2012 Proceedings - International Tissue Elasticity Conference

036 3D RECONSTRUCTION OF IN VIVO ARFI AND SWEI IMAGES OF THE PROSTATE.
Stephen Rosenzweig 1 , Mark L Palmeri 1 , Thomas Polascik 2 , Kathryn R Nightingale 1 .
1 Duke University Biomedical Engineering, USA; 2 Duke University Medical Center, Durham, NC,
28
USA.
Background: Acoustic radiation force impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) of
the prostate have been reported to portray cancer and other pathologies as stiffer than the surrounding
tissue [1,2]. While these methods employ similar push excitations, they differ in resolution, contrast and
artifacts; SWEI images provide quantitative information, but generally afford poorer resolution and can
suffer from reflected wave artifacts [3], whereas ARFI images are typically higher resolution, but do not
reflect the true mechanical contrast of the tissue [4].
Aims: The aim of this work is to reconstruct matched ARFI and SWEI images, which are overlaid and
compared in order to overcome the challenges of each modality and provide additional information.
Methods: ARFI and SWEI data were collected concurrently, in vivo, under an IRB–approved protocol,
using a side–fire Acuson ER7B transducer, a Siemens Acuson SC2000 (Mountain View, CA) and a custom
transducer rotation stage. The data were then reconstructed in 3D taking advantage of spatial
continuity axially, laterally and in elevation as well as left and right propagating shear waves from each
push. The custom pulse sequence consisted of rapidly pushing at multiple foci and tracking the resulting
displacement on– and off–axis of the push using 16 parallel receive beams for each push location.
Results: To date, data from 7 patients with known prostate cancer have been obtained prior to radical
prostatectomy surgery in this ongoing study. Example matched ARFI and SWEI images are shown below
where a stiff region has been identified in the basal region of the patient’s right side (white circle) as
compared to the contralateral region (black circle). The ARFI image contrast is 0.64 and the SWEI image
contrast is 0.75; however, the edge resolution is much clearer in the ARFI image as seen at the location of
the arrows in the images, indicating the margin of the central gland. Structural information in these
modalities is significantly improved over B–mode ultrasound.
Conclusions: We have demonstrated the ability to concurrently acquire ARFI and SWEI data and
reconstruct the images utilizing the inherent three dimensional nature of the organ. The high contrast
SWEI images allow the user to more readily identify suspicious regions which can then be localized using
the ARFI image.
Acknowledgements: This work has been supported by NIH grants EB001040 and CA142824. We thank the
Ultrasound Division at Siemens Medical Solutions, USA, Inc. for their technical and in–kind support.
References:
[1] Zhai, L., et al.: Acoustic Radiation Force Impulse Imaging of Human Prostates: Initial In Vivo Demonstration.
Ultrasound Med Biol, 38(1), pp. 50–61, 2012.
[2] Barr, R.G., et al.: Shear Wave Ultrasound Elastography of the Prostate: Initial Results. Ultrasound Quarterly,
28(1), pp. 13–20, 10.1097, 2012.
[3] Deffieux, T., et al.: On the Effects of Reflected Waves in Transient Shear Wave Elastography. IEEE UFFC, 58(10),
pp. 2032–35, 2011.
[4] Nightingale, K., et al.: Analysis of Contrast in Images Generated with Transient Acoustic Radiation Force.
Ultrasound Med Biol, 32(1), pp. 61–72, 2006.
Figure 1: Matched coronal B–mode, ARFI, and SWEI images with the regions for contrast and resolution
computations indicated by the circles and arrows, respectively, on the ARFI and SWEI images.
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