have been carried out to probe the microstructural quality of the HEMT stack comprising of such short- and long-period AlxGa1−xN/AlN SLs. The EELS-plasmon maps are utilized to address the sharp interface characteristics of the SL layers as well as the top active p-GaN/AlxGa1−xN/GaN layers. This work highlights the capability of high-resolution TEM as a complementing characterization method to produce reliable AlxGa1−xN/GaN HEMTs on such a large diameter silicon substrate.

Dynamics of the ultrasonographic picture of the skin and subcutaneous tissue in the physiotherapy treatment of cellulite by compression microvibration: а non-randomized prospective study

BACKGROUND: Various methods are offered to effectively eliminate cellulite and improve skin appearance; however, its treatment remains one of the most difficult tasks in aesthetic medicine. The arsenal of tools that allow an objective assessment of cosmetic and esthetic therapeutic measures is very limited.
 AIM: To evaluate the effectiveness of the compression microvibration method to treat structural and functional skin changes in women with gynoid lipodystrophy of different age groups.
 MATERIALS AND METHODS: A single-center, nonrandomized, prospective study of the effectiveness of the compression microvibration method (Endospheres Therapy) was carried out in 27 women (4069 years old) with mild-to-moderate gynoid lipodystrophy under the control of ultrasonographic skin examination before treatment, after 12 procedures, and after 2 months. After a course of therapy, skin ultrasonography was performed using a specialized high-resolution digital ultrasound system DUB SkinScanner (tpm GmbH, Germany) equipped with a 75 MHz transducer with a resolution of 21 m and a scanning depth of 46 mm. Additionally, anthropometric parameters were measured, and the body mass index was calculated.
 RESULTS: Changes in body mass index (BMI) revealed a trend toward weight loss in most of the participants. The circumference of the hips and waist in participants aged 4049, 5059 and 6069 years decreased by 3.01.1 and 5.31.1, 2.20.9 and 4.11.3 and 2.50.9 and 6.31.5 cm, respectively. It was found that after the course of Endospheres Therapy in patients of the 1st, 2nd and 3rd age groups in the areas of the anterior, inner, posterior surface of the thigh and the anterior surface of the abdomen, the thickness of the dermis decreased by 15.6, 9.5 and 18.1%; 10.9, 10.5 and 19.3%; 6.1, 15.7 and 13.8%, 23.4, 14.7 and 14.5% (p 0.05), respectively; increased echogenicity of the dermis in the areas of the anterior, inner, posterior thigh and anterior abdominal surface by 2, 1.4 and 1.3; 1.2, 1.4 and 1.2; 1.4, 1.4 and 1.5; 1.3, 1.5 and 1.7 times (p 0.05), respectively. The echogenicity of the hypodermis decreased in the studied areas by 30.8, 27.6 and 31.2% (p 0.05); 20.1, 37.3 and 40.4% (p 0.05); 43.2, 57.8 (p 0.05) and 9.3%; 23.6, 15.2 (p 0.05) and 9.3%, respectively. The effect persisted 60 days after the course of therapy.
 CONCLUSION: These results have convincingly demonstrated the effectiveness of Endospheres Therapy in women with mild-to-moderate gynoid lipodystrophy for body shaping and skin improvement in the long term without revealing any side effects.

The Effect of Filament Density on the Build-Up Region Responsiveness of 3D Printed Boluses in High-Energy Photon Radiotherapy

Due to the inability of commercial boluses to fully replicate the body's curvature during radiation treatments, introduction of 3D printed boluses can be a solution for avoiding the skin sparing effect for irregular body shapes. The purpose of this study was to assess the applicability of a uniformly thick 3D printed bolus. We report the influence of 6 different 3D printed boluses on the surface dose (Ds) delivered by a 6 MV photon beam linear accelerator. Six distinct types of filaments used in 3D modelling were evaluated. The selection of materials was determined by the filament's density, to be comparable with a commercial bolus used in clinical practice (tissue equivalent). Bolus plates of 21.5x21.5x0.5cm were designed, printed and exposed to high energy photon beam with field apertures of 5x5cm, 10x10cm, 15x15cm, and 20x20cm. We used a water tank phantom, which gives precise beam data visuals to confirm the delivered dose. The behavior of the profile depth dose (PDD) was analyzed for different air volumes between the bolus surface and water characterized by bolus-water distances of 0cm, 0.5cm, 1cm, and 1.5cm. A conventional beam geometry with SSD = 100cm and scanning depths of 15, 50, 100, 200, and 300 mm was used. The initial validation of the materials was performed by evaluating the CT attenuation properties (mean Hounsfield Units - HU) of the six 3D printed boluses and the commercial one. The commercial bolus had -34.89HU, whereas the ABS (-144.53HU), ASA (-124.40HU), Premium PLA (9.55HU), Polycarbonate (-140.79HU), Standard PLA (-68.58HU) and PET-G (-113.159HU) had comparable attenuation values. The PDD reference measurements without bolus resulted in the following surface dose (Ds) values: 54.42% for the 5x5cm field, 57.94% for 10x10cm, 61.29% for 15x15cm, and 65.44% for 20x20cm, respectively. We observed a proportional increase of Ds with the field size. Even more, when the bolus was in direct contact with water (0cm airgap), an influence of the material density on the Ds values was evidenced. For the commercial bolus (ρ = 1.01) we obtained a Ds = 95.59%, while ABS (ρ = 1.04) had Ds = 89.12%, ASA (ρ = 1.07) Ds = 86.51%, Premium PLA (ρ = 1.17) Ds = 90.89%, Polycarbonate (ρ = 1.19) Ds = 88.55%, Standard PLA (ρ = 1.24) Ds = 89.15%, and PET-G (ρ = 1.27) Ds = 88.78%, respectively. The Ds value dropped following the increase of the introduced air volume. The Ds values and the analysis of the buildup regions in the depth dose profile revealed the significance of the air present between the skin surface and the bolus in the clinical setting, as well as the need to reduce these air gaps. We confirmed from a dosimetric perspective, that the materials used for the 3D printed bolus plates are suitable to be used as a clinical bolus. Further validation studies are warranted to exploit the potential of these 3D printed boluses in real clinical scenarios.

Comprehensive fully-automatic multi-depth grading of the clinical types of macular neovascularization in OCTA images

AbstractOptical Coherence Tomography Angiography or OCTA represents one of the main means of diagnosis of Age-related Macular Degeneration (AMD), the leading cause of blindness in developed countries. This eye disease is characterized by Macular Neovascularization (MNV), the formation of vessels that tear through the retinal tissues. Four types of MNV can be distinguished, each representing different levels of severity. Both the aggressiveness of the treatment and the recovery of the patient rely on an early detection and correct diagnosis of the stage of the disease. In this work, we propose the first fully-automatic grading methodology that considers all the four clinical types of MNV at the three most relevant OCTA scanning depths for the diagnosis of AMD. We perform both a comprehensive ablation study on the contribution of said depths and an analysis of the attention maps of the network in collaboration with experts of the domain. Our proposal aims to ease the diagnosis burden and decrease the influence of subjectivity on it, offering a explainable grading through the visualization of the attention of the expert models. Our grading proposal achieved satisfactory results with an AUC of 0.9224 ± 0.0381. Additionally, the qualitative analysis performed in collaboration with experts revealed the relevance of the avascular plexus in the grading of all three types of MNV (despite not being directly involved in some of them). Thus, our proposal is not only able to robustly detect MNV in complex scenarios, but also aided to discover previously unconsidered relationships between plexuses.

Learning flat optics for extended depth of field microscopy imaging

Abstract Conventional microscopy systems have limited depth of field, which often necessitates depth scanning techniques hindered by light scattering. Various techniques have been developed to address this challenge, but they have limited extended depth of field (EDOF) capabilities. To overcome this challenge, this study proposes an end-to-end optimization framework for building a computational EDOF microscope that combines a 4f microscopy optical setup incorporating learned optics at the Fourier plane and a post-processing deblurring neural network. Utilizing the end-to-end differentiable model, we present a systematic design methodology for computational EDOF microscopy based on the specific visualization requirements of the sample under examination. In particular, we demonstrate that the metasurface optics provides key advantages for extreme EDOF imaging conditions, where the extended DOF range is well beyond what is demonstrated in state of the art, achieving superior EDOF performance.

Effect of Process Parameters on Properties of NiCrAl20%WC Cladding Layer

NiCrAl/20%WC coatings were prepared by laser cladding on 45 steel under different technological parameters. The effects of technological parameters on the microstructure, microstructure, hardness and wear resistance were investigated. The results show that with the increase of the scanning speed, the height, width, depth and dilution rate of the cladding layer gradually decrease, the microstructure becomes smaller and smaller, the hardness gradually increases, and the wear amount decreases first and then increases, and the wear amount is the least when the scanning speed is 600 mm/min. With the increase of laser power, the height, width, depth and dilution rate of cladding layer gradually increase. The hardness gradually decreases; The wear decreases first and then increases, and the wear is the least when the laser power is 1.2 kW.

Super-resolution ultrasound imaging -- creating 3D in vivo images of the renal microvasculature

Aim: Our overall aim is to create 3D in vivo microvascular imaging of the renal vasculature in healthy and diabetic rats in real time. Methods-1: Super-resolution ultrasound imaging (SRUS) using intravascular microbubbles (MBs) can generate in vivo images of the renal microcirculation. Spatially separated MBs are followed over numerous image frames to create anatomical vascular images showing MB direction and velocity. Presently, images with a resolution of 50 μm are obtainable. Results-1: As diabetes mellitus is associated with micro- and macrovascular diseases also affecting the kidneys we used SRUS on Zucker Diabetic Fat rats (ZDF) aged 12-, 20- and 40-weeks. We show a significant decrease in vascular density in the cortex at week 12 before onset of proteinuria when compared to age-matched lean Zucker rats. At week 20 vascular density decreased in the outer medulla and inner medulla. No significant changes were found in vascular tortuosity. However, the SRUS images are collected over several minutes, and are challenged by tissue motion and the lack of real-time imaging. The fragile MBs limit emission pressure and thus scan depth. Hypothesis: We hypothesize that tracking erythrocytes instead of MBs will reduce these obstacles and make the method non-invasive. Resolution and scan depth will increase and scan time will shorten. This will allow an easy transition into the clinic. Results-2: Using this innovative method, we have generated images of healthy rat kidneys. Within 24 seconds, we can create an image of the renal vasculature showing the vasa recta (the capillary network penetrating the medulla) and the arcuate and cortical radial arteries. μCT scans have verified the structure of the vascular tree. However, even at these short scan times, there is considerable tissue motion from heart-beat, respiration etc. moving the image out of plane. To clearly image the true microcirculation, 3D imaging is needed. We have recently obtained this amazing step and made a 3D in vivo scan of a healthy rat kidney. The project is funded by an ERC Synergy Grant SURE, project no. 854796. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Region- and layer-specific investigations of the human menisci using SHG imaging and biaxial testing.

In this paper, we examine the region- and layer-specific collagen fiber morphology via second harmonic generation (SHG) in combination with planar biaxial tension testing to suggest a structure-based constitutive model for the human meniscal tissue. Five lateral and four medial menisci were utilized, with samples excised across the thickness from the anterior, mid-body, and posterior regions of each meniscus. An optical clearing protocol enhanced the scan depth. SHG imaging revealed that the top samples consisted of randomly oriented fibers with a mean fiber orientation of 43.3 o . The bottom samples were dominated by circumferentially organized fibers, with a mean orientation of 9.5 o . Biaxial testing revealed a clear anisotropic response, with the circumferential direction being stiffer than the radial direction. The bottom samples from the anterior region of the medial menisci exhibited higher circumferential elastic modulus with a mean value of 21MPa. The data from the two testing protocols were combined to characterize the tissue with an anisotropic hyperelastic material model based on the generalized structure tensor approach. The model showed good agreement in representing the material anisotropy with a mean r 2 = 0.92.

A Hybrid System for Automatic Identification of Corneal Layers on In Vivo Confocal Microscopy Images.

Accurate identification of corneal layers with in vivo confocal microscopy (IVCM) is essential for the correct assessment of corneal lesions. This project aims to obtain a reliable automated identification of corneal layers from IVCM images. A total of 7957 IVCM images were included for model training and testing. Scanning depth information and pixel information of IVCM images were used to build the classification system. Firstly, two base classifiers based on convolutional neural networks and K-nearest neighbors were constructed. Second, two hybrid strategies, namely weighted voting method and light gradient boosting machine (LightGBM) algorithm were used to fuse the results from the two base classifiers and obtain the final classification. Finally, the confidence of prediction results was stratified to help find out model errors. Both two hybrid systems outperformed the two base classifiers. The weighted area under the curve, weighted precision, weighted recall, and weighted F1 score were 0.9841, 0.9096, 0.9145, and 0.9111 for weighted voting hybrid system, and were 0.9794, 0.9039, 0.9055, and 0.9034 for the light gradient boosting machine stacking hybrid system, respectively. More than one-half of the misclassified samples were found using the confidence stratification method. The proposed hybrid approach could effectively integrate the scanning depth and pixel information of IVCM images, allowing for the accurate identification of corneal layers for grossly normal IVCM images. The confidence stratification approach was useful to find out misclassification of the system. The proposed hybrid approach lays important groundwork for the automatic identification of the corneal layer for IVCM images.

Impact of angle on photothermal radiometry and modulated luminescence (PTR/LUM) value

ObjectiveTo evaluate the impact of scanning angles to detect/quantify non-cavitated caries by photothermal-radiometry and modulated-luminescence (PTR/LUM, Canary System) and to evaluate the association of PTR/LUM value with lesion depth (LD), including sound tissue thickness under the lesion (ST). MethodsThirty human extracted premolars were selected based on micro-computed tomography [μ-CT: sound (n=12), lesions into outer-half of enamel (n=6), lesions into inner-half of enamel (n=6), lesions into outer one-third of dentine (n=6)]. Each tooth sample was scanned 90° directly contacted to the center of non-cavitated lesion or sound smooth surface, and tilted 10° and 20° in four directions: buccal/lingual/occlusal/cervical. The procedure was repeated 48 h later. Lesion depth and ST [ST=5000 µm (maximum PTR/LUM scanning depth)-LD] were measured at the same scanning direction on μ-CT images. Sensitivity, specificity, area under the Receiver Operating Characteristic curve (AUC), and intraclass correlation coefficients (ICC) for different scanning angles were calculated. Sensitivity was further evaluated based on lesion extensions. Relationships between PTR/LUM value and lesion depth, and between PTR/LUM value and LD/ST-Ratio were evaluated. ResultsPTR/LUM value showed significant differences among scanning angles. Overall sensitivity (78%–89%), specificity (66%–87%), AUC (0.86–0.92) and ICC (0.89–0.99), sensitivity based on lesion extensions presented no significant differences among angles. PTR/LUM value showed moderate correlations (0.56–0.74) with deepest lesion depth and LD/ST-Ratios. ConclusionThe scanning angle within 20° increments might impact PTR/LUM value statistically; however, it did not affect PTR/LUM detection performance. PTR/LUM values were positively correlated with non-cavitated lesion depth, and not affected by sound tissue thickness under the lesion. Clinical significance: Clinically, it is challenging to measure/scan at the same location and same angle longitudinally, however, it is important to standardize these parameters. Scanning within 20° deviation from perpendicular did not affect detection performance of PTR/LUM, and PTR/LUM value showed positive moderate correlation with caries depth.

Application of endoscopic ultrasound to the descending colon and rectum in normal dogs.

Endoscopic ultrasound (EUS) is a medical procedure in which endoscopy is combined with ultrasonography (US) to compensate for problems associated with the transabdominal US such as large penetration depths, presence of intestinal gas, and acoustic shadowing. This prospective, method comparison, pilot study was performed to assess the feasibility of applying EUS in the colorectal region and to describe the typical EUS features of the descending colon and rectum in healthy dogs. Transabdominal US and EUS with or without the hydrosonography were applied to the descending colon and rectum in 10 clinically healthy Beagle dogs and wall thickness, visibility of the wall layers, and conspicuity of the mucosal and serosal surfaces of the intestinal wall were assessed. Endoscopic ultrasound enabled circumferential evaluation of the colorectal wall and provided better visibility of the wall layers and conspicuity of the mucosal and serosal surfaces without degradation of the image, even in the far-field portion of the colorectal wall, compared to US. Moreover, EUS provided the adequate image quality of the rectum, which was difficult to evaluate with US due to deep scan depth and acoustic shadowing by the pelvis. Meanwhile, the application of hydrosonography to EUS deteriorated the visibility of the wall layers and conspicuity of the intestinal wall. The results of this study demonstrate the feasibility of EUS to assess the colorectal region and its potential application for the evaluation of rectal masses or intrapelvic lesions that are inaccessible by the transabdominal US in dogs.

Morphological and Morphometric Analysis of Canine Choroidal Layers Using Spectral Domain Optical Coherence Tomography.

The choroid, a multifunctional tissue, has been the focus of research interest for many scientists. Its morphology and morphometry facilitate an understanding of pathological processes within both the choroid and retina. This study aimed to determine the choroidal layer thicknesses in healthy, mixed-breed mesocephalic dogs, both male (M) and female (F), using spectral domain optical coherence tomography (SD-OCT) with radial, cross-sectional, and linear scans. The dogs were divided into two groups based on age: middle-aged (MA) and senior (SN). Thicknesses of choroidal layers, namely RPE-Bruch's membrane-choriocapillaris complex (RPE-BmCc) with tapetum lucidum in the tapetal fundus, the medium-sized vessel layer (MSVL), and the large vessel layer with lamina suprachoroidea (LVLS), as well as whole choroidal thickness (WCT), were measured manually using the caliper function integrated into the OCT software. Measurement was performed dorsally and ventrally at a distance of 5000-6000 μm temporally and nasally at a distance of 4000-7000 μm to the optic disc on enhanced depth scans. The measurements were conducted temporally and nasally in both the tapetal (temporal tapetal: TempT, nasal tapetal: NasT) and nontapetal (temporal nontapetal: TempNT, nasal nontapetal: NasNT) fundus. The ratio of the MSVL thickness to the LVLS thickness for each region was calculated. In all examined dogs, the RPE-BmCc in the dorsal (D) region and MSVL in the Tt region were significantly thicker than those in the other regions. The MSVL was thinner in the ventral (V) region than in the D, TempT, TempNT and NasT regions. The MSVL was significantly thinner in the NasNT region than in the D region. LVLS thickness and WCT were significantly greater in the D and TempT regions than those in the other regions and significantly lesser in the V region than those in the other regions. The MSVL-to-LVLS thickness ratio did not differ between the age groups. Our results reveal that the choroidal thickness profile does not depend on age. Our findings can be used to document the emergence and development of various choroidal diseases in dogs in the future.

Optical design and fabrication of zinc selenide microlens array with extended depth of focus for biomedical imaging

Optical coherence tomography is a well-known technique for the optical imaging biological tissues. However, the depth scanning range of high-resolution optical coherence tomography is restricted by its depth of focus. In this study, a Zinc Selenide (ZnSe) Microlens Array (MLA) is employed to overcome the depth-of-focus limitation of optical coherence tomography. The ZnSe material with a low Abbe number and high chromatic dispersion extends the depth of focus with transverse resolution. The ZnSe MLA focused the incident light (from visible to near-infrared (NIR) region) on multiple focal planes with the uniform distribution of light over a biological tissue. The MLA is designed using Zemax OpticStudio software and fabricated via a single-point diamond-turning based on Slow Tool Servo (STS) configuration. STS machining has the unique advantage of offering larger degrees of freedom with no additional baggage, thereby reducing the setup time. The experimental results show the effectiveness of the STS machining process in fabricating ZnSe MLA with desired accuracies. The characterization of fabricated MLA using Coherence Correlation Interferometry (CCI) depicts uniform lenslets with no structural and positional distortion, with a total error of 32 nm within the tolerance limit.

Profiling H2O2 from single COS-7 cells by means of scanning electrochemical microscopy

We report quantitative determination of extracellular H2O2 released from single COS-7 cells with high spatial resolution, using scanning electrochemical microscopy (SECM). Our strategy of depth scan imaging in vertical x-z plane was conveniently utilized to a single cell for obtaining probe approach curves (PACs) to any positions on the membrane of a live cell by simply drawing a vertical line on one depth SECM image. This SECM mode provides an efficient way to record a batch of PACs, and visualize cell topography simultaneously. The H2O2 concentration at the membrane surface in the center of an intact COS-7 cell was deconvoluted from apparent O2, and determined to be 0.020 mM by overlapping the experimental PAC with the simulated one having a known H2O2 release value. The H2O2 profile determined in this way gives insight into physiological activity of single live cells. In addition, intracellular H2O2 profile was demonstrated using confocal microscopy by labelling the cells with a luminomphore, 2′,7′-dichlorodihydrofluorescein diacetate. The two methodologies have illustrated complementary experimental results of H2O2 detection, indicating that H2O2 generation is centered at endoplasmic reticula.

A Novel Ultrasound Robot with Force/torque Measurement and Control for Safe and Efficient Scanning.

Medical ultrasound is of increasing importance in medical diagnosis and intraoperative assistance and possesses great potential advantages when integrated with robotics. However, some concerns, including the operation efficiency, operation safety, image quality, and comfort of patients, remain after introducing robotics into medical ultrasound. In this paper, an ultrasound robot integrating a force control mechanism, force/torque measurement mechanism, and online adjustment method, is proposed to overcome the current limitations. The ultrasound robot can measure operating forces and torques, provide adjustable constant operating forces, eliminate great operating forces introduced by accidental operations, and achieve various scanning depths based on clinical requirements. The proposed ultrasound robot would potentially facilitate sonographers to find the targets quickly, improve operation safety and efficiency, and decrease patients' discomfort. Simulations and experiments were carried out to evaluate the performance of the ultrasound robot. Experimental results show that the proposed ultrasound robot is able to detect operating force in the z-direction and torques around the x- and y- directions with errors of 3.53% F.S., 6.68% F.S., and 6.11% F.S., respectively, maintain the constant operating force with errors of less than 0.57N, and achieve various scanning depths for target searching and imaging. This proposed ultrasound robot has good performance and would potentially be used in medical ultrasound.

Adaptive Active Fusion of Camera and Single-Point LiDAR for Depth Estimation

Depth sensing is an important problem in many applications such as autonomous driving, robotics, and automation. This paper presents an adaptive active fusion method for scene depth estimation by using an RGB camera and a single-point LiDAR. An active scanning mechanism is proposed to guide laser scanning based on critical visual and saliency features, and the convolutional spatial propagation network (CSPN) is designed to generate and refine full depth map from the sparse depth scans. The active scanning mechanism generates a depth mask by using log-spectrum saliency detection, Canny edge detection, and uniform sampling, which indicate critical regions that require a high resolution of laser scanning. To reconstruct a full depth map, the designed CSPN network extracts affinity matrices from the sparse depth scans, while reserving global spatial information in the RGB images. The performance of proposed method was evaluated and compared with the state-of-the-art methods on the NYUv2 dataset, and the experiment demonstrated its outperformance in reconstruction accuracy and robustness to measurement noise. The proposed method was also evaluated in real-world scenarios.

Formation mechanism and regulation of silicon vacancy centers in polycrystalline diamond films

Diamond silicon vacancy centers (SiV centers) have important application prospects in quantum information technology and biomarkers. In this work, the formation mechanism and regulation method of SiV center during the growth of polycrystalline diamond on silicon substrate are studied. By changing the ratio of nitrogen content to oxygen content in the growing atmosphere of diamond, the photoluminescence intensity of SiV center can be controlled effectively, and polycrystalline diamond samples with the ratios of SiV center photoluminescence peak to diamond intrinsic peak as high as 334.46 and as low as 1.48 are prepared. It is found that nitrogen promotes the formation of SiV center in the growth process, and the inhibition of oxygen. The surface morphology and photoluminescence spectrum for each of these samples show that the photoluminescence peak intensity of SiV center is positively correlated with the grain size of diamond, and the SiV center’s photoluminescence peak in the diamond film with obvious preferred orientation of crystal plane is higher. The distribution of Si centers and SiV centers on the surface of polycrystalline diamond are further characterized and analyzed by photoluminescence, Raman surface scanning and depth scanning spectroscopy. It is found that during the growth of polycrystalline diamond, the substrate silicon diffuses first into the diamond grain and then into the crystal structure to form the SiV center. This paper provides a theoretical basis for the development and application of SiV centers in diamond.

TURBO: A novel beam delivery system enabling rapid depth scanning for charged particle therapy

Charged particle therapy (CPT) is a well-established modality of cancer treatment and is increasing in worldwide presence due to improved accelerator technology and modern techniques. The beam delivery system (BDS) determines the overall timing and beam shaping capabilities, but is restricted by the energy variation speed: energy layer switching time (ELST). Existing treatment beamlines have a ±1% momentum acceptance range, needing time to change the magnetic fields as the beam is delivered in layers at various depths across the tumour volume. Minimising the ELST can enable the delivery of faster, more effective and advanced treatments but requires an improved BDS. A possibility for this could be achieved with a design using Fixed Field Alternating Gradient (FFA) optics, enabling a large energy acceptance to rapidly transport beams of varying energies. A scaled-down, novel system – Technology for Ultra Rapid Beam Operation (TURBO) – is being developed at the University of Melbourne, to explore the potential of rapid depth scanning. Initial simulation studies, beam and field measurements, project plans and clinical considerations are discussed.

Mammalian tooth enamel functional sophistication demonstrated by combined nanotribology and synchrotron radiation FTIR analyses

The teeth of limbed vertebrates used for capturing and processing food are composed of mineralized dentine covered by hypermineralized enamel, the hardest material organisms produce. Here, we combine scanning probe microscopy, depth sensing, and spectromicroscopy (SR-FTIR) to characterize the surface ultrastructural topography, nanotribology, and chemical compositions of mammal species with different dietary habits, including omnivorous humans. Our synergistic approach shows that enamel with greater surface hardness or thickness exhibited a more salient gradient feature from the tooth surface to the dentino-enamel junction (DEJ) one that corresponds to the in situ phosphate-to-amide ratio. This gradient feature of enamel covering softer dentine is the determining factor of the amazingly robust physical property of this unique biomaterial. It provides the ability to dissipate stress under loading and prevent mechanical failure. Evolutionary change in the biochemical composition and biomechanical properties of mammalian dentition is related to variations in the oral processing of different food materials.