American Institute of Ultrasound in Medicine <strong>Proceedings</strong> J Ultrasound Med 32(suppl):S1–S134, 2013of magnitude higher compared to unablated samples. However, reductionin stiffening was obtained in samples ablated at higher energy levels relativeto samples at lower energy levels (Table 1), which can be explainedby the strong tissue thermo-mechanical effects occurring at very high temperaturesthat essentially alter the structure of the tissue.Conclusions—The monotonic increase in tissue stiffness andviscosity under increasing HIFU ablation power has been shown to holdup only up to a certain point, beyond which the tissue stiffening starts todecay due to structural changes mainly due to rapid boiling. Such quantitativeunderstanding of tissue phenomenologic alterations during ablationis significant in the effective design and application of any HIFU-basedtherapeutic technique where a combination of tissue mechanical, thermal,and structural effects is expected.Table 1. Viscoelastic Properties of Canine Liver After AblationHIFU Energy, J0 360 750 900 1080Shear modulus, 4.4 ± 2.0 73.6 ± 19.0 85.7 ± 54.5 50.1 ± 38.7 53.9 ± 27.6kPaPhase shift, ° 8.4 ± 1.9 12.3 ± 0.8 12.3 ± 0.4 12.2 ± 0.4 12.1 ± 0.6Normalized shear 1 15.8 ± 6.9 18.5 ± 13.9 10.4 ± 9.5 11.3 ± 7.4modulus1540029 Therapeutic Ultrasound as Treatment for Chronic BacterialProstatitisMingde Li South China University of Technology, Richmond,British Columbia, CanadaObjectives—Antibiotic therapy for chronic bacterial prostatitisoften fails to eradicate pathogens due to poor antibiotic penetration intoprostatic secretions where the infection occurs, caused by the bloodprostatebarrier of the prostatic epithelium. It is our purpose to report antibiotictherapy enhanced by therapeutic ultrasound for a patient withchronic bacterial prostatitis with mixed pathogenic microorganisms ofStaphylococcus aureus, coagulase-negative Staphylococcus and Ureaplasmaurealyticum and with hardness of the prostate who was difficultto treat with methods in literature.Methods—After antibiotic medication, ultrasonic irradiationfrom the lower abdomen, perineum, and anus (not transrectally) on hisprostate followed immediately. The working ultrasonic intensity was 3W/cm 2 .Results—Without ultrasound, intravenous azithromycin andlevofloxacin hydrochloride therapies could not eradicate the pathogens,and his symptoms recurred and became more severe. Under continuousultrasonic irradiation at the intensity of 3 W/cm 2 , intravenous antibiotictherapies with azithromycin and imipenem eradicated S aureus and U urealyticum,but intravenous antibiotic therapies could not treat coagulasenegativeStaphylococcus; interventional antibiotic therapies with imipenemand urethral perfusion treated coagulase-negative Staphylococcus successfully.The National Institutes of Health Chronic Prostatitis SymptomIndex of the patient was reduced from 26 (pain, 16; urinary symptoms, 5;quality of life impact, 5) to 3 (pain, 0; urinary symptoms, 2; quality of lifeimpact, 1).Conclusions—The eradication of S aureus and U urealyticumindicates the continuous therapeutic ultrasound can open the bloodprostatebarrier. The blood-prostate barrier opening is explained by thehypothesis of ultrasonic emulsification of a secreted steroidogenic lipidin the basal layers of the prostatic epithelium caused by cavitations. Intravenousantibiotic therapies cannot treat coagulase-negative Staphylococcusdue to the formation of biofilms adherent to the epithelium of theductal system. The treatment for the patient was successful.1540196 Ultrasound-Assisted Chronic Wound Management:Clinical OutcomeJoshua Samuels, 1 * Michael Weingarten, 2 Leonid Zubkov, 1Youhan Sunny, 1 Christopher Bawiec, 1 David Margolis, 3 PeterLewin 1 1 Biomedical Engineering, Drexel University,Philadelphia, Pennsylvania USA; 2 Surgery, Drexel UniversityCollege of Medicine, Philadelphia, Pennsylvania USA; 3 Epidemiology,University of Pennsylvania Perelman School ofMedicine, Philadelphia, Pennsylvania USAObjectives—The purpose of this research was to examinewhether low-frequency (
American Institute of Ultrasound in Medicine <strong>Proceedings</strong> J Ultrasound Med 32(suppl):S1–S134, 2013deconvolution between the hydrophone output voltage and the hydrophonefrequency-dependent complex sensitivity. We have previouslyreported a method for measuring the magnitude and phase of hydrophonesensitivity using time delay spectrometry (TDS). The goal of this work isto assess the improvement in the accuracy of estimates of acoustic outputparameters (pulse intensity integral and peak rarefactional pressure) usingcomplex deconvolution.Methods—In the first set of experiments, a swept-frequencyTDS system was used to measure magnitude and phase responses of severaltypes of hydrophones used in medical ultrasound exposimetry. Theseincluded polyvinylidene difluoride spot-poled membrane, needle, and capsuledesigns. Measurements were performed using 4 broadband sourcetransducers to measure hydrophone sensitivity over the band from 1 to 30MHz. In the second set of experiments, 6 hydrophones were used to measurethe acoustic pressure waveform generated by a 3-MHz single-elementsource transducer. The voltage waveforms acquired in the second set of experimentswere deconvolved with sensitivities measured in the first set ofexperiments. The effect of deconvolution on measurements of the pulse intensityintegral and peak rarefactional pressure was measured.Results—The effect of deconvolution on measurements ofpulse the intensity integral and peak rarefactional pressure sometimes exceeded10%.Conclusions—The frequency dependence of hydrophone sensitivitycan have a substantial impact on measurements of the pulse intensityintegral and peak rarefactional pressure. In these cases, complexdeconvolution can be used to compensate for frequency-dependent hydrophonesensitivity.1538679 Pulmonary Hemorrhage Induced by Diagnostic UltrasoundRevealed by Growth of Comet Tail Artifacts in the ImageDouglas Miller Radiology, University of Michigan, AnnArbor, Michigan USAObjectives—Ultrasound examination of the lung has becomean important part of chest medicine, particularly for point-of-care diagnosisin emergency rooms and intensive care units. The objective of thisstudy was to explore the potential for lung injury, which may arise fromthe interaction of ultrasound pulses with alveolar gas, using a rat model ofpulmonary diagnostic ultrasound.Methods—Anesthetized rats were prepared by shaving theright thorax and then mounted in a 37°C water bath. A linear array (CL15-7, HDI 5000; Philips Healthcare, Andover MA) was used for B-mode imagingof the right lung at ≈7.6 MHz. A low mechanical index (MI) of 0.21was used to align the scan plane through an intercostal space. The MI thenwas raised for 5 minutes to higher settings in different groups of 5 rats. Fora sham group, the rats were prepared but not scanned. The real-time imagewas recorded and evaluated for occurrence of comet tail artifacts (CTAs),which are indicative of alveolar fluid. The lungs were evaluated for the sizeof any pulmonary hemorrhages (PHs).Results—For the highest available MI (0.9), the image immediatelydisplayed growing CTAs, which rapidly spread across the entirebright-line image of the lung surface. The CTAs appeared within secondsat MI = 0.7 or 0.9 but more slowly at lower MIs. Contusion-like PHs werefound on the lungs, which appeared to have a one-to-one correspondencewith the CTAs in the image. The proportion of positive results was statisticallysignificant for MI = 0.52 (4 of 5 rats; P < .01) but not for MI = 0.37(2 of 5, P > .1), relative to no PH in shams.Conclusions—PH was induced in a rat model of pulmonary diagnosticultrasound at moderate MIs, and this bioeffect was indicated by thegrowth of CTAs in the image. The induction of PHs by pulsed ultrasoundwas discovered over 20 years ago but appeared to pose little risk to patients,because only incidental scanning of the lung was expected. However,direct scanning, which occurs for pulmonary applications, may carry a riskof pulmonary injury for some patients. More information will be needed toprovide safety guidance consistent with optimal diagnostic imaging.1528109 Evaluation of Definity Stability Over Time Using DoublePassive Cavitation DetectionMarianne Gauthier, 1,2 * Daniel King, 1,3 William O’Brien Jr 1,21Bioacoustics Research Laboratory, 2 Electrical and ComputerEngineering, 3 Mechanical Science and Engineering, Universityof Illinois at Urbana-Champaign, Urbana, Illinois USAObjectives—Definity is the first ultrasound contrast agent(UCA) approved by the US Food and Drug Administration that offersflexible dosing and administration through intravenous bolus injection orcontinuous intravenous infusion. In a clinical context (for diagnosis, therapy,and bioeffect studies), temporal stability of the UCA can be criticalusing either infusion or bolus: infusion implies stability of the microbubblesduring the time of the injection, while bolus may be repeated to acquireseveral images for the same patient, implying the microbubbles toexhibit the same properties over time.Methods—This study’s aim was to assess the stability of Definityover time. Experiments were performed using the double passive cavitationdetection (DPCD) method, allowing the evaluation of the collapsethresholds of an isolated microbubble based on the detection of postexcitationsignals occurring 1 to 5 microseconds after the principle excitationof the bubble. Five sets of DPCD experiments (3-cycle tone bursts at thecentral frequency of 2.8 MHz) were performed over 3 weeks. For eachset of experiments, 5% and 50% collapse thresholds were determined withtheir 95% confidence interval (CI) based on the generalized linear modelregression performed using MatLab. We also compared the size distributionof each tested microbubble set.Results—Statistical analysis exhibited no significant differencesin the bubble size distributions and the 5% and 50% collapse thresholdsmeasured using the DPCD method (Table 1).Conclusions—Definity microbubbles have been found to bestable over the 3 weeks of experiments from the size distribution and the5% and 50% collapse thresholds points of view. Definity can be used withoutextra precaution concerning its temporal stability. (Supported by NationalInstitutes of Health grant R37EB002641.)Table 1. Bubble Diameter, 5% and 50% Postexcitation Thresholds ± 95% CIsEvaluated Over 3 Weeks5% Postexcitation 50% PostexcitationBubble Diameter Threshold ± 95% CI, Threshold ± 95% CI,Group ± 95% CI, μm MPa MPa1 1.40 (1.28–1.52) 0.022 (0.001–0.191) 0.173 (0.001–0.559)2 1.23 (1.12–1.34) 0.05 (0.001–0.277) 0.455 (0.005–0.944)3 1.39 (1.26–1.52) 0.077 (0.003–0.226) 0.38 (0.075–0.671)4 1.26 (1.13–1.39) 0.116 (0.015–0.269) 0.464 (0.162–0.72)5 1.42 (1.31–1.53) 0.058 (0.001–0.235) 0.315 (0.01–0.663)1541018 Arrival Time Estimation in a Sparsely Sampled HemisphericTransducer ArrayJason Tillett, 1 * Jeffrey Astheimer, 1 Robert Waag 1,2 1 Electricaland Computer Engineering, 2 Imaging Sciences, University ofRochester, Rochester, New York USAObjectives—Estimate waveform arrival time fluctuationscaused by propagation through a breast model in a sparsely sampledfaceted approximation of a hemispheric transducer array.Methods—A 3D pseudospectral k-space method was used tocalculate acoustic propagation from a point source located near the centerof an array of widely separated transducers. The point source, with a centerfrequency of 5 MHz and –6-dB bandwidth of 2.5 MHz, was situatednear the chest wall of a numeric anthropomorphic breast model, and thetransducer array surrounded the pendant boundary of the breast. The hemispherewas approximated using 40 triangular facets. The separation of elementsaveraged about 1.5 times the wavelength at 5 MHz, ie, about 3S42
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