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High-transmission frequency sonography of superficial tendons:A comparative study between matrix and linear transducerperformances using a commercial phantomClaudon M, Guerin A-L, Thammavong S, Winninger D, Mainard L,Galloy M-A, Mandry D, Department of Radiology, Children’sHospital, CHU Nancy Brabois, France; Hospital St-Julien, CHUNancy, France

Objectives: The study was to compare imaging performances obtainedwith a matrix and a linear high-frequency transmission transducers inthe evaluation of tendons, using a commercial phantom as well as toevaluate potential benefits of harmonic imaging and spatial compoundmode.Methods: Using a high-end US system (Aplio, Toshiba), a compara-tive study between a linear (5–12 MHz) (LT) and a matrix transducer(7–14 MHz) (MT) was performed in an experimental study based onthe RMI 403 GS (Gammex, WI). Phantom gel was figuring soft tissues,and nylon filaments superficial tendons.Results: For LT and MT, maximum penetration depth was, respec-tively, 100 mm and 55 mm; best axial resolution was 0.2 mm and0.1 mm, and highest lateral resolution 0.4 mm and 0.3 mm, respec-tively; lowest slice thickness was 0.6 mm and 0.9 mm at 10.7 mmdepth. Anisotropy effect appeared for a beam angle of 8° for bothtransducers. Harmonic mode slightly decreased depth penetration,significantly improved axial resolution and reduced slice thicknessfor LT only (p � 0.5). Spatial compound only improved lateralresolution for LT.Conclusions: Using a test object, both LT and MT have a high level ofperformance valuable for imaging superficial tendons, with a betterspatial resolution obtained with MT.

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Development of ultrasound imaging and diagnostic system forfine blood vessel structureIto M, Yamada A, Nakamura K, Kato K, Kobayashi A, Kuroshima N,Tokyo Denki University, Japan; Tokyo University of Agriculture andTechnology, Japan; Mitaka Kohki Co., Japan; Aloka Co., Ltd.,Japan; Micro Design Inc., Japan; Teikyo University, School ofMedicine, Japan

Objectives: To diagnose fine vessels before surgery, their locationsmust be identified in the lesions with their surrounding tissues in a threedimensional way. We developed an ultrasound imaging system todisplay vessels primarily for micro-surgery.Methods: The system consists of a console unit, an ultrasound scannerwith a high-frequency probe, and a mechanically flexible holder tosupport the scanner at a desired position. The frequencies are 20–40MHz. The console unit controls the scanner and the ultrasound probe toscan the region of 10 � 10 � 30 (mm in size) and provides differentcross sectional views. The accessed volume data have 128 cross sec-tions of 512 � 512 pixels of 256 gray levels. Ultrasound longitudinalcross sectional images of blood vessels as well as their 3D contours arereconstructed after a series of image processing.Results: Reconstructed longitudinal images, vertical and horizontalones, display the scanned vessels in the lesion. We confirmed that abranched fine vessel is observed clearly.Conclusions: The system can be used for the diagnosis of fine vesselsin a lesion near skin and is useful for micro-surgery. This research issupported by MEXT.HAITEKU (2002–2006) and the Regional Indus-try Revitalization Project, Kanto Bureau of Economy, Trade, andIndustry.

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System identification approach to contrast imaging with singlepulse emissionFox P, Tranquart F, Institute of Sound and Vibration Research(ISVR), University of Southampton, United Kingdom of Great Britainand Northern Ireland; Hospital Bretonneau CHRU Tours, France

Objectives: Contrast imaging methods such as pulse inversionexploit the difference in scattering responses between linear tissueand nonlinear contrast agents. Such methods emit two or morepulses separated either temporally or spatially, at the cost of eitherreduced frame rate or reduced spatial resolution as compared to thetheoretical values possible from a single pulse emission. This articleproposes a method for imaging contrast agents specifically usingsingle pulse emission only.Methods: A system identification approach is taken, first fitting aleast squares linear transfer function model between emitted andreceived pulses, and then obtaining a set of predicted received pulsevalues based on the emitted pulse and the linear least squares model.Results: In the case of the reflector being linear (tissue), the linear leastsquares model accurately predicts the received pulse and the pulseprediction error is insignificant. In the case of a nonlinear reflector(contrast agent), the linear model cannot accurately predict the receivedpulse and the pulse prediction error is significant.Conclusions: These results are parallel to the insignificant andsignificant residual pulses obtained respectively in pulse inversion,but the method here requires only a single emission to obtain thediscrimination. Results for typical contrast agent responses aregiven.

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Beam steering at low frequencies for noninvasive brain diseasetherapy with a hemispherical ultrasound transducerYang F-Y, Liu H-L, Chen Y-Y, Lin W-L, Institute of BiomedicalEngineering, National Taiwan University, Taiwan; Department ofElectrical Engineering, Chang Gung University, Taiwan;Department of Electrical Engineering, National Taiwan University,Taiwan

Objectives: To examine the steering and focusing ability of a station-ary hemispherical ultrasound transducer for trans-skull brain diseasetherapy without skull-specific aberration correction.Methods: This work employs a simulation program to investigate theeffect of ultrasound transducer parameters on the steering and focusingability for trans-skull therapy. The ultrasound pressure distribution andthe grating lobes in tissue are used to determine the steering andfocusing ability for a set of given conditions. The factors studied are theultrasound frequency and the size of the transducer.Results: Simulation results demonstrate that a hemispherical phasedarray with low frequencies can steer a high-pressure focal zone inthe brain tissue without performing a craniectomy. The peak and thesize of the high-pressure focal zone mainly depend on the fre-quency, and the shifting distance of the focal zone. By comparingthe peak pressures between the focal zone and the grating lobe, 0.1MHz transducer performs the desired results for wide ranges ofbeam steering.Conclusions: The results reveal the feasibility of using a hemisphericaltransducer with beam steering method at low frequency for braindisease therapy within a wide range of the brain without performing acraniectomy.

P278 Ultrasound in Medicine and Biology Volume 32, Number 5S, 2006