IEEE transactions on ultrasonics, ferroelectrics, and frequency control最新文献_第4页

Delivery of Cavitation Therapy With a Modified Clinical Scanner: In Vitro Evaluation

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-29 DOI: 10.1109/TUFFC.2025.3536932

Lance H. De Koninck;Kaleb S. Vuong;Seonghun Shin;Jeffry E. Powers;Michalakis A. Averkiou

{"title":"Delivery of Cavitation Therapy With a Modified Clinical Scanner: In Vitro Evaluation","authors":"Lance H. De Koninck;Kaleb S. Vuong;Seonghun Shin;Jeffry E. Powers;Michalakis A. Averkiou","doi":"10.1109/TUFFC.2025.3536932","DOIUrl":"10.1109/TUFFC.2025.3536932","url":null,"abstract":"In this study, we design and implement pulses [1.67 MHz, 20–1000 cycles, 0.8–2.5 MPa, and 5–100 ms pulse repetition time (PRT)] suitable for microbubble cavitation treatments with a phased array of a clinical ultrasound scanner. A range of acoustic parameters was evaluated in a tissue-mimicking phantom with suspended Sonazoid microbubbles. Hydrophone measurements were used to optimize the transmit beamforming. A passive cavitation detection (PCD) system was designed to measure the microbubble scattered signals over a 1 s exposure. Postprocessing of the scattered signals evaluated frequency content to extract broadband energy and calculate the inertial cavitation dose (ICD). ICD was maximized at 1000 cycles (maximum pulse length), 5 ms (fastest firing rate), and 2.5 MPa peak negative pressure (PNP) (maximum pressure). Inertial cavitation was only sustained for about three pulses (out of hundreds fired) occurring within the first 100 ms of treatment. Temporal analysis of the first 1000-cycle pulse revealed that broadband energy is sustained for the entire pulse. We also demonstrate that while inertial cavitation is possible with clinically available pulse wave Doppler settings, ICD can be significantly increased using the new conditions suggested in this work. We have delivered successful image-guided cavitation treatment after modifying a clinical scanner and monitored the cavitation dose with a PCD system on a gel phantom with suspended microbubbles. We plan to apply this technique in vivo in animal tumor models next. This work demonstrates the first implementation of long, high-pressure pulses on a clinical scanner that users can optimize for cavitation treatments.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"351-361"},"PeriodicalIF":3.0,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Frequency-Domain Decoding of Cascaded Dual- Polarity Waves for Ultrafast Ultrasound Imaging

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-28 DOI: 10.1109/TUFFC.2025.3534429

Charlotte L. Nawijn;Joosje M. K. de Bakker;Tim Segers;Chris L. de Korte;Michel Versluis;Anne E. C. M. Saris;Guillaume Lajoinie

{"title":"Frequency-Domain Decoding of Cascaded Dual- Polarity Waves for Ultrafast Ultrasound Imaging","authors":"Charlotte L. Nawijn;Joosje M. K. de Bakker;Tim Segers;Chris L. de Korte;Michel Versluis;Anne E. C. M. Saris;Guillaume Lajoinie","doi":"10.1109/TUFFC.2025.3534429","DOIUrl":"10.1109/TUFFC.2025.3534429","url":null,"abstract":"Ultrafast plane-wave (PW) ultrasound imaging is a versatile tool that has become increasingly relevant for blood flow imaging using speckle tracking but suffers from a low signal-to-noise ratio (SNR). Cascaded dual-polarity wave (CDW) imaging can improve the SNR by transmitting pulse trains, which are subsequently decoded to recover the imaging resolution. However, the current decoding method (in the time domain) requires a set of two acquisitions, which introduces motion artifacts that result in incorrect speckle tracking at high flow velocities. Here, we evaluate an inverse filtering approach that uses frequency-domain decoding to decode acquisitions independently. Experiments using a disk phantom show that frequency-domain decoding of a four-pulse train achieves an SNR gain of up to 4.2 dB, versus 5.9 dB for conventional decoding. The benefit of frequency-domain decoding for flow quantification is assessed through experiments performed with a rotating disk phantom and a parabolic flow, and through matching linear simulations. Both CDW methods improve the tracking accuracy compared to single PW imaging. Time-domain decoding outperforms frequency-domain decoding in low SNR conditions and low velocities (<inline-formula> <tex-math>$leq 0.25$ </tex-math></inline-formula> m/s), as a result of the higher SNR gain. In contrast, frequency-domain decoding outperforms time-domain decoding for high peak velocities in imaging of the rotating disk (1 m/s) and of the parabolic flow (2 m/s), when significant scatterer motion between acquisitions causes imperfect time-domain decoding. Its ability to decode individual acquisitions makes the used frequency-domain decoding of CDW (F-CDW) a promising approach to improve the SNR and thereby the accuracy of flow quantification at high velocities.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"321-337"},"PeriodicalIF":3.0,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10856850","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control Publication Information

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-27 DOI: 10.1109/TUFFC.2025.3529339

引用次数: 0

Spatially Weighted Fidelity and Regularization Terms for Attenuation Imaging

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-27 DOI: 10.1109/TUFFC.2025.3534660

Sebastian Merino;Roberto Lavarello

{"title":"Spatially Weighted Fidelity and Regularization Terms for Attenuation Imaging","authors":"Sebastian Merino;Roberto Lavarello","doi":"10.1109/TUFFC.2025.3534660","DOIUrl":"10.1109/TUFFC.2025.3534660","url":null,"abstract":"Quantitative ultrasound (QUS) holds promise in enhancing diagnostic accuracy. For attenuation imaging, the regularized spectral log difference (RSLD) can generate accurate local attenuation maps. However, the performance of the method degrades when significant changes in backscatter amplitude occur. Variations in the technique were introduced involving a weighted approach to backscatter regularization, which, however, is not effective when changes in both attenuation and backscatter are present. This study introduces a novel approach that incorporates an L1-norm for backscatter regularization and spatially varying weights for both fidelity and regularization terms. The weights are calculated from an initial estimation of backscatter changes. Comparative analyses with simulated, phantom, and clinical data were performed. When changes in backscatter and attenuation occur, the proposed approach reduced the lowest root mean square error by up to 73%. It also improved the contrast-to-noise ratio (CNR) by a factor of 4.4 on average compared with previously available methods, considering the simulated and phantom data. In vivo results from healthy livers, thyroid nodules, and a breast tumor further confirm its effectiveness. In the liver, it is shown to be effective at reducing artifacts of attenuation images. In thyroid and breast tumors, the method demonstrated an enhanced CNR and better consistency of the attenuation measurements with the posterior acoustic enhancement. Overall, this approach offers promise for enhancing ultrasound attenuation imaging by helping differentiate tissue characteristics that may indicate pathology.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"338-350"},"PeriodicalIF":3.0,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Quantification of Blood Flow in the Carotid Bifurcation of Healthy Subjects

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-22 DOI: 10.1109/TUFFC.2025.3529285

Janna Ruisch;Joosje M. K. de Bakker;Majorie van Helvert;Erik Groot Jebbink;Suzanne Holewijn;Michel M. P. J. Reijnen;Chris L. de Korte;Anne E. C. M. Saris

{"title":"Quantification of Blood Flow in the Carotid Bifurcation of Healthy Subjects","authors":"Janna Ruisch;Joosje M. K. de Bakker;Majorie van Helvert;Erik Groot Jebbink;Suzanne Holewijn;Michel M. P. J. Reijnen;Chris L. de Korte;Anne E. C. M. Saris","doi":"10.1109/TUFFC.2025.3529285","DOIUrl":"10.1109/TUFFC.2025.3529285","url":null,"abstract":"Locally disturbed blood flow patterns are known to create an atherogenic environment, particularly in the presence of other cardiovascular risk factors. Given the geometry of a healthy carotid artery, complex flow patterns are expected to be present. This study aims to characterize (complex) blood flow patterns and estimate flow-derived parameters in the carotid bifurcation of healthy subjects. Ultrasound-based velocity vector imaging (US-VVI) was acquired in the carotid bifurcation of 20 healthy subjects. Hemodynamic parameters, including temporal velocity profile, vector complexity (VC), vortex presence, and wall shear stress (WSS), were derived and compared between two age groups (20–30 and 65–75 years). Lower velocities and higher VC values were observed in the older age group for all timepoints. The highest presence of vortices was observed during the systolic deceleration, which was more exposed in younger subjects (5 out of 10) compared to older subjects (3 out of 9). A quick build-up and consequent resolving of the vortices was reflected by the relatively short vortex duration, with a vortex presence of 11.4% (7.9–15.6) and 13.1% (5.9–18.6) as a percentage of the cardiac cycle in younger and older subjects, respectively. Larger WSS estimates, represented as median along the complete vessel wall, were found in the younger subjects at all timestamps, except at systolic deceleration. In conclusion, the presence of complex flow patterns was confirmed in healthy subjects and multiple flow-derived hemodynamic parameters were evaluated in two age groups, providing an insight into age-related differences in hemodynamics. Aging seemed to result in higher vector complexities, whereas the presence of recirculating flow is less in older subjects.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"309-320"},"PeriodicalIF":3.0,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10849671","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Selective sub-nucleus ultrasound stimulation induces synaptic potentiation in the mouse hippocampus.

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-20 DOI: 10.1109/TUFFC.2025.3531971

Wei Zhou, Pengqi Li, Wen Meng, Stephanie Hong Zheng, Shixiong Zhang, Shasha Yi, Minghui Gao, Zhengrong Lin

{"title":"Selective sub-nucleus ultrasound stimulation induces synaptic potentiation in the mouse hippocampus.","authors":"Wei Zhou, Pengqi Li, Wen Meng, Stephanie Hong Zheng, Shixiong Zhang, Shasha Yi, Minghui Gao, Zhengrong Lin","doi":"10.1109/TUFFC.2025.3531971","DOIUrl":"https://doi.org/10.1109/TUFFC.2025.3531971","url":null,"abstract":"<p><p>Ultrasound neuromodulation enables to elicit long-lasting effect on neural activities and behavioral responses across species, including humans. However, the potential biophysical mechanism of ultrasound stimulation to induce neuroplasticity still unclear. In this study, we developed a miniature, high target-specificity ultrasound neuro-stimulation chip to selectively stimulate sub-nucleus and investigate the synaptic plasticity induced by ultrasound stimulation in mouse hippocampal slices. The design of the narrow aperture planar interdigital transducers could reach 1.3 mm acoustic beam to precise stimulate the presynaptic CA3 neurons. Acoustic long-term potentiation (A-LTP) was induced by the ultrasound neuro-stimulation chip with 1 ms pulsed duration and different acoustic pressures at 100 Hz repetition frequency (100 Hz LIPUS) in the CA3 sub-region. Synaptic plasticity was measured by the slope of field excitatory postsynaptic potentials (fEPSPs), which were elicited using bipolar electrical stimulation electrodes in the Schaffer collaterals of CA3 region and recorded in postsynaptic CA1 neurons using extracellular electrodes. The LTP induced by ultrasound was compared to conventional 100 Hz tetanic electrical stimulation (100 Hz ES). Our results confirmed that ultrasound stimulation of CA3 significantly induces LTP-like synaptic plasticity when the applied acoustic pressure was 1.08 MPa. The success rate of A-LTP and the average weight of synaptic potentiation level were significantly increased with the increment of acoustic pressure. Moreover, A-LTP was mainly due to the mechanical effects of acoustic waves, but not the thermal or cavitation effects. These results demonstrated that the high-precision ultrasound neuro-stimulation chip can selectively modulate the neural activities in sub-nuclear brain region to induce synaptic potentiation, clarifying the biophysical mechanism of A-LTP.</p>","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"PP ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Temperature Dependence of the Sensitivity of Hydrophones for Biomedical Ultrasound Exposimetry

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-09 DOI: 10.1109/TUFFC.2025.3527625

Volker Wilkens;Martin Weber;Jennifer Twiefel

{"title":"Temperature Dependence of the Sensitivity of Hydrophones for Biomedical Ultrasound Exposimetry","authors":"Volker Wilkens;Martin Weber;Jennifer Twiefel","doi":"10.1109/TUFFC.2025.3527625","DOIUrl":"10.1109/TUFFC.2025.3527625","url":null,"abstract":"Though it has been recognized that the sensitivity of hydrophones depends on the temperature of the water they are used in, the amount of specific data that is available is very limited. This is possible because the measurements are technically challenging, laborious, and time-consuming. A broadband primary hydrophone calibration setup was extended to implement stable calibration conditions at different temperature settings. Four hydrophones of different types commonly used in ultrasound exposimetry were then characterized in the range from 17 °C to 29 °C, and average change rates of the sensitivity with temperature were determined for different ultrasonic frequencies. Two different membrane hydrophones showed an increase in sensitivity with increasing temperature in the range from 0.55% to 1.10% per 1 °C temperature rise within their bandwidths. The results for a capsule-type and a needle-type hydrophone were different in the sense that a decreasing sensitivity with increasing temperature was also observed. For the capsule-type hydrophone, a small increase was observed up to 15 MHz and a decrease for higher frequencies. The needle-type hydrophone provided a decrease at all frequencies, and the results were more noisy. Data, as determined in this study, can be applied to correct acoustic output measurements of medical ultrasonic equipment if the water temperature of the hydrophone application differs from that during calibration. Alternatively, it may suffice in some applications to consider a sensitivity change with temperature within the uncertainty estimation of the exposure measurement, in particular, if the temperature difference is limited to 1 °C or 2 °C.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"362-369"},"PeriodicalIF":3.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Variable Curvature Flexible Transducer for Abdominal Expandable Imaging

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-09 DOI: 10.1109/TUFFC.2025.3527543

Jianzhong Chen;Bing Zhuang;Jiaxing Peng;Zhe Zhang;Bo Wang;Chunsun Dai;Dawei Wu

{"title":"Variable Curvature Flexible Transducer for Abdominal Expandable Imaging","authors":"Jianzhong Chen;Bing Zhuang;Jiaxing Peng;Zhe Zhang;Bo Wang;Chunsun Dai;Dawei Wu","doi":"10.1109/TUFFC.2025.3527543","DOIUrl":"10.1109/TUFFC.2025.3527543","url":null,"abstract":"Expanding the imaging field of view (FOV) of medical ultrasound transducers will more effectively detect pathological behaviors of tissues or organs. Conventional rigid transducers can be realized by increasing the number of array elements or the curvature; however, the imaging aperture is fixed by the original size and shape during the manufacturing process. This article presented a 128-element, 3-MHz flexible curvature abdominal array (FCAA) with the goal of dynamically expanding the FOV within a 120° range. The piezoelectric stack was divided into small pitches through a double-cut process, and two-component viscoelastic substrates (TCVSs) were filled between adjacent array elements to generate tensile and compressive stresses during decomposition deformation. A 3-D-printed push-pull device provides sufficient mechanical support, resulting in a conformal minimum curvature radius of 46 mm. The innovative rigid-flexible composite backing layer was used to balance mechanical flexibility and high bandwidth (BW) of −6 dB to 67.6%. The results showed that the axial and lateral resolutions of the commercial phantom line target are 0.35 and 0.77 mm, respectively, and the axial and lateral resolutions of FOV 120° are 0.36 and 1.02 mm, respectively. The imaging performance of FCAA was verified by B-model imaging of the kidneys, intestines, uterus, and bladder of volunteers with a different body mass index (BMI). In addition, the 5-mm renal artery phantom verified the Doppler imaging function of FCAA. All the results demonstrated that FCPA has great potential clinical value in abdominal ultrasound and gynecological examination.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"299-308"},"PeriodicalIF":3.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control Publication Information IEEE超音波学、铁电学与频率控制论文集

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-08 DOI: 10.1109/TUFFC.2024.3520761

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Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO₂/LiNbO₃ Structure

IF 3 2区工程技术

IEEE transactions on ultrasonics, ferroelectrics, and frequency control Pub Date : 2025-01-08 DOI: 10.1109/TUFFC.2025.3526958

Temesgen Bailie Workie;Xiuwen Bi;Lingqin Zhang;Junyao Shen;Quhuan Shen;Jingfu Bao;Ken-ya Hashimoto

{"title":"Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO₂/LiNbO₃ Structure","authors":"Temesgen Bailie Workie;Xiuwen Bi;Lingqin Zhang;Junyao Shen;Quhuan Shen;Jingfu Bao;Ken-ya Hashimoto","doi":"10.1109/TUFFC.2025.3526958","DOIUrl":"10.1109/TUFFC.2025.3526958","url":null,"abstract":"This article proposes a double metal dots interdigital transducer (IDT) configuration for suppression of spurious responses in temperature-compensated surface acoustic wave (SAW) resonators employing the SiO2/LiNbO3 structure. The proposed IDT configuration includes primary metal dots at the edges of the IDT aperture region, and in addition, secondary metal dots placed near the busbars with the addition of short dummy electrodes. This double metal dots IDT configuration enables us to effectively suppress two kinds of spurious resonances: the transverse resonances that are common and the ones that are predominantly excited in the gap regions between IDT finger edges and busbars. The impact of geometric parameters on suppressing spurious responses is studied using periodic 3-D finite element simulations. Then, it is shown both theoretically and experimentally that the proposed mechanism can effectively suppress almost all spurious responses without affecting the critical performance metrics such as the quality factor and electromechanical coupling coefficient.","PeriodicalId":13322,"journal":{"name":"IEEE transactions on ultrasonics, ferroelectrics, and frequency control","volume":"72 3","pages":"390-396"},"PeriodicalIF":3.0,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143541883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0