Transrectal ultrasound vector projectile imaging for time-resolved visualization of flow dynamics in the male urethra: A clinical pilot study.

BACKGROUND: Quantitative and comprehensive visualization of urinary flow dynamics in the urethra is crucial for investigating patient-specific mechanisms of lower urinary tract symptoms (LUTS). Although some methods can evaluate the global properties of the urethra, it is critical to assess the local information, such as the location of the responsible lesion and its interactions with urinary flow in relation to LUTS. This approach is vital for enhancing personalized and focal treatments. However, there is a lack of such diagnostic tools that can directly observe how the urethral shape and motion impact urinary flow in the urethra. PURPOSE: This study aimed to develop a novel transrectal ultrasound imaging modality based on the contrast-enhanced urodynamic vector projectile imaging (CE-UroVPI) framework and validate its clinical applicability for visualizing time-resolved flow dynamics in the urethra. METHODS: A new CE-UroVPI system was developed using a research-purpose ultrasound platform and a custom transrectal linear probe, and an imaging protocol for acquiring urodynamic echo data in male patients was designed. Thirty-four male patients with LUTS participated in this study. CE-UroVPI was performed to acquire ultrasound echo signals from the participant's urethra and urinary flow at various voiding phases (initiation, maintenance, and terminal). The ultrasound datasets were processed with custom software to visualize urinary flow dynamics and urethra tissue deformation. RESULTS: The transrectal CE-UroVPI system successfully visualized the time-resolved multidirectional urinary flow dynamics in the prostatic urethra during the initiation, maintenance, and terminal phases of voiding in 17 patients at a frame rate of 1250 fps. The maximum flow speed measured in this study was 2.5 m/s. In addition, when the urethra had an obstruction or an irregular partial deformation, the devised imaging modality visualized complex flow patterns, such as vortices and flow jets around the lesion. CONCLUSIONS: Our study findings demonstrate that the transrectal CE-UroVPI system developed in this study can effectively image fluid-structural interactions in the urethra. This new diagnostic technology has the potential to facilitate quantitative and precise assessments of urethral voiding functions and aid in the improvement of focal and effective treatments for patients with LUTS.

A GPU-Based, Real-Time Dealiasing Framework for High-Frame-Rate Vector Doppler Imaging.

Vector Doppler is well regarded as a potential way of deriving flow vectors to intuitively visualize complex flow profiles, especially when it is implemented at high frame rates. However, this technique's performance is known to suffer from aliasing artifacts. There is a dire need to devise real-time dealiasing solutions for vector Doppler. In this article, we present a new methodological framework for achieving aliasing-resistant flow vector estimation at real-time throughput from precalculated Doppler frequencies. Our framework comprises a series of compute kernels that have synergized: 1) an extended least squares vector Doppler (ELS-VD) algorithm; 2) single-instruction, multiple-thread (SIMT) processing principles; and 3) implementation on a graphical processing unit (GPU). Results show that this new framework, when executed on an RTX-2080 GPU, can effectively generate aliasing-free flow vector maps using high-frame-rate imaging datasets acquired from multiple transmit-receive angle pairs in a carotid phantom imaging scenario. Over the entire cardiac cycle, the frame processing time for aliasing-resistant vector estimation was measured to be less than 16 ms, which corresponds to a minimum processing throughput of 62.5 frames/s. In a human femoral bifurcation imaging trial with fast flow (150 cm/s), our framework was found to be effective in resolving two-cycle aliasing artifacts at a minimum throughput of 53 frames/s. The framework's processing throughput was generally in the real-time range for practical combinations of ELS-VD algorithmic parameters. Overall, this work represents the first demonstration of real-time, GPU-based aliasing-resistant vector flow imaging using vector Doppler estimation principles.

Ultrasound vector flow imaging during veno-arterial extracorporeal membrane oxygenation in a thoracic aorta model.

In veno-arterial extracorporeal membrane oxygenation (VA-ECMO) treatment, the mixing zone is a key hemodynamic factor that determines the efficacy of the treatment. This study aimed to evaluate the applicability of a novel ultrasound technique called vector flow imaging (VFI) for visualizing complex flow patterns in an aorta phantom under VA-ECMO settings. VFI experiments were performed to image aortic hemodynamics under VA-ECMO treatment simulated in an anthropomorphic thoracic aorta phantom using a pulsatile pump (cardiac output: 2.7 L/min) and an ECMO pump with two different flow rates, 0.35 L/min and 1.0 L/min. The cardiac cycle of hemodynamics in the ascending aorta, aortic arch, and descending aorta was visualized, and the spatio-temporal dynamics of flow vectors were analyzed. VFI successfully visualized dynamic flow patterns in the aorta phantom. When the flow rate of the ECMO pump increased, ECMO flow was more dominant than cardiac output in the diastole phase, and the speed of cardiac output was suppressed in the systole phase. Vortex flow patterns were also detected in the ascending aorta and the arch under both ECMO flow rate conditions. The VFI technique may provide new insights into aortic hemodynamics and facilitates effective and safe VA-ECMO treatment.

Utilization of Curvelet Transform in Reconstructing Cellular Images for Undersampled Optical-Resolution Photoacoustic Microscopy.

We address the problem of limited temporal resolution in optical-resolution microscopy (OR-PAM) for cellular imaging by undersampling and reconstruction. A curvelet transform method in a compressed sensing framework (CS-CVT) was devised to specifically reconstruct the boundary and separability of cell objects in an image. The performance of the CS-CVT approach was justified by comparisons with the natural neighbor interpolation (NNI) followed by smoothing filters on various imaging objects. In addition, a full-raster scanned image was provided as a reference. In terms of structure, CS-CVT produces cellular images with a smoother boundary but less aberration. We found the strength of CS-CVT in recovering high frequency that is important in representing sharp edges which often missing in typical smoothing filters. In a noisy environment, CS-CVT was less affected by the noise compared to NNI with a smoothing filter. Furthermore, CS-CVT could attenuate noise beyond the full raster scanned image. By considering the finest structure in the cellular image, CS-CVT was performing well with a minimum range of undersampling around 5% to 15%. In practice, this undersampling was easily translated into 8- to 4-fold faster OR-PAM imaging. In summary, our approach improves the temporal resolution of OR-PAM without a significant tradeoff in image quality.

Evaluation of temperature-dependent fluctuations in skin microcirculation flow using a light-emitting diode based photoacoustic imaging device.

PURPOSE: Skin microvessels maintain temperature homeostasis by contracting and dilating upon exposure to changes in temperature. Under general anesthesia, surgical invasiveness, including incisions and coagulation, and the effects of anesthetics may cause variations in the threshold temperature, leading to the constriction and dilation of cutaneous blood vessels. Therefore, studies on skin microvascular circulation are necessary to develop appropriate interventions for complications during surgery. METHODS: We visualized and quantified skin microcirculatory fluctuations associated with temperature variations using a light-emitting diode photoacoustic imaging (LED-PAI) device. The hands of ten healthy volunteers were stressed with four different water temperatures [25℃ (Control), 15℃ (Cold1), 40℃ (Warm), and 15℃ (Cold2)]. The photoacoustic images of the fingers were taken under each condition, and the microvascular flow owing to temperature stress was quantified as the area of photoacoustic signal (S) in each image. The S values were compared with the variations in blood flow (Q) measured by laser Doppler flowmetry (LDF). RESULTS: The correlation between Q and S according to the 40 measurements was r = 0.45 (p＜0.01). In addition, the values of S under each stress condition were as follows: Scontrol = 10,826 ± 3364 pixels, Scold1 = 8825 ± 2484 pixels, Swarm = 13,369 ± 3001 pixels, and Scold2 = 8838 ± 1892 pixels; the differences were significant. The LDF blood flow (Q) showed similar changes among conditions. CONCLUSION: These findings suggest that the LED-PAI device could be an option for evaluating microcirculation in association with changes in temperature.

Development of Ultrasound Phantom Made of Transparent Material: Feasibility of Optical Particle Image Velocimetry.

OBJECTIVE: The need for ultrasound flow phantoms to validate ultrasound systems requires the development of materials that can clearly visualize the flow inside for measurement purposes. METHODS: A transparent ultrasound flow phantom material composed of poly(vinyl alcohol) hydrogel (PVA-H) with dimethyl sulfoxide (DMSO) and water solution manufactured using the freezing method and mixed with quartz glass powder to exhibit scattering effects is proposed. To achieve transparency of the hydrogel phantom, the refractive index (RI) was changed to match that of the glass by modifying the PVA concentration and the ratio of DMSO to water in the solvent. The feasibility of optical particle image velocimetry (PIV) was verified by comparing an acrylic rectangular cross-section channel with a rigid wall. After the feasibility tests, an ultrasound flow phantom was fabricated to conduct ultrasound B-mode visualization and Doppler-PIV comparison. DISCUSSION: The results revealed that the PIV measured through PVA-H material exhibited 0.8% error in the measured maximum velocity compared with PIV through the acrylic material. B-mode images are similar to real tissue visualization with a limitation of a higher sound velocity, when compared with human tissue, of 1792 m/s. Doppler measurement of the phantom revealed approximately 120% and 19% overestimation of maximum and mean velocities, respectively, compared with those from PIV. CONCLUSION: The proposed material possesses the advantage of the single-phantom ability to improve the ultrasound flow phantom for validation of flow.

Region-based SVD processing of high-frequency ultrafast ultrasound to visualize cutaneous vascular networks.

Observing alterations in cutaneous vasculature in response to any disease or pathology is considered as a potential diagnostic marker in the progression and cure of a disease. To observe skin morphologies and tissue conditions, high-frequency ultrasound (HFUS) has been used in dermatology, although its ability to selectively visualize micro-vessels is limited due to insufficient Doppler sensitivity to peripheral slow-speed blood flow. In recent studies, this issue has been improved by increasing the sensitivity of Doppler imaging to slow flow, leveraging advanced cutter filtering approaches based on singular value decomposition (SVD) techniques that aid to effectively extract flow signals overlapped with tissue echo signals. Nevertheless, in skin imaging, variations in flow speed, diameter, and depth of the blood vessels at different skin layers can make clutter filtering challenging because these variations are problematic in selecting the optimal cut-off value for the SVD filtering. In this study, we aimed to devise a novel region-based SVD filtering approach for ultrafast HFUS data to visualize cutaneous vascular networks. The proposed method divides the acquired high-framerate data into two regions based on B-mode cutaneous morphological identification (dermis layer and subcutaneous tissue). Singular value decomposition processing was performed on each region to effectively extract the desired flow signal, and the processed regions were merged to generate a single power Doppler image, thereby highlighting the appearance of a complete cutaneous vascular network. Finally, top-hat transform was applied to the power Doppler image to further suppress the background noises and enhances the visibility of the micro-vessels. Experimental observations of the human cutaneous circulation showed that the image quality (contrast-to-noise ratio) through the region-based SVD filtering was measured to be 4.1 dB (before top-hat filtering) and 5.2 dB (after top-hat filtering), which were improved from 3.4 dB and 4.0 dB obtained using the global SVD approach with and without top-hat filtering, respectively. We envisioned that this approach would provide diverse applications in the diagnosis of cutaneous disorders.

Prediction of heading date, culm length, and biomass from canopy-height-related parameters derived from time-series UAV observations of rice.

Unmanned aerial vehicles (UAVs) are powerful tools for monitoring crops for high-throughput phenotyping. Time-series aerial photography of fields can record the whole process of crop growth. Canopy height (CH), which is vertical plant growth, has been used as an indicator for the evaluation of lodging tolerance and the prediction of biomass and yield. However, there have been few attempts to use UAV-derived time-series CH data for field testing of crop lines. Here we provide a novel framework for trait prediction using CH data in rice. We generated UAV-based digital surface models of crops to extract CH data of 30 Japanese rice cultivars in 2019, 2020, and 2021. CH-related parameters were calculated in a non-linear time-series model as an S-shaped plant growth curve. The maximum saturation CH value was the most important predictor for culm length. The time point at the maximum CH contributed to the prediction of days to heading, and was able to predict stem and leaf weight and aboveground weight, possibly reflecting the association of biomass with duration of vegetative growth. These results indicate that the CH-related parameters acquired by UAV can be useful as predictors of traits typically measured by hand.

Development of an Imaging Framework for Visualization of Cutaneous Micro-Vasculature by using High Frequency Ultrafast Ultrasound Imaging.

Visualization of cutaneous micro-vasculatures is a determined approach in the diagnosis of skin vascular disorders. Clinically, high frequency ultrasound (HFUS) modalities have been used for cutaneous morphological and structural imaging, but visualization of micro-vessels has always been remained a daunting task. These tiny structures might be visualized by devising a highly sensitive Doppler technique for HFUS systems. In this study, we proposed an imaging framework using HFUS (30 MHz) ultrafast Doppler imaging along with SVD clutter filtering that is proficient in detection of micro-scale circulation. The performance of the devised framework was examined on a 200-micron flow phantom made of poly-vinyl alcohol under four different flow rates (56 - 18 ul/min) and visualized the micro-structure with averaged detected diameter of 93 - 170 µm. The results indicated that the devised framework has sufficient sensitivity and resolvability to visualize the micro-vasculatures in dermis layer of skin (depth ≤ 4 mm). Clinical Relevance - This study brings an insight to visualize in-vivo cutaneous micro-vasculatures with ultrafast Doppler imaging in clinical applications for better assessment of cutaneous disorders.

High-speed optical resolution photoacoustic microscopy with MEMS scanner using a novel and simple distortion correction method.

Optical resolution photoacoustic microscopy (OR-PAM) is a remarkable biomedical imaging technique that can selectively visualize microtissues with optical-dependent high resolution. However, traditional OR-PAM using mechanical stages provides slow imaging speed, making it difficult to biologically interpret in vivo tissue. In this study, we developed a high-speed OR-PAM using a recently commercialized MEMS mirror. This system (MEMS-OR-PAM) consists of a 1-axis MEMS mirror and a mechanical stage. Furthermore, this study proposes a novel calibration method that quickly removes the spatial distortion caused by fast MEMS scanning. The proposed calibration method can easily correct distortions caused by both the scan geometry of the MEMS mirror and its nonlinear motion by running an image sequence only once using a ruler target. The combination of MEMS-OR-PAM and distortion correction method was verified using three experiments: (1) leaf skeleton phantom imaging to test the distortion correction efficacy; (2) spatial resolution and depth of field (DOF) measurement for system performance; (3) in-vivo finger capillary imaging to verify their biomedical use. The results showed that the combination could achieve a high-speed (32 s in 2 × 4 mm) and high lateral resolution (~ 6 µm) imaging capability and precisely visualize the circulating structure of the finger capillaries.

Genetic Background Negates Improvements in Rice Flour Characteristics and Food Processing Properties Caused by a Mutant Allele of the PDIL1-1 Seed Storage Protein Gene.

Phenotypic differences among breeding lines that introduce the same superior gene allele can be a barrier to effective development of cultivars with desirable traits in some crop species. For example, a deficient mutation of the Protein Disulfide Isomerase Like 1-1 (PDIL1-1) gene can cause accumulation of glutelin seed storage protein precursors in rice endosperm, and improves rice flour characteristics and food processing properties. However, the gene must be expressed to be useful. A deficient mutant allele of PDIL1-1 was introduced into two rice cultivars with different genetic backgrounds (Koshihikari and Oonari). The grain components, agronomic traits, and rice flour and food processing properties of the resulting lines were evaluated. The two breeding lines had similar seed storage protein accumulation, amylose content, and low-molecular-weight metabolites. However, only the Koshihikari breeding line had high flour quality and was highly suitable for rice bread, noodles, and sponge cake, evidence of the formation of high-molecular-weight protein complexes in the endosperm. Transcriptome analysis revealed that mRNA levels of fourteen PDI, Ero1, and BiP genes were increased in the Koshihikari breeding line, whereas this change was not observed in the Oonari breeding line. We elucidated part of the molecular basis of the phenotypic differences between two breeding lines possessing the same mutant allele in different genetic backgrounds. The results suggest that certain genetic backgrounds can negate the beneficial effect of the PDIL1-1 mutant allele. Better understanding of the molecular basis for such interactions may accelerate future breeding of novel rice cultivars to meet the strong demand for gluten-free foods.

Color Doppler shear wave elastography using commercial ultrasound machine with compensated transducer scanning delay.

PURPOSE: Tissue elasticity can be measured and mapped using color Doppler elastography. In a previous study, a binary pattern of shear waves was observed using a color flow imaging (CFI) system with matched pulse Doppler packet size as well as shear wave frequency and displacement condition. In the present study, we demonstrate the possibility of mapping shear wave velocity and resolving phantom elasticity using any commercial ultrasound machine without fulfilling that condition. METHODS: We derive a relation between Doppler autocorrelator integration time and the estimated flow velocity. The underlying principles behind the shear wave shadows captured by a typical modern ultrasound machine are investigated. The ultrasound machine measurement preset is calibrated to remove the effect of transducer array scanning delay in modifying the appearing wavenumber and thus correct the measurement error. RESULTS: The method was used to successfully measure the elasticity of a biological tissue-mimicking phantom and distinguish a stiff phantom from a soft phantom. CONCLUSION: Using this method, the elasticity of a biological tissue-mimicking phantom can be recovered with less strict constraint. As a result, it provides more flexibility to be implemented in common ultrasound machines. This method may be practically used to help identify tissue stiffness-related disease.

Binary Pattern Color Doppler Shear Wave Elastography.

Some studies suggested a correlation between tissue elasticity and diseases, such as Adhesive Capsulitis (AC) of the shoulder. One category of method to measure elasticity is by utilizing Doppler imaging. This paper discusses color Doppler shear wave elastography methods and demonstrated an experiment with biological tissue mimicking phantom. A simulation with binary pattern color Doppler shear wave elastography shows that wavelength of a shear wave with suggested magnitude is equal to four multiple of pitch strip in a color flow image. However, the larger amplitude changes the duty ratio and frequency of the pattern. An experiment with biological tissue mimicking Polyvinyl Alcohol (PVA) phantoms has shown that the binary pattern color Doppler method has successfully recovered shear wave velocity map and calculate the elasticity.Clinical Relevance-The result of experiments presents a possibility of using the method for quantitatively access the stage of tissue stiffness related disease.

Helical toroid phantom for 3D flow imaging investigations.

The medical physics community has hitherto lacked an effective calibration phantom to holistically evaluate the performance of three-dimensional (3D) flow imaging techniques. Here, we present the design of a new omnidirectional, three-component (3-C) flow phantom whose lumen is consisted of a helical toroid structure (4 mm lumen diameter; helically winded for 5 revolutions over a torus with 10 mm radius; 5 mm helix radius). This phantom's intraluminal flow trajectory embraces all combinations of x, y, and z directional components, as confirmed using computational fluid dynamics (CFD) simulations. The phantom was physically fabricated via lost-core casting with polyvinyl alcohol cryogel (PVA) as the tissue mimic. 3D ultrasound confirmed that the phantom lumen expectedly resembled a helical toroid geometry. Pulsed Doppler measurements showed that the phantom, when operating under steady flow conditions (3 ml s-1 flow rate), yielded flow velocity magnitudes that agreed well with those derived from CFD at both the inner torus (-47.6 ± 5.7 versus -52.0 ± 2.2 cm s-1; mean ± 1 S.D.) and the outer torus (49.5 ± 4.2 versus 48.0 ± 1.7 cm s-1). Additionally, 3-C velocity vectors acquired from multi-angle pulsed Doppler showed good agreement with CFD-derived velocity vectors (<7% and 10° difference in magnitude and flow angle, respectively). Ultrasound color flow imaging further revealed that the phantom's axial flow pattern was aligned with the CFD-derived flow profile. Overall, the helical toroid phantom has strong potential as an investigative tool in 3D flow imaging innovation endeavors, such as the development of flow vector estimators and visualization algorithms.

A Deep Learning Approach to Resolve Aliasing Artifacts in Ultrasound Color Flow Imaging.

Despite being used clinically as a noninvasive flow visualization tool, color flow imaging (CFI) is known to be prone to aliasing artifacts that arise due to fast blood flow beyond the detectable limit. From a visualization standpoint, these aliasing artifacts obscure proper interpretation of flow patterns in the image view. Current solutions for resolving aliasing artifacts are typically not robust against issues such as double aliasing. In this article, we present a new dealiasing technique based on deep learning principles to resolve CFI aliasing artifacts that arise from single- and double-aliasing scenarios. It works by first using two convolutional neural networks (CNNs) to identify and segment CFI pixel positions with aliasing artifacts, and then it performs phase unwrapping at these aliased pixel positions. The CNN for aliasing identification was devised as a U-net architecture, and it was trained with in vivo CFI frames acquired from the femoral bifurcation that had known presence of single- and double-aliasing artifacts. Results show that the segmentation of aliased CFI pixels was achieved successfully with intersection over union approaching 90%. After resolving these artifacts, the dealiased CFI frames consistently rendered the femoral bifurcation's triphasic flow dynamics over a cardiac cycle. For dealiased CFI pixels, their root-mean-squared difference was 2.51% or less compared with manual dealiasing. Overall, the proposed dealiasing framework can extend the maximum flow detection limit by fivefold, thereby improving CFI's flow visualization performance.

Contrast-Enhanced Urodynamic Vector Projectile Imaging (CE-UroVPI) for Urethral Voiding Visualization: Principles and Phantom Studies.

OBJECTIVE: To devise a new urodynamic imaging framework that can provide time-resolved visualization of urinary flow and urethral deformation during the initiation phase of voiding. MATERIALS AND METHODS: Contrast-enhanced urodynamic vector projectile imaging (CE-UroVPI) was devised using the principles of high-frame rate ultrasound, microbubble contrast agents, and flow vector mapping. CE-UroVPI was implemented using a research-purpose ultrasound scanner (5 MHz frequency) and commercial contrast agents (USphere Prime). The performance of CE-UroVPI was evaluated using 2 custom-designed deformable urethra phantoms - a healthy model and a diseased model with benign prostatic hyperplasia (BPH) - that respectively simulate urodynamics in the urinary tract with and without mechanical obstruction. The corresponding spatiotemporal urodynamics were investigated and analyzed. RESULTS: Using a frame rate of 1,250 fps that corresponds to 0.8 ms time resolution, CE-UroVPI effectively depicted the transient urodynamic events during the initiation phase of voiding. Anomalous spatiotemporal characteristics were observed in the urodynamics of the BPH-obstructed urethra. Specifically, upstream from the obstruction site, a transient surge in flow speed was observed in the first 100 ms of voiding. Also, downstream from the obstruction site, complex urodnyamics had emerged in the forms of flow jet and vortices. These anomalies were not found in the healthy urethra. CONCLUSION: CE-UroVPI is the first imaging framework that can visualize complex urodynamics over an entire voiding episode including its initiation phase. This new tool may be used to potentially gain new insight into the causal relationships between urethral morphokinetic factors and lower urinary tract symptoms.

Deformable phantoms of the prostatic urinary tract for urodynamic investigations.

PURPOSE: Assessment of urethral dynamics is clinically regarded to be important in analyzing the functional impact of pathological features like urethral obstruction, albeit it is difficult to perform directly in vivo. To facilitate such an assessment, urethra phantoms may serve well as investigative tools by reconstructing urethral dynamics based on anthropomorphic factors. Here, our aim is to design a new class of anatomically realistic, deformable urethra phantoms that can simulate the geometric, mechanical, and hydrodynamic characteristics of the male prostatic urethra. METHODS: A new lost-core tube casting protocol was devised. It first involved the drafting of urethra geometry in computer-aided design software. Next, 3D printing was used to fabricate the urethra geometry and an outer mold. These parts were then used to cast a urinary tract using a polyvinyl alcohol (PVA)-based material (with 26.6 ± 4.0 kPa Young's elastic modulus). After forming a surrounding tissue-mimicking slab using an agar-gelatin mixture (with 17.4 ± 3.4 kPa Young's modulus), the completed urethra phantom was connected to a flow circuit that simulates voiding. To assess the fabricated phantoms' morphology, ultrasound imaging was performed over different planes. Also, color Doppler imaging was performed to visualize the flow profile within the urinary tract. RESULTS: Deformable phantoms were devised for the normal urethra and a diseased urethra with obstruction due to benign prostatic hyperplasia (BPH). During voiding, the short-axis lumen diameter at the verumontanum of the BPH-featured phantom (0.91 ± 0.08 mm) was significantly smaller than that for the normal phantom (2.49 ± 0.20 mm). Also, the maximum flow velocity of the BPH-featured phantom (59.3 ± 5.8 cm/s; without Doppler angle correction) was found to be higher than that of the normal phantom (22.7 ± 9.0 cm/s). CONCLUSION: The fabricated phantoms were effective in simulating urethra deformation resulting from urine passage during voiding. They can be used for mechanistic studies of urethral dynamics and for the testing of urodynamic diagnostic techniques in urology.

A follow-up study for biomass yield QTLs in rice.

The biomass yield (plant weight) of rice fluctuates from year to year. In a previous study, we demonstrated that six quantitative trait loci (QTLs) contribute to the variation in the plant weight of recombinant inbred lines (RILs) of high-yielding Japanese rice cultivars. However, it remains unclear whether the effects of those QTLs are stable over multiple years. Therefore, we evaluated the effect of the alleles on the plant weight of RILs over multiple years, including a change of fertilization level (i.e., in different environments). Even though the biomass yields of all RILs fluctuated among environments, RILs that were selected on the basis of the genotypes of the detected QTLs had a stable rank order of plant weight that corresponded to their genotypes. This multiple-environment experiment reveals the highly significant contribution of both genotypic and environmental variances to the observed variance in plant weight. A marginally significant QTL-environment interaction was detected at only one of the six QTLs, with a subtle contribution. These results support the idea that the biomass yield of rice can be improved through QTL-based allele selection.

Vector Flow Visualization of Urinary Flow Dynamics in a Bladder Outlet Obstruction Model.

Voiding dysfunction that results from bladder outlet (BO) obstruction is known to alter significantly the dynamics of urine passage through the urinary tract. To non-invasively image this phenomenon on a time-resolved basis, we pursued the first application of a recently developed flow visualization technique called vector projectile imaging (VPI) that can track the spatiotemporal dynamics of flow vector fields at a frame rate of 10,000 fps (based on plane wave excitation and least-squares Doppler vector estimation principles). For this investigation, we designed a new anthropomorphic urethral tract phantom to reconstruct urinary flow dynamics under controlled conditions (300 mm H2O inlet pressure and atmospheric outlet pressure). Both a normal model and a diseased model with BO obstruction were developed for experimentation. VPI cine loops were derived from these urinary flow phantoms. Results show that VPI is capable of depicting differences in the flow dynamics of normal and diseased urinary tracts. In the case with BO obstruction, VPI depicted the presence of BO flow jet and vortices in the prostatic urethra. The corresponding spatial-maximum flow velocity magnitude was estimated to be 2.43 m/s, and it is significantly faster than that for the normal model (1.52 m/s) and is in line with values derived from computational fluid dynamics simulations. Overall, this investigation demonstrates the feasibility of using vector flow visualization techniques to non-invasively examine internal flow characteristics related to voiding dysfunction in the urethral tract.

Physiological and Biochemical Responses to Continuous Saline Irrigation Inside the Abdominal Cavity in Anesthetized Pigs.

BACKGROUND: Water-filled laparoendoscopic surgery (WaFLES) has been proposed as a novel surgical system achieving a wide surgical field in the intra- and extraperitoneal space with continuous irrigation of isotonic fluid into the field. Despite its technical feasibility and advantages, the safety of the technique, particularly with respect to physiological functions, has not been evaluated. METHODS: Various types of minor abdominal surgeries were performed under general anesthesia in nine adult pigs either by conventional laparoscopy (n = 3) or WaFLES (n = 6). In addition to esophageal temperature and body weight, cardiorespiratory variables such as blood pressure, heart rate, and arterial blood gas parameters were compared before and after the surgeries. Blood samples were obtained for assessing changes in biochemical parameters before and after the surgeries. RESULTS: Three to seven hours of various surgeries were completed without critical cardiorespiratory events in all animals. Oxygenation and ventilation were maintained regardless of the techniques used for the surgeries. A minor increase of body weight (2.5% of initial body weight), metabolic acidosis, hyperkalemia, and impaired hepatic function were observed after WaFLES surgeries. CONCLUSIONS: The preliminary study indicated no serious immediate adverse effects of the WaFLES technique.