Vibro-acoustography and B-mode integration for 3D imaging Hermes A. S. Kamimura, Marden A. Fagundes, Mostafa Fatemi, Senior Member, IEEE and Antonio A. O. Carneiro Abstract— Tridimensional representation of vibro- acoustography images based on the topology acquired by B-mode acquisitions is proposed for the evaluation of bone and implant surfaces. A tridimensional evaluation of the implant coverage used in a total hip arthroplasty procedure was performed to show the feasibility of this approach. A vibro-acoustography image of the uncovered area of the implant was acquired and represented in planar representation. However, tridimensional representation of the exposed surface area is necessary for proper evaluation of the stability of the implant. Hence, the topologies of the implant and the bone region around it were determined by acquiring 280 B-mode images. The B-scan images were processed in order to reconstruct the tridimensional surface of the objects. Finally, the vibro-acoustography image and the B-mode-based surface were aligned for the tridimensional visualization. The B-mode tridimensional representation of the bone and implant was improved by the enhancement of contrast and resolution provided by the vibro-acoustography image. The final tridimensional image presented a resolution of 0.25 mm. The topological correction based on B-mode slices allowed an accurate evaluation of the surface area. I. INTRODUCTION Current X-ray-based methods are not feasible for postoper- ative monitoring in some cases of therapeutic procedures due to the impossibility of wide visualization of the region, side effects in patients or image artifacts. Total hip arthroplasty (THA) is a cost-effective procedure to treat patients with end stage osteoarthritis in which implants replace the head of the femur and the acetabular in the pelvis [1]. Plain AP (anterior/posterior) pelvis radiographs are used in this case for measuring the cup coverage postoperatively [2] [3]. How- ever, to provide precise information relating the minimum cup coverage and cup loosening rate, a noninvasive three- dimensional imaging technique is required, since plain AP radiograph does not allow clear visualization of the both anterior and posterior regions [4] (Fig. 1). Since, X-ray radiograph is avoided in cases involving children [5], B-mode ultrasound images allow an estimation of the investigated regions. Other modalities such as computer tomography and magnetic resonance imaging introduce artifacts due to the material used in the implants (metal and ceramic), which This work was supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) from Brazil. Hermes A. S. Kamimura Marden A. Fagundes, and Antonio Adilton O. Carneiro are with the Departamento de Fisica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, SP, Brazil. (adilton@ffclrp.usp.br) Mostafa Fatemi is with the Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine, Rochester, MN, 55904, USA can be a problem for a correct evaluation of the uncovered area. Ultrasound wave (UW) propagation is subjected to energy loss by absorption, where its energy is converted into other energy forms such as heat, chemical energy, or light [6]. Changes in the compressibility and density of the medium can cause scattering (mainly reflection and refraction) of the wave. Objects inside the human body with high densities, such as bones and metal implants used in orthopedic proce- dures, present high impedance causing high reflection of the UW. For high-density objects, UW propagation is severely attenuated. Ultrasound parameters (frequency, intensity, con- trast, etc) can be set to mainly display information about the surface of high-density objects. Therefore, high-density helps the visualization of the surface in ultrasound modalities in comparison to X-ray-based modalities where the high- density can include artifacts or blind regions anterior or posterior to the object. Vibro-acoustography (VA) is an ultrasound-based tech- nique in which two cofocused ultrasound beams of slightly different frequency (MHz) generate a low frequency (kHz) acoustic excitation due to their interference [7] [8]. A dedicated hydrophone detects the sound emitted by the target when excited by this low frequency radiation force. The focused low-frequency excitation provides a speckle- free image with a high lateral resolution image (sub-mm). Calle [9] presented VA images with high resolution of the trabecular structure of a calcaneus bone. An implementation of VA on a clinical imaging system [10] using linear and phased arrays is being developed in Mayo Clinic which Fig. 1. Plain AP (anterior/posterior) radiography of the total hip arthro- plasty model. The uncovered area is not clear in the anterior and posterior region. The implant coverage is evaluated by defining the lateral border of the uncovered region. 978-1-4244-4122-8/11/$26.00 ©2011 IEEE 421 33rd Annual International Conference of the IEEE EMBS Boston, Massachusetts USA, August 30 - September 3, 2011