metastases economically and effectively, also reducing the number ofmore expensive imaging procedures.

DIAGNOSTIC US

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Transient ultrasound radiation force elastography: Apreliminary comparison with surface palpation elastographyBamber JC, Lima DM, Duck FA, Shipley JA, Xu L, Institute ofCancer Research and Royal Marsden NHS Foundation Trust, UnitedKingdom of Great Britain and Northern Ireland; Bath Royal UnitedHospital, United Kingdom of Great Britain and Northern Ireland

Objectives: Ultrasound elasticity imaging is being developed for eval-uating the mechanical properties of soft tissues in vivo, but eachresearch group tends to specialize in a specific approach. Our objectivewas to assess the advantages and disadvantages of generating tissuestrain by deep loading with transient acoustic radiation force, versus theuse of nearly static surface loading.Methods: Experiments with gelatin phantoms and finite element mod-els were employed to measure the performance of pseudo-static free-hand elastography and radiation force elastography.Results: Relative to surface loading, radiation force images are lesssusceptible to artefacts associated with boundary conditions, elasticmodulus inhomogeneities and pre-existing tissue motion. Furthermore,they may possess a reduced rate of decay of strain signal-to-noise ratiowith depth, and demonstrate an improved contrast-transfer-efficiency,particularly for inclusions that have negative modulus contrast or thatare disconnected from the background by a low friction boundary. Ittakes longer to scan using radiation force loading and the elastogramsmay show contrast for ultrasonic attenuation and absorption, as well asfor tissue stiffness.Conclusions: Transient deep loading possess advantages over surfaceloading for elastography but both approaches may have a role to play,and further comparative evaluation in vivo is needed.

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Multidimensional reconstruction/imaging of shear modulusdistribution of living soft tissuesSumi C, Sophia University, Japan

Objectives: Previously, we reported a shear modulus reconstructionmethod utilizing the typical value of Poisson’s ratio. However, asreconstruction errors were confirmed due to the difference between theoriginal value and the set value, we proposed a method to reconstructPoisson’s ratio as well. Furthermore, we proposed to reconstruct den-sity as well to deal with dynamic deformation. However, due to thetissue incompressibility, the reconstruction of shear modulus, Poisson’sratio and density become unstable.Methods: In this report, to stabilize these reconstructions, we report anew reconstruction method using the mean normal stress as unknown.This method also allows stable reconstructions of shear modulus anddensity under the condition that Poisson’s ratio remains unknown. Theeffectiveness is verified through 2D phantom experiments and 3Dsimulations. [The cubic phantom (50 mm sides) includes a sphericalinclusion (radius, 5 mm) at the center (depth, 25.0 mm) having differentshear modulus and Poisson’s ratio from those of the surroundingmedium. Density is uniformly set. Noise-filled measurement data ofdisplacement vector were simulated by adding white noise to thecalculated raw displacement data.]Results: The new method yielded stable quantitative reconstructionsfor both the simulations and phantom experiments.

Conclusions: The method using the mean normal stress as unknown iseffective.

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On useful ultrasound image processing techniques for thediagnosis of fine blood vesselsIto M, Yamada A, Nakamura K, Kato K, Kobayashi A, Kuroshima N,Tokyo Denki University, Japan; Tokyo Univ. Agriculture and Tech.,Japan; Mitaka Kohki Co., Japan; Aloka Co., Japan; Micro DesignInc., Japan; Teikyo Univ., School of Medicine, Japan

Objectives: In order to extract the contours of vessels of various sizes,robust three-dimensional imaging techniques are essential to the result-ant successive scanned data. Our aim is to access to the vessels of about300 to 500 microns. We focus on the speckle reduction and edgeenhancement by adaptive morphological filters.Methods: The system with a high-frequency probe of 20 to 40 MHz,scan the region of 10�10�30 (mm in size). The accessed volume datahave 128 cross sections of 512�512 pixels of 256 gray levels. Ultra-sound longitudinal cross sectional images of blood vessels as well as3D contours can be reconstructed after a series of pre- and postpro-cessing.Results: We developed an adaptive three dimensional morphologicalfilter, which smooth and enhance a series of cross sectional images in3D space. It makes the imaging system independent of scanning con-ditions such as position and other factors.Conclusions: The system can be used for the diagnosis of fine vesselsin a lesion. The developed filters are designed to process ultrasoundimages adaptively and are, thus useful for detecting fine vessel in noisyultrasound images with low resolution. This research is supported byMEXT.HAITEKU (2002–2006) and Kanto Bureau of Economy, Tradeand Industry.

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Tissue harmonic imaging for musculoskeletal ultrasoundGauthier TP, van Holsbeeck MT, Philips Ultrasound, United Statesof America; Henry Ford Hospital, United States of America

Objectives: To assess the diagnostic performance of Tissue HarmonicImaging (THI) for musculoskeletal imaging.Methods: A numerical simulation was used to predict harmonicwaveform shape given ultrasound scanners signal path limitation. Itwas further used to design ideal THI waveforms for musculoskeletalimaging. Patients were then scanned with a compact linear trans-ducer featuring THI. Side-by-side comparisons between conven-tional imaging and THI were performed by scanning pathologiesusing either imaging modes. Dual display was used to monitor bothconventional and THI performance on same imaging planes.Results: When THI was used, image quality was significantly im-proved overall. Direct comparisons demonstrated lower overall clutterlevel with superior axial, contrast and lateral resolution leading to betterborder delineation of structures. THI was utilized for a more definitivediagnosis of cases such as meniscus tears, TFC abnormalities, rotatorcuff tears, needle visualization during procedures and bursal abnormal-ities.Conclusions: THI may be used to improve image quality and helpdiagnostic. Musculoskeletal ultrasound typically involves scanningsuperficial structures, which implies that acoustic waveforms won’tpropagate over long distances to allow for nonlinear propagation tooccur. This study therefore supports the need for carefully designedacoustic waveforms to make THI work to image the musculoskeletalsystem.

P142 Ultrasound in Medicine and Biology Volume 32, Number 5S, 2006