Low Pulse Repetition Frequency Research Articles

Parental Reflective Functioning on the Parent Development Interview: A narrative review of measurement, association, and future directions.

A caregiver's capacity to mentalize is thought to be one of the most important features of secure parent-child relationships. Parental mentalizing can be measured using the Reflective Functioning (RF) coding system applied to the Parent Development Interview (PDI). In this narrative review, we summarize the research using this measure and synthesize what has been learnt about the predictors, correlates and sequelae of parental RF. Studies have consistently shown that PRF on the PDI is associated with both parent and child attachment and is an important factor in the intergenerational transmission of attachment. It is also related to the quality of parental representations, parent-child interactions, and child outcomes. While a number of social and clinical risk factors are associated with lower PRF, it is difficult to disentangle the unique contribution of each of these. We discuss these findings and present the direction of future work that is planned to expand and refine the PRF scale for the PDI.

Facilitatory effect of low-pulse repetition frequency ultrasound on release of extracellular vesicles from cultured myotubes.

Extracellular vesicles (EVs) serve as carriers of intracellular factors with therapeutic effects, including tissue regeneration and attenuation of inflammatory responses. The majority of EVs in vivo are derived from skeletal muscle, which is reported to have anti-inflammatory effects. While high-intensity pulsed ultrasound (US) irradiation has been shown to promote EV secretion from myotubes, the impact of pulse repetition frequency, a US parameter affecting pulse length, on EV release remains unclear. This study aimed to investigate the impact of pulse repetition frequency of US on the release of EVs from myotubes. C2C12 myoblasts were used in this study. After differentiation into C2C12 myotubes, US was performed for 5min at an intensity of 3.0W/cm2, duty cycle of 20%, acoustic frequency of 1MHz, and different pulse repetition frequencies (100Hz, 10Hz, or 1Hz). After 12h, EVs and cells were collected for subsequent analyses. US did not cause a reduction in cell viability across all US groups compared to the control. The concentration of EVs was significantly higher in all US groups compared to the control group. In particular, the highest increase was observed in the 1-Hz group on EV concentration as well as intracellular Ca2+ level. This study investigated the effect of three different pulse repetition frequencies of US on the release of EVs from cultured myotubes. It is concluded that a low-pulse repetition frequency of 1Hz is the most effective for enhancing EV release from cultured myotubes with pulsed ultrasound.

Experimental Investigation of Excitation Strategies for Erosion by Cavitation Histotripsy

Abstract Cavitation histotripsy has been applied to the disintegration on the surface of soft tissue in a well-controlled manner. Its performance was assumed to be determined by the acoustic pressure alone. Long pulse duration with low pulse repetition frequency (PRF) can also successfully generate erosion. This study was designed to investigate the excitation strategies for cavitation histotripsy-induced erosion. The erosion area and volumes produced by cavitation histotripsy on the alginate gel phantom using single-frequency, dual-frequency, and two pulsed excitations at the same power output at the PRF of 1 Hz and 200 Hz were compared. Dual-frequency excitation can improve the erosion at all PRFs, while pulsed excitations decrease it at the PRF of 200 Hz. Using both pulsed and dual-frequency excitations has more erosion areas than using single-frequency at a PRF of 1 Hz. In comparison, although the induced erosion areas using the pulsed excitations are larger than those of single-frequency at the PRF of 200 Hz, the erosion volumes are much lower than those of dual-frequency excitation. It suggests that a sufficient long pulse duration is another important factor for the performance of cavitation histotripsy. Dual-frequency excitation or amplitude modulation by the low-frequency sinusoidal envelope can achieve more erosion than that produced by single-frequency excitation at the same power output in a wide range of PRFs.

Effects of pulse repetition frequency on bubble cloud characteristics and ablation in single-cycle histotripsy

Objective. Histotripsy is a cavitation-based ultrasound ablation method in development for multiple clinical applications. This work investigates the effects of pulse repetition frequency (PRF) on bubble cloud characteristics and ablative capabilities for histotripsy using single-cycle pulsing methods. Approach. Bubble clouds produced by a 500 kHz histotripsy system at PRFs from 0.1 to 1000 Hz were visualized using high-speed optical imaging in 1% agarose tissue phantoms at peak negative pressures, p-, of 2–36 MPa. Main results. Results showed a decrease in the cavitation cloud threshold with increasing PRF, ranging from 26.7 ± 0.5 MPa at 0.1 Hz to 15.0 ± 1.9 MPa at 1000 Hz. Bubble cloud analysis showed cavitation clouds generated at low PRFs (0.1–1 Hz) were characterized by consistently dense bubble clouds (41.7 ± 2.8 bubbles mm−2 at 0.1 Hz), that closely matched regions of the focus above the histotripsy intrinsic threshold. Bubble clouds formed at higher PRFs measured lower cloud densities (23.1 ± 4.0 bubbles mm−2 at 1000 Hz), with the lowest density measured for 10 Hz (8.8 ± 4.1 bubbles mm−2). Furthermore, higher PRFs showed increased pulse-to-pulse correlation, characteristic of cavitation memory effects; however, bubble clouds still filled the entire volume of the focus due to their initial density and enhanced bubble expansion from the restimulation of residual nuclei at the higher PRFs. Histotripsy ablation assessed through lesion analysis in red blood cell (RBC) phantoms showed higher PRFs generated lesions with lower adherence to the initial focal region compared to low PRF ablations; however, no trend of decreasing ablation efficiency with PRF was observed, with similar efficiencies observed for all the PRFs tested in this study. Significance. Notably, this result is different than what has previously been shown for shock-scattering histotripsy, which has shown decreased ablation efficiencies at higher PRFs. Overall, this study demonstrates the essential effects of PRF on single-cycle histotripsy procedures that should be considered to help guide future histotripsy pulsing strategies.

Performance characterization of a novel hybrid dosimetry insert for simultaneous spatial, temporal, and motion-included dosimetry for MR-linac.

Several (online) adaptive radiotherapy procedures are available to maximize healthy tissue sparing in the presence of inter/intrafractional motion during stereotactic body radiotherapy (SBRT) on an MR-linac. The increased treatment complexity and the motion-delivery interplay during these treatments require MR-compatible motion phantoms with time-resolved dosimeters to validate end-to-end workflows. This is not possible with currently available phantoms. Here, we demonstrate a new commercial hybrid film-scintillator cassette, combining high spatial resolution radiochromic film with four time-resolved plastic scintillator dosimeters (PSDs) in an MRI-compatible motion phantom. First, the PSD's performance for consistency, dose linearity, and pulse repetition frequency (PRF) dependence was evaluated using an RW3 solid water slab phantom. We then demonstrated the MRI4D scintillator cassette's suitability for time-resolved and motion-included quality assurance for adapt-to-shape (ATS), trailing, gating, and multileaf collimator (MLC) tracking adaptations on a 1.5 T MR-linac. To do this, the cassette was inserted into the Quasar MRI4D phantom, which we used statically or programmed with artificial and patient-derived motion. Simultaneously with dose measurements, the beam-gating latency was estimated from the time difference between the target entering/leaving the gating window and the beam-on/off times derived from the time-resolved dose measurements. Experiments revealed excellent detector consistency (standard deviation 0.6%), dose linearity (R2 = 1), and only very low PRF dependence ( 0.4%). The dosimetry cassette demonstrated a near-perfect agreement during an ATS workflow between the time-resolved PSD and treatment planning system (TPS) dose (0%-2%). The high spatial resolution film measurements confirmed this with a 1%/1-mm local gamma pass-rate of 90%. When trailing patient-derived prostate motion for a prostate SBRT delivery, the time-resolved cassette measurements demonstrated how trailing mitigated the motion-induced dose reductions from 1%-17% to 1%-2% compared to TPS dose. The cassette's simultaneously measured spatial dose distribution highlighted the dosimetric gain of trailing by improving the 3%/3-mm local gamma pass-rates from 80% to 97% compared to the static dose. Similarly, the cassette demonstrated the benefit of real-time adaptations when compensating patient-derived respiratory motion by showing how the TPS dose was restored from 2%-56% to 0%-12% (gating) and 1%-26% to 1%-7% (MLC tracking) differences. Larger differences are explainable by TPS-PSD coregistration uncertainty combined with a steep dose gradient outside the PTV. The cassette also demonstrated how the spatial dose distributions were drastically improved by the real-time adaptations with 1%/1-mm local gamma pass-rates that were increased from 8 to 79% (gating) and from 35 to 89% (MLC tracking). The cassette-determined beam-gating latency agreed within 12 ms with the ground truth latency measurement. Film and PSD dose agreed well for most cases (differences relative to TPS dose 4%), while film-PSD coregistration uncertainty caused relative differences of 5%-8%. This study demonstrates the excellent suitability of a new commercial hybrid film-scintillator cassette for simultaneous spatial, temporal, and motion-includeddosimetry.

Detection of hypersonic weak targets by high pulse repetition frequency radar based on multi‐hypothesis fuzzy‐matching radon transform

AbstractFor the integration detection of near space hypersonic weak targets by high pulse repetition frequency (PRF) radar, a novel method named Multi‐Hypothesis Fuzzy‐Matching Radon transform (MHFM‐RT) is proposed for the near space hypersonic target detection and tracking. For remote hypersonic target detection, to avoid range ambiguity, current radars always use a low PRF mode, which limit the number of pulse accumulations. Using the high PRF mode, the fuzzy folding will appear in the target range measurements when target trajectory crosses range fuzzy intervals. Therefore, there is a contradiction between range ambiguity and energy accumulation. The proposed method is used to match the fuzzy measurements, so as to realise the correct integration in the condition of range ambiguity. Firstly, considering the need of range ambiguity resolution, the mode of staggered PRF is used. Secondly, the first frame measurements are periodically extended for multiple‐fuzzy hypothesis. Finally, the weak target track is accumulated in MHFM‐RT domain, and the signal integration and ambiguity resolution can be realised simultaneously. The proposed method expands the Variable‐Diameter‐Arc‐Helix Radon transform (VDAH‐RT) method to fuzzy folding conditions. Compared with the existing methods, for 7‐scan measurements non‐coherent integration, the detection sensitivity of the proposed method is about 0.5–1 dB higher than that of the IMM hybrid filter algorithm, and about 1 dB higher than that of the RHT‐TBD approach, and it needs less storage space and has higher detection probability.

Ultrasound-Induced Tumor Perfusion Changes and Doxorubicin Delivery: A Study on Pulse Length and Pulse Repetition Frequency.

To investigate the appropriate combination of pulse length (PL) and pulse repetition frequency (PRF) when performing ultrasound stimulated microbubble (USMB) to enhance doxorubicin (DOX) delivery to tumors. A total of 48 tumor-bearing mice were divided into four groups, namely groups A-D. The mice in groups B-D were treated with chemotherapy and USMB treatment with different combinations of PL and PRF, and group A was control. Contrast-enhanced ultrasound imaging was conducted to analyze tumor blood perfusion. Fluorescence microscopy and high-performance liquid chromatography were used to qualitatively and quantitatively analyse DOX release. The structural changes of tumors were observed under light microscope and transmission electron microscope. Furthermore, another 24 tumor-bearing mice were treated with sonochemotherapy and some related inflammatory factors were measured to explore the underlying mechanism. With PL of three cycles and PRF of 2 kHz, the tumor perfusion area ratio increased by 26.67%, and the DOX concentration was 4.69 times higher than the control (P < .001). With PL of 34.5 cycles and PRF of 200 Hz, the tumor perfusion area ratio decreased by 12.7% and DOX did not exhibit increased extravasation compared with the control. Microvascular rupture and hemorrhage were observed after long PL and low PRF treatment. While vasodilation and higher levels of some vasodilator inflammatory factors were found after treatment with short PL and high PRF. USMB treatment using short PL and high PRF could enhance tumor blood perfusion and increase DOX delivery, whereas long PL and low PRF could not serve the same purpose.

Accuracy Improvement of High-Resolution Wide-Swath Spaceborne Synthetic Aperture Radar Imaging with Low Pule Repetition Frequency

For a single-channel spaceborne synthetic aperture radar (SAR), the usage of a low pulse repetition frequency (PRF) is an effective technical way to extend the range swath. The sub-aperture imaging strategy is usually used to solve the problem of azimuth spectrum aliasing under the condition of a low PRF. However, the required up-sampling processing before the coherent synthesis of sub-images will lead to spectrum discontinuity between adjacent sub-images, which leads to an obvious grating lobe phenomenon after the process of sub-image synthesis, resulting in a significant decrease in image quality. For this issue, a high-resolution wide-swath (HRWS) imaging algorithm for a spaceborne SAR with a low PRF is proposed in this paper based on optimal spectrum shift processing. First, each sub-aperture is imaged using the typical range migration algorithm (RMA), and then all sub-images are up-sampled at the same time. Then, based on the criterion of the minimum grating lobe, the optimal spectrum shift is estimated. Finally, the spectrum of all sub-images is shifted and then all the shifted sub-images are synthesized coherently. The simulation data processing results verify the effectiveness of the proposed method.

Deep-learning-assisted and GPU-accelerated vector Doppler imaging with aliasing-resistant velocity estimation

Vector flow imaging is a diagnostic ultrasound modality that is suited for the visualization of complex blood flow dynamics. One popular way of realizing vector flow imaging at high frame rates over 1000 fps is to apply multi-angle vector Doppler estimation principles in conjunction with plane wave pulse-echo sensing. However, this approach is susceptible to flow vector estimation errors attributed to Doppler aliasing, which is prone to arise when a low pulse repetition frequency (PRF) is inevitably used due to the need for finer velocity resolution or because of hardware constraints. Existing dealiasing solutions tailored for vector Doppler may have high computational demand that makes them unfeasible for practical applications. In this paper, we present the use of deep learning and graphical processing unit (GPU) computing principles to devise a fast vector Doppler estimation framework that is resilient against aliasing artifacts. Our new framework works by using a convolutional neural network (CNN) to detect aliased regions in vector Doppler images and subsequently applying an aliasing correction algorithm only at these affected regions. The framework’s CNN was trained using 15,000 in vivo vector Doppler frames acquired from the femoral and carotid arteries, including healthy and diseased conditions. Results show that our framework can perform aliasing segmentation with an average precision of 90 % and can render aliasing-free vector flow maps with real-time processing throughputs (25–100 fps). Overall, our new framework can improve the visualization quality of vector Doppler imaging in real-time.

An Operational Processing Framework for Spaceborne SAR Formations

The paper proposes a flexible and efficient wavenumber domain processing scheme suited for close formations of low earth orbiting (LEO) synthetic aperture radar (SAR) sensors hosted on micro-satellites or CubeSats. Such systems aim to generate a high-resolution image by combining data acquired by each sensor with a low pulse repetition frequency (PRF). This is usually performed by first merging the different channels in the wavenumber domain, followed by bulk focusing. In this paper, we reverse this paradigm by first upsampling and focusing each acquisition and then combining the focused images to form a high-resolution, unambiguous image. Such a procedure is suited to estimate and mitigate artifacts generated by incorrect positioning of the sensors. An efficient wave–number method is proposed to focus data by adequately coping with the orbit curvature. Two implementations are provided with different quality/efficiency. The image quality in phase preservation, resolution, sidelobes, and ambiguities suppression is evaluated by simulating both point and distributed scatterers. Finally, a demonstration of the capability to compensate for ambiguities due to a small across-track baseline between sensors is provided by simulating a realistic X-band multi-sensor acquisition starting from a stack of COSMO-SkyMed images.

Phase Bias Estimation and Imaging for High-Squint Multichannel SAR in Azimuth

High-squint multichannel synthetic aperture radar (SAR) in azimuth can overcome the constraint of minimum antenna area in the traditional single-channel classical SAR system, and thereby it would be much more flexible to achieve high-resolution and wide-swath (HRWS) imaging than broadside SAR. However, for the high-squint multichannel SAR imaging mode, the squint angle causes Doppler centroid varying with the range frequency, which can further result in much more complicated problem of the spectral folding after down-sampled with low PRF. Meanwhile, the Doppler centroid frequency is indispensable for the estimation of phase bias and unambiguous signal reconstruction among received channels. In this paper, the impact of high-squint angle on the aliased Doppler spectrum and Doppler centroid is analyzed in detail. Then, a novel approach to phase bias estimation as well as the underlying signal processing in the case of high-squint multichannel SAR imaging mode in azimuth is proposed. Simulation results validate the effectiveness of the proposed processing flowchart for high-squint multichannel SAR.

Multi-Channel SAR Imaging on Cruising Ships with Sub-Orbital Spaceplane

A multi-channel synthetic aperture radar (SAR) on board a spaceplane orbiting near the top of the atmosphere is proposed to acquire images of cruising ships. Low pulse repetition frequency (PRF) is required for high-resolution wide-swath (HRWS) imaging, leading to inevitable problems of azimuth spectrum aliasing (ASA) and azimuth Doppler ambiguity (ADA). In this work, we propose a phase matching technique to solve the ASA problem in restoring the azimuth spectrum. A multi-stage compressive-sensing (CS) technique is also proposed to solve both ADA and ASA problems. Five similar types of cruising ship are simulated to verify the efficacy of the proposed approach, at different levels of signal-to-noise ratio. Indices of geometry match, intensity match, and structural similarity are used to identify different ships from the acquired SAR images.

Modulation of Pain-Associated Behaviors in Sickle Mice Using Low-Intensity Transcranial Focused Ultrasound

Pain is a major comorbidity of sickle cell disease (SCD), which is the most genetic diathesis affecting mostly African Americans in the United States. Opioids are used to reduce pain, however the increased risk of drug abuse, overdose, and addiction has led to an urgent need to develop non-pharmacologic approaches to treat pain safely and effectively. Low-intensity transcranial focused ultrasound (tFUS) is a non-invasive brain stimulation method featured with high precision and deep brain penetration, which holds great promise in managing pain. Here, we report how tFUS modulates pain-related behaviors in wild-type mice and humanized sickle mice by targeting specific brain regions involved in the processing and perception of pain. We used wild-type mice (C57BL/6J) and humanized transgenic BERK mice on a mixed genetic background (FVB/N, 129, DBA/2, C57BL/6, and Black Swiss) murine α and β globin knockouts (α−/−, β−/−) with sickle mice expressing >99% human sickle hemoglobin S (HbS), demonstrating severe SCD. Mice were generated in-house by cross-breeding homozygous (SS) males with hemizygous (AS) females. All studies in mice were approved by IACUC of Carnegie Mellon University and University of California at Irvine, and complied with NIH guidelines. The tFUS was applied to hindlimb of the primary somatosensory cortex (S1HL) at the left hemisphere of the brain, and the effect of tFUS stimulation was further investigated by comparing with control groups such as sham treatment (applying tFUS to a vicinity region of S1HL) and negative control (not applying tFUS while keeping the same experimental procedures). A modified hot-plate behavior test was used to assess unilateral effects of tFUS by comparing withdrawal responses of contralateral (right) and ipsilateral (left) hind paws. The nociceptive responses to noxious heat stimuli were blindly assessed and analyzed in terms of ∆hind paw withdrawal latency (∆hPWL) (s) (= contralateral hPWL- ipsilateral hPWL) before and after specific treatment. We observed a marked reduction in sensitivity to noxious heat stimuli in tFUS-treated male and female wild-type mice. Compared to the baseline value, tFUS stimulation with lower pulse repetition frequency (PRF) (i.e., 40 Hz) at left S1HL led to a significant increase in the averaged ∆hPWL (***p<0.001, N=8 male wild-type mice for 3 min after tFUS; *p<0.05, N=8 for 8 min after tFUS; **p<0.01, N=8 female wild-type mice for 3 min after tFUS; *p<0.05, N=8 for 8 min after tFUS; Friedman test), but not with the sham treatment (p>0.05, N=8 male and female wild-type mice for 3 and 8 min after sham treatment; Friedman test). Next, we assessed whether tFUS could modulate heat hyperalgesia in female sickle mice. Fig. 1 shows that tFUS stimulation with PRF of 40 Hz at left S1HL resulted in a significant change of ∆hPWL in the sickle mice compared to pre-stimulation baseline (**p<0.01, N=10 for 3 and 8 min after tFUS; Friedman test). This effect was specific to tFUS stimulation as a remarkable difference of averaged ∆hPWL between the sham treatment/negative control and pre-sham/negative control baseline was not observed (p>0.05, N=10 for 3 and 8 min after sham treatment and negative control; Friedman test), which suggests that tFUS stimulation with a lower PRF at S1HL can attenuate heat hyperalgesia in the sickle mice. In addition, when tFUS with higher PRF (i.e., 3 kHz) was applied at left S1HL, we found a negative averaged value of ∆hPWL based on the decreased contralateral (right) hind paw latency compared to latency of ipsilateral (left) hind paw, which is significantly different from the behavioral responses to heat stimuli with the PRF of 40 Hz (###p<0.001, N=10 for 3 min after tFUS with PRF of 40 and 3 kHz; ####p<0.0001, N=10 for 8 min after tFUS with PRF of 40 and 3 kHz; Kruskal-Wallis test). Since, tFUS stimulation with a higher PRF leads to exacerbation of heat hyperalgesia in the sickle mice, it is critical to optimize the level of PRF to achieve an analgesic effect. We show that tFUS stimulation can be effective in non-invasively attenuating heat pain sensitivity in wild-type mice and heat hyperalgesia in humanized sickle mice at a lower PRF, but exacerbating at a higher PRF by stimulating pre-identified pain-processing brain circuit. These observations have a translational potential for establishing an effective, non-addictive, non-pharmacological, non-invasive device-based neuromodulation technique for managing sickle cell pain. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Effects of pulse repetition frequency on bubble cloud characteristics and ablation for single-cycle histotripsy

Histotripsy is a cavitation-based focused ultrasound ablation method in development for multiple clinical applications. This work investigates the effects of pulse repetition frequency (PRF) on histotripsy bubble cloud characteristics and ablative capabilities for single cycle histotripsy. Bubble clouds produced by a 500 kHz histotripsy system at PRF’s from 0.1 to 1000 Hz were visualized using high speed imaging in 1% agarose phantoms. Cloud images were analyzed to determine bubble cloud density (bubbles/mm2) and pulse-to-pulse bubble correlation. Ablation was assessed through lesion analysis in red blood cell (RBC) phantoms. Results showed cavitation clouds generated at low PRF were characterized by consistently dense bubble clouds (49.6 ± 7.7 bubbles/mm2, 1 Hz) that closely matched regions above the histotripsy intrinsic threshold. Bubble clouds formed at high PRF had significantly lower cloud density (20.0 ± 8.3 bubbles/mm2, 1000 Hz). In addition, bubbles in higher PRF clouds had significantly increased pulse-to-pulse correlation, characteristic of what has been reported as the cavitation memory effect. Results from RBC ablation showed that higher PRF generated lesions had lower adherence to the focal region and less repeatability compared to low PRF ablations. This study demonstrates essential differences in bubble cloud characteristics that will help guide future histotripsy pulsing strategies.

Evolutions of repetitively pulsed positive streamer discharge in electronegative gas mixtures at high pressure

Electronegative gas components and gas pressure significantly change residual charge dynamics, which are critical for pulse-periodic streamer discharge behaviors. Evolutions of repetitively pulsed positive streamer discharge and the streamer-to-spark transitions were investigated at high pressures and compared between typical weak (O2) and strong (SF6) electronegative gas mixtures. Pulse-sequence resolved electrical and optical diagnostics were implemented to capture discharge evolutions in long pulse trains. We observe that streamer inception and propagation under subsequent pulses in N2 and N2–O2 mixtures are similar, including the earlier inception of the primary streamer and the accelerated propagation of the secondary streamer. The repetitively pulsed breakdown is extended to the low pulse repetition frequency region with the addition of O2. Discharge evolutions are unexpectedly different in N2–SF6 mixtures. Subsequent discharge channels prefer to propagate around the periphery of the inception cloud region with large radial deviations. Another difference is the precursor channel identified besides multiple streamer channels. Effects of electronegative gas on streamer evolutions under positive repetitive pulses have been qualitatively analyzed. Collisional electron detachment and photo-ionization are crucial in N2–O2 mixtures. With the presence of strong electronegative gas (SF6), the leader formation is probably induced by the earlier corona inception and longer voltage stressing period under following pulses in a pulse train, which are caused by the strong electronegativity of SF6 and the small ion mobility.

High-Resolution Wide-Swath Ambiguous Synthetic Aperture Radar Modes for Ship Monitoring

This paper proposes two high-resolution, wide-swath synthetic aperture radar (SAR) acquisition modes for ship monitoring that tolerate ambiguities and do not require digital beamforming. Both modes, referred to as the low pulse repetition frequency (PRF) and the staggered (high PRF) ambiguous modes, make use of a wide elevation beam, which can be obtained by phase tapering. The first mode is a conventional stripmap mode with a PRF much lower than the nominal Doppler bandwidth, allowing for the imaging of a large swath, because the ships’ azimuth ambiguities can be recognized as they appear at known positions. The second mode exploits a continuous variation of the pulse repetition interval, with a mean PRF greater than the nominal Doppler bandwidth as the range ambiguities of the ships are smeared and are unlikely to determine false alarms. Both modes are thought to operate in open sea surveillance, monitoring Exclusive Economic Zones or international waters. Examples of implementation of both modes for TerraSAR-X show that ground swaths of 120 km or 240 km can be mapped with 2 m2 resolution, ensuring outstanding detection performance even for small ships. The importance of resolution over noise and ambiguity level was highlighted by a comparison with ScanSAR modes that image comparable swaths with better noise and ambiguity levels but coarser resolutions.

MP04-02 ANALYSIS OF EX-VIVO HUMAN BPH TISSUE TREATED BY HISTOTRIPSY: DOSE AND PARAMETER EFFECTS

You have accessJournal of UrologyCME1 May 2022MP04-02 ANALYSIS OF EX-VIVO HUMAN BPH TISSUE TREATED BY HISTOTRIPSY: DOSE AND PARAMETER EFFECTS Zorawar Singh, Yashwanth N. Kumar, Yak-Nam Wang, Adam Maxwell, Matthew Bruce, Rishi Sekar, Eli Vlaisavljevich, Lawrence D. True, and George R. Schade Zorawar SinghZorawar Singh More articles by this author , Yashwanth N. KumarYashwanth N. Kumar More articles by this author , Yak-Nam WangYak-Nam Wang More articles by this author , Adam MaxwellAdam Maxwell More articles by this author , Matthew BruceMatthew Bruce More articles by this author , Rishi SekarRishi Sekar More articles by this author , Eli VlaisavljevichEli Vlaisavljevich More articles by this author , Lawrence D. TrueLawrence D. True More articles by this author , and George R. SchadeGeorge R. Schade More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002521.02AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Histotripsy is a promising alternative to more invasive procedures for the treatment of benign prostatic hyperplasia (BPH). However, in a phase 1 clinical trial, histotripsy failed to provide objective improvements in urinary function. One explanation may be that the clinical trial pulse parameters, optimized in a canine model, do not translate to more fibrotic human prostates. We aimed to evaluate the efficacy of different histotripsy parameter settings to identify a more efficacious exposure in ex-vivo human BPH tissue (EVHP). METHODS: Deidentified EVHP tissue specimens (n=17) were treated with an 18 element 700kHz cavitation histotripsy transducer, which approximated the device used in the prior clinical trial, and a 1.5MHz boiling histotripsy (BH) transducer. Three different histotripsy exposures were compared: 1) a high pulse repetition frequency (PRF) (approximating the clinical system cavitation cloud histotripsy [CCH]), 2) low PRF CCH and 3) 1Hz PRF BH. Treatment effectiveness was evaluated by measuring pre vs. post treatment Young’s modulus through shear wave elastography (SWE) and histologic analysis (H&E, Masson’s Trichome) of the targeted area. The dose was standardized at 30s/mm and escalated as required to note a significant change in SWE. RESULTS: At the given dose of 30s/mm, BH treatments resulted in a significant 40.1% reduction in SWE Young’s modulus (Figure 1A) p < 0.001. At this dose, neither of the CCH parameter settings (500Hz and 10Hz) resulted in a significant reduction in the Young’s modulus with % changes of differences of 3.1% (p = .83) and -5% (p = .08), respectively. For CCH settings, greater exposure times (up to 90s) did result in significant stiffness reduction of 12.5% (p = 0.04) and 41.1% (p < 0.001) for 500Hz and 10Hz parameter settings, respectively. On histology (Figure 1B), at 30s/mm, the CCH parameter settings resulted in minimal intermittent damage while BH treatments caused near complete ablation. At increasing doses, CCH was also capable of causing complete liquefactive cavity formation. CONCLUSIONS: BH parameters applied in this study resulted in more complete ablation of EVH tissue in comparison to CCH parameters. Additionally, histotripsy treatment parameters similar to those applied with a previous clinical system did not produce consistent ablation of EVHP possibly explaining trial results. Source of Funding: None © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e56 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Zorawar Singh More articles by this author Yashwanth N. Kumar More articles by this author Yak-Nam Wang More articles by this author Adam Maxwell More articles by this author Matthew Bruce More articles by this author Rishi Sekar More articles by this author Eli Vlaisavljevich More articles by this author Lawrence D. True More articles by this author George R. Schade More articles by this author Expand All Advertisement PDF DownloadLoading ...

Resolving Doppler Ambiguity of High-Speed Moving Targets via FDA-MIMO Radar

To address the problem of Doppler ambiguity in low pulse repetition frequency (PRF) radar, we propose the use of frequency diverse array multiple-input multiple-output (FDA-MIMO) radar to detect high-speed moving targets. This method does not require the radar to transmit multiple-PRF pulses. The possible Doppler ambiguity is resolved by exploiting the multicarrier characteristics of FDA-MIMO radar. The effectiveness of the proposed method is verified by simulation results.

MIMO SBR via Code Division Multiplexing for Track While Simultaneous Search

This article outlines the archetype of a novel SpaceBorne Radar (SBR) in the Ka-band for space situational awareness (SSA) based on a code-division multiplexing (CDM) multiple-input–multiple-output (MIMO) payload transceiver. Considering small-size hypervelocity debris, the functional architecture of the fully polarimetric SBR is described, including key comparisons with previous works based on single-input–multiple-output (SIMO) configurations. SBR operations are clarified via timing hierarchies in surveillance mode, the complex data hypercube structure, and the low pulse repetition frequency (L-PRF) range and range rate search (RRRS) entailing a track while simultaneous search (TWSS) contacts collection strategy. Ancillary details on the SBR functional architecture provide paramount insights to ponder critical MIMO aspects and pave the way for key research and development efforts. Finally, numerical results provide a proof of concept for the signal processor upstream the constant false alarm rate-like (CFAR-like) detection block.

HRWS SAR Narrowband Interference Mitigation Using Low-Rank Recovery and Image-Domain Sparse Regularization

Synthetic aperture radar (SAR), as a wideband radar system, may be subject to strong interferences with a variety of signals. The narrowband interference (NBI) exemplifies the most typical of its kind, such as the form of radio frequency interference (RFI). With the development of SAR imaging technology, the high-resolution wide-swath (HRWS) imagery technology now reaches its maturity to finally take shape in current SAR systems. To obtain HRWS images, the multichannel SAR (MC-SAR) system has been employed to tackle the contradictory requirements for both high resolution and low pulse repetition frequency (PRF). Previous interference methods focused on single-channel SAR systems and few research works for MC-SAR systems. In this article, we first derive a new interference-mitigation model for HRWS SAR systems and conclude that the low-rank property of the NBI is suitable for MC-SAR systems. Then we employ an image-domain sparse regularization to protect the real echoes of the SAR system and mitigate the NBIs by solving the low-rank recovery problems of NBIs. Also, the MC-SAR system errors are further taken into account as a measure for our method’s practical applicability. Finally, the real SAR data is used to demonstrate the effectiveness of the proposed method.